the 8 2 ka event from greenland ice cores we present a collection of high resolution chemistry and stable isotope records from the plateau of the greenland ice cap during the cold event 8200 yr ago using a composite of four records the cold event is observed as a 160 5 yr period during which decadal mean isotopic values were below average within which there is a central event of 69 yr during which values were consistently more than one standard deviation below the average for the preceding period four cores in north south and central greenland show differences at decadal and shorter timescales it is not yet clear if this represents significant spatial differences in response the results show clear evidence for colder temperatures and a decrease in snow accumulation rate however the changes in chemical concentrations for the ions looked at here are small suggesting only minor changes in atmospheric circulation for this event apart from the decrease in methane concentration greenland ice cores give only weak evidence for effects outside the north atlantic region

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

seasonal variations in sr mg and p in modern speleothems grotta di ernesto italy sub annual variations in trace element chemistry and luminescence have recently been demonstrated from speleothems and offer the potential of high resolution palaeoclimatic proxies however no studies have yet examined microscopic trace element variations in relation to modern cave conditions in this study the spatial variations in trace element sr mg and p concentrations in speleothems a stalagmite and a soda straw stalactite from the alpine ernesto cave temperature 6 6 0 1 c in a forested catchment in ne italy have been studied using secondary ion mass spectrometry sims and compared with environmental parameters and waters in the modern cave an annual lamination exists in the stalagmite and soda straw stalactite in the form of clear calcite with narrow visible layers which are uv fluorescent and interpreted to contain soil derived humic fulvic acids washed into the cave during autumn rains microanalyses were undertaken of seven annual laminae probably deposited during the 1960s in the stalagmite and seven laminae in the 1990s for the stalactite the analysis results show that sr consistently has a trough and p a peak centred on the inclusion rich layer mg shows mainly a negative covariation with sr in laminae formed in the 1990s but a positive covariation in the stalagmite formed in 1960s the spatial scale of the main geochemical variations is the same as that of annual laminae of inclusion poor and inclusion rich couplets mass balance arguments are used to show that the p is inorganic in form and presumably occurs as individual phosphate ions within the calcite most drip waters show limited chemical variations but a summer peak in trace elements in 1995 and a decrease in mg ca in the following winter are notable more pronounced covariations in mg ca and sr ca are shown by a site with highly variable drip rates where ratios increase at slow drip rates the strongest seasonal variations are found in pool waters where ratios increase reflecting significant ca removal from the water into the calcite during the winter in response to seasonal pco2 variations in cave air thus the cave waters compositions tend to reflect climate conditions such that mg ca and sr ca are tentatively interpreted to be higher when climate conditions are dry combining results from the speleothems and cave water along with the behaviour of each trace species mg ca variations in the speleothems are considered to reflect their variation in the cave waters whereas sr incorporation is also dependent on precipitation rate in this case mainly controlled by temporal variations in pco2 in the cave and conceivably also by inhibitors such as phosphate p adsorption a fraction of which is subsequently incorporated within calcite depends on aqueous phosphate concentration and water flux both of which should increase during the autumn therefore multiple trace element profiles in speleothems reflect multiple aspects of environment seasonality and conditions and hence a calibration against weather records is desirable to establish their palaeoclimatological meaning the strong annual variation of trace elements and particularly p can provide chronological markers for high resolution studies of other climate proxies such as stable isotopes

cold event at 8200 yr b p recorded in annually laminated lake sediments in eastern europe a quantitative annual mean temperature reconstruction from an annually laminated lake sediment sequence in estonia eastern europe shows a distinct cold period at 8400 8080 yr b p before a d 2000 the timing is consistent with that seen in the greenland ice core data and various high resolution records from western europe during maximal cooling at 8250 8150 yr b p the annual mean temperature in estonia was 2 0 c colder than prior to and 3 0 c colder than after the cooling the pollen stratigraphic and sedimentological data suggest especially cold and snowy winter conditions the duration and amplitude of the cold event agree with the modeled impact of a sudden freshening of the north atlantic surface water and subsequent perturbation of the thermohaline circulation provided that the cold event was caused by a pulse of freshwater from the melting laurentide ice sheet to the north atlantic the results indicate a strong teleconnection between the north atlantic oceanic forcing and the east european climate at least up to long 26 e mediated probably by the changing intensity of the zonal atmospheric circulation

stratigraphic evidence for a pluvial phase between ca 8200 7100 ka from renella cave central italy a stratigraphic and chronological study of the upper level of renella cave apuan alps central italy reveals that two episodes of flowstone accumulation bracket a thick clastic layer deposited between ca 8 2 and 7 1 ka this layer which represents a period of enhanced cave flooding is substantially in phase with an interval of depleted oxygen isotope values previously recorded in a stalagmite from nearby corchia cave interpreted to have resulted from an increase in local precipitation these data confirm that during this period of time the region experienced relatively wetter conditions including an increase in high magnitude events capable of invading the higher passages of renella cave the timing of the clastic phase occurred when the eastern mediterranean experienced deposition of sapropel layer s1 which is thought to reflect the stagnation of sea water produced largely by enhanced flood activity along the nile in response to increased monsoon intensity in northern equatorial africa recent estimates suggest that s1 may have lasted from ca 10 8 to ca 6 1 ka cal bp combined evidence from renella and corchia cave indicates that the period corresponding to the wettest phase in the apuan alps was much shorter than this and suggests that there is no straightforward connection between increased advection of water vapour from the atlantic between 8 2 and 7 1 ka as recorded in the corchia and renella records and monsoon driven enhancement of nile discharge and s1 deposition in the eastern mediterranean

lake agassiz outburst age and routing by labrador current and the 8 2 cal ka cold event abstract catastrophic drainage of glacial lake agassiz impounded by the laurentide ice sheet lis into hudson bay and strait is widely thought to have caused the 8 2 cal ka cold event though the path of its drainage in the north atlantic is poorly known analysis and compilation of 10 sediment cores from 8 sites distributed on the eastern canadian continental shelf and upper slope south of hudson strait revealed distinct beds with elevated detrital carbonate dc concentrations known by their distinct composition to originate from erosion of carbonate bedrock and carbonate rich glacial sediments in the hudson bay hudson strait region at all but one site radiocarbon ages bracketing and within the thickest and most widespread of these beds are coeval with the age constraints for the agassiz floods in hudson strait and southeastern hudson bay the dc distribution and concentration of this bed are consistent with southward transport in the labrador current transfer function analysis of dinoflagellate assemblage data from cores on the central labrador shelf in hudson bay and on the northeast newfoundland shelf reveal that early holocene seasonal ice cover was 5 6 months longer than at present requiring the application of a 200 year reduction to the radiocarbon age constraints on the lake agassiz outburst floods the age of the floods is reduced to about 8 33 cal ka 7 5 14 c ka from the previous determination of 8 47 cal ka 7 7 14 c ka with a similar reduction in their error ranges to 8 04 8 49 cal ka from 8 16 8 74 cal ka based on present current routing the agassiz floodwaters and icebergs are inferred to have travelled south in the labrador current and to have possibly become incorporated into the north atlantic current and transported to the nordic seas there the freshwater additions would have lessened deepwater production with a concomitant reduction in northward heat transport in the upper limb of the atlantic meridional overturning circulation thereby contributing to the 8 2 cal ka cold event variation in the calcite and dolomite content of the agassiz dc bed two salinity reductions during agassiz bed deposition and low level shorelines of lakes agassiz and ojibway suggest that more than one outburst was delivered during the final agassiz drainage the 8 2 cal ka cold event registered in greenland was coeval with a second or later flood which possibly accompanied the final collapse of the lis in hudson bay

steady state behaviour of the black ven mudslide the application of archival analytical photogrammetry to studies of landform change the concept of dynamic equilibrium has provided geomorphologists with a challenging paradigm for studying landform evolution but quantitative evidence for its existence has proved illusive particularly for complex geomorphological systems the authors believe that the principle has now been verified through the application of the archival photogrammetric technique to a sequence of historical photographs spanning 50 years of process at the black ven mudslide complex in dorset u k the principles and limitations of the archival photogrammetric technique are described the method is applied to oblique and vertical aerial photographs of black ven at five epochs commencing in 1946 continuing at approximately 10 year intervals until 1988 the technique is used to generate plans contours sections and a dense and accurate digital elevation model dem of the whole site at each epoch this is used to generate dems of difference and a distribution of slope angle which suggest that the mudslides are in equilibrium despite the removal of 200 000 m3 of sediment between 1958 and 1988 extrapolation of the slope distribution through time suggests that the frequency of an episodic landform change model at black ven may be approximately 60 years

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

persistent positive north atlantic oscillation mode dominated the medieval climate anomaly the medieval climate anomaly mca was the most recent pre industrial era warm interval of european climate yet its driving mechanisms remain uncertain we present here a 947 year long multidecadal north atlantic oscillation nao reconstruction and find a persistent positive nao during the mca supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker nao conditions into the little ice age lia globally distributed proxy data suggest that this nao shift is one aspect of a global mca lia climate transition that probably was coupled to prevailing la nina like conditions amplified by an intensified atlantic meridional overturning circulation during the mca

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

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

an absolute paleotemperature record from 10 to 6 ka inferred from fluid inclusion d h ratios of a stalagmite from vancouver island british columbia canada abstract by using continuous helium flow during the crushing of calcite speleothem samples we are able to recover liberated inclusion waters without isotopic fractionation a paleotemperature record for the jacklah jill cave locality vancouver island bc was obtained from a 30 cm tall stalagmite that grew 10 3 6 3 ka ago using 18 o values of the crushed calcite and of the inclusion water as inferred from its d it is found that the locality experienced mean annual temperature variations up to 11 c over a 4 ka period in the early holocene at the beginning of the period local temperature quickly increased from a minimum of 1 c to around 10 c but this early climate optimum about 3 c warmer than today only lasted for 1200 years about 8 6 ka ago temperature had declined to 7 c approximately the same as the modern cave temperature since then the study area has experienced only minor temperature fluctuations but there was a brief fall to 4 c at around 7 ka ago which might be caused by a short lived expansion of local alpine glaciers the long term t dependence of d was 1 47 c identical to the value in modern precipitation

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

fluid inclusion and carbon isotope studies of quartz graphite veins black hills south dakota and ruby range montana abstract fluid inclusions and graphite are intimately associated in quartz veins that cut high grade metamorphic rocks in the black hills south dakota and at the crystal graphite mine in the southwestern ruby range montana measured fluid inclusion compositions and volumetric properties were compared with calculated compositions of graphite saturated fluids and with estimates of metamorphic p t conditions and carbon isotope ratios of graphite were measured to evaluate possible sources of carbon in veinforming fluids fluid inclusions from the two areas contrast markedly in their reliability as recorders of metamorphic fluid compositions and metamorphic conditions the 13 c of graphite associated with the veins indicates that the source of carbon was also different in the two areas in the black hills veins fluid inclusions are dominantly h 2 o co 2 mixtures with 24 96 mol co 2 and a maximum of 5 mol n 2 and 13 mol ch 4 isochores for the highest density inclusions pass near estimated peak metamorphic conditions 550 600 c 4 5 6 5 kbar and fluid inclusion compositions are compatible with thermodynamic predictions for fluids in equilibrium with graphite in the stated p t range at geologically reasonable o 2 graphite in a 12 cm wall rock alteration zone adjacent to one of the veins has uniform 13 c of 20 8 0 2 indicating that carbon in the vein forming fluid was derived largely from reduced organic carbon in the ruby range peak metamorphic conditions were higher 750 850 c 5 8 kbar in contrast to the black hills veins fluid inclusions are almost all co 2 ch 4 mixtures with unknown n 2 content many contain 20 equivalent mol ch 4 and mixed h 2 o co 2 inclusions were observed in only one sample inclusions in one vein have 84 97 mol ch 4 virtually all inclusion compositions are incompatible with computed graphite equilibria and inclusion isochores likewise do not pass through estimated metamorphic conditions the density and composition of most if not all inclusions have been modified subsequent to original trapping possibly through h 2 o loss the range of 13 c values of vein graphites 5 8 to 8 6 is nearly indistinguishable from values for graphite in dolomitic marble near the veins 4 8 to 7 1 carbon was probably mobilized through devolatilization reactions in the marble and precipitated as 13 c rich graphite in the veins at fairly constant temperature and from fluid of fairly constant composition

surface and deep ocean interactions during the cold climate event 8200 years ago evidence from a north atlantic deep sea sediment core reveals that the largest climatic perturbation in our present interglacial the 8200 year event is marked by two distinct cooling events in the subpolar north atlantic at 8490 and 8290 years ago an associated reduction in deep flow speed provides evidence of a significant change to a major downwelling limb of the atlantic meridional overturning circulation the existence of a distinct surface freshening signal during these events strongly suggests that the sequenced surface and deep ocean changes were forced by pulsed meltwater outbursts from a multistep final drainage of the proglacial lakes associated with the decaying laurentide ice sheet margin

freshwater outbursts to the oceans from glacial lake agassiz and their role in climate change during the last deglaciation abstract lake agassiz was the largest lake in north america during the last deglaciation as the laurentide ice sheet lis retreated large volumes of water stored in this proglacial lake were episodically released into the oceans these waters were variably routed to the gulf of mexico arctic ocean north atlantic ocean and hudson bay during this period the three largest cooling events in the northern hemisphere closely followed 4 of the 5 largest outbursts from lake agassiz 1 the younger dryas which was preceded by a release of 9500 km 3 2 the preboreal oscillation preceded by releases of 9300 km 3 and 5900 km 3 and 3 the 8 2 ka cold event preceded by a 163 000 km 3 outburst these are respectively fluxes of 0 30 sv 0 29 sv 0 19 sv and 5 2 sv if released in 1 year because the influx of freshwater reaching the north atlantic ocean can inhibit thermohaline circulation partly depending on whether the ocean was in a glacial interglacial or transitional mode of circulation we believe that at least these large outbursts from lake agassiz may have provided the triggers for changes in ocean circulation and in turn for widespread climate change

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

high resolution reconstruction of 8 2 ka bp event documented in pere noel cave southern belgium a distinct shift in 18o 13c and trace element contents of the pere noel pn stalagmite from southern belgium revealed an abrupt climatic anomaly at 8 13 0 03 ka bp before present before 1950 ad this anomaly is characterized by a maximum drop in the 18o 1 4 compared the mean between 8 13 and 8 10 ka bp 0 03 this drop of 18o coincides with a decrease in 13c and trace element sr ba and mg concentrations suggesting drier conditions our precise chronology provides the timing of the outburst of proglacial lakes agassiz and ojibway that caused the 18o 13c and trace elemental anomalies at 8 13 8 10 0 03 ka bp which corresponds to the 8 2 ka bp event the pn stalagmite bears 18o values in fluid inclusions that covary with the 18o values in calcite suggesting that the speleothem calcite 18o primarily reflects variations in the rainfall 18o comparison of the pn record with different marine and terrestrial archives during the 8 2 ka bp event shows a good agreement in timing and duration suggesting that the pn speleothem can be regarded as a valuable proxy to better understand the 8 2 ka bp event

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

enhanced rainfall in the western mediterranean during deposition of sapropel s1 stalagmite evidence from corchia cave central italy a stable isotope record from a stalagmite collected from antro del corchia cave apuan alps central italy supported by 17 uranium series ages indicates enhanced regional rainfall between ca 8 9 and 7 3 kyr cal bp at the time of sapropel s1 deposition within this phase the highest rainfall occurred between 7 9 and 7 4 kyr cal bp comparison with different marine and lake records and in particular with the soreq cave record israel suggests substantial in phase occurrence of enhanced rainfall between the western and eastern mediterranean basins there is no convincing evidence for major climatic change at the time of the 8 2 kyr event

changing moisture sources over the last 330 000 years in northern oman from fluid inclusion evidence in speleothems speleothems from hoti cave in northern oman provide a record of continental pluvial periods over the last 330 000 yr periods of rapid speleothem deposition occurred from 6000 to 10 500 78 000 to 82 000 120 000 to 135 000 180 000 to 200 000 and 300 000 to 330 000 yr ago with little or no growth during the intervening periods during each of these five pluvial periods d values of water extracted from speleothem fluid inclusions dfi are between 60 and 20 vsmow and 18o values of speleothem calcite 18oc are between 12 and 4 to vpdb these values are much more negative than modern rainfall for d or modern stalagmites for 18o previous work on the isotopic composition of rainfall in oman has shown that northern and southern moisture sources are isotopically distinct combined measurements of the d values of fluid inclusion water with calculated 18o values from peak interglacial speleothems indicate that groundwater was predominantly recharged by the southern indian ocean moisture source when the monsoon rainfall belt moved northward and reached northern oman during each of these periods

a high resolution fluid inclusion δ18o record from a stalagmite in sw france modern calibration and comparison with multiple proxies abstract the 18 o of speleothem fluid inclusions can provide information about local climate and the atmospheric circulation if the fate of oxygen isotopes from precipitation to the stalagmite is well understood at villars cave sw france the present day relationship between the 18 o of precipitation and the 18 o of cave drip water has been determined by previous monitoring studies in this article we examine the link between drip water and fluid inclusions in speleothems from the same cave and investigate whether the fossil water in the stalagmites provides a record of the isotopic composition of precipitation replicated fluid inclusion isotope measurements d and 18 o from two modern calcite samples which had precipitated under the monitored stalactites are in agreement with the corresponding contemporaneous drip waters the drip water in turn represents average pluri annual precipitation this gives strong evidence that the isotopic composition of the infiltrating water is preserved in the pores of speleothem calcite thus providing a record of average precipitation 18 o at the site furthermore we measured isotope ratios in fluid inclusions in the stalagmite vil stm1 a 2300 year old sample with a high growth rate up to 0 6 mm yr 1 and a high water content which allows a high resolution reconstruction of the drip water isotopic composition covering the last two millennia the stalagmite is well dated by 13 u th ages and the counting of annual growth layers the fluid inclusion 18 o varies by 2 with high 18 o values in medieval times and low values during the little ice age indicating a temperature influence on precipitation 18 o however temperature change alone cannot account for the full range of variability observed other proxies measured in the same stalagmite indicate that the cave environment has undergone substantial changes during this period stable isotopes and trace element concentrations in calcite show large variations with amplitudes similar to those found in other villars speleothems during large climatic shifts such as dansgaard oeschger events or glacial interglacial transitions in the context of the last 2000 years the proxy variability cannot be attributed to climate alone but is likely influenced by anthropogenic deforestation and the associated changes in carbon dynamics and hydrology these changes might also have an influence on the isotope ratios in drip water relative to precipitation e g through an altered evaporation transpiration ratio nevertheless despite some common trends in all proxy records the marked shifts in the other proxies are not seen in the fluid inclusion stable isotopes which gives evidence that the relationship between precipitation and drip water 18 o in the past was similar to present day conditions and not much affected by the anthropogenic impact a replication of the fluid inclusion isotope record using stalagmites from the same region will be necessary to determine whether local cave processes or large scale temperature and atmospheric circulation dominate the fluid inclusion 18 o signal and in how far the fluid inclusions can provide a direct record of precipitation 18 o

high resolution isotope records of early holocene rapid climate change from two coeval stalagmites of katerloch cave austria abstract two coeval stalagmites from katerloch cave show pronounced intervals of low 18o values around 8 2 9 1 and 10 0 kyr all ages are reported before the year 2000 ad and represent an inorganic u th dated climate archive from the southeast of the european alps a region where only very few well dated climate records exist the o isotope curves providing near annual resolution allow a direct comparison to the greenland ice core records as temperature was the primary factor controlling the o isotopic composition of katerloch speleothems the 8 2 kyr climate anomaly lasted about one century from 8196 to 8100 yr with a maximum amplitude of 1 1 at 8175 yr the event is characterized by a rapid onset and a more gradual demise and u th data as well as annual lamina counting support a rapid climate change towards cooler conditions within 10 20 yr there is no strong evidence that the 8 2 kyr anomaly was superimposed on a pronounced longer term cooling episode nor do the new data support two separate cooling events within the 8 2 kyr event as reported by other studies our record also shows a distinct climate anomaly around 9 1 kyr which lasted 70 110 yr and showed a maximum amplitude of 1 0 i e it had a similar duration and amplitude as the central 8 2 kyr event compared to the 8 2 kyr event the 9 1 kyr anomaly shows a more symmetrical structure but onset and demise still occurred within a few decades only the different progression of the 8 2 asymmetrical and 9 1 kyr anomaly symmetrical suggests a fundamental difference in the trigger and or the response of the climate system moreover both stalagmites show evidence of a climate anomaly around 10 0 kyr which was of comparable magnitude to the two subsequent events using a well constrained modern calibration between air temperature and 18o of precipitation for the study area and cave monitoring data confirming speleothem deposition in katerloch reflecting cave air temperature a maximum cooling by ca 3 c can be inferred at 8 2 and 9 1 kyr which is similar to other estimates e g from lake ammersee north of the alps the o isotopic composition of meteoric precipitation however is a complex tracer of the hydrological cycle and these temperature estimates do not take into account additional effects such as changes in the source area or synoptic shifts apart from that the relative thickness of the seasonally controlled lamina types in the katerloch stalagmites remains rather constant across the intervals comprising the isotopic anomalies i e the stalagmite petrography argues against major shifts in seasonality during the early holocene climate excursions

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

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

lake agassiz final drainage event in the northwest north atlantic 1 the 8 2 ka climate event recorded in greenland ice cores is subject of debates with respect to causal linkage with a collapse of the atlantic meridional overturning due to the drainage of the late glacial lake agassiz here we present records from the nw north atlantic down current the flood discharge route showing that the 9 5 8 ka interval was marked by a succession of events the drainage itself corresponds to a twin layer of carbonate rich turbidites deposited within the calibrated 8 35 8 5 ka interval proxies of sea surface and deep current conditions do not indicate significant concomitant changes in the nw north atlantic the dataset however supports the concept that the 8 2 ka climate event may represent one of the manifestations of climate instability during an interval with major changes of land drainage in ne america due to the collapse of the laurentide ice sheet subsequent fast sea level rise and large scale reorganization of the north atlantic thermohaline circulation pattern

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

the recovery and isotopic measurement of water from fluid inclusions in speleothems the isotopic composition of speleothems is a useful palaeoclimatic indicator but its value would be enhanced if information on the composition of the parent dripwaters could be recovered from fluid inclusions in the speleothem calcite to develop a robust method for extracting and measuring oxygen and hydrogen isotopic composition of fluid inclusions we have used anhydrous iceland spar and microlitre glass capillaries of water as an analogue system crushing the capillary and calcite together in a high vacuum cell we have investigated the adsorbtive and isotopic behaviour of water when exposed to clean fracture surfaces significant water adsorption occurs at room temperature accompanied by large negative isotopic shifts of both oxygen and hydrogen in the recovered foe water at h2o caco3 mass ratios c for 60 min totally desorbs the water and allows retrieval of the correct isotopic composition application of these methods to a british late holocene speleothem yields delta o 18 and delta h 2 compositions for the inclusion water which are closely comparable with the modern cave dripwaters and local precipitation the results show that isotopic compositions can be recovered from inclusion samples of l equivalent to approximately ig of calcite with precisions that are useful for palaeoclimatic research 0 4 for delta o 18 and 3 for delta h 2 greater precision than this will require replicate analysis for each speleothem growth increment copyright c 2001 elsevier science ltd

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

the 8200 cal yr bp event reflected in the arctic fjord van mijenfjorden svalbard detailed stratigraphic investigations of a high resolution sediment core from the arctic fjord van mijenfjorden svalbard reveal significant reductions in benthic foraminiferal 18o of 0 4 and 0 2 0 3 dated to c 8200 and 8450 cal yr bp respectively these reductions combined with changes in the benthic foraminiferal fauna and ird indicate substantial changes in the hydrography of the fjord such as freshening of the bottom water enhanced sea ice distribution and reduced biogenic production the age and duration 100 years of the youngest event is directly in phase with the 8200 cal yr anomaly in the 18o record gisp2 and ngrip of the greenland ice sheet the changes around 8450 cal yr bp compare well to the timing of the initial freshwater drainage of the proglacial lake agassiz therefore the proxy record of van mijenfjorden lends support to the theory explaining the 8200 cal yr bp event as a cumulative response to a freshwater forced reduction in the meridional overturning circulation in

freshwater forcing of abrupt climate change during the last glaciation large millennial scale fluctuations of the southern margin of the north american laurentide ice sheet occurred during the last deglaciation when the margin was located between about 43 and 49 n fluctuations of the ice margin triggered episodic increases in the flux of freshwater to the north atlantic by rerouting continental runoff from the mississippi river drainage to the hudson or st lawrence rivers we found that periods of increased freshwater flow to the north atlantic occurred at the same time as reductions in the formation of north atlantic deep water thus providing a mechanism for observed climate variability that may be generally characteristic of times of intermediate global ice volume