climatic dependence of stable carbon and oxygen isotope signals recorded in speleothems from soil water to speleothem calcite abstract understanding the relationship between stable isotope signals recorded in speleothems 13 c and 18 o and the isotopic composition of the carbonate species in the soil water is of great importance for their interpretation in terms of past climate variability here the evolution of the carbon isotope composition of soil water on its way down to the cave during dissolution of limestone is studied for both closed and open closed conditions with respect to co 2 the water entering the cave flows as a thin film towards the drip site co 2 degasses from this film within approx 10 s by molecular diffusion subsequently chemical and isotopic equilibrium is established on a time scale of several 10 100 s the 13 c value of the drip water is mainly determined by the isotopic composition of soil co 2 the evolution of the 18 o value of the carbonate species is determined by the long exchange time t ex between oxygen in carbonate and water of several 10 000 s even if the oxygen of the co 2 in soil water is in isotopic equilibrium with that of the water dissolution of limestone delivers oxygen with a different isotopic composition changing the 18 o value of the carbonate species consequently the 18 o value of the rainwater will only be reflected in the drip water if it has stayed in the rock for a sufficiently long time after the water has entered the cave the carbon and oxygen isotope composition of the drip water may be altered by co 2 exchange with the cave air exchange times ex co 2 of about 3000 s are derived thus only drip water which drips in less than 3000 s onto the stalagmite surface is suitable to imprint climatic signals into speleothem calcite deposited from it precipitation of calcite proceeds with time constants p of several 100 s different rate constants and equilibrium concentrations for the heavy and light isotopes respectively result in isotope fractionation during calcite precipitation since t ex p exchange with the oxygen in the water can be neglected and the isotopic evolution of carbon and oxygen proceed analogously for drip intervals t d p the isotopic compositions of both carbon and oxygen in the solution evolve linearly in time the calcite precipitated at the apex of the stalagmite reflects the isotopic signal of the drip water for long drip intervals when calcite is deposited from a stagnant water film long drip intervals may have a significant effect on the isotopic composition of the dic in this case the isotopic composition of the calcite deposited at the apex must be determined by averaging over the drip interval such processes must be considered when speleothems are used as proxies of past climate variability

variations in the discharge and organic matter content of stalagmite drip waters in lower cave bristol six drip waters which were actively depositing stalagmites in lower cave bristol were analysed both for discharge and luminescence properties drip discharges were determined for two different years and show a complex response to surface precipitation variations inter annual variability in drip discharge is demonstrated to be significantly higher than intra annual variability and discharge was demonstrated both to increase and decrease non linearly with increased precipitation drip waters demonstrate a correlation between their luminescence intensity and drip discharge with increased luminescence in winter as more organic matter is flushed through the aquifer the strength of the relationship between luminescence intensity and discharge increases with increased discharge the results presented here have implications for the palaeoenvironmental interpretation of annual growth laminae and the growth rates of stalagmite samples 1997 john wiley sons ltd

calibration of the calcite water oxygen isotope geothermometer at devils hole nevada a natural laboratory abstract the 18 o of ground water 13 54 0 05 and inorganically precipitated holocene vein calcite 14 56 0 03 from devils hole cave 2 in southcentral nevada yield an oxygen isotopic fractionation factor between calcite and water at 33 7 c of 1 02849 0 00013 1000 ln calcite water 28 09 0 13 using the commonly accepted value of calcite water t of 0 00020 k 1 this corresponds to a 1000 ln calcite water value at 25 c of 29 80 which differs substantially from the current accepted value of 28 3 use of previously published oxygen isotopic fractionation factors would yield a calcite precipitation temperature in devils hole that is 8 c lower than the measured ground water temperature alternatively previously published fractionation factors would yield a 18 o of water from which the calcite precipitated that is too negative by 1 5 using a temperature of 33 7 c several lines of evidence indicate that the geochemical environment of devils hole has been remarkably constant for at least 10 ka accordingly a re evaluation of calcite water oxygen isotopic fractionation factor may be in order assuming the devils hole oxygen isotopic value of calcite water represents thermodynamic equilibrium many marine carbonates are precipitated with a 18 o value that is too low apparently due to a kinetic isotopic fractionation that preferentially enriches 16 o in the solid carbonate over 18 o feigning oxygen isotopic equilibrium

carbon and oxygen isotope study of the active water carbonate system in a karstic mediterranean cave implications for paleoclimate research in semiarid regions abstract in a semiarid climatic zone such as the eastern mediterranean region annual rainfall variations and fractionation processes in the epikarst zone exert a profound influence on the isotopic compositions of waters seeping into a cave consequently the isotopic compositions of speleothems depositing from cave waters may show complex variations that need to be understood if they are to be exploited for paleoclimate studies this is confirmed by a four year study of the active carbonate water system in the soreq cave israel the 18o smow values of cave waters range from 6 3 to 3 5 the highest 18o values occur at the end of the dry season in waters dripping from stalactites and reflect evaporation processes in the epikarst zone whereas the lowest values occur in rapidly dripping fast drip waters at the peak of the rainy seasons however even fast drip waters are about 1 5 heavier than the rainfall above the cave which is taken to reflect the mixing of fresh with residual evaporated water in the epikarst zone 13c pdb values of dissolved inorganic carbon dic vary from 15 6 to 5 4 with fast drip waters having lower 13c values mostly 15 6 to 12 and higher dic concentrations relative to pool and stalactite drip water the low 13c values of fast drip waters and their supersaturation with respect to calcium carbonate indicates that the seepage waters have dissolved both soil co2 derived from overlying c3 type vegetation and marine dolomite host rock the 18o pdb values of various types of present day low magnesium calcite lmc speleothems range from 6 5 to 4 3 and 13c values from 13 to 5 5 and are not correlated with speleothem type an analysis of 18o values of present day calcite rafts and pool waters shows that they form in oxygen isotope equilibrium similarly the measured ranges of 13c and 18o values for all types of present day speleothems are consistent with equilibrium deposition at cave temperatures the 13c 18o range of contemporary lmc thus reflects the variations in temperatures and isotopic compositions of the presentday cave waters the 10 variation in the 13c values in waters can be modeled by a simple rayleigh calculation of the carbon isotope fractionation accompanying co2 degassing and carbonate precipitation these variations may obscure the differences in the carbon isotopic composition of speleothems that could arise when vegetation cover changes from c3 to c4 type plants this consideration emphasizes that it is necessary to characterize the full range of 13c values associated with contemporaneous speleothems in order to clarify the effects of degassing from those due to differing vegetation types isotopic studies of a number of different types of fossil lmc speleothems show many of them to exhibit isotopic trends that are similar to those of present day lmc but others show both higher and lower 18o ranges in particular the higher 18o range has been shown by independent age measurements to be associated with a period of drier conditions the results of the study thus indicate that it is necessary to work on a well calibrated cave system in semiarid climates and that the fossil speleothem record should be obtained from different types of contemporaneous deposit in order to fully characterize the 18o 13c range representative of any given climatic period

seasonal isotopic variability of precipitation and cave drip water at indian oven cave new york a major assumption in palaeoclimatic studies using speleothems is that cave seepage waters are homogenized as they pass through the bedrock so that they record the average annual isotopic signal of precipitation a year long study during 2001 02 was conducted at indian oven cave in eastern new york state usa to investigate how cave seepage water isotopic signals relate to those of precipitation samples were collected biweekly and analysed for stable isotopes of oxygen and hydrogen our study shows that for this cave homogenization did not occur as seepage waters had the same seasonal variability as precipitation however mean seepage water isotopic values were very close to those of the mean values for precipitation rapid flow through times of seepage water show that the speleothems can record climate conditions above the cave contemporaneously at one location flow ceased during the winter therefore isotopes measured in cave drip waters reflected only the enriched summer isotopes under certain circumstances the analysis of calcite sampled from those drip waters may then lead to a false conclusion of a warming during that period instead of the fact that it was merely a drier winter period copyright 2005 john wiley sons ltd

directional spectra of hurricane generated waves in the gulf of mexico 1 hurricane induced directional wave spectra in the gulf of mexico are investigated based on the measurements collected at 12 buoys during 7 hurricane events in recent years focusing on hurricane generated wave spectra we only consider the wave measurements at the buoys within eight times the radius of the hurricane maximum wind speed rmax from the hurricane center a series of numerical experiments using a third generation spectral wave prediction model were carried out to gain insight into the mechanism controlling the directional and frequency distributions of hurricane wave energy it is found that hurricane wave spectra are almost swell dominated except for the right rear quadrant of a hurricane with respect to the forward direction where the local strong winds control the spectra despite the complexity of a hurricane wind field most of the spectra are mono modal similar to those under fetch limited unidirectional winds however bi modal spectra were also found in both measurements and model results four types of bi modal spectra have been observed type i happens far away 6 rmax from a hurricane type ii is bi modal in frequency with significant differences in direction it happens in the two left quadrants when the direction of hurricane winds deviates considerably from the swell direction type iii is bi modal in frequency in almost the same wave direction with two close peaks it occurs when the energy of locally generated wind sea is only partially transferred to the swell energy by non linear wave wave interactions type iv was observed in shallow waters owing to coastal effects

disequilibrium carbon and oxygen isotope fractionation in recent cave calcite comparison of cave precipitates and model data abstract speleothem proxy data provide important information in continental palaeo climate research due to their precise chronology and wide geographic distribution despite a continuously growing number of field and numerical studies designed to study stable isotope fractionation effects many aspects remain a matter of debate here carbon and oxygen isotope ratios from cave drip water and calcite precipitates sampled on watch glasses in the bunker cave western germany are compared with the values expected for isotopic equilibrium furthermore the field data are compared with the results of a numerical model simulating stalagmite growth and stable isotope ratios two drip sites with different drip rates were investigated drip site ts 1 is characterised by a high drip rate and drip water of this site is characterised by a high saturation index with respect to calcite ts 1 shows no evidence of prior calcite precipitation conversely drip site ts 8 shows a low drip rate and drip water from this site is characterised by a low saturation index ts 8 shows evidence of prior calcite precipitation whereas the mean 13 c dic values of the drip water are significantly different between the two drip sites the mean 18 o drip water values are similar calcite precipitation rates are higher at watch glass site u i corresponding to drip site ts 1 this is probably due to the higher si calcite and drip rate the 18 o and 13 c values of the calcite precipitated on watch glasses u iv corresponding to drip site ts 8 are significantly higher than those of the calcite collected on watch glasses u i calcite precipitation occurs close to isotopic equilibrium at watch glass site u i whereas the calcite precipitated at watch glass site u iv shows clear evidence of isotopic disequilibrium the results suggest that cave calcites precipitated at lower drip rates have higher 13 c and 18 o values than predicted by equilibrium precipitation furthermore our data show that stalagmites from the same cave which are fed by drip water with similar 18 o values may have different 18 o calcite values the 13 c and 18 o values predicted by the numerical model are generally lower by 1 9 and 0 8 respectively than those of the natural cave calcite nevertheless the first order trends observed in the cave data are well reproduced by the model the offset between cave and model data is probably due to the fractionation factors used in the model

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

hydrogeochemistry and fractionation pathways of mg isotopes in a continental weathering system lessons from field experiments abstract the potential of magnesium isotope records from cave carbonate archives speleothems has been documented but remains underexplored this is due to the limited knowledge regarding the complex suite of physico chemical and biological disequilibrium fractionation processes affecting meteoric fluids in the soil zone the carbonate hostrock and calcite precipitation in the cave this study presents 26 mg data from a monitored cave in germany bunker cave including rain water 26 mg 0 70 0 14 soil water 26 mg 0 51 0 10 and drip waters 26 mg 1 65 0 08 sampled between november 2009 and may 2011 field precipitation experiments i e calcite precipitated on watch glasses 26 mg 3 56 0 26 may 2006 to june 2010 were found to be of limited use this is because of experimental crystallographic and sampling artefacts conversely variations in soil and drip water 26 mg over time are predominantly related to seasonal variations in water availability and air temperature affecting the subtle weathering ratio between mg bearing clay minerals in the soil here mainly chlorite and montmorillonite and the low mg calcite hostrock bunker cave 26 mg drip water values display a significant dependency on the air temperature outside the cave this is because air temperature influences co 2 levels in the soil and hence rock water interaction for fast drip sites the direct correlation of 26 mg soil water and 26 mg drip water documents a relative short residence time of the fluid in the carbonate aquifer and thus limited isotope equilibration and mixing of different reservoirs this result is encouraging and adds new evidence to the poorly understood hydro geochemistry of carbonate aquifers slow seepage flow drip sites display an annual 26 mg drip water pattern that is geochemically unrelated to that of the soil water further research including laboratory experiments must focus on the complex fractionation between drip water and speleothem calcite mg isotope record

a paleoclimate record of the last 17 600 years in stalagmites from the b7 cave sauerland germany abstract petrographical and geochemical parameters of stalagmites from the b7 cave in iserlohn letmathe northern rhenish massif nw germany record late and postglacial climate changes temperature and or precipitation fabrics and microfacies of the stalagmite profiles lead to a differentiation of four hierarchies of rhythms clastic layers in the stalagmites are caused by flooding events and are time markers twenty four tims th u age dates provide a time calibration of stalagmite growth phases one stalagmite reveals an early growth period between 17 6 and 16 7 ka bp between 9 6 and 5 5 ka bp atlantic episode of the holocene the growth rate of the stalagmites was higher than before and after this time with dominant light porous microfacial laminae and high 18 o and 13 c values representing partly kinetic fractionation effects this part of the holocene is interpreted as a mainly warm episode with frequent interruptions of dripping within the past 4 ka the profiles with predominant dark compact facies reveal low isotopic values which may be interpreted as a temperature proxy record the stalagmite records resemble records from an irish stalagmite correlation with the 14 c record from european tree rings suggests that colder periods in the north atlantic were accompanied by drier winters in central europe

modelling fractionation of stable isotopes in stalagmites abstract high resolution 13c and 18o profiles recorded in precisely dated speleothems are widely used proxies for the climate of the past both 13c and 18o depend on several climate related effects including meteorological processes processes occurring in the soil zone above the cave and isotope fractionation processes occurring in the solution layer on the stalagmite surface here we model the latter using a stalagmite isotope and growth model and determine the relationship between the stable isotope values in speleothem calcite and cave parameters such as temperature drip interval water p co 2 and a mixing coefficient describing mixing processes between the solution layer and the impinging drop the evolution of 13c values is modelled as a rayleigh distillation process and shows a pronounced dependence on the residence time of the solution on the stalagmite surface and the drip interval respectively the evolution of 18o values in contrast is also influenced by buffering reactions between the bicarbonate in the solution and the drip water driving the 18o value of the bicarbonate towards the value expected for equilibrium isotope fractionation between drip water and calcite this attenuates the dependence of the 18o values on drip interval the temperature dependence of 18o however is more pronounced than for 13c and in a similar range as expected for fractionation under equilibrium conditions we also investigate the isotopic enrichment of the 13c and 18o values along individual growth layers and thus the slopes expected for hendy tests the results show that a positive hendy test is only possible if isotope fractionation occurred under disequilibrium conditions however a negative hendy test does not exclude that isotope fractionation occurred under disequilibrium conditions a more reliable indicator for disequilibrium fractionation is the enrichment of the 13c values along an individual growth layer

isotope disequilibrium effects the influence of evaporation and ventilation effects on the carbon and oxygen isotope composition of speleothems a model approach abstract in order to improve the understanding of variations of speleothem 18o and 13c values in the context of palaeoclimate research it is important to quantify the isotope fractionation processes influencing the 18o and 13c values of stalagmites here we present an extended version of speleothem stable isotope model that accounts for evaporation and condensation effects during precipitation of calcite the isolution model allows to calculate the effect of evaporation on 18ocalcite and 13ccalcite values in dependence on relative humidity and wind velocity our results reveal that evaporation may have a significant effect on 18ocalcite and 13ccalcite due to the loss of h2o from the solution layer and the related increase of the ca2 concentration this leads to higher precipitation rates and consequently larger isotope fractionation effects the effect on speleothem 18ocalcite and 13ccalcite can be as high as changes caused by variations of temperature drip interval pco2 drip and pco2 cave furthermore the change of pco2 cave due to ventilation effects may also affect speleothem 18ocalcite and 13ccalcite values because of the effect of pco2 cave on the equilibrium concentrations of the co2 h2o caco3 system and thus the calcite precipitation rate the variability of other cave parameters temperature drip interval pco2 drip pco2 cave can have a comparable effect on 18ocalcite and 13ccalcite values depending on the magnitude of variability we validated the isolution model by modelling the 18ocalcite values from a cave analogue experiment and successfully reproduced the values for high temperatures

seasonal variation of martian middle atmosphere tides observed by the mars climate sounder the increased local time coverage retrieved from the mars climate sounder on board the mars reconnaissance orbiter enables the direct extraction of thermal tides in the mars middle atmosphere using temperature profiles from mars years 30 to 32 we studied the latitudinal and seasonal variations in the tides and stationary planetary waves with zonal wave numbers s 1 3 the amplitude of the migrating diurnal tide exhibits strong semiannual variations in both the equatorial region and the middle latitudes of southern hemisphere the migrating semidiurnal tide sw2 shows clear semiannual variations in the equatorial region and the middle latitudes of northern hemisphere but an annual variation in the southern hemisphere the spatial and temporal correlations between the sw2 amplitude and the density scaled opacity of both the water ice and dust in the equatorial region may provide a possible explanation for the tidal forcing of sw2 three kelvin modes with zonal wave numbers 1 3 de1 de3 have significant seasonal variations in the equatorial region de1 appears to have a semiannual variation whereas de2 and de3 have clear annual variations herein for the first time we have extracted the westward propagating diurnal tide with s 2 and 3 and semidiurnal tide with s 1 in the mars middle atmosphere using observational data all three waves have asymmetric latitudinal distributions which should correspond to their possible excitation source i e nonlinear interactions between stationary planetary waves and migrating tides

oxygen isotopic fractionation between drip water and speleothem calcite a 10 year monitoring study central texas usa abstract speleothem 18o values can serve as a paleoclimate proxy yielding information about past temperature and rainfall an accurate determination of the equilibrium calcite water oxygen isotopic fractionation factor and an assessment of kinetic isotopic fractionation are required for interpretation of speleothem 18o data in this study 18o values were measured for calcite deposited on artificial substrates at four sites in two central texas caves monitored for over 10 years the results are used to evaluate the equilibrium isotopic fractionation factor and the impact of climatic and hydrologic conditions on kinetic isotopic fractionation the 18o values of calcite from the four sites ranged from 24 8 to 26 7 v smow and associated drip water values ranged from 4 6 to 3 9 a comparison of predicted equilibrium calcite 18o values calculated using a commonly used isotopic fractionation factor with measured values indicates that 94 of the calcite samples are not in oxygen isotopic equilibrium with respect to their associated drip water the departure from oxygen isotopic equilibrium expressed as 18occ e ranges from 0 7 to 1 4 three of the four drip sites yield similar linear relationships between 18occ e and water temperature tw and can be collectively expressed as 18occ e 0 3tw 4 7 r2 0 56 n 93 therefore calcite deposited during time periods of lower tw lower cave air co2 concentration and faster calcite deposition rates have 18o values closer to equilibrium this contradicts conceptual models which predict that a faster calcite deposition rate leads to a larger departure of calcite 18o from equilibrium if slower calcite deposition indeed facilitates equilibrium fractionation i e 18occ e 0 then the results of this study support a larger than commonly accepted value for the equilibrium calcite water oxygen isotopic fractionation factor adopting a larger published value for the fractionation factor yields negative 18occ e values of up to 2 4 these negative values cannot be explained by existing kinetic fractionation models alternatively they may reflect the trapping of a calcite surface layer with a lower 18o value than that of calcite in isotopic equilibrium with ambient water the relationship between deposition rates and 18occ e for this study is consistent with the same relationship using data for synthetic calcite from the literature this relationship indicates a 0 8 shift of calcite 18o for every ten fold increase in deposition rate at 5 to 25 c and a ph of 8 3 the significant kinetic fractionation observed in this study warrant consideration in applying measured speleothem calcite 18o values to interpret past climate conditions

monitoring bunker cave nw germany a prerequisite to interpret geochemical proxy data of speleothems from this site summary monitoring cave environments is important to understand processes in karst systems if stalagmites from a specific cave are used as archives of past climate variability a quantitative understanding of the soil karst speleothem system is crucial the monitoring program performed in bunker cave nw germany which includes monthly collection of climatological data as well as air and water samples from the cave and the overlying soil since 2006 is a prerequisite for the interpretation of speleothem data from the cave in terms of climate variability the results show that bunker cave is a homogeneously ventilated cave with rather low pco2 values of 580 1200 ppmv which lacks strong seasonal variations the 18o value of cave drip water reflects the mean annual composition of the rain water and the seasonal variability is strongly attenuated indicating a well mixed karst aquifer hence stalagmites from bunker cave should be well suited to record interannual decadal climate trends seven drip sites in two cave chambers show three different types of discharge behaviour including slow seasonal drip fast seasonal drip and seepage flow the drip rate patterns of most drip sites are consistent with the main infiltration events taking into account a delay of several months an instantaneous response to precipitation i e piston flow is not observed for any drip site indicating a specific water capacity threshold in the soil karst aquifer prior calcite precipitation pcp was also identified especially during times of low discharge though pcp is not as pronounced at bunker cave as in other caves it probably has an influence on the mg ca ratios of the stalagmites

modelling carbon isotopes of carbonates in cave drip water abstract c isotopes in cave drip water are affected by both the c isotope composition of soil air and host rock carbonate furthermore the c isotope composition of cave drip water strongly depends on the calcite dissolution system i e open closed and intermediate conditions here we present a calcite dissolution model which calculates the 14c activity and 13c value of the dissolved inorganic carbon of the drip water the model is based on the chemical equations describing calcite dissolution h 2 o caco 3 co 2 ca 2 2hco 3 the most important improvement relative to previous models is the combination of the open and closed system conditions in order to simulate the c isotope composition during intermediate states of calcite dissolution and the application to carbon isotope measurements on cave drip waters from grotta di ernesto italy the major changes in the c isotope composition of the drip water occur in response to variations in the open closed system ratio additionally the 14c activity and the 13c value of the drip water depend on changes in the partial pressure of soil co2 radiocarbon and 13c values of the grotta di ernesto drip water are well reproduced by the model

carbon mass balance modelling and carbon isotope exchange processes in dynamic caves abstract diverse interpretations have been made of carbon isotope time series in speleothems reflecting multiple potential controls here we study the dynamics of 13 c and 12 c cycling in a particularly well constrained site to improve our understanding of processes affecting speleothem 13 c values the small tubular grotta di ernesto cave ne italy hosts annually laminated speleothem archives of climatic and environmental changes temperature air pressure pco 2 dissolved inorganic carbon dic and their c isotopic compositions were monitored for up to five years in soil water and gas cave dripwater and cave air mass balance models were constructed for co 2 concentrations and tested against the carbon isotope data air advection forces winter pco 2 to drop in the cave air to ca 500 ppm from a summer peak of ca 1500 ppm with a rate of air exchange between cave and free atmosphere of approximately 0 4 days the process of cave ventilation forces degassing of co 2 from the dripwater prior to any calcite precipitation onto the stalagmites this phase of degassing causes kinetic isotope fractionation i e 13 c enrichment of dripwater whose 13 c dic values are already higher by about 1 than those of soil water due to dissolution of the carbonate rock a subsequent systematic shift to even higher 13 c values from 11 5 in the cave drips to about 8 calculated for the solution film on top of stalagmites is related to degassing on the stalagmite top and equilibration with the cave air mass balance modelling of c fluxes reveals that a very small percentage of isotopically depleted cave air co 2 evolves from the first phase of dripwater degassing and shifts the winter cave air composition toward slightly more depleted values than those calculated for equilibrium the systematic 13 c enrichment from the soil to the stalagmites at grotta di ernesto is independent of drip rate and forced by the difference in pco 2 between cave water and cave air this implies that speleothem 13 c values may not be simply interpreted either in terms of hydrology or soil processes

climate and cave control on pleistocene holocene calcite to aragonite transitions in speleothems from morocco elemental and isotopic evidence the occurrence of aragonite in speleothems has commonly been related to high dripwater mg ca ratios because mg is known to be a growth inhibitor for calcite laboratory aragonite precipitation experiments however suggested a more complex array of controlling factors here we present data from pleistocene to holocene speleothems collected from both a dolostone and a limestone cave in northern morocco these stalagmites exhibit both lateral and stratigraphic calcite to aragonite transitions aragonite fabrics are well preserved and represent primary features in order to shed light on the factors that control alternating calcite and aragonite precipitation elemental mg sr ba u p y pb al ti and th abundances were measured using la icp ms and analysed with principal component analysis samples were analyzed at 100 200 m resolution across stratigraphic and lateral transitions carbon and oxygen isotope ratios were analysed at 100 m resolution covering stratigraphic calcite to aragonite transitions results show that the precipitation of aragonite was driven by a decrease in effective rainfall which enhanced prior calcite precipitation different geochemical patterns are observed between calcite and aragonite when comparing data from the grotte de piste and grotte prison de chien this may be explained by the increased dripwater mg ca ratio and enhanced prior aragonite precipitation in the dolostone cave versus lower dripwater mg ca ratio and prior calcite precipitation in the limestone cave a full understanding for the presence of lateral calcite to aragonite transitions is not reached trace elemental analysis however does suggest that different crystallographic parameters ionic radius amount of crystal defect sites adsorption potential may have a direct effect on the incorporation of sr mg ba al ti th and possibly y and p

magnesium isotope fractionation during low mg calcite precipitation in a limestone cave field study and experiments abstract the chemical and isotopic composition of speleothem calcite and particularly that of stalagmites and flowstones is increasingly exploited as an archive of past environmental change in continental settings despite intensive research including modelling and novel approaches speleothem data remain difficult to interpret a possible way foreword is to apply a multi proxy approach including non conventional isotope systems for the first time we here present a complete analytical dataset of magnesium isotopes 26 mg from a monitored cave in nw germany bunker cave the data set includes 26 mg values of loess derived soil above the cave 1 0 0 5 soil water 1 2 0 5 the carbonate hostrock 3 8 0 5 dripwater in the cave 1 8 0 2 speleothem low mg calcite stalactites stalagmites 4 3 0 6 cave loam 0 6 0 1 and runoff water 1 8 0 1 in the cave respectively magnesium isotope fractionation processes during weathering and interaction between soil cover hostrock and solute bearing soil water are non trivial and depend on a number of variables including solution residence times dissolution rates adsorption effects and potential neo formation of solids in the regolith and the carbonate aquifer apparent mg isotope fractionation between dripwater and speleothem low mg calcite is about 1000ln mg cc mg aq 2 4 a similar mg isotope fractionation 1000ln mg cc mg aq 2 1 is obtained by abiogenic precipitation experiments carried out at aqueous mg ca ratios and temperatures close to cave conditions accordingly 26 mg discrimination during low mg calcite formation in caves is highly related to inorganic fractionation effects which may comprise dehydration of mg 2 prior to incorporation into calcite surface entrapment of light isotopes and reaction kinetics relevance of kinetics is supported by a significant negative correlation of mg isotope fractionation with the precipitation rate for inorganic precipitation experiments

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

modelling the δ18o value of cave drip water and speleothem calcite abstract stable isotope signals recorded in speleothems have provided important insights about past climate variability in recent years quantitative reconstruction of mean annual temperature and the amount of precipitation however remains difficult because the stable isotope signals are influenced by various processes here we present a drip water model which shows how these climate parameters affect the oxygen isotope signal of cave drip water in the model the dependence of the 18 o value of drip water on mean annual temperature is established by correlation to the amount of winter precipitation and winter temperature application of the model to two caves in western germany reveals a strong influence of winter rainfall on the oxygen isotope composition of cave drip water in this region assuming equilibrium isotope fractionation between drip water and calcite we provide a function relating the 18 o value of speleothem calcite to mean annual surface temperature this function shows a clear anticorrelation between temperature and the 18 o value of speleothem calcite which has been previously reported for several caves in central and northern europe by inverse application of this function we tentatively reconstruct average temperatures for the period between 6 and 1 5 ka from the 18 o signals of two stalagmites from atta and bunker cave western germany the resulting temperature curves are very sensitive to the value used for the correlation between the amount of winter precipitation and winter temperature since this correlation was probably not constant in the past the reconstructed temperature curves are associated with substantial uncertainty

controls on dissolved inorganic carbon and δ13c in cave waters from desoto caverns implications for speleothem δ13c assessments abstract unraveling the factors controlling the carbon chemistry and transport of carbon within extant karst systems has important implications concerning the assessment of time series 13c records of speleothems here we report the results of a 3 year study of total dissolved inorganic carbon dic and 13cdic from cave waters at desoto caverns southeastern usa that offer valuable insight on carbon transport and the accompanied isotope fractionations from end member sources to speleothems dic and 13cdic values of cave waters range from 0 2 to 6 0 mm and 2 7 to 12 9 vpdb respectively dic and 13cdic of seasonal drips show seasonal albeit noisy variability and are inversely related 13cdic 2 49 dic 0 64 r2 0 84 a shallow pool fed by multiple drips shows a bimodal 13cdic distribution with an isotopically heavier mode during winter 4 to 5 vpdb relative to summer months 9 to 10 vpdb a multi year trend of decreasing water availability during the study period is not reflected in a response of cave water carbon chemistry suggesting that rainfall amount may not be a significant controlling factor of the carbon chemistry coupled cave air winter ventilation summer stagnation and varying co2 fluxes through the soil horizon and epikarst exert the strongest influence on seasonal dic and 13cdic variability measured values of high dic and low 13cdic from cave waters collected during the summer early fall closely approximate isotopic equilibrium conditions conversely low dic and high 13cdic values during winter early months indicate kinetically enhanced isotopic fractionations within the cave waters the kinetically enhanced isotopic fractionation of hco 3 partitioned between degassed co2 and precipitated caco3 1000 ln co 2 hco 3 caco 3 ar hco 3 2 is greater by about a factor of two 6 7 0 3 relative to the same isotopic fractionation under equilibrium conditions 3 1 on the basis of 14c mass balance and paired 14c u th measurements we estimate that on average about 23 of c delivered annually by the drips to the aragonite stalagmites is derived from 14c dead dolomite cap while the remainder of 77 is derived from 14c live biomass 13c measurements of aragonite n 12 sampled from the tips of active speleothems during the summer months are consistent with theoretical aragonite 13c values calculated using the shallow pool summer early fall data thus confirming the 13c seasonality in both drips and coeval aragonite 13c values of an active stalagmite section spanning the last 200 years show a normal distribution with a mean of 7 1 1 2 n 81 and a mode of 7 to 8 that are statistically indistinguishable from the annual mean and mode of all dripwaters thus secular time series 13c records of stalagmites at desoto caverns with resolving power 10 1 year will likely carry the imprints of drip annual means that record climate driven 13c seasonal biases

seasonal variations in modern speleothem calcite growth in central texas u s a variations in growth rates of speleothem calcite have been hypothesized to reflect changes in a range of paleoenvironmental variables including atmospheric temperature and precipitation drip water composition and the rate of soil co2 delivery to the subsurface to test these hypotheses we quantified growth rates of modern speleothem calcite on artificial substrates and monitored concurrent environmental conditions in three caves across the edwards plateau in central texas within each of two caves different drip sites exhibit similar annual cycles in calcite growth rates even though there are large differences between the mean growth rates at the sites the growth rate cycles inversely correlate to seasonal changes in regional air temperature outside the caves with near zero growth rates during the warmest summer months and peak growth rates in fall through spring drip sites from caves 130 km apart exhibit similar temporal patterns in calcite growth rate indicating a controlling mechanism on at least this distance the seasonal variations in calcite growth rate can be accounted for by a primary control by regional temperature effects on ventilation of cave air co2 concentrations and or drip water co2 contents in contrast site to site differences in the magnitude of calcite growth rates within an individual cave appear to be controlled principally by differences in drip rate a secondary control by drip rate on the growth rate temporal variations is suggested by interannual variations no calcite growth was observed in the third cave which has relatively high values of and small seasonal changes in cave air co2 these results indicate that growth rate variations in ancient speleothems may serve as a paleoenvironmental proxy with seasonal resolution by applying this approach of monitoring the modern system speleothem growth rate and geochemical proxies for paleoenvironmental change may be evaluated and calibrated

investigation of the stable isotope fractionation in speleothems with laboratory experiments many speleothems show evidence for calcite precipitation under disequilibrium conditions to improve the understanding of these kinetic processes several laboratory experiments were performed to study the fractionation of stable oxygen and carbon isotopes during the precipitation of calcite carbonate was precipitated under controlled conditions from both a body of standing water beaker experiments and a solution flowing along a channel channel experiments at a relative humidity of 100 slow degassing of co2 simulated by the beaker experiments results in 18o values in equilibrium with the solution in contrast the 13c values show a significant enrichment inversely proportional to the height of the solution in the beakers fast degassing of co2 simulated by the channel experiments showed an enrichment of both 13c and 18o and a slope of 13c 18o of 1 4 0 6 these results represent experimental evidence for the hendy effect which is manifested in i a progressive increase in 18o and 13c away from the growth axis and ii a positive correlation between 18o and 13c along a single growth layer of a stalagmite

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

a high resolution multi proxy stalagmite record from mechara southeastern ethiopia palaeohydrological implications for speleothem palaeoclimate reconstruction an annually laminated stalagmite from southeastern ethiopia grew for 443 8 yr starting at 5023 yr bp 160 yr as determined by lamina tuned u th dating the speleothem shows three growth phases 1 an initial phase where the stalagmite has a candlestick shape deposited by relatively slow rate drip water 2 a middle growth phase where laminae grow on the flanks suggesting faster drip rates and 3 a final growth phase where the speleothem becomes narrower owing to a decrease in drip water supply towards the end of deposition morphometry annual growth rate fluorescence index and 234u 238u isotope ratio show marked differences between the growth phases while 13c and 18o do not show significant variation except within the third phase towards the top of the stalagmite where they have higher values the study indicates that the multiproxy approach is crucial as the different proxies respond to single climate forcing in different manners our results can be widely applied to speleothem studies distinguishing the relative importance of the various proxies in recording cave external climate hydrology and cave internal e g evaporation processes copyright 2006 john wiley sons ltd

the hydrochemical response of cave drip waters to sub annual and inter annual climate variability wombeyan caves se australia abstract a thorough understanding of cave seepage waters is necessary to interpret geochemical variations in speleothem calcite in terms of changing surface climatic conditions at a particular site here we present the hydrochemistry of ten cave drip waters from a karst system in se australia based on up to 5 5 years of monitoring discharge was continuously measured at six sites and manually at the other sites dripwater samples were analysed for ph electrical conductivity cations and anions at all sites at monthly or more frequent intervals each drip possesses a unique chemistry and not all drip waters responded to antecedent short term hydrological variations for example the hydrochemical behaviour of three adjacent drips at a bedrock depth of 45 m was completely different to that of shallower sites and was apparently un related to surface hydrology throughout the investigation based on modelled calcite precipitation vectors prior calcite precipitation was demonstrated at several sites but can only be linked directly to changes in surface recharge at the shallowest sites at extremely low flow shallow drip waters accessed a high mg sr and ba source thought to be the overlying soil high frequency sample collection allows for the calculation of predicted mg ca calcite and sr ca calcite values highlighting that the sites with the greatest potential to record high resolution palaeohydrological records are those situated at shallow depth longer temporal resolution palaeohydrological records may be recorded at deeper sites but longer term monitoring is required to identify probable time scales inherent system non linearities dissolution of secondary calcite in pore spaces of the aquifer changes in the source of trace elements and the presence of multiple reservoirs confirm the need for the use of multiple speleothems and a multi proxy approach to gain accurate palaeohydrological records from this site

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