eemian cooling in the norwegian sea and north atlantic ocean preceding continental ice sheet growth changing conditions in the north atlantic region may drive global climate changes1 2 according to previous reconstructions of the last interglacial the eemian north atlantic sea surface tempera tures ssts were similar to present day values3 in the norwegian sea even warmer conditions appeared as a single pulse of short duration4 5 whereas the greenland ice record suggests that the warm interglacial air temperatures were interrupted by several cold periods6 here we use faunal and stable isotope analyses of foraminifera in two sediment cores from the north atlantic ocean and norwegian sea to reconstruct high resolution records of sst and sea surface salinity sss during the eemian interglacial our results which differ significantly from the greenland record6 show a sharp decrease in sst and sss of the norwegian sea associated with a more moderate cooling and freshening of the north atlantic at the middle of isotope substage 5e several millennia before the beginning of continental ice sheet growth changes in the norweg ian sea surface conditions appear to have represented an important climate change affecting global atmospheric and thermohaline circulations

variations in mode of formation and temperature of oceanic deep waters over the past 125 000 years marked changes in the deep water temperature of the different oceanic basins during the past 125 kyr are revealed by a detailed comparison of the oxygen isotopic composition ofbenthicforaminiferafrom sediment cores taken from the norwegian sea and the pacific atlantic and southern oceans the last interglacial deep water temperatures were similar to the modern ones at the 5e 5d transition around 115 kyr bp the deep water temperatures dropped below approximately 0 c in the pacific and southern indian oceans in the atlantic ocean the deep water temperature dropped in 2 successive steps at 115 and 75ky bp the global ocean deep water temperatures were in the 0 to 1 c range for the whole of the last ice age isotope stages 4 2

could deep subantarctic convection feed the world deep basins during the last glacial maximum simple box model calculations are used to simulate the oceanic circulation during the last glacial maximum lgm these experiments show that the main features of the 13c and 14c distributions and of the lysocline depth may be explained by a circulation pattern very different from the modem one intermediate and upper deep waters were produced in the north atlantic ocean whereas deep waters of subantarctic mode type forming at the northern edge of the subantarctic convergence invaded the main oceanic basins the southern ocean mainly self ventilated had a reduced deep component that flew southward along the east pacific ridge and the australian west cost the thermodynamic fractionation that occurs during air sea exchange has only contributed slightly to the glacial deep 13c distribution through surface water temperature variations

planktonic foraminiferal depth habitat and δ18o calibrations plankton tow results from the atlantic sector of the southern ocean varies by several orders of magnitude across a large gradient in sea surface temperature and other hydrographic features demonstrating high sensitivity of foraminiferal populations to regional differences in water properties the depth of maximum abundance for key species such as globigerina bulloides and neogloboquadrina pachyderma is not constant from station to station the pattern suggests that their abundance and shell chemistry are tied to density horizons or other conditions such as food availability that become more sharply defined with depth in the northern subantarctic the consistent observation of globorotalia inflata and globoratalia truncatulinoides as relatively deep dwelling species confirms their utility as indicators of upper thermocline properties in d 18 o all species are observed to be isotopically lighter than predicted from water properties but the species specific offset is fairly uniform at all stations these observations define the utility of multispecies d 18 o for reconstructing temperature and density stratification from past surface oceans index terms 4267 oceanography general paleoceanography 4572 oceanography physical upper ocean processes 4870 oceanography biological and chemical stable isotopes 3030 marine geology and geophysics micropaleontology keywords stratification d 18 o

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

physicochemical characteristics of drip waters influence on mineralogy and crystal morphology of recent cave carbonate precipitates speleothems are one of the most intensively explored continental archives for palaeoclimate variability the parameters however that control speleothem petrography and its changes with time and space specifically calcite crystal morphology and carbonate mineralogy are still poorly understood in order to shed light on processes and their products precipitation experiments of recent carbonate crystals on watch glasses and glass plates were performed in seven selected caves drip water sites were analysed for their fluid mg ca molar ratio ph degree of saturation for calcite and aragonite and drip rates corresponding precipitates were analysed with respect to their mineralogy calcite crystal morphology and mg ca molar ratio of calcite the following results are found high fluid mg ca ratios are found only for caves situated in dolostone thus the hostrock lithology indirectly controls the carbonate mineralogy and calcite crystal morphology of speleothems the precipitation of aragonite in place of calcite occurred only in dolostone caves and is bound to very specific conditions these are high fluid mg ca ratios 0 5 high fluid ph 8 2 and low fluid saturation indices for calcite 0 8 these specific conditions are induced by slow drip rates of 0 2 ml min as often under more arid conditions causing the precipitation of calcite aragonite prior to reaching the stalagmite top due to this fluid chemistry is altered which in turn leads to changes in carbonate mineralogy and geochemistry on the stalagmite top calcite growth is inhibited at high fluid mg ca ratios and hence aragonite precipitation is kinetically stabilised an increase of the drip water mg ca ratio leads to an increased incorporation of mg2 into the calcite crystal lattice and thus to a change in calcite crystal morphology four distinctive changes occur with increasing mg2 incorporation i development of new forms steeper rhombohedra and base pinacoid at the edges and corners of the crystal seed ii crystal habit tend to elongate along 0 0 1 due to slower growth of faces with high mg2 densities iii reconstitution of crystal faces with low mg2 densities and iv occurrence of calcite crystals with bended faces and edges due to very high mg2 mg ca ratios of 0 009 0 051 incorporation growth rates and possibly also organic compounds however may also affect the morphology of calcite crystals based on the data shown here the relation of mg2 incorporation and the resulting changes in calcite crystal morphologies as well as the conditions of aragonite precipitation are now clearly better understood further work should aim at linking the calcite crystal morphology of watch glass precipitates with calcite crystal fabrics in speleothems in order to exploit the petrographic archive of speleothem deposits

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

the last deglaciation in the southern ocean the isotopic and micropaleontological deglacial records of three deep sea cores from 44 s to 55 s have been dated by accelerator mass spectrometry the available records did not allow accurate dating of the initiation of the deglaciation by 13 000 years b p sea surface temperatures reached values similar to the present values a cool oscillation abruptly interrupted this warm phase between 12 000 and 11 000 years b p initiation of this cooling therefore preceded the northern hemisphere younger dryas by approximately 1000 years complete warming was reached by 10 000 years b p more or less synchronous with the northeast atlantic ocean

deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation the degree of similarity of the 13c records of the planktonic foraminiferal species n pachyderma and of the benthic foraminiferal genus cibicides in the high latitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle whereas continuous formation of deep water is recognized in the southern ocean the norwegian sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation however deep water formed in the north atlantic south of the norwegian sea during the last climatic cycle as early as isotope substage 5d and this area was also the only active northern source during stages 4 2 a detailed reconstruction of the geographic distribution of 13c in benthic foraminifera in the atlantic ocean during the last glacial maximum shows that the most important deepwater mass originated from the southern ocean whereas the glacial north atlantic deep water cannot be traced south of 40 n at shallower depth an oxygenated 13c rich intermediate water mass extended from 45 n to 15 s in the pacific ocean a ventilation higher than the modern one was also found in open ocean in the depth range 700 2600 m and is best explained by stronger formation of intermediate water in high northern latitudes

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

cyclic rapid warming on centennial scale revealed by a 2650 year stalagmite record of warm season temperature 1 a 2650 year bc665 ad1985 warm season mjja may june july august temperature reconstruction is derived from a correlation between thickness variations in annual layers of a stalagmite from shihua cave beijing china and instrumental meteorological records observations of soil co2 and drip water suggest that the temperature signal is amplified by the soil organism co2 system and recorded by the annual layer series our reconstruction reveals that centennial scale rapid warming occurred repeatedly following multicentenial cooling trends during the last millennia these results correlate with different records from the northern hemisphere indicating that the periodic alternation between cool and warm periods on a sub millennial scale had a sub hemispherical influence

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

reconstruction of late holocene autumn winter precipitation variability in sw romania from a high resolution speleothem trace element record abstract we present the first high resolution trace element mg ca sr ca ba ca record from a stalagmite in southwestern romania covering the last 3 6 ka which provides the potential for quantitative climate reconstruction precise age control is based on three independent dating methods in particular for the last 250 yr where chemical lamina counting is combined with the identification of the 20th century radiocarbon bomb peak and 230th u dating long term cave monitoring and model simulations of drip water and speleothem elemental variability indicate that precipitation related processes are the main drivers of speleothem mg ca ratios calibration against instrumental climate data shows a significant anti correlation of speleothem mg ca ratios with autumn winter october to march precipitation r 0 61 p during the late holocene our data suggest a heterogeneous pattern of past regional winter hydroclimate in the carpathian balkan realm along with intermittent weakening of the dominant influence of north atlantic forcing in agreement with other regional paleo hydrological reconstructions the observed variability reveals periodically occurring strong nw se hydro climate gradients we hypothesize that this pattern is caused by shifts of the eastern edge of the area of influence of the nao across central eastern europe due to the confluence of north atlantic forcing and other climatic features such as the east atlantic western russia eawr pattern

rainfall and cave water isotopic relationships in two south france sites this article presents isotopic measurements 18o and d of precipitation and cave drip water from two sites in southern france in order to investigate the link between rainfall and seepage water and to characterize regional rainfall isotopic variability these data which are among the longest series in france come from two rainfall stations in south west france le mas 1996 2012 and villars 1998 2012 typically under atlantic influence and from one station in the south east orgnac 2000 2012 under both mediterranean and atlantic influence rainfall isotopic composition is compared to drip water collected under stalactites from the same sites villars cave four drip stations 1999 2012 in the south west and chauvet cave two drip stations 2000 2012 in the south east near orgnac the study of these isotopic data sets allows the following conclusions to be drawn about the rainfall drip water relationships and about rainfall variability 1 the cave drip water isotopic composition does not show any significant changes since the beginning of measurements in order to explain its isotopic signature it is necessary to integrate weighted rainfall 18o of all months during several years which demonstrates that even at shallow depths 10 50 m cave drip water is a mixture of rain water integrated over relatively long periods which give an apparent time residence from several months to up to several years these results have important consequences on the interpretation of proxies like speleothem fluid inclusions and tree ring cellulose isotopic composition which are used for paleoclimatic studies 2 in the villars cave where drip stations at two different depths were studied lower 18o values were observed in the lower galleries which might be due to winter season overflows during infiltration and or to older rain water with a different isotopic composition that reaches the lower galleries after years 3 local precipitation is characterized by local meteoric water lines lmwl with 18o d slopes close to 7 in both areas and correlations between air temperature and precipitation 18o are low at both monthly and annual scales even with temperature weighted by the amount of precipitation 4 the mesoscale climate model remoiso equipped with a water isotope module allows the direct comparison of modeled and observed long term water isotope records the model slightly overestimates rainfall 18o at the respective sampling stations however it simulates very well not only the seasonal rainfall isotopic signal but also some intra seasonal patterns such as a typical double peak 18o pattern in winter time

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

reconstruction of the last deglaciation deconvolved records of δ18o profiles micropaleontological variations and accelerator mass spectrometric14c dating bioturbation acts as a low pass filter in displacing and reducing the amplitudes of stratigraphic signals this often leads to a loss of high frequency events in the stratigraphic record in addition when considering an isotopic signal 18o 14c measured in stratigraphic carriers such as foraminifera bioturbation and carrier abundance changes can create artifacts which may be falsely interpreted as leads or lags in the paleoclimatic record

surface water temperature changes in the high latitudes of the southern hemisphere over the last glacial interglacial cycle a set of numerical equations is developed to estimate past sea surface temperatures sst from fossil antarctic diatoms these equations take into account both the biogeographic distribution and experimentally derived silica dissolution the data represent a revision and expansion of a floral data base used previously and includes samples resulting from progressive opal dissolution experiments factor analysis of 166 samples 124 holocene core top and 42 artificial samples resolved four factors three of these factors depend on the water mass distribution one subantarctic and two antarctic assemblages factor 4 corresponds to a dissolution assemblage inclusion of this factor in the data analysis minimizes the effect of opal dissolution on the assemblages and gives accurate estimates of sst over a wide range of biosiliceous dissolution a transfer function dtf 166 34 4 is derived from the distribution of these factors versus summer sst its standard error is 1 c in the 1 to 10 c summer temperature range this transfer function is used to estimate sst changes in two southern ocean cores 43 s and 55 s which cover the last climatic cycle the time scale is derived from the changes in foraminiferal oxygen and carbon isotopic ratios the reconstructed sst records present strong analogies with the air temperature record over antarctica at the vostok site derived from changes in the isotopic ratio of the ice this similarity may be used to compare the oceanic isotope stratigraphy and the vostok time scale derived from ice flow model the oceanic time scale if taken at face value would indicate that large changes in ice accumulation rates occurred between warm and cold periods

orbital changes and climate at the 41 000 period of orbital tilt summer insolation forces a lagged response in northern ice sheets this delayed ice signal is rapidly transferred to nearby northern oceans and landmasses by atmospheric dynamics these ice driven responses lead to late phased changes in atmospheric co2 that provide positive feedback to the ice sheets and also project late 41 k forcing across the tropics and the southern hemisphere responses in austral regions are also influenced by a fast response to summer insolation forcing at high southern latitudes at the 22 000 year precession period northern summer insolation again forces a lagged ice sheet response but with muted transfers to proximal regions and no subsequent effect on atmospheric co2 most 22 000 year greenhouse gas responses have the early phase of july insolation july forcing of monsoonal and boreal wetlands explains the early ch4 response the slightly later 22 k co2 response originates in the southern hemisphere the early 22 k ch4 and co2 responses add to insolation forcing of the ice sheets the dominant 100 000 year response of ice sheets is not externally forced nor does it result from internal resonance internal forcing appears to play at most a minor role the origin of this signal lies mainly in internal feedbacks co2 and ice albedo that drive the gradual build up of large ice sheets and then their rapid destruction ice melting during terminations is initiated by uniquely coincident forcing from insolation and greenhouse gases at the periods of tilt and precession

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

on the structure and origin of major glaciation cycles 1 linear responses to milankovitch forcing time series of ocean properties provide a measure of global ice volume and monitor key features of the wind driven and density driven circulations over the past 400 000 years cycles with periods near 23 000 41 000 and 100 000 years dominate this climatic narrative when the narrative is examined in a geographic array of time series the phase of each climatic oscillation is seen to progress through the system in essentially the same geographic sequence in all three cycles we argue that the 23 000 and 41 000 year cycles of glaciation are continuous linear responses to orbitally driven changes in the arctic radiation budget and we use the phase progression in each climatic cycle to identify the main pathways along which the initial local responses to radiation are propagated by the atmosphere and ocean early in this progression deep waters of the southern ocean appear to act as a carbon trap to stimulate new observations and modeling efforts we offer a process model that gives a synoptic view of climate at the four end member states needed to describe the system s evolution and we propose a dynamic system model that explains the phase progression along causal pathways by specifying inertial constants in a chain of four subsystems solutions to problems involving systems of such complexity are not born full grown like athena from the head of zeus rather they evolve slowly in stages each of which requires a pause to examine data at great lengths in order to guarantee a sure footing and to properly choose the next step victor p starr

13c record of benthic foraminifera in the last interglacial ocean implications for the carbon cycle and the global deep water circulation the 13c 12c ratios of upper holocene benthic foraminiferal tests genera cibicides and uvigerina of deep sea cores from the various world ocean basins have been compared with those of the modern total carbon dioxide tco2 measured during the geosecs program the 13c difference between benthic foraminifera and tco2 is 0 07 0 04 for cibicides and 0 83 0 07 for uvigerina at the 95 confidence level 13c analyses of the benthic foraminifera that lived during the last interglaciation isotopic substage 5e about 120 000 yr ago show that the bulk of the tco2 in the world ocean had a 13c value 0 15 0 12 lower than the modern one at the 95 confidence level reflecting a depletion compared to the present value of the global organic carbon reservoir regional differences in 13c between the various oceanic basins are explained by a pattern of deep water circulation different from the modern one the antarctic bottom water production was higher than today during the last interglaciation but the eastward transport in the circumpolar deep water was lower

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

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

changes in the vertical structure of the north atlantic ocean between glacial and modern times the distribution of planktic foraminiferal 18o over the north atlantic ocean has been interpreted by duplessy et al 1991 1992 in terms of the distribution of surface water salinity during the last glacial maximum lgm and the younger dryas yd we present here the implications of this surface salinity distribution for changes in deep convection during these periods temperature salinity density diagrams of the water column have been constructed using the plancktic and benthic foraminifera 18o values together with sea surface temperature estimates obtained by using micropaleontological transfer functions the precision of these reconstructions is limited by the remaining uncertainties in the two basic assumptions upon which the methods are based the sea surface temperature reconstruction by climap are valid within the statistical uncertainties the water salinity 18o relationship is well constrained for surface and intermediate ocean waters a significant difference between the modern and the reconstructed glacial water structure is observed during the lgm the modern relatively warm and salty norwegian sea surface water and the north atlantic deep water nadw were replaced by low salinity surface water in the northern atlantic ocean and the norwegian sea and cold deep water 0 1 c however surface water salinity in the central north atlantic ocean 52 54 n 25 40 w was sufficiently high to permit deep water convection as a source of north atlantic intermediate and deep waters open ocean convection at the northern limit of the subtropical surface waters around 40 n may have contributed to the ventilation of the intermediate waters the waters deeper than 2000 m were the result of mixing between poorly oxygenated southern waters and well ventilated north atlantic deep waters a similar reconstruction for the cold yd period indicates that the modern type of circulation with warm and ventilated nadw was largely in operation and that the hydrologic pattern was different from that prevailing during the lgm

a 135 000 year vostok specmap common temporal framework the object of the present study is to introduce a means of comparing the vostok and marine chronologies our strategy has been to use the 18o of atmospheric o2 denoted 18oatm from the vostok ice core as a proxy for the 18o of seawater denoted 18osw our underlying premise in using 18oatm as a proxy for 18osw is that past variations in 18osw an indicator of continental ice volume have been transmitted to the atmospheric o2 reservoir by photosynthesizing organisms in the surface waters of the world s oceans we compare our record of 18oatm to the 18osw record which has been developed from studies of the isotopic composition of biogenic calcite 18oforam in deep sea cores we have tied our 18oatm record from vostok to the specmap timescale throughout the last 135 kyr by correlating 18oatm with a 18osw record from v19 30 results of the correlation indicate that 77 of the variance is shared between these two records we observed differences between the 18oatm and the 18osw records during the coldest periods which indicate that there have been subtle changes in the factors which regulate 18oatm other than 18osw our use of 18oatm as a proxy for 18osw must therefore be considered tentative especially during these periods by correlating 18oatm with 18osw we provide a common temporal framework for comparing phase relationships between atmospheric records from ice cores and oceanographic records constructed from deep sea cores our correlated age depth relation for the vostok core should not be considered an absolute vostok timescale we consider it to be the preferred timescale for comparing vostok climate records with marine climate records which have been placed on the specmap timescale we have examined the fidelity of this common temporal framework by comparing sea surface temperature sst records from sediment cores with an antarctic temperature record from the vostok ice core we have demonstrated that when the southern ocean sst and antarctic temperature records are compared on this common temporal framework they show a high degree of similarity we interpret this result as supporting our use of the common temporal framework for comparing other climate records from the vostok ice core with any climate record that has been correlated into the specmap chronology

the southern ocean surface between marine isotope stages 6 and 5d shape and timing of climate changes summer sea surface temperature ssst and sea ice extent obtained at millennial to centennial resolution are presented for seven cores recovered in the atlantic and western indian antarctic zone from termination ii and the last interglacial s s i e marine isotope substage mis 5e the diatom based ssst estimates show that during the late mis 6 intensified export of cold waters from the weddell sea resulted in sssts close to 0 c in the central and eastern atlantic sector due to northward expansion of the winter sea ice edge by 3 5 latitude the sea ice seasonality was reduced such conditions have great potential for efficient year round reduction in air sea gas exchange and glacial co2 draw down the warming at termination ii started at 132 131 ka marked by rapid retreat of the sea ice edge the ssst increased within a few thousands of years to reach maximum interglacial summer temperatures ranging between 2 5 and 3 5 c in the earliest mis 5e 128 125 ka besides a distinct cold reversal around 129 5 ka the warming was punctuated by short lived temperature rebounds with amplitudes of 1 1 5 c occurring at 200 300 yr frequency thus in the range of the periodicity of solar input increased chaetoceros spp abundance suggests meltwater events as the primary cause of the coolings the ssst optimum characterised by strongly enhanced biogenic sedimentation rates ended at ca 125 ka with the full re establishment of the global conveyor belt and beginning of the northern hemisphere climatic optimum at this time sssts decreased stepwise and stabilised on values slightly warmer than today showing in the following period of mis 5e only low amplitude oscillations during mis 5d a northward expansion of the sea ice field took place but sssts only slightly colder than modern ones and a weakened meridional temperature gradient indicate that the southern ocean did not fall in a true glacial mode the tight correlation between southern ocean ssst and winter sea ice records and vostok atmospheric temperature and co2 records support the idea that the antarctic winter sea ice and southern ocean temperature exert a primary control on the atmospheric ocean co2 exchanges and hence on global climate reduction of the antarctic sea ice field and increase of ssst at the onset of termination ii could have been triggered by precessional changes influencing southern high latitude summer insolation positive feedback mechanisms reduction of surface albedo and release of co2 into the atmosphere and changes in global ocean circulation affected by a collapse or strong reduction in north atlantic deep water nadw production could have induced further reinforcement of the southern ocean warming

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

northern european summer temperature variations over the common era from integrated tree ring density records tree ring chronologies of maximum latewood density are most suitable to reconstruct annually resolved summer temperature variations of the late holocene the two longest such chronologies have been developed in northern europe stretching back to the 2nd century bc and the 5th century ad we show where similarities between the two chronologies exist and combine portions of both into a new summer temperature reconstruction for the common era to minimize the transfer of potential biases we assess the contribution of the candidate reconstructions measurements and exclude data i from exceptionally young and old trees and ii produced by different laboratory technologies our new composite reconstruction reveals warmer conditions during roman medieval and recent times separated by prolonged cooling during the migration period and little ice age twentieth century warmth as indicated in one of the existing density records is reduced in the new reconstruction also affecting the overall millennial scale cooling trend over the late holocene 0 30uc per 1000 years due to the reduced biological memory typical for tree ring density measurements the new reconstruction is most suitable for evaluating the rate and speed of abrupt summer cooling following large volcanic eruptions copyright 2014 john wiley sons ltd

sensitivity of bunker cave to climatic forcings highlighted through multi annual monitoring of rain soil and dripwaters abstract the last two decades have seen a considerable increase in studies using speleothems as archives of past climate variability caves under study are now monitored for a wide range of environmental parameters and results placed in context with speleothem data the present study investigates trends from a seven year long monitoring of bunker cave northwestern germany in order to assess the hydraulic response and transfer time of meteoric water from the surface to the cave rain soil and dripwater were collected from august 2006 to august 2013 at a monthly to bimonthly resolution and their oxygen and hydrogen isotope composition was measured furthermore drip rates were quantified due to different drip characteristics annual mean values were calculated for the drip rates of each drip site correlations of the annual mean drip rate of each site with precipitation and infiltration demonstrate that the annual infiltration and thus the annual precipitation control the inter annual drip rate variability for all except one site the hydraulic response is not delayed on an annual basis all drip sites display identical long term trends which suggests a draining of a common karst reservoir over these seven years of monitoring correlations of soil and dripwater monthly 18o and d values with atmospheric temperature data reveal water transfer times of 3 months to reach a depth of 40 cm soilwater at site bw 2 and 4 months for 70 cm depth soilwater at site bw 1 finally the water reaches the cave chambers 15 to 30 m below land surface after ca 2 5 years consequently a temporal offset of 29 to 31 months ca 2 5 years between the hydraulic response time no time lag on annual basis and the water transfer time time lag of 29 to 31 months was found which is negligible with regard to bunker cave speleothems because of their slow growth rates here proxies recording precipitation infiltration and temperature are registered on a decadal scale variations in drip rate and thus precipitation and infiltration are recorded by 13c and mg ca ratios in speleothem calcite speleothem 18o values reflect both temperature and precipitation signals due to drip rate related fractionation processes we document that long term patterns in temperature and precipitation are recorded in dripwater patterns of bunker cave and that these are linked to the north atlantic oscillation nao

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

late quaternary sea ice history in the indian sector of the southern ocean as recorded by diatom assemblages abstract a modern analog technique mat5201 31 has been applied to fossil diatom assemblages to provide down core estimates of february sea surface temperatures ssts and of sea ice duration over the past 220 000 years at 56 40 s 160 14 e at the core location sea ice progression lagged the sst drop by 1 ka at interglacial glacial transitions and sea ice retreat was almost synchronous to the sst increase at glacial interglacial terminations sea ice increased continuously during glacial periods to reach its maximum extent at the end of glacial times although ssts were almost constant during glacials this indicates that ssts are the major parameter determining the advance and retreat of sea ice at transitions but that the sea ice advance during glacial conditions may be related to positive feedbacks of the ice on albedo air temperature and meridional wind stress the strong correlation r 0 75 between sea ice duration at the core location and the vostok co2 record argues for a control of antarctic sea ice extent on atmospheric co2 concentration via the modification of the ocean to atmosphere gas balance

a comparison of the vostok ice deuterium record and series from southern ocean core md 88 770 over the last two glacial interglacial cycles taking advantage of the fact that the vostok deuterium d record now covers almost two entire climatic cycles we have applied the orbital tuning approach to derive an age depth relation for the vostok ice core which is consistent with the specmap marine time scale a second age depth relation for vostok was obtained by correlating the ice isotope content with estimates of sea surface temperature from southern ocean core md 88 770 both methods lead to a close correspondence between vostok and md 88 770 time series however the coherence between the correlated d and insolation is much lower than between the orbitally tuned 8d and insolation this reflects the lower accuracy of the correlation method with respect to direct orbital tuning we compared the ice and marine records set in a common temporal framework in the time and frequency domains our results indicate that changes in the antarctic air temperature quite clearly lead variations in global ice volume in the obliquity and precession frequency bands moreover the average phase we estimated between the filtered d and insolation signals at precessional frequencies indicates that variations in the southern high latitude surface temperature could be induced by changes in insolation taking place during a large period of the summer in northern low latitudes or winter in southern low latitudes the relatively large lag found between vostok d variations and obliquity driven changes in insolation suggests that variations in the local radiative balance are not the only mechanism responsible for the variability in surface temperature at those frequencies finally in contrast to the cross spectral analysis method used in previous studies the method we use here to estimate the phases can reveal errors in cross correlations with orbitally tuned chronologies

benthic foraminiferal abundance and stable isotope changes in the indian ocean sector of the southern ocean during the last 20kyr paleoceanographic implications abstract benthic foraminiferal faunas and benthic stable isotopes during the last 20 kyr were investigated in core md02 2488 46 28 8 s 88 01 3 e 3420 m water depth from the southeast indian ocean sector of the southern ocean in order to document paleoceanographic changes from the last glacial through deglaciation and into the holocene variations occurred in the accumulation rates species composition diversity and stable isotopes during the last 20 kyr the benthic 18o and 13c records during the last 28 kyr show that no significant deep water circulation changes took place before 15 6 calendar kyr ka the 13c increase at 15 6 ka is interpreted as reflecting the arrival of better ventilated deep waters at the site and is associated with the progressive increase in of miliolids from 15 ka to 0 ka an interval 16 15 ka of low benthic foraminiferal accumulation rates bfars and an increase in the relative abundance of stainforthia complanata deep waters were 2 2 0 4 c colder during the last glacial than at present carbonate dissolution proxies indicate that carbonate dissolution was higher during the last glacial than during the last deglacial and holocene bfars and the percentage of species indicative of high productivity suggest that the flux of organic matter resulting from surface water productivity was generally higher between 20 and 13 ka than between 12 and 0 ka consistent with the observed higher proportion of biosiliceous sediment at 20 14 ka and published records the combined percentages of the two most abundant species alabaminella weddellensis and epistominella exigua phytodetritus species suggest that seasonality of productivity intermittency of primary productivity fluctuated over the last 20 kyr and was higher during the last glacial and deglaciation 20 10 ka compared with the holocene 10 0 ka the relative abundances of a weddellensis and e exigua do not covary over the last 20 kyr an observation also reported from other areas

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

melting history of antarctica during the past 60 000 years marked changes in the surface water hydrology of the southern ocean during the past 60 kyr are revealed by a detailed comparison of the oxygen isotopic composition of planktonic and benthic foraminifera from sediment cores and the surface water temperature estimated by a transfer function derived from the distribution of diatoms in the same sediments from 35 to 17 kyr bp the southern ocean polar front was covered by a melt water lid containing a significant contribution from melting icebergs calved from antarctic ice shelves these icebergs may have originated from a succession of surges of the ice shelves

geochemistry of gases and waters discharged by the mud volcanoes at paterno mt etna italy approximately 20 km south of mt etna craters at the contact between volcanic and sedimentary formations three mud volcanoes discharge co2 rich gases and na cl brines the compositions of gas and liquid phases indicate that they are fed by a hydrothermal system for which temperatures of 100 150 c were estimated by means of both gas and solute geothermometry the hydrothermal system may be associated with co2 rich groundwaters over a large area extending from the central part of etna to the mud volcanoes numerous data on the he ch4 co2 composition of the gases of the three manifestations sampled over the past 5 years indicate clearly that variations are due to separation processes of a co2 rich gas phase from the liquid the effects of these processes have to be taken into account in the interpretation of the monitoring data collected for the geochemical surveillance of etna volcano

regional and global benthic δ18o stacks for the last glacial cycle although detailed age models exist for some marine sediment records of the last glacial cycle 0 150 ka age models for many cores rely on the stratigraphic correlation of benthic 18o which measures ice volume and deep ocean temperature change the large amount of data available for the last glacial cycle offers the opportunity to improve upon previous benthic 18o compilations such as the lr04 global stack not only are the age constraints for the lr04 stack now outdated but a single global alignment target neglects regional differences of several thousand years in the timing of benthic 18o change during glacial terminations here we present regional stacks that characterize mean benthic 18o change for 8 ocean regions and a volume weighted global stack of data from 263 cores age models for these stacks are based on radiocarbon data from 0 to 40 ka correlation to a layer counted greenland ice core from 40 to 56 ka and correlation to radiometrically dated speleothems from 56 to 150 ka the regional 18o stacks offer better stratigraphic alignment targets than the lr04 global stack and furthermore suggest that the lr04 stack is biased 1 2 kyr too young throughout the pleistocene finally we compare global and regional benthic 18o responses with sea level estimates for the last glacial cycle

northeast indian stalagmite records pacific decadal climate change implications for moisture transport and drought in india two types of el nino events are distinguished by sea surface temperature sst anomalies centered in the central or eastern equatorial pacific the central pacific el nino events cp el nino are more highly correlated with weakening of the central indian summer monsoon and linked to decadal pacific climate variability we present a 50 year subannually resolved speleothem 18o record from northeast india that exhibits a significant correlation with northern pacific decadal variability and central equatorial pacific ssts accordingly we suggest that 18o time series in similar northeast indian speleothems are effective tools for investigating preinstrumental changes in pacific climate including changes in el nino dynamics in contrast to central india rainfall amounts in northeast india are relatively unaffected by el nino however back trajectory analysis indicates that during cp el nino events moisture transport distance to northeast india is reduced suggesting that variations in moisture transport primarily control 18o in the region

winter precipitation changes during the medieval climate anomaly and the little ice age in arid central asia abstract the strength of the north atlantic oscillation nao is considered to be the main driver of climate changes over the european and western asian continents throughout the last millennium for example the predominantly warm medieval climate anomaly mca and the following cold period of the little ice age lia over europe have been associated with long lasting phases with a positive and negative nao index its climatic imprint is especially pronounced in european winter seasons however little is known about the influence of nao with respect to its eastern extent over the eurasian continent here we present speleothem records 13c 18o and sr ca from the southern rim of fergana basin central asia revealing annually resolved past climate variations during the last millennium the age control of the stalagmite relies on radiocarbon dating as large amounts of detrital material inhibit accurate 230th dating present day calcification of the stalagmite is most effective during spring when the cave atmosphere and elevated water supply by snow melting and high amount of spring precipitation provide optimal conditions seasonal precipitation variations cause changes of the stable isotope and sr ca compositions the simultaneous changes in these geochemical proxies however give also evidence for fractionation processes in the cave by disentangling both processes we demonstrate that the amount of winter precipitation during the mca was generally higher than during the lia which is in line with climatic changes linked to the nao index but opposite to the higher mountain records of central asia several events of strongly reduced winter precipitation are observed during the lia in central asia these dry winter events can be related to phases of a strong negative nao index and all results reveal that winter precipitation over the central eurasian continent is tightly linked to atmospheric nao modes by the westerly wind systems

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

speleothem calcite farmed in situ modern calibration of δ18o and δ13c paleoclimate proxies in a continuously monitored natural cave system abstract understanding the relationships between speleothem stable isotopes 13 c 18 o and in situ cave forcing mechanisms is important to interpreting ancient stalagmite paleoclimate records cave studies have demonstrated that the 18 o of inorganically precipitated low temperature speleothem calcite is systematically heavier than the 18 o of laboratory grown calcite for a given temperature to understand this apparent offset rainwater cave drip water groundwater and modern naturally precipitated calcite farmed in situ were grown at multiple locations inside hollow ridge cave in marianna florida high resolution micrometeorological air chemistry time series and ventilation regimes were also monitored continuously at two locations inside the cave supplemented with periodic bi monthly air gas grab sample transects throughout the cave cave air chemistry and isotope monitoring reveal density driven airflow pathways through hollow ridge cave at velocities of up to 1 2 m s 1 in winter and 0 4 m s 1 in summer hollow ridge cave displays a strong ventilation gradient in the front of the cave near the entrances resulting in cave air that is a mixture of soil gas and atmospheric co 2 a clear relationship is found between calcite 13 c and cave air ventilation rates estimated by proxies pco 2 and 222 rn calcite 13 c decreased linearly with distance from the front entrance to the interior of the cave during all seasons with a maximum entrance to interior gradient of 13 c caco3 7 a whole cave hendy test at multiple contemporaneous farming sites reveals that ventilation induces a 1 9 0 96 13 c offset between calcite precipitated in a ventilation flow path and calcite precipitated on the edge or out of flow paths this interpretation of the hendy test has implications for interpreting 13 c records in ancient speleothems calcite 13 c caco3 may be a proxy not only for atmospheric co 2 or overlying vegetation shifts but also for changes in cave ventilation due to dissolution fissures and ceiling collapse creating and plugging ventilation windows farmed calcite 18 o was found to exhibit a 0 82 0 24 offset from values predicted by both theoretical calculations and laboratory grown inorganic calcite unlike 13 c caco3 oxygen isotopes showed no ventilation effects i e 18 o caco3 appears to be a function of growth temperature only although we cannot rule out a small effect of unmeasured gradients in relative humidity evaporation accompanying ventilation our results support the findings of other cave investigators that water calcite fractionation factors observed in speleothem calcite are higher that those measured in laboratory experiments cave and laboratory calcite precipitates may differ mainly in the complex effects of kinetic isotope fractionation combining our data with other recent speleothem studies we find a new empirical relationship for cave specific water calcite oxygen isotope fractionation across a range of temperatures and cave environments 1000 ln 16 1 10 3 t 1 24 6 with a fractionation temperature dependence of 18 o t 0 177 c lower than the currently accepted 0 206 c

evidence from southern ocean sediments for the effect of north atlantic deep water flux on climate evidence from southern ocean sediments for the effect of north atlantic deep water flux on climate

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

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

annual growth banding in a cave stalagmite the presence of microscopic luminescence banding in cave calcite deposits speleothems has recently been reported1 3 the luminescence seems to be caused by excitation of humic and fulvic acids derived from the overlying soil and subsequently incorporated into the calcite3 4 we have tested whether such luminescence corresponds to annual growth layers using high precision thermal ionization mass spectrometric 238u 234u 230 th ages from banded sections of a holocene stalagmite we report here that the timespans yielded by counting bands on the assumption that they are annual agree within error limits with those obtained by our uranium thorium dating this demonstration that the banding is annual should make banded speleothems valuable resources for providing high resolution records of past climate in which precipitation can be estimated from growth rates5 6 and temperatures from stable isotope measurements7 and solar terrestrial correlations as the luminescence intensity can be related to the solar sunspot cycle1 3

glacial and holocene stable isotope distributions in the southeastern indian ocean we have reconstructed glacial interglacial variations in cibicidoides wuellerstorfi 13c and 18o in the southeastern indian ocean using depth transects of cores from off western and southern australia we compare these new results with published stable isotope records to constrain glacial interglacial changes in indian ocean chemistry and circulation the strong last glacial maximum lgm deep water 13c depletions previously observed for the northeastern indian ocean did not extend throughout the low latitude glacial indian ocean we observe only a small lgm 13c decrease off southern australia in marked contrast to the strong lgm 13c depletions observed in many cores from the atlantic and western indian sectors of the southern ocean it is not yet clear whether the very low lgm 13c values in the deep northern and southwestern indian ocean are an artifact of surface ocean productivity or whether they reflect real gradients in deep water chemistry

the role of climate and vegetation in weathering and clay mineral formation in late quaternary soils of the swiss and italian alps nteractions between climate and soil remain ambiguous particularly when silicate weathering and clay mineral formation and transformation rates are considered in relation to global climate changes recent studies suggest that climate affects weathering rates much less than previously thought here we show that the climate in the central european alps has a significant but indirect influence on the weathering of soils through vegetation the pattern of element leaching and mineral transformations is not only due to precipitation and temperature element leaching was greatest in subalpine forests near the timberline weathering is lessened at higher and lower altitudes vegetation therefore contributes significantly to weathering processes the highest accumulation of organic matter was found in climatically cooler sites subalpine range where the production of organic ligands which enhance weathering is greatest patterns of smectite formation and distribution had strong similarities to that of the elemental losses of fe and al r 0 69 p 0 01 or base cations r 0 58 p 0 05 higher precipitation rates and the production of organic chelating compounds in the soil promoted the appearance of smectites the relationship between climate element leaching fe al ca mg k na and smectite formation is strongly nonlinear and driven by the podzolisation process which is more pronounced near the timberline because of the bioclimatic constellation climate warming will probably in the future lead to a decrease in som stocks in the subalpine to alpine range because of more favourable conditions for biodegradation that would also affect weathering processes

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

late quaternary sea surface conditions at dsdp hole 594 in the southwest pacific ocean based on dinoflagellate cyst assemblages investigation of organic walled dinoflagellate cyst distribution in 118 surface sediments from the southern ocean documents the relatively high diversity of cyst taxa 46 species and distinct cyst assemblages in relation to surface water masses and temperature gradient the antarctic water is characterised by the dominance of selenopemphix antarctica accompanied by brigantedinium spp and impagidinium pallidum the subantarctic water association consists mainly of nematosphaeropsis labyrinthus impagidinium paradoxum and impagidinium sphaericum whereas the subtropical water association is dominated by operculodinium centrocarpum and spiniferites membranaceus multivariate analyses non metric multidimensional scaling demonstrate the relationships with sea surface conditions and enable the application of the best analogue method on the southern ocean dinoflagellate cyst data base for reconstructing past sea surface conditions the dinoflagellate cyst record from dsdp 594 45 31 41 s 174 56 88 e 1204 m southern margin of the chatham rise shows important fluctuations in species composition from glacial to interglacial over the last 140 000 yr reconstruction of winter and summer ssts reveals much lower temperature than present by 6 to 10 c during marine oxygen isotope stages 6 4 and 2 and higher temperature by 2 3 c during substage 5e copyright 2001 john wiley sons ltd journal of quaternary science

reconstructing palaeoprecipitation from an active cave flowstone several drill cores were obtained from a laminated actively forming flowstone from a shallow cave in austria highly resolved petrographic and geochemical analyses combined with multi annual cave monitoring reveal a distinct sensitivity of flowstone growth and composition to late holocene meteoric precipitation the regular sub millimetre scale lamination consists of thicker translucent laminae and thinner organic inclusion rich laminae there is also a macroscopic millimetre scale banding of darker and lighter bands comprising several laminae stable isotope analyses of drill cores and modern calcite precipitates show a pronounced positive covariation of 13c and 18o values indicative of kinetic isotope effects comparing the isotope values with petrography shows gradual changes across several of the annual laminae i e changes of several per mille on a multi annual to decadal timescale the stable isotope and trace element composition as well as the flowstone petrography are mainly controlled by the variable drip water discharge controlling the water film thickness and water residence time on the flowstone surface and consequently the intensity of co2 degassing kinetic isotope enrichment and concomitant calcite precipitation drill core pfu6 provides an isotope record of the last ca 3000 years at near annual resolution a distinct phase of low c and o isotope values interpreted as increased discharge and hence higher meteoric precipitation occurred from ca 300 to 140 a b2k second half of the little ice age and another wet interval occurred around 700 a corresponding to reported medieval glacier advances the roman warm period was also dominated by relatively wet conditions although significant decadal variability prevailed increased precipitation further characterized the intervals from ca 2480 to 2430 and 2950 to 2770 a dry conditions persisted during the medieval climate anomaly although this trend towards reduced precipitation started earlier the highest c isotope values of the last 2 ka are recorded around 750 a and another dry phase is centred at 1480 a this new record shows that inter annual to decadal oscillations are a dominant mode of variation during the last 3 ka in the alps copyright 2011 john wiley sons ltd

modelling of dripwater hydrology and hydrogeochemistry in a weakly karstified aquifer bath uk implications for climate change studies abstract a better knowledge of dripwater hydrology in karst systems is needed to understand the palaeoclimate implications of temporal variations in mg ca and sr ca of calcareous cave deposits quantitative modelling of drip hydrology and hydrochemistry was undertaken at a disused limestone mine brown s folly mine in sw england overlain by 15 m of poorly karstified jurassic limestones with sub vertical fracturing enhanced by proximity to an escarpment discharge was monitored at 15 sites intermittently from the beginning of 1996 and every 10 20 days from later 1996 to early 1998 samples for hydrochemical parameters ph alkalinity cations anions fluorescence were taken corresponding to a sub set of these data and supplemented by bedrock and soil sampling limited continuously logged discharge and soil water observations three sites covering the range of discharge approximately 1 l s 1 to 1 ml s 1 maximum discharge and hydrochemical behaviours were studied in more detail a quantitative flow model was constructed based on two parallel unit hydrographs responsive and relatively unresponsive to discharge events respectively the linear response and conservative mixing assumptions of the model were tested with hydrogeochemical data dripwaters at many of sites are characterized by evidence of prior calcite precipitation in the flowpath above the mine which in the higher discharging sites diminishes at high flow also at low flow rates dripwaters may access seepage reservoirs enriched in mg and or sr dependent on the site the discharge at all three sites can be approximated by the flow model but in each case hydrochemical data show violations of the model assumptions all sites show evidence of non conservative mixing and there are temporal discontinuities in behaviour which may be stimulated by airlocks generated at low flow enhanced mg ca and sr ca often do relate to low flow conditions but the relationships between climate and hydrogeochemical response are non linear

changes in the oceanic 13c 12c ratio during the last 140 000 years high latitude surface water records detailed records of the carbon and oxygen isotopic ratios of neogloboquadrina pachyderma are compared between nine high latitude sediment cores from the northern and southern hemispheres covering the last 140 000 yrs the strong analogies between the 13c records permit to define a 13c stratigraphic scale with three clear cut transitions simultaneous with the oxygen isotopic transitions 65 125 kyrs 54 65 kyrs and 21 13 kyrs the 13c records of n pachyderma in the high latitude cores which follow the changes in 13c of the surface water tco2 near areas of deep water formation present trends similar to the benthic foraminifera 13c records in cores v19 30 and m12 392 although amplitudes of the isotopic shifts are different this implies that a large part of the observed variations represents global changes in the carbon distribution between biosphere and ocean the 13c12c ratios of n pachyderma in the north atlantic cores display larger regional variations at 18 kyrs b p than at present to explain these differences we have plotted the 18 kyrs b p 13c values of n pachyderma from 17 cores distributed n of 40 n comparison with published surface water temperature distribution at 18 kyrs b p indicates that a strong divergent cyclonic cell centered approximatively 55 n and 15 w was active during most of the last ice age maximum this hydrology analogous to the present weddell sea explains the published evidences of bottom water formation if located on the northern flank of the gyre and the strong polar front on the southern flank probable location of intermediate water formation

investigating the behaviour of mg isotopes during the formation of clay minerals abstract we present elemental and isotopic data detailing how the mg isotope system behaves in natural and experimentally synthesized clay minerals we show that the bulk mg isotopic composition 26 mg of a set of natural illite montmorillonite and kaolinite spans a 2 range and that their isotopic composition depends strongly on a balance between the relative proportions of structural and exchangeable mg after acid leaching these natural clays become relatively enriched in isotopically heavy mg by between 0 2 and 1 6 results of exchange experiments indicate that the mg that has adsorbed to interlayer spaces and surface charged sites is relatively enriched in isotopically light mg compared to the residual clay the isotopic composition of this exchangeable mg 1 49 to 2 03 is characteristic of the isotopic composition of mg found in many natural waters further experiments with an isotopically characterized mgcl 2 solution shows that the clay minerals adsorb this exchangeable mg with little or no isotopic fractionation although we cannot discount the possibility that the uptake of exchangeable mg does so with a slight preference for 24 mg to characterize the behaviour of mg isotopes during clay mineral formation we synthesized brucite mg oh 2 which we consider to be a good analogue for the incorporation of mg into the octahedral sheet of mg rich clay minerals or into the brucitic layer of clays such as chlorite in our experiment the brucite mineral becomes enriched in the heavy isotopes of mg while the corresponding solution is always relatively enriched in isotopically light mg the system reaches a steady state after 10 days with a final fractionation factor solid solution of 1 0005 at near neutral ph this result is consistent with the general consensus that secondary clay minerals preferentially take up isotopically heavy mg during their formation however our results also show that exchangeable mg is an important component within bulk clay minerals and can have an important influence over the bulk clay 26 mg value modeling shows that in certain soils or sediments where the percentage of exchangeable mg is 30 and the isotopic composition of the exchangeable mg is around 2 the generation of bulk 26 mg values of 26 mg values that are closer in composition to the ucc despite this results of modeling together with experimental observation suggests that the uptake of exchangeable mg into these clay rich sediments could cause a decrease in the bulk 26 mg value by up to 0 3 0 4 this should be accounted for when assessing the 26 mg value of sediments on a crustal scale

seasonal resolution of eastern mediterranean climate change since 34 ka from a soreq cave speleothem the combination of ion microprobe analysis of d 18 o and confocal laser fluorescent microscope imaging of annual growth bands in a soreq cave speleothem provides sub annual scale climate information between 34 and 4 ka this high resolution methodology is ideal both for comparing seasonal climate patterns across broad windows of time and examining rapid climate events such as the younger dryas termination in detail the sub annual d 18 o gradients we report represent a combination of seasonal variability in rainfall amount and air temperature a distinct change in both the pattern of fluorescent banding and the gradient of d 18 o measured in situ across single annual growth bands indicates a change in seasonal climate patterns of the eastern mediterranean region following heinrich event 1 and again after the younger dryas throughout the holocene wet winters and dry summers characterized regional climate during the younger dryas we find that regional climate may have been more arid than in the holocene but the fluorescent banding pattern indicates that the supply of dripwater to the cave was more consistent year round we suggest that a reduced gradient of seasonal precipitation occasional snowfall and vegetation differences may have all contributed to the isotope and fluorescent banding patterns observed during heinrich event 1 and the last glacial stadial detailed investigation of the younger dryas termination reveals a rapid onset of regional environmental change fluorescent band counting indicates that the younger dryas termination as recorded by rainfall in the

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

a 53 year seasonally resolved oxygen and carbon isotope record from a modern gibraltar speleothem reconstructed drip water and relationship to local precipitation abstract the response of a climate proxy against measured temperature rainfall and atmospheric circulation patterns at sub annual resolution is the ultimate test of proxy fidelity but very few data exist showing the level of correspondence between speleothem climate proxies and the instrumental climate record cave sites on the gibraltar peninsula provide a unique opportunity to calibrate speleothem climate proxies with the longest known available precipitation isotopes and instrumental records an actively growing speleothem sampled from new st michaels cave in 2004 is composed of paired laminae consisting of light columnar calcite and a darker microsparitic calcite stable isotope analysis of samples micromilled in 100 m steps at the equivalent of bi monthly intervals reveals fabric correlated annual cycles in carbon isotopes oxygen isotopes and trace elements responding to seasonal changes in cave microclimate hydrology and ventilation patterns calcite 13 c values reach a minimum in the light columnar fabric and evidence from trace element behaviour and cave monitoring indicates that this grows under cave winter conditions of highest p co 2 whereas the dark microsparitic calcite characterised by elevated 13 c and 18 o values grows under low summer p co 2 conditions drip water 13 c dic reaches a minimum in march april at which time the attenuated 18 o signal becomes most representative of winter precipitation an age model based on cycle counting and the position of the 14 c bomb carbon spike yields a precisely dated winter oxygen isotope proxy of cave seepage water for comparison with the gnip and instrumental climate record for gibraltar the 18 o characteristics of calcite deposited from drip water representing winter precipitation for each year can be derived from the seasonally resolved record and allows reconstruction of the 18 o drip water representing winter precipitation for each year from 1951 2004 these data show an encouraging level of correspondence r 2 0 47 with the 18 o of rainfall falling each year between october and march and on a decadal scale the 18 o of reconstructed winter drip water mirrors secular change in mean winter temperatures

transfer functions between diatom assemblages and surface hydrology in the southern ocean interpretation of the distribution of 31 marine diatom species and two silicoflagellate genera in 28 core tops from the atlantic and west indian sectors of the southern ocean by q mode factor analysis allows definition of three significantly different floral assemblages one associated with subantarctic and two with antarctic waters these three areas are clearly delineated by prominent oceanographic limits the antarctic convergence and the maximum retreat of sea ice during the summer season a set of palaeoecological transfer functions is derived by comparison between the distribution of these associations and surface water hydrological parameters using these equations estimated summer temperatures from core top floral assemblages range from 12 c in the north of the study area to 2 0 c near the southernmost cores the standard errors of estimate are 1 1 c for summer temperatures 1 5 months year for sea ice cover 0 2 mg atp l for sea surface phosphate concentrations numerical tests of these paleoecological equations demonstrate their usefulness to reconstruct the evolution of the surface oceanography of the austral ocean at different periods of the last climatic cycle

interhemispheric moisture transport in the indian ocean summer monsoon data model and model model comparisons exchange of energy and mass between the ocean and the atmosphere is an integral component of indian ocean summer monsoon dynamics most previous general circulation model simulations of the monsoon have prescribed sea surface temperature sst thus severely constraining atmosphere ocean energy exchanges here we compare model physics based on both prescribed and computed sst simulations to observed climate links between northern hemisphere monsoon strength and the cross equatorial transport of moisture latent heat from the southern subtropical indian ocean for the computed sst case stronger southern hemisphere southeast trades and colder southern subtropical ssts are associated with increased cross equatorial moisture flux increased moisture flux induces strengthened monsoon circulation via increased condensational heating and decreased sea level pressure over asia for the prescribed sst case stronger southeast trades and colder southern subtropical ssts are also associated with increased cross equatorial moisture flux and hence strengthened monsoon circulation however in this case the increased moisture flux is induced by strengthened cross equatorial winds associated with subsidence over the cold southern hemisphere ssts i e increased sea level pressure in the southern subtropics thus the model physics associated with changes in monsoon strength are very different for the prescribed and computed sst simulations only the computed sst simulation replicates observed meteorological relationships

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

past hydrographic and climatic changes in the subantarctic zone of the south atlantic the pleistocene record from odp site 1090 abstract pleistocene summer sea surface temperatures ssst have been reconstructed on a composite core section recovered in the subantarctic zone of the southern ocean from planktonic foraminifers applying the modern analog technique the composite consists of core ps2489 2 and the sections recovered at odp site 1090 and documents the last 1 83 ma three distinct climatic periods can be identified that mirror the pleistocene development of the southern ocean hydrography cold climatic conditions prevailed at 43 s during glacial as well as during interglacial periods during the early pleistocene 1 83 0 87 ma indicating a northward shift of isotherms that characterize the present day polar front zone by about 7 of latitude evidence shows a strong linkage between southern ocean and low latitude climate during that interval time between the mid pleistocene revolution ca 0 9 ma and the mid brunhes event ca 0 4 ma we observe higher amplitude fluctuations in the ssst between glacial and interglacial periods corresponding to the temperature range between the present polar front and subantarctic front these climatic variations have been related to changes in the northern hemisphere ice sheets the past 0 4 ma are characterized by strong ssst variations of up to 8 c between glacials and interglacials only during the climatic optima stages 11 3 9 3 7 5 7 1 5 5 and the early holocene ssst exceeded present ssst at the core locality 10 2 c although the carbonate dissolution record exhibits high variability during the pleistocene it can be shown that ssst estimates were not significantly biased the mid brunhes dissolution cycle as well as the mid pleistocene enhanced carbonate preservation appear to belong to a global long term variability in carbonate preservation

high resolution stratigraphic correlation of benthic oxygen isotopic records spanning the last 300 000 years abstract in order to compare the response of different oceanographic regions to global climate change very detailed stratigraphic techniques are required the global signal of ice volume changes recorded in the oxygen isotopic composition of foraminifera can provide the tool for developing the necessary high resolution stratigraphy in order to evaluate the resolution of a stratigraphy based on detailed isotopic records two techniques are used to correlate a set of benthic oxygen isotope records from seven piston cores taken in the north and south atlantic the indian and the equatorial and north pacific oceans the first technique was modified from the graphic correlation procedure of shaw 1964 this procedure requires the identification of isotopic events that are correlated from core to core detailed correlations for intervals of the cores between events are provided by a series of straight line segments connecting all common events the second technique developed by martinson et al 1982 uses inverse procedures to define a continuous non linear mapping function that correlates the isotopic records the mapping function maximizes the correlation coefficient between data sets being compared the techniques are independent in that they rely on different criteria for correlating the data series stratigraphic correlations obtained by these procedures are in excellent agreement the mean difference between the correlations is on the order of the sampling intervals of each core and when corrected for sedimentation rates suggests that benthic isotope records from the suite of seven cores can be correlated to a resolution of 2000 to 4000 yrs

changes in the distribution of δ13c of deep water σco2 between the last glaciation and the holocene carbon isotopic measurements on the benthic foraminiferal genus cibicidoides document that mean deep ocean 13c values were 0 46 lower during the last glacial maximum than during the late holocene the geographic distribution of 13c was altered by changes in the production rate of nutrient depleted deep water in the north atlantic during the late holocene north atlantic deep water with high 13c values and low nutrient values can be found throughout the atlantic ocean and its effects can be traced into the southern ocean where it mixes with recirculated pacific deep water during the glaciation decreased production of north atlantic deep water allowed southern ocean deep water to penetrate farther into the north atlantic and across low latitude fracture zones into the eastern atlantic mean southern ocean 13c values during the glaciation are lower than both north atlantic and pacific 13c values suggesting that production of nutrient depleted water occurred in both oceans during the glaciation enriched 13c values in shallow cores within the atlantic ocean indicate the existence of a nutrient depleted water mass above 2000 m in this ocean

late quaternary palaeoceanography of the circumpolar deep water from the south tasman rise we use sediment cores from the south tasman rise str to reconstruct deepwater circulation in the southwest pacific sector of the southern ocean sediment cores md972106 45 09 s 146 17 e 3310 m water depth and gc34 45 06 s 147 45 e 4002 m water depth preserve records covering the last 160 k yr with chronology controlled by calibrated accelerator mass spectrometry radiocarbon dates and benthic foraminiferal 18o tied to specmap the stir benthic foraminiferal 13c records provide new 13c values for southern ocean deep water spanning the last 160 kyr at sites unlikely to be affected by variations in productivity the records establish that glacial benthic foraminifera cibicidoides spp 13c values are lower relative to interglacial values and are comparable to previous glacial benthic 13c records in the indian and pacific sectors of the southern ocean comparisons of the benthic foraminiferal 13c time series at the str are made with the equatorial pacific v19 30 and site 846 and the equatorial atlantic geob1115 the similarity of benthic 13c records at the str to the equatorial pacific suggest the southern ocean deep water mass closely tracked those of the deep pacific and the presence of a 13c gradient between the str and the equatorial atlantic suggests there was continual production of northern source deep water over the past 160 k yr

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

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

were glacial iceberg surges in the north atlantic triggered by climatic warming high resolution physical mineralogical sedimentological and micropalaeontological studies were carried out on north atlantic cores from the reykjanes ridge at 59degreesn and from the region southwest of the faeroe islands all core sites are situated along the pathway of iceland scotland overflow water isow and the various parameters measured display similar features previously identified carbonate oscillations keigwin and jones 1994 j geophys res 99 12397 12410 in the time span back to the marine isotope stage 5 4 transition and late glacial lithic events bond and lotti 1995 science 267 1005 1010 such as the heinrich ice rafting events are all represented in the core records long term trends and higher frequency changes in isow intensity were reconstructed on the basis of various independent proxy records the long term trends in circulation match theoretical orbitally forced insolation changes our observed links between ice rafted detritus ird input variations in sea surface temperature sst and circulation at greater depth point to the need to re examine the origin of ird events we suggest that these events may have been triggered by enhanced partly sub surface heat transport to the north enhanced northward heat transport may have caused bottom melting of floating outlet glaciers and ice shelves leading to increased iceberg discharge and ice sheet destabilization this discharge resulted in lower sst s and a lower temperature over greenland thus as shown by our records this scenario implies a temporary de coupling of surface processes and circulation at greater depth a key feature is the occurrence of a saw tooth pattern in the marine data which is similar to the greenland ice core records moreover the warming theory of ird events would explain the observed out of phase relationship between the greenland and antarctic ice core records and also the rapid establishment of higher temperatures over greenland immediately after the cold phases stadials of the dansgaard oeschger cycles less

dripwater organic matter and trace element geochemistry in a semi arid karst environment implications for speleothem paleoclimatology a series of four short term infiltration experiments which revealed hydrochemical responses relevant to semi arid karst environments were carried out above cathedral cave wellington new south wales nsw australia dripwater samples were collected at two sites for trace element and organic matter analysis organic matter was characterised using fluorescence and interpreted using a parafac model three components were isolated that represented unprocessed soil derived humic like and fulvic like material processed humic fulvic like material and tryptophan like fluorescence principal component analysis pca performed on the entire dataset comprising trace element concentrations and parafac scores revealed two dominant components that were identified as soil and limestone bedrock the soil component was assigned based on significant contributions from the parafac scores and additionally included ba cu ni and mg the bedrock component included the expected elements of ca mg and sr as well as si the same elemental behaviour was observed in recent stalagmite growth collected from the site our experiments demonstrate that existing paleoclimate interpretations of speleothem mg and sr developed in regions of positive water balance are not readily applicable to water limited environments we provide a new interpretation of trace element signatures unique to speleothems from water limited karst environments

simulating speleothem growth in the laboratory determination of the stable isotope fractionation δ13c and δ18o between h2o dic and caco3 abstract here we present novel cave analogue experiments directly investigating stable carbon and oxygen isotope fractionation between the major involved species of the carbonate system hco3 co2 caco3 and h2o in these experiments which were performed under controlled conditions inside a climate box a thin film of solution flew down an inclined marble or glass plate after different distances of flow and thus residence times on the plate ph electrical conductivity supersaturation with respect to calcite precipitation rate as well as the 18o and 13c values of the dissolved inorganic carbon dic and the precipitated caco3 were obtained progressive precipitation of caco3 along the plate is accompanied by degassing of co2 and stable isotope fractionation and the system is driven out of isotope equilibrium we observe a strong enrichment of the 13c values with increasing residence time and a smaller enrichment in 18o the temporal evolution of the 18o and 13c values of both the dic and the precipitated caco3 can be explained by a rayleigh fractionation model but the observed enrichment in 13c values is much larger than expected based on isotope equilibrium fractionation factors our setup enables to determine the fractionation between caco3 and hco3 i e ecaco3 hco3 carbon isotope fractionation 13ecaco3 hco3 is strongly negative for all experiments and much lower than equilibrium isotope fractionation 0 1 in addition 13ecaco3 hco3 decreases with increasing residence time on the plate and thus decreasing supersaturation with respect to calcite thus isotope fractionation depends on precipitation rate and consequently occurs under kinetic conditions this is in contrast to previous studies which found no rate dependence and no or even a positive carbon isotope fractionation between caco3 and hco3 oxygen isotope fractionation 18ecaco3 hco3 is also negative and dependent on precipitation rate since no literature values for 18ecaco3 hco3 are available we calculated 18ecaco3 hco3 using equilibrium oxygen isotope fractionation factors between water and calcite and water and hco3 respectively at the beginning of the plate the fractionation is in agreement with the fractionation calculated using fractionation factors determined in cave systems the observed fractionation between caco3 and water 1000ln18 is also in good agreement with the values determined in cave systems and shows a very similar temperature dependence 1000 ln 18 16 516 1 267 10 3 t 26 141 4 356 however with progressive precipitation of caco3 along the plate the system is forced out of isotope equilibrium with the water and 1000ln18 increases the large negative rate dependent isotope fractionations observed in this study suggest that precipitation of speleothem calcite is strongly kinetically controlled and may thus have a large effect on speleothem 18o and 13c values since these values may erroneously be interpreted as reflecting changes in past temperature precipitation and or vegetation density these results have important implications for paleoclimate reconstructions from speleothems

hydrographic changes of the southern ocean southeast indian sector over the last 230 kyr hydrographical changes of the southern indian ocean over the last 230 kyr is reconstructed using a 17 m long sediment core md 88 770 46 01 s 96 28 e 3290m the oxygen and carbon isotopic composition of planktonic n pachyderma sinistra and g bulloides and benthic cibicidoides wuellerstorfi epistominella exigua and melonis barleeanum foraminifera have been analysed changes in sea surface temperatures sst are calculated using diatom and foraminiferal transfer functions a new core top calibration for the southern ocean allows an extension of the method developed in the north atlantic to estimate paleosalinities duplessy et al 1991 the age scale is built using accelerator mass spectrometry ams 14c dating of n pachyderma s for the last 35 kyr and an astronomical age scale beyond changes in surface temperature and salinity clearly lead by 3 to 7 kyr deep water variations thus changes in deep water circulation are not the cause of the early response of the surface southern ocean to climatic changes we suggest that the early warming and cooling of the southern ocean result from at least two processes acting in different orbital bands and latitudes 1 seasonality modulated by obliquity affects the high latitude ocean surface albedo sea ice coverage and heat transfer to and from the atmosphere 2 low latitude insolation modulated by precession influences directly the atmosphere dynamic and related precipitation evaporation changes which may significantly change heat transfer to the high southern latitudes through their control on latitudinal distribution of the major frontal zones and on the conditions of intermediate and deep water formation

a comparison of radiolarian and foraminiferal paleoecology in the southern indian ocean new evidence for the interhemispheric timing of climatic change the deglacial transition between oxygen isotope stages 6 and 5e about 127 000 yr b p is marked by both oxygen isotopic depletion and estimated sea surface temperature sst increase in two subantarctic indian ocean cores the data show synchroneity between warming of foraminifera based sst estimates and depletion of 18o but an earlier warming trend on the basis of radiolarian sst estimates these data have been previously interpreted to indicate that the high latitude southern ocean warms prior to significant melting of glacial age ice sheets comparison of core top assemblages with surface and subsurface conditions in the southern indian ocean reveals that 1 a three part foraminiferal zonation reflects the surface hydrographic regime with abrupt faunal transitions at two major fronts the subtropical convergence stc and the antarctic polar front apf and 2 a two part radiolarian zonation coincides with a two part subsurface hydrographic regime with an abrupt faunal transition corresponding to the southern terminus of subtropical lower water stlw between the stc and the apf it is suggested that shifts of these surface and subsurface regimes are recorded by these foraminiferal and radiolarian assemblages in this interpretation the observed lead of radiolarian sst with respect to 18o indicates an early response to a southward shift of stlw while the later foraminiferal sst warming indicates a southward shift of the stc thus the origin of the southern hemisphere sst lead may be related to stlw which emanates from the subtropical gyres rather than the polar regions

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

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

on the structure and origin of major glaciation cycles 2 the 100 000 year cycle climate over the past million years has been dominated by glaciation cycles with periods near 23 000 41 000 and 100 000 years in a linear version of the milankovitch theory the two shorter cycles can be explained as responses to insolation cycles driven by precession and obliquity but the 100 000 year radiation cycle arising from eccentricity variation is much too small in amplitude and too late in phase to produce the corresponding climate cycle by direct forcing we present phase observations showing that the geographic progression of local responses over the 100 000 year cycle is similar to the progression in the other two cycles implying that a similar set of internal climatic mechanisms operates in all three but the phase sequence in the 100 000 year cycle requires a source of climatic inertia having a time constant similar to 15 000 years much larger than the other cycles similar to 5 000 years our conceptual model identifies massive northern hemisphere ice sheets as this larger inertial source when these ice sheets forced by precession and obliquity exceed a critical size they cease responding as linear milankovitch slaves and drive atmospheric and oceanic responses that mimic the externally forced responses in our model the coupled system acts as a nonlinear amplifier that is particularly sensitive to eccentricity driven modulations in the 23 000 year sea level cycle during an interval when sea level is forced upward from a major low stand by a milankovitch response acting either alone or in combination with an internally driven higher frequency process ice sheets grounded on continental shelves become unstable mass wasting accelerates and the resulting deglaciation sets the phase of one wave in the train of 100 000 year oscillations whether a glacier or ice sheet influences the climate depends very much on the scale the interesting aspect is that an effect on the local climate can still make an ice mass grow larger and larger thereby gradually increasing its radius of influence

δ18o seasonality of planktonic foraminifera from southern ocean sediment traps latitudinal gradients and implications for paleoclimate reconstructions abstract the oxygen isotopic record obtained from globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s was analysed for 5 sediment traps moored in the southern ocean and southwest pacific the traps extend from subtropical to the polar frontal environments providing the first analysis of seasonal foraminiferal 18 o records from these latitudes comparison between the foraminiferal records and various equations for predicted 18 o of calcite reveals that the predicted 18 o is best captured by the equations of epstein et al 1953 epstein s buchsbaum r lowenstam h a urey h c 1953 revised carbonate water isotopic temperature scale geological society of america bulletin 64 1315 1326 and kim and o neil 1997 kim s t o neil j r 1997 equilibrium and non equilibrium oxygen isotope effects in synthetic carbonates geochimica et cosmochimica acta 61 3461 3475 the epstein equation shows a constant offset from the 18 o of g bulloides and n pachyderma s across the full range of latitudes the seasonal range in 18 o values for these two species implies a near surface habitat across all sites while g inflata most likely dwells at 50 m depth a significant finding in this study was that offsets from predicted 18 o for g bulloides do not correlate to changes in the carbonate ion concentration this suggests that co 3 2 in and of itself may not capture the full range of carbonate chemistry conditions in the marine system this sediment trap deployment also reveals distinct seasonal flux patterns for each species comparison between flux weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint at the 51 s site g bulloides has a spring flux peak while n pachyderma s is dominated by summer production the imprint of these differing seasonal production patterns on the flux weighted 18 o values results in more depleted 18 o for n pachyderma s than for g bulloides interpretations of n pachyderma s isotopic composition as a record of subsurface conditions may therefore need to be refined with implications for interpretation of depleted glacial 13 c for this species sigman boyle 2000 sigman d m boyle e a 2000 glacial interglacial variations in atmospheric carbon dioxide nature 407 859 869

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

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr