initiation of the australian summer monsoon 14 000 years ago abstract definitive evidence for the onset of monsoon moisture in northern australia following the arid phase of the last glacial maximum has been elusive in large part due to the lack of long continuous sediment records here we report new evidence from two separate drainage basins in the kimberley region of monsoonal northwestern australia at both sites radiocarbon ages on basal biogenic materials in flood deposits indicate stream flow as high or higher than maximum historic levels began about 14 cal ka bp these results suggest that the australian summer monsoon was fully active several millennia earlier than previously expected the early onset of the monsoon and the widespread evidence for diminished monsoon activity in the late holocene cannot be reconciled with primary forcing of the australian monsoon by changes in low latitude summer insolation over australia

lake kumphawapi revisited the complex climatic and environmental record of a tropical wetland in ne thailand kumphawapi which is thailand s largest natural freshwater lake contains a 10 000 year long climatic and environmental archive new data sets stratigraphy chronology hydrogen isotopes plant macrofossil and charcoal records for two sedimentary sequences are here combined with earlier multi proxy studies to provide a comprehensive reconstruction of past climatic and environmental changes for northeast thailand gradually higher moisture availability due to a strengthening of the summer monsoon led to the formation of a large shallow lake in the kumphawapi basin between 10 700 and c 7000 cal bp the marked increase in moisture availability and lower evaporation between c 7000 and 6400 cal bp favoured the growth and expansion of vegetation in and around the shallow lake the increase in biomass led to gradual overgrowing and infilling to an apparent lake level lowering and to the development of a wetland multiple hiatuses are apparent in all investigated sequences between c 6500 and 1400 cal b

oscillations in the southern extent of the indo pacific warm pool during the mid holocene the indo pacific warm pool ipwp is thought to play a key role in the propagation and amplification of climate changes through its influence on the global distribution of heat and water vapour however little is known about past changes in the size and position of the ipwp in this study we use a total of 48 modern and fossil coral records from the mentawai islands sumatra indonesia and muschu koil islands papua new guinea to reconstruct oscillations in the extent of the ipwp since the mid holocene we show that reliable estimates of mean sea surface temperature sst can be obtained from fossil corals by using low resolution sr ca analysis of a suite of corals to overcome the large uncertainties associated with mean sr ca sst estimates from individual coral colonies the coral records indicate that the southeastern and southwestern margins of the ipwp were cooler than at present between similar to 5500 and 4300 years bp similar to 1 2 degrees c 0 3 degrees c and were similarly cool before similar to 6800 years bp this mid holocene cooling was punctuated by an abrupt short lived shift to mean ssts that were warmer than at present between similar to 6600 and 6300 years bp similar to 1 3 degrees c 0 3 degrees c while similarly warm conditions may have also existed after similar to 4300 years bp we suggest that mid holocene cooling at our study sites was related to contractions of the southeastern and southwestern margins of the ipwp associated with the more northerly position of the inter tropical convergence zone itcz that accompanied mid holocene strengthening of the asian summer monsoon conversely intervals of abrupt warming appear to correspond with widespread episodes of monsoon weakening and accompanying southward migrations of the itcz that caused the ipwp to expand beyond our coral sites intervals of a strengthened asian monsoon and cooling in the southwestern ipwp during the mid holocene appear to correspond with a more positive indian ocean dipole iod like mean configuration across the tropical indian ocean suggesting that the asian monsoon iod interaction that exists at interannual time scales also persists over centennial to millennial scales associated mean changes in the pacific enso modes may have also occurred during the mid holocene the dynamic and inter connected behaviour of the ipwp with tropical climate systems during the mid holocene highlights the fundamental importance of the warm pool region for understanding climate change throughout the tropics and beyond c 2009 elsevier ltd all rights reserved

trace elements in speleothems as recorders of environmental change speleothems are now established as important palaeoenvironmental archives and contain a number of suitable proxies although trace elements have been much less widely used than oxygen and carbon isotopes the complexity of the cave environment helps to explain this since the fluids from which speleothems form vary greatly in composition in space even within a cave chamber seasonally and over longer periods understanding the forcing factors for this variability is the key to decoding the significance of the trace element records a variety of techniques are available for trace element work and it is important to understand the strengths and limitations of each and also to seek an understanding e g by micro imaging techniques of whether the elements are associated with inclusions in the caco3 or are isolated within the crystal lattice for some elements there is a more or less predictable relationship between element ratios to ca in the water and in the calcite individual trace elements may be derived from atmospheric deposition superficial deposits or bedrock and can be recycled in soil processes before being transferred to the cave some components show an instantaneous response to water infiltration whereas others are only leached by slow flowing seepage waters changing in the proportion of water from fracture fed and seepage flow aquifer compartments is an important factor in influencing trace element supply high flows lead to higher fluxes of soil derived colloidally transported elements conversely under relatively dry conditions degassing of co2 results in prior calcite precipitation upflow of the site of speleothem deposition and leads to higher ratios of sr ca and mg ca some trace element variations in speleothems over time are induced during crystal growth whereby faster growth leads to a greater departure from equilibrium element partitioning despite the demonstrated temperature dependence of mg partitioning into calcite attempts at deriving palaeotemperature records from speleothems have been so far confounded by variations in solution mg ca and or crystallographic effects a number of case studies have effectively used trace elements such as speleothem mg as records of palaeo aridity using supporting arguments from modern monitoring or covariations with other parameters such as stable isotopes sr and u isotopes can also be indicators of palaeohydrology although sr isotope variations can also reflect varying aeolian input considerable progress has been made in decoding the meaning of annual trace element variations using criteria for understanding dripwater hydrology and ph this should lead in the future to more specific interpretations of how seasonality evolves through time

an aquaplanet monsoon abstract a hypothesis is proposed that the seasonal evolution of sea surface temperature sst is the major forcing to control both the onset and the life cycle of the monsoon a sensitive coupling of surface heat flux and cumulus convection is the central process and in the current model is realized by wind induced surface heat exchange the model adopted is a shallow water analog in dynamics with two vertical levels for thermodynamics the land forcing effect is neglected as a crucial simplification of the model experiments along with the absence of the dynamical feedback to the sst in the model experiments with steady sst forcing reveal the presence of three regimes of response weak sst forcing realizes two unsteady regimes depending on the latitude of the forcing i the supercluster regime characterized by equatorially trapped eastward propagating convective coherencies akin to the madden julian waves and ii the monsoon regime characterized by an intermittent planetary scale standing conv

a discontinuous climatic record from 187 to 74 ka from a speleothem of the clamouse cave south of france this study presents a continental paleoclimatic record in the south of france based on n 18 o n 13 c and the 234 u 238 u activity ratio dated by the 230 th 234 u disequilibrium method with thermal ionization mass spectrometry a stalagmite cla4 from the clamouse cave offers a discontinuous stable isotopic record between 189 ka and 74 ka which covers marine isotope stages mis 7 6 4 5 5 5 3 and 5 1 the growth phases of the cla4 stalagmite correspond to high sea level stages except during mis 6 4 169 162 ka all the growth phases of cla4 correspond to humid periods corresponding to the sapropel events observed in the eastern mediterranean basin thus the influence of a strong hydrological activity in the eastern mediterranean basin during these periods prevailed as far west as the south of france because the karstic system studied strongly buffers the isotopic composition of water isotopic variations of the calcite deposited in the cave represent mainly global and large scale environmental variations when isotopic equilibrium conditions prevailed for calcite crystallization sub stage 5 3 the end of 5 5 and mis 7 were colder by about 4 6 c calculated temperature compared to present day temperature while the growth phases of substages 5 1 and the beginning of 5 5 reflect environmental conditions close to present ones the n 18 o and n 13 c values of cave deposits of the sub stage 6 4 are 1 strongly marked by kinetic fractionation processes such as evaporation due to moisture deficit within the cave atmosphere during the first step of this growth phase and 2 related to higher humidity due to a second period of enhanced rainfall during the second step of growth this study shows that even if calcite has not been deposited at isotopic equilibrium its isotopic composition can give insights into the environmental conditions at the time of deposition 2002 elsevier science b v all rights reserved

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

holocene tropical western indian ocean sea surface temperatures in covariation with climatic changes in the indonesian region the sea surface temperature sst of the tropical indian ocean is a major component of global climate teleconnections while the holocene sst history is documented for regions affected by the indian and arabian monsoons data from the near equatorial western indian ocean are sparse reconstructing past zonal and meridional sst gradients requires additional information on past temperatures from the western boundary current region we present a unique record of holocene sst and thermocline depth variations in the tropical western indian ocean as documented in foraminiferal mg ca ratios and 18o from a sediment core off northern tanzania for mg ca and thermocline 18o most variance is concentrated in the centennial to bicentennial periodicity band on the millennial time scale an early to mid holocene 7 8 5 6 ka warm phase is followed by a temperature drop by up to 2 c leading to a mid holocene cool interval 5 6 4 2 ka the shift is accompanied by an initial reduction in the difference between surface and thermocline foraminiferal 18o consistent with the thickening of the mixed layer and suggestions of a strengthened walker circulation however we cannot confirm the expected enhanced zonal sst gradient as the cooling of similar magnitude had previously been found in ssts from the upwelling region off sumatra and in flores air temperatures the sst pattern probably reflects the tropical indian ocean expression of a large scale climate anomaly rather than a positive indian ocean dipole like mean state

partitioning of strontium between calcite and fluid the sr ca ratio of biogenic carbonate is widely used as a proxy for paleotemperature this application is supported by empirical calibrations of sr ca as a function of temperature but it is also known that sr uptake in calcite gauged by kdsr is affected by other variables including bulk precipitation rate kdsr increases with increasing precipitation rate there are no data from controlled experiments specifically addressing the effect of radial growth rate of individual crystals on kdsr for this reason we conducted two series of experiments to explore sr partitioning at varying growth rates 1 growth from a cacl2 nh4cl srcl2 solution by diffusion of co2 from an ammonium carbonate source drift experiments and 2 drip precipitation of calcite on a substrate using a steady flow of cacl2 srcl2 and na2co3 solutions mixed just before passage through a tube and dripped onto a glass slide precoated with calcite cave type experiments the growth rates of individual crystals were determined by periodic monitoring of crystal size through time or roughly by comparison of the final size with the duration of the experiment electron microprobe analyses across sectioned crystals grown in the drift experiments show that the concentration of sr is high in the center where radial growth rates are highest and decreases systematically toward the edge the center to edge drop in sr concentration is a consequence of the slowing radial growth rate as individual crystals become larger in general high crystal growth rate v enhances sr uptake in calcite due to a type of kinetic disequilibrium we refer to as growth entrapment the apparent kdsr ranges from 0 12 to 0 35 as v increases from 0 01 nm s to 1 m s at 25 c

new early triassic bryozoa trepostomata from spitsbergen with some remarks on the stratigraphy of the investigated horizons new trepostomatous bryozoan species paralioclema winsnesi sp nov paralioclema mariaholmensis sp nov and paralioclema sp cf mariaholmensis are described from the lower triassic succession of spitsbergen the investigated bryozoan faunas are associated with coarse sandstones calcareous siltstones and shelly limestones the bryozoan colonies are mostly well preserved in situ and show limited evidence of transportation some zoarial fragments show bioerosion the conodont species neogondolella elongata ellisonia triassica neospathodus dieneri and neospathodus svalbardensis extracted from the investigated horizons are dienerian smithian in age

soil and karst aquifer hydrological controls on the geochemical evolution of speleothem forming drip waters crag cave southwest ireland abstract in recent years there has been increased interest in cave speleothems as archives of palaeoclimate monitoring of rainfall and soil and karst water chemistries was performed at crag cave castleisland co kerry southwest ireland in august 1997 and january 1998 in order to understand temporal and spatial variations in karst water hydrology and chemistry and their implications for interpreting the potential palaeohydrological signal preserved by speleothems at this site temporal variations in karst water drip rates and geochemistry allow drips to be classified by hydrological response to rainfall and the associated processes of dilution piston flow source change and prior calcite precipitation during aquifer throughflow evolution from soil matrix and preferential flow solutions has also been determined to exert an important control on karst water chemistries as a result of these findings we present hydrogeochemical models and plumbing diagrams that delineate the controls on karst water evolution at a number of sampling locations within the cave at this site we propose that a palaeohydrological signal may be recorded by crag cave speleothems that may be interpreted via the study of mg ca ratios in speleothems linked to monitoring of modern drip water chemistry

comparison of high resolution sub annual records of trace elements in a modern 1911 1992 speleothem with instrumental climate data from southwest australia high spatial resolution measurements of mg p u sr ba and na using 193 nm excimer laser ablation inductively coupled plasma mass spectrometry has revealed clearly resolvable annual cycles in a modern speleothem from southwestern australia the age of this stalagmite is established by the dates of emplacement and removal of the boardwalk where it grew 1911 1992 this chronological constraint allows for the first confident comparison between the instrumental climate record and speleothem trace element content eleven laser ablation transects across a 0 5 mm wide section of the speleothem growth axis were measured cycles that could be matched between adjacent transects were stacked into a master record to minimise variability between tracks and permit greater confidence in comparing the trace elements to the instrumental climate record p and u positively and mg inversely mimic the sudden 20 decrease in annual rainfall experienced by this region since 1965 we argue that p from seasonal vegetation decay is transported to the speleothem before it is mineralised in the soil owing to the low p retention capacity of southwest australian soils both vegetation activity and the transport of vegetation derived hpo42 are sensitive to rainfall groundwater p concentration may also influence the transport of u through the strong affinity between phosphate and uranyl ions mg appears to be sensitive to groundwater residence time as this affects drip water mg ca composition by preferential loss of ca during drier episodes when calcite precipitates before reaching the stalagmite the effects of groundwater residence time may also be important for sr on inter annual scales however the behaviour of sr on the annual cycle is opposite to mg but compatible with ba and na which are shown to depend on speleothem growth rate

mg sr and sr isotope geochemistry of a belgian holocene speleothem implications for paleoclimate reconstructions in this study variations in mg ca sr ca and 87sr 86sr ratios in a holocene belgian speleothem cave secondary carbonate deposit are interpreted in terms of changes in water residence time and changes in weathering processes possibly induced by changes in west european climate a stalagmite from the pere noel cave belgium was dated with the tims u th method and was deposited between 13 and 2 ka bp the 1000 mg ca ratio varies between 4 9 and 26 and displays short term changes but no significant long term trend the 1000 sr ca ratio varies between 0 09 and 0 31 and displays both short term changes and a long term decreasing trend from 12 9 to 3 5 ka in parallel the sr isotopic composition of the speleothem decreases from 0 7090 at 12 9 ka to 0 7088 at 3 5 ka the sr isotope ratio is higher than expected from the overlying limestone 87sr 86sr 0 7081 which implies an external source of radiogenic sr most probably from a silicate phase short term and long term changes in mg ca sr ca as well as long term changes of 87sr 86sr ratios can be explained by changes in the dissolution and precipitation processes of the host limestone these processes are controlled by changes in water residence times linked to changes in the water excess precipitation minus evapo transpiration c 2000 elsevier science b v all rights reserved

the coupled δ13c radiocarbon systematics of three late glacial early holocene speleothems insights into soil and cave processes at climatic transitions abstract the coupled 13 c radiocarbon systematics of three european stalagmites deposited during the late glacial and early holocene were investigated to understand better how the carbon isotope systematics of speleothems respond to climate transitions the emphasis is on understanding how speleothems may record climate driven changes in the proportions of biogenic soil carbon and limestone bedrock derived carbon at two of the three sites the combined 13 c and 14 c data argue against greater inputs of limestone carbon as the sole cause of the observed shift to higher 13 c during the cold younger dryas in these stalagmites gar 01 from la garma cave n spain and so 1 from sofular cave turkey the combined changes in 13 c and initial 14 c activities suggest enhanced decomposition of old stored more recalcitrant soil carbon at the onset of the warmer early holocene alternative explanations involving gradual temporal changes between open and closed system behaviour during the late glacial are difficult to reconcile with observed changes in speleothem 13 c and the growth rates in contrast a stalagmite from pindal cave n spain indicates an abrupt change in carbon inputs linked to local hydrological and disequilibrium isotope fractionation effects rather than climate change for the first time it is shown that while the initial 14 c activities of all three stalagmites broadly follow the contemporaneous atmospheric 14 c trends the younger dryas atmospheric 14 c anomaly can be clearly discerned subtle changes in speleothem initial 14 c activities are linked to climate driven changes in soil carbon turnover at a climate transition

preliminary u series and thermoluminescence dating of excavated deposits in liang bua sub chamber flores indonesia we report the results of a test excavation of deposits in a limestone cave sub chamber located beneath the main chamber of liang bua flores indonesia the discovery site of the small hominin species homo floresiensis well preserved remains of extinct pleistocene fauna and stone artefacts have previously been identified on the surface of a sediment cone within the sub chamber our excavation of the deposits at the base of the sediment cone in the sub chamber to 130 cm depth yielded only a few fragmentary bones of extant fauna uranium thorium u series or u th dating of soda straw stalactites excavated from 20 to 130 cm in depth demonstrates that the excavated sediments were deposited during the holocene red thermoluminescence tl dating of the sediments at the base of the excavation 130 cm depth indicates these sediments were last exposed to sunlight at 84 15 ka thousand years similar to red tl ages of cave sediments from the main chamber together these results indicate that the surface faunal remains which are morphologically analogous to pleistocene finds from the main chamber excavations were transported to the sub chamber relatively recently from the main chamber of liang bua and probably originated from conglomerate deposits at the rear of the cave and from deposits around the front entrance there is no evidence for hominin occupation of the sub chamber instead it seems to have acted as a sink for cultural materials and fossil remains transported from the surface via sinkholes despite the small number of finds from the test excavation it is possible that more extensive excavations may yield additional transported cultural and faunal evidence at greater depths c 2012 elsevier ltd all rights reserved

evidence for holocene changes in australian indonesian monsoon rainfall from stalagmite trace element and stable isotope ratios abstract trace element and stable isotope ratios from an active stalagmite lr06 b1 recovered from liang luar cave on the island of flores eastern indonesia are used to reconstruct the position of the austral summer inter tropical convergence zone and australian indonesian summer monsoon variability during the holocene uranium series dating of the stalagmite shows that it commenced growth 12 640 years ago with hiatuses spanning 8 560 to 6 420 and 3 670 to 2 780 years ago stalagmite mg ca and sr ca ratios correlate significantly with one another and with 18 o and 13 c throughout the record this suggests that the mg ca and sr ca ratios are dominated by prior calcite precipitation a process whereby degassing in the vadose zone during periods of low recharge causes deposition of calcite and disproportionate loss of ca 2 ions relative to mg 2 and sr 2 upstream of the stalagmite the degree of initial 234 u 238 u disequilibrium also appears to have been controlled by recharge to the overlying aquifer together with the mg ca sr ca and 18 o values the initial uranium isotope activity ratios 234 u 238 u i imply a generally drier early holocene coincident with a lower sea level and lower southern hemisphere summer insolation comparison of speleothem 18 o time series from flores and borneo shows that they vary in unison for much of the holocene however there is a significant decrease in the borneo 18 o record 6 000 to 4 000 years ago that does not occur in the flores record this anomaly may be related to a change in the australian indonesian summer monsoon circulation in response to a protracted positive phase of the indian ocean dipole under this scenario stronger upwelling off of western indonesia would based on present day effects result in reduced summer convective activity over flores and a subsequent northward shift of the intertropical convergence zone

stable isotopes in east african precipitation record indian ocean zonal mode observational stable isotope data and model simulations show that the 18 o composition of precipitation in east africa is closely related to the coupled ocean atmosphere system over the indian ocean during the rainy seasons 18 o is a very sensitive recorder of the indian ocean zonal mode iozm the link between 18 o and the iozm is established through adjustments in the large scale overturning circulation over the indian ocean and associated changes in convective activity and precipitation over east africa the iozm is recorded as significant departures in 18 o not only over east africa but as a dipole mode with opposite sign to the east and west of the indian ocean

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

stalagmite evidence for the precise timing of north atlantic cold events during the early last glacial evidence of millennial scale cold events following the last interglacial are well preserved in north atlantic marine cores greenland ice and pollen records from europe however their timing was previously undetermined by radiometric dating we report the first precise radiometric ages for two such events c23 105 1 0 9 ka to 102 6 0 8 ka and c24 112 0 0 8 ka and 108 8 1 0 ka based on stable carbon and oxygen isotope measurements on a stalagmite from italy cc28 in addition to providing new information on the duration of these events in southern europe the age data provide invaluable tuning points for the melisey i c24 and montaigu c23 pollen zones identified in western europe the former event is of particular significance because it represents the end of the eemian interglacial forest phase in western europe the new age data will also allow fine tuning of the timing and duration of greenland stadial 24 equivalent to c23 in the north greenland ice core project ice core and via a common gasage chronology tuning of the vostok and epica european project for ice coring in antarctica ice cores

palaeoenvironmental change in tropical australasia over the last 30 000 years a synthesis by the oz intimate group the tropics are the major source of heat and moisture for the australasian region determining the tropics response over time to changes in climate forcing mechanisms such as summer insolation and the effects of relative sea level on exposed continental shelves during the last glacial period is an ongoing process of re evaluation we present a synthesis of climate proxy data from tropical australasia spanning the last 30 000 years that incorporates deep sea core coral speleothem pollen charcoal and terrestrial sedimentary records today seasonal variability is governed largely by the annual migration of the inter tropical convergence zone itcz influencing this region most strongly during the austral summer however the position of the itcz has varied through time towards the end of marine isotope stage mis 3 conditions were far wetter throughout the region becoming drier first in the south universally cooler land and sea surface temperature sst were characteristic of the last glacial maximum with drier conditions than previously although episodic wet periods are noted in the fluvial records of northern australia the deglacial period saw warming first in the coral sea and then the indonesian seas with a pause in this trend around the time of the antarctic cold reversal c 14 5 ka coincident with the flooding of the sunda shelf wetter conditions occurred first in indonesia around 17 ka and northern australia after 14 ka the early holocene saw a peak in marine sst to the northwest and northeast of australia modern vegetation was first established on indonesia then progressively south and eastward to ne australia flores and the atherton tablelands show a dry period around 11 6 ka steadily becoming wetter through the early holocene the mid late holocene was punctuated by millennial scale variability associated with the el nino southern oscillation this is evident in the marine coral speleothem and pollen records of the region

87sr 86sr and sr ca in speleothems for paleoclimate reconstruction in central china between 70 and 280 kyr ago limestone cave deposits speleothems provide archives for past changes in regional climates over a range of timescales while 18o and 13c in speleothem calcite have been commonly used for reconstruction of paleoclimates we report here further efforts in the use of 87sr 86sr and sr ca signals in speleothem calcite to deduce paleomonsoon variability near the loess plateau of central china a two end member mass balance model of concentration and isotopic composition of strontium in a cave system is used to estimate variation of the 87sr 86sr ratio in sediments overlying a limestone cave we show that this ratio reflects climate driven variations in the provenance and the extent of chemical weathering of the epikarstic sediments the measurements of 87sr 86sr made on a well dated stalagmite sfl from buddha cave 33o40n 109o05 e show ratios of 0 71092 to 0 71133 0 00001 as 2 during relatively cold periods e g marine isotope stage mis 5b 5d and 8 lower than ratios of 0 71133 to 0 71194 during relatively warm periods e g mis 5a 5c 5e and 7 as changes in the sr ca ratio may affect speleothem 87sr 86sr we show that the direct use of speleothem 87sr 86sr is less ideal than our modeled 87sr 86sr for the exogenic sr source above the cave as a paleomonsoon proxy using the 18o 13c sr ca and 87sr 86sr records of the stalagmite we reconstruct the variability of the east asian monsoon for the time period between 70 and 280 kyr ago the results show that summer monsoons were more intense during interglacial periods than during glacial periods

trace element partition coefficients in the calcite water system and their paleoclimatic significance in cave studies abstract speleothems stalactites stalagmites formed in limestone caves have been found to contain much information on the timing and intensity of past climates from analysis of their u th 13c and 18o contents because the incorporation of certain trace elements e g mg mn and zn in calcite is known to be temperature dependent it may be possible to use variations in trace metal content of fossil speleothems as an alternative paleotem perature indicator using specially developed ion exchange sampling techniques analysis of trace metal content of seepage water and associated fresh calcite deposits in caves in vancouver island and jamaica shows that mg is distributed between phases in a consistent manner within the temperature regimes of the caves 7 and 23 c respectively average values of the distribution coefficient for mg are respectively 0 017 and 0 045 at these temperatures these results indicate that the mg content of calcite varies directly with temperature and in a sufficiently pronounced manner that a 1 c rise in depositional temperature of a speleothem containing 500 ppm mg at 10 c would be seen as an increase of 35ppm mg a readily determinable shift other factors affecting mg content of a speleothem are considered

complex speleothem growth processes revealed by trace element mapping and scanning electron microscopy of annual layers closely spaced transects measured by excimer laser ablation inductively coupled plasma mass spectrometry ela icpms at 5 and 32 m spatial resolution are used to generate trace element composition maps ba sr mg u na p and al from mnd s1 a previously studied modern stalagmite from southwest australia treble et al 2003 epsl216 141 rainfall at the site is highly seasonal and trace elements in mnd s1 show strong seasonal variation trace element maps show that ba sr u and na concentrations coherently follow annual growth layers identified from scanning electron microscopy sem images the sem images also reveal that stalagmite growth did not proceed uniformly growth layers vary in thickness and locally pinch out highly preferential crystal growth determined by nucleation sites left by the previous year s growth may be responsible for this uneven growth layering differential crystal growth apparently causes variability of trace element concentrations along each annual layer although additional disequilibrium processes affect mg which is less distinctly banded than ba sr u and na uneven and discontinuous growth layers influence the number of annual cycles their wavelengths and seasonal amplitudes measured in any one transect this has clear implications for studies that use annual trace element cycles as chronological markers growth rate or seasonality proxies

modification and preservation of environmental signals in speleothems speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system however the climatological meaning of many speleothem records cannot be interpreted unequivocally this is particularly so for more subtle shifts and shorter time periods but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward

a 780 year annually resolved record of indian ocean monsoon precipitation from a speleothem from south oman 1 meteorological records of monsoon rainfall in the indian ocean are generally less than 100 years long the relative brevity of these records makes it difficult to investigate monsoon variation on decadal and centennial timescales to determine what factors influence the intensity of rainfall on these timescales or to place possible changes in the twentieth century into a broader historical context development of a geologic proxy for rainfall that records annual variation in the monsoon over much longer time periods than are covered by instrumental records would be a significant step forward we have developed an annually resolved record of monsoon rainfall variation for the past 780 years based on annual layer thickness and stable isotope analyses of a laminated stalagmite from southern arabia our results show that monsoon variation over the past century is not outside of the range of the past 800 years decreasing monsoon rainfall over the past century is related to increasing sea surface temperature in the indian ocean spectral analyses of the record are dominated by cycles that are similar to those observed in records of solar activity on centurial timescales decadal to interannual cycles in the record appear to originate in the tropical pacific ocean index terms 3344 meteorology and atmospheric dynamics paleoclimatology 3354 meteorology and atmospheric dynamics precipitation 1854 1620 global change climate dynamics 3309 1699 global change general or miscellaneous keywords monsoon paleoclimate rainfall indian ocean speleothem oxygen isotopes

a stalagmite record of holocene indonesian australian summer monsoon variability from the australian tropics oxygen isotopic data from a suite of calcite and aragonite stalagmites from cave kni 51 located in the eastern kimberley region of tropical western australia represent the first absolute dated high resolution speleothem record of the holocene indonesianeaustralian summer monsoon iasm from the australian tropics stalagmite oxygen isotopic values track monsoon intensity via amount effects in precipitation and reveal a dynamic holocene iasm which strengthened in the early holocene decreased in strength by 4 ka with a further decrease from w2 to 1 ka before strengthening again at 1 ka to years to levels similar to those between 4 and 2 ka the relationships between the kni 51 iasm reconstruction and those from published speleothem time series from flores and borneo in combination with other data sets appear largely inconsistent with changes in the position and or organization of the intertropical convergence zone itcz instead we argue that the el nino southern oscillation enso may have played a dominant role in driving iasm variability since at least the middle holocene given the muted modern monsoon rainfall responses to most el nino events in the kimberley an impact of enso on regional monsoon precipitation over northwestern australia would suggest non stationarity in the long term relationship between enso forcing and iasm rainfall possibly due to changes in the mean state of the tropical pacific over the holocene

trace element distribution in annual stalagmite laminae mapped by micrometer resolution x ray fluorescence implications for incorporation of environmentally significant species abstract stalagmite er78 from grotta di ernesto cave in ne italy displays clear annual lamination consistent with its shallow depth below a forest ecosystem subject to autumnal peaking of water infiltration synchrotron radiation scanning micro x ray fluorescence analyses of heavy elements at european synchrotron radiation facility beamline id22 and light elements at id21 with 1 3 m resolution has been combined with data from ion microprobe analyses to reveal chemical variability across the visible layers of these annual laminae a series of elements display a symmetrical peak centered around the thin dark layer at the top of each lamina the peak concentration is ordered y zn cu and pb p and br this hierarchy is thought to reflect the selectivity of transport of these elements possibly by organic colloids flushed from the soil zone during autumn infiltration ion microprobe analysis indicates na and f also increase as does h the latter reflecting increased microporosity sr displays a trough around the dark and thin autumn layer implying that its incorporation may be limited by competition with other elements mg and s show a different pattern of annual variation and fe displays none the trace metals br and y display peak abundance in the early 20th century which appears to reflect a period of tree felling rather than a climatic anomaly the results demonstrate the power of the high spatial resolution and low detection limits of the synchrotron technique and its ability to produce quantitative maps that allow distinction of layered structure from that of isolated particles or irregular inhomogeneities

stalagmite evidence for the onset of the last interglacial in southern europe at 129 1 ka multi proxy data from an italian stalagmite constrain the commencement of full last interglacial conditions in southern europe at 129 1 ka consistent with absolutely dated records currently available from both hemispheres the post glacial transition towards warmer and wetter conditions commenced at 134 2 ka oxygen isotope evidence suggests this was interrupted briefly at 130 2 ka an event probably related to the termination ii pause associated with heinrich event 11 for most of the stalagmite the pattern of delta 18 o variation mimics the air temperature record from the vostok ice core especially through marine isotope stage 5 there is no obvious evidence for substantial early interglacial warming

late holocene drought responsible for the collapse of old world civilizations is recorded in an italian cave flowstone a severe drought in parts of low latitude northeastern africa and southwestern asia 4200 yr ago caused major disruption to ancient civilizations stable isotope trace element and organic fluorescence data from a calcite flowstone collected from the well watered alpi apuane karst of central western italy indicate that the climatic event responsible for this drought was also recorded in mid latitude europe although the timing of this event coincides with an episode of increased ice rafted debris to the subpolar north atlantic the regional ocean atmosphere response seems atypical of similar holocene ice rafting events furthermore comparison of the flowstone data with other regional proxies suggests that the most extreme part of the dry spell occurred toward the end of a longer term climate anomaly

holocene surface hydroclimate changes in the indo pacific warm pool abstract the indo pacific warm pool ipwp is an area hosting key tropical climate processes such as the el nino southern oscillation enso and indian ocean dipole iod the tropical climate processes via various feedback mechanisms control the surface ocean climate in the indian ocean and its surrounding continents on annual to inter annual timescales however little has been known about how the tropical processes are effective forcing climate mechanism over longer timescales here we presented a reconstruction of the spatiotemporal pattern of sea surface temperature sst with inferred hydroclimate changes since the early holocene 11ka using proxies of planktonic foraminifer shell mg ca organic biomarker tex86 foraminifer oxygen isotopes and a terrigenous bit index measured from a 220 cm long core bs24 2 724041 n 97 010943 e 1015 m water depth which was taken offshore of northwest sumatra in the eastern indian ocean with an age model of 13 ams 14c dating by the uses of planktonic foraminiferal shells from the core the tex86h temperatures of bs24 show as summer weighted and reflect integrated thermal effects from the surface to thermocline water while the mg ca temperature of bs24 better reflects mean annual sst our results along with a regional synthesis of published sst records from the ipwp suggest that the ipwp has migrated eastwardly since the mid holocene 5ka in phase with this eastward migration the ipwp ssts have decreased but the upwelling in the eastern indian ocean appears to have been a persistent feature since the mid holocene our empirical orthogonal function eof analysis on the compiled ipwp sst records indicates two dominant modes of spatio temporal variability of surface hydrographes in the ipwp that are attributed to a combined effect of orbital and solar forcing with expressions analogous to the indian ocean basin wide mode iobm and the indian ocean dipole model iod

controls on trace element sr mg compositions of carbonate cave waters implications for speleothem climatic records abstract at two caves clamouse s france and ernesto ne italy cave drip and pool waters were collected and sampled at intervals over a 2 3 year period mg ca and sr ca concentration ratios corrected for marine aerosols are compared with those of bedrocks and in some cases aqueous leachates of soils and weathered bedrocks cave waters do not lie along mixing lines between calcite and dolomite of bedrock carbonate but typically show enhanced and covarying mg ca and sr ca four factors are considered as controlling processes 1 the much faster dissolution rate of calcite than dolomite allows for the possibility of increase of mg ca if water rock contact times are increased during drier conditions a theoretical model is shown to be comparable to experimental leachates 2 prior calcite precipitation along a flow path is a powerful mechanism for generating enhanced and covarying mg ca and sr ca ratios this mechanism requires the solution to lose co 2 into pores or caverns 3 incongruent dolomite dissolution has only limited potential and is best regarded as two separate processes of dolomite dissolution and calcite precipitation 4 selective leaching of mg and sr with respect to ca is shown to be important in leachates from ernesto where it appears to be a phenomenon of calcite dissolution in general selective leaching can occur whenever ca is sequestered into precipitates due to freezing or drying of soils or if there is derivation of excess sr and mg from non carbonate species the ernesto cave has abundant water supply which in the main chamber is derived from a reservoir with year round constant p co 2 of around 10 2 4 and no evidence of calcite precipitation in the karst above the cave two distinct but overlying trends of enhanced and covarying mg ca and sr ca away from the locus of bedrock compositions are due to calcite precipitation within the cave and at a variable drip site due to enhanced selective leaching at slow drip rates mg enhancement in the first chamber is due to a more dolomitic bedrock and longer residence times the clamouse site has a less abundant water supply and presents geochemical evidence of prior calcite precipitation both in the cave and in overlying porous dolomite dedolomitized limestone bedrock initial p co 2 values as high as 10 1 are inferred experimental incubations of clamouse soils which generated enhanced p co 2 and precipitated caco 3 had compositions similar to the karst waters calcite precipitation is inferred to be enhanced in drier conditions hydrological controls on cave water chemistry imply that the trace element chemistry of speleothems may be interpretable in palaeohydrological terms drier conditions tends to promote not only longer mean residence times enhancing dolomite dissolution and hence mg ca but also enhances degassing and calcite precipitation leading to increased mg ca and sr ca

climate variability over the last 35 000 years recorded in marine and terrestrial archives in the australian region an oz intimate compilation abstract the australian region spans some 60 of latitude and 50 of longitude and displays considerable regional climate variability both today and during the late quaternary a synthesis of marine and terrestrial climate records combining findings from the southern ocean temperate tropical and arid zones identifies a complex response of climate proxies to a background of changing boundary conditions over the last 35 000 years climate drivers include the seasonal timing of insolation greenhouse gas content of the atmosphere sea level rise and ocean and atmospheric circulation changes our compilation finds few climatic events that could be used to construct a climate event stratigraphy for the entire region limiting the usefulness of this approach instead we have taken a spatial approach looking to discern the patterns of change across the continent the data identify the clearest and most synchronous climatic response at the time of the last glacial maximum lgm 21 3 ka with unambiguous cooling recorded in the ocean and evidence of glaciation in the highlands of tropical new guinea southeast australia and tasmania many terrestrial records suggest drier conditions but with the timing of inferred snowmelt and changes to the rainfall runoff relationships driving higher river discharge at the lgm in contrast the deglaciation is a time of considerable south east to north west variation across the region warming was underway in all regions by 17 ka post glacial sea level rise and its associated regional impacts have played an important role in determining the magnitude and timing of climate response in the north west of the continent in contrast to the southern latitudes no evidence for cooling during the younger dryas chronozone is evident in the region but the antarctic cold reversal clearly occurs south of australia the holocene period is a time of considerable climate variability associated with an intense monsoon in the tropics early in the holocene giving way to a weakened monsoon and an increasingly el nino dominated enso to the present the influence of enso is evident throughout the southeast of australia but not the southwest this climate history provides a template from which to assess the regionality of climate events across australia and make comparisons beyond our region

sensitivity of the australian summer monsoon to tilt and precession forcing abstract the response of the australian summer monsoon to orbital forcing is studied using a coupled general circulation model gcm with the focus on the relative roles of tilt and precession on the forcing of the northern australian summer monsoon it was found that unlike the northern hemisphere monsoons which are dominated by precession forcing the australian monsoon can be enhanced significantly not only by precession forcing but also by tilt forcing coupled to oceanic feedback the new insights obtained from a series of experiments with differing tilt precession configurations allow an interpretation of the australian late quaternary monsoon record in which insolation forcing plays a significant role

australasian monsoon response to dansgaard oeschger event 21 and teleconnections to higher latitudes abstract dansgaard oeschger d o cycles were the most prominent abrupt climate events of the last glacial period whose impact was most strongly felt in the high latitudes of the north atlantic region the climate links between the north atlantic the asian and american tropics and antarctica during these cycles are well documented however the potential role of the indo pacific warm pool and australasian monsoon system in propagating climate impacts across the hemispheres is still unclear here we use tandem measurements of oxygen isotopes in calcite and fluid inclusions as well as carbon isotope ratios from multiple stalagmites from liang luar cave flores southern indonesia to examine the monsoon response to d o event number 21 87 000 84 000 years ago the longest and warmest event recorded in greenland ice cores the record shows that there was a rapid decline in monsoon rainfall in indonesia during d o21 warming in greenland and cooling in antarctica at around the same time the east asian monsoon was intensified indicating that the intertropical convergence zone itcz shifted abruptly to the north during this event our record also shows that there was a 2 3 c increase in local air temperature which would have acted to increase primary productivity and promote the generation of soil carbon for methanogenesis therefore our findings indicate that itcz positioning in tropical australasia through its influence on large scale oceanic atmospheric circulation played a key role in transmitting the abrupt climate signal between the hemispheres thereby facilitating the rapid rise of atmospheric co 2 and ch 4 concentrations during d o21 that ultimately led to global warming and the demise of the mis5b stadial

abrupt increase in east indonesian rainfall from flooding of the sunda shelf 9500 years ago we present a precisely dated multi proxy stalagmite record from liang luar cave flores southeast indonesia that reveals a rapid increase in indonesian monsoon rainfall at 9 5 ka a ramp fitting method for detecting statistically significant inflections in a time series was applied to the stalagmite 18o mg ca and sr ca profiles to quantify the precise timing and magnitude of an abrupt increase in monsoon strength over a period of 350 years previously published lake level records from the monsoon affected australian interior show a sudden intensification of the australian monsoon at 14 ka however our records indicate that monsoon intensification in flores occured 4 5 kyr later the timing of the monsoon shift in flores is synchronous with the rapid expansion of rainforest in northeast australia and regional freshening of the southern makassar strait which under present day conditions is sensitive to monsoon variability the freshening of southern makassar was coeval with an abrupt 1 5 c cooling in the upper thermocline of the timor sea 9 5 ka indicative of reduced surface heat transport by the indonesian throughflow itf when the java sea opened during postglacial sea level rise this suggests that the abrupt increase in monsoon rainfall on flores was not due to a change in the itf because a decrease in rainfall would be expected to accompany cooler local sea surface temperatures ssts but rather by the sudden increase in ocean surface area and or temperature in the monsoon source region as the sunda shelf flooded during deglaciation we propose that it was the abrupt intensification of the monsoon through the late deglaciation that maintained the subsequent structure of the itf following the flooding of the sunda shelf at 9 5 ka

late quaternary milankovitch scale climatic change and variability and its impact on monsoonal australasia four pollen and charcoal records derived from marine cores around the northern perimeter of australia are examined to provide a regional picture of patterns causes and impacts of climate change over the last 100 300 ka the availability of radiocarbon dates and oxygen isotope records for the cores provides primary chronological control spectral analysis of components of these records demonstrates an overall importance of milankovitch frequencies with clear glacial interglacial cyclicity dominated by variation in precipitation in addition a number of pollen taxa as well as charcoal particles exhibit a 30 ka frequency that is considered from its relationship with biomass burning and with results of past modelling to reflect changes in the intensity of el nino southern oscillation enso variability pollen components of all records show a decline frequently stepwise in more fire sensitive vegetation and its replacement with more fire tolerant vegetation there is some evidence that this trend is linked to an onset or general increase in enso activity and perhaps also to variation in monsoon activity dating from about 300 ka bp that was caused by changes to oceanic circulation within the indonesian region the trend may have accelerated within the last 45 ka due to burning by indigenous people c 2003 elsevier b v all rights reserved

two phases of the holocene east african humid period inferred from a high resolution geochemical record off tanzania during the holocene the most notably climatic change across the african continent is the african humid period ahp however the pace and primary forcing for this pluvial condition is still ambiguous particularly in east africa we present a high resolution marine sediment record off tanzania to provide insights into the climatic conditions of inland east africa during the holocene major element ratios i e log ratios of fe ca and ti ca derived from x ray fluorescence scanning have been employed to document variations in humidity in east africa our results show that the ahp is represented by two humid phases an intense humid period from the beginning of the holocene to 8 ka ahp i and a moderate humid period spanning from 8 to 5 5 ka ahp ii on the basis of our geochemical record and regime detection the termination of the ahp initiated at 5 5 ka and ceased around 3 5 ka combined with other paleoclimatic records around east africa we suggest that the humid conditions in this region responded to northern hemisphere nh summer insolation the ahp i and ii might have been related to an eastward shift of the congo air boundary and warmer conditions in the western indian ocean which resulted in additional moisture being delivered from the atlantic and indian oceans during the nh summer and autumn respectively we further note a drought event throughout east africa north of 10 s around 8 2 ka which may have been related to the southward migration of the intertropical convergence zone in response to the nh cooling event

partitioning of mg sr ba and u into a subaqueous calcite speleothem abstract the trace element geochemistry of speleothems is becoming increasingly used for reconstructing palaeoclimate with a particular emphasis on elements whose concentrations vary according to hydrological conditions at the cave site e g mg sr ba and u an important step in interpreting trace element abundances is understanding the underlying processes of their incorporation this includes quantifying the fractionation between the solution and speleothem carbonate via partition coefficients where the partitioning d of element x dx is the molar ratio x ca in the calcite divided by the molar ratio x ca in the parent water and evaluating the degree of spatial variability across time constant speleothem layers previous studies of how these elements are incorporated into speleothems have focused primarily on stalagmites and their source waters in natural cave settings or have used synthetic solutions under cave analogue laboratory conditions to produce similar dripstones however dripstones are not the only speleothem types capable of yielding useful palaeoclimate information in this study we investigate the incorporation of mg sr ba and u into a subaqueous calcite speleothem cd3 growing in a natural cave pool in italy pool water measurements extending back 15 years reveal a remarkably stable geochemical environment owing to the deep cave setting enabling the calculation of precise solution x ca we determine the trace element variability of modern subaqueous calcite from a drill core taken through cd3 to derive dmg dsr dba and du then compare these with published cave cave analogue and seawater analogue studies the dmg for cd3 is anomalously high 0 042 0 002 compared to previous estimates at similar temperatures 8 c the dsr 0 100 0 007 is similar to previously reported values but data from this study as well as those from tremaine and froelich 2013 and day and henderson 2013 suggest that na sr might play an important role in sr incorporation through the potential for na to outcompete sr for calcite non lattice sites dba in cd3 0 086 0 008 is similar to values derived by day and henderson 2013 under cave analogue conditions whilst du 0 013 0 002 is almost an order of magnitude lower possibly due to the unusually slow speleothem growth rates

stalagmite carbon isotopes and dead carbon proportion dcp in a near closed system situation an interplay between sulphuric and carbonic acid dissolution in this study the dead carbon proportion dcp calculated from combined u th and radiocarbon analyses was used to explore the carbon isotope systematics in corchia cave italy speleothems using the example of stalagmite cc26 which grew during the last 12 ka the dcp values in cc26 are among the highest ever recorded in a stalagmite spanning the range 44 8 68 8 a combination of almost closed system conditions and sulphuric acid dissolution sad are proposed as major drivers in producing such a high dcp with minor contribution from old organic matter from the deep vadose zone the long term decrease in both dcp and 13c most likely reflects post glacial soil recovery above the cave with a progressive increase of soil co2 contribution to the total dissolved inorganic carbon dic pronounced millennial scale shifts in dcp and relatively small coeval but antipathetic changes in 13c are modulated by the effects of hydrological variability on open and closed system dissolution sad and prior calcite precipitation hence the dcp in corchia cave speleothems represents an additional proxy for rainfall amount

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

younger dryas holocene temperature and rainfall history of southern indonesia from delta o 18 in speleothem calcite and fluid inclusions abstract we have applied a new technique to analyze the oxygen 18o and hydrogen d isotope ratios in speleothem fluid inclusions to reconstruct the temperature and rainfall history of southern indonesia during the younger dryas yd event and the holocene the 12 640 year speleothem record anchored by 33 uranium series dates shows that fluid inclusion 18o values vary in phase with speleothem calcite 18o during the holocene suggesting that the speleothem calcite 18o primarily reflects variations in the 18o of local rainfall significant early to mid holocene decreases in both 18o series are interpreted as an intensification of australian indonesian summer monsoon rainfall in response to deglacial eustatic sea level rise and flooding of the sunda shelf cave drip water temperatures reconstructed from coupled measurements of 18o in speleothem calcite and fluid inclusions remained relatively constant through the holocene this is consistent with reconstructions of indo pacific sea surface temperature sst based on analysis of mg ca ratios in planktonic foraminifera however during the yd event drip water i e cave temperature was 5 c cooler than modern which is substantially cooler than ssts inferred from foraminiferal mg ca but consistent with coral sr ca reconstructions of sst and terrestrial evidence for high elevation snow line depressions lower fluid inclusion 18o values during the yd indicate that the cooling was accompanied by increased monsoon rainfall taken together the results suggest that the southerly penetration of the intertropical convergence zone itcz was largely influenced by the cross equatorial temperature gradient rather than local ssts and air temperatures our results provide new evidence for a rapid cooling of deep tropical air temperatures and repositioning of the itcz during the yd event

enso related decadal scale climate variability from the indo pacific warm pool the el nino southern oscillation enso is a climatic phenomenon that affects socio economical welfare in vast areas in the world a continuous record of holocene enso related climate variability of the indo pacific warm pool ipwp is constructed on the basis of stable oxygen isotopes in shells of planktic foraminifera from a sediment core in the western pacific ocean at the centennial scale variations in the stable oxygen isotope signal delta o 18 are thought be a representation of enso variability although an imprint of local conditions cannot be entirely excluded the record for the early holocene 10 3 6 ka bp shows in comparison with the mid to late holocene small amplitude variations in the delta o 18 record of up to 0 3 parts per thousand indicating relatively stable and warm sea surface conditions the mid to late holocene 6 2 ka bp exemplified higher variability in delta o 18 and thus in oceanic ipwp conditions climatically we interpret this change 5 5 4 2 ka bp as a phenomenon induced by variability in frequency and or intensity changes of el nino in the period 4 2 2 ka bp we identified several periods centred on 1 9 2 1 2 7 3 3 3 7 and 4 2 ka bp with in general heavy 6180 values during these periods the ipwp was relocated to a more eastward position enhancing the susceptibility for el nino like conditions at the core site over the last 2000 yr precipitation increased in the area as a response to an increase in asian monsoon strength resulting in a freshening of the surface waters this study corroborates previous findings that the present day enso activity started around 5 5 ka bp c 2006 elsevier b v all rights reserved

mid holocene sea surface conditions and riverine influence on the inshore great barrier reef we present measurements of sr ca 18o and spectral luminescence ratios g b from a mid holocene porites sp microatoll recovered from the nearshore great barrier reef gbr these records were used as proxies to reconstruct sea surface temperature sst the 18o of surrounding seawater 18osw and riverine influence respectively and compared with records from a modern porites sp microatoll growing in the same environment strong riverine influence in the mid holocene record is indicated by 1 an increased annual 18osw range in the mid holocene record 2 negative peaks in 18o characteristic of flood events and 3 a higher g b luminescence ratio seasonal cycles in g b suggest that humic acid inputs were elevated for a longer portion of the year during the mid holocene the seasonal cycle of 18osw peaked earlier in the year in the mid holocene record relative to the modern while mean 18osw values from the mid holocene record were similar to modern values these records provide an insight into the oceanographic conditions the nearshore gbr experienced during mid holocene climatic shifts and are consistent with a strong australian indonesian summer monsoon aism system at 4700 cal yr bp

speleothem based paleoclimate record from northern oman u th age dating and stable isotope measurements of speleothems from hoti cave in northern oman yield paleoclimate information from the region extending to 125 ka the results 1 provide further confirmation of an early holocene wet period in southern arabia extending from some time prior to 9 7 ka and ending at 6 2 ka 2 demonstrate a second period of wetness closely coinciding with the last interglacial period marine isotope stage mis 5e 3 indicate that during mis 5e southern arabia was considerably wetter than during the early holocene and 4 demonstrate that periods of increased monsoon wind strength based on data from marine sediments do not always coincide with evidence of greatly increased precipitation even from nearby continental areas

the holocene environmental changes in southern indonesia reconstructed from highland caldera lake sediment in bali island diatom pollen geomagnetic and geochemical analyses were carried out on a 3 6 m long sediment core taken from lake buyan a highland caldera lake in central bali island to reconstruct the holocene climate changes in equatorial southern indonesia the core represents 8 thousand years sedimentation of organic diatomaceous lake mud constant inclusion of benthic diatom fossils as main components indicated that suspension and inflow of littoral materials were the main sedimentary process the core contained laminated sediments in two distinct intervals at 6 5 5 0 and 3 6 3 1 cal ky bp and multi proxy records showed generally drier climate in these sections especially at 3 6 3 1 cal ky bp lake bottom waters were more reducing condition in these laminated periods probably due to increased lake productivity by prolonged dry season and wind mixing laminae structures were made up of a layer composed of benthic diatoms and amorphous organic materials and a layer made by only planktonic diatom fossils each of which may represent rainy and dry period deposits although southern indonesia shows clear australian monsoon rainfall seasonality at present counting of layer numbers showed interannual cycles of laminae formation prolonged dry seasons could obscured the rainfall seasonality in these periods but precise depositional patterns were elusive unlaminated sections showed homogeneous sediment mixture of benthic planktonic diatoms and more volume of terrigenous materials indicating wetter climate and seasonality similar to the present time this was supported by the higher share of marsh environment pollens reflecting more stable lake level trends the dry climate from 6 5 cal ky bp was in line with the general perception of stronger enso dynamics from the mid holocene due to weaker than before boreal summer insolation but the sporadic appearances of dry periods imply the influence of regional climate forcings such as temporal migrations of inter tropical convergence zone itcz it was however possible that temporal shifts of large climate mode occurred in equatorial pacific and indian oceans wettest climate was inferred from 3 1 cal ky bp to the present and this might reflect increased importance of austral hemisphere atmospheric convection and subsequent southerly position of itcz in austral summer time

new type of compositional zoning in calcite insights into crystal growth mechanisms compositional zoning of trace elements is observed in time equivalent regions within 10 overline 1 4 growth sectors of natural and synthetic calcite single crystals and has been called intrasectoral zoning to distinguish it from conventional sectoral zoning differential interference contrast microscopy shows that 101 overline 1 4 faces grow by the spiral mechanism cathodoluminescence microscopy and electron probe microanalyses reveal that trace element partitioning differences on 101 overline 1 4 faces correspond exactly to crystallographically controlled orientations of growth steps effective partitioning of mg and mn varies up to a factor of four between time correlative growth steps spreading in different directions effective sr partitioning varies by approximately 20 and is inversely correlated with enrichment trends of mg and mn preferential incorporation of different aqueous species at different growth steps may provide an explanation for morphological and chemical variation in natural calcites

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

the 2002 2003 el nino recorded in australian cave drip waters implications for reconstructing rainfall histories using stalagmites 1 a 30 month study of drip hydrochemistry from kooringa cave eastern australia revealed a clear geochemical response to the 2002 2003 el nino through the drought drip discharge fell to base flow drip ca2 concentrations fell by half and drip mg ca and sr ca increased in a co varying pattern calcite mg ca and sr ca predicted from drip waters displayed a marked increase through and just beyond the period of greatest moisture deficit the results suggest that stalagmites from shallow caves in drought sensitive eastern australia potentially preserve a valuable record of el nino la nina history

rapid measurement of strontium in speleothems using core scanning micro x ray fluorescence abstract speleothem trace element ratios such as mg ca and sr ca are increasingly used in speleothem paleoclimatology as a supplement to stable oxygen and carbon isotope ratios as proxies for past variability in the hydrologic system using multiple proxies together allows for a better understanding of both the local and distal hydrologic changes recorded in speleothem chemistry and therefore of changes in past rainfall despite the potential benefits trace element analysis of speleothems has yet to become widespread which is likely due to the significant time and costs required by traditional trace element analytical techniques in this study we present an in depth investigation into a rapid relatively non destructive and competitively priced technique for measuring sr ca in speleothems core scanning micro x ray fluorescence cs xrf we show that cs xrf reliably and precisely records sr concentration in speleothems ratioed to near stoichiometric ca the sr ca ratio accounts for variations in beam strength and machine settings producing a more reliable reported measurement for both intra and inter run comparisons cs xrf compares favorably with more conventional trace element procedures such as quadrupole icp ms and icp aes giving confidence in the ability of cs xrf to produce paleoclimatologically significant sr ca results we also identify secondary issues relating to speleothem crystallinity the dominance of ca spectral peaks and comparatively lower energy x rays that can interfere with precise cs xrf analyses if these can be overcome then cs xrf may provide an even more useful method of trace element analysis in speleothem studies

trace element variations and dating of a late pleistocene tasmanian speleothem abstract a calcitic stalagmite from lynds cave a limestone cave near mole creek in northern tasmania australia has been dated and shows continuous deposition at a uniform rate from 15 0 to 11 7 ka b p ionium dates or 12 6 8 8 ka b p radiocarbon dates the age difference obtained by comparing the two dating methods is highly significant and strongly supports recent work by bard et al 1990 on barbados corals the speleothem was found to be unsuitable for palaeotemperature estimation by oxygen isotope analysis but the time of deposition is known to have been one rapidly rising temperatures trace element composition was determined by neutron activation analysis naa for fifteen samples spaced along the stalagmite core all elements present in measurable quantities showed significant temporal variation in concentrations which are in part believed to be due to environmental change a significant positive trend in mg sr content and a negative trend in br content appear to be temperature related the halide content is shown to be of terrestrial origin

phosphorus speciation in calcite speleothems determined from solid state nmr spectroscopy abstract variations in speleothem p concentration show cyclic patterns that have important implications for high resolution palaeoclimate and palaeoenvironmental reconstructions however little is known about the speciation of p in calcite speleothems here we employ solid state 31p and 1h magic angle spinning nuclear magnetic resonance mas nmr spectroscopic techniques as a non destructive method for analyzing the distribution of p in speleothems the 31p mas nmr results show three peaks indicating the presence of three primary types of phosphate species in samples from the grotta di ernesto northeastern italy a broad peak at a chemical shift p 31 3 1 to 3 7 ppm from individual phosphate ions incorporated within calcite a narrow set of peaks near p 31 0 9 ppm from crystalline monetite and a narrow peak at p 31 2 9 ppm from an unidentified crystalline phosphate phase essentially identical results were obtained for a synthetic calcite phosphate coprecipitate spectra collected for a sample from grotte de clamouse southern france show only a broad peak near 3 5 ppm suggesting a possible limit for phosphate incorporation into the calcite structure these data suggest that p in this system can interact to form calcium phosphate surface precipitates during infiltration events and are subsequently enclosed during calcite growth

climatic backdrop to the terminal pleistocene extinction of north american mammals north american terminal pleistocene mammal extinctions are the subject of a long running scientifi c debate although the role of climate has fi gured centrally we lack clear knowledge of the timing and nature of terminal pleistocene climate variability herein we document lengthy terminal pleistocene drought in the southwestern united states usa using 13 c and 234 u effective moisture proxy data in speleothem calcite stalagmite fs2 from fort stanton cave new mexico supplemented with age data from pool basin shelfstone speleothems from the big room in carlsbad cavern this terminal pleistocene drought defi ned by a sharp rise in both 13 c and 234 u values began just before 14 5 k y ago and lasted at least until 12 9 k y ago when it was briefl y and only mildly interrupted by the younger dryas the timing and length of this drought 1500 yr match the northern hemisphere bolling allerod oscillation preserved in greenland ice cores and exhibited in the 18 o record of stalagmite fs2 rapid transition from cool moist late glacial to warm dry holocenelike climatic conditions was likely unfavorable to many species of pleistocene mammals in the southwestern usa a climate induced extinction implies that this last glacial cycle and its termination were more extreme than previous glacial cycles and or glacial terminations

multi scale variability of the asian monsoon recorded in an annually banded stalagmite during the neoglacial from qixing cave southwestern china abstract solar forcing of the asian summer monsoon asm and the embedded feedback mechanism remain highly controversial in this study interannual scale asm variability from 3 58 to 2 28 ka bp is reconstructed based on the 18 o record of an annually laminated stalagmite from qixing cave in southwestern china the cave 18 o record agrees well with a record of solar activity on the centennial scale during the whole time series furthermore statistical analysis of singular spectrum and wavelet spectrum shows a significant cycle of 60 years one of the solar activity cycles the two lines of evidence have consolidated the solar impact on a centennial decadal time scale of asm variability timing and structure of the 2 8 ka event detected in various archives at a global scale have been well determined in our 18 o record with a high precision time scale established by absolute 230 th dating and annual layer counting we observed an asymmetrical pattern of the event i e a gradual transition at the onset with a rapid end which can be interpreted as a far field effect of changing thermohaline circulations in the north atlantic we further demonstrate a striking inverse correlation between the asm and the indonesian australian summer monsoon iasm on the centennial scale including three dominant asm depression events that are related to periods of weak solar activity the evidence we present here supports that ocean atmosphere interactions amplified the solar signal and caused abrupt cooling events in widespread areas during the holocene

successive phases of holocene reef flat development evidence from the mid to outer great barrier reef a re examination of 46 recently published u th reef flat ages from heron and one tree reefs in the southern great barrier reef gbr identified several distinct holocene reef growth phases with a clear 2 3 kyr hiatus in lateral reef accretion from 3 9 ka to 1 5 ka an analysis of all available published radiocarbon reef flat ages 165 from 27 other mid outer platform reefs revealed a similar hiatus between 3 6 ka and 1 6 ka for the northern south central and southern gbr however no hiatus in reef flat growth was observed in reefs from the central gbr with ages ranging from 7 6 ka to 0 9 ka increased upwelling turbidity and cyclone activity in response to increased sea surface temperature sst s precipitation and el nino southern oscillation variability have been ruled out as possible mechanisms of reef turn off for the mid outer platform reefs rather a fall 0 5 m in relative sea level at 4 3 5 ka is the most likely explanation for why reefs in the northern and southern regions turned off during this time greater hydro isostatic adjustment of the central gbr and long term subsidence of the halifax basin may have provided greater vertical accommodation for the mid outer reefs of the central gbr thus allowing these reefs to continue to accrete vertically despite a fall in sea level 4 3 5 ka further evidence for greater subsidence in this region includes the lack of senile reefs and dominance of incipient and juvenile reefs in the central gbr this suggests that these reefs approached sea level considerably later than the northern and southern reefs consistent with their deeper antecedent substrates thus these results not only provide important information about possible reef flat demise in response to natural environmental factors but also provide insights into regional subsidence that affected relative sea level along the east australian margin during the holocene

hydrological and vegetation shifts in the wallacean region of central indonesia since the last glacial maximum abstract precipitation is the most important variable of indonesian climate yet there are substantial uncertainties about past and future hydroclimate dynamics over the region this study explores vegetation and rainfall and associated changes in atmospheric circulation during the past 26 000 years in wallacea a biogeographical area in central indonesia wedged between the sunda and sahul shelves and known for its exceptionally high rainforest biodiversity we use terrestrial plant biomarkers from sediment cores retrieved from mandar bay off west sulawesi to reconstruct changes in wallacean vegetation and climate since the last glacial maximum lgm enriched leaf wax carbon isotope 13cwax values recorded in mandar bay during the lgm together with other regional vegetation records document grassland expansion implying a regionally dry and possibly more seasonal glacial climate depleted leaf wax deuterium isotope dwax values in mandar bay during the lgm and low reconstructed precipitation isotope compositions from nearby sites reveal an intensified austral asian summer monsoon circulation and a southward shift of the mean position of the intertropical convergence zone likely due to strong southern hemisphere summer insolation and the presence of large northern hemisphere ice sheets mandar bay 13cwax was anti correlated with dwax during the lgm and the last deglaciation but was positively correlated during most of the holocene indicating time varying controls on the isotopic composition of rainfall in this region the inundation event of the sunda shelf and in particular the opening of the java sea and karimata strait between 9 4 and 11 1 thousand years ago might have provided new moisture sources for regional convection and or influenced moisture source trajectories providing the trigger for shifts in atmospheric circulation and the controls on precipitation isotope compositions from the lgm to the holocene

global patterns of enso induced precipitation although there have been many analyses of el nino southern oscillation enso induced precipitation anomalies global patterns from these analyses remain incomplete here we combine recent satellite estimates of oceanic precipitation and historical rain gauge records to derive a global climatology of enso induced precipitation anomalies using empirical orthogonal function eof analyses the patterns suggest that the re arrangement of convection centers of the walker circulation during enso events induces large precipitation anomalies in the tropics while associated changes in the monsoon systems through the hadley cell over the pacific indian and atlantic oceans and their interactions with midlatitude westerlies generate coherent anomaly patterns over the extratropics our results can be used to evaluate climate models and forecast enso induced precipitation anomalies

continuous 150 k y monsoon record from lake eyre australia insolation forcing implications and unexpected holocene failure our reconstructed history of lake eyre provides the first continuous continental proxy record of australian monsoon intensity over the past 150 k y this continental record s broad correspondence to the marine isotope record demonstrates that this very large catchment with its hydrology dependent on a planetary scale climate element responds to milankovitch scale climate forcing abrupt transitions from dry phases to wet phases ca 125 and 12 ka coincide with northern hemisphere winter insolation minima rather than southern hemisphere summer insolation maxima indicating that northern hemi sphere insolation exerts a dominant control over the intensity of the australian monsoon stratigraphic and dating uncertainties of other wet phases preclude conclusive correlation to specific insolation signals but within the uncertainties are consistent with northern hemisphere forcing regardless of the hemispheric forcing the low intensity of the early holocene australian monsoon by comparison with the last interglacial and particularly the last high level lacustrine event at 65 60 ka when all forcing elements were modest is an enigma that can be explained by a change in boundary conditions within australia

evidence of holocene surface and near surface palaeofires in karst caves and soils abstract black deposits covering speleothems cave walls and floors in postojna cave and predjama cave sw slovenia and charcoal found in soil outside the postojna cave were studied in order to establish their origin and age sem eds analysis of these deposits from both caves indicated that they are charred plant remains very similar to oxidised charcoal in soil stable carbon isotope 13 c values of 29 41 crna jama p1 26 9 predjama and 25 1 charcoal in soil confirm their origin from biomass burning radiocarbon dating from postojna cave crna jama p1 8394 35 cal yr b p and pisani rov 8235 25 cal yr b p suggests that the oldest analysed black deposits formed in the early holocene mesolithic the age is consistent with soil charcoal found at 1 m depth in the surrounding area black deposits from predjama were dated to 4095 25 cal yr b p eneolithic and were caused by burning fires at the cave entrance as supported by archaeological remains prehistoric 2375 20 cal yr b p charcoal from the upper part of the soil profile 0 5 to 0 6 m and historic 1240 29 cal yr b p or 745 cal yr ce black deposits from postojna cave crna jama p2 are related to forest fires which are most likely human induced we interpret the oldest dated black deposits in postojna cave as traces of early holocene natural forest fires since fire activity inside crna jama and pisani rov is not supported by archaeological remains favourable cave entrance morphology and microclimate allowed smoke to enter the cave during the winter period and deposit on speleothems but an anthropogenic cause of forest fires cannot be excluded since there are well documented mesolithic archaeological cave sites located close to the area the study shows that black deposits on speleothems in caves are an important palaeoenvironmental record and proxy for holocene climate

late pleistocene to holocene composite speleothem 18o and 13c chronologies from south island new zealand did a global younger dryas really exist oxygen and carbon data from eight stalagmites from northwest south island are combined to produce composite records of delta 18 o and delta 13 c from 23 4 ka to the present the chronology is anchored by 43 thermal ionization mass spectrometry tims uranium series ages delta o 18 values are interpreted as having a first order positive relationship to temperature but also to be influenced by precipitation in a complex manner delta c 13 is interpreted as responding negatively to increases in atmospheric co concentration biological activity and precipitation amount six climatic phases are recognized after adjustment of 1 2parts per thousand for the ice volume effect the delta 18 o record between 23 and 18 ka varies around 3 72parts per thousand compared to the holocene average of 3 17parts per thousand late glacial warming commenced between 18 2 and 17 8 ka and accelerated after 16 7 ka culminating in a positive excursion between 14 70 and 13 53 ka this was followed by a significant negative excursion between 13 53 and 11 14 ka of up to 0 55parts per thousand depth that overlapped the antarctic cold reversal acr and spanned the younger dryas yd positive delta 18 o excursions at 11 14 ka and 6 91 6 47 ka represent the warmest parts of the holocene the mid holocene from 6 to 2 ka was marked by negative excursions that coincide with increased glacial activity in the south island a short positive excursion from 0 71 to 0 57 ka was slightly later than the medieval warm period of europe delta c 13 values were high until 17 79 ka after which there was an abrupt decrease to 17 19 ka followed by a steady decline to a minimum at 10 97 ka then followed a general increase suggesting a drying trend to 3 23 ka followed by a further general decline the abrupt decrease in delta values after 17 79 ka probably corresponds to an increase in atmospheric co2 concentration biological activity and wetness at the end of the last glaciation but the reversal identified in the delta 18 o record from 13 53 to 11 14 ka was not reflected in delta 13 c changes the lowest delta 13 c values coincided with the early holocene climatic suboptimum when conditions were relatively wet as well as mild major trends in the delta 18 o c record are similar to the northern hemisphere but second order detail is often distinctly different consequently at the millennial scale a more convincing case can be made for asymmetric climatic response between the two hemispheres rather than synchronicity c 2004 elsevier b v all rights reserved

speleothem trace element signatures a hydrologic geochemical study of modern cave dripwaters and farmed calcite trace element variations in ancient cave speleothems are often interpreted as indicators of changes in paleo rainfall and hydrologic conditions however these records are difficult to interpret without an understanding of the physicochemical controls on stalagmite chemistry plus site specific calibration of changes in net rainfall to variations in dripwater and speleothem chemistry in this study we examine geochemical relationships between net rainfall precipitation minus evapotranspiration p et drip rates drip water chemistry and contemporaneous calcite chemistry to test the hypothesis that speleothem mg ca and sr ca records are proxies for rainfall amount hrc is contained within four low magnesium limestone units capped sporadically by a remnant dolomitic limestone aqueous concentrations of magnesium post evapotranspiration decrease with increasing vertical travel distance between the soil zone and the point of in cave drip emergence drip path length dpl as dissolved high mg solutions sourced from the dolomitic caprock are diluted with dissolved low mg limestone waters sourced from the host limestone dripwater mg ca and sr ca ratios covary and provide diagnostic indicators of the two dominant mechanisms controlling dripwater chemistry 1 mixing of post evaporative solutions derived from two geochemical endmembers dissolution of dolomite and limestone and 2 evolution of hydrochemistry away from dissolved bedrock compositions due to prior calcite precipitation pcp above the drip sites by resolving the linear mixing relationships for drip water mg ca and sr ca sources and the distribution coefficients for trace element transfer in the pcp dripwater to calcite precipitation reactions and applying these principles to our time series we find that the extent of pcp production within the karst is directly controlled by the balance between precipitation p and evapotranspiration et higher net rainfall p et 1 wet conditions reduces pcp and lower net rainfall with increased evapotranspiration p et 1 increases pcp farmed calcite x ca ratios faithfully track hydrologically influenced seasonal variations in dripwater chemistry for x mg sr and na however the relationship between changes in net rainfall and changes in mg ca and sr ca ratios in modern calcite is unique at each site and differs significantly at closely spaced drip stalagmite locations this suggests that in situ modern hydrochemical calibrations should be performed atop individual speleothems prior to harvesting for paleoclimate investigations and that such calibrations may not reflect past conditions as drip paths change we apply this understanding to published dripwater data and speleothem time series from other caves a major implication is that in order to interpret stalagmite sr ca and mg ca ratios as wet vs dry proxies speleothem sr ca and mg ca variations must be coherent and in phase over all time periods i e sr mg ratios must be constant these criteria will help to distinguish rainfall amount versus rainfall source in speleothem 18o records

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

petrography strontium barium and uranium concentrations and strontium and uranium isotope ratios in speleothems as palaeoclimatic proxies soreq cave israel the reconstruction of the palaeoclimate of the eastern mediterranean region for the last 60 ka bp is based on the 18o and 13c variations of speleothems from soreq cave israel climatic conditions during most of the time interval between 60 and 17 ka bp the period equivalent to the last glacial were relatively cold and dry while they were warmer and wetter from 17 ka bp to the present at 17 ka bp there was a major climatic change with a sharp increase in annual rainfall and temperature and a very wet period occurring between 8 5 and 7 0 ka bp during the colder and drier period large detritus free preferentially oriented calcite crystals were deposited from slow moving water as a result of a sharp change in the hydrological regime at 17 ka bp fast moving water started entrainment of the soil and carrying detrital material into the cave and the calcite crystals deposited became small and anhedral coinciding with the petrographic and isotopic changes a sharp drop occurred in the concentration

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

inconsistency between records of δ18o and trace element ratios from stalagmites evidence for increasing mid late holocene moisture in arid central asia the interpretation of trace element calcium ratios of speleothems as indicators of local hydroclimatic variability in the vicinity of caves has led to controversy in reconstructing the evolution of

annual to sub annual resolution of multiple trace element trends in speleothems this study aims to establish evidence for the widespread existence of preserved high resolution trace element variations in speleothems that may have climatic significance ion microprobe analysis of speleothems reveals that annual to sub annual variations in element chemistry exist at five shallow western european cave sites crag cave county kerry and ballynamintra county waterford ireland uamh an tartair sutherland scotland grotte pere noel belgium grotta di ernesto ne italy with widely varying climatic geomorphic and geological settings the variations are not restricted to species mg sr and ba known to substitute directly for ca in the calcite lattice but include h f na and p phosphorus as phosphate displays the greatest variability and may have the most significance as a proxy for the seasonal temperature cycle because of its role as a nutrient element the technique allows estimation of growth rate of speleothems at any interval of interest which is one of several possible uses in palaeoclimatology

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

annual trace element variations in a holocene speleothem high resolution secondary ionization mass spectrometry sims analysis along the growth axis of a holocene speleothem from northern scotland reveals high frequency oscillations and longer term trends in mg ca sr ca and ba ca at the scale of the high frequency oscillations mg ca and sr ca display a well defined anticorrelation while sr ca and ba ca are positively correlated imaging of elemental ratios in two dimensions reveals that the high frequency signal is well preserved and laterally continuous across the sample tims 230th ages and annual ultraviolet luminescence banding provide chronological control and demonstrate that the high frequency cyclicity is annual trace element variations in speleothem calcite are a reflection of hydrochemical processes in the unsaturated zone overlying the cave supply effects and partitioning at the water calcite interface mg partitioning between water and calcite is temperature dependent calculations suggest that the annual mg ca oscillations may be caused by seasonal temperature changes however the longer timescale variations in mg ca are too great to be explained by this mechanism seasonal variations in water residence time in the unsaturated zone which reflect effective precipitation provide a more probable explanation for the observed annual oscillations and also explain the inverse relationship between mg ca and sr ca this record suggests that trace elements in speleothems have the potential to provide the high resolution insights into interannual palaeoclimatic variability required for assessment of general circulation models

variations in atmospheric sulphate recorded in stalagmites by synchrotron micro xrf and xanes analyses abstract we report here the first speleothem time series of the variability of sulphate a species whose abundance in catchments is strongly influenced by atmospheric anthropogenic and volcanic sources annually resolved archives of s mg si and p were generated by applying synchrotron radiation micro x ray fluorescence xrf to two speleothems from different sites in northern italy x ray absorption edge spectrometry proves that the s is in the form of sulphate and xrf mapping demonstrates that s is within calcite and enriched zones are predominantly as layers a post 1850 a d record from the ernesto cave shows a substantial rise in sulphate interpreted as reflecting the largely anthropogenically forced variation of sulphate of the atmospheric boundary layer moderated by some ecosystem storage analysis of the circa 5 2 to circa 5 0 ka interval of a speleothem from savi cave where ecosystem retention of s is likely to have been minimal shows a spiky sulphate record resembling that of ice cores a series of sulphate peaks suggest that multiple volcanic sulphate aerosol emissions at that time this probably enhanced summer temperature cooling thus favouring the preservation of the human mummy of neolithic copper age the iceman on the watershed between italy and austria both examples illustrate the power of speleothems to record atmospheric sulphate variability

accurate trace element analysis of speleothems and biogenic calcium carbonates by la icp ms the high spatial resolution of laser ablation inductively coupled plasma mass spectrometry la icp ms microanalysis of speleothems and biogenic calcium carbonates makes it possible to improve our understanding of past climatic conditions however there are analytical problems associated with this method such as molecular interferences elemental fractionation and mass load dependent matrix effects when using nist silicate reference glasses for calibration our study with a sector field icp ms shows that many masses are affected by interferences such as 24mg by 48ca or 31p by 15n16o elemental fractionation and mass load dependent matrix effects have been detected for both 213 and 193 nm nd yag lasers they are small for refractory lithophile elements in particular for the 193 nm laser 5 for chalcophile siderophile trace elements with low boiling points however these effects are large up to 40 and 20 for the 213 and 193 nm lasers respectively and variable for the nist glasses and carbonates in this paper a protocol for precise and accurate la icp ms analysis of calcium carbonates is established isotopes for interference free measurements at low m m 300 and medium m m 4000 mass resolution have been identified the nist glasses are suitable for calibration of refractory lithophile element concentrations however matrix matched calibration with carbonate reference materials such as usgs macs 1 or macs 3 is necessary for accurate analysis of chalcophile siderophile elements with low boiling points analytical reproducibility rsd is a factor of 2 better using the 193 nm laser than the 213 nm laser as shown by the analysis of macs 1 and macs 3 la icp ms analyses yield results that agree with the reference values within relative uncertainties of ca 5 10 at the 95 confidence level we have applied la icp ms for the determination of trace element concentrations in calcite and aragonite layers of a stalagmite and found large variations for mg zn sr and u in ostracod shells the concentrations of some trace elements e g sr and ba vary significantly indicating the potential for paleoclimate research

evaluating the evidence of a global sea surface temperature threshold for tropical cyclone genesis abstractrecent studies have reaffirmed a global threshold sea surface temperature sst of 26 c for tropical cyclone tc genesis however it is well understood that other thermodynamic variables influence tc genesis and that high sst in isolation is not a sufficient criterion for genesis here a basin by basin analysis of the sst distributions in the five most active ocean basins is performed which shows that there is no global sst threshold for tc genesis the distributions of genesis sst show substantial variations between basins furthermore analysis of the conditional probability of genesis for a given tc season main development region sst suggests that the sst bounds for tc genesis are largely determined by the climatological bounds of the basin and that the sst values within this environmental range have similar probabilities of genesis the distribution of relative sst the difference between local and tropical mean and tropical cyclone potential intensity at tc genesis are more distinct from

paleoenvironmental shifts and precipitation variations recorded in tropical maar lake sediments during the holocene in southern china tropical ocean atmosphere system exerts powerful control on the precipitation variations around the pacific ocean area where interactions among monsoon system intertropical convergence zone itcz migration and other tropical ocean circulations modulate the regional climate changes in centennial scale however little high resolution information is known about the paleoenvironment changes in this area during the holocene in this study a composite sediment profile approximately 16 m in length recovered from shuangchiling scl maar lake in hainan island northern margin of western tropical pacific was selected to investigate the lake level fluctuations net precipitation variations and the influence of the ocean atmosphere system stable isotope 13c 15n analyses total organic carbon toc and total nitrogen tn concentration measurements as well as grain size estimations revealed a two stage evolution scenario for the lake dating back to 9 cal kyr bp the first stage spans a period of tim

anomalous drip in the punkva caves moravian karst relevant implications for paleoclimatic proxies the drips in the punkva caves have been investigated using several methods there was an anomalous drip which differed from regular drips in several parameters including mineralization and isotopic values it has been interpreted as a consequence of prior calcite precipitation above the caves this behavior has implications for the use of speleothems as climatic archives

seasonal trace element and stable isotope variations in a chinese speleothem the potential for high resolution paleomonsoon reconstruction abstract we report the presence of clear annual cycles in trace element mg ca sr ca ba ca and u ca and stable isotope 18o and 13c composition in an annually banded stalagmite from heshang cave hubei province china 30 44 n 110 42 e through a combination of micromilling and in situ analysis la mc icpms we measured geochemical variations across 16 annual growth bands to assess their potential as seasonal resolution paleomonsoon proxies to facilitate comparison with modern climatic and environmental data we created composite annual cycles for each proxy by stacking 6 well defined years speleothem 18o variations 10 8 to 8 5 are controlled by seasonal variations in temperature and drip water 18o which lead to maximum values during may around the time of summer monsoon onset this provides a chronological marker which can be used to constrain the timing of the other geochemical cycles the composite cycles reveal a strong positive correlation between mg ca sr ca ba ca and 13c values in the micromilled section r2 0 65 0 98 with minimum values occurring around may maximum u ca values occur at the same time we present simple models which show that these correlations as well as the observed ranges of mg ca 14 1 to 22 4 mmol mol sr ca 0 2 to 0 4 mmol mol and 13c 12 5 to 10 7 may be fully explained by progressive co2 degassing and calcite precipitation from an initially saturated solution using realistic initial conditions for heshang cave t 18 c mg casolution 0 84 mol mol sr casolution 0 69 mmol mol 13ctdic 16 75 we find that the observed relationships can be produced by using dmg 0 016 and dsr 0 30 within the range of expected values the model suggests that the fraction of ca removed from the solution ranges from 0 to 30 to produce the observed seasonal cycles this variation may be due to two related processes which occur during drier periods 1 increased prior precipitation of calcite in the epikarst or on the cave ceiling and or 2 a greater degree of co2 degassing and calcite precipitation on stalagmite surfaces when drip rates are lower both mechanisms would have the effect of enriching speleothem mg ca sr ca ba ca and 13c values during drier periods past variations in heshang carbonate chemistry may therefore be useful as seasonal resolution proxies for past rainfall

crystal growth rate effect on mg ca and sr ca partitioning between calcite and fluid an in situ approach abstract partition coefficients of mg and sr kmg and ksr between calcite and fluid were determined in crystals grown under different rates v where v is defined as the crystal extension per unit of time nm s addition of rare earth elements ree into the fluid leads to ree preservation in the calcite this preservation allows for a direct determination of the values of v by measuring the widths of the ree spiked zones the edge to edge spot analyses of mg ca sr ca and ree ca in the individual crystals were conducted using secondary ion mass spectrometry sims the mg ca and sr ca ratios in the fluids from which calcites precipitated were also measured with inductively coupled plasma atomic emission spectroscopy icp oes this allowed for the first time to evaluate kmg in situ in the individual crystals without averaging the data from the multiple calcite crystals results show that ksr increases by a factor of six with increasing calcite growth rate from 0 001 to 4 nm s kmg decreases by a factor of three with the same increase of v values these ksr and kmg behaviors were described quantitatively using a growth entrapment model gem according to the gem simulations sr is enriched and mg is depleted in the near surface layer of calcite relative to the bulk lattice this distinct outermost region of the crystal may be fully or partially captured by its lattice during rapid growth this process causes disequilibrium partitioning of sr and mg through growth entrapment

evidence of rainfall variations in southern brazil from trace element ratios mg ca and sr ca in a late pleistocene stalagmite trace element ratios in the bt2 stalagmite from botuveracave southern brazil are explored as a proxy for changes in the local rainfall recharge during the last 116 ky bp mg ca and sr ca ratios measured with an electron microprobe are signif icantly positively correlated with one another throughout the entire record and vary in a way that is very consistent with variations of d 18 o in the same speleothem during the last glacial period we suggest that prior calcite precipitation in the vadose zone of the cave system is the main factor affecting the incorporation of mg and sr into calcite of the stalagmite this interpretation is supported by trace element correlation patterns and by results from a hydrochemistry study performed in a cave located in the same region and in a similar environmental setting therefore we conclude that higher lower mg ca and sr ca values are associated with lower higher levels of recharge into the karstic aquifer as such conditions lead to an increase decrease in the volume of calcite precipitated in the unsaturated zone above the cave during dry wet climate periods trace element variations point to generally dryer wetter conditions during lower high phases of summer insolation in the southern hemisphere these periods coincide with decreased increased activity of the south american summer monsoon as revealed by d 18 o stalagmite records in addition trace element variations show that rather wet conditions persisted through out most of the last glacial period from approximately 70 to 17 ky bp we suggest that during this period the glacial boundary conditions especially ice volume buildup in the northern hemisphere played an important role for monsoon rainfall inten sification in the region 2007 elsevier ltd all rights reserved

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

palaeoclimate determination from cave calcite deposits calcite deposits formed in limestone caves have been found to be an excellent repository of palaeoclimatic data for terrestrial environments the very presence of a relict deposit indicates non glacial conditions at the time of formation and both 14c and uranium series methods can be used to date the deposit and hence the age of these climatic conditions variations in 13c and 18o content of the calcite in 2h and 18o content of fluid inclusions in trace element concentrations and more recently in pollen assemblages trapped in the calcite are all potentially available as synchronous palaeoclimatic indicators previous work has tended to concentrate mainly on abundance of deposits as a palaeoclimatic indicator for the last 300 000 years this literature is briefly reviewed here together with the theory and methods of analysis of the u series and stable isotopic techniques the combined use of u series ages and 13c and 18o variations in cave calcites illustrates the potential for palaeoclimate determination previously unpublished results of stable isotopic variations in dated calcites from caves in northern england indicate the level of detail of stable isotopic variations and time resolution that can be obtained and the complexity of interpretation that may arise tentative palaeoclimatic signals for the periods 90 125 ka and 170 300 ka are presented more comprehensive studies are needed in future work especially in view of the difficulty in obtaining suitable deposits and the ethics of cave deposits conservation