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

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

intra and inter annual growth rate of modern stalagmites we measure the factors that determine growth rate temperature drip rate calcium ion concentration for 31 waters that feed stalagmites within six cave systems throughout europe water samples were collected at a frequency of at least 1 month to permit the modelling of both inter and intra annual growth rate variations utilising the theory of wolfgang dreybrodt chem geol 29 1980 89 105 chem geol 32 1981 237 245 dreybrodt w 1988 processes in karst systems springer verlag berlin 288 pp inter annual growth rates were measured using the stalagmites that were associated with the analysed water samples growth rate was determined from annual lamina counting specific time markers within the stalagmites and location of bomb 14c when compared to theoretically predicted values a good agreement between theoretical and measured stalagmite growth rates is observed r2 0 69 when compared to site climate and geochemical parameters a good correlation is observed between measured growth rate and mean annual temperature for five sites r2 0 63 and dripwater calcium content r2 0 61 but not drip rate r2 0 09 the good correlation with both calcium and temperature is due to soil co2 production being primarily determined by surface temperature and soil moisture however when we compare our data to that in the grotte de clamouse a site that has little soil cover we observe that the growth rate temperature relationship breaks down due to either the lack of soil co2 production or prior calcite precipitation intra annual data demonstrates that maximum growth rate occurs when calcium concentrations are high and that this occurs under different seasons depending on the hydrology of each site our results demonstrate a stronger dependence of intra annual stalagmite growth rate on dissolved calcium ion concentrations than drip rate for the range of drip rates investigated here 0 01 t 2drip s 1 but for lower drip rates this factor becomes important in controlling growth rate we suggest that for well monitored and understood sites stalagmite growth rate variations can provide useful information for palaeoclimate reconstruction

extending the vostok ice core record of palaeoclimate to the penultimate glacial period the ice core record of local temperature dust accumulation and air composition at vostok station antarctica now extends back to the penultimate glacial period 140 200 kyr ago and the end of the preceding interglacial this yields a new glaciological timescale for the whole record which is consistent with ocean records temperatures at vostok appear to have been more uniformly cold in the penultimate glacial period than in the most recent one concentrations of co2 and ch4 correlate well with temperature throughout the record

recent flowstone growth rates field measurements in comparison to theoretical predictions abstract the model of calcite precipitation kinetics of d buhmann and w dreybrodt based on the rate laws of l n plummer et al is used to predict cave flowstone growth rates these theoretically modelled growth rates are compared to actual growth rates of recent samples found in cave and mine sites in southwest england a good agreement is found between modelled and actual growth rates within the 95 confidence level of the determinations although in general modelled growth rates overestimate actual growth rate by between 2 4 and 4 7 times several reasons for this overestimation are discussed including uncertainties arising from the experimental data of l n plummer et al seasonal shut off of water flow onto the flowstones and significant variations in the growth rate determining parameters during the period of flowstone growth for one flowstone an underestimation of growth rate is observed and is explained by the presence of rimstone pools which pond water on the sample surface

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

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

mineralogical and sub microscopic aspects of iron oxides in polygenetic oxisols from minas gerais brazil iron oxides are known to be useful paleo environmental indicators and their properties may give information about past and present circumstances of weathering and soil formation iron oxides from polygenetic oxisols developed on saprolites of metamorphic rocks soil saprolite sequences and on sediments soil sediment sequences from minas gerais brazil were studied by x ray diffraction mossbauer spectroscopy micromorphology and electron microscopy to establish the connection between their properties and circumstances of formation hematite and goethite are the only iron oxides found in the clay and silt fractions micromorphology and mineralogy indicated the presence of three genetically different forms of hematite and four forms of goethite xrd and mossbauer spectroscopy indicate that these forms have differences in mean coherence length mcl and al substitution in soil saprolite sequences hematite is mainly formed during saprolite formation while goethite formed mainly during soil formation microscopic hematite formed in the saprolite has low al substitution and uniform mcl in response to soil formation it diminishes to submicroscopic size and goethite is formed towards toposoils goethite formed in yellow surface soils reflects recent soil formation and has high al substitution hematites and goethites related to gley phenomena have low al substitution and large mcls different coexisting forms of either goethite or hematite point to varying pedo environments either in time corroborating the polygenetic nature of the studied soils or at micron scale

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

origin and palaeoenvironmental significance of lamination in stalagmites from katerloch cave austria the origin and environmental dependencies of lamination in stalagmites from katerloch common in speleothems from other cave sites are examined in detail petrographic observations and chemical analyses including isotopes of stalagmites and modern calcite were combined with multi annual cave monitoring all investigated stalagmites are composed of low mg calcite and show white porous laminae and typically thinner translucent dense laminae the binary lamination pattern results from changes in the calcite fabric white porous laminae are characterized by a high porosity and abundant fluid inclusions and also by enhanced vertical growth and thinning towards the flanks translucent dense laminae exhibit a compact fabric and constant thickness of individual growth layers u th dating supports an annual origin of the lamination and the seasonally changing intensity of cave ventilation provides a robust explanation for the observed relationships between lamination stable c isotopic compositions and trace elements mg sr and ba the seasonally variable air exchange driven by temperature contrasts between the cave interior and outside atmosphere modulates the rate and amount of co2 degassing from the drip water and affects the hydrochemistry and consequently the fabric of the precipitating calcite although cave air composition and drip rate are both major variables in controlling co2 degassing from the drip water the seasonally changing ventilation in katerloch exerts the primary control and the results suggest a secondary amplifying attenuating influence of the drip rate drip rate however might be the controlling parameter for lamina development at cave sites experiencing only small seasonal cave air exchange importantly the seasonally variable composition of drip water does not reflect the seasonal cycle of processes in the soil zone but results from exchange with the cave atmosphere the alternating porous and dense calcite fabric is the expression of a variable degree of lateral coalescence of smaller crystallites forming large columnar crystals the white porous laminae represent partial coalescence and form during the warm season low calcite 13c values are linked to low 13c values of cave air and drip water during that time this observation corresponds to times of reduced cave ventilation high pco2 of cave air low drip water ph lower calcite supersaturation and typically high drip rates in contrast the translucent dense laminae represent more or less complete lateral coalescence inclusion free during the cold season high calcite drip water and cave air 13c values i e times of enhanced cave ventilation low cave air pco2 increased drip water ph relatively high calcite supersaturation and typically low drip rates in essence the relative development of the two lamina types reflects changes in the seasonality of external air temperature and precipitation with a strong control of the winter air temperature on the intensity of cave air exchange thick translucent dense laminae are favoured by long cold and wet winters and such conditions may be related closely to the north atlantic oscillation mode weak westerlies and enhanced mediterranean cyclone activity during the cold season studies of speleothem lamination can thus help to better understand and quantify the role of seasonality changes for example during rapid climate events

testing theoretically predicted stalagmite growth rate with recent annually laminated samples implications for past stalagmite deposition annually laminated stalagmites deposited over the last 30 160 years are analysed to determine their growth rate three natural and artificial cave sites in england france and belgium were chosen for their wide range of variability in growth rate determining variables and multiple samples were taken from each site the annual nature of laminae deposition within the stalagmite calcite was confirmed by comparison to the date of cave void opening 14c analyses or by using dated event horizons measured stalagmite growth rate was determined from annual laminae thickness measurements and compared to that theoretically predicted from the chemical kinetics of the calcite precipitation reaction a good agreement is observed between empirical observations and theoretical predictions although two complicating factors variations in calcite porosity and seasonal cessation of the water supply to the samples both affect the growth rate implications for the extraction of palaeoclimate information from stalagmite growth rate are discussed

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

oxygen isotope precipitation anomaly in the north atlantic region during the 8 2 ka event an annual laminated stalagmite from northern spain recorded two outstanding oxygen isotope 18o pulses during the 8 2 ka event most of the oxygen isotope record variability is related to the amount of rainfall although other factors affect the signal the lamina thickness record which is also related to amount of rainfall does not show any significant anomaly at the time of oxygen isotope spikes considering the factors affecting the isotope signal the two prominent falls in 18o during the event are interpreted to be caused by the release of large amounts of fresh waters into the north atlantic thus 18o depleted ocean surface waters shifted the rainfall 18o composition for europe and greenland our precise chronology provides the timing of the outbursts that caused the 18o anomalies at 8350 8340 and 8221 8211 34 yr b p most probably generated by the drainage of proglacial lakes agassiz and ojibway therefore in the north atlantic region 18o records during the 8 2 ka event trace important hydrological modifications in the ocean not just local climate as a consequence paleoclimate reconstructions from europe and greenland using the 18o proxy that does not take this into account would be overestimating the magnitude of the anomalies during the 8 2 ka event

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

stalagmite growth and palaeo climate the numerical perspective abstract the growth of stalagmites can be approximated by a simple mathematical model which depends on growth rate and equilibrium radius these two parameters are controlled by the climate temperature variations derived from ice and deep sea core data together with models for changes in precipitation and soil cover are used to derive stalagmite stratigraphies which reflect the palaeo climate variations imposed in general stalagmite growth is strongly correlated to temperature and the amount of carbon dioxide available in the soil furthermore precipitation is correlated to the stalagmite diameter however several assumptions need to be made i a functional relationship between temperature on the one hand and precipitation and soil cover on the other needs to be established ii the kinetics of calcite dissolution and precipitation needs to be assigned either under soil and epikarst conditions open to the atmosphere or under fractured rock conditions closed from the atmosphere these assumptions are difficult to access from field data and therefore a stalagmite stratigraphy can be ambiguous and not easily converted back into an unknown palaeo climate signal

effect of aragonite to calcite transformation on the geochemistry and dating accuracy of speleothems an example from castanar cave spain aragonite speleothems are increasingly being used as high resolution climate proxies however aragonite is unstable and susceptible to diagenetic transformation into calcite leading to mineralogical textural and geochemical alterations that have not been fully investigated to provide some insights to these modifications this study combines stable isotope geochemistry and u series dating with petrological observations and empa elemental analyses to characterize a stalagmite from castanar cave caceres spain that shows primary aragonite diagenetically altered and with reverse ages the diagenetic processes include recrystallization to calcite micritization and dissolution characterization and interpretation of the chemistry and nature of the waters from which the aragonite precipitated and of the ones that subsequently formed the calcite indicates that both polymorphs formed from the same fluids these fluids hydrochemically evolved from an aragonite mode to a calcite mode along a diagenetic path within the sample the results show that during transformation the system stayed close in one of the stages and open in the other with the same textural result reverse ages are found either in the recrystallized areas or in the primary aragonite caused by two different u remobilization mechanisms u leaching due to flowing waters on the surface and u loss during the transformation process these results highlight the complex behavior of speleothems during diagenesis and the impact on the geochemical information of the primary and secondary phases and thus the importance of petrological and geochemical characterization of speleothems for paleoclimatic studies

very high frequency and seasonal cave atmosphere pco2 variability implications for stalagmite growth and oxygen isotope based paleoclimate records abstract cave air p co 2 at two irish sites varied dramatically on daily to seasonal timescales potentially affecting the timing of calcite deposition and consequently climate proxy records derived from stalagmites collected at the same sites temperature dependent biochemical processes in the soil control co 2 production resulting in high summer p co 2 values and low winter values at both sites large large amplitude high frequency variations superimposed on this seasonal cycle reflect cave air circulation here we model stalagmite growth rates which are controlled partly by co 2 degassing rates from drip water by considering both the seasonal and high frequency cave air p co 2 variations modeled hourly growth rates for stalagmite cc bil from crag cave in sw ireland reach maxima in late december 0 063 m h 1 and minima in late june early july 0 033 m h 1 for well mixed diffuse flow cave drips such as those that feed cc bil high summer cave air p co 2 depresses summer calcite deposition while low winter p co 2 promotes degassing and enhances deposition rates in stalagmites fed by well mixed drips lacking seasonal variations in 18 o integrated annual stalagmite calcite 18 o is unaffected however seasonality in cave air p co 2 may influence non conservative geochemical climate proxies e g 13 c sr ca stalagmites fed by seasonal drips whose hydrochemical properties vary in response to seasonality may have higher growth rates in summer because soil air p co 2 may increase relative to cave air p co 2 due to higher soil temperatures this in turn may bias stalagmite calcite 18 o records towards isotopically heavier summer drip water 18 o values resulting in elevated calcite 18 o values compared to the equilibrium values predicted by calcite water isotope fractionation equations interpretations of stalagmite based paleoclimate proxies should therefore consider the consequences of cave air p co 2 variability and the resulting intra annual variability in calcite deposition rates

a stepwise screening system to select storm sensitive stalagmites taking a targeted approach to speleothem sampling methodology a stepwise stalagmite sample screening process was applied in order to select a stalagmite as a sensitive recorder of recent tropical cyclone rainfall events near belize field and laboratory criteria were combined in series to screen out candidate stalagmites whose characteristics indicated lower sensitivity to stormwater infiltration the approach described here was designed to increase the likelihood that selected stalagmites would increase the signal noise ratio of the target phenomenon in the resulting proxy records this four stage method for sample selection may be an important methodological consideration for researchers attempting to use speleothems for stable isotope paleotempestology hallmarks of this approach include 1 establishing a priori scientific targets 2 applying sample criteria in the form of contra indicators and 3 organizing the sample screening protocol into a series of practical stages the overall approach to stalagmite selection presented here supports cave conservation and can be adapted readily by others in support of different scientific goals it is hoped that other investigators will also publish field and laboratory sample selection schemes as increased transparency will provide new information invaluable to replication efforts and to advancing the field of speleothem paleo environmental studies

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

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

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

controls on water drop volume at speleothem drip sites an experimental study summary the growth of speleothem under cave drip sites is closely related to local climate events and provides an increasingly important means of deciphering past climate change since calcite precipitation rates depend on the water discharge at the drip site the drip rate and mass of water drops detaching from stalactites are fundamental controls on speleothem growth and we have investigated factors that control the volume of water drops in this environment the classical investigations on the volume of falling water drops are reviewed but there have been no measurements of the volume of drops detaching from curved surfaces equivalent to tips of stalactites in this study we have used an acoustic drop counting method to measure the variation of the mass of water drops detaching from tubes representing soda straw stalactites and artificial stalactites with spherical terminations representing massive stalactites as a function of tube radius or surface curvature and the drip rate the experimental method corroborates classical measurements of drop mass detaching from tubes and for massive stalactites we derive a simple empirical relationship between drop mass and radius of curvature of a spherical surface based on 100 000 drop counts from artificial stalactites with 19 different radii ranging from 3 6 mm to 500 mm the results of this study allow discharge to be calculated from drip interval measurements and provide a quantitative basis for theoretical modelling of speleothem growth from drip sites

hydrological conditions over the western mediterranean basin during the deposition of the cold sapropel 6 ca 175 kyr bp a new oxygen isotope record is reported from a stalagmite collected in the argentarola cave located on the tyrrhenian coast of italy as shown from observations and numerical modeling of n 18 o in modern precipitation the recorded n 18 o variability for this zone is dominated by the amount of precipitation so called amount effect the n 18 o profile measured in the stalagmite is characterized by a prominent negative excursion ca 2 3x between 180 and 170 kyr bp this paleoclimatic feature is interpreted as being due to a relatively wet period which occurred during the penultimate glacial period more precisely during marine isotope stage 6 5 this pluvial phase is shown to correspond chronologically to the deposition of the sapropel event 6 s6 although this particular sapropel event occurred during a cold phase the n 18 o excursion is similar to those corresponding to other sapropels s4 s3 and s2 the evidence for humid conditions during s6 in the western mediterranean basin agrees with previous studies based on deep sea sediment cores taken collectively the data suggest that during sapropel events dilution of ocean surface waters was not restricted to the output of the river nile but was rather widespread over the entire mediterranean sea due to increased rainfall 2002 elsevier science b v all rights reserved

reconstruction of cave air temperature based on surface atmosphere temperature and vegetation changes implications for speleothem palaeoclimate records abstract cave temperature is a parameter of major importance for palaeoclimate studies based on speleothems since most proxies used are temperature dependent the general assumption that cave temperature reflects the mean annual surface atmosphere temperature sat over the cave is based on a limited number of specific studies and detailed mechanisms supporting this link are not properly described eagle cave in spain was used to understand the detailed mechanisms connecting sat and cave temperature a monitoring programme conducted from 2009 to 2011 allows the characterization of the thermal dynamics in the cave air in the studied karstic environment thermal conduction is the main mechanism responsible for transferring the ground temperature signal to the cave the calculated thermal diffusion coefficient is 0 756 10 6 0 013 m 2 s 1 the sat signal is recorded at the cave with a delay ranging from 3 to 11 yr depending on the thickness of the bedrock over the ceiling 5 18 m a cave cooling of 2 c has been recorded since mid 1970s when cave temperature measurements were made the application of a model exclusively based on thermal conduction of sat does not reproduce the observed thermal changes however vegetation cover over the cave was modified dramatically during recent decades this impacts ground temperature due to the changes in exposure to insolation and the modification of soil properties which is eventually recorded in the cave the incorporation of changes in vegetation cover in the model provides a realistic thermal reconstruction the impact of vegetation cover was much more significant than sat in order to explain the large thermal change in the cave over past decades thus the cooling in eagle cave during past decades is mainly controlled by a variable decoupling from mean annual sat as a result of the afforestation over the cave the effect of this thermal decoupling on speleothem 18 o records is potentially significant and should be considered when performing accurate palaeoclimate reconstructions

hydrodynamically locked morphogenesis in karst and ice flutings two of the most widespread and fascinating patterns observed on cave walls and icefalls karst and ice flutings are demonstrated to share the same morphogenesis whose core is a water film induced locking mechanism creeping flow based parallel and non parallel stability analyses are developed through a numerical and analytical approach these instabilities are shown to develop at inverted overhung conditions a sharp transition between fluting and ripple like patterns is presented the non parallel problem is solved with the use of papkovich neuber solutions in order to obtain a finite wavelength selection close to the critical conditions the method and results can be extended to similar problems where the temporal evolution of the interface is linearly related to the film depth

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

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

carbon dioxide concentration in temperate climate caves and parent soils over an altitudinal gradient and its influence on speleothem growth and fabrics carbon dioxide co2 concentrations in caves and parent soils in the italian alps have been studied along a 2100 m altitudinal range corresponding to a mean annual temperature mat range of 12 c in order to investigate the relationship between mat soil pco2 and cave air pco2 and to test the influence of soil pco2 on speleothem growth and fabric to ultimately gain insight into their palaeoclimatic significance in temperate climate settings our findings indicate that soil co2 is linearly correlated to mat and its mean annual concentration is described by the equation soil co2 ppmv 1112 460 mat soil pco2 can also be exponentially correlated to actual evapotranspiration the pco2 in the aquifer is linearly correlated to mat at the infiltration site and is more influenced by summer soil pco2 cave air co2 in the innermost part of the caves exhibits a similar seasonal pattern and commonly reaches concentrations of about 15 to 35 with respect to the corresponding soil values and is exponentially correlated to the mat at the infiltration site the combination of these parameters soil pco2 dripwater pco2 and cave air pco2 results in speleothem growth and controls their fabrics which are typical of four mat elevation belts broadly corresponding to the present day vegetation zones in the lower montane zone 100 800 m above sea level a s l speleothems mostly consist of columnar fabric in the upper montane zone 800 1600 m a s l both columnar and dendritic fabrics are common the subalpine zone 1600 2200 m a s l is characterized mostly by moonmilk deposits whereas in the alpine zone above 2200 m a s l no speleothems are forming today therefore fabric changes in fossil speleothem can potentially be used to reconstruct mat changes in temperate climate karst areas copyright 2015 john wiley sons ltd

the origin of the transverse instability of aeolian megaripples abstract flat sand beds subjected to wind stress are unstable and the wind action results in two types of aeolian sand ripples normal ripples and megaripples the distinction between the two types is based on two characteristics i the normal ripple pattern usually has a wavelength of up to 30 cm while the megaripple wavelength is on the order of meters and ii unimodal distributions of sand grain size lead to normal ripples while bimodal distributions result in megaripples on mars the distinction between the two types is more difficult to ascertain because the length scales of normal ripples and megaripples can overlap and often there is no detailed information regarding their grain size distribution unlike normal ripples megaripples show transverse instability whose mechanism remains elusive resulting in a much larger sinuosity of the crestline than normal ripples in this study we investigate the megaripples transverse instability by using field measurements wind tunnel experiments and numerical simulations of a three dimensional ripple model we show that a coarse grains accumulate at megaripple crests with a corresponding reduction of the lateral sand transport along the crest and b the transverse instability of megaripples is generated by a positive feedback between the height of the crest and the accumulation of coarse grains with more grains accumulating on the higher portions of the crest the outcomes of this positive feedback are that the thickness of the coarse grain armoring layer along the crest is not uniform and that it correlates with the crest height in turn these height differences drive the transverse instability such that higher portions of the ripple migrate more slowly than the lower sections creating a wavy crestline an analysis of martian ripple images shows variations in the sinuosity index suggesting that this characteristic can be useful in distinguishing between normal ripples and megaripples on mars

speleothems as sensitive recorders of volcanic eruptions the bronze age minoan eruption recorded in a stalagmite from turkey mounting evidence exists that variations in sulphur content in stalagmites are closely linked to changes in volcanic or anthropogenic atmospheric sulphur the strong dependency of sulphur on soil ph and ecosystem storage however can result in a delay of several years to decades in the registration of volcanic eruptions and anthropogenic emissions by stalagmites here we present synchrotron radiation based trace element analysis performed on a precisely dated section of a stalagmite from sofular cave in northern turkey as this section covers the time interval of the intensively studied minoan volcanic eruption between 1600 and 1650 bc we can test whether this vigorous eruption can be traced in a stalagmite of all measured trace elements only bromine shows a clear short lived peak at 1621 251621 25 bc whereas sulphur and molybdenum show peaks later at 1617 251617 25 and 1589 251589 25 respectively we suggest that all trace element peaks are related to the minoan eruption whereas the observed phasing of bromine molybdenum and sulphur is related to differences in their retention rates in the soil above sofular cave for the first time we can show that bromine appears to be an ideal volcanic tracer in stalagmites as it is a prominent volatile component in volcanic eruptions can be easily leached in soils and rapidly transferred from the atmosphere through the soil and bedrock into the cave and stalagmite respectively highly resolved oxygen and carbon isotope profiles indicate that the minoan eruption had no detectable climatic and environmental impact in northern turkey