a model based interpretation of low frequency changes in the carbon cycle during the last 120 000 years and its implications for the reconstruction of atmospheric δ14c a main caveat in the interpretation of observed changes in atmospheric d14c during the last 50 000 years is the unknown variability of the carbon cycle which together with changes in the 14c production rates determines the 14c dynamics a plausible scenario explaining glacial interglacial dynamics seen in atmospheric co2 and d13c was proposed recent ly kohler et al 2005 a similar approach and expanding its interpretation to the 14c cycle is an important step towards a deeper understanding of d14c variability this approach is based on an ocean atmosphere biosphere box model of the global carbon cycle bicycle to reproduce low freque ncy changes in atmospheric co2 as seen in antarctic ice cores the model is forced forward in time by various paleo climatic records derived from ice and sediment cores the simulation results of our proposed scenario match a compiled co2 record from various ice cores during the last 120 000 years with high accuracy r2 0 89 we analyze scenarios with different 14c production rates which are either constant based on 10be measured in greenland ice cores or the recent high resolution geomagnetic field reconstruction glopis 75 and compare them with the available d14c data covering the last 50 000 years our results suggest that during the last glacial cycle in general less than 110 o oo of the increased atmospheric d14c are based on variations in the carbon cycle while the largest part 5 6 of the variations has to be explained by other factors glacial atmospheric d14c larger than 700 o oo cannot not be explained within our framework neither through carbon cycle based changes nor through variable 14c production superimposed on these general trends might lie positive anomalies in atmospheric d14c of 50 o oo caused by millennial scale variability of the northern deep water production during heinrich events and dansgaard oeschger climate fluctuations according to our model the dominant processes that increase glacial d14c are a reduced glacial ocean circulation 40 o oo a restricted glacial gas exchange between the atmosphere and the surface ocean through sea ice coverage 20 o oo and the enrichment of dic with 14c in the surface waters through isotopic fractionation during higher glacial marine export production caused by iron fertilization 10 o oo

responses of ocean circulation and carbon cycle to changes in the position of the southern hemisphere westerlies at last glacial maximum 1 we explore the impact of a latitudinal shift in the westerly wind belt over the southern ocean on the atlantic meridional overturning circulation amoc and on the carbon cycle for last glacial maximum background conditions using a state of the art ocean general circulation model we find that a southward northward shift in the westerly winds leads to an intensification weakening of no more than 10 of the amoc this response of the ocean physics to shifting winds agrees with other studies starting from preindustrial background climate but the responsible processes are different in our setup changes in amoc seemed to be more pulled by upwelling in the south than pushed by downwelling in the north opposite to what previous studies with different background climate are suggesting the net effects of the changes in ocean circulation lead to a rise in atmospheric pco2 of less than 10 atm for both northward and southward shift in the winds for northward shifted winds the zone of upwelling of carbon and nutrient rich waters in the southern ocean is expanded leading to more co2outgassing to the atmosphere but also to an enhanced biological pump in the subpolar region for southward shifted winds the upwelling region contracts around antarctica leading to less nutrient export northward and thus a weakening of the biological pump these model results do not support the idea that shifts in the westerly wind belt play a dominant role in coupling atmospheric co2 rise and antarctic temperature during deglaciation suggested by the ice core data

glacial interglacial temperature change in the tropical west pacific a comparison of stalagmite based paleo thermometers in the tropics geochemical records from stalagmites have so far mainly been used to qualitatively reconstruct changes in precipitation but several new methods to reconstruct past temperatures from stalagmite material have emerged recently i liquid vapor homogenization of fluid inclusion water ii noble gas concentrations in fluid inclusion water iii the partitioning of oxygen isotopes between fluid inclusion water and calcite and iv the abundance of the 13 c 18 o 16 o clumped isotopologue in calcite we present for the first time a direct comparison of these four paleo thermometers by applying them to a fossil stalagmite covering nearly two glacial interglacial cycles marine isotope stages mis 12 9 and to two modern stalagmites all from northern borneo the temperature estimates from the different methods agree in most cases within errors for both the old and recent samples reconstructed formation temperatures of the recent samples match within 2 sigma errors with measured cave temperatures however slight but systematic deviations are observed between noble gas and liquid vapor homogenization temperatures whereas the temperature sensitivity of fluid inclusion 18 o and clumped isotopes is currently debated we find that the calibration of tremaine et al 2011 for fluid inclusion 18 o and a synthetic calcite based clumped isotope calibration ziegler et al in prep yield temperature estimates consistent with the other methods all methods with the potential exception of clumped isotopes show excellent agreement on the amplitude of glacial interglacial temperature change indicating temperature shifts of 4 5 c this amplitude is similar to the amplitude of mg ca based regional sea surface temperature records when correcting for sea level driven changes in cave elevation our reconstruction of tropical temperature evolution over the time period from 440 to 320 thousand years ago ka adds support to the view that climate sensitivity to varying greenhouse forcing is substantial also in the deep tropics

southwest pacific deep water carbonate chemistry linked to high southern latitude climate and atmospheric co2 during the last glacial termination abstract a greater amount of co2 was stored in the deep sea during glacial periods likely via greater efficiency of the biologic pump and increased uptake by a more alkaline ocean reconstructing past variations in seawater carbonate ion concentration a major component of alkalinity enables quantification of the relative roles of different oceanic co2 storage mechanisms and also places constraints on the timing magnitude and location of subsequent deep ocean ventilation here we present a record of deep water inorganic carbon chemistry since the last glacial maximum lgm 19 23 ka bp derived from sediment core rr0503 83 raised from 1627 m in new zealand s bay of plenty the core site lies within the upper limit of southern sourced circumpolar deep water cdw just below the lower boundary of antarctic intermediate water aaiw we reconstruct past changes in bottom water inorganic carbon chemistry from the trace element and stable isotopic composition of calcite shells of the epibenthic foraminifer cibicidoides wuellerstorfi a record of co 3 2 co 3 2 co 3 2 i n s i t u co 3 2 saturation derived from the foraminiferal boron to calcium ratio b ca provides evidence for greater ice age storage of respired co2 and reveals abrupt deglacial shifts in co 3 2 i n s i t u of up to 30 mol kg 5 times larger than the difference between average lgm and holocene values the rapidity of these changes suggests the influence of changing water mass structure and atmospheric circulation in addition to a decrease in co2 content of interior waters

wetland expansion on the continental shelf of the northern south china sea during deglacial sea level rise abstract to identify environmental causes for past changes in vegetation in subtropical east asia we present carbon isotope compositions of plant wax n alkanes and provide estimates of the c4 plant contribution across the past four glacial terminations and interglacials based on cores recovered from the northern south china sea our results show a comparable c4 plant contribution between the last glacial maximum lgm and the holocene an increase of the c4 plant contribution by 15 20 is found for terminations iv ii and i relative to subsequent interglacial peaks coeval with an expansion of cyperaceae and poaceae in contrast termination v reveals a lower c4 plant contribution than marine isotope stage mis 11c the data exhibit a long term trend with a stepwise increase of the c4 plant contribution across interglacials mis 11c 9e 7e and 1 we suggest that no substantial changes in humidity levels over glacial interglacial cycles occurred facilitating a similar c3 c4 plant ratio for the lgm and the holocene instead deglacial sea level rises caused an extensive development of floodplains and wetlands on the exposed continental shelf providing habitats for the spread of c4 sedges and grasses the progressive subsidence of chinese coastal areas and the broadening of the continental shelf over the late quaternary explains the nearly absence of c4 plant occurrence during termination v and a gradual increase of the c4 plant contribution across interglacial peaks taken together changes in coastal environments should be considered when interpreting marine based vegetation reconstructions from subtropical asia

last glacial interglacial productivity and associated changes in the eastern arabian sea abstract we reconstruct paleo productivity and bottom water oxygenation changes during the past 32 ka from the southeastern arabian sea using absolute abundance of planktic foraminifera relative abundance of globigerina bulloides angular asymmetrical benthic foraminifera aabf measurements of total organic carbon c org caco 3 and globigerinoides ruber 18 o and 13 c the faunal and geochemical proxies suggest that productivity in the southeastern arabian sea was high during mis 3 a distinct decrease in productivity is inferred during the last glacial maximum 19 23 ka lgm bottom water was well oxygenated during mis3 only to become oxygen depleted during the lgm productivity decreased abruptly during heinrich stadial 1 hs 1 but the response to heinrich stadial 2 hs 2 was different low productivity during the early deglaciation is also synchronous with an increase in ice volume corrected 18 o 18 o sw ivc a salinity proxy between 18 9 18 3 18 9 ka bp and 15 9 15 0 16 3 ka bp and a concomitant decrease in 13 c between 18 2 17 5 18 7 ka bp and 16 4 15 3 16 7 ka bp these patterns suggest that the global 13 c minimum event during the last deglaciation was associated with the weak monsoon interval during hs 1 and a drop in productivity in tropical regions a progressive increase in productivity is observed throughout the holocene with a distinct jump at 5 4 3 8 6 3 ka bp we infer that although productivity was higher in the eastern arabian sea during most of the last glacial interval the overall resultant carbon sequestration was confined only to a restricted zone and not large enough to substantially alter atmospheric co 2

tracing the strength of the southwest monsoon using boron isotopes in the eastern arabian sea here we present the first boron isotope based pco2sw pco2 of seawater reconstruction from the eastern arabian sea using the planktic foraminifera species globigerinoides ruber our results from sediment core aas9 21 show that pco2sw varied between 160 and 300 atm during the last 23 kyr the pco2 the sea air pco2 difference is relatively small during the last glacial maximum and becomes more negative toward the holocene with the exception of a significant excess during the last deglaciation centered on the bolling allerod throughout the record pco2 is predominantly negative probably as a result of enhanced biological productivity and higher nutrient and carbon utilization during the southwest monsoon a reduction in pco2 during the last glacial maximum is therefore consistent with a reduction in the strength of this monsoon system

the ice age carbon puzzle between about 24 000 years ago and today the large ice sheets covering most of canada and parts of europe and asia melted away sea level rose by 120 m earth warmed by about 5 c and rainfall and vegetation patterns shifted sometimes abruptly this dramatic natural climate experiment was set in motion by cyclic variations in the geometry of earth s orbit but a complex system of feedbacks governed the transition from a glacial to an interglacial state one of the most important of these feedbacks was a well documented change in the atmospheric greenhouse gas carbon dioxide co2 1 on page 711 of this issue schmitt et al 2 provide important new carbon isotopic data that help to explain these changes

complementary constraints from carbon 13c and nitrogen 15n isotopes on the glacial ocean s soft tissue biological pump a three dimensional process based model of the ocean s carbon and nitrogen cycles including 13c and 15n isotopes is used to explore effects of idealized changes in the soft tissue biological pump results are presented from one preindustrial control run pictrl and six simulations of the last glacial maximum lgm with increasing values of the spatially constant maximum phytoplankton growth rate max which accelerates biological nutrient utilization mimicking iron fertilization the default lgm simulation without increasing max and with a shallower and weaker atlantic meridional overturning circulation and increased sea ice cover leads to 280 pg more respired organic carbon corg storage in the deep ocean with respect to pictrl dissolved oxygen concentrations in the colder glacial thermocline increase which reduces water column denitrification and with delay nitrogen fixation thus increasing the ocean s fixed nitrogen inventory and decreasing 15nno3 almost everywhere this simulation already fits sediment reconstructions of carbon and nitrogen isotopes relatively well but it overestimates deep ocean 13cdic and underestimates 15nno3 at high latitudes increasing max enhances corg and lowers deep ocean 13cdic improving the agreement with sediment data in the model s antarctic and north pacific oceans modest increases in max result in higher 15nno3 due to enhanced local nutrient utilization improving the agreement with reconstructions there models with moderately increased max fit both isotope data best whereas large increases in nutrient utilization are inconsistent with nitrogen isotopes although they still fit the carbon isotopes reasonably well the best fitting models reproduce major features of the glacial 13cdic 15n and oxygen reconstructions while simulating increased corg by 510 670 pg compared with the preindustrial ocean these results are consistent with the idea that the soft tissue pump was more efficient during the lgm both circulation and biological nutrient utilization could contribute however these conclusions are preliminary given our idealized experiments which do not consider changes in benthic denitrification and spatially inhomogenous changes in aeolian iron fluxes the analysis illustrates interactions between the carbon and nitrogen cycles as well as the complementary constraints provided by their isotopes whereas carbon isotopes are sensitive to circulation changes and indicate well the three dimensional corg distribution nitrogen isotopes are more sensitive to biological nutrient utilization

southwest atlantic water mass evolution during the last deglaciation the rise in atmospheric co2 during heinrich stadial 1 hs1 14 5 17 5 kyr b p may have been driven by the release of carbon from the abyssal ocean model simulations suggest that wind driven upwelling in the southern ocean can liberate 13c depleted carbon from the abyss causing atmospheric co2 to increase and the 13c of co2 to decrease one prediction of the southern ocean hypothesis is that water mass tracers in the deep south atlantic should register a circulation response early in the deglaciation here we test this idea using a depth transect of 12 cores from the brazil margin we show that records below 2300 m remained 13c depleted until 15 kyr b p or later indicating that the abyssal south atlantic was an unlikely source of light carbon to the atmosphere during hs1 benthic 18o results are consistent with abyssal south atlantic isolation until 15 kyr b p in contrast to shallower sites the depth dependent timing of the 18o signal suggests that correcting 18o for ice volume is problematic on glacial terminations new data from 2700 to 3000 m show that the deep sw atlantic was isotopically distinct from the abyss during hs1 as a result we find that mid depth 13c minima were most likely driven by an abrupt drop in 13c of northern component water low 13c at the brazil margin also coincided with an 80 decrease in 14c our results are consistent with a weakening of the atlantic meridional overturning circulation and point toward a northern hemisphere trigger for the initial rise in atmospheric co2 during hs1

permafrost carbon as a missing link to explain co 2 changes during the last deglaciation the atmospheric concentration of co2 increased from 190 to 280 ppm between the last glacial maximum 21 000 years ago and the pre industrial era1 2 this co2 rise and its timing have been linked to changes in the earth s orbit ice sheet configuration and volume and ocean carbon storage2 3 the ice core record of 13co2 refs 2 4 in the atmosphere can help to constrain the source of carbon but previous modelling studies have failed to capture the evolution of 13co2 over this period5 here we show that simulations of the last deglaciation that include a permafrost carbon component can reproduce the ice core records between 21 000 and 10 000 years ago we suggest that thawing permafrost due to increasing summer insolation in the northern hemisphere is the main source of co2 rise between 17 500 and 15 000 years ago a period sometimes referred to as the mystery interval6 together with a fresh water release into the north atlantic much of the co2 variability associated with the bolling allerod younger dryas period 15 000 to 12 000 years ago can also be explained in simulations of future warming we find that the permafrost carbon feedback increases global mean temperature by 10 40 relative to simulations without this feedback with the magnitude of the increase dependent on the evolution of anthropogenic carbon emissions

triple water isotopologue record from wais divide antarctica controls on glacial interglacial changes in 17oexcess of precipitation measurements of the 17oexcess of h2o were obtained from ice cores in west and east antarctica combined with previously published results from east antarctica the new data provide the most complete spatial and temporal view of antarctic 17oexcess to date there is a steep spatial gradient of 17oexcess in present day precipitation across antarctica with higher values in marine influenced regions and lower values in the east antarctic interior there is also a spatial pattern to the change in 17oexcess between the last glacial maximum lgm and holocene periods at coastal locations there is no significant change in 17oexcess at both the west antarctic ice sheet divide site and at vostok east antarctica the lgm to early holocene change in 17oexcess is about 20 per meg atmospheric general circulation model gcm experiments show that both the observed spatial gradient of 17oexcess in modern precipitation and the spatial pattern of lgm to early holocene change can be explained by kinetic isotope effects during snow formation under supersaturated conditions requiring a high sensitivity of supersaturation to temperature the results suggest that fractionation during snow formation is the primary control on 17oexcess in antarctic precipitation variations in moisture source relative humidity play a negligible role in determining the glacial interglacial 17oexcess changes observed in antarctic ice cores additional gcm experiments show that sea ice expansion increases the area over which supersaturating conditions occur amplifying the effect of colder temperatures temperature and sea ice changes alone are sufficient to explain the observed 17oexcess glacial interglacial changes across antarctica

constraint of the co2 rise by new atmospheric carbon isotopic measurements during the last deglaciation 1 the causes of the 80 ppmv increase of atmospheric carbon dioxide co2 during the last glacial interglacial climatic transition remain debated we analyzed the parallel evolution of co2 and its stable carbon isotopic ratio 13co2 in the european project for ice coring in antarctica epica dome c ice core to bring additional constraints agreeing well but largely improving the taylor dome ice core record of lower resolution our 13co2 record is characterized by a w shape with two negative 13co2 excursions of 0 5 during heinrich 1 and younger dryas events bracketing a positive 13co2 peak during the bolling allerod warm period the comparison with marine records and the outputs of two c cycle box models suggest that changes in southern ocean ventilation drove most of the co2 increase with additional contributions from marine productivity changes on the initial co2 rise and 13co2 decline and from rapid vegetation buildup during the co2 plateau of the bolling allerod

comment on synchronous records of pco2 and δ14c suggest rapid ocean derived pco2 fluctuations at the onset of younger dryas by steinthorsdottir et al steinthorsdottir et al 2014 used a previously published stomata based co2 record steinthorsdottir et al 2013 to argue for a large abrupt change in atmospheric carbon dioxide at the onset of the younger dryas yd cold interval their record implies a 50 ppm co2 rise followed by a decline by 100 ppm they compare their results to a hypothetical and highly unlikely simulation sce nario in which vertical mixing in the ocean is increased by a factor of 100 and wind strength by a factor of 7 they furthermore compare their stomata based co2 record with the ice core co2 re cord derived from epica dome c edc we here question their interpretation

stomatal proxy record of co2 concentrations from the last termination suggests an important role for co2 at climate change transitions a new stomatal proxy based record of co2 concentrations co2 based on betula nana dwarf birch leaves from the hasseldala port sedimentary sequence in south eastern sweden is presented the record is of high chronological resolution and spans most of greenland interstadial 1 gi 1a to 1c allerod pollen zone greenland stadial 1 gs 1 younger dryas pollen zone and the very beginning of the holocene preboreal pollen zone the record clearly demonstrates that i co2 were significantly higher than usually reported for the last termination and ii the overall pattern of co2 evolution through the studied time period is fairly dynamic with significant abrupt fluctuations in co2 when the climate moved from interstadial to stadial state and vice versa a new loss on ignition chemical record used here as a proxy for temperature lends independent support to the hasseldala port co2 record the large amplitude fluctuations around the climate change transitions may indicate unstable climates and that tippingpoint situations were involved in last termination climate evolution the scenario presented here is in contrast to co2 records reconstructed from air bubbles trapped in ice which indicate lower concentrations and a gradual linear increase of co2 through time the prevalent explanation for the main climate forcer during the last termination being ocean circulation patterns needs to re examined and a larger role for atmospheric co2 considered

late pleistocene evolution of the ocean s carbonate system abstract we demonstrate that the carbonate record from a single site ocean drilling program site 1089 in the deep south atlantic represents a qualitative high resolution record of the temporal evolution of the carbonate saturation state of the deep sea the record is especially notable because it is free from many of the complications that limit other records low sedimentation rates blurring by chemical erosion bioturbation etc the pattern of carbonate variability is characteristic of indo pacific cores with high carbonate glacials and low carbonate interglacials wt carbonate lags changes in benthic 18 o by an average of 7 6 kyr and carbonate variations are in phase with the rate of change first derivative of benthic 18 o intense dissolution occurs at the transition from interglacial to glacial periods and increased preservation occurs during deglaciations these observations represent two fundamentally different responses of the marine carbonate system the lagged response of carbonate to 18 o reflects a steady state mass balance process whereby the lysocline adjusts to maintain alkalinity balance between riverine input and marine burial the site 1089 carbonate signal is remarkably similar to inferred changes in the sr ca of seawater for the past 250 kyr which implies that both carbonate dissolution and seawater sr ca may be controlled by sea level induced changes in the location of carbonate deposition shelf basin fractionation during glacial to interglacial cycles the transient change in preservation during the transitions into and out of glacial stages reflects a response of the carbonate system to a redistribution of alkalinity and dic in the ocean i e carbonate compensation comparison of the site 1089 carbonate and vostok p co 2 records suggests a role of deep sea co 3 2 variations for governing at least some second order features of the atmospheric p co 2 signal in order to quantify this role however measurement of indices of dissolution along a true depth transect will be required to estimate the magnitudes of changes in deep sea co 3 2

quantitative interpretation of atmospheric carbon records over the last glacial termination 1 the glacial interglacial rise in atmospheric pco2 is one of the best known changes in paleoclimate research yet the cause for it is still unknown forcing the coupled ocean atmosphere biosphere box model of the global carbon cycle bicycle with proxy data over the last glacial termination we are able to quantitatively reproduce transient variations in pco2 and its isotopic signatures 13c 14c observed in natural climate archives the sensitivity of the box model of the isotopic carbon cycle bicycle to high or low latitudinal changes is comparable to other multibox models or more complex ocean carbon cycle models respectively the processes considered here ranked by their contribution to the glacial interglacial rise in pco2 in decreasing order are the rise in southern ocean vertical mixing rates 30 ppmv decreases in alkalinity and carbon inventories 30 ppmv the reduction of the biological pump 20 ppmv the rise in ocean temperatures 15 20 ppmv the resumption of ocean circulation 15 20 ppmv and coral reef growth 5 ppmv the regrowth of the terrestrial biosphere sea level rise and the increase in gas exchange through reduced sea ice cover operate in the opposite direction decreasing pco2 during termination i by 30 ppmv according to our model the sequence of events during termination i might have been the following a reduction of aeolian iron fertilization in the southern ocean together with a breakdown in southern ocean stratification the latter caused by rapid sea ice retreat trigger the onset of the pco2 increase after these events the reduced north atlantic deep water nadw formation during the heinrich 1 event and the subsequent resumption of ocean circulation at the beginning of the bolling allerod warm interval are the main processes determining the atmospheric carbon records in the subsequent time period of termination i we further deduce that a complete shutdown of the nadw formation during the younger dryas was very unlikely changes in ocean temperature and the terrestrial carbon storage are the dominant processes explaining atmospheric 13c after the bolling allerod warm interval

interaction between climate volcanism and isostatic rebound in southeast alaska during the last deglaciation abstract observations of enhanced volcanic frequency during the last deglaciation have led to the hypothesis that ice unloading in glaciated volcanic terrains can promote volcanism through decompression melting in the shallow mantle or a reduction in crustal magma storage time however a direct link between regional climate change isostatic adjustment and the initiation of volcanism remains to be demonstrated due to the difficulty of obtaining high resolution well dated records that capture short term climate and volcanic variability traced to a particular source region here we present an exceptionally resolved record of 19 tephra layers paired with foraminiferal oxygen isotopes and alkenone paleotemperatures from marine sediment cores along the southeast alaska margin spanning the last deglacial transition major element compositions of the tephras indicate a predominant source from the nearby mt edgecumbe volcanic field mevf we constrain the timing of this regional eruptive sequence to 14 6 13 1 ka the sudden increase in volcanic activity from the mevf coincides with the onset of bolling allerod interstadial warmth the disappearance of ice rafted detritus and rapid vertical land motion associated with modeled regional isostatic rebound in response to glacier retreat these data support the hypothesis that regional deglaciation can rapidly trigger volcanic activity rapid sea surface temperature fluctuations and an increase in local salinity i e 18osw variability are associated with the interval of intense volcanic activity consistent with a two way interaction between climate and volcanism in which rapid volcanic response to ice unloading may in turn enhance short term melting of the glaciers plausibly via albedo effects on glacier ablation zones

changes in monsoon driven upwelling in the south china sea over glacial terminations i and ii a multi proxy record upwelling intensity in the south china sea has changed over glacial interglacial cycles in response to orbital scale changes in the east asian monsoon here we evaluate new multi proxy records of two sediment cores from the north eastern south china sea to uncover millennial scale changes in winter monsoon driven upwelling over glacial terminations i and ii on the basis of u th based speleothem chronology we compare these changes with sediment records of summer monsoon driven upwelling east of south vietnam ocean upwelling is traced by reduced uk 37 based temperature and increased nutrient and productivity estimates of sea surface waters 13c on planktic foraminifera accumulation rates of alkenones chlorins and total organic carbon accordingly strong winter upwelling occurred north west of luzon philippines during late marine isotope stage 6 2 heinrich hs and greenland stadials gs hs 11 gs 26 gs 25 hs 1 and the younger dryas during these stadials summer upwelling decreased off south vietnam and sea surface salinity reached a maximum suggesting a drop in monsoon rains concurrent with speleothem records of aridity in china in harmony with a stadial to interstadial see saw pattern winter upwelling off luzon in turn was weak during interstadials in particular those of glacial terminations i and ii when summer upwelling culminated east of south vietnam most likely this upwelling terminated widespread deep water stratification coeval with the deglacial rise in atmospheric co2 yet a synchronous maximum in precipitation fostered estuarine overturning circulation in the south china sea in particular as long as the borneo strait was closed when sea level dropped below 40 m

the attenuation of fast atmospheric ch4 variations recorded in polar ice cores 1 to reconstruct fast atmospheric trace gas variations from polar ice cores it has to be considered that their amplitudes are attenuated during the enclosure process in the ice relevant processes for the attenuation are the molecular diffusion in the open pores of the firn column and the gradual bubble close off in the depth of the transition from firn to ice these processes depend mainly on temperature and accumulation rate and lead e g to a strong attenuation for cold sites with low accumulation rates with a diffusion and enclosure model it is possible to calculate the attenuation for a single event and to compare ice core records from different sites we investigate the atmospheric methane ch4 variation during the cold event 8200 years ago and calculate that its amplitude as recorded in the epica dome c ice core is attenuated to a magnitude between 34 and 59

interglacials of the last 800 000 years interglacials including the present holocene period are warm low land ice extent high sea level end members of glacial cycles based on a sea level definition we identify eleven interglacials in the last 800 000 years a result that is robust to alternative definitions data compilations suggest that despite spatial heterogeneity marine isotope stages mis 5e last interglacial and 11c 400 ka ago were globally strong warm while mis 13a 500 ka ago was cool at many locations a step change in strength of interglacials at 450 ka is apparent only in atmospheric co2 and in antarctic and deep ocean temperature the onset of an interglacial glacial termination seems to require a reducing precession parameter increasing northern hemisphere summer insolation but this condition alone is insufficient terminations involve rapid nonlinear reactions of ice volume co2 and temperature to external astronomical forcing the precise timing of events may be modulated by millennial scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere a variety of temporal trends is observed such that maxima in the main records are observed either early or late in different interglacials the end of an interglacial glacial inception is a slower process involving a global sequence of changes interglacials have been typically 10 30 ka long the combination of minimal reduction in northern summer insolation over the next few orbital cycles owing to low eccentricity and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future

two phase structure of tropical hydroclimate during heinrich stadial 1 and its global implications abstract previous studies have proposed that the two phase structure of heinrich stadial 1 hs1 is a ubiquitous feature however few studies have focused on the internal structure of hs1 over a tropical domain thus the interhemispheric ocean atmosphere teleconnections during hs1 are poorly defined here we present high resolution sedimentological geochemical and palaeoceanographic records from the core cg2 in the southern south china sea scs off the northern sunda shelf the core continuously spans 9 0 22 0 ky bp the records suggest two episodes of increased monsoon rainfall during the pre hs1 19 0 18 0 ky bp and in the early hs1 17 5 16 1 ky bp along with a weaker monsoon rainfall during the late hs1 16 1 14 7 ky bp in contrast a lower precipitation over the flores sea occurred during the early hs1 off the southern sunda shelf followed by an enhanced precipitation runoff during the late hs1 muller et al 2012 notably these two different precipitation phases characterise a southward intertropical convergence zone itcz shift over the sunda shelf during hs1 these changes are also consistent with other monsoon records as well as other available data from the tropical to high latitudes of both hemispheres supporting the global scope of the twofold hs1 we propose that the two episodes of intense monsoon rainfall over the northern sunda shelf during the pre hs1 and the early hs1 observed in our study are closely linked to two different melting events associated with european ice sheet eis retreat we further propose that the subsequent maximum atlantic meridional overturning circulation amoc reduction and the migration of the itcz to its southernmost position during the late hs1 are tightly connected with the destabilization of the marine terminating ice streams of the laurentide ice sheet lis in the north atlantic tropical positive feedbacks during hs1 in turn should have played an important role in sustaining the amoc reduction and northern hemisphere nh stadial conditions by continuously lowering the salinity of the low latitude currents in the atlantic ocean in addition the tropical itcz appears to have been a key bridge in promoting interhemispheric climate connections by which north atlantic cooling was rapidly linked to increased southern ocean surface westerlies this in turn drove upwelling and co2 ventilation from the southern ocean and thereby facilitated deglacial warming finally these findings show that tropical climate variation is an important component of deglacial climate changes understanding how it responds to millennial events like hs1 may help us better understand global teleconnections

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

stable isotope composition of cave guano from eastern borneo reveals tropical environments over the past 15 000 cal yr bp abstract insular southeast asia is a key driver for global atmospheric and oceanic circulation is a hotspot for biodiversity and conservation and is likely to have played a unique and important role in early human dispersals despite this partially due to its vast size and remote tropical location very few continuous palaeoenvironmental records exist especially in eastern borneo therefore we investigated 13 c and 15 n values and geochemistry of two cave guano deposits to reconstruct palaeoenvironments in eastern borneo firstly a profile was recovered from gomantong caves sabah reflecting a continuous deposit over 15 cal kyr bp secondly a profile was recovered from bau bau cave east kalimantan that ranged from 15 5 cal kyr bp the geochemical signature of each deposit confirmed the material to be ancient guano 13 c values revealed that a continuous dense rainforest persisted over at least the last 15 cal kyr bp around the gomantong site that was relatively insensitive to regional climate change by contrast 13 c values at bau bau indicate that although rainforest remained dominant in the record a significant drying occurred between 7 7 and 6 3 cal kyr bp with up to 25 grasses present although most regional models suggest that sea level rise and increased holocene insolation led to an increase in monsoonal moisture we find some evidence of more regional variability and that a reduction in monsoonal precipitation could have occurred however we cannot discount the implementation of an anthropogenic fire regime that opened the canopy allowing more grasses to occur

hydro isostasy and the sea level isobase of 5500 b p in north queensland australia abstract previous studies of holocene sea level in north queensland have been based on a variety of sea level related deposits with interpretations of mid holocene levels ranging from near zero up to 4 m above present we report data from 8 carefully controlled new sites located from the palm group northwards and extending into the gulf of carpentaria field evidence is from coral reef flats and prograded coastal deposits the highest sea level on inner shelf islands and mainland coast occurred 5500 yrs ago the results of this and of certain previous studies are reduced to a common reference surface or isobase which varies systematically in elevation across the region the isobase correlates strongly with predicted hydro isostatic deformation caused by postglacial sea level rise

atmospheric δ13co2 and its relation to pco2 and deep ocean δ13c during the late pleistocene the ratio of the stable carbon isotopes of atmospheric co2 13co2 contains valuable information on the processes which are operating on the global carbon cycle however current 13co2 ice core records are still limited in both resolution and temporal coverage as well as precision in this study we performed simulations with the carbon cycle box model bicycle with special emphasis on atmospheric 13co2 proposing how changes in 13co2 might have evolved over the last 740 000 years we furthermore analyze the relationship between atmospheric 13co2 pco2 and deep ocean 13c of dissolved inorganic carbon dic 13cdic in both our modeling framework and proxy records when available our analyses show that mean ocean and deep pacific 13cdic are mainly controlled by the glacial interglacial uptake and release of carbon temporarily stored in the terrestrial biosphere during warmer climate periods in contrast glacial interglacial changes in pco2 and 13co2 represent mainly a mixture of ocean related processes superimposed on the slow glacial interglacial change in terrestrial carbon storage the different processes influencing atmospheric 13co2 largely compensate each other and cancel all variability with frequencies of 1 100 kyr 1 large excursions in 13co2 can a priori be expected as any small phase difference between the relative timing of the dominant and opposite sign processes might create large changes in 13co2 amplitudes in 13co2 caused by fast terrestrial uptake or release during millennial scale climate variability depend not only on the amount of transferred carbon but also on the speed of these changes those which occur on timescales shorter than a millennium are not detectable in 13co2 because of gas exchange equilibration with the surface ocean the 13co2 signal of fast processes on the other hand is largely attenuated in ice core records during the firnification and gas enclosure we therefore suggest to measure 13co2 with priority on ice cores with high temporal resolution and select times with rather fast climatic changes

loss of carbon from the deep sea since the last glacial maximum deep ocean carbonate ion concentrations co32 and carbon isotopic ratios 13c place important constraints on past redistributions of carbon in the ocean land atmosphere system and hence provide clues to the causes of atmospheric co2 concentration changes however existing deep sea co32 reconstructions conflict with one another complicating paleoceanographic interpretations here we present deep sea co32 for five cores from the three major oceans quantified using benthic foraminiferal boron calcium ratios since the last glacial period combined benthic 13c and co32 results indicate that deep sea released co2 during the early deglacial period 17 5 to 14 5 thousand years ago was preferentially stored in the atmosphere whereas during the late deglacial period 14 to 10 thousand years ago besides contributing to the contemporary atmospheric co2 rise a substantial portion of co2 released from oceans was absorbed by the terrestrial biosphere

carbon isotope constraints on the deglacial co2 rise from ice cores the stable carbon isotope ratio of atmospheric co2 13catm is a key parameter in deciphering past carbon cycle changes here we present 13catm data for the past 24 000 years derived from three independent records from two antarctic ice cores we conclude that a pronounced 0 3 per mil decrease in 13catm during the early deglaciation can be best explained by upwelling of old carbon enriched waters in the southern ocean later in the deglaciation regrowth of the terrestrial biosphere changes in sea surface temperature and ocean circulation governed the 13catm evolution during the last glacial maximum 13catm and atmospheric co2 concentration were essentially constant which suggests that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then

late quaternary carbon cycling responses to environmental change revealed by multi proxy analyses of a sediment core from an upland lake in southwest china stable carbon isotope 13c values of organic matter in lacustrine sediments are commonly used to trace past changes in terrestrial and aquatic carbon cycles here we use a high resolution well dated 13c record from lake tengchongqinghai tcqh in southwestern china together with other proxy indices to reconstruct the paleolimnological history over the past 18 5 ka organic matter in the sediments of lake tcqh is derived predominately from aquatic macrophytes the lacustrine primary productivity is closely linked with lake level changes affected by variations in the strength of the asian summer monsoon and modified by evapotranspiration similar to lake sediments world wide a ca 3 shift occurred in the 13c values of lake tcqh in response to the significant increase in atmospheric co2 concentration during the last deglaciation in the holocene the availability of dissolved co2 in the lake water of lake tcqh was determined by variations in hydraulic energy low water turbulence creates a thick stagnant boundary layer around aquatic plants which will restrict the rate of co2 diffusion and result in more positive 13c values of aquatic plants in contrast significant water turbulence dramatically reduces the boundary layer thickness leading to more negative 13c values of aquatic plants

what do benthic δ13c and δ18o data tell us about atlantic circulation during heinrich stadial 1 approximately synchronous with the onset of heinrich stadial 1 hs1 13c decreased throughout most of the upper 1000 2500 m atlantic and at some deeper north atlantic sites this early deglacial 13c decrease has been alternatively attributed to a reduced fraction of high 13c north atlantic deep water nadw or to a decrease in the nadw 13c source value here we present new benthic 18o and 13c records from three relatively shallow 1450 1650 m subpolar northeast atlantic cores with published data from other cores these data form a depth transect 1200 3900 m in the subpolar northeast atlantic we compare last glacial maximum lgm and hs1 data from this transect with data from a depth transect of cores from the brazil margin the largest lgm to hs1 decreases in both benthic 13c and 18o occurred in upper waters containing the highest nadw fraction during the lgm we show that the 13c decrease can be explained entirely by a lower nadw 13c source value entirely by a decrease in the proportion of nadw relative to southern ocean water or by a combination of these mechanisms however building on insights from model simulations we hypothesize that reduced ventilation due to a weakened but still active atlantic meridional overturning circulation also contributed to the low 13c values in the upper north atlantic we suggest that the benthic 18o gradients above 2300 m at both core transects indicate the depth to which heat and north atlantic deglacial freshwater had mixed into the subsurface ocean by early hs1

a high resolution temporal record of environmental changes in the eastern caribbean guadeloupe from 40 to 10 ka bp abstract in neotropical regions fossil bat guano accumulated over time as laminated layers in caves hence providing a high resolution temporal record of terrestrial environmental changes additionally cave settings have the property to preserve such organic sediments from processes triggered by winds deflation abrasion and sandblasting and intense rainfall leaching away this study reports both stable carbon and nitrogen isotope compositions of frugivorous bat guano deposited in a well preserved stratigraphic succession of blanchard cave on marie galante guadeloupe these isotopic data are discussed with regard to climate changes and its specific impact on eastern caribbean vegetation during the late pleistocene from 40 to 10 ka cal bp guano 13 c values are higher than modern ones suggesting noticeable vegetation changes this provides also evidence for overall drier environmental conditions during the pleistocene compared to today meanwhile within this generally drier climate shifts between wetter and drier conditions can be observed large temporal amplitudes in both 13 c and 15 n variations reaching up to 5 9 and 16 8 respectively also indicate these oceanic tropical environments have been highly sensitive to regional or global climatic forcing stable isotope compositions of bat guano deposited from 40 to 35 ka bp the last glacial maximum and the younger dryas reveal relatively wet environmental conditions whereas at least from the end of the heinrich event 1 and the bolling period the region experienced drier environmental conditions nevertheless when considering uncertainties in the model age the isotopic record of blanchard cave show relatively similar variations with known proxy records from the northern south america and central america suggesting thus that the blanchard cave record is a robust proxy of past itcz migration teleconnections through global atmospheric pattern suggest that islands of the eastern caribbean basin could be also under the influence of a bipolar temperature gradients that impact the mean location of the itcz with a southern hemisphere imprint during the glacial period and a more significant role of northern hemisphere during the last deglaciation

flushing of the deep pacific ocean and the deglacial rise of atmospheric co 2 concentrations during the last deglaciation 19 000 9 000 years ago atmospheric co2 increased by about 80 ppm understanding the mechanisms responsible for this change is a central theme of palaeoclimatology relevant for predicting future co2 transfers in a warming world deglacial co2 rise hypothetically tapped an accumulated deep pacific carbon reservoir but the processes remain elusive as they are underconstrained by existing tracers here we report high resolution authigenic neodymium isotope data in north pacific sediment cores and infer abyssal pacific overturning weaker than today during the last glacial maximum but intermittently stronger during steps of deglacial co2 rise radiocarbon evidence suggestive of relatively old deglacial deep pacific water is reinterpreted here as an increase in preformed 14c age of subsurface waters sourced near antarctica consistent with movement of aged carbon out of the deep ocean and release of co2 to the atmosphere during the abyssal flushing events the timing of neodymium isotope changes suggests that deglacial acceleration of pacific abyssal circulation tracked southern hemisphere warming sea ice retreat and increase of mean ocean temperature the inferred magnitude of circulation changes is consistent with deep pacific flushing as a significant and perhaps dominant control of the deglacial rise of atmospheric co2

reconstruction of prehistoric pottery use from fatty acid carbon isotope signatures using bayesian inference abstract carbon isotope measurements of individual fatty acids c16 0 and c18 0 recovered from archaeological pottery vessels are widely used in archaeology to investigate past culinary and economic practices typically such isotope measurements are matched with reference to food sources for straightforward source identification or simple linear models are used to investigate mixing of contents however in cases where multiple food sources were processed in the same vessel these approaches result in equivocal solutions to address this issue we tested the use of a bayesian mixing model to determine the proportional contribution of different food sources to a series of different mixed food compositions using data generated both by simulation and by experiment the model was then applied to previously published fatty acid isotope datasets from pottery from two prehistoric sites durrington walls near stonehenge in southern britain and neustadt in northern germany we show that the bayesian approach to the reconstruction of pottery use offers a reliable probabilistic interpretation of source contributions although the analysis also highlights the relatively low precision achievable in quantifying pottery contents from datasets of this nature we suggest that with some refinement the approach outlined should become standard practice in organic residue analysis and also has potential application to a wide range of geological and geochemical investigations

mean global ocean temperatures during the last glacial transition little is known about the ocean temperature s long term response to climate perturbations owing to limited observations and a lack of robust reconstructions although most of the anthropogenic heat added to the climate system has been taken up by the ocean up until now its role in a century and beyond is uncertain here using noble gases trapped in ice cores we show that the mean global ocean temperature increased by 2 57 0 24 degrees celsius over the last glacial transition 20 000 to 10 000 years ago our reconstruction provides unprecedented precision and temporal resolution for the integrated global ocean in contrast to the depth region organism and season specific estimates provided by other methods we find that the mean global ocean temperature is closely correlated with antarctic temperature and has no lead or lag with atmospheric co2 thereby confirming the important role of southern hemisphere climate in global climate trends we also reveal an enigmatic 700 year warming during the early younger dryas period about 12 000 years ago that surpasses estimates of modern ocean heat uptake

search for a glacial age 14c depleted ocean reservoir 1 measurements of the radiocarbon age difference between mixed benthic foraminifera and several coexisting planktic entities were made in hopes of finding evidence for the existence of an isolated glacial age abyssal ocean reservoir whose demise would explain the large drops in the 14 c to c ratio in atmosphere and surface ocean carbon which occurred during the period of deglaciation forty six new radiocarbon results were obtained at seven depths covering the full range of glacial time i e 27 to 15 14 c kyrs from an equatorial pacific sediment core at 4 4 km water depth even though age reversals for foraminifera but not for coccoliths at two of the eight depths and large age differences between g sacculifer and three submixed layer planktic species mar this data set there remains little likelihood that such a reservoir existed

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

assessment of diffusive isotopic fractionation in polar firn and application to ice core trace gas records abstract during rapid variations of the atmospheric mixing ratio of a trace gas diffusive transport in the porous firn layer atop ice sheets and glaciers alters the isotopic composition of that gas relative to the overlying atmosphere records of past atmospheric trace gas isotopic composition from ice cores and firn need to be corrected for this diffusive fractionation artifact we present a novel semi empirical method to accurately estimate the magnitude of the diffusive fractionation in the ice core record our method 1 consists of a relatively simple analytical calculation 2 requires only commonly available ice core data 3 is not subject to the uncertainties inherent to estimating the accumulation rate temperature close off depth and depth diffusivity relationship back in time 4 does not require knowledge of the true atmospheric variations but uses the smoothed records obtained from ice cores 5 arguably gives more accurate results than a combined firn densification firn air transport modeling study would we apply the method to records of ch4 co2 and n2o mixing ratios and we find that the correction is particularly important for 13 c ch 4 we apply the correction to 13 c ch 4 records over the last glacial termination and the 8 2 ka event in both cases the diffusive signal exceeds the analytical precision of the data and has a significant impact on the observed isotopic trends for the 8 2 ka event the corrected data show an isotopic enrichment in 13 c ch 4 for the duration of the event consistent with reduced wetland emissions

clumped and stable isotopes of land snail shells on the chinese loess plateau and their climatic implications abstract we report stable 13cshell 18oshell and clumped isotope 47 compositions of modern and last glacial fossil snail shell carbonates from the luochuan and weinan sections on the central and southern chinese loess plateau clp our study reveals that the average 47 temperature t47 of modern snails is consistent with monitored temperatures during the snail growing season at the studied locations and is 10 c higher than that of fossil snails from glacial time moreover the average 13cshell of modern snails is more depleted than that of fossils we argue that the 13cshell cannot record changes in plant communities i e the c3 c4 ratio on the clp and may mainly indicate arid conditions with depleted values reflecting reduced aridity additionally the reconstructed snail body water 18o 18owater of modern snails is more enriched than 18o in modern growing season precipitation and 18owater of fossils this contrast may be related to the high degree of evaporative enrichment of environmental water 18o in the body ingested by modern snails under warm conditions therefore we suggest that using 18oshell to directly reconstruct the oxygen isotopes of precipitation is difficult and that higher 18oshell and 18owater values probably indicate higher environmental temperature stronger evaporative enrichment on glacial interglacial timescales on the clp

thermohaline circulation crisis and impacts during the mid pleistocene transition the mid pleistocene transition mpt marked a fundamental change in glacial interglacial periodicity when it increased from 41 thousand year to 100 thousand year cycles and developed higher amplitude climate variability without substantial changes in the milankovitch forcing here we document by using nd isotopes a major disruption of the ocean thermohaline circulation thc system during the mpt between marine isotope stages miss 25 and 21 at 950 to 860 thousand years ago which effectively marks the first 100 thousand year cycle including an exceptional weakening through a critical interglacial mis 23 at 900 thousand years ago its recovery into the post mpt 100 thousand year world is characterized by continued weak glacial thc the mpt ocean circulation crisis facilitated the coeval drawdown of atmospheric co2 and high latitude ice sheet growth generating the conditions that stabilized 100 thousand year cycles

large inert carbon pool in the terrestrial biosphere during the last glacial maximum during each of the late pleistocene glacial interglacial transitions atmospheric carbon dioxide concentrations rose by almost 100 ppm the sources of this carbon are unclear and efforts to identify them are hampered by uncertainties in the magnitude of carbon reservoirs and fluxes under glacial conditions here we use oxygen isotope measurements from air trapped in ice cores and ocean carbon cycle modelling to estimate terrestrial and oceanic gross primary productivity during the last glacial maximum we find that the rate of gross terrestrial primary production during the last glacial maximum was about 40 10 pg c yr 1 half that of the pre industrial holocene despite the low levels of photosynthesis we estimate that the late glacial terrestrial biosphere contained only 330 pg less carbon than pre industrial levels we infer that the area covered by carbon rich but unproductive biomes such as tundra and cold steppes was significantly larger during the last glacial maximum consistent with palaeoecological data our data also indicate the presence of an inert carbon pool of 2 300 pg c about 700 pg larger than the inert carbon locked in permafrost today we suggest that the disappearance of this carbon pool at the end of the last glacial maximum may have contributed to the deglacial rise in atmospheric carbon dioxide concentrations

synchronous records of pco2 and δ14c suggest rapid ocean derived pco2 fluctuations at the onset of younger dryas just before the onset of the younger dryas yd cold event several stomatal proxy based pco2 records have shown a sharp increase in atmospheric co2 concentration pco2 of between ca 50 and 100 ppm followed by a rapid decrease of similar or even larger magnitude here we compare one of these records a high resolution pco2 record from southern sweden with the intcal13 record of radiocarbon d 14 c the two records show broadly synchronous fluctuations at the yd onset specifically the intcal13 record documents decreasing d 14 c just before the yd onset when pco2 peaks consistent with a source of old co2 from the deep ocean we propose that this fluctuation occurred due to a major ocean flushing event the cause of the flushing event remains speculative but could be related to the hypothesis of the glacial ocean as a thermobaric capacitor we confirm that the earth system can produce such large multidecadal timescale fluctuations in pco2 through simulating an artificial ocean flushing event with the genie earth system model we suggest that sharp transitions of pco2 may have remained undetected so far in ice cores due to inter firn gas exchange and time averaging the stomatal proxy record is a powerful complement to the ice core records for the study of rapid climate change

environmental geochemistry of the river gomti a tributary of the ganges river water and sediment samples collected from the gomti river a tributary of the ganges river system during the postmonsoon season have been analyzed to estimate major elemental chemistry water chemistry of the river gomti shows almost monotonous spatial distribution of various chemical species especially because of uniform presence of alluvium dun gravels throughout the basin the river annually transports 0 34 106 tonnes of total suspended material tsm and 3 0 106 tonnes of total dissolved solids tds 69 percent of which is accounted for by bicarbonate ions only samples collected downstream of the city of lucknow show the influence of anthropogenic loadings for a considerable distance in the river water na cl and so4 2 concentrations build up downstream the bed sediment chemistry is dominated by si 36 percent reflecting a high percentage of detrital quartz which makes up about 74 percent of the mineralogy of the bed sediments in the river gomti the average kjeldahl nitrogen concentration 234 g g indicates indirectly the amount of organic matter in the sediments the hg concentration in sediments has been found to be higher average 904 ppb than the background value the suspended sediments are well sorted very finely skewed and extremely leptokurtic indicating a low energy condition of flow in the gomti river the influence of chemical loads in the gomti has been found to be small or nonexistent on the ganges river perhaps because the water discharge of the gomti 1 57 percent to the ganges is quite low

evolution of the stable carbon isotope composition of atmospheric co2 over the last glacial cycle we present new c measurements of atmospheric co covering the last glacial interglacial cycle complementing previous records covering terminations i and ii most prominent in the new record is a significant depletion in c atm of 0 5 occurring during marine isotope stage mis 4 followed by an enrichment of the same magnitude at the beginning of mis 3 such a significant excursion in the record is otherwise only observed at glacial terminations suggesting that similar processes were at play such as changing sea surface temperatures changes in marine biological export in the southern ocean so due to variations in aeolian iron fluxes changes in the atlantic meridional overturning circulation upwelling of deep water in the so and long term trends in terrestrial carbon storage based on previous modeling studies we propose constraints on some of these processes during specific time intervals the decrease in c atm at the end of mis 4 starting approximately 64 kyr b p was accompanied by increasing co this period is also marked by a decrease in aeolian iron flux to the so followed by an increase in so upwelling during heinrich event 6 indicating that it is likely that a large amount of c depleted carbon was transferred to the deep oceans previously i e at the onset of mis 4 apart from the upwelling event at the end of mis 4 and potentially smaller events during heinrich events in mis 3 upwelling of deep water in the so remained reduced until the last glacial termination whereupon a second pulse of isotopically light carbon was released into the atmosphere

late quaternary deep stratification climate coupling in the southern ocean implications for changes in abyssal carbon storage the southern ocean plays an important role in modulating pleistocene atmospheric co2 concentrations but the underlying mechanisms are not yet fully understood here we report the laser grain size distribution and mn geochemical data of a 523 kyr long sediment record core ant30 p1 02 off prydz bay east antarctica to trace past physical changes in the deep southern ocean the core sediments are predominantly composed of clay and silt sized material three grain size end members em as well as three sensitive grain size classes sc were discerned interpreted as ice rafted debris em1 and sc1 and coarse em2 and sc2 and fine em3 sc3 materials deposited from bottom nepheloid layers respectively ratios of em2 em2 em3 and sc2 sc3 reveal changes in the local bottom current strength which is related to the deep ocean diapycnal mixing rate showing higher values during interglacial periods and lower values during glacial periods mno was enriched at each glacial termination probably caused by abrupt elevations in antarctic bottom water aabw formation rate lower aabw formation rate and reduced deep diapycnal mixing during glacial periods enhanced deep southern ocean stratification contributing to glacial atmospheric co2 drawdown the elevated aabw formation and enhanced deep diapycnal mixing during glacial terminations alleviated such deep stratification promoting deeply sequestered co2 to outgas

radiocarbon age anomaly at intermediate water depth in the pacific ocean during the last deglaciation 1 benthic and planktonic 14c ages are presented for the last glacial termination from marine sediment core vm21 30 from 617 m in the eastern equatorial pacific the benthic planktonic 14c age differences in the core increased to more than 6000 years between heinrich 1 time and the end of the younger dryas period several replicated 14c ages on different benthic and planktonic species from the same samples within the deglacial section of the core indicate a minimal amount of bioturbation scanning electron microscopy reveals no evidence of calcite alteration or contamination the oxygen isotope stratigraphy of planktonic and benthic foraminifera does not indicate anomalously old glacial age values and there is no evidence of a large negative stable carbon isotope excursion in benthic foraminifera that would indicate input of old carbon from dissociated methane it appears therefore that the benthic 14c excursion in this core is not an artifact of diagenesis bioturbation or a pulse of methane a benthic 14c stratigraphy reconstructed from the 14c ages from the deglacial section of vm21 30 appears to match that of baja margin core mv99 mc19 gc31 pc08 705 m but the magnitude of the low 14c excursion is much larger in the vm21 30 record this would seem to imply that the vm21 30 core was closer to the source of 14c depleted waters during the deglaciation but the source of this co2 remains elusive

timing of past glaciation at the sierra de aconquija northwestern argentina and throughout the central andes abstract advances in cosmogenic nuclide exposure dating have made moraines valuable terrestrial recorders of palaeoclimate a growing number of moraine chronologies reported from the central andes show that tropical glaciers responded sensitively to past changes in precipitation and temperature over timescales ranging from 103 to 105 years however the causes of past glaciation in the central andes remain uncertain explanations have invoked insolation modulated variability in the strength of the south american summer monsoon teleconnections with the north atlantic ocean and or cooling in the southern hemisphere the driver for these past climate changes is difficult to identify partly due to a lack of dated moraine records especially in climatically sensitive areas of the southern central andes moreover new constraints are needed on precisely where and when glaciers advanced we use cosmogenic 10be produced in situ to determine exposure ages for three generations of moraines at the sierra de aconquija situated at 27 s on the eastern flank of the southern central andes these moraines record glacier advances at approximately 22 ka and 40 ka coincident with summer insolation maxima in the sub tropics of the southern hemisphere as well as at 12 5 ka and 13 5 ka during the younger dryas and the antarctic cold reversal respectively we also identify minor glaciation during bond event 5 also known as the 8 2 ka event these moraines register past climate changes with high fidelity and currently constitute the southernmost dated record of glaciation on the eastern flank of the central andes to contextualise these results we compile 10be data reported from 144 moraines in the eastern central andes that represent past glacier advances we re calculate exposure ages from these data using an updated reference production rate and we re interpret the moraine ages by taking the oldest clustered boulder age after the exclusion of outliers attributed to nuclide inheritance as closest to the timing of glacier advance an approach for which we provide empirical justification this compilation reveals that central andean glaciers have responded to changes in temperature and precipitation we identify cross latitude advances in phase with insolation cycles the last global glacial maximum and episodes of strengthened monsoonal moisture transport including the younger dryas and heinrich stadials 1 and 2 our results from the sierra de aconquija allow us to constrain the southerly limit of enhanced precipitation associated with heinrich stadials at 25 s more broadly our findings demonstrate at both local and regional scales that moraines record past climate variability with a fine spatial and temporal resolution

geomagnetic field intensity during the last 60 000 years based on 10be and 36cl from the summit ice cores and 14c abstract based on 10 be 36 cl and 14 c records we reconstruct past changes in the geomagnetic field intensity under the assumption that radionuclide records are mainly influenced by changes in their production rates subsequent comparison of these records with independent geomagnetic field reconstructions allows us to assess the reliability of our approach and to identify periods where our method or the geomagnetic field reconstructions might be problematic the geomagnetic field derived from the 10 be flux to summit in central greenland agrees well with independent geomagnetic field intensity reconstructions however compared to independent palaeomagnetic data the radionuclide record suggests increased geomagnetic field intensities especially for the period from 20 000 to 30 000 years bp 36 cl from the grip ice core agrees well with the 10 be record for the last ice age and hence also the reconstructed geomagnetic field based on the tree ring radiocarbon record it is possible to reconstruct geomagnetic field intensity changes during the holocene a comparison of radiocarbon based and independent geomagnetic field reconstructions indicates that changes in the carbon cycle significantly influenced the atmospheric radiocarbon concentration before 10 000 years bp

holocene carbon cycle dynamics based on co2 trapped in ice at taylor dome antarctica a high resolution ice core record of atmospheric co2 concentration over the holocene epoch shows that the global carbon cycle has not been in steady state during the past 11 000 years analysis of the co2 concentration and carbon stable isotope records using a one dimensional carbon cycle model uggests that changes in terrestrial biomass and sea surface temperature were largely responsible for the observed millennial scale changes of atmospheric co2 concentrations

co2 and o2 n2 variations in and just below the bubble clathrate transformation zone of antarctic ice cores co2 measurements on the epica european project for ice coring in antarctica dml ice core in depth levels just below the bubble ice clathrate ice transformation zone 1230 2240 m depth were performed in the youngest part 1230 1600 m they reveal variations of up to 25 ppmv around the mean atmospheric concentration within centimetres corresponding to a snow deposition interval of a few years similar results are found at corresponding depth regions of the dome c and the talos dome ice cores since we can exclude all hitherto known processes altering the concentration of co2 in ice cores we present a hypothesis about spatial fractionation of air components related to episodically increasing clathrate formation followed by diffusion processes from bubbles to clathrates this hypothesis is supported by optical line scan observations and by o2 n2 measurements at the same depth where strong co2 variations are detected below the clathrate formation zone this small scale fractionation process is slowly smoothed out most likely by diffusion regaining the initial mean atmospheric concentration although this process compromises the representativeness of a single co2 measurement on small ice samples in the clathrate formation zone of an ice core it does not affect the mean atmospheric co2 concentration if co2 values are averaged over a sufficiently long depth scale 10 cm in case of the epica dml ice core

deep south atlantic carbonate chemistry and increased interocean deep water exchange during last deglaciation abstract carbon release from the deep ocean at glacial terminations is a critical component of past climate change but the underlying mechanisms remain poorly understood we present a 28 000 year high resolution record of carbonate ion concentration a key parameter of the global carbon cycle at 5 km water depth in the south atlantic we observe similar carbonate ion concentrations between the last glacial maximum and the late holocene despite elevated concentrations in the glacial surface ocean this strongly supports the importance of respiratory carbon accumulation in a stratified deep ocean for atmospheric co 2 reduction during the last ice age after 9 mol kg decline during heinrich stadial 1 deep south atlantic carbonate ion concentration rose by 24 mol kg from the onset of bolling to pre boreal likely caused by strengthening north atlantic deep water formation bolling or increased ventilation in the southern ocean younger drays or both pre boreal the 15 mol kg decline in deep water carbonate ion since 10 ka is consistent with extraction of alkalinity from seawater by deep sea caco 3 compensation and coral reef growth on continental shelves during the holocene between 16 600 and 15 000 years ago deep south atlantic carbonate ion values converged with those at 3 4 km water depth in the western equatorial pacific as did carbon isotope and radiocarbon values these observations suggest a period of enhanced lateral exchange of carbon between the deep south atlantic and pacific oceans probably due to an increased transfer of momentum from southern westerlies to the southern ocean by spreading carbon rich deep pacific waters around antarctica for upwelling invigorated interocean deep water exchange would lead to more efficient co 2 degassing from the southern ocean and thus to an atmospheric co 2 rise during the early deglaciation

environmental influences on rabbit and hare bone isotope abundances implications for paleoenvironmental research abstract palaeoclimatological and palaeoenvironmental reconstructions based on stable isotope analysis of mammalian bone require an understanding of the behavior and physiology of the organism and mandate taxon specific considerations this study assesses the utility of using bone tissue of leporids cottontail rabbits sylvilagus sp and hares lepus sp as paleoenvironmental proxies leporids are globally widespread and commonly found in many archaeological middens in north america with material available in many museum collections we isolated and analyzed bone collagen and carbonate from 135 modern specimens from mexico and southern united states for light element stable isotope values of oxygen nitrogen and carbon stable isotope values were assessed with local ecoregion types for each specimen location and interpolated precipitation humidity and temperature variables reflecting the water acquisition strategies of leporids our results show significant negative correlations of bone 18o values with mean annual precipitation and with relative humidity contrary to expectations neither 13c nor 15n values are strong predictors of moisture variables which may be due to micro scale topographic and environmental variation and selective feeding strategies significant positive correlations are observed for 13c and 15n values with temperature variables our study increases our ability to model past environmental landscapes by considering how behavior ecology and environment interact to result in measured stable isotope values in leporid bones

the carbon isotope composition of atmospheric co 2 in paris one characteristic of air pollution in the urban environment is high co2 concentrations resulting from human activities determining the relative contributions of the different co2 sources can be addressed simply and elegantly by combining isotope and concentration measurements using this approach on atmospheric co2 samples collected in paris its suburbs and the open country provides fairly accurate conclusions our results show that air pollution within the first few metres above ground results basically from binary mixtures among which road traffic is the main contributor and in particular vehicles using unleaded gasoline 90 of the total heating sources which account for 50 of the co2 input below the atmospheric inversion level and vehicles using diesel contribute very little human respiration has a recognisable signature at street level under certain circumstances the combined isotope and concentration analysis provides a sensitive tracer of local variations even detecting the occasional prevalence of human respiration and the onset of actions in which natural gas is burnt it also detects surprising inlets of clean air co2 wise in the very centre of the city

oxygen 18 16 variability in greenland snow and ice with 10 3 to 105 year time resolution the 3 km long greenland ice sheet project 2 gisp2 ice core presents a 100 000 year detailed oxygen isotope profile covering almost a full glacial interglacial cycle measuranents of isotopic fluctuations in snow frost and atmospheric water vapor samples collected during summer field seasons up to 20 0 are compatible with the large and abrupt 80 160 changes observed in accumulated tim snow pit 15 80 profiles from the gisp2 summit area however show rapid smoothing of the 180 160 signal near the surface beyond about 2 m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate the longer climate fluctuations also have regional and often global significance in the older part of the record corresponding to marine isotope stages mis 5a to 5d the effect of orbital climate forcing via the 19 and 23 kyr precession cycles and the 41 kyr obliquity cycle is obvious from the end ofmis 5a at about 75 000 years b p till the end of the glacial at the younger dryas preboreal transition at 11 650 years b p the o180 160 record shows frequent rapid switches between intermediate interstadial and low stadial values fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1 5 kyr a broad peak at 4 0 kyr and additional shorter periods detailed comparison of the gisp2 180 160 record with the vostok antarctica 15d record pacific ocean foraminiferal 180 160 grande pile france tree pollen and insolation indicates that a counterpart to many of the rapid 180 160 fluctuations of gisp2 can be found in the other records and that the gisp2 isotopic changes clearly are the local expression of climate changes of worldwide extent correlation of events on the independent gisp2 and specmap time scales for the interval 10 000 50 000 years b p shows excellent chronometric agreement except possibly for the event labeled 3 1 the glacial to interglacial transition evidently started simultaneously in the arctic and the antarctic but its development and its expression in greenland isotopes was later suppressed by the influence of meltwater especially from the barents sea ice sheet on deep water formation and ocean circulation meltwaters from different ice sheets bordering the north atlantic also influenced ocean circulation during the bolling allerod interstadial complex and the younger dryas and led to a distinct development of european climate and greenland 180 160 values the holocene interval with long term stable mean isotopic values contains several fluauations with periods from years to millennia dominant is a 6 3 year oscillation with amplitude up to 3 to 4 0 periodicities of 11 and 210 years also found in the solar modulated records of the cosmogenic isotopes 1obe and 14c suggest solar processes as the cause of these cycles depression of180 160 values cooling by volcanic eruptions is observed in stacked gisp215 80 records but the effect is small and not likely to trigger major climate changes

a high resolution record of atmospheric 14c based on hulu cave speleothem h82 abstract the development of a calibration of atmospheric radiocarbon 14c is a significant scientific goal because it provides the means to link the numerous 14c dated paleoclimate records to a common timescale with absolutely dated records and thereby improve our understanding the relationships between the carbon cycle and climate change currently few calibration datasets that directly sample the atmospheric 14c reservoir are available beyond the end of the dendro dated holocene tree ring record at 12 6 kyr bp before 1950 ad in the absence of suitable true atmospheric records 14c calibrations beyond this age limit are based largely on marine data that are complicated by the marine reservoir effect which may have varied over the glacial cycle in this paper we present a high resolution record of u th series and 14c measurements from hulu cave speleothem h82 spanning 10 6 26 8 kyr bp corrections for detrital 230th are negligible and the contribution of 14c free geologic carbon to the speleothem calcite is small 5 6 and is stable across major climate shifts the time series provides a 16 kyr record of atmospheric 14c as well as an updated age model for the existing hulu cave 18o record the 14c data are in good overall agreement with existing marine and terrestrial 14c records but comparisons with the cariaco basin marine 14c record through the deglacial interval reveal that the cariaco reservoir age appears to have varied during parts of the younger dryas and heinrich stadial 1 cold events this highlights the importance of developing extended high resolution marine and terrestrial 14c records as a means of detecting changes in ocean circulation over the glacial cycle

firn processes and δ15n potential for a gas phase climate proxy abstract in order to quantify the sequence of events between changes in atmospheric composition and climate changes recorded in ice cores we must accurately account for the age difference between ice and gas at a given depth this gas age ice age difference depends on the age of the ice at the bottom of the firn layer where the bubbles are closed off firn densification models are used to calculate how this age difference varied in the past but have an uncertainty on the order of 1000 years for central antarctic sites here we explore the possibility that 15 n of n 2 is a gas phase proxy of climate which can be used to synchronize gas and ice records we present the 15 n record from the epica dome c edc ice core covering the last three glacial terminations and five glacial interglacial cycles between 300 and 800 ka previous studies have shown that gravitational settling enriches 15 n as a function of the diffusive column height in the firn if densification models prediction of deeper firn close off under glacial conditions is correct then we would expect heavier 15 n during glacial periods and a negative correlation with temperature instead edc 15 n is positively correlated with the ice deuterium content a proxy for temperature as previously reported at vostok dome fuji and epica dronning maud land we propose a mechanism that links accumulation rate firn permeability and convective mixing in the top meters of the firn to explain this correlation between 15 n and ice deuterium content the tightest correlation is observed over glacial terminations supporting the idea that 15 n is a property in the gas phase that records changes in surface conditions linked to deglacial warming

increased ventilation age of the deep northeast pacific ocean during the last deglaciation the amount of radiocarbon depleted carbon dioxide in the atmosphere rose dramatically during the last deglaciation estimates of the radiocarbon content of water at 2 7 km depth in the northeast pacific ocean over the past 24 000 years suggest that this water mass was not a significant source of this carbon

an oceanic cold reversal during the last deglaciation a detailed deuterium excess profile measured along the dome c epica european project for ice coring in antarctica core reveals the timing and strength of the sea surface temperature changes at the source regions for dome c precipitation we infer that an oceanic cold reversal took place in the southern indian ocean 800 years after the antarctic cold reversal the temperature gradient between the oceanic moisture source and antarctica is similar to the dome c sodium profile during the deglaciation illustrating the strong link between this gradient and the strength of the atmospheric circulation

consistent dating for antarctic and greenland ice cores we are hereby presenting a new dating method based on inverse techniques which aims at calculating consistent gas and ice chronologies for several ice cores the proposed method yields new dating scenarios simultaneously for several cores by making a compromise between the chronological information brought by glaciological modeling i e ice flow model firn densification model accumulation rate model and by gas and ice stratigraphic constraints this method enables us to gather widespread chronological information and to use regional or global markers i e methane volcanic sulfate beryllium 10 tephra layers etc to link the core chronologies stratigraphically confidence intervals of the new dating scenarios can be calculated thanks to the probabilistic formulation of the new method which takes into account both modeling and data uncertainties we apply this method simultaneously to one greenland ngrip and three antarctic epica dome c epica dronning maud land and vostok ices cores and refine existent chronologies our results show that consistent ice and gas chronologies can be derived for depth intervals that are well constrained by relevant glaciological data in particular we propose new and consistent dating of the last deglaciation for greenland and antarctic ice and gas records

synchronous volcanic eruptions and abrupt climate change 17 7 ka plausibly linked by stratospheric ozone depletion glacial state greenhouse gas concentrations and southern hemisphere climate conditions persisted until 17 7 ka when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the southern hemisphere with many changes ascribed to a sudden poleward shift in the southern hemisphere westerlies and subsequent climate impacts we used high resolution chemical measurements in the west antarctic ice sheet divide byrd and other ice cores to document a unique 192 y series of halogen rich volcanic eruptions exactly at the start of accelerated deglaciation with tephra identifying the nearby mount takahe volcano as the source extensive fallout from these massive eruptions has been found 2 800 km from mount takahe sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface uv radiation indicate that the eruptions led to stratospheric ozone depletion rather than a highly improbable coincidence circulation and climate changes extending from the antarctic peninsula to the subtropics similar to those associated with modern stratospheric ozone depletion over antarctica plausibly link the mount takahe eruptions to the onset of accelerated southern hemisphere deglaciation 17 7 ka

the role of southern ocean processes in orbital and millennial co2 variations a synthesis abstract recent progress in the reconstruction of atmospheric co 2 records from antarctic ice cores has allowed for the documentation of natural co 2 variations on orbital time scales over the last up to 800 000 years and for the resolution of millennial co 2 variations during the last glacial cycle in unprecedented detail this has shown that atmospheric co 2 varied within natural bounds of approximately 170 300 ppmv but never reached recent co 2 concentrations caused by anthropogenic co 2 emissions in addition the natural atmospheric co 2 concentrations show an extraordinary correlation with southern ocean climate changes pointing to a significant direct or indirect influence of climatic and environmental changes in the southern ocean region on atmospheric co 2 concentrations here we compile recent ice core and marine sediment records of atmospheric co 2 temperature and environmental changes in the southern ocean region as well as carbon cycle model experiments in order to quantify the effect of potential southern ocean processes on atmospheric co 2 related to these orbital and millennial changes this shows that physical and biological changes in the so are able to explain substantial parts of the glacial interglacial co 2 change but that none of the single processes is able to explain this change by itself in particular changes in the southern ocean related to changes in the surface buoyancy flux which in return is controlled by the waxing and waning of sea ice may favorably explain the high correlation of co 2 and antarctic temperature on orbital and millennial time scales in contrast the changes of the position and strength of the westerly wind field were most likely too small to explain the observed changes in atmospheric co 2 or may even have increased atmospheric co 2 in the glacial also iron fertilization of the marine biota in the southern ocean contributes to a glacial drawdown of co 2 but turns out to be limited by other factors than the total dust input such as bioavailability of iron or macronutrient supply

paleoceanographic conditions at approximately 20 and 70 ka recorded in kikaithyris hanzawai brachiopoda shells abstract the 13c and 18o values of fossil brachiopod shells have been widely used as paleoenvironmental proxies in this study we investigated intrashell and intraspecific variations in the isotopic and minor element concentrations of well preserved shells of the brachiopod kikaithyris hanzawai yabe from the last glacial period 20 ka last glacial maximum lgm and 70 ka marine isotope stage 4 mis4 collected in the central ryukyus and used these data to estimate the paleoceanographic conditions seawater temperature concentration of dissolved inorganic carbon dic and 13c value of dic 13cdic the 13c and 18o profiles along the maximum growth axis obtained from the inner shell surface show three distinct intervals corresponding to changes in shell morphology these results suggest that the bulk isotopic compositions of brachiopods with complex shell morphologies are unsuitable for paleoenvironmental reconstructions nevertheless there exists a specific shell portion with relatively small intrashell and intraspecific variations the past seawater temperatures derived from the 18o values of this portion are consistent with the alkenone and planktic foraminiferal mg ca based past seawater temperatures reported in previous studies the past 13cdic values estimated from the 13c values of the specific shell portion are within the range of the past 13cdic values calculated from known atmospheric and oceanographic parameters the past dic concentrations reconstructed from the brachiopod based 13cdic values are lower than the present concentrations in the east china sea which can be explained by low partial pressure of co2 during the last glacial period these results indicate that the 13c and 18o values obtained from k hanzawai shells are potential paleoenvironmental indicators the intrashell and intraspecific variations in the k hanzawai shells are different for each minor element some anomalously high mn and fe concentrations in the shells are probably caused by metabolic factor s not by meteoric diagenesis this suggests that the minor element concentrations are useful but not perfect for distinguishing diagenetically altered and unaltered portions of the shells of k hanzawai in the studied succession

deglacial weakening of the oceanic soft tissue pump global constraints from sedimentary nitrogen isotopes and oxygenation proxies abstract among the many potential explanations for the 80 ppm rise of atmospheric co2 concentrations at the end of the last ice age most involve a weakening of the oceanic soft tissue pump here we use global data compilations of sedimentary nitrogen isotopes and benthic oxygenation proxies to provide a synoptic global perspective on the deglacial soft tissue pump weakening the net change between the last glacial maximum and holocene shows a removal of respired carbon everywhere that proxy data is available with the exception of the upper 1 5 km of the north pacific while excess nitrate accumulated in polar oceans these observations could be explained by intensifying iron limitation a shoaling of organic matter remineralization and or a change in ocean circulation but are inconsistent with a change in the magnitude or position of the southern mid latitude westerlies the net soft tissue pump weakening was front loaded in the early deglaciation 17 5 14 ka when atmospheric 13c and 14c were changing rapidly and appears to have contributed little net change thereafter superimposed on the overall deglacial trend were pronounced transient changes that coincided with variability in the atlantic meridional overturning circulation amoc and bipolar seesaw the seesaw variability is most clearly expressed as anti phased oxygenation changes between the upper 1 5 km of the north pacific and the deep north atlantic consistent with an atlantic pacific ventilation seesaw but it dominated transient variability in records throughout the world although the soft tissue pump seesaw made little contribution to the contrast between the glacial and interglacial states it could have contributed to deglacial variability in atmospheric co2 and might have catalyzed the deglaciation

a 190 drop in atmosphere s δ14c during the mystery interval 17 5 to 14 5 kyr reconstructions of atmospheric 14c for the deglacial period reveal a 190 10 drop between 17 5 and 14 5 kyr before present during the mystery interval while it appears that the major contributor must be the mixing between an isolated low radiocarbon abyssal reservoir and the remainder of the ocean a combination of 14c measurements on coexisting benthic and planktic foraminifera shells and 13c 12c measurements on benthic foraminifera make it difficult to identify a sufficiently large volume for this reservoir an alternative scenario based on higher 14c production rates between about 38 and 18 kyr ago would escape the need for a large isolated reservoir prior to the mystery interval but instead would call for a better ventilated ocean afterwards the addition of 14c deficient sedimentary carbon appears not to be an important contributor while the unlikely explanation that the half life of 14c is 15 greater than the accepted value 5730 yr would eliminate the steady decrease in the 14c c over the last 40 kyr it would not explain the steep drop which occurred between 17 5 and 14 5 kyr

hydrological impact of heinrich events in the subtropical northeast atlantic reconstructing the impact of heinrich events outside the main belt of ice rafting is crucial to understanding the underlying causes of these abrupt climatic events a high resolution study of a marine sediment core from the iberian margin demonstrates that this midlatitude area was strongly affected both by cooling and advection of low salinity arctic water masses during the last three heinrich events these paleoclimatic time series reveal the internal complexity of each of the last three heinrich events and illustrate the value of parallel studies of the organic and inorganic fractions of the sediments

deglaciation in the tropical indian ocean driven by interplay between the regional monsoon and global teleconnections abstract high resolution climate records of the ice age terminations from monsoon dominated regions reveal the interplay of regional and global driving forces speleothem records from chinese caves indicate that glacial terminations were interrupted by prominent weak monsoon intervals wmi lasting a few thousand years deglacial wmis are interpreted as the result of cold temperature anomalies generated by sea ice feedbacks in the north atlantic most prominently during heinrich events recent modeling results suggest however that wmis reflect changes in the intensity of the indian rather than the east asian monsoon here we use foraminiferal trace element mg ca and ba ca and stable isotope records from a sediment core off the malabar coast in the southeastern arabian sea with centennial scale resolution to test this hypothesis and to constrain the nature and timing of deglacial climate change in the tropical indian ocean the malabar deglacial sst record is unique in character and different from other tropical climate records sst at the last glacial maximum was 2 7 0 5 c colder than pre industrial sst deglacial warming started at 18 6 95 ci range 18 8 18 1 kyr bp within error of the onset of warming at other tropical sites as well as in antarctica and the southern ocean and either coeval with or up to 1 kyr before the atmospheric co 2 rise warming took place in two steps separated by an interval of stable sst between 15 7 16 2 14 9 and 13 2 13 9 12 0 kyr bp the 18 o water record and the ba ca record which is a measure of indian sub continent riverine runoff indicate that the last ice age termination was marked by a prominent weak indian monsoon interval interrupted by an intense monsoon phase as seen in speleothem records and predicted by modeling a strong correspondence between the timing of the malabar 18 o sw record and the hulu cave monsoon record suggests that deglacial 18 o changes in both localities dominantly reflect compositional changes in precipitation likely driven by changes in the north atlantic

the southern ocean s role in carbon exchange during the last deglaciation changes in the upwelling and degassing of carbon from the southern ocean form one of the leading hypotheses for the cause of glacial interglacial changes in atmospheric carbon dioxide we present a 25 000 year long southern ocean radiocarbon record reconstructed from deep sea corals which shows radiocarbon depleted waters during the glacial period and through the early deglaciation this depletion and associated deep stratification disappeared by 14 6 ka thousand years ago consistent with the transfer of carbon from the deep ocean to the surface ocean and atmosphere via a southern ocean ventilation event given this evidence for carbon exchange in the southern ocean we show that existing deep ocean radiocarbon records from the glacial period are sufficiently depleted to explain the 190 per mil drop in atmospheric radiocarbon between 17 and 14 5 ka

glacial water mass structure and rapid δ18o and δ13c changes during the last glacial termination in the southwest pacific abstract changes in ocean circulation are thought to have contributed to lowering glacial atmospheric co 2 levels by enhancing deep ocean sequestration of carbon that was returned to the atmosphere during glacial terminations high resolution benthic foraminiferal 13 c and 18 o records from a depth transect of cores in the southwest pacific ocean presented here provide evidence that both wind and thermohaline driven circulation drove co 2 from the ocean during the last deglaciation shallow geochemical stratification in the glacial southern ocean was followed by a short pulse of rapid 13 c enrichment to intermediate water depths during heinrich stadial 1 indicative of better ventilated intermediate waters co occurring with documented wind driven upwelling in the southern ocean intermediate depth 13 c enrichment paused at the start of the antarctic cold reversal 14 7 ka implying a brief shallow restratification while deeper layers were progressively flushed of 13 c depleted and 18 o enriched waters likely caused by the increasing influence of deep waters sourced from the north atlantic the coincidence of atmospheric co 2 increases with these geochemical shifts in both shallow and deep cores suggests that shifts in both atmospheric and oceanic circulation contributed to the deglacial rise of co 2