a detailed 2840 year record of explosive volcanism in a shallow ice core from dome a east antarctica a detailed history of volcanism covering the last 2840 years is reconstructed from the top 100 42 m of a 109 91 m ice core from dome a da2005 ice core east antarctica using two known volcanic stratigraphic markers the mean accumulation rate during the period ad 1260 1964 is found to be 23 2 mm w e a 1 consistent with the previously reported accumulation rate at dome a this mean accumulation rate is used to date the entire core volcanic eruptions in the period 840 bc ad 1998 are detected as outstanding sulphate events seventy eight eruptions are identified with a mean of 2 7 eruptions per century comparisons with previous antarctic ice core volcanic records are made to assess the quality of this new da2005 record in terms of dates for volcanic events the da2005 record is in good agreement with previous records in the second millennium ad ad 1000 1998 a series of volcanic signatures found in both the da2005 record and several other antarctic ice core records in the first millennium ad ad 1 1000 appear to validate the da2005 record during this time period for the older periods direct comparisons are difficult between the da2005 record and other antarctic ice core records due to the lack of well dated stratigraphic horizons

proposed re dating of the european ice core chronology by seven years prior to the 7th century ad 1 progress in the study of past climate change requires integration of historical documentation tree ring data and ice core chemistry larsen et al 2008 re evaluate volcanic acid signals in the dye 3 grip and ngrip ice cores and identify large eruptions at 529 2 and 533 534 2 the latter claimed to cause the dry fog of 536 537 and environmental consequences to 550 this conflicts with previous suggestions of a two stage environmental event one in 536 the second c 540 understanding the full range of natural hazards requires critical evaluation of the happenings in the mid 6th century this paper will show that 4 spaced tree ring responses to extreme environmental conditions in the 6th century can be used to re locate 4 key ice acid dates moving the ice core chronology forward 7 years places two large volcanoes in 536 and 541 explaining the extended duration of the 536 550 effects and anchoring the ice chronology

bristlecone pine tree rings and volcanic eruptions over the last 5000 yr many years of low growth identified in a western usa regional chronology of upper forest border bristlecone pine pinus longaeva and pinus aristata over the last 5000 yr coincide with known large explosive volcanic eruptions and or ice core signals of past eruptions over the last millennium the agreement between the tree ring data and volcano ice core data is high years of ring width minima can be matched with known volcanic eruptions or ice core volcanic signals in 86 of cases in previous millennia while there is substantial concurrence the agreement decreases with increasing antiquity many of the bristlecone pine ring width minima occurred at the same time as ring width minima in high latitude trees from northwestern siberia and or northern finland over the past 4000 5000 yr suggesting climatically effective events of at least hemispheric scale in contrast with the ice core records the agreement between widely separated tree ring records does not decrease with increasing antiquity these data suggest specific intervals when the climate system was or was not particularly sensitive enough to volcanic forcing to affect the trees and they augment the ice core record in a number of ways by providing confirmation from an alternative proxy record for volcanic signals by suggesting alternative dates for eruptions and by adding to the list of years when volcanic events of global significance were likely including the mid 2nd millennium bc eruption of thera

laboratory experiments on the formation of subaqueous depositional gullies by turbidity currents abstract gullies and furrows are shallow sub parallel features widespread on the seafloor and some lacustrine environments vast fields of linear channels of erosional origin called furrows with spacings of meters and up to hundred of meters are common in settings with relatively low seafloor slopes and have been previously ascribed to helical motion in benthic boundary layers submarine gullies are linear donwslope trending features of erosional depositional or mixed nature commonly observed in the upper continental slope submarine canyon walls and other relatively steep submarine environments while gully fields have been associated to the action of unconfined turbidity currents and other cascading dense flows their relatively large spacings ranging from several hundreds of meters to 1 2 km suggest that these features might be the result of other mechanisms different than boundary layer helical motion in this paper we propose an alternative mechanism for the initiation of gullies observed in relatively steep seabed gradients downslope of a seabed slope change such as those observed in continental margins self slope break or submarine canyon walls our working hypothesis is that gullies could be the result of a centrifugal instability that sets in interfaces of gravity currents as they flow through a bedslope transition since for these cases the centrifugal force excess is of the same order of magnitude of the driving force and therefore a potential source of flow instability we propose that gully spacing might be controlled by the magnitude of the centrifugal force scaling roughly with the radius of curvature of the transition slope break we also present experimental evidence on the formation of longitudinal features resembling slope gullies that were created in a laboratory tank after running successive supercritical depositional turbidity currents through a slope change similar to that observed in continental margins gullies in the tank developed through differential deposition only and showed spacing an order of magnitude larger that that expected from a boundary layer helical motion origin these experimental results along with the observation that gullies were not formed in the tank without a bed slope change low to high support the hypothesis of a centrifugal instability origin for longitudinal features in relatively steeper submarine settings our experimental results also support our first order approximate gully spacing rule which is in general agreement with field observations of gully spacing in upper continental slopes and submarine canyon walls

evidence of the eldgja iceland eruption in the gisp2 greenland ice core relationship to eruption processes and climatic conditions in the tenth century glaciochemical studies and the evaluation of tephra in the gisp2 ice core provide information on the characteristics and potential environmental and climatic effects of the mid to late ad 930s voluminous fissure eruption of eldgja iceland the similarity in the chemical composition of basaltic glass shards found in a section of core dated at ad 938 4 compared to proximal glass from the eldgja eruption verifies the presence of eldgja debris a dacitic glass present in the same layer probably originated from eldgja as well in which case eldgja was the primary contributor of sulphur rich aerosols to the atmosphere in the late ad 930s we cannot completely exclude the possibility that another explosive eruption in the ad 930s produced this dacitic glass estimated maximum stratospheric loading is 100 x 1012 g h 2so4 over a 3 6 year period following the eruption but loading could be as low as half of that value a search of historical and proxy records for the late ad 930s to early 940s fail to show a co

extreme temperature events in summer in northwest siberia since ad 742 inferred from tree rings abstract frost and light rings of living and dead individuals of siberian juniper juniperus sibirica burgsd and siberian larch larix sibirica ledeb growing at the upper polar ural mountains and polar yamal peninsula tree lines in northwest siberia have been studied to reconstruct summer frosts and abrupt temperature declines during the second half of the growing season over the past 1250 years the most severe temperature events in both regions were in ad 801 1109 1259 1278 1466 1601 and 1783 comparison of our data with data from other regions of the world shows that there is agreement in the timing of extreme temperature events in ad 800 801 1109 1258 1259 1453 1466 1585 1601 1783 1884 1912 and 1992 between several regions most probably these extremes have been caused by climatically effective explosive volcanic eruptions

mortality in england during the 1783 4 laki craters eruption 1783 4 has been recognised as a mortality crisis year in the population history of england this demographic incident coincides with the laki craters eruption iceland which began in june 1783 and fumigated many parts of europe with volcanic gases and particles many reports and proxy climate records implicate the volcanic cloud in meteorological anomalies including notably hot 1783 summer conditions in england and a severe subsequent winter we present here a detailed analysis of the geographical and temporal trends in english mortality data and interpret them in the light of the climatological records and observations of the pollutant cloud we show that there were two distinct crisis periods in august september 1783 and january february 1784 which together accounted for 20 000 extra deaths in both cases the east of england was the worst affected region possible causes for the two crisis periods are considered and we conclude that the timing and magnitude of the winter mortality peak can be explained by the severe cold of january 1784 the late summer mortality followed 1 2 months after the very hot july of 1783 and may also have been related to the weather with the time lag reflecting the relatively slow spread of enteric disease or the contraction of malaria however it is hard to explain the entire late summer anomaly by these high temperature causes we therefore consider that fine acid aerosol and or gases in the volcanic haze may also have contributed to the unusual august september mortality given that complex radiative and dynamical effects of the volcanic cloud are implicated in the climatic anomalies in 1783 4 it is likely that the laki craters eruption did play a role in the english mortality crises of the same period

major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

spatio temporal variability in volcanic sulphate deposition over the past 2 kyr in snow pits and firn cores from amundsenisen antarctica in the framework of the european project for ice coring in antarctica epica a comprehensive glaciological pre site survey has been carried out on amund senisen dronning maud land east antarctica in the past decade within this survey four intermediate depth ice cores and 13 snow pits were analyzed for their ionic compos ition and interpreted with respect to the spatial and temporal variability of volcanic sul phate deposition the comparison of the non sea salt nss sulphate peaks that are related to the well known eruptions of pinatubo and cerro hudson in ad1991 revealed sulphate depositions of comparable size 15 8 3 4 kg km 2 in 11 snow pits there is a tendency to higher annual concentrations for smaller snow accumulation rates the combination of seasonal sodium and annually resolved nss sulphate records allowed the establishment of a time scale derived by annual layer counting over the last 2000 years and thus a detailed chronology of annual volcanic sulphate deposition using a robust outlier detection algo rithm 49 volcanic eruptions were identified between ad165 and 1997 the dating uncer tainty is 3 years between ad1997 and 1601 around 5 years between ad1601 and 1257 and increasing to 24 years at ad165 improving the accuracy of the volcanic chronology during the penultimate millennium considerably abstract in the framework of the european project for ice coring in antarctica epica a comprehensive glaciological pre site survey has been carried out on amund senisen dronning maud land east antarctica in the past decade within this survey four intermediate depth ice cores and 13 snow pits were analyzed for their ionic compos ition and interpreted with respect to the spatial and temporal variability of volcanic sul phate deposition the comparison of the non sea salt nss sulphate peaks that are related to the well known eruptions of pinatubo and cerro hudson in ad1991 revealed sulphate depositions of comparable size 15 8 3 4 kg km 2 in 11 snow pits there is a tendency to higher annual concentrations for smaller snow accumulation rates the combination of seasonal sodium and annually resolved nss sulphate records allowed the establishment of a time scale derived by annual layer counting over the last 2000 years and thus a detailed chronology of annual volcanic sulphate deposition using a robust outlier detection algo rithm 49 volcanic eruptions were identified between ad165 and 1997 the dating uncer tainty is 3 years between ad1997 and 1601 around 5 years between ad1601 and 1257 and increasing to 24 years at ad165 improving the accuracy of the volcanic chronology during the penultimate millennium considerably

ash from changbaishan millennium eruption recorded in greenland ice implications for determining the eruption s timing and impact major volcanic eruptions can impact on global climate by injecting large quantities of aerosols and ash into the atmosphere that alter the radiative balance and chemical equilibrium of the stratosphere the millennium eruption of tianchi paektu china north korea was one of the largest late holocene eruptions uncertainty about the precise timing of the eruption has hindered the recognition of its climate impact in palaeoclimate and historical records here we report the compelling identification of the eruption s volcanic signal in greenland ice cores through the association of geochemically characterized volcanic glass represented in by bimodal populations that compare with proximal material from the source eruption the eruption most probably occurred in the a d 940s 7 years after the eldgja eruption on iceland we examine the eruption s potential for climate forcing using the sulfate records from the ice cores and conclude that it was unlikely to have had a global or extraregional impact

snow anomaly events from historical documents in eastern china during the past two millennia and implication for low frequency variability of ao nao and pdo 1 models and instrumental data indicate that the spatial and temporal variations of snow cover are significantly related to atmospheric circulation e g the ao nao here we present historical snow anomaly events during the past two millennia that provide a unique temporal window to studying long term ao nao a prominent phenomenon in wintertime direct descriptions such as no snow during the winter and pray god for snow are interpreted as convincing evidence for snow anomalies the variations of positive negative snow abnormal events show clear decadal to century variations during the past two millennia based on the previous instrumental research and comparison with other reconstruction data we suggest the index of abnormal snow ias may be an ao like atmospheric variability the winter during the medieval warm period mwp ad 900 1300 might be strongly influenced by a predominantly positive ao with less snow condition whereas the little ice age lia ad 1300 1900 by negative ao concomitant with heavier snowfalls in east asia our data show that a warm climate period the mwp a cold period the lia can be perturbed by a cold spell a warm spell which are linked with a change in atmospheric circulation low frequency variability of snow records may be intrinsic to the natural climate system although the dynamic mechanisms linking snow anomalies with atmospheric circulation the ao nao the pdo is unclear on the decadal to century time scales pacific ocean may play an important role in regulating atmospheric circulations since the ias is highly correlated with the reconstruction of pdo

new ice core evidence for a volcanic cause of the a d 536 dust veil in new zealand human cryptosporidiosis demonstrates spring and autumn peaks of incidence with the spring peak being three times greater in magnitude than the autumn peak the imbalance between the two peaks is notable and may be associated with the high livestock density in new zealand in the summer and autumn the cryptosporidiosis rate was positively associated with temperatures in the current and previous month highlighting the importance of outdoor recreation to transmission no associations between spring incidence and weather were found providing little support for the importance of drinking water pathways imported travel cases do not appear to be an important factor in the aetiology of cryptosporidiosis in new zealand

climate response to large high latitude and low latitude volcanic eruptions in the community climate system model 1 explosive volcanism is known to be a leading natural cause of climate change the second half of the 13th century was likely the most volcanically perturbed half century of the last 2000 years although none of the major 13th century eruptions have been clearly attributed to specific volcanoes this period was in general a time of transition from the relatively warm medieval period to the colder little ice age but available proxy records are insufficient on their own to clearly assess whether this transition is associated with volcanism this context motivates our investigation of the climate system sensitivity to high and low latitude volcanism using the fully coupled ncar community climate system model ccsm3 we evaluate two sets of ensemble simulations each containing four volcanic pulses with the first set representing them as a sequence of tropical eruptions and the second representing eruptions occurring in the mid high latitudes of both the northern and southern hemispheres the short term direct radiative impacts of tropical and high latitude eruptions include significant cooling over the continents in summer and cooling over regions of increased sea ice concentration in northern hemisphere nh winter a main dynamical impact of moderate tropical eruptions is a winter warming pattern across northern eurasia furthermore both ensembles show significant reductions in global precipitation especially in the summer monsoon regions the most important long term impact is the cooling of the high latitude nh produced by multiple tropical eruptions suggesting that positive feedbacks associated with ice and snow cover could lead to long term climate cooling in the arctic

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 effect of explosive tropical volcanism on enso thisstudyexaminestheresponseofelnino southernoscillation enso tomassivevolcaniceruptionsin a suite of coupled general circulation model cgcm simulations utilizing the community climate system model version 3 ccsm3 the authors find that the radiative forcing due to volcanic aerosols injected into the stratosphere induces a model climatic response that projects onto the enso mode and initially creates a la nina event that peaks around the time the volcanic forcing peaks the curl of the wind stress changes accompanying this volcanically forced equatorial region cooling acts to recharge the equatorial region heat for weaker volcanic eruptions this recharging results in an el nino event about two seasons after the peak of the volcanic forcing the results of the ccsm3 volcanic forcing experiments lead the authors to propose that the initial tropical pacific ocean response to volcanic forcing is determined by four different mechanisms one process is the dynamical thermostat mechanism the mean upwelling of anomalous temperature and the other processes are related to the zonal equatorial gradients of the mean cloud albedo newtonian cooling and mixed layer depth the zonal gradient in ccsm3 set by both mixed layer depth and newtonian cooling terms oppose the zonal sea surface temperature anomaly ssta gradient produced by the dy namical thermostat and initially dominate the mixed layer zonal equatorial heat budget response applying this knowledge to a simple volcanically forced mixed layer equation using observed estimates of the spa tially varying variables the authors again find that the mixed layer depth and newtonian cooling terms oppose and dominate the zonal ssta gradient produced by the dynamical thermostat this implies that the observed initial response to volcanic forcing should be la nina like not el nino as suggested by paleo climate records

volcanic forcing of climate over the past 1500 years an improved ice core based index for climate models 1 understanding natural causes of climate change is vital to evaluate the relative impacts of human pollution and land surface modification on climate we have investigated one of the most important natural causes of climate change volcanic eruptions by using 54 ice core records from both the arctic and antarctica our recently collected suite of ice core data more than double the number of cores ever used before reduces errors inherent in reconstructions based on a single or small number of cores which enables us to obtain much higher accuracy in both detection of events and quantification of the radiative effects we extracted volcanic deposition signals from each ice core record by applying a high pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation we then studied the spatial pattern of volcanic sulfate deposition on greenland and antarctica and combined this knowledge with a new understanding of stratospheric transport of volcanic aerosols to produce a forcing data set as a function of month latitude and altitude for the past 1500 years we estimated the uncertainties associated with the choice of volcanic signal extraction criteria ice core sulfate deposition to stratospheric loading calibration factor and the season for the eruptions without a recorded month we forced an energy balance climate model with this new volcanic forcing data set together with solar and anthropogenic forcing to simulate the large scale temperature response the results agree well with instrumental observations for the past 150 years and with proxy records for the entire period through better characterization of the natural causes of climate change this new data set will lead to improved prediction of anthropogenic impacts on climate the new data set of stratospheric sulfate injections from volcanic eruptions for the past 1500 years as a function of latitude altitude and month is available for download in a format suitable for forcing general circulation models of the climate system

dendrochemical analysis of a tree ring growth anomaly associated with the late bronze age eruption of thera the most marked tree ring growth anomaly in the aegean dendrochronological record over the last 9000 years occurs in the mid 17th century bc and has been speculatively correlated with the impact of the late bronze age eruption of thera santorini if such a connection could be proved it would be of major interdisciplinary significance it would open up the possibility of a precise date for a key archaeological geological and environmental marker horizon and offer a direct tie between tree ring and ice core records some 3600 years ago a volcanic explanation for the anomaly is highly plausible yet in the absence of a scientifically proven causal connection the value of the proposed correlation is limited in order to test the hypothesis dendrochemical analysis via synchrotron radiation scanning x ray fluorescence microscopy sxfm inductively coupled plasma atomic emission spectroscopy icp aes and inductively coupled plasma mass spectroscopy icp ms was carried out on growth ring series from four trees displaying the anomaly increases of sulfur calcium and rare earth elements following the onset of altered growth plus concentration spikes of zinc and hafnium in the first affected growth ring provide promising new evidence in support of a volcanic causal factor although a volcanic association is implied the new data are not sufficient to prove a link to the exact eruption source

mystery cloud of ad 536 dry fogs appear in the atmosphere when large volcanic eruptions inject massive quantities of fine silicate ash and aerosol forming sulphur gases into the troposphere and stratosphere although the ash gravitationally settles out within weeks the aerosols spread around the globe and can remain suspended in the stratosphere for years because solar radiation is easily absorbed and backscattered by the volcanic particles a haziness in the sky and a dimming of the sun and moon are produced very dense and widespread dry fogs occur on the average once every few centuries1 3 the sizes and intensities of some of the largest of them before the modern scientific era have been estimated by several indirect methods2 4 5 the densest and most persistent dry fog on record was observed in europe and the middle east during ad 536 and 537 despite the earliness of the date there is sufficient detailed information to estimate the optical depth and mass of this remarkable stratospheric dust cloud the importance of this cloud resides in the fact that its mass and its climatic consequences appear to exceed those of any other volcanic cloud observed during the past three millenia although the volcano responsible remains a mystery a tropical location perhaps the volcano rabaul on the island of new britain papua new guinea can be tentatively inferred

south pole ice core record of explosive volcanic eruptions in the first and second millennia a d and evidence of a large eruption in the tropics around 535 a d 1 a record of explosive eruptions over the last 1830 years reconstructed from a south pole antarctica ice core extends the coverage of volcanic history to the start of the first millennium a d the ice core dating by annual layer counting carries an uncertainty of 2 of the number of years from time markers with the largest dating error of 20 years at the bottom of the 182 m core several aspects of the methodology of detecting and quantifying volcanic sulfate signals in ice cores are examined in developing this record the new record is remarkably consistent with previous south pole records a comparison with records from several antarctica locations suggests that the south pole location is among the best for ice core reconstruction of volcanic records owing to the excellent preservation of volcanic signals at the south pole the relatively low and uniform sulfate background and the moderately high snow accumulation rates which allow for dating by annual layer counting a prominent volcanic event dated at 531 15 a d along with evidence from other records indicates that an unusually large eruption took place in the tropics and was probably responsible for the mystery cloud climate episode of 536 537 a d the date of 536 is suggested for a prominent volcanic signal that appears in the first half of the sixth century a d in ice cores which can in turn be used as a time stratigraphic marker in dating ice cores by annual layer counting or by computing average accumulation rates or layer thicknesses with such markers

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

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

centennial scale climate change from decadally paced explosive volcanism a coupled sea ice ocean mechanism northern hemisphere summer cooling through the holocene is largely driven by the steady decrease in summer insolation tied to the precession of the equinoxes however centennial scale climate departures such as the little ice age must be caused by other forcings most likely explosive volcanism and changes in solar irradiance stratospheric volcanic aerosols have the stronger forcing but their short residence time likely precludes a lasting climate impact from a single eruption decadally paced explosive volcanism may produce a greater climate impact because the long response time of ocean surface waters allows for a cumulative decrease in sea surface temperatures that exceeds that of any single eruption here we use a global climate model to evaluate the potential long term climate impacts from four decadally paced large tropical eruptions direct forcing results in a rapid expansion of arctic ocean sea ice that persists throughout the eruption period the expanded sea ice increases the flux of sea ice exported to the northern north atlantic long enough that it reduces the convective warming of surface waters in the subpolar north atlantic in two of our four simulations the cooler surface waters being advected into the arctic ocean reduced the rate of basal sea ice melt in the atlantic sector of the arctic ocean allowing sea ice to remain in an expanded state for 100 model years after volcanic aerosols were removed from the stratosphere in these simulations the coupled sea ice ocean mechanism maintains the strong positive feedbacks of an expanded arctic ocean sea ice cover allowing the initial cooling related to the direct effect of volcanic aerosols to be perpetuated potentially resulting in a centennial scale or longer change of state in arctic climate the fact that the sea ice ocean mechanism was not established in two of our four simulations suggests that a long term sea ice response to volcanic forcing is sensitive to the stability of the seawater column wind and ocean currents in the north atlantic during the eruptions

bi decadal variability excited in the coupled ocean atmosphere system by strong tropical volcanic eruptions decadal and bi decadal climate responses to tropical strong volcanic eruptions sves are inspected in an ensemble simulation covering the last millennium based on the max planck institute earth system model an unprecedentedly large collection of pre industrial sves up to 45 producing a peak annual average top of atmosphere radiative perturbation larger than 1 5 wm 2 is investigated by composite analysis post eruption oceanic and atmospheric anomalies coherently describe a fluctuation in the coupled ocean atmosphere system with an average length of 20 25 years the study provides a new physically consistent theoretical framework to interpret decadal northern hemisphere nh regional winter climates variability during the last millennium the fluctuation particularly involves interactions between the atlantic meridional overturning circulation and the north atlantic gyre circulation closely linked to the state of the winter north atlantic oscillation it is characterized by major distinctive details among them the most prominent are a a strong signal amplification in the arctic region which allows for a sustained strengthened teleconnection between the north pacific and the north atlantic during the first post eruption decade and which entails important implications from oceanic heat transport and from post eruption sea ice dynamics and b an anomalous surface winter warming emerging over the scandinavian western russian region around 10 12 years after a major eruption the simulated long term climate response to sves depends to some extent on background conditions consequently ensemble simulations spanning different phases of background multidecadal and longer climate variability are necessary to constrain the range of possible post eruption decadal evolution of nh regional winter climates

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

effects of large volcanic eruptions on global summer climate and east asian monsoon changes during the last millennium analysis of mpi esm simulations abstractresponses of summer june august jja temperature and precipitation to large volcanic eruptions are analyzed using the millennial simulations of the earth system model developed at the max planck institute for meteorology the model was driven by up to date reconstructions of external forcing including natural forcing solar and volcanic and anthropogenic forcing land cover change and greenhouse gases cooling anomalies after large volcanic eruptions are seen on a nearly global scale the cooling in the northern hemisphere nh is stronger than in the southern hemisphere sh and cooling is stronger over the continents than over the oceans the precipitation decreases in the tropical and subtropical regions in the first summer after large volcanic eruptions the cooling with amplitudes of up to 0 6 c is also seen over eastern china east asia is dominated by northerly wind anomalies and the corresponding summer rainfall exhibits a coherent reduction over the entirety of eastern china t

the greenland ice sheet project 2 depth age scale methods and results the greenland ice sheet project 2 gisp2 depth age scale is presented based on a multiparameter continuous count approach to a depth of 2800 m using a systematic combination of parameters that have never been used to this extent before the ice at 2800 m is dated at 110 000 years b p with an estimated error ranging from 1 to 10 in the top 2500 m of the core and averaging 20 between 2500 and 2800 m parameters used to date the core include visual stratigraphy oxygen isotopic ratios of the ice electrical conductivity measurements laser light scattering from dust volcanic signals and major ion chemistry gisp2 ages for major climatic events agree with independent ages based on varve chronologies calibrated radiocarbon dates and other techniques within the combined uncertainties good agreement also is obtained with greenland ice core project ice core dates and with the specmap marine timescale after correlation through the 18 o of o 2 although the core is deformed below 2800 m and the continuity of the record is unclear we attempted to date this section of the core on the basis of the laser light scattering of dust in the ice

a continuous multimillennial ring width chronology in yamal northwestern siberia remains of subfossil siberian larch trees in the holocene deposits of the yamal peninsula western siberia have been collected in order to develop a continuous multimillennium tree ring width chronology this work has produced a calendar age dated 4000 year 2000 bc to ad 1996 series from these data summer temperature variability in this region has been estimated on annual to multidecadal timescales radiocarbon dating of selected older material shows that the oldest subfossil wood is 9400 years old and the dates of the sampled material are generally distributed evenly through time it will therefore be possible to develop a tree ring chronology for more than nine millennia an initial assessment of long term e uctuations in yamal summer warmth has been realized through the reconstruction of tree line dynamics using a combination of dendrochron ological absolute dated material and less precisely radiocarbon dated older subfossils

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

a 12 000 year record of explosive volcanism in the siple dome ice core west antarctica 1 air mass trajectories in the southern hemisphere provide a mechanism for transport to and deposition of volcanic products on the antarctic ice sheet from local volcanoes and from tropical and subtropical volcanic centers this study extends the detailed record of antarctic south american and equatorial volcanism over the last 12 000 years using continuous glaciochemical series developed from the siple dome a sdma ice core west antarctica the largest volcanic sulfate spike 280 g l occurs at 5881 b c e other large signals with unknown sources are observed around 325 b c e 270 g l and 2818 b c e 191 g l ages of several large equatorial or southern hemisphere volcanic eruptions are synchronous with many sulfate peaks detected in the sdma volcanic ice chemistry record the microprobe fingerprinting of glass shards in the sdma core points to the following antarctic volcanic centers as sources of tephra found in the sdma core balenny island pleiades mount berlin mount takahe and mount melbourne as well as mount hudson and possibly mount burney volcanoes of south america identified volcanic sources provide an insight into the poorly resolved transport history of volcanic products from source volcanoes to the west antarctic ice sheet

a synchronized dating of three greenland ice cores throughout the holocene as part of the effort to create the new greenland ice core chronology 2005 gicc05 a synchronized stratigraphical timescale for the holocene parts of the dye 3 grip and ngrip ice cores is made by using volcanic reference horizons in electri cal conductivity measurements to match the cores the main annual layer counting is carried out on the most suited records only exploit ing that the three ice cores have been drilled at locations with different climatic con ditions and differences in ice flow however supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the valid ity of the match after the verification the main dating is transferred to all records us ing the volcanic reference horizons as tie points an assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores the data used for the main annual layer counting of the past 7900 years are the dye 3 grip and ngrip stable isotope records as the high accumulation rate at the dye 3 drill site makes the seasonal cycle in the dye 3 stable isotopes very resistant to firn diffusion an effort has been made to extend the dye 3 holocene record the new syn chronized dating relies heavily on this record of 75 000 stable isotope samples the dat ing of the early holocene consists of an already established part of gicc05 for grip and ngrip which has now been transferred to the dye 3 core gicc05 dates the younger dryas termination as defined from deuterium excess to 11 703 b2k 130 years earlier than the previous grip dating

reconciling multiple ice core volcanic histories the potential of tree ring and documentary evidence 670 730 ce chronologically secure volcanic event histories are important for improving our understanding of volcano climate responses and securing ice core chronologies we present an exploratory case study that attempts to reconcile the chemical fingerprints of major volcanism in greenland ice cores for the years 670 730 ce this period experienced considerable volcanic perturbation with multiple volcanic signals registered in all 8 greenland ice core datasets studied including some comparable in magnitude to the great 1815 tambora eruption but reconciling signals with divergent dating between datasets presents a number of challenges to further our understanding of the volcanic history of this period frost rings tree ring growth width and density minima from europe siberia and china are considered together with western european near eastern and chinese documentary evidence these reveal a striking sequence of co occurring inter regional climatic extremes and social crises we further examine a recently proposed 7 year adjustment to the gicc05 chronology used by many greenland ice cores and find that this results in a more coherent volcanic history for these years and an improved agreement with tree ring and written records three major volcanic events can now be identified dated to 681 684 686 and 706 707 with several moderate events further contributing to a sustained climate perturbation reflected in prolonged temperature reductions in high resolution reconstructions

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

climatic response to high latitude volcanic eruptions 1 strong volcanic eruptions can inject large amounts of so2 into the lower stratosphere which over time are converted into sulfate aerosols and have the potential to impact climate aerosols from tropical volcanic eruptions like the 1991 mount pinatubo eruption spread over the entire globe whereas high latitude eruptions typically have aerosols which remain in the hemisphere in which they where injected this causes their largest radiative forcing to be extratropical and the climate response should be different from that of tropical eruptions we conducted a 20 member ensemble simulation of the climate response to the katmai eruption 58 n of 6 june 1912 using the nasa goddard institute for space studies modele climate model we also produced an additional 20 member ensemble for a 3 times katmai 3x katmai eruption to see the impact the strength of the eruption has on the radiative as well as the dynamical responses the results of these simulations do not show a positive arctic oscillation response like past simulations of tropical volcanic eruptions but we did find significant cooling over southern asia during the boreal winter the first winter following katmai and the second winter following 3x katmai showed strong similarities in lower stratospheric geopotential height anomalies and sea level pressure anomalies which occurred when the two cases had similar optical depth perturbations these simulations show that the radiative impact of a high latitude volcanic eruption was much larger than the dynamical impact at high latitudes in the boreal summer however strong cooling over the northern hemisphere landmasses caused a decrease in the asian monsoon circulation with significant decreases of up to 10 in cloud cover and warming over northern india thus the main dynamical impact of high latitude eruptions is in the summer over asia

abrupt onset of the little ice age triggered by volcanism and sustained by sea ice ocean feedbacks 1 northern hemisphere summer temperatures over the past 8000 years have been paced by the slow decrease in summer insolation resulting from the precession of the equinoxes however the causes of superposed century scale cold summer anomalies of which the little ice age lia is the most extreme remain debated largely because the natural forcings are either weak or in the case of volcanism short lived here we present precisely dated records of ice cap growth from arctic canada and iceland showing that lia summer cold and ice growth began abruptly between 1275 and 1300 ad followed by a substantial intensification 1430 1455 ad intervals of sudden ice growth coincide with two of the most volcanically perturbed half centuries of the past millennium a transient climate model simulation shows that explosive volcanism produces abrupt summer cooling at these times and that cold summers can be maintained by sea ice ocean feedbacks long after volcanic aerosols are removed our results suggest that the onset of the lia can be linked to an unusual 50 year long episode with four large sulfur rich explosive eruptions each with global sulfate loading 60 tg the persistence of cold summers is best explained by consequent sea ice ocean feedbacks during a hemispheric summer insolation minimum large changes in solar irradiance are not required

a new bipolar ice core record of volcanism from wais divide and neem and implications for climate forcing of the last 2000 years volcanism is a natural climate forcing causing short term variations in temperatures histories of volcanic eruptions are needed to quantify their role in climate variability and assess human impacts we present two new seasonally resolved annually dated non sea salt sulfur records from polar ice cores wais divide wdc06a from west antarctica spanning 408 b c e to 2003 c e and neem neem 2011 s1 from greenland spanning 78 to 1997 c e both analyzed using high resolution continuous flow analysis coupled to two mass spectrometers the high dating accuracy allowed placing the large bi hemispheric deposition event ascribed to the eruption of kuwae in vanuatu previously thought to be 1452 1453 c e and used as a tie point in ice core dating into the year 1458 1459 c e this new age is consistent with an independent ice core timescale from law dome and explains an apparent delayed response in tree rings to this volcanic event a second volcanic event is detected in 1453 c e in both ice cores we show for the first time ice core signals in greenland and antarctica from the strong eruption of taupo in new zealand in 232 c e in total 133 volcanic events were extracted from wdc06a and 138 from neem 2011 s1 with 50 ice core signals predominantly from tropical source volcanoes identified simultaneously in both records we assess the effect of large bipolar events on temperature sensitive tree ring proxies these two new volcanic records synchronized with available ice core records to account for spatial variability in sulfate deposition provide a basis for improving existing time series of volcanic forcing

sr isotope evidence for a lacustrine origin for the upper miocene to pliocene bouse formation lower colorado river trough and implications for timing of colorado plateau uplift the upper miocene to pliocene bouse formation in the lower colorado river trough which consists largely of siltstone with basal tufa and marl has been interpreted as estuarine on the basis of paleontology this interpretation requires abrupt marine inundation that has been linked to early rifting in the gulf of california and salton trough new strontium isotope measurements reported here from carbonates and invertebrate shells in the bouse formation reveal no evidence of marine water but are consistent with deposition in a lake or chain of lakes fed by the colorado river furthermore the absence of a southward decrease in 87 sr 86 sr within the bouse formation does not support the estuarine model in which low 87 sr 86 sr marine sr would have dominated the mouth of the hypothetical bouse estuary elevation of originally marine 87 sr 86 sr in the bouse formation to its present level due to postdepositional interaction with ground water is unlikely because sr from secondary calcite above below and within the bouse formation is consistently less radiogenic not more than bouse marl and shells in contrast to bouse sr strontium from mollusks in tidal flat and delta front paleoenvironments in the contemporaneous imperial formation in the salton trough and from the subsurface south of yuma was derived from sea water and confirms the dominance of marine strontium near or at the mouth of the late miocene to early pliocene colorado river inferred post early pliocene uplift of the bouse formation from below sea level to modern elevations of up to 550 m has been used to support a late cenozoic uplift age for the nearby colorado plateau this constraint on uplift timing is eliminated if the bouse formation is lacustrine

the 1452 or 1453 a d kuwae eruption signal derived from multiple ice core records greatest volcanic sulfate event of the past 700 years 1 we combined 33 ice core records 13 from the northern hemisphere and 20 from the southern hemisphere to determine the timing and magnitude of the great kuwae eruption in the mid 15th century we extracted volcanic deposition signals by applying a high pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation by accounting for the dating uncertainties associated with each record these ice core records together reveal a large volcanogenic acid deposition event during 1453 1457 a d the results suggest only one major stratospheric injection from the kuwae eruption and confirm previous findings that the kuwae eruption took place in late 1452 or early 1453 which may serve as a reference to evaluate and improve the dating of ice core records the average total sulfate deposition from the kuwae eruption was 93 kg so4 km 2 in antarctica and 25 kg so4 km 2 in greenland the deposition in greenland was probably underestimated since it was the average value of only two northern greenland sites with very low accumulation rates after taking the spatial variation into consideration the average kuwae deposition in greenland was estimated to be 45 kg so4 km 2 by applying the same technique to the other major eruptions of the past 700 years our result suggests that the kuwae eruption was the largest stratospheric sulfate event of that period probably surpassing the total sulfate deposition of the tambora eruption of 1815 which produced 59 kg so4 km 2 in antarctica and 50 kg so4 km 2 in greenland