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

marine derived 14c calibration and activity record for the past 50 000 years updated from the cariaco basin abstract an expanded cariaco basin 14c chronology is tied to 230th dated hulu cave speleothem records in order to provide detailed marine based 14c calibration for the past 50 000 years the revised high resolution cariaco 14c calibration record agrees well with data from 230th dated fossil corals back to 33 ka with continued agreement despite increased scatter back to 50 ka suggesting that the record provides accurate calibration back to the limits of radiocarbon dating the calibration data document highly elevated 14c during the glacial period carbon cycle box model simulations show that the majority of observed 14c change can be explained by increased 14c production however from 45 to 15 ka 14c remains anomalously high indicating that the distribution of radiocarbon between surface and deep ocean reservoirs was different than it is today additional observations of the magnitude spatial extent and timing of deep ocean 14c shifts are critical for a complete understanding of observed glacial 14c variability

flow dissolution and precipitation in dolomite 1 the evolution of hydraulic conductivity and porosity during the process of dedolomitization was examined in a series of laboratory experiments by analyzing the effects of concurrent dolomite dissolution and calcium carbonate precipitation linear flow experiments were performed in columns of crushed sucrosic dolomite by injecting different concentrations of hcl at various flow rates temporal changes in head gradient were used to calculate overall hydraulic conductivities of each column while chemical analyses of the effluent acid enabled estimation of porosity changes during the experiments after each experiment the rock samples were retrieved and sectioned in order to study the pore space geometry micromorphology and mineral concentrations a range of injected hcl concentrations and flow rates was identified which leads to oscillations in the effective hydraulic conductivity and porosity of the evolving rock samples in all cases however the porous medium ultimately clogged short term experiments were also used to study the formation of dissolution and precipitation bands along the columns under the experimental conditions dolomite dissolution is a reaction rate controlled process experiments indicated that as such the flow rate and the ph of the injected fluid affect dissolution only during the initial stages when calcium carbonate is dissolved on the other hand both the flow rate and the ph of the injected fluid strongly influence the precipitation process throughout the duration of the experiments because higher flow rates retard nucleation these findings are in qualitative accordance with field observations of dolomite formations

towards radiocarbon calibration beyond 28 ka using speleothems from the bahamas we present a new speleothem record of atmospheric 14c between 28 and 44 ka that offers considerable promise for resolving some of the uncertainty associated with existing radiocarbon calibration curves for this time period the record is based on a comprehensive suite of ams 14c ages using new low blank protocols and u th ages using high precision mc icpms procedures atmospheric 14c was calculated by correcting 14c ages with a constant dead carbon fraction dcf of 22 7 5 9 based on a comparison of stalagmite 14c ages with the intcal04 reimer et al 2004 calibration curve between 15 and 11 ka the new 14c speleothem record shows similar structure and amplitude to that derived from cariaco basin foraminifera hughen et al 2004 2006 and the match is further improved if the latter is tied to the most recent greenland ice core chronology svensson et al 2008 these data are however in conflict with a previously published 14c data set for a stalagmite record from the bahamas gb 89 24 1 beck et al 2001 which likely suffered from 14c analytical blank subtraction issues in the older part of the record the new bahamas speleothem 14c data do not show the extreme shifts between 44 and 40 ka reported in the previous study beck et al 2001 causes for the observed structure in derived atmospheric 14c variation based on the new speleothem data are investigated with a suite of simulations using an earth system model of intermediate complexity data model comparison indicates that major fluctuations in atmospheric 14c during marine isotope stage 3 is primarily a function of changes in geomagnetic field intensity although ocean atmosphere system reorganisation also played a supporting role

inter hemispheric transport of volcanic ash from a 1259 a d volcanic eruption to the greenland and antarctic ice sheets a strong volcanic sulfuric acid signal corresponding to an age of 1259 a d has been reported in ice cores from greenland antarctica and arctic canada tiny 5 m volcanic glass shards were reported previously in samples from this layer in an ice core from the south pole here we report the discovery of volcanic glass shards from a contemporaneous layer in an ice core from summit greenland the major element composition of the glass shards in the greenland sample are identical to those from the south pole confirming the assumption that has been made previously that the sulfuric acid signal in the ice cores is an inter hemispheric time stratigraphic marker the composition of these glass shards is similar to those produced by a 550 700 yrs b p eruption of el chichon volcano in mexico suggesting that it may be the source of the widely dispersed material

challenges in c 14 dating towards the limit of the method inferred from anchoring a floating tree ring radiocarbon chronology to ice core records around the laschamp geomagnetic field minimum the c 14 dating method is the cornerstone for inferring age estimates for natural archives covering the last 50 000 yrs however c 14 age calibration for the last ice age relies mostly on records that only indirectly reflect the atmospheric c 14 concentrations in consequence calendar age estimates are significantly more uncertain for the period of the last ice age compared to the past 14000 yrs where tree ring based calibration records exist here we connect a c 14 tree ring chronology from kauri trees in new zealand to ice core be 10 records via the common signal in the galactic cosmic ray flux around the period of the laschamp geomagnetic field minimum ca 41 000 yrs bp synchronous changes of modelled c 14 and c 14 inferred from u th dated speleothems support the ice core chronology independently and suggest that the published ice core time scale errors are rather conservative for this period our analysis puts c 14 age determinations directly into the context of ice core climate records and it shows that the c 14 records underlying the c 14 calibration curve overestimate the atmospheric c 14 concentration by more than 200 parts per thousand consequently c 14 age calibration presently yields too old calendar age estimates by about 1200 yrs for this period c 2014 elsevier b v all rights reserved less

evidence for a volcanic cooling signal in a 335 year coral record from new caledonia although volcanic cooling events have been detected in tree ring records their occurrence in marine records has received much less attention herein we report results from a 335 year oxygen isotope record 1657 1992 from a new caledonia coral indicating that as many as 16 interannual scale cooling events occur within 1 year of a volcanic eruption as determined by ice core records there are also pentadal decadal scale cooling events beginning in 1675 1813 and 1903 that immediately postdate volcanic eruptions however the interannual correspondences are complicated by the fact that some of the cooling events also coincide with el ninos which cause cooling in this part of the western south pacific if our conclusions are substantiated by further work occurrence of distinct volcanic cooling signals may enable refinement of coral chronologies by use of the event stratigraphic approach with the most promising correlation horizons being associated with the following eruptions 1808 unknown 1813 1821 several eruptions 1835 coseguina 1883 krakatau and possibly 1963 agung

an application of hierarchical bayesian modeling to better constrain the chronologies of upper paleolithic archaeological cultures in france between ca 32 000 21 000 calibrated years before present abstract investigations of chronology play a key role in the majority of archaeological research endeavors and are particularly pertinent to examinations of culture environment relationships especially during periods characterized by rapid and marked climatic variability and environmental reorganization rigorous evaluations of available data and robust methods are required if one wishes to reconstruct reliable chronologies and this is especially the case when examining periods that are associated with a relatively few radiometric measurements such is the case for the upper paleolithic archaeological record documented in present day france from 32 000 to 21 000 calibrated years bp we take into account critically examined radiocarbon measurements from contextually secure archaeological contexts and employ a recently developed method of hierarchical bayesian modeling to reconstruct the chronology of archaeological cultures from the middle gravettian to the badegoulian the calculated chronological intervals for each typo technologically defined culture phase are compared to the greenland ice core climatic record and a terrestrial paleoenvironmental record from bergsee lake southern germany itself expressed in calendar years calculated with the same calibration curve employed in our age model thereby permitting each archaeological culture to be correlated accurately with documented paleoclimatic variability

placing late neanderthals in a climatic context attempts to place stone age events in climatic context are hampered by the difficulty of calibrating the radiocarbon calendar beyond 21 000 radiocarbon years ago and the lack of a master chronology for climate events but there is a way round this problem radiocarbon years can be related to palaeoclimate via the excellent cariaco basin deep sea record in this way the disappearance of neanderthals in europe can be related to known climatic events applying this analysis to dates linked to neanderthal artefacts from gorham s cave gibraltar suggests that they survived there up to the onset of a major environmental shift attempts to place palaeolithic events in climatic context are hampered by the difficulty of calibrating the radiocarbon calendar beyond around 21 000 radiocarbon years ago and the absence of a master calendar chronology for climate events but this is circumvented by relating radiocarbon years to the paleoclimatic record through the excellent cariaco basin deep sea record in this way it is possible to relate the disappearance of neanderthals in europe to known climatic events attempts to place palaeolithic finds within a precise climatic framework are complicated by both uncertainty over the radiocarbon calibration beyond about 21 500 14c years bp1 and the absence of a master calendar chronology for climate events from reference archives such as greenland ice cores or speleothems2 here we present an alternative approach in which 14c dates of interest are mapped directly onto the palaeoclimate record of the cariaco basin by means of its 14c series3 circumventing calendar age model and correlation uncertainties and placing dated events in the millennial scale climate context of the last glacial period this is applied to different sets of dates from levels with mousterian artefacts presumably produced by late neanderthals from gorham s cave in gibraltar first generally accepted estimates of about 32 000 14c years bp for the uppermost mousterian levels4 5 second a possible extended middle palaeolithic occupation until about 28 000 14c years bp6 and third more contentious evidence for persistence until about 24 000 14c years bp6 this study shows that the three sets translate to different scenarios on the role of climate in neanderthal extinction the first two correspond to intervals of general climatic instability between stadials and interstadials that characterized most of the middle pleniglacial and are not coeval with heinrich events in contrast if accepted the youngest date indicates that late neanderthals may have persisted up to the onset of a major environmental shift which included an expansion in global ice volume and an increased latitudinal temperature gradient more generally our radiocarbon climatostratigraphic approach can be applied to any snapshot date from discontinuous records in a variety of deposits and can become a powerful tool in evaluating the climatic signature of critical intervals in late pleistocene human evolution

the volcanic signal in surface temperature observations abstract climate records of the past 140 years are examined for the impact of major volcanic eruptions on surface temperature after the low frequency variations and el nino southern oscillation signal are removed it is shown that for 2 years following great volcanic eruptions the surface cools significantly by 0 1 0 2 c in the global mean in each hemisphere and in the summer in the latitude bands 0 30 s and 0 30 n and by 0 3 c in the summer in the latitude band 30 30 60 n by contrast in the first winter after major tropical eruptions and in the second winter after major high latitude eruptions north america and eurasia warm by several degrees while northern africa and southwestern asia cool by more than 0 5 c because several large eruptions occurred at the same time as enso events the warming produced by the enso masked the volcanic cooling during the first year after the eruption the timescale of the enso response is only 1 year while the volcanic response timescale is 2 years so the coo

experimental evaluation of in situ co2 water rock reactions during co2 injection in basaltic rocks implications for geological co2 sequestration 1 deep aquifers are potential long term storage sites for anthropogenic co2 emissions the retention time and environmental safety of the injected co2 depend on geologic and physical factors and on the chemical reactions between the co2 the aquifer water and the host rocks the ph buffer capacity of the aquifer water and the acid neutralization potential of the host rocks are important factors for the permanent stabilization of the injected co2 mafic rocks such as basalt which primarily consists of ca mg silicate minerals have a high acid neutralization capacity by providing alkaline earth elements that form stable carbonate minerals the carbonate minerals formed thus sequester co2 in a chemically stable and environmentally benign form in this study we present results from a small scale co2 injection test in mafic and metasedimentary rocks the injection test was conducted using a single well push pull test strategy co2 saturated water ph 3 5 was injected into a hydraulically isolated and permeable aquifer interval to study the acid neutralization capacity of ca mg silicate rocks and to estimate in situ cation release rates release rates for ca mg and na were calculated by use of solute compositions of water samples retrieved after the co2 injection the incubation time of the injected solution within the aquifer and geometric estimates of the reactive surface area of the host rocks our results confirm rapid acid neutralization rates and water rock reactions sufficient for safe and permanent storage of co2 carbonic acid was neutralized within hours of injection into a permeable mafic aquifer by two processes mixing between the injected solution and the aquifer water and water rock reactions calculated cation release rates decrease with increasing ph that is confirmed by laboratory based experiments large differences between release rates obtained from the field and laboratory experiments may be mainly due to uncertainties in the estimation of the reactive surface area in the field experiment and in hydrological and geological factors our results underscore the importance of defining bulk rock dissolution rates under in situ conditions in order to evaluate target formations for permanent mineral sequestration of carbon dioxide

regionally consistent western north america paleomagnetic directions from 15 to 35 ka assessing chronology and uncertainty with paleosecular variation psv stratigraphy abstract new paleomagnetic secular variation psv data from fish lake utah usa along with previously published regional records allow us to build an independently dated western north america psv stack wnam17 from about 35 to 15 ka that quantifies dating and paleomagnetic uncertainties in february 2014 we recovered a composite 11 m long sediment record from fish lake utah that retrieved glacially influenced and post glacial sediments computed tomography ct scans and magnetic susceptibility were used to build a precise depth scale while radiocarbon dating of terrestrial macrofossils and tephrostratigraphy provide tight age control glacially influenced sediments have well defined characteristic remanent magnetizations with all maximum angular deviation values

chlorine 36 evidence for the mono lake event in the summit grip ice core abstract a distinct peak has been discovered in the 36 cl data from the grip ice core between the dansgaard oeschger d o events 6 and 7 at approximately 32 kyr bp this peak can be attributed to a minimum of the geomagnetic dipole field associated with the mono lake event since the 36 cl peak reflects a higher production rate of all cosmogenic radionuclides it has an impact on the 14 c dating of the last ice age furthermore it provides an additional time marker similar to a peak found earlier corresponding to the laschamp event at approximately 39 kyr bp

burial dissolution of micrite in middle east carbonate reservoirs jurassic cretaceous keys for recognition and timing abstract this paper discusses burial diagenesis and especially a burial dissolution phase and its effects on micrite microtexture in reservoirs in the middle east three microporous reservoirs were selected the cenomanian mishrif formation in iraq the kimmeridgian tithonian arab d and the barremian kharaib formations both in abu dhabi staining cathodoluminescence and scanning electron microscopy were used for petrographic observations in the selected reservoirs three typical micrite microtextures are distinguished micro rhombic compact anhedral and rounded the chronology of diagenesis based on petrographic observations shows that mineralogical stabilisation through high magnesian calcite replacement by low magnesian calcite led to the formation of micro rhombic micrites non reservoir facies such as seals present compact anhedral micrites correlation between these micrites and high aluminium content suggests alumino silicate minerals clays as a catalyst for pressure dissolution and thus for reservoir degradation through cementation micrites from the upper part of oil reservoirs are dissolved during burial diagenesis dissolution is responsible for rounded shape and for reduction of crystal size it also implies pore diameter and pore throat size enlargement comparison of porosity and permeability with scanning electron microscope data confirms that rounded micrites are better reservoirs than micro rhombic micrites

pattern and forcing of northern hemisphere glacier variations during the last millennium time series depicting mountain glacier fluctuations in the alps display generally similar patterns over the last two centuries as do chronologies of glacier variations for the same interval from elsewhere in the northern hemisphere episodes of glacier advance consistently are associated with intervals of high average volcanic aerosol production as inferred from acidity variations in a greenland ice core advances occur whenever acidity levels rise sharply from background values to reach concentrations 1 2 equiv h kg above background a phase lag of about 10 15 yr equivalent to reported response lags of alpine glacier termini separates the beginning of acidity increases from the beginning of subsequent ice advances a similar relationship but based on limited and less reliable historical data and on lichenometric ages is found for the preceding 2 centuries calibrated radiocarbon dates related to advances of non calving and non surging glaciers during the earlier part of the little ice age display a comparable consistent pattern an interval of reduced acidity values between about 1090 and 1230 a d correlates with a time of inferred glacier contraction during the medieval optimum the observed close relation between noothern hemisphere glacier fluctuations and variations in greenland ice core acidity suggests that sulfur rich aerosols generated by volcanic eruptions are a primary forcing mechanism of glacier fluctuations and therefore of climate on a decadal scale the amount of surface cooling attributable to individual large eruptions or to episodes of eruptions is simlar to the probable average temperature reduction during culminations of little ice age alacier advances ca 0 5 1 2 c as inferred from depression of equilibrium line altitudes

the potential of new zealand kauri agathis australis for testing the synchronicity of abrupt climate change during the last glacial interval 60 000 11 700 years ago abstract the latter part of the last glacial interval lgi 60 000 to 11 700 years ago experienced a range of climatic and environment extremes to elucidate the mechanisms of these changes requires records of past variability that are precisely dated and correlated on the same absolute timescale however despite decades of research it is still not possible to align most marine and terrestrial records of past change with ice core records largely because of ongoing uncertainties over the conversion of pre holocene 14c ages on to a calendar timescale and uncertainties with in ice core chronologies as a result it is equivocal whether climate changes in both hemispheres during the lgi led lagged or were synchronous with one another a decadally resolved radiocarbon calibration is urgently required to test these models of the earth system here we report radiocarbon measurements obtained from subfossil new zealand kauri agathis australis spanning a collective 3500 years dated between 25 000 and 45 000 years ago the results are compared to the recently published international calibration curve intcal09 and to the marine cariaco basin datasets we show that kauri have considerable potential for development of a southern hemisphere component of a unified global calibration curve suite and that tree ring sequences can be superposed on other radiocarbon records to constrain atmospheric marine offsets and precisely test the synchronicity of abrupt climate change

carbonation of ca bearing silicates the case of wollastonite experimental investigations and kinetic modeling abstract carbonation reactions of wollastonite have been investigated in experiments conducted at conditions relevant to geologic co 2 sequestration in subsurface environments t 90 c and pco 2 25 mpa experiments were performed in batch reactors on single mineral powders of selected grain size either in supercritical co 2 or in aqueous solutions with different alkalinities the main reaction products were calcite and amorphous silica calcite occurred either as a compact continuous coating of small crystals in the case of supercritical co 2 and in circum neutral ph aqueous solutions or as isolated larger crystals in acidic aqueous solutions measured extents of carbonation were faster in aqueous solutions than in supercritical co 2 extents of carbonation in aqueous acidic solutions were modelled using a geochemical code incorporating kinetic parameters for wollastonite dissolution and calcite precipitation taken from the literature comparison with experimental results shows that in aqueous solutions wollastonite dissolution is the rate limiting step of the carbonation reaction and that silica layers have only a minor passivation effect on the overall reaction rate in acidic solutions secondary calcite coating has only a minor effect on carbonation extent whereas the experimental data in circum neutral ph aqueous solutions are consistent with dissolution rates inhibited by the observed dense calcite coating a geochemical code incorporating a modified reactive surface model successfully accounted for this passivation effect the more efficient carbonation in acidic than in circum neutral ph solutions is thus ascribed to differences in microstructures of the secondary calcite layers due to differences in supersaturation states of calcite when its precipitation begins inhibitory effects of dense calcite coating are also invoked for limiting carbonation extents of wollastonite in supercritical co 2 secondary calcite precipitations are thus shown to play a major role both as coatings of reactive surfaces and by maintaining large undersaturation with respect to wollastonite dissolution

resolving the differences in the simulated and reconstructed temperature response to volcanism explosive volcanism imposes impulse like radiative forcing on the climate system providing a natural experiment to study the climate response to perturbation previous studies have identified disa

a new model of cosmogenic production of radiocarbon 14c in the atmosphere abstract we present the results of full new calculation of radiocarbon 14c production in the earth atmosphere using a numerical monte carlo model we provide for the first time a tabulated 14c yield function for the energy of primary cosmic ray particles ranging from 0 1 to 1000 gev nucleon we have calculated the global production rate of 14c which is 1 64 and 1 88 atoms cm2 s for the modern time and for the pre industrial epoch respectively this is close to the values obtained from the carbon cycle reservoir inventory we argue that earlier models overestimated the global 14c production rate because of outdated spectra of cosmic ray heavier nuclei the mean contribution of solar energetic particles to the global 14c is calculated as about 0 25 for the modern epoch our model provides a new tool to calculate the 14c production in the earth s atmosphere which can be applied e g to reconstructions of solar activity in the past

assessment of the record of the 1982 el chichon eruption as preserved in greenland snow variability in the so42 and cl time series for the 1980s from 12 shallow snow pits across the greenland ice sheet is used to evaluate the record of the 1982 el chichon eruption and the potential for recording a moderate northern equatorial eruption in a single greenland ice core composition of volcanic glass found in spring 1983 snow in one of the pits in the summit region matches that from el chichon glass thereby verifying the deposition of material from the eruption high na and cl concentrations in this same layer probably represent deposition of the reaction products of halite and h2so4 as observed in the stratosphere following the eruption these findings and the presence of a cl signal in five of the other pits indicate that the cl aerosol component of some eruptions has the potential to remain aloft for at least 1 year after the eruption some of these aerosols may be adsorbed onto tephra particles distinct so42 peaks that can be confidently linked to el chichon were found in only 50 of the records developed through subseasonal sampling however in several other pits an elevated baseline thought to represent more lengthy periods of el chichon aerosol deposition as opposed to deposition from a single snowfall event were observed smoothing of the original data by the calculation of annual so42 flux resulted in the presence of high flux values between 1982 and 1984 years thought to be affected by el chichon aerosol deposition in 9 of the 12 pits these results suggest that a single ice core from anywhere in greenland may record a signal from a northern equatorial eruption of magnitude similar to that of el chichon about 75 of the time this is despite the overall high levels of so2 4 deposition from anthropogenic sources that now make identification and quantification of the volcanic so2 portion of the record more difficult than obtaining the same data for preindustrial volcanism nevertheless composite records from all the pits sampled yielded stratospheric loading 20 mt and optical depth 0 13 estimates similar to stratospheric and satellite based measurements following the eruption equally high so42 concentration and flux values in snow from 1980 to 1982 reflect deposition from the series of middle to high northern latitude volcanic eruptions 1979 1981

the gisp2 δ18o climate record of the past 16 500 years and the role of the sun ocean and volcanoes measured 18o 16o ratios from the greenland ice sheet project 2 gisp2 ice core extending back to 16 500 cal yr b p provide a continuous record of climate change since the last glaciation high resolution annual 18o 16o results were obtained for most of the current millennium a d 818 1985 and record the medieval warm period the little ice age and a distinct 11 yr 18o 16o cycle volcanic aerosols depress central greenland annual temperature 1 5 c maximally and annual 18o 16o for about 4 yr after each major eruptive event on a bidecadal to millennial time scale the contribution of solar variability to holocene greenlandic temperature change is 0 4 c the role of thermohaline circulation change on climate problematic during the holocene is more distinct for the 16 500 10 000 cal yr b p interval analogous to 14c age calibration terminology we express time in calibrated cal yr b p a d 1950 0 cal yr b p the oldest dryas bolling older dryas allerod younger dryas sequence appears in great detail bidecadal variance in 18o 16o but not necessarily in temperature is enhanced during the last phase of lateglacial time and the younger dryas interval suggesting switches of air mass transport between jet stream branches the branched system is nearly instantaneously replaced at the beginning of the bolling and holocene at 14 670 and 11 650 cal yr b p respectively by an atmospheric circulation system in which 18o 16o and annual accumulation initially track each other closely thermodynamic considerations of the accumulation rate temperature relationship can be used to evaluate the 18 o 16o temperature relationship the gisp2 ice layer count years of major gisp2 climate transitions also support the use of coral 14c ages for age calibration

european summer temperature response to annually dated volcanic eruptions over the past nine centuries the drop in temperature following large volcanic eruptions has been identified as an important component of natural climate variability however due to the limited number of large eruptions that occurred during the period of instrumen tal observations the precise amplitude of post volcanic cooling is not well constrained here we present new evidence on summer temperature cooling over europe in years following volcanic eruptions we compile and analyze an updated net work of tree ring maximum latewood density chronologies spanning the past nine centuries and compare cooling sig natures in this network with exceptionally long instru mental station records and state of the art general circu lation models results indicate post volcanic june august cooling is strongest in northern europe 2 years after an eruption 0 52 0 05 c whereas in central europe the temperature response is smaller and occurs 1 year after an eruption 0 18 0 07 c we validate these estimates by comparisonwith the shorter instrumental network and evaluate the statistical significance of post volcanic summer tempera ture cooling in the context of natural climate variability over the past nine centuries finding no significant post volcanic temperature cooling lasting longer than 2 years our results question the ability of large eruptions to initiate long term temperature changes through feedback mechanisms in the climate system we discuss the implications of these findings with respect to the response seen in general circulation models and emphasize the importance of considering well documented annually dated eruptions when assessing the

the influence of volcanic eruptions on growth of central european lowland trees in ne germany during the last millennium abstract palaeoclimate proxies have shown links between climate changes and volcanic activity however not much is known about the impact of volcanic outbursts on growth of lowland trees we investigate the effect of large volcanic eruptions on the growth rate of trees the study is based on an unexplored comprehensive database with 1128 samples of long tree ring width trw chronologies of quercus robur l and pinus sylvestris l correlating with forest net primary production npp originating from three different sites in eastern germany greifswald eberswalde and saxony this study focuses on trees in rarely examined temperate zones where tree growth is less temperature limited growth relationships were compared against 52 large volcanic eruptions known for the last 1000 years dendrochronological methods revealed a predominantly negative 60 2 effect of large volcanic eruptions on the tree ring chronologies nevertheless also positive 31 7 and neutral 8 7 tree growth reactions were detected in the tree ring width chronologies of q robur and p sylvestris we detected a negative influence on tree growth for up to four years after large eruptions the chronologies of q robur revealed a stronger negative response 68 1 than those of p sylvestris 53 however at the greifswald site both tree species 79 q robur and 73 p sylvestris show a negative response in tree growth after every volcanic eruption furthermore the results suggest that volcanic aerosols originating from the northern hemisphere cause a greater reduction in tree growth than aerosols being emitted from southern hemisphere volcanoes which might be related to the long distances between trees and volcanoes as well as the global atmospheric circulation patterns this study demonstrates that the effects of major volcanic eruptions are less clear in trees from central european lowlands than in trees growing at the altitudinal or latitudinal timberlines

visual stratigraphic dating of the gisp2 ice core basis reproducibility and application annual layers are visible in the greenland ice sheet project 2 ice core from central greenland allowing rapid dating of the core changes in bubble and grain structure caused by near surface primarily summertime formation of hoar complexes provide the main visible annual marker in the holocene and changes in cloudiness of the ice correlated with dustiness mark wisconsinan annual cycles both markers are evident and have been intercalibrated in early holocene ice layer counts are reproducible between different workers and for one worker at different times with 1 error over century length times in the holocene reproducibility is typically 5 in wisconsinan ice age ice and decreases with increasing age and depth cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50 000 years visible observations are not greatly degraded by brittle ice or many other core quality problems allowing construction of long consistently sampled time series high accuracy requires careful study of the core by dedicated observers

radiocarbon calibration uncertainties during the last deglaciation insights from new floating tree ring chronologies abstract radiocarbon dating is the most commonly used chronological tool in archaeological and environmental sciences dealing with the past 50 000 years making the radiocarbon calibration curve one of the most important records in paleosciences for the past 12 560 years the radiocarbon calibration curve is constrained by high quality tree ring data prior to this however its uncertainties increase rapidly due to the absence of suitable tree ring 14c data here we present new high resolution 14c measurements from 3 floating tree ring chronologies from the last deglaciation by using combined information from the current radiocarbon calibration curve and ice core 10be records we are able to absolutely date these chronologies at high confidence we show that our data imply large 14c age variations during the bolling chronozone greenland interstadial 1e a period that is currently characterized by a long 14c age plateau in the most recent intcal13 calibration record we demonstrate that this lack of structure in intcal13 may currently lead to erroneous calibrated ages by up to 500 years

the late pleistocene palaeoenvironmental evolution in northern eurasia through the prism of the mollusc shell based esr dating evidence abstract long term investigations devoted mostly to the eurasian arctic sedimentary deposits have provided dated climatic sequence within the late pleistocene period most of the dates ca 315 were obtained by electron spin resonance esr method on marine mollusc remains taken directly from transgressive marine sedimentary deposits here it is shown that the climatic signature revealed in the studied sedimentary sequences can be compared by proxy and chronologic correlation with the climatic signals recorded in different parts of the continent from deposits of marine freshwater and terrestrial origin the resulting climate chronostratigraphic record allow the last interglacial to be placed approximately between 145 140 ka and 70 ka with concentration of overwhelming majority of the warm climate related dates ca 82 in the second half of marine isotope stage mis 5 in the time range between 110 and 70 ka this evidence coincides with integrative multidisciplinary results derived from the south eastern coast of the gulf of finland they show unambiguously that the second half of the mis 5 sequence at least between ca 94 ka and 71 ka reflects the fully interglacial character of the studied deposits the climate chronostratigraphic record within mis 3 displays a sequence of three successive palaeoenvironmental events 59 0 52 0 ka 47 5 40 0 ka and 32 4 24 8 ka which are interpreted as the consequence of large scale climate amelioration during which marine sedimentation occurred on palaeo shelves what is now dry land the consistency of the parallel comparative dating results obtained in this study by different methods both the numerical and relative exemplify the potential of palaeodosimetric dating methods mainly used in this study mollusc shell based electron spin resonance esr and feldspar based infrared optically stimulated luminescence ir osl to chronologically organize the sequence of the late pleistocene palaeoenvironmental events and to improve understanding of the palaeoenvironmental evolution during this period

lateglacial environmental variability from swiss tree rings abstract evidence of annually resolved environmental variations during the allerod interstadial is presented using 81 fossil scots pine tree ring series from gaenziloo and landikon near zurich switzerland the absolute age of the trees ranges between 11 920 and 10 610 14 c bp which was determined by wiggle matching radiocarbon ages to the cariaco 14 c data set from the two sites we created a composite floating allerod chronology on the basis of their 632 years of overlap r 0 57 after individual spline detrending merging both data sets resulted in a lateglacial tree ring chronology covering 1050 years regional curve standardization rcs was applied to preserve low frequency information growth behavior of the fossil trees was compared with a recent composite pine data set from the central swiss alps and reveals distinct differences the new allerod rcs chronology reveals major lateglacial variations such as the gerzensee oscillation the abrupt climate shift towards the younger dryas and some short term events radiocarbon ages agree well with those from other sites on the swiss plateau for hemispheric comparisons we used the annual layer thickness record from the ngrip ice core and the gray scale varve record from the cariaco basin even though the amplitudes are not yet fully understood similarities on decadal to centennial scales are apparent

tree ring and summer temperature response to volcanic aerosol forcing at the northern tree line kola peninsula russia potential linkages between volcanic activity and a 403 year record of pinus sylvestris l scots pine growth and summer temperatures estimated from tree ring widths are evaluated from an arctic tree line site on the kola peninsula northwestern russia the joint occurrence of volcanic eruptions and severe negative ring width values is more than four times that expected by chance a composite average of temperatures indicates that a 0 72 c temperature reduction is typical for the year immediately following volcanic eruptions while tree growth is reduced for up to two decades the greenland ice sheet project 2 gisp2 volcanic sulphate record shows a small but significant correlation with summer temperatures volcanic aerosols originating at low and middle latitudes appear to cause the greatest ring width reduction and cooling

atmospheric 14c variations derived from tree rings during the early younger dryas abstract atmospheric radiocarbon variations over the younger dryas interval from 13 000 to 11 600 cal yr bp are of immense scientific interest because they reveal crucial information about the linkages between climate ocean circulation and the carbon cycle however no direct and reliable atmospheric 14c records based on tree rings for the entire younger dryas have been available in this paper we present 1 high precision 14c measurements on the extension of absolute tree ring chronology from 12 400 to 12 560 cal yr bp and 2 high precision high resolution atmospheric 14c record derived from a 617 yr long tree ring chronology of huon pine from tasmania australia spanning the early younger dryas the new tree ring 14c records bridge the current gap in european tree ring radiocarbon chronologies during the early younger dryas linking the floating lateglacial pine record to the absolute tree ring timescale a continuous and reliable atmospheric 14c record for the past 14 000 cal yr bp including the younger dryas is now available the new records indicate that the abrupt rise in atmospheric 14c associated with the younger dryas onset occurs at 12 760 cal yr bp 240 yrs later than that recorded in cariaco varves with a smaller magnitude of 40 followed by several centennial 14c variations of 20 25 comparing the tree ring 14c to marine derived 14c and modelled 14c based on ice core 10be fluxes we conclude that changes in ocean circulation were mainly responsible for the younger dryas onset while a combination of changes in ocean circulation and 14c production rate were responsible for atmospheric 14c variations for the remainder of the younger dryas

tree ring evidence for climatically effective volcanic eruptions abstract ringwidth variations from temperature sensitive upper timberline sites in the sierra nevada show a marked correspondence to the decadal pattern of volcanic sulfate aerosols recorded in a greenland ice core acidity profile and a significant negative growth response to individual explosive volcanic events the appearance of single events in the mid latitude tree ring record in connection with ice core evidence from the arctic and historical records from the mediterranean indicates that the majority of these events represent climatically effective volcanic eruptions producing temperature decreases on the order of 1 c for up to 2 yr after the initial eruption clusters of climatically effective volcanic events may serve as a trigger to glaciation and are consistently associated with lowered ringwidths and late holocene glacier advance in the sierra nevada the tree ring record strongly suggests forcing of solar radiation receipt and temperatures by increased volcanic aerosols especially during the recess peak advances and matthes little ice age advances from 1400 to 1850 a d intervals with an absence of significant volcanic aerosol production or historically documented eruptive activity correspond to intervals of significantly increased indexed ringwidth values minimal numbers of severe annual negative ringwidth anomalies and an absence of glacial deposits in the southern sierra nevada

timing and climatic impact of greenland interstadials recorded in stalagmites from northern turkey a 50 kyr long exceptionally well dated and highly resolved stalagmite oxygen 18o and carbon 13c isotope record from sofular cave in northwestern turkey helps to further improve the dating of greenland interstadials gi 1 and 3 12 timing of most gi in the sofular record is consistent within 10 to 300 years with the iconic hulu cave record larger divergences 500 years between sofular and hulu are only observed for gi 4 and 7 the sofular record differs from the most recent ngrip chronology by up to several centuries whereas age offsets do not increase systematically with depth the sofular record also reveals a rapid and sensitive climate and ecosystem response in the eastern mediterranean to gi whereas a phase lag of 100 years between climate and full ecosystem response is evident finally results of spectral analyses of the sofular isotope records do not support a 1 470 year pacing of gi

changes in the carbon cycle during the last deglaciation as indicated by the comparison of 10be and 14c records the variations in atmospheric radiocarbon c 14 concentration during the last 50 000 years can be attributed to changes in the c 14 production rate due to changes in solar activity the geomagnetic field and or interstellar galactic cosmic ray flux and to changes in the global carbon cycle the relative contributions of these processes is the subject of current debate although the discrepancies between the various reconstructions of the past atmospheric radiocarbon concentration increase with age the relatively good agreement over the last 25 000 years allows a quantitative discussion of the causes of the observed c 14 variations for this period using be 10 measurements from greenland summit ice cores we show that in addition to solar and geomagnetically induced production rate changes significant changes in the carbon cycle have to be considered to explain the measured c 14 concentrations there is evidence that these changes are connected to 1 global deglaciation and 2 climate changes in the north atlantic region on centennial to millennial time scales related to changes in the ocean circulation differences between be 10 and geomagnetic field records however suggest that uncertainties of about 20 still exist in determinations of past changes in the c 14 production rate c 2004 elsevier b v all rights reserved less

reaction of plagioclase feldspars with co2 under hydrothermal conditions abstract geological storage of co 2 in plagioclase bearing sediments granitic rocks and fractured basalts is expected to have a variety of geochemical and geomechanical effects including mineral trapping and porosity permeability changes the amount of co 2 trapped by mineralisation and the extent of any changes in host rock transport or mechanical properties depend on rock composition to date studies of mineralisation have mainly been based on dissolution and precipitation experiments performed at ambient surface conditions or at slightly elevated temperature and pressure however the reactions that occur under in situ conditions are poorly constrained in an attempt to determine the secondary phases formed in the plagioclase co 2 water system under such conditions we performed a set of batch experiments at temperatures in the range 200 300 c using carbon dioxide pressures from 0 4 to 15 mpa we investigated reaction of anorthite and albite which are expected to precipitate calcite and kaolinite and dawsonite and quartz respectively however in most of our experiments reactions precipitating clays kaolinite and smectite or illite boehmite and a mg ni fe hydrotalcite like phase dominated the nickel being derived from the reaction vessel little or no carbonate and no dawsonite were detected additional feldspar free control experiments employing mg rich brine showed that carbonates would be preserved in our feldspar experiments if formed but that a carbonate substrate is needed to promote precipitation since the secondary phases formed in our plagioclase experiments are stable under a wide range of conditions we expect that they will also form under co 2 storage systems with suitable fluid rock composition from our results we conclude that clay precipitation can proceed or accompany carbonate precipitation depending on the availability of carbonate substrate though an artefact in our experiments in the context of subsurface alkaline waste injection hydrotalcite may play a positive role here by immobilising heavy metals while carbonates will mineralise the co 2

dating synthesis and interpretation of palaeoclimatic records of the last glacial cycle and model data integration advances by the intimate integration of ice core marine and terrestrial records cost action es0907 since 2010 the intimate integration of ice core marine and terrestrial records network has been operating as a cost action designated es0907 this paper outlines the accomplishments of the intimate cost action in the context of how the intimate ideas have evolved during the network s twenty year life span and highlights a number of challenges that can guide further work in the second part of the paper the contributions that comprise this intimate special issue are introduced

cosmic ray event of a d 774 775 shown in quasi annual 10be data from the antarctic dome fuji ice core 14c content in tree rings and 10be concentration records in polar ice core provide information about past cosmic ray intensities the a d 774 775 cosmic ray event has been identified by 14c measurement in several tree rings from all over the world although the quasi decadal 10be dome fuji data in the antarctic ice core also shows a sharp peak around a d 775 annual 10be variations in the dome fuji core or in other cores have not been revealed we have measured quasi annual 10be concentrations from approximately a d 763 794 in the dome fuji ice core and detected a clear increase 80 above the baseline in 10be concentration around a d 775 however an accurate height of this increase is not straightforwardly estimated due to the background variation in 10be concentration the 10be increase can be due to the same cosmic ray event as shown in the 14c content in a d 774 775

do volcanic eruptions enhance or diminish net primary production evidence from tree rings 1 low growth rates of atmospheric co2 were observed following the 1991 pinatubo luzon volcanic eruption one hypothesis for this co2 anomaly is that since diffuse light is more efficiently used by forests than direct light the increase in the diffuse fraction of sunlight due to scattering by volcanic sulfur aerosol in the years following the eruption substantially increased forest net primary production npp however other observations suggest a decrease in northern forest npp because of the cooler conditions following the eruption here we used a global database of dated tree ring widths which correlate with forest npp to test this hypothesis ice core records of sulfur deposition allowed us to identify the timing and magnitude of 23 pinatubo scale eruptions since 1000 ce we found a significant decrease in ring width for trees in middle to high northern latitudes north of 45 n following eruption sulfur peaks decreases in tree ring widths were in the range of 2 8 and persisted for 8 years following sulfur peaks with minima at around 4 6 years ring width changes at lower latitudes in the northern hemisphere 30 n to 45 n and in the southern hemisphere 30 s to 56 s were not significant in the tropics 30 n to 30 s the paucity of tree ring records did not permit the evaluation of npp changes given that elevated aerosol levels and summer cooling last only 2 3 years after an eruption the persistence of declines in northern tree growth for up to 8 years after eruptions implies some additional mechanism that links these shorter lived global eruption effects to sustained changes in tree physiology biogeochemistry or microclimate at least for this sample of trees the beneficial effect of aerosol light scattering appears to be entirely offset by the deleterious effect of eruption induced climate change

global surface temperature responses to major volcanic eruptions the impacts of pollution resulting from large explosive volcanic eruptions on the atmospheric heat budget and planetary albedo are not in doubt1 2 however the effects of volcanic aerosols on the surface climate are less clear and still controversial3 4 in a previous study5 it was shown that significant surface cooling occurs over the landmasses of the northern hemisphere in the first few months after a major eruption in that hemisphere here we extend that work using new surface air temperature compilations based on land and marine data6 for both the northern and southern hemispheres our results indicate that major northern hemisphere eruptions have an immediate effect on the northern hemisphere average surface temperature but little or no effect on the southern hemisphere average southern hemisphere eruptions affect both southern and northern hemisphere temperatures after a lag of between six months and a year

the response of the north pacific decadal variability to strong tropical volcanic eruptions in this study the effects of volcanic forcing on north pacific climate variability on interannual to decadal time scales are examined using climate model simulations covering the last 600 years the model used is the bergen climate model a fully coupled atmosphere ocean general circulation model it is found that natural external forcings such as tropical strong volcanic eruptions sves and variations in total solar irradiance play an important role in regulating north pacific decadal variability npdv in response to tropical sves the lower stratospheric pole to equator temperature gradient is enhanced the north polar vortex is strengthened which forces a significant positive arctic oscillation at the same time dipole zonal wind anomalies associated with strong polar vortex propagate downward from the lower stratosphere through positive feedbacks in the troposphere the surface westerly winds across the central north pacific are significantly weakened and positive sea level pressure anomalies are formed in the north pacific this anomalous surface circulation results in changes in the net heat fluxes and the oceanic advection across the north pacific as a result of this warm water converges in the subtropical western north pacific where the surface waters in addition are heated by significantly reduced latent and sensible heat fluxes from the ocean in the eastern and high latitude north pacific the ocean loses more heat and large scale decreases in sea surface temperatures are found the overall response of this chain of events is that the north pacific enters a negative phase of the pacific decadal oscillation pdo and this negative phase of the pdo is maintained for several years it is thus concluded that the volcanic forcing plays a key role in the phasing of the pdo the model results furthermore highlight the important role of troposphere stratosphere coupling tropical extratropical teleconnections and extratropical ocean atmosphere interactions for describing npdv

low frequency temperature variations from a northern tree ring density network we describe new reconstructions of northern extratropical summer temperatures for nine subcontinental scale regions and a composite series representing quasi northern hemisphere temperature change over the last 600 years these series are based on tree ring density data that have been processed using a novel statistical technique age band decomposition designed to preserve greater long timescale variability than in previous analyses we provide time dependent and timescale dependent uncertainty estimates for all of the reconstructions the new regional estimates are generally cooler in almost all precalibration periods compared to estimates obtained using earlier processing methods particularly during the 17th century one exception is the reconstruction for northern siberia where 15th century summers are now estimated to be warmer than those observed in the 20th century in producing a new northern hemisphere series we demonstrate the sensitivity of the results to the methodology used once the number of regions with data and the reliability of each regional series begins to decrease we compare our new hemisphere series to other published large regional temperature histories most of which lie within the 1 confidence band of our estimates over most of the last 600 years the 20th century is clearly shown by all of the palaeoseries composites to be the warmest during this period

the δ18o record along the greenland ice core project deep ice core and the problem of possible eemian climatic instability over 70 000 samples from the 3029 m long greenland ice core project grip ice core drilled on the top of the greenland ice sheet summit have been analyzed for 8o a highly detailed and continuous 8o profile has thus been obtained and is discussed in terms of past temperatures in greenland we also discuss a three core stacked annual 8o profile for the past 917 years the short term 50 years variability of the annual 8o signal is found to be 1 in the holocene and estimates for the coldest parts of the last glacial are 3 or higher these data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the eemian spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the 8o signal which for the holocene ice is found to be considerably stronger than expected we suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix deconvolution techniques were employed for restoring with great confidence the highly attenuated annual 8o signal in the holocene we confirm earlier findings of dramatic temperature changes in greenland during the last glacial cycle abrupt and strong climatic shifts are also found within the eem sangamon interglaciation which is normally recorded as a period of warm and stable climate in lower latitudes the stratigraphic continuity of the eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile

atmospheric 14c 12c changes during the last glacial period from hulu cave paired measurements of 14c 12c and 230th ages from two hulu cave stalagmites complete a precise record of atmospheric 14c covering the full range of the 14c dating method 54 000 years over the last glacial period atmospheric 14c 12c ranges from values similar to modern values to values 1 70 times higher 42 000 to 39 000 years ago the latter correspond to 14c ages 5200 years less than calibrated ages and correlate with the laschamp geomagnetic excursion followed by heinrich stadial 4 millennial scale variations are largely attributable to earth s magnetic field changes and in part to climate related changes in the oceanic carbon cycle a progressive shift to lower 14c 12c values between 25 000 and 11 000 years ago is likely related in part to progressively increasing ocean ventilation rates

a geomagnetic chronology for antarctic ice accumulation the curve of 10be flux versus age in the vostok ice core largely covaries with a synthetic curve calculated assuming that a large fraction of 10be production rate is modulated by changes in the geomagnetic field intensity with this assumption it is also possible to derive a precise chronology for the vostok core this chronology is in good agreement with a very recent glaciological chronology obtained for vostok ice core and improves the correspondence of climate events recorded in antarctic ice with correlative events recorded in deep sea sediments therefore the idea that changes in the 10be flux at vostok may arise from variations in earth s geomagnetic dipole field has to be seriously considered this would imply that a large portion of the 10be deposited there is derived from lower latitudes

last millennium northern hemisphere summer temperatures from tree rings part i the long term context abstract large scale millennial length northern hemisphere nh temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed this paper and its companion part ii anchukaitis et al in prep details the latest tree ring tr based nh land air temperature reconstruction from a temporal and spatial perspective this work is the first product of a consortium called n trend n orthern hemisphere tre e ring n etwork d evelopment which brings together dendroclimatologists to identify a collective strategy for improving large scale summer temperature reconstructions the new reconstruction n trend2015 utilises 54 records a significant expansion compared with previous tr studies and yields an improved reconstruction with stronger statistical calibration metrics n trend2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time scales from 918 to 2004 where at least 3 tr records exist from each major continental mass n trend2015 indicates a longer and warmer medieval period 900 1170 than portrayed by previous tr nh reconstructions and by the cmip5 model ensemble but with better overall agreement between records for the last 600 years future dendroclimatic projects should focus on developing new long records from data sparse regions such as north america and eastern eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring width records which can improve local based calibration substantially

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

reconciling the greenland ice core and radiocarbon timescales through the laschamp geomagnetic excursion abstract cosmogenic radionuclides such as 10be and 14c share a common production signal with their formation in the earth s upper atmosphere modulated by changes to the geomagnetic field as well as variations in the intensity of the solar wind here we use this common production signal to compare between the radiocarbon intcal and greenland ice core gicc05 timescales utilising the most pronounced cosmogenic production peak of the last 100 000 years that associated with the laschamp geomagnetic excursion circa 41 000 years ago we present 54 new 14c measurements from a peat core tp 2005 from tenaghi philippon ne greece contiguously spanning between circa 47 300 and 39 600 cal bp demonstrating a distinctive tripartite structure in the build up to the principal laschamp production maximum that is not present in the consensus intcal13 calibration curve this is the first time that a continuous non reservoir corrected 14c dataset has been generated over such a long time span for this the oldest portion of the radiocarbon timescale this period is critical for both palaeoenvironmental and archaeological applications with the replacement of neanderthals by anatomically modern humans in europe around this time by placing our tenaghi philippon 14c dataset on to the hulu cave u series timescale of cheng et al 2018 via bayesian statistical modelling the comparison of tp 2005 14c with greenland 10be fluxes also implicitly relates the underlying u series and gicc05 timescales themselves this comparison suggests that whilst these two timescales are broadly coherent the intcal13 timescale contains erroneous structure circa 40 000 cal bp

consistently dated records from the greenland grip gisp2 and ngrip ice cores for the past 104 ka reveal regional millennial scale δ18o gradients with possible heinrich event imprint abstract we present a synchronization of the ngrip grip and gisp2 ice cores onto a master chronology extending back to 104 ka before present providing a consistent chronological framework for these three greenland records the synchronization aligns distinct peaks in volcanic proxy records and other impurity records chemo stratigraphic matching and assumes that these layers of elevated impurity content represent the same instantaneous event in the past at all three sites more than 900 marker horizons between the three cores have been identified and our matching is independently confirmed by 24 new and previously identified volcanic ash tephra tie points using the reference horizons we transfer the widely used greenland ice core chronology gicc05modelext to the two summit cores grip and gisp2 furthermore we provide gas chronologies for the summit cores that are consistent with the gicc05modelext timescale by utilizing both existing and new gas data ch4 concentration and 15n of n2 we infer that the accumulation contrast between the stadial and interstadial phases of the glacial period was 10 greater at summit compared to at ngrip the 18o temperature proxy records from ngrip grip and gisp2 are generally very similar and display synchronous behaviour at climate transitions the 18o differences between summit and ngrip however changed slowly over the last glacial interglacial cycle and also underwent abrupt millennial to centennial scale variations we suggest that this observed latitudinal 18o gradient in greenland during the glacial period is the result of 1 relatively higher degree of precipitation with a pacific signature at ngrip 2 increased summer bias in precipitation at summit and 3 enhanced rayleigh distillation due to an increased source to site distance and a potentially larger source to site temperature gradient we propose that these processes are governed by changes in the north american ice sheet nais volume and north atlantic sea ice extent and or sea surface temperatures sst on orbital timescales and that changing sea ice extent and ssts are the driving mechanisms on shorter timescales finally we observe that maxima in the summit ngrip 18o difference are roughly coincident with prominent heinrich events this suggests that the climatic reorganization that takes place during stadials with heinrich events possibly driven by a southward expansion of sea ice and low ssts in the north atlantic are recorded in the ice core records

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

use of paleo records in determining variability within the volcanism climate system abstract volcanic eruptions that inject large quantities of sulfur rich gases into the stratosphere have the capability of cooling global climate by 0 2 0 3 c for several years after the eruption equatorial eruptions will impact global climate whereas mid latitude eruptions can cool climate in the hemisphere of origin magnitude of cooling varies by latitude and it is possible for warming to occur in certain regions primarily during the winter although instrumental records have been used to quantify the volcanic impact on climate they are limited in their temporal and spatial coverage and the style and magnitude of eruptions occurring over the two centuries of instrumental records is limited a thorough evaluation of the range of variability in the volcanism climate system requires a multidisciplinary approach that includes the analysis of ice core records geological data atmospheric measurements and visual phenomena tree ring records and other proxy data evaluation of these longer time series indicates that multiple volcanic eruptions have the potential to force climate over decadal to multi decadal time frames especially when these eruptions enhance or extend pre existing cool conditions on the other hand a lack of climatically significant eruptions may result in warmer average temperatures over decadal time frames because the volcanic cooling component within the climate system is absent mega eruptions like the toba eruption of 71 000 73 000 yr ago may impact climate on centennial time frames through positive feedback mechanisms evidence exists which indicates that environmental changes associated with rapid climatic fluctuations such as crustal loading unloading with glaciation deglaciation and variability in glacial meltwater loading on ocean basins may cause an increase in volcanic activity

presence of the solar de vries cycle 205 years during the last ice age certain characteristic periodicities in the 14c record from tree rings such as the well known 11 yr schwabe cycle are known to be of solar origin the origin of longer period cycles such as the 205 yr de vries cycle in the 14c record was less certain and it was possible to attribute it either to solar or climatic variability here we demonstrate that the de vries cycle is present in 10be data from the grip ice core during the last ice age 25 to 50 kyr bp analysis of the amplitude of variation of this cycle shows it to be modulated by the geomagnetic field indicating that the de vries cycle is indeed of solar rather than climatic origin

a complete terrestrial radiocarbon record for 11 2 to 52 8 kyr b p radiocarbon 14c provides a way to date material that contains carbon with an age up to 50 000 years and is also an important tracer of the global carbon cycle however the lack of a comprehensive record reflecting atmospheric 14c prior to 12 5 thousand years before the present kyr b p has limited the application of radiocarbon dating of samples from the last glacial period here we report 14c results from lake suigetsu japan 35 35 n 135 53 e which provide a comprehensive record of terrestrial radiocarbon to the present limit of the 14c method the time scale we present in this work allows direct comparison of lake suigetsu paleoclimatic data with other terrestrial climatic records and gives information on the connection between global atmospheric and regional marine radiocarbon levels

radiocarbon calibration beyond 20 000 14c yr b p by means of planktonic foraminifera of the iberian margin we present a new set of 14c ages obtained by accelerator mass spectrometry ams on planktonic foraminifera from a deep sea core collected off the iberian margin md952042 this site at 37 n is distant from the high latitude zones where 14c reservoir age is large and variable many independent proxies alkenones magnetic susceptibility ice rafted debris foraminifera stable isotopes abundances of foraminifera pollen and dinoflagellates show abrupt changes correlative with dansgaard oeschger and heinrich events of the last glacial period the good stratigraphic agreement of all proxies from the fine to the coarse size fractions indicates that the foraminifera 14c ages are representative of the different sediment fractions to obtain reliable 14c ages of foraminifera beyond 20 000 14c yr b p we leached the shells prior to carbonate hydrolysis and subsequent analysis for a calendar age scale we matched the iberian margin u37k profile with that of greenland summit 18o both are proxies for temperature which in models varies synchronously in the two areas the match creates no spurious jumps in sedimentation rate and requires only a limited number of tie points except for ages older than 40 000 14c yr b p greenland s gisp2 and grip records yield similar calendars the 14c and imported calendar ages of the iberian margin record are then compared to data from lacustrine annual varves and from corals and speleothems dated by u th previously used to extend the calibration beyond 20 000 14c yr b p the new record follows a smooth pattern between 23 000 and 50 000 cal yr b p we find good agreement with the previous data sets between 23 000 and 31 000 cal yr b p in the interval between 33 000 and 41 000 cal yr b p for which previous records disagree by up to 5000 cal yr the iberian margin record closely follows the polynomial curve that was previously defined by an interpolation of the coral ages and runs between the lake suigetsu and the bahamian speleothem data sets

irish tree rings santorini and volcanic dust veils there has recently been renewed interest in the dating of the violent eruption of the aegean island of santorini in the second millennium bc both by its possible effects on tree ring growth in the united states1 suggesting a date of 1628 1626 bc and by acidity peaks in ice cores from south greenland2 suggesting 1645 bc we now show that oak trees growing on bogs in northern ireland produce significant concentrations of extremely narrow rings within a few periods less than 20 years long and that these periods correspond to the dates suggested by other methods for major volcanic eruptions in particular one of them corresponding to a short period beginning in 1628 bc was probably caused by santorini this date is qualitatively better than those derived from carbon 14 or ice cores because it is based on an absolute tree ring chronology

volcanic cooling signal in tree ring temperature records for the past millennium the authors acknowledge the national science foundation for funding much of the research presented herein rw s scottish work is currently funded through the uk leverhulme trust and natural environment research council nerc projects relic reconstructing 8000 years of environmental and landscape change in the cairngorms f 00 268 bg and scot2k reconstructing 2000 years of scottish climate from tree rings ne k003097 1

quantifying the global carbon cycle response to volcanic stratospheric aerosol radiative forcing using earth system models 1 large volcanic eruptions can have a significant cooling effect on climate which is evident in both modern and palaeo data however due to the difficulty of disentangling volcanic and other influences in the modern atmospheric co2 record and uncertainties associated with palaeo reconstructions of atmospheric co2 the magnitude of the carbon cycle response to volcanically induced climatic changes is difficult to quantify in this study three earth system models simearth climber 2 and climber lpj are used to simulate the effects of different magnitudes of volcanic eruption from relatively small e g mount pelee 1902 to very large e g the 1258 ice core event on the coupled global climate carbon cycle system these models each use different but justifiable parameterizations to simulate the global carbon cycle and climate key differences include how soil respiration and net primary productivity respond to temperature and atmospheric co2 all models simulate global surface cooling in response to volcanic events in response to a mount pinatubo equivalent eruption the modelled temperature decrease is 0 3 c to 0 4 c and atmospheric co2 decreases by 1 1 ppm to 3 4 ppm the initial response time of climate to volcanic forcing and subsequent recovery time vary little with changes in the size of the forcing response times for vegetation and soil carbon are relatively consistent across forcings for each model however results indicate that there is significant uncertainty concerning the response of the carbon cycle to volcanic eruptions suggestions for future research directed at reducing this uncertainty are given

tree rings and ice cores reveal c 14 calibration uncertainties during the younger dryas the younger dryas interval during the last glacial termination was an abrupt return to glacial like conditions punctuating the transition to a warmer interglacial climate despite recent advances in the layer counting of ice core records of the termination the timing and length of the younger dryas remain controversial also a steep rise in the concentration of atmospheric radiocarbon at the onset of the interval recorded primarily in the cariaco basin has been difficult to reconcile with simulations of the younger dryas carbon cycle here we discuss a radiocarbon chronology from a tree ring record covering the late glacial period that has not been absolutely dated we correlate the chronology to ice core timescales using the common cosmic production signal in tree ring 14c and ice core 10be concentrations the results of this correlation suggest that the cariaco record may be biased by changes in the concentration of radiocarbon in the upper ocean during the early phase of the younger dryas climate reversal in the cariaco basin this bias in the marine record may also affect the accuracy of a widely used radiocarbon calibration curve over this interval our tree ring based radiocarbon record is easily reconciled with simulated production rates and carbon cycle changes associated with reduced ocean ventilation during the younger dryas attaching a floating tree ring chronology to ice core records that cover the abrupt younger dryas cold interval during the last glacial termination provides a better estimate of the onset and duration of the radiocarbon anomaly the chronology suggests that marine records may be biased by changes in the concentration of radiocarbon in the ocean which may affect the accuracy of a popular radiocarbon calibration program during this interval

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

40ar 39ar k ar and 230th 238u dating of the laschamp excursion a radioisotopic tie point for ice core and climate chronologies abstract a brief period of enhanced 10 be flux that straddles the interstadial warm period known as dansgaard oeschger event 10 in greenland and its counterpart in antarctica the antarctic isotope maximum 10 is but one consequence of the weakening of earth s magnetic field associated with the laschamp excursion this 10 be peak measured in the grip ice core is dated at 41 250 y b2k before year 2000 ad in the most recent gicc05 age model obtained from the northgrip core via multi parameter counting of annual layers uncertainty in the age of the 10 be peak is however no better than 1630 y at the 95 confidence level reflecting accumulated error in identifying annual layers the age of the laschamp excursion guillou h singer b s laj c kissel c scaillet s jicha b 2004 on the age of the laschamp geomagnetic excursion earth planet sci lett 227 331 343 is revised on the basis of new 40 ar 39 ar unspiked k ar and 238 u 230 th data from three lava flows in the massif central france together with the 40 ar 39 ar age of a transitionally magnetized lava flow at auckland new zealand combined these data yield an age of 40 700 950 y b2k where the uncertainty includes both analytical and systematic 40 k and 230 th decay constant errors taking the radioisotopic age as a calibration tie point suggests that the layer counting chronologies for the northgrip and gisp2 ice cores are more accurate and precise than previously thought at depths corresponding to the laschamp excursion

an inter hemispheric volcanic time marker in ice cores from greenland and antarctica a strong volcanic acid signal is clearly registered using an acidity measuring technique in the a d 1259 ice layer in four different greenland ice cores camp century milcent crete and dye 3 this signal is similar in amplitude to the laki iceland a d 1783 volcanic event as recorded in the central and south greenland ice cores measurement of ice layers from corresponding age levels in antarctic ice cores byrd station south pole and j 9 on the ross ice shelf provides similar strong acid signals there is no historical record of a significant volcanic eruption for the period around a d 1260 in the northern hemisphere subsequent chemical analyses of all a d 1259 ice layers show similar compositions we suggest that the a d 1259 signals registered in both greenland and antarctica were caused by the same volcanic disturbance and that its epicenter was located at the earth s equatorial zone which enabled global distribution of the acid gases these results indicate that inter hemispheric dating of ice sheets is possible by the chemical identification of major eruptive volcanic events in the equatorial zone

implications of pore microgeometry heterogeneity for the movement and chemical reactivity of co2 in carbonates abstractwe studied the heterogeneity of natural rocks with respect to their pore size distribution obtained from mercury intrusion capillary pressure micp tests at a scale about one fifth of the standard plug size 2 5 cm we investigated two fontainebleau sandstone and two limestone samples we found that at the scale of the micp tests heterogeneities are practically nonexistent still there are large differences in the capillary curves from one rock type to another also carbonate rocks unlike fontainebleau sandstone show heterogeneities at a scale smaller than the scale used in micp tests as seen by the complexity in the mercury saturation versus pressure curves we used this diversity between the capillary curves and this complexity within a single capillary curve to obtain information about the movement and chemical reactivity of co2 in carbonates the method consists of three steps first subdividing the carbonate pore system into microstructural facies each of them having a specific ra

the pinatubo eruption in south pole snow and its potential value to ice core paleovolcanic records snow samples collected in the 1996 austral summer at south pole show that sulfate concentrations in snow and by inference sulfur aerosol concentrations in the antarctic atmosphere were elevated from the end of 1991 to mid 1994 over a stable non volcanic background the new data support earlier findings that the june 1991 pinatubo eruption and the hudson eruption in the same year deposited volcanic sulfate and tephra in south pole snow and provide strong evidence of the global distribution of volcanic materials from the pinatubo eruption in this study snow samples were taken in six snow pits spatially distributed around the south pole station in order to evaluate the local spatial variability of volcanic signals due to glaciological variables such as snow accumulation rates and snow redistribution by wind after initial deposition the results indicate that pinatubo sulfate flux varies by as much as 20 throughout a 400 km2 area centered around the south pole station this glaciological variability probably represents the likely range of volcanic signals due to variations in snow deposition and post depositional changes the pinatubo eruption provides an unprecedented opportunity to estimate aerosol mass loadings by explosive volcanic eruptions found in antarctic ice cores via a quantitative relationship between aerosol mass loadings and sulfate flux in antarctic snow here the satellite estimated pinatubo so2 emission and the measured volcanic sulfate flux in snow with an assumed linearly quantitative relationship are used to calculate so2 loadings for several well known volcanic eruptions in the past 300 years covered by a shallow 42 m south pole firn core drilled in 1996 the errors for the calculated mass loadings are estimated by means of the glaciological variability associated with pinatubo volcanic flux

high precision dating and correlation of ice marine and terrestrial sequences spanning heinrich event 3 testing mechanisms of interhemispheric change using new zealand ancient kauri agathis australis robustly testing hypotheses of geographic synchroneity of abrupt and extreme change during the late pleistocene 60 000 to 11 650 years ago requires a level of chronological precision often lacking in ice marine and terrestrial sequences here we report a bidecadally resolved new zealand kauri agathis australis tree ring sequence spanning two millennia that preserves a record of atmospheric radiocarbon 14c during ice rafted debris event heinrich event 3 he3 in the north atlantic and antarctic isotope maximum 4 aim4 in the southern hemisphere using 14c in the marine cariaco basin and 10be preserved in greenland ice the kauri 14c sequence allows us to precisely align sequences across this period we observe no significant difference between atmospheric and marine 14c records during he3 suggesting no stratification of surface waters and collapse in atlantic meridional overturning circulation amoc instead our results support recent evidence for a weakened amoc across at least two millennia of the glacial period our work adds to a growing body of literature confirming that heinrich events are not the cause of stadial cooling and suggests changes in the amoc were not the primary driver of antiphase temperature trends between the hemispheres decadally resolved 14c in ancient kauri offers a powerful new and complementary approach to polar ice core ch4 alignment for testing hypotheses of abrupt and extreme climate change