reply to comment by cole dai et al on climatic impact of the long lasting laki eruption inapplicability of mass independent sulfur isotope composition measurements here we respond to the comments by cole dai et al 2014 on our article schmidt et al 2012 specifically in response to section 2 of their reply we argued in schmidt et al 2012 that based on previously published estimates of the volatile release height during the 1783 1784 c e laki eruption the lack of a sulfur massindependent fractionation mif anomaly is expected in other words no previous study on laki ever argued that this eruption emitted so2 into altitudes 13 15 km in section 2 3 cole dai et al 2014 argue that the nonzero 33s value of their laki sample 1 may be explained by a short lived explosive phase at laki during which volatiles reached the stratosphere in schmidt et al 2012 in section 2 we argued in agreement with cole dai et al 2014 section 3 1 that for a mif anomaly to be preserved the laki volatiles would have had to be emitted in 20 km altitude our main point is that eruption column heights 20 km are unlikely based on the historical accounts and plume rise modeling for the laki eruption stothers et al 1986 woods 1993 thordarson and self 2003 in schmidt et al 2012 we argued that to deduce a short lived climatic impact of the laki eruption based on the lack of a mif anomaly and the length of the sulfate deposition in greenland ice cores may be misleading because the climatic impact will outlast the radiative forcing of the laki aerosol cloud cole dai et al 2014 acknowledge the latter in their reply in section 4 2 we agreewith cole dai et al 2014 in that themagnitude and length of the climatic impact during the winter of 1783 1784 depends on the altitude of the volatile release during the eruption sections 2 3 and 4 2 however even if we assumed that during laki all sulfur dioxide so2 would have been released in the troposphere then the aerosol cloud would still be present in the upper troposphere during march 1784 as is evident from independent model simulations of this tropospheric only scenario stevenson et al 2003 we acknowledge that there is uncertainty on the volatile release height for laki however it is worth considering that those climate model simulations that used an injection altitude between 9 km and 13 km for the laki so2 highwood and stevenson 2003 oman et al 2006a 2006b schmidt et al 2012 best match the observed temperature changes during summer of 1783 angell and korshover 1985 brzdil et al 2010 briffa et al 1998 d arrigo and jacoby 1999 jacoby et al 1999 kington 1988 manley 1974 parker et al 1992 thordarson and self 2003 based on these model simulations a climatic impact during the winter of 1783 1784 albeit weaker than during the climactic phases of laki is expected and our argument here does not exclude the role of natural variability in contributing to the cold winter of 1783 1784 as discussed in schmidt et al 2012 therefore we continue to argue that for high latitude eruptions such as laki the applicability of sulfur isotopic measurements to interpret the climatic relevance has yet to be demonstrated itmay transpire that the interpretation of mif signals for the climate relevance of an eruption is valid and unambiguous only for short lived explosive eruptions in the tropics in terms of the processes producing a mif anomaly section 3 3 in cole dai et al 2014 the works by hattori et al 2013 and ono et al 2013 suggest that there are remaining issues not discussed by cole dai et al 2014 for instance self shielding of so2 due to high column densities typical for eruptions of pinatubo scale and greater and the preservation of the mif signature in general

volcanic aerosol perturbations and strong el nino events no general correlation we test the hypothesis that el nino southern oscillation enso events are caused or enhanced by volcanic aerosol perturbations using two methods 1 a case by case comparison of the 16 strongest el nino events of the last 150 years with the characteristics of the largest concurrent volcanic events and 2 comparison of the timing of strong el nino events and the independently determined record of stratospheric optical depth perturbations many eruptions that occurred near times of strong el nino years produced small amounts of stratospheric aerosols in many cases the relative timing of the two events argues against triggering the correlation of 4 of 11 peaks in global stratospheric optical depth 0 025 within 3 years of strong el nino events over the last 150 years is what would be expected by chance moreover five strong el ninos occurred between 1915 and 1960 when the stratosphere was largely free of volcanic aerosols of the three strongest tropical volcanic aerosol perturbations that coincided with or were followed by strong el ninos in the period studied krakatau in 1883 el chichon in 1982 and pinatubo in 1991 the two modern ones occurred after the earliest sst warming of the el nino events the coincidence of these two phenomena indicates no causative relationship

simulation and observations of stratospheric aerosols from the 2009 sarychev volcanic eruption 1 we used a general circulation model of earth s climate to conduct simulations of the 12 16 june 2009 eruption of sarychev volcano 48 1 n 153 2 e the model simulates the formation and transport of the stratospheric sulfate aerosol cloud from the eruption and the resulting climate response we compared optical depth results from these simulations with limb scatter measurements from the optical spectrograph and infrared imaging system osiris in situ measurements from balloon borne instruments lofted from laramie wyoming 41 3 n 105 7 w and five lidar stations located throughout the northern hemisphere the aerosol cloud covered most of the northern hemisphere extending slightly into the tropics with peak backscatter measured between 12 and 16 km in altitude aerosol concentrations returned to near background levels by spring 2010 after accounting for expected sources of discrepancy between each of the data sources the magnitudes and spatial distributions of aerosol optical depth due to the eruption largely agree in conducting the simulations we likely overestimated both particle size and the amount of so2 injected into the stratosphere resulting in modeled optical depth values that were a factor of 2 4 too high modeled optical depth due to the eruption shows a peak too late in high latitudes and too early in low latitudes suggesting a problem with stratospheric circulation in the model the model also shows a higher decay rate in optical depth than is observed showing an inaccuracy in stratospheric removal rates in some seasons the modeled removal rate of sulfate aerosols from the sarychev eruption is higher than the rate calculated for aerosols from the 1991 eruption of mt pinatubo

sage ii measurements of early pinatubo aerosols sage ii satellite measurements of the mt pinatubo eruption cloud in the stratosphere during june july and early august 1991 show that aerosols in the tropics reached as high as 29 km altitude with most of the cloud between 20 and 25 km the most optically thick portions of the cloud covered latitudes from 10 s to 30 n during the early part of this period by late july high stratospheric optical depths were observed to at least 70 n with the high values north of about 30 n from layers below 20 km high pressure systems in both hemispheres were observed to be correlated with the movement of volcanic material at 21 km into the westerly jet stream at high southern latitudes and similarly to high northern latitudes at 16 km by august the entire southern hemisphere had experienced a 10 fold increase in optical depth relative to early july due to layers above 20 km initial mass calculations using sage ii data place the aerosol produced from this eruption at 20 to 30 megatonnes well above the 12 megatonnes produced by el chichon

a 220 year continuous record of volcanic h2so4 in the antarctic ice sheet continuous h2so4 profiles observed in snow from several antarctic locations reveal four major volcanic events of the past two centuries agung krakatoa tambora and another large scale event not recorded historically acid deposition and interhemispheric distribution mechanisms are quantified and then used to obtain an order of magnitude estimate for the h2so4 emissions from these eruptions

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

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

estimation of the size distribution of pinatubo volcanic dust from bishop s ring simulations since the middle of july 1991 approximately one month after the explosive eruptions of mt pinatubo in the philippines bishop s ring phenomena were occasionally observed over japan under favorable conditions of clear skies on the basis of the single scattering approximation the chromaticity of bishop s rings was simulated it was found that bishop s rings are observable only when a sufficient amount of aerosols exist that have an unusually narrow mono modal size distribution and a mode radius between 0 57 m and 0 63 m with an effective variance of less than 0 05

stratospheric sulfate from el chichon and the mystery volcano stratospheric sulfate was collected by high altitude aircraft and balloons to assess the impacts of el chichon and an unidentified volcano on the stratosphere the mystery volcano placed about 0 85 tg of sulfate in the northern hemisphere stratosphere el chichon injected about 7 6 tg sulfate into the global stratosphere

a latitudinally dependent volcanic dust veil index and its effect on climate simulations abstract a latitudinally dependent annual average volcanic dust veil index is developed based on indices of lamb and mitchell this index is then used to force a climate model to determine if an improved volcanic index could improve the correlations previously found when forcing the model with hemispherically averaged dust it does not this suggests that natural variability may also be an important cause of climate change during the past 400 years

major optical depth perturbations to the stratosphere from volcanic eruptions pyrheliometric period 1881 1960 a detailed chronology of major stratospheric dust veils from 1881 to 1960 has been constructed by searching the primary literature for relevant observational data of various kinds especially pyrheliometry data from 23 observing sites in both hemispheres have been reduced in a rigorous fashion to yield a table of pyrheliometric optical depth perturbations as a function of year month and latitude band to convert to visual reference wavelengths the tabular entries should be multiplied by a time dependent factor that is somewhat greater than unity ten measurable volcanic dust veils have been established in this manner and have been analyzed as to their generation transport decay and total mass these clouds arose from eruptions of krakatau 1883 an unidentified volcano 1890 soufriere and pelee 1902 santa maria 1902 ksudach 1907 katmai 1912 puyehue 1921 paluweh 1928 komagatake 1929 and quizapu 1932 other turbidity indicators have also been used in the analysis including starlight extinction purple twilight glows color of sun and moon polarization of blue sky light bishop s ring around the sun and dark lunar eclipses global stratospheric aerosol loadings have been computed from the peak turbidities agreement with the aerosol masses derived from polar ice cores is good in the important cases of krakatau santa maria and after a major correction of the ice core value katmai during the long period 1881 1992 about 80 of all stratospheric aerosols generated by the largest sulfur producing eruptions were emplaced during the two short time intervals 1883 1902 and 1982 1991 the long term 1881 1992 average annual production rate of stratospheric so2 from the largest eruptions was 0 8 tg yr 1 about half the average rate since 1981 implications of the principal results are discussed

atmospheric aerosol loading and transport due to the 1783 84 laki eruption in iceland interpreted from ash particles and acidity in the gisp2 ice core abstract glass shards from the a d 1783 laki fissure eruption in iceland have been identified in the gisp2 ice core from summit greenland at a level just preceding the major acidity sulfate peak detailed reconstruction of ice stratigraphy coupled with analyses of solid particles from filtered samples indicate that a small amount of laki ash was carried via atmospheric transport to greenland in the summer of 1783 whereas the main aerosol precipitation occurred in the summer and early fall of 1784 sulfate concentrations in the ice increase slightly during late summer and fall of 1783 and remain steady throughout the winter due to slow oxidation rates during this season in the arctic the sulfate concentration rises dramatically in the spring and summer of 1784 producing a massive sulfate peak previously believed to have accumulated during the summer of 1783 and commonly used as the marker horizon in greenland ice core studies the chronology of ash and acid fallout at the gisp2 site suggests that a significant portion of the laid eruption plume penetrated the tropopause and that aerosol generated from it remained aloft for at least 1 yr after the eruption based on comparisons with other glaciochemical seasonal indicators abnormally cool conditions prevailed at summit during the summer of 1784 this further supports the claim that a significant volume of sulfate aerosol remained in the arctic middle atmosphere well after the eruption had ceased

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

runoff induced sediment yield over dune slopes in the negev desert 1 quantity and variability although extensive data exist on runoff erosion and rates for non sandy hillslopes data for arid dune slopes are scarce owing to the widespread perception that the high infiltrability of sand will reduce runoff however runoff is generated on sandy dunes in the hallamish dune field western negev desert israel p 95 mm due to the presence of a thin usually 1 3 mm microbiotic crust the runoff in turn produces erosion sediment yield was measured on ten plots 140 1640 m2 on the north and south facing slopes of longitudinal dunes two plots facing north and two facing south were subdivided into three subplots the subplots represented the crest of the active dune devoid of crust the extensively crusted footslope of the dune and the midslope section characterized by a patchy crust the remaining plots extended the full length of the dune slope no runoff and consequently no water eroded sediments were obtained from the crest subplots devoid of crust however runoff and sediment were obtained from the mid and footslope crusted subplots sediment yield from the footslope subplots was much higher than from the midslopes despite the higher sediment concentration that characterized the midslope subplots the mean annual sediment yield at the hallamish dune field was 432 g per metre width and was associated with high average annual concentrations of 32 g l 1 the data indicate that owing to the presence of a thin microbiotic crust runoff and water erosion may occur even within arid sandy dune fields copyright 2001 john wiley sons ltd

partial melting and the formation of granulite facies assemblages in namaqualand south africa abstract dehydration melting reactions in which water from a hydrous phase enters the melt leaving an anhydrous solid assemblage are the dominant mechanism of partial melting of high grade rocks in the absence of externally derived vapour equilibria involving melt and solid phases are effective buffers of ah2 o the element partitioning observed in natural rocks suggests that dehydration melting occurs over a temperature interval during which for most cases ah2o is driven to lower values the mass balance of dehydration melting in typical biotite gneiss and metapelite shows that the proportion of melt in the product assemblage at t 850 c is relatively small 10 20 and probably insufficient to mobilize a partially melted rock body granulite facies metapelite biotite gneiss and metabasic gneiss in namaqualand contain coarse grained discordant unfoliated anhydrous segregations surrounded by a finer grained foliated matrix that commonly includes hydrous minerals the segregations have modes consistent with the hypothesis that they are the solid and liquid products of the dehydration melting reactions bt sil qtz pi grt crd kfs l metapelite bt qtz pl opx kfs l biotite gneiss and hbl qtz opx cpx pl l metabasic gneiss the size shape distribution and modes of segregations suggest only limited migration and extraction of melt growth of anhydrous poikiloblasts in matrix regions development of anhydrous haloes around segregations and formation of dehydrated margins on metabasic layers enclosed in migmatitic metapelites all imply local gradients in water activity also they suggest that individual segregations and bodies of partially melted rock acted as sinks for soluble volatiles the preservation of anhydrous assemblages and the restricted distribution of late hydrous minerals suggest that retrograde reaction between hydrous melt and solids did not occur and that h2o in the melt was released as vapour on crystallization this model combined with the natural observations suggests that it is possible to form granulite facies assemblages without participation of external fluid and without major extraction of silicate melt

tarawera 1886 new zealand a basaltic plinian fissure eruption abstract new zealand s biggest and most destructive volcanic eruption of historical times was that of tarawera in 1886 the resulting scoria fall has a dispersal very similar in extent to that of the vesuvius a d 79 pumice fall and is one of the few known examples of a basaltic deposit of plinian type a new estimate of the volume 2 km 3 is significantly greater than previous estimates the basalt came mainly from a 7 km length of fissure and emission and exit velocity were fairly uniform along at least 4 km of it this is one of the few documented examples of a plinian eruption from a fissure vent primary welding of the scoria fall resulted where the accumulation rate exceeded about 250 mm min 1 a model of the eruption dynamics is proposed which leads to an estimate of 28 km for the height of the eruption cloud and implies a magma volatile fraction of 1 5 3 violent phreatic explosions occurred in the southwestern extension of the fissure across the rotomahana geothermal field and it is thought that some of the water responsible for the power of the plinian eruption came from this source though its amount was not sufficient to turn the eruption into a phreatoplinian one

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

volcanic eruptions and solar activity the historical record of large volcanic eruptions from 1500 to 1980 as contained in two recent eruption catalogs is subjected to detailed time series analysis two weak but probably statistically significant periodicities of 11 and 80 years are detected both cycles appear to correlate with well known cycles of solar activity the phasing is such that the frequency of volcanic eruptions increases decreases slightly around the times of solar minimum maximum the weak quasi biennial solar cycle is not obviously seen in the eruption data nor are the two slow lunar tidal cycles of 8 85 and 18 6 years time series analysis of the volcanogenic acidities in a deep ice core from greenland covering the years 553 1972 reveals several very long periods that range from 80 to 350 years and are similar to the very slow solar cycles previously detected in auroral and carbon 14 records mechanisms to explain the sun volcano link probably involve induced changes in the basic state of the atmosphere solar flares are believed to cause changes in atmospheric circulation patterns that abruptly alter the earth s spin the resulting jolt probably triggers small earthquakes which may temporarily relieve some of the stress in volcanic magma chambers thereby weakening postponing or even aborting imminent large eruptions in addition decreased atmospheric precipitation around the years of solar maximum may cause a relative deficit of phreatomagmatic eruptions at those times

the possible effects of large 19th and 20th century volcanic eruptions on zonal and hemispheric surface temperatures abstract the contribution of volcanic material to the stratosphere from major eruptions within the last two centuries has been estimated using volcanological criteria including eruption type eruption column height volume and duration of eruption and composition and degree of fragmentation of magma the chronology of major explosive volcanic eruptions is compared with a record of mean surface temperature deviation t for the same interval constructed from all available temperature data the temperature records are divided into 6 latitudinal zones allowing analysis for individual zones where temperature changes induced by aerosol perturbation might be intensified we focus on the explosive volcanic events which by our estimates injected the most material into the stratosphere these include tambora 1815 krakatau 1883 santa maria 1902 katmai 1912 and quizapu 1932 such eruptions appear to have produced a consistent but small temperature decrease on the order of 0 2 to 0 5 c on a hemispheric scale for periods ranging from one to five years although these changes are similar to background temperature variations the maximum change in t after some of these explosions appears to lag by up to three years in going from equatorial to polar latitudes somewhat smaller eruptions e g agung 1963 and possibly cosiguina 1835 seem to have produced about the same perturbation in t as the larger eruptions this suggests either a limiting mechanism on loading of the aerosol layer after a volcanic eruption or that the composition of injected material i e the ratio of silicate dust to volatiles and composition of the volatiles may significantly effect stratospheric optical depth perturbation temperatures do not remain depressed for a longer period after a series of closely timed eruptions e g the 1881 1889 or the 1902 1903 sequences than after single events

on some radiative features of the el chichon volcanic stratospheric dust cloud and a cloud of unknown origin observed at mauna loa we present some results of our initial optical observations of the el chichon volcanic cloud these observations were made at the geophysical monitoring for climatic change mauna loa observatory hawaii and consist of lidar profiles optical thickness spectral variation in optical thickness and changes in global and direct solar broadband fluxes particle size distribution and cloud mass information contained in the optical thickness observations are discussed it is clear that the atmospheric radiative effects of the el chichon cloud far exceed the effects of all other volcanic clouds observed at mauna loa since observations were begun in 1958