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

influence of the tropics and southern westerlies on glacial interhemispheric asymmetry latitudinal variations in the location of the southern westerly wind belt have been associated with millennial scale climate variations during the last glacial period a reconstruction of sea surface temperatures off the southern coast of australia suggests that these climate variations also drove changes in the location of the oceanic subtropical front

putting the younger dryas cold event into context abstract the younger dryas event is by far the best studied of the millennial scale cold snaps of glacial time yet its origin remains a subject of debate the long held scenario that the younger dryas was a one time outlier triggered by a flood of water stored in proglacial lake agassiz has fallen from favor due to lack of a clear geomorphic signature at the correct time and place on the landscape the recent suggestion that the younger dryas was triggered by the impact of a comet has not gained traction instead evidence from chinese stalagmites suggests that rather than being a freak occurrence the younger dryas is an integral part of the deglacial sequence of events that produced the last termination on a global scale

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

hydrological change in southern europe responding to increasing north atlantic overturning during greenland stadial 1 greenland stadial 1 gs 1 was the last of a long series of severe cooling episodes in the northern hemisphere during the last glacial period numerous north atlantic and european records reveal the intense environmental impact of that stadial whose origin is attributed to an intense weakening of the atlantic meridional overturning circulation in response to freshening of the north atlantic recent high resolution studies of european lakes revealed a mid gs 1 transition in the climatic regimes the geographical extension of such atmospheric changes and their potential coupling with ocean dynamics still remains unclear here we use a subdecadally resolved stalagmite record from the northern iberian peninsula to further investigate the timing and forcing of this transition a solid interpretation of the environmental changes detected in this new accurately dated stalagmite record is based on a parallel cave monitoring exercise this record reveals a gradual transition from dry to wet conditions starting at 12 500 y before 2000 a d in parallel to a progressive warming of the subtropical atlantic ocean the observed atmospheric changes are proposed to be led by a progressive resumption of the north atlantic convection and highlight the complex regional signature of gs 1 very distinctive from previous stadial events

the july 20 2017 m6 6 kos earthquake seismic and geodetic evidence for an active north dipping normal fault at the western end of the gulf of gokova se aegean sea on july 20 2017 22 31 utc a strong mw 6 6 earthquake occurred at shallow depth between kos island greece and bodrum turkey we derive a co seismic fault model from joint inversion of geodetic data gnss and insar assuming that the earthquake can be modelled by the slip of a rectangular fault buried in an elastic and homogeneous half space the gnss observations constrain well most of the model parameters but do not permit to discriminate between south and north dipping planes however the interferograms produced from c band esa sentinel 1 data give a clear preference to the north dipping plane we also map surface motion away from the satellite along the turkish coast from bodrum towards the east which reached about 17 cm onshore islet karaada the best fit model is obtained with a 37 north dipping n283 e striking normal fault in agreement with the published moment tensor solutions the resolved slip vector is dominantly normal with a slight component of left lateral motion 15 the surface projection of the seismic fault outcrops in the gokova ridge area a well developed bathymetric feature inside the western gulf of gokova our geodetic model fits the pattern of the shallow north dipping aftershocks obtained from rigorous relocation of all available recordings in the region about 1120 events relocated mainshock is at 36 955 n 27 448 e depth at 9 2 km 0 5 km the relocated aftershocks also indicate clustering at both ends of the rupture and seismicity triggering mainly towards the east and the north within 2 weeks following the mainshock we also analysed regional gps data interseismic velocities and obtained an extension rate of 3 2 mm yr across the gokova rift along a direction n165 e

three thousand years of extreme rainfall events recorded in stalagmites from spring valley caverns minnesota article i nfo annual layer analysis in two stalagmites collected from spring valley caverns southeastern minnesota reveals hydrological response of the cave to extreme rainfall events in the midwest usa cave flooding events are identified within the two samples by the presence of detrital layers composed of clay sized particles comparison with instrumental records of precipitation demonstrates a strong correlation between these cave flood events and extreme rainfall observed in the upper mississippi valley a simple model is developed to assess the nature of rainfall capable of flooding the cave the model is first calibrated to the last 50 yr 1950 1998 a d instrumental record of daily precipitation data for the town of spring valley and verified with the first 50 yr of record from 1900 to 1949 a d frequency analysis shows that these extreme flood events have increased from the last half of the nineteenth century comparison with other paleohydrological records shows increased occurrence of extreme rain events during periods of higher moisture availability our study implies that increased moisture availability in the midwestern region due to rise in temperature from global warming could lead to an increase in the occurrence of extreme rainfall events

hydrochemical controls on aragonite versus calcite precipitation in cave dripwaters abstract despite the paleoclimatic relevance of primary calcite to aragonite transitions in stalagmites the relative role of fluid mg ca ratio supersaturation and co 3 2 concentration in controlling such transitions is still incompletely understood accordingly we have monitored the hydrochemistry of 50 drips and 8 pools that are currently precipitating calcite and or aragonite in el soplao and torca ancha caves n spain investigating the mineralogy and geochemistry of the caco 3 precipitates on the corresponding natural speleothem surfaces the data reveal that apart from possible substrate effects dripwater mg ca is the only obvious control on caco 3 polymorphism in the studied stalagmites and pools where calcite and aragonite precipitating dripwaters are separated by an initial i e at stalactite tips mg ca threshold at 1 1 mol mol within the analyzed ranges of ph 8 2 8 6 co 3 2 concentration 1 6 mg l supersaturation si aragonite 0 08 1 08 si calcite 0 23 1 24 drip rate 0 2 81 drops min and dissolved zn 6 90 g l we observe no unequivocal influence of these parameters on caco 3 mineralogy despite the almost complete overlapping supersaturations of calcite and aragonite precipitating waters the latter are on average less supersaturated because the waters having mg ca above 1 1 have mostly achieved such high ratios by previously precipitating calcite both calcite and aragonite precipitated at or near oxygen isotopic equilibrium and mg incorporation into calcite was consistent with literature based predictions indicating that in the studied cases caco 3 precipitation was not significantly influenced by strong kinetic effects in the studied cases the calcites that precipitate at 11 c from dripwaters with initial mg ca approaching 1 1 incorporate 5 mol mgco 3 close to the published value above which calcite solubility exceeds aragonite solubility suggesting that aragonite precipitation in high relative humidity caves is favored from a solubility viewpoint we also show that unaccounted caco 3 precipitation in intermediate sampling containers and splash effects may in cases result in underestimating dripwater ca concentration and alkalinity potentially leading to incorrect conclusions regarding the role of fluid mg ca ratio and supersaturation on caco 3 mineralogy a simple way to elude the first effect is by taking water samples directly from stalactites and by titrating alkalinity in the same containers used to collect dripwaters

paleoclimate and growth rates of speleothems in the northwestern iberian peninsula over the last two glacial cycles abstract speleothem growth requires humid climates sufficiently warm to stimulate soil co2 production by plants we compile 283 u th dates on 21 stalagmites from six cave systems in the nw coast of spain to evaluate if there are patterns in stalagmite growth that are evidence of climatic forcing in the oldest stalagmites from marine oxygen isotope stage mis 7 5 growth persists through the glacial period hiatuses and major reductions in growth rate occur during extreme minima in summer insolation stalagmites active during the last interglaciation cease growth at the mis 5 4 boundary 74 ka when regional sea surface temperature cooled significantly during mis 3 only two stalagmites grew rates were highest between 50 and 60 ka during the maximum in summer insolation one stalagmite grew briefly at 41 ka 36 5 and 28 6 ka all during warm phases of the dansgaard oeschger cycles a pronounced holocene optimum in stalagmite growth occurs from 9 to 6 ka the cessation of most growth by 4 1 ka coincident with broad increases in aridity over the mediterranean and areas influenced by the north african monsoon suggest that regions such as nw spain with dominant atlantic moisture sources also experienced increased aridity at this time

paleo watertable definition using cave ferromanganese stromatolites and associated cave wall notches sierra de arnero spain abstract the steeply dipping dolostone hosted caves of the sierra de arnero n spain contain low gradient relict canyons with up to ten mapped levels of ferromanganese stromatolites and associated wall notches over a vertical range of 85 m the highest occurring 460 m above base level despite a plausible speleogenetic contribution by pyrite oxidation and the irregular cave wall mesomorphologies suggestive of hypogenic speleogenesis the arnero relict caves are dominantly epigenic as indicated by the conduit pattern and the abundant allogenic sediments allogenic input declined over time due to a piracy related decrease in the drainage area of allogenic streams explaining the large size of the relict arnero caves relative to the limited present day outcrop area of the karstified carbonates allogenic sediment input also explains the observed change from watertable canyons to phreatic conduits in the paleo downstream direction stromatolites and notches arguably formed in cave stream passages at the watertable the best defined paleo watertables show an overall slope of 1 7 consistent with the present day relief of the watertable with higher slope segments caused by barriers related to sulfide mineralization the formation of watertable stromatolites favored wall notching by the combined effect of enhanced acidity by mn fe oxidation and shielding of cave floors against erosion abrasive bedload further contributed to notch formation by promoting lateral mechanical erosion and protecting passage floors the irregular wallrock erosional forms of arnero caves are related partly to paragenesis and partly to the porous nature of the host dolostones which favored irregular dissolution near passage walls generating friable halos subsequent mechanical erosion contributed to generate spongework patterns the dolostone porosity also contributes to explain the paradox that virtually all arnero caves are developed in dolostone despite being less soluble than adjacent limestone u series dating of carbonate speleothems and paleomagnetic data from ferromanganese stromatolites and clastic sediments indicate that the paleo watertables recorded 320 m above the present day watertable formed during the matuyama chron but prior to 1 5 ma implying long term base level lowering rates from 125 to 213 m ma to our knowledge this is the first attempt of paleomagnetic dating of cave ferromanganese stromatolites these deposits are excellent geomagnetic recorders and offer a direct way to delineate and date paleo watertables especially in caves developed in dolostone

early holocene humidity patterns in the iberian peninsula reconstructed from lake pollen and speleothem records abstract comparison of selected well dated lacustrine speleothem and terrestrial pollen records spanning the holocene onset and the early holocene ca 11 7 8 cal kyrs bp in the iberian peninsula shows large hydrological fluctuations and landscape changes with a complex regional pattern in timing and intensity marine pollen records from alboran the mediterranean and off shore atlantic sites show a step wise increase in moisture and forest during this transition however available continental records point to two main patterns of spatial and temporal hydrological variability i atlantic influenced sites located at the northwestern areas enol sanabria lucenza prd 4 characterized by a gradual increase in humidity from the end of the younger dryas to the mid holocene similarly to most north atlantic records and ii continental and mediterranean influenced sites laguna grande villarquemado fuentillejo padul estanya banyoles salines with prolonged arid conditions of variable temporal extension after the younger dryas followed by an abrupt increase in moisture at 10 9 cal kyrs bp different local climate conditions influenced by topography or the variable sensitivity gradual versus threshold values of the proxies analyzed in each case are evaluated vegetation composition conifers versus mesothermophilous taxa and resilience would explain a subdued response of vegetation in central continental areas while in mediterranean sites insufficient summer moisture availability could not maintain high lake levels and promote mesophyte forest in contrast to atlantic influenced areas comparison with available climate models greenland ice cores north atlantic marine sequences and continental records from central and northern europe and the whole mediterranean region underlines the distinctive character of the hydrological changes occurred in inner iberia throughout the early holocene the persistent arid conditions might be explained by the intensification of the summer drought due to the high seasonality contrast at these latitudes caused by the orbital induced summer insolation maximum new records particularly from western and southernmost iberia and palaeoclimate models with higher spatial resolution would help to constrain these hypotheses

regional temperature atmospheric circulation and sea ice variability within the younger dryas event constrained using a speleothem from northern iberia precisely dated high resolution stable isotope and trace element data from a stalagmite from la garma cave northern spain reveal several stages of distinct climatic variability along the northern iberian atlantic margin and provide new constraints on the latitude of north atlantic westerlies during the younger dryas event yd westerly wind position reconstructed using sub annually resolved mg data as a proxy for sea spray contributions associated with wind strength at this coastal cave site during the early yd 12 85 12 15 kyr oscillated meridionally resembling the decadal scale component of the modern north atlantic oscillation nao northward repositioning of westerly storm tracks over northern iberia began at 12 15 kyr consistent with other high resolution wind proxy reconstructions from central and northern europe but occurred more gradually nearer the atlantic margin from 12 15 kyr to the yd termination atmospheric circulation resembled a persistently positive nao with westerlies reaching their maximum northward extent at 11 8 kyr reflected by a mg concentration minimum at this time air temperature reflected by our 18o data and iberian wind strength were predominantly coupled throughout the yd suggesting that temperature modulated sea ice extent and consequently controlled westerly wind latitude however our data suggest that abrupt warming at 12 1 kyr was followed by much more gradual northward shifts in westerly position and that a lag existed between the warming and sea ice retreat this gradual return of the westerlies to the north beginning at 12 1 kyr is consistent with inferred changes in wind strength at other european sites additionally atmospheric circulation inferred from our northern iberian wind strength proxy record generally tracked low frequency meridional shifts in intertropical convergence zone position corroborating past research that suggested closely coupled low and high latitude atmospheric teleconnections over this period

late holocene annual growth in three alpine stalagmites records the influence of solar activity and the north atlantic oscillation on winter climate annual growth rates and the ratio of dark to light colored calcite within single annual laminae in three contemporaneously deposited holocene speleothems from grotta di ernesto an alpine cave in northern italy respond to changes in surface temperature rather than precipitation based on monitoring of present day calcite growth and correlation with instrumental data for surface climatic conditions we interpret a higher ratio of dark to light colored calcite and the simultaneous thinning of annual laminae as indicative of colder than present winters such dark and thin laminae occur in those parts of the three stalagmites deposited from ad 1650 to 1713 and from ad 1798 to 1840 as reconstructed through lamina counting these periods correspond to the well known maunder and dalton minima of solar activity an 11 yr cyclicity in growth rate coupled with reduced calcite deposition during the historic minima of solar activity is indicative of a solar influence on lamina thickness spectral analysis of the lamina thickness data also suggests that the north atlantic oscillation variability influenced winter temperatures based on the present day controls on cave calcite formation we infer that high frequency changes in solar activity modulated the seasonal duration of soil co2 production

timing and dynamics of the last deglaciation from european and north african δ13c stalagmite profiles comparison with chinese and south hemisphere stalagmites abstract the last deglaciation and its climatic events such as the bolling allerod ba and the younger dryas yd have been clearly recorded in the 13 c profiles of three stalagmites from caves from southern france to northern tunisia the three 13 c records dated by thermal ionization mass spectrometric uranium thorium method tims show great synchroneity and similarity in shape with the chinese cave 18 o records and with the marine tropical records leading to the hypothesis of an in phase between 15 5 and 16 ka 0 5 ka postglacial warming in the northern hemisphere up to at least 45 n the ba transition appears more gradual in the speleothem records than in the greenland records and the allerod seems warmer than the bolling showing here close similarities with other marine and continental archives a north south gradient is observed in the ba trend it cools in greenland and warms in our speleothem records several climatic events are clearly recognizable a cooler period at about 14 ka older dryas od the intra allerod cold period at about 13 3 ka the yd cooling onset between 12 7 and 12 9 0 3 ka similar to the ba the yd displays a gradual climate amelioration just after its onset at 12 75 0 25 ka up to the preboreal and is punctuated by a short climatic event at 12 15 ka even though the southern hemisphere stalagmite records seem to indicate that the postglacial warming started about 3 ka 1 8 ka earlier in new zealand 41 s and about 1 to 2 ka earlier in south africa 24 1 s large age uncertainties essentially due to slow growth rates make the comparison still perilous the overall 13 c speleothem record seems to follow a baseline temperature increase controlled by the increase in insolation and punctuated by cold events possibly due to the n america freshwater lake discharges

seasonal dripwater mg ca and sr ca variations driven by cave ventilation implications for and modeling of speleothem paleoclimate records a 4 year study in a central texas cave quantifies multiple mechanisms that control dripwater composition and how these mechanisms vary at different drip sites we monitored cave air compositions in situ calcite growth dripwater composition and drip rate every 4 6 weeks three groups of drip sites are delineated groups 1 3 based on geochemical variations in dripwater composition quantitative modeling of mineral solution reactions within the host carbonate rock and cave environments is used to identify mechanisms that can account for variations in dripwater compositions the covariation of mg ca and sr ca and sr isotopes is key in delineating whether mg ca and sr ca variations are dictated by water rock interaction i e calcite or dolomite recrystallization or prior calcite precipitation pcp group 1 dripwater compositions reflects a narrow range of the extent of water rock interaction followed by varying amounts of prior calcite precipitation pcp group 2 dripwater compositions are controlled by varying amounts of water rock interaction with little to no pcp influence group 3 dripwater compositions are dictated by variable extents of both water rock interaction and pcp group 1 drip sites show seasonal variations in dripwater mg ca and sr ca whereas the other drip sites do not in contrast to the findings of most previous dripwater mg ca sr ca studies these seasonal variations at group 1 drip sites are independent of changes in water flux i e rainfall and or drip rate and instead significantly correlate with changes in cave air co2 concentrations these results are consistent with lower cave air co2 related to cool season ventilation of the cave atmosphere enhancing calcite precipitation and leading to dripwater geochemical evolution via pcp group 1 dripwater mg ca and sr ca seasonality and evidence for pcp as a mechanism that can account for that seasonality have two implications for many other regions where seasonal ventilation of caves is likely 1 speleothem trace element records may provide seasonal signals and 2 such records may be biased toward recording climate conditions during the season when calcite is depositing additionally we use our results to construct a forward model that illustrates the types of speleothem mg ca and sr ca variations that would result from varying controls on dripwater compositions the model provides a basis for interpreting paleodripwater controls from high frequency mg ca and sr ca variations for speleothems from caves at which long term monitoring studies are not feasible 2011 elsevier ltd all rights reserved

speleothems from the earliest quaternary snapshots of paleoclimate and landscape evolution at the northern rim of the alps abstract ancient cave systems in the northern calcareous alps today located well above the timberline at altitudes of 2400 2500 m host u rich speleothems that preserved growth layers on the microscopic scale of presumably annual origin two flowstone samples were dated to 2 019 0 037 0 069 ma and 1 730 0 032 0 068 ma respectively using u pb isochron techniques these ages are corroborated by the late pliocene to early pleistocene pollen spectrum extracted from one of the samples we use a multiproxy approach and exploit laminated speleothem sequences to tie high resolution stable isotope data to a floating lamina counted chronology o isotope values of growth intervals when calcite deposition was close to isotopic equilibrium are low compared to modern and holocene speleothems from other alpine caves and are inconsistent with the current altitudinal setting of the caves a vegetated but geomorphologically stable alpine catchment i e 2000 m asl no peri glacial processes combined with a deep seated cave the thickness of the vadose zone might have exceeded 1000 m is required in order to reconcile the isotopic data with the pollen record and the petrographic evidence furthermore the data can be used to constrain the rate for quaternary rock uplift to 0 8 mm annum for this frontal part of the european alps collectively the data suggest that these speleothems formed both during interglacials mis 59 or 61 and interglacial glacial transitions mis 75 74 or 77 76 but the seasonal precipitation pattern was arguably markedly different from today s provided that the highly regular microscopic laminae are indeed annual lamina counts suggest a minimum length of ca 6 ka for interglacials during the earliest pleistocene

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

on the timing of retreat of the loch lomond younger dryas readvance icefield in the sw scottish highlands and its wider significance abstract it has long been assumed that the last glacier expansion in the scottish highlands the loch lomond readvance llr resulted from a cold reversal that was broadly coeval with the younger dryas episode this view has recently been challenged with the suggestion that glacier ice had disappeared from rannoch moor one of the main ice accumulation centres in the sw scottish highlands by as early as 12 5 ka i e within the first half of the younger dryas here we present new radiocarbon tephrostratigraphical and pollen stratigraphical evidence from one of the key sites on rannoch moor the results of an experiment designed to test this hypothesis our results not only contradict that concept but are fully compatible with other evidence from the sw scottish highlands that suggests that the llr glaciers in this area continued to expand until towards the end of the younger dryas period and may have persisted in some places after the onset of the holocene we consider the possible reasons for this marked divergence in chronology a matter that is crucial to resolve because the precise timing of the demise of the llr glaciers has important palaeoclimatic and other implications in the wider context we also draw attention to problems with the general use of the term younger dryas and why we regard the greenland stratotype unit and term greenland stadial 1 gs 1 a more secure stratigraphic comparator

data model comparison of soil water δ 18 o at a temperate site in n spain with implications for interpreting speleothem δ 18 o summary an understanding of how seasonal and longer term 18 o signals in meteoric precipitation 18 o p are modified by percolation through soils is essential to link temporal changes in speleothem 18 o to surface climatic conditions this study focuses on modifications that occur in a relatively thick soil above a temperate cave site la garma n spain monthly soil water 18 o 18 o sw values at a depth of 60 cm through the year are only 14 of the range in 18 o p implying substantial homogenisation and attenuation of seasonal signals a striking feature is that 18 o sw values at 60 cm depth are lowest in summer and highest in winter the opposite anti phase to that observed in rainfall soil water residence times of up to circa 6 months in the upper 60 cm of soil and a matrix flow piston type infiltration behaviour with mixing are inferred evaporative effects on recovered soil water 18 o are minimal at this wet temperate site in contrast with published results from arid and semi arid sites a soil water model is presented to estimate monthly 18 o sw as a function of air temperature and 18 o p incorporating effects such as variations in the amount of infiltrated water changes in the ratio between evaporation and transpiration mixing with antecedent soil moisture and small enrichments in 18 o linked to evaporation and summer moisture deficits our model reproduces the observed 18 o sw results and produces 18 o outputs in excellent agreement with 18 o data for two monitored drip water sites at la garma cave that exhibit seasonal 18 o variability we conclude that simple evapotranspiration models that permit infiltration during months that have a positive hydrological balance only tend to underestimate summer rainfall contributions overall the study provides an improved framework for predicting 18 o sw trends at temperate sites such as la garma that have a relatively thick soil cover as well as for understanding seasonal ranges and trends in 18 o in cave drip sites

temperature and altitudinal influence on karst dripwater chemistry implications for regional scale palaeoclimate reconstructions from speleothems abstract the reconstruction of robust past climate records from speleothems requires a prior understanding of the environmental and hydrological conditions that lead to speleothem formation and the chemical signals encoded within them on regional scales there has been little quantification of the dependency of cave dripwater geochemistry on meteorology net infiltration temperature environmental and geographical factors elevation latitude soil activity vegetation cover atmospheric aerosol composition and geological properties of the aquifer lithology porosity and thickness in the present study we analysed over 200 karst waters collected in 11 caves of the trentino region ne italy the caves span sub humid mediterranean to cold humid temperate climates and infiltration elevations zinf ranging from 355 to 2400 m a s l corresponding to infiltration mean annual temperatures matinf between 12 and 0 c since all the caves developed in pure carbonate rocks soil pco2 is found to be the main factor controlling the carbonate dissolution for this reason the parameters controlling the carbonate carbonic acid system and calcite saturation state sicc are directly correlated with the matinf which influences the vegetation zones and eventually the production of co2 in the soil sicc linearly depends on matinf sicc 0 09 matinf 0 4 and sicc 0 is reached at zinf 1 66 km a s l corresponding to a matinf 4 4 c this point identifies the speleothem limit defined here as the elevation or corresponding matinf above which no sparitic speleothem precipitation usually occurs we demonstrate that due to temperature forced changes in the soil and vegetation and subsequently sicc the speleothem limit shifts to higher altitudes during maximum interglacial conditions speleothems from high altitude caves 1 5 2 5 km a s l thus can identify optimum interglacial periods by contrast speleothems formed at lower altitudes are better suited as archives of hydrological proxies at altitudes below 1 2 km a s l prior calcite precipitation pcp modifies percolating waters particularly during periods of reduced infiltration we introduce the use of the sio2 ca and so4 ca ratios in cave waters to complement mg ca and sr ca ratios as markers of pcp so4 and sio2 are derived from atmospheric deposition and siliciclastic minerals in the soil zone rather than carbonate host rocks as in the case of mg and sr by combing shifts to higher mg ca sio2 ca and so4 ca ratios along their characteristics pcp lines we improve the robustness of the interpretation that this resulted from increasing pcp rather than incongruent calcite dissolution icd our method permits the quantification of pcp between 0 and 40 for low elevation cave waters this novel approach has important implications for speleothem based paleoclimate studies where the distinction between pcp and icd can be ambiguous and in combination with mg ca and sr ca ratios permits the quantification of net infiltration and or rainfall amount from speleothem records

rapid oceanic and atmospheric changes during the younger dryas cold period the younger dryas event which began approximately 12 900 years ago was a period of rapid cooling in the northern hemisphere driven by large scale reorganizations of patterns of atmospheric and oceanic circulation 1 3 environmental changes during this period have been documented by both proxy based reconstructions 3 and model simulations 4 but there is currently no consensus on the exact mechanisms of onset stabilization or termination of the younger dryas 5 8 here we present high resolution records from two sediment cores obtained from lake krakenes in western norway and the nordic seas multiple proxies from lake krakenes are indicative of rapid alternations between glacial growth and melting during the later younger dryas meanwhile reconstructed sea surface temperature and salinity from the nordic seas show an alternation between sea ice cover and the influx of warm salty north atlantic waters we suggest that the influx of warm water enabled the westerly wind systems to drift northward closer to their present day positions the winds thus brought relatively warm maritime air to northern europe resulting in rising temperatures and the melting of glaciers subsequent input of this fresh meltwater into the ocean spurred the formation of sea ice which forced the westerly winds back to the south cooling northern europe we conclude that rapid alternations between these two states immediately preceded the termination of the younger dryas and the permanent transition to an interglacial state the impact of freshwater pulses released from northern hemisphere ice sheets on the north atlantic meridional overturning circulation has been suggested as a likely mechanism for the younger dryas cooling 7 11 in addition a responsive sea ice cover has been proposed as a mechanism that could rapidly alter the heat exchange between the ocean and atmosphere during the last glacial period 12 13 the roles of the ocean and the atmosphere in triggering the climate shifts around the younger dryas are much discussed 9 these hypotheses are difficult to resolve partly because the temporal resolution of most palaeoclimate archives is too coarse to enable the anatomy of the younger dryas stadial to be adequately described 14 to address these questions we here present a lake sediment record at sub annual resolution together with new data on the sea surface conditions of the norwegian atlantic current nwac throughouttheyoungerdryasstadial fig 1

north iberian temperature and rainfall seasonality over the younger dryas and holocene abstract several stalagmite records have yielded important but discontinuous insights into northern iberian climate since the last glacial here we present the first continuous iberian stalagmite based reconstruction of climate since the bolling allerod interstadial from a single stalagmite sample gar 01 from la garma cave cantabria the 13 5 ka gar 01 record provides the opportunity for replication continuation and aggregation of previously published records from northern spain the gar 01 record reveals shifts in oxygen isotope ratios that are inexplicable by appealing to a single control i e exclusively temperature rainfall amount etc herein we explore the potential role of rainfall and temperature seasonality shifts on the new 18o record using a simple monte carlo approach to estimate the seasonal distribution of rainfall and the annual temperature range at 100 year timeslices across the record this model is corroborated by intervals of monthly resolved laser ablation trace element data providing glimpses into past iberian seasonality shifts the most salient features of the modelled results include extremely dry younger dryas winters 12 9 11 6 ka bp and several intervals during the mid holocene with almost no summer rainfall e g at 4 2 and 9 0 ka bp by 1 6 ka bp a near modern rainfall seasonality was established according to the modelling results seasonal rainfall and temperature distribution variability can account for 95 of the record the model presented here provides a new tool for extracting critical missing seasonality information from stalagmite 18o records intervals where the model does not converge may represent transient climate anomalies with unusual origins that warrant further investigation

a uniform database of teleseismic shear wave splitting measurements for the western and central united states we present a shear wave splitting sws database for the western and central united states as part of a lasting effort to build a uniform sws database for the entire north america the sws measurements were obtained by minimizing the energy on the transverse component of the pks skks and sks phases each of the individual measurements was visually checked to ensure quality this version of the database contains 16 105 pairs of splitting parameters the data used to generate the parameters were recorded by 1774 digital broadband seismic stations over the period of 1989 2012 and represented all the available data from both permanent and portable seismic networks archived at the incorporated research institutions for seismology data management center in the area of 26 00 n to 50 00 n and 125 00 w to 90 00 w about 10 000 pairs of the measurements were from the 1092 usarray transportable array stations the results show that approximately 2 3 of the fast orientations are within 30 from the absolute plate motion apm direction of the north american plate and most of the largest departures with the apm are located along the eastern boundary of the western us orogenic zone and in the central great basins the splitting times observed in the western us are larger than and those in the central us are comparable with the global average of 1 0 s the uniform database has an unprecedented spatial coverage and can be used for various investigations of the structure and dynamics of the earth

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

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

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

high resolution greenland ice core data show abrupt climate change happens in few years the last two abrupt warmings at the onset of our present warm interglacial period interrupted by the younger dryas cooling event were investigated at high temporal resolution from the north greenland ice core project ice core the deuterium excess a proxy of greenland precipitation moisture source switched mode within 1 to 3 years over these transitions and initiated a more gradual change over 50 years of the greenland air temperature as recorded by stable water isotopes the onsets of both abrupt greenland warmings were slightly preceded by decreasing greenland dust deposition reflecting the wetting of asian deserts a northern shift of the intertropical convergence zone could be the trigger of these abrupt shifts of northern hemisphere atmospheric circulation resulting in changes of 2 to 4 kelvin in greenland moisture source temperature from one year to the next

manganese stromatolites in caves el soplao cantabria spain in the dark regions of caves the formation of stromatolites is virtually unknown although mn oxide crusts presumably induced by bacteria have been described in some caves they lack stromatolite features and the evidence of microbial origin is normally inconclusive here we describe for the first time the occurrence of extensive mn oxide stromatolites formed in the deep interior of a cave the stromatolites are of decimeter thickness and kilometer extent and show features extremely similar to typical caco 3 stromatolites however unlike most stromatolites their biogenicity is supported by the exceptional abundance of fossil microbes our data support that the stromatolites were mainly induced by chemolithotrophic mn oxidizing microbes and were formed in a low gradient water table stream passage at least 1 m y ago the el soplao stromatolites cantabria spain may contribute to increasing our understanding of microbial life in extreme environments as well as the role of bacteria in the genesis of modern and ancient mn deposits

climate variability across the last deglaciation in nw iberia and its margin abstract the direct comparison between marine and terrestrial data from the nw iberian margin core md03 2697 allows us to accurately evaluate without chronological ambiguity the vegetation response to north atlantic climate events across the last deglaciation comparison of md03 2697 data with other marine and terrestrial records from a vast area stretching from the azores to western w france iberia and its margin the w mediterranean and nw africa reveals the importance of enhanced winter north atlantic westerlies episodes in driving a heterogeneous regional climatic signal during particular events of the last deglaciation heinrich stadial 1 hs1 oldest dryas is a complex event marked by three synchronous main phases a extremely cold relatively wet b cool dry c relatively warmer increasing moisture availability in regions directly influenced by the north atlantic while it is characterized by a single phase cold and dry in most inland and high altitude areas changes in the strength and position of north atlantic westerlies could explain the variability in moisture during hs1 from w pyrenees to w mediterranean the bolling allerod b a event is marked by a synchronous progressive increase of ocean and atmospheric temperatures and precipitation from the bolling to the allerod in w iberia and w pyrenees contrasting with the greenland temperature pattern mid to high latitudes thermal contrast and the gradual strengthening of the atlantic meridional overturning circulation amoc triggered the continuing enhancement of westerlies and moisture along this period finally the younger dryas yd stadial is characterized by a land ocean synchronous returning cold conditions but not so cold as hs1 and although dry conditions persisted during this period extreme winter precipitation occurrences might have affected the most coastal areas of north and central w iberia and pyrenees in contrast dry conditions persisted during the yd in the western mediterranean regions the westerlies migrated further north following the displacement of the polar front during the deglaciation precluding the input of moisture in the w mediterranean region which persisted very dry during the yd stadial

shear wave splitting measurements problems and solutions abstract we compare sensitivity and reliability of three basic techniques of shear wave splitting analysis cross correlation of wave components minimization of covariance matrix eigenvalues and minimizing energy on the transverse component of both synthetic and real data point out some problems and propose solutions we discuss major difficulties of evaluating shear wave splitting parameters which are not always obvious in routine processing and can sometimes lead to false results and wrong interpretations we describe effects of pre processing of digital records of shear waves e g filtering and setting lengths of analyzed signals and discuss reliability of results to minimize outliers in evaluated splitting parameters for reliable evaluation of splitting of medium quality sks wave forms which are valuable mainly in temporary deployments of stations we recommend a careful band pass filtering of the signal using a window length not shorter than the dominant period inspecting the signal noise ratio on t component and the particle motion the transverse minimization method provides usually more robust and stable solutions than the other two methods in the conclusion we suggest how to proceed in evaluation of splitting parameters to ensure reliable solutions even for medium or low quality shear waveforms recorded frequently during temporary field measurements

regional climate variability and ecosystem responses to the last deglaciation in the northern hemisphere from stable isotope data and calcite fabrics in two northern adriatic stalagmites abstract geochemical and physical changes along the growth axis of speleothems are controlled by climate as well as the dynamics of the host karst system discriminating between the two is one of the major challenges in assembling robust cave palaeoclimate records overcoming this dilemma may be achieved by investigating multiple properties from two or more speleothems from the same cave spanning the same time interval in this study we use high resolution stable oxygen and carbon isotope 13c and 18o morphological and petrographic data from two calcite stalagmites sv1 and sv7 from grotta savi italy to help constraining the regional climate conditions during the younger dryas the new sv1 record spanning 15 3 9 4 ka builds on a previously published low resolution stable isotope time series it is anchored by 22 new u th ages and lamina counting yielding a refined age model that supersedes the previous one the sv7 record is anchored by 8 u th ages and spans 13 1 10 5 ka partially overlapping the sv1 record together the morphological and geochemical characteristics of sv1 and sv7 allow us to identify site specific processes driving the isotopic variations this enables us to explore the degree of complacency in speleothems whereby periodically a speleothem is insensitive to recording a climate signal due to aquifer hydrology and network evolution the model suggests that 18o is a proxy for the infiltration amount that reaches the site of deposition which in the case of sv7 was buffered by the aquifer hydrology the interpretation of 13c in both stalagmites is more complex being influenced by both temperature and hydrology only a comparison of the two stalagmite records allows us to recognise a decoupling between the effects of hydrology and temperature according to our interpretation the most distinctive climate information of the younger dryas was the high hydrological variability with phases dominated by seasonal infiltration within an overall cooling trend our record also reveals a significant early holocene climate anomaly centred at 10 4 ka whose magnitude was possibly amplified by local synoptic conditions our research demonstrates the importance of investigating several complementary proxies particularly from morphologically diverse stalagmites when monitoring data are not available fabric and lamina thickness can be fundamental to unravelling the dominant control of hydrology or temperature on stable isotopes

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

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

climatic and environmental controls on speleothem oxygen isotope values variations in speleothem oxygen isotope values d 18 o result from a complicated interplay of environmental controls and processes in the ocean atmosphere soil zone epikarst and cave system as such the controls on speleothem d 18 o values are extremely complex an understanding of the processes that control equilibrium and kinetic fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem d 18 o as paleoclimate and paleoenvironmental proxies and is best complemented by study of site specific cave processes such as infiltration flow routing drip seasonality and saturation state and cave microclimate among others this review is a process based summary of the multiple controls on d 18 o in the atmosphere soil epikarst and speleothem calcite illustrated with case studies primary controls of d 18 o in the atmosphere include temperature and relative humidity through their role in the multiple isotope effects variability and modifications of water d 18 o values in the soil and epikarst zones are dominated by evaporation mixing and infiltration of source waters the isotopically effective recharge into a cave system consists of those waters that participate in precipitation of caco3 resulting in calcite deposition rates which may be biased to time periods with optimal dripwater saturation state recent modeling experimental and observational data yield insight into the significance of kinetic fractionation between dissolved carbonate phases and solid caco3 and have implications for the hendy test to assist interpretation of speleothem d 18 o time series quantitative and semi quantitative d 18 o climate calibrations are discussed with an emphasis on some of the difficulties inherent in using modern spatial and temporal isotope gradients to interpret speleothems as paleoclimate proxy records finally several case studies of globally significant speleothem paleoclimate records are discussed that show the utility of d 18 o to reconstruct past climate

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

delayed hydrological response to greenland cooling at the onset of the younger dryas in western europe during the younger dryas cold event about 12 800 years ago environmental change in western europe seems to occur 170 years after cooling over greenland lake sediment analyses confirm this delay and suggest european hydrological and vegetation change occurred only after the build up of sea ice in the north atlantic pushed the westerly wind system south

paleoclimate variability during the blake geomagnetic excursion mis 5d deduced from a speleothem record abstract to evaluate possible connections between climate and the earth s magnetic field we examine paleoclimate proxies in a stalagmite pa 8 recording the blake excursion 112 116 4 ka from cobre cave n spain trace element 13 c 18 o 234 u fluorescent lamination growth rate and paleomagnetic records were synchronized using a floating lamina counted chronology constrained by u th dates providing a high resolution multi proxy paleoclimate record for mis 5d the alpine cave setting and the combination of proxies contributed to improve the confidence of the paleoclimatic interpretation periods of relatively warm and humid climate likely favored forest development and resulted in high speleothem growth rates arguably annual fluorescent laminae low 13 c and mg and increased sr and ba colder periods limited soil activity and drip water availability leading to reduced speleothem growth poor development of fluorescent lamination enhanced water rock interaction leading to increased mg 13 c and 234 u and episodic flooding in the coldest and driest period recorded evaporation caused simultaneous 18 o and 13 c enrichments and perturbed the trace element patterns the blake took place in a relatively warm interestadial at the inception of the last glacial period but during a global cooling trend recorded in pa 8 by an overall decrease of 18 o and growth rate and increasing mg that trend culminated in the cessation of growth between 112 and 101 ka likely due to the onset of local glaciation correlated with greenland stadial 25 that trend is consistent with a link between low geomagnetic intensity and climate cooling but it does not prove it shorter term changes in relative paleointensity rpi relate to climate changes recorded in pa 8 particularly a prominent rpi low from 114 5 to 113 ka coincident with a significant cooling indicated by all proxy records suggesting a link between geomagnetic intensity and climate at millennial time scales although the reliability of such inference is limited by the inferior resolution of the paleomagnetic data and a possible contamination of the rpi data by unaccounted changes in magnetite concentration the agreement of those data with the marine record of cosmogenic be suggests that the rpi record of pa 8 may reflect truly geomagnetic intensity variations

hydroclimatic changes in the british isles through the last glacial interglacial transition multiproxy reconstructions from the vale of pickering ne england abstract european paleoenvironmental records through the last glacial interglacial transition lgit ca 16 8 cal ka bp record a series of climatic events occurring over decadal to multi centennial timescales changes in components of the climatic system other than temperature e g hydrology through the lgit are relatively poorly understood however and further records of hydroclimatic changes are required in order to develop a more complete understanding on the phasing of environmental and anthropogenic responses in europe to abrupt climate change here we present a multiproxy palaeoenvironmental record macroscale and microscale sedimentology macrofossils and carbonate stable isotopes from a palaeolake sequence in the vale of pickering vop ne england which enables the reconstruction of hydroclimatic changes constrained by a radiocarbon based chronology relative lake level changes in the vop occurred in close association although not necessarily in phase to threshold shifts across abrupt climate change transitions most notably lowering during cooling intervals of the lgit gi 1d gi 1b and gs 1 this reflects more arid hydroclimates associated with these cooling episodes in the british isles comparisons to hydrological records elsewhere in europe show a latitudinal bifurcation with northern europe 50 60 n becoming more arid humid and southern europe 40 50 n becoming more humid arid in response to these cooling warming intervals we attribute these bifurcating signals to the relative positions of the atlantic storm tracks sea ice margin and north atlantic polar front napf during the climatic events of the lgit

time corrections to teleseismic p delays derived from sks splitting parameters and implications for western u s p wave tomography 1 upper mantle anisotropy will affect teleseismic p wave arrival times and create artifacts in isotropic travel time tomography compiled sks splitting results indicate variations in the strength and orientation of azimuthal anisotropy beneath the western u s we use sks splitting parameters and a hexagonally anisotropic elastic tensor fast symmetry axis to estimate azimuthal anisotropy contributions to p wave delay times and evaluate the effects on isotropic p wave tomography estimated anisotropy correction times have a root mean square rms value of 0 16 s which is 37 of p wave delay time rms the magnitude of azimuthal anisotropy rather than its azimuth has the strongest effect on p delay times however if the anisotropy symmetry axis has a plunge p wave travel times may be strongly affected by both magnitude and azimuth applying azimuthal anisotropy corrections significantly increases tomographic p wave velocity beneath the high lava plains and central california coast and decreases velocity beneath the great basin

applications of stalagmite laminae to paleoclimate reconstructions comparison with dendrochronology climatology abstract laminated stalagmites observed in either ultra violet or visible light or recognized via trace elements are now widely recognized as a common deposition form annually laminated stalagmites should be expected in caves which have an overlying climate that has a strong seasonality similar climate zones to where trees grow with distinct annual rings continuous laminated stalagmite chronologies up to several thousand years should be expected where some mixing of stored water occurs such stalagmites can be used to reconstruct climate particularly through variations in lamina width such climate records would be relatively damped by mixing of event water with stored groundwater constraining the amount of high frequency climate signals contained in the stalagmite but relatively long continuous lamina sequences permit the preservation of low frequency centennial scale climate signals this contrasts with numerous tree ring climate records which are frequently limited in preserving multi centennial trends due to the necessary removal of age related noise from relatively short tree segments laminated stalagmites and tree rings should therefore to some degree provide complementary climate information appropriate methods for compiling stalagmite layer chronologies and climatologies are presented

significant seismic anisotropy beneath the southern lhasa terrane tibetan plateau 1 shear wave splitting measurements using teleseismic pks skks and sks phases recorded by station lsa on the southern part of the lhasa terrane of the tibetan plateau reveal significant azimuthal anisotropy with a splitting time of up to 1 5 s a conclusion that is contradictory to previous studies which suggested isotropy or weak anisotropy in addition systematic variations of the splitting parameters fast polarization direction and splitting time with the arriving azimuth of the seismic ray path are observed suggesting a model of anisotropy that is more complicated than a single layer with horizontal axis of symmetry the measurements are consistent with a model with two layers of anisotropy the top layer has a ne sw fast direction which is consistent with gps revealed direction of surface movement and can be associated with lattice preferred orientation of middle lower crustal minerals such as amphibole the lower layer has a nearly e w fast direction and can be the consequence of either the n s directed compressional stress originated from the india eurasia collision or flow in the asthenosphere related to the absolute motion of eurasia this study underlines the importance of a long duration of deployment of seismic stations in resolving complex anisotropy

magnesium and strontium systematics in tropical speleothems from the western pacific abstract we present bulk average sr and mg data for 13 speleothems from different locations in the western equatorial pacific guam solomon islands and vanuatu these data plot on a single straight line in a graph of ln sr ca vs ln mg ca with a slope of 0 9 a 22 000 year record of sr and mg in one of these samples from guam also plots with the same slope suggesting that the process partitioning mg and sr within the guam speleothem is the same as the one that partitions mg and sr between the different pacific speleothems we rule out temperature growth rate detrital phases and sea spray as likely mechanisms for this correlation we construct mathematical models of limestone diagenesis and show that this cannot explain the slope of the correlation our favoured explanation for the correlation is calcite water interaction in the form of prior calcite precipitation pcp and or incongruent calcite dissolution icd we present a formal mathematical model of pcp and prove that the slope of a graph of ln sr ca and ln mg ca is given by kd sr 1 kd mg 1 a similar equation is derived for icd in a companion paper sinclair 2011 using published values for kdsr and kdmg this slope is calculated to be 0 88 in excellent agreement with our observations because the slope is independent of solution and host limestone composition it can be used to diagnose calcite water interaction in individual cave water studies where host rock composition is unknown or in speleothems for which no field drip water data or host rock geochemistry exists approximately half of published drip and speleothem mg sr studies plot within error of this slope we hypothesize that the overall trend in our pacific speleothem data results from the individual dripwater systems evolving from a roughly similar initial rock composition set by late quaternary reef limestone in the guam speleothem the broad peak in mg and sr centred on the early mid holocene reflects a change in hydrology rainfall with the most likely scenario being that dry conditions prevailed on guam at this time

cryptic diagenesis and its implications for speleothem geochronologies abstract speleothems are usually considered as one of the most amenable palaeoclimate archives for u series dating a number of studies in recent years however report cases of diagenetic alteration which compromises the use of u series systematics in speleothems resulting in inaccurate u th ages here we present the results of a high resolution u th dating study of a stalagmite cc26 from corchia cave in italy where we document a number of departures from an otherwise well defined age depth model and explore potential causes for these outliers unlike examples illustrated in previous studies cc26 contains no visible evidence of neomorphism and appears at least superficially ideally suited to dating good reproducibility obtained between multi aliquot u th analyses removes any possibility of analytical issues contributing to these outliers furthermore replicate analyses of samples from the same stratigraphic layer yielded ages in stratigraphic sequence implying very localized open system behavior uranium loss is suggested as a causative mechanism on account of the fact that all the outliers are older than their assumed true age a limited number of micro voids were observed under micro ct analyses and it is proposed that these were pathways for u loss uranium loss modelling allows us to constrain the possible timing of diagenetic alteration and indicates that the precursor for the outlier with the largest age discrepancy 309 must have been aragonite this study indicates that visibly unaltered speleothems may still contain small domains that have experienced post depositional alteration such cryptic diagenesis as recorded in this stalagmite has implications for the constancy of accuracy of the u series dating technique and suggests a need for careful examination of speleothems prior to dating particularly in low resolution u th studies

an abrupt wind shift in western europe at the onset of the younger dryas cold period the younger dryas cold reversal during the last glacial termination is one of the most abrupt climate change events observed in the northern hemisphere analyses of varved lake sediments from western germany suggest that storminess in the north atlantic region increased within a single year at this time providing a mechanistic link between a decrease in the meridional overturning circulation and western european cooling the younger dryas cooling 12 700 years ago is one of the most abrupt climate changes observed in northern hemisphere palaeoclimate records1 2 3 4 annually laminated lake sediments are ideally suited to record the dynamics of such abrupt changes as the seasonal deposition responds immediately to climate and the varve counts provide an accurate estimate of the timing of the change here we present sub annual records of varve microfacies and geochemistry from lake meerfelder maar in western germany providing one of the best dated records of this climate transition5 our data indicate an abrupt increase in storminess during the autumn to spring seasons occurring from one year to the next at 12 679 yr bp broadly coincident with other changes in this region we suggest that this shift in wind strength represents an abrupt change in the north atlantic westerlies towards a stronger and more zonal jet changes in meridional overturning circulation alone cannot fully explain the changes in european climate6 7 we suggest the observed wind shift provides the mechanism for the strong temporal link between north atlantic ocean overturning circulation and european climate during deglaciation

cave air control on dripwater geochemistry obir caves austria implications for speleothem deposition in dynamically ventilated caves there are very few process studies that demonstrate the annual variation in cave environments depositing speleothems accordingly we initiated a monitoring program at the obir caves an austrian dripstone cave system characterized by a seasonally changing air flow that results in a predictable pattern of high pco2 during summer and low pco2 in winter although similar seasonal changes in soil pco2 occur they are not directly connected with the changes in the subsurface since the dripwaters are fed from a well mixed source showing little seasonal variation cold season flushing by relatively co2 poor air enhances degassing of co2 in the cave and leads to a high degree of supersaturation of dripwater with regard to calcite forced calcite deposition during the cold season also gives rise to a pronounced pattern of synchronous seasonal variations in electrical conductivity alkalinity ph ca and 13cdic which parallel variations recorded in 13ccave air chemical components unaffected by calcite precipitation e g d 18o sio2 so4 lack a seasonal signal attesting to a long residence in the karst aquifer modeling shows that degassing of co2 from seepage waters results in kinetically enhanced c isotopic fractionation which contrasts with the equilibrium degassing shown from the soreq cave in israel the obir caves may serve as a case example of a dripstone cave whose seepage waters and speleothems show intra annual geochemical variability that is primarily due to chemical modification of the groundwater by a dynamic bidirectional subsurface air circulation

na sws 1 1 a uniform database of teleseismic shear wave splitting measurements for north america 1 this version of shear wave splitting sws database db for north america na contains 6224 pairs of splitting parameters fast polarization directions and splitting times measured using all the available data recorded by digital broadband seismic stations over the period of 1980 2007 and archived at the incorporated research institutions for seismology data management center the measurements were produced using a set of robust procedures that involve automated batch processing and manual screening and were ranked quantitatively on the basis of a uniform criterion the result is a homogeneous database of individual rather than station averaged splitting parameters that can be used by a variety of geoscientists for the understanding of the structure and dynamics of the earth s deep interior beneath na this data brief describes the seismic data and techniques used to generate the sws results the spatial and azimuthal coverage and the limitations of the db the db will be periodically updated and enhanced by adding newly recorded data and by measuring splitting parameters using the pks and skks phases in addition to sks the database can be accessed at http www mst edu liukh sws

volcanic ash reveals time transgressive abrupt climate change during the younger dryas knowledge of regional variations in response to abrupt climatic transitions is essential to understanding the climate system and anticipating future changes global climate models typically assume that major climatic changes occur synchronously over continental to hemispheric distances the last major reorganization of the ocean atmosphere system in the north atlantic realm took place during the younger dryas yd an 1100 yr cold period at the end of the last glaciation within this region several terrestrial records of the yd show at least two phases an initial cold phase followed by a second phase of climatic amelioration related to a resumption of north atlantic overturning we show that the onset of climatic amelioration during the yd cold period was locally abrupt but time transgressive across europe atmospheric proxy signals record the resumption of thermohaline circulation midway through the younger dryas occurring 100 yr before deposition of ash from the icelandic vedde eruption in a german varve lake record and 20 yr after the same isochron in western norway 1350 km farther north synchronization of two high resolution continental records using the vedde ash layer 12 140 40 varve yr b p allows us to trace the shifting of the polar front as a major control of regional climate amelioration during the yd in the north atlantic realm it is critical that future climate models are able to resolve such small spatial and chronological differences in order to properly encapsulate complex regional responses to global climate change

the role of seasonality in abrupt climate change abstract a case is made that seasonality switches dominated by wintertime were instrumental in abrupt climate changes in the north atlantic region during the last glaciation and into the holocene the primary evidence comes from mismatches between mean annual temperatures from greenland ice cores in comparison with snowline changes in east greenland northern europe and north america the most likely explanation is a shutdown or reduction in strength of the conveyor this allows the spread of winter sea ice across the north atlantic thus causing the northern region to experience much colder winters because they mimic the greenland temperature rather than the snowline signal changes in the atlantic intertropical convergence zone and the asian monsoon may also share a winter linkage with greenland thus the paleoclimate record is consistent with the notion that a huge continental sector of the northern hemisphere stretching from greenland to asia was close to an extreme winter threshold during much of the last glaciation winter climate crossed this threshold repeatedly with marked changes in seasonality that may well have amplified and propagated a signal of abrupt change throughout the hemisphere and into the tropics

younger dryas to early holocene paleoclimate in cantabria n spain constraints from speleothem mg annual fluorescence banding and stable isotope records abstract the younger dryas yd stadial represents the most abrupt climate change of the earth s recent history thus understanding its causes and different local responses is relevant for quaternary paleoclimatology we present a speleothem high resolution proxy record of the lateglacial to early holocene paleoclimate of the cantabrian cordillera n spain a strategic location to evaluate the influence of north atlantic events such as the yd on south western europe fluorescence lamination growth rate stable isotope and mg records from stalagmite sir 1 were dated using an age depth model constrained by u th dates and annual lamina counting the yd is recorded as a prominent positive 13c excursion whose chronology 12 95 0 14 to 11 62 0 16 ka and shape closely agree with the gs 1 stadial as defined in greenland ice supporting the event synchronicity in both areas a colder and drier yd climate limited soil productivity and dripwater availability leading to higher 13c and mg reduced growth rate and virtually absent fluorescence lamination the early yd record until 12 5 ka reflects increasing aridity whereas the late yd from 12 2 ka on shows the opposite trend at the yd boundaries temperature changes influenced the mg record by modifying the mg partition into calcite however this effect was superseded by major changes in dripwater mg ca linked to rainfall variations during the early holocene the arnero sierra was forested and had a relatively warm and humid seasonal climate indicated in sir 1 by higher growth rates lower 13c and mg and well developed fluorescent lamination similar to other high resolution stalagmitic records of the cordillera from 8 5 to 8 0 ka sir 1 reflects a temporary trend of increasing aridity

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

stable isotope variations in modern tropical speleothems evaluating equilibrium vs kinetic isotope effects applications of speleothem calcite geochemistry in climate change studies require the evaluation of the accuracy and sensitivity of speleothem proxies to correctly infer paleoclimatic information the present study of harrison s cave barbados uses the analysis of the modern climatology and groundwater system to evaluate controls on the c and o isotopic composition of modern speleothems this new approach directly compares the 18 o and 13 c values of modern speleothems with the values for their corresponding drip waters in order to assess the degree to which isotopic equilibrium is achieved during calcite precipitation if modern speleothems can be demonstrated to precipitate in isotopic equilibrium then ancient speleothems suitable for paleoclimatic studies from the same cave environment may also have been precipitated in isotopic equilib rium if modern speleothems are precipitated out of isotopic equilibrium then the magnitude and direction of the c and o isotopic offsets may allow specific kinetic and or equilibrium isotopic fractionation mechanisms to be identified carbon isotope values for the majority of modern speleothem samples from harrison s cave fall within the range of equilibrium values predicted from the combined use of 1 calcite water fractionation factors from the literature 2 measured temperatures and 3 measured 13 c values of the dissolved inorganic carbon of drip waters calcite samples range from 0 8 higher to 1 1 lower than predicted values the 13 c depletions are likely caused by kinetically driven departures in the fractionation between hco3 aq and caco3 from equilibrium conditions caused by rapid calcite growth 13 c enrichments can be accounted for by rayleigh distillation of the hco3 aq reservoir during degassing of 13 c depleted co2 modern speleothems from harrison s cave are not in o isotopic equilibrium with their corresponding drip waters and are 0 2 to 2 3 enriched in 18 o relative to equilibrium values 18 o variations in modern calcite are likely controlled by kinetically driven changes in the fractionation between hco3 aq and caco3 from equilibrium conditions to nonequilibrium conditions consistent with rapid calcite growth in contrast to 13 c 18 o values of modern calcite may not be affected by rayleigh distillation during degassing because co2 hydration and hydroxylation reactions will buffer the o isotopic composition of the hco3 aq reservoir if the effects of rayleigh distillation manifest themselves in the o isotopic system they will result in 18 o enrichment in the hco3

precise dating of dansgaard oeschger climate oscillations in western europe from stalagmite data the signature of dansgaard oeschger events millennial scale abrupt climate oscillations during the last glacial period is well established in ice cores and marine records but the effects of such events in continental settings are not as clear and their absolute chronology is uncertain beyond the limit of 14 c dating and annual layer counting for marine records and ice cores respectively here we present carbon and oxygen isotope records from a stalagmite collected in southwest france which have been precisely dated using 234u 230th ratios we find rapid climate oscillations coincident with the established dansgaard oeschger events between 83 000 and 32 000 years ago in both isotope records the oxygen isotope signature is similar to a record from soreq cave israel and deep sea records indicating the large spatial scale of the climate oscillations the signal in the carbon isotopes gives evidence of drastic and rapid vegetation changes in western europe an important site in human cultural evolution we also find evidence for a long phase of extremely cold climate in southwest france between 61 2 0 6 and 67 4 0 9 kyr ago

radiometric isotopic and petrographic evidence of changing interglacials over the past 550 000 years from six stalagmites from the serra do courel in the cordillera cantabrica of northwestern spain abstract seventy u th ages from six stalagmites from the cordillera cantabrica in northwestern spain indicate deposition during interglacial but not glacial stages over the last 550 kyr stable isotope data and petrographic observations suggest that within each interglacial conditions typically progressed from drier to wetter consideration of the most precise u th ages suggests that stalagmite deposition occurred in times more predictable from european pollen records than from the global marine isotope record for example during the last interglacial ages suggest deposition in an interval better characterized as the eemian as opposed to mis 5e and during the st germain i or mis 5c interval the same holds for mis 7 where ages suggest deposition during mis 7a and mis 7c but not mis 7e these age ranges for interglacials consistently later than those suggested by the benthic marine record are compatible with warm conditions maintained by thermohaline circulation that simultaneously supplied the moisture for growing ice sheets of the subsequent glaciation trends both within and across these six stalagmites suggest that cooler temperatures were associated with wetter conditions both during interglacials and in conditions intermediate between interglacials and glacials in northern spain in contrast other researchers results from a stalagmite from the last glacial maximum and subsequent deglaciation suggest colder temperatures were associated with drier conditions the two trends combine to suggest wettest conditions in times intermediate between interglacials and glacials compatible with a model in which modern climatic belts from dry arctic to wet european to dry marginal saharan have moved over northern spain in the cycle from glacial to interglacial times extrapolation to a warmer future would suggest drier conditions in the northern iberian peninsula than those of today