combining local and remote infrasound recordings from the 2009 redoubt volcano eruption abstract the explosive phase of the 2009 redoubt volcano eruption produced predominantly short duration high amplitude infrasound signals recorded up to 4500 km away all 19 numbered explosive events were recorded at a local microphone dfr 12 km as well as at an infrasound array in fairbanks alaska i53us 547 km most with high signal to noise ratios the local microphone provides an estimate of the source parameters and comparison between the two datasets allows the unique opportunity to evaluate acoustic source term estimation at a remote array high waveform similarity between dfr and i53us occurs during much of the explosive phase due to strong stratospheric ducting permitting accurate source constraints inferred from i53us data cross correlation analysis after applying a hilbert transform to the i53us data shows how the acoustic energy has passed through a single caustic as predicted by ray theory similar to previous studies significant low frequency infrasound from redoubt recorded at i53us is coincident with high altitude ash emissions the largest events also produced considerable energy at greater than 50 s periods likely related to the initial oscillations of the volcanic plume or jet many of the explosive events have emergent onsets somewhat unusual for explosive short duration eruptions comparison of the satellite derived so2 emissions with the relative amount of acoustic energy at i53us shows a very high statistically significant correlation this study reiterates the utility of using remote infrasound arrays for detection of hazardous emissions and characterization of large volcanic eruptions and demonstrates how under typical meteorological conditions remote infrasound arrays can provide an accurate representation of the acoustic source

source characterization for an explosion during the 2009 eruption of redoubt volcano from very long period seismic waves abstract the 2009 eruption of redoubt produced several very long period vlp signals associated with explosions we invert for the source location and mechanism of an explosion at redoubt volcano using waveform methods applied to broadband recordings such characterization of the source carries information on the geometry of the conduit and the physics of the explosion process inversions are carried out assuming the volcanic source can be modeled as a point source with mechanisms described by a a set of 3 orthogonal forces b a moment tensor consisting of force couples and c both forces and moment tensor components we find that the source of the vlp seismic waves during the explosion is well described by either a combined moment force source located northeast of the crater and at an elevation of 1 6 km asl or a moment source at an elevation of 800 m to the southwest of the crater the moment tensors for the solutions with moment and force and moment only share similar characteristics the source time functions for both moment tensors begin with inflation pressurization and execute two cycles of deflation reinflation depressurization repressurization although the moment force source provides a better fit to the data we find that owing to the limited coverage of the broadband stations at redoubt the moment only source is the more robust and reliable solution based on the moment only solution we estimate a volume change of 19 000 m3 and a pressure change of 7 mpa in a dominant sill and an out of phase volume change of 5000 m3 and pressure change of 1 8 mpa in a subdominant dike at the source location these results shed new light on the magmatic plumbing system beneath redoubt and complement previous studies on vulcanian explosions at other volcanoes

detection of plumes at redoubt and etna volcanoes using the gps snr method abstract detection and characterization of volcanic eruptions is important both for public health and aircraft safety a variety of ground sensors are used to monitor volcanic eruptions data from these ground sensors are subsequently incorporated into models that predict the movement of ash here a method to detect volcanic plumes using gps signals is described rather than carrier phase data used by geodesists the method takes advantage of attenuations in signal to noise ratio snr data two datasets are evaluated the 2009 redoubt volcano eruptions and the 2013 2015 eruptions at mt etna snr based eruption durations are compared with previously published seismic infrasonic and radar studies at redoubt volcano snr based plume detections from mt etna are compared with l band radar and tremor observations to place these snr observations from redoubt and etna in context a model of the propagation of gps signals through both water water vapor and tephra is developed neither water nor fine ash particles will produce the observed attenuation of gps signals while scattering caused by particles 1 cm in diameter potentially could

eruption chronologies plume heights and eruption styles at tungurahua volcano integrating remote sensing techniques and infrasound article i nfo satellite remote sensing allows volcanic ash plumes to be detected and tracked and routinely aids in hazard mitigation especially to the aviation community although satellite imagery provides valuable information about volcanic plume processes i e plume heights plume composition and plume transport it has its limitations in addition to the observational gaps produced by meteorological clouds as well as temporal and spatial resolution restrictions large volcanic clouds often obscure the vent during an eruption therefore some key information about eruption dynamics and processes are impossible to obtain from satellite images in this paper we investigate four eruptions at tungurahua volcano ecuador during the 2006 2008 time period we integrate satellite derived eruption chronologies plume heights and plume aspect ratios with infrasound data primarily acoustic power and hand held thermal imagery when available integrating these datasets allows us to identify accurate eruption onsets durations and cessations as well as define different types of eruption styles ranging from plinian to weak vulcanian transitions between the different eruption styles were also documented results show that there is a positive correlation between plume height and acoustic power we conclude that combining the two datasets allows better constraints on eruption processes and source parameters using these methods in real time monitoring will allow more accurate eruption monitoring and ash hazard mitigation

cd ca changes in a deep cape basin core over the past 730 000 years response of circumpolar deepwater variability to northern hemisphere ice sheet melting a comparison of cadmium calcium cd ca records of benthic foraminifera from a deep cape basin and a deep eastern equatorial pacific core suggests that over the past 400 000 years the nutrient concentration of circumpolar deep water cpdw has always been lower than that of the deep pacific the data further suggest that at the 100 000 and 23 000 year orbital periods the contribution of north atlantic deep water to cpdw is at a maximum during periods of ice growth and at a minimum during periods of ice decay these results are not in agreement with results based on carbon isotope records of benthic foraminifera which suggest intervals of cpdw nutrient enrichment relative to the deep pacific and an approximately in phase relationship between cpdw nutrient concentration and ice volume resolution of the apparent conflict between 13c and cd ca data may provide important constraints on past deep ocean circulation and nutrient variability

new insights into the 1999 eruption of shishaldin volcano alaska based on acoustic data data collected by a pressure sensor provide new insights into the 1999 eruption of shishaldin volcano unimak island alaska on 19 april 1999 after 3 months of unrest and an extended period of low level strombolian activity shishaldin experienced a subplinian eruption ash plume to 16 km followed by several episodes of strong strombolian explosions acoustic data from the pressure sensor allow us to investigate the details of an eruption which was instrumentally well recorded but with few visual observations in the 12 h prior to the subplinian phase the pressure sensor detected a series of small repeated pulses with a constant spectral peak at 2 3 hz the amplitude and occurrence rate of the pulses both grew such that the signal became a nearly continuous hum just before the subplinian eruption this humming signal may represent gas release from rising magma the main subplinian phase was heralded by 1 the abrupt end of the humming signal 2 several pulses of low frequency sound interpreted as ash bursts and 3 a dramatic increase in seismic tremor amplitude the change in acoustic signature at this time allows us to precisely time the start of the subplinian eruption previously approximated as the time of strongest tremor increase the 50 min subplinian phase actually contained several bursts of signal each of which may represent a discrete volume of magma passing through the system following the subplinian event the pressure sensor recorded four discrete episodes of strombolian gas explosions on 19 20 april and another on 22 23 april four of the five episodes were accompanied by strong seismic tremor the fifth has not been previously recog nized and was not associated with anomalous tremor amplitudes in time series these events are similar to explosions recorded at other volcanoes but in general they are much larger with maximum amplitudes of 65 pa at 6 5 km from the vent and they have low 0 7 1 5 hz peak frequencies these large explosions occurred at rates of 3 20 per minute for 1 5 h in each episode the explosions were accompanied by a small 5 km above sea level ash plume and only minor amounts of ejecta were produced thus the explosion activity was domi nated by gas release

a multidisciplinary effort to assign realistic source parameters to models of volcanic ash cloud transport and dispersion during eruptions during volcanic eruptions volcanic ash transport and dispersion models vatds are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind those models use input parameters called eruption source parameters such as plume height h mass eruption rate duration d and the mass fraction m63 of erupted debris finer than about 4 or 63 m which can remain in the cloud for many hours or days observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected moreover observed plume height may change during an eruption requiring rapid assignment of new parameters this paper reports on a group effort to improve the accuracy of source parameters used by vatds in the early hours of an eruption we do so by first compiling a list of eruptions for which these parameters are well constrained and then using these data to review and update previously studied parameter relationships we find that the existing scatter in plots of h versus yields an uncertainty within the 50 confidence interval of plus or minus a factor of four in eruption rate for a given plume height this scatter is not clearly attributable to biases in measurement techniques or to well recognized processes such as elutriation from pyroclastic flows sparse data on total grain size distribution suggest that the mass fraction of fine debris m63 could vary by nearly two orders of magnitude between small basaltic eruptions 0 01 and large silicic ones 0 5 we classify eleven eruption types four types each for different sizes of silicic and mafic eruptions submarine eruptions brief or vulcanian eruptions and eruptions that generate co ignimbrite or co pyroclastic flow plumes for each eruption type we assign source parameters we then assign a characteristic eruption type to each of the world s 1500 holocene volcanoes these eruption types and associated parameters can be used for ash cloud modeling in the event of an eruption when no observational constraints on these parameters are available

the timing of deglacial circulation changes in the atlantic 1 well dated benthic foraminifer oxygen isotopic records 18o from different water depths and locations within the atlantic ocean exhibit distinct patterns and significant differences in timing over the last deglaciation this has two implications on the one hand it confirms that benthic 18o cannot be used as a global correlation tool with millennial scale precision but on the other hand the combination of benthic isotopic records with independent dating provides a wealth of information on past circulation changes comparing new south atlantic benthic isotopic data with published benthic isotopic records we show that 1 circulation changes first affected benthic 18o in the 1000 2200 m range with marked decreases in benthic 18o taking place at 17 5 cal kyr b p ka due to the southward propagation of brine waters generated in the nordic seas during heinrich stadial 1 hs1 cold period 2 the arrival of 18o depleted deglacial meltwater took place later at deeper north atlantic sites 3 hydrographic changes recorded in north atlantic cores below 3000 m during hs1 do not correspond to simple alternations between northern and southern sourced water but likely reflect instead the incursion of brine generated deep water of northern as well as southern origin and 4 south atlantic waters at 44 s and 3800 m depth remained isolated from better ventilated northern sourced water masses until after the resumption of north atlantic deep water nadw formation at the onset of the bolling allerod which led to the propagation of nadw into the south atlantic

variable water column structure of the south atlantic on glacial interglacial time scales the structure of the glacial ocean was significantly different to that of the present day with intermediate to mid depth waters being notably more 13c enriched than deep waters this contrast was especially pronounced in the south atlantic suggesting the development of a sharp chemical divide or chemocline at around 2500 m water depth between upper and lower layers with implications for deep ocean carbon storage hodell et al 2003 pleistocene vertical carbon isotope and carbonate gradients in the south atlantic sector of the southern ocean geochemistry geophysics geosystems 4 1 doi 1004 10 1029 2002gc000367 we evaluate existing benthic foraminiferal 13c cd ca and derived carbon isotope air sea exchange signature 13cas data sets for the atlantic during the last glacial maximum lgm and marine isotope stages mis 6 and 8 in order to examine the regional extent of the chemocline in the south atlantic benthic 13c data north of the approximate latitude of the lgm subantarctic front lgm saf 43 s linearly decrease with water depth indicative of mixing between upper well and lower poorly ventilated water masses with little evidence of the sharp chemical divide conversely benthic 13c data south of the lgm saf below 2500 m water depth are uniformly around 0 8 the apparent 13c gradient across the lgm saf suggests enhanced mid depth ventilation north of the saf and reduced ventilation to the south from this pattern we conclude that the regional chemocline in the south atlantic constituted a dominantly meridional rather than a vertical gradient and was developed during at least the past three glacial periods benthic cd ca data indicate that the gradient was not nutrient related although further data from the south atlantic are needed for a better assessment of this suggestion the combined benthic 13c and cd ca data indicate the source of well ventilated upper waters in the south atlantic changed from northern component water ncw during early glacial phases to upper southern component water uscw during mid to late glacial phases when the southern ocean may have become isolated uscw maintained a positive 13c and 13cas signature simulating a north atlantic origin that has been implicated in previous studies the data demonstrate that secular imprints on 13c must be taken into consideration when assessing the implications of the vertical 13c gradient this data also supports a variable water column architecture and modes of water mass formation as primary means to draw down atmospheric co2 and storage in the abyssal ocean by involving processes occurring on either side of the saf in the glacial southern ocean

thermodynamic influences on the marine carbon isotope record air sea exchange represents an important controlling factor for the distribution of carbon isotopes in the modern ocean even below the surface mixed layer here we show that this thermodynamic influence varies between water masses with a magnitude which is large relative to the amplitude of typical deep sea sediment 13c records thus changes in air sea exchange processes must be regarded as a significant source of variability for any marine 13c signal

tracing the differences between vulcanian and strombolian explosions using infrasonic and thermal radiation energy abstract eruptive plume dynamics is a direct expression of explosive style where duration and altitude of eruptive clouds and dispersion of erupted products is proportional to the degree of fragmentation we present an analysis of infrasonic and thermal records for explosions at villarrica chile stromboli italy santiaguito and fuego guatemala volcanoes across these four systems magma composition spans from basaltic to dacitic and explosive activity is typically described as ranging from strombolian to vulcanian we use this analysis to provide a quantitative geophysically based description of and discrimination between the different explosive styles that characterize the four volcanoes while infrasound is directly related to the emission of over pressurized gas and thus solely reflects the plume emission both plume emission and ascent are detected thermally thus the two data sets together provide a complete description of the plume dynamics in particular while infrasound solely reflects the gas thrust phase driving plume emission thermal radiation energy is also affected by buoyancy during plume ascent thermal radiation energy estimated for explosions at stromboli and villarrica 10 4 10 7 j is lower than that for events at santiaguito and fuego 10 8 10 9 j but infrasonic energies overlap this suggests a greater contribution of buoyancy for eruptive clouds at santiaguito and fuego when compared with stromboli and villarrica we further investigated the plume dynamics by comparing infrasonic energy which reflects gas thrust e gt with the difference between thermal radiation and infrasonic energies which mostly reflects buoyancy e b our data distribution reveals two separate clusters explosions at stromboli and villarrica share low values of buoyancy pointing to a gas thrust dominated emission efficient coupling of the infrasonic source to the atmosphere and a strombolian type source process to generate a plume rich in coarse fragments in contrast explosions at santiaguito and fuego share large buoyancy e b and are consistent with vulcanian type events in which a large part of infrasonic energy is spent in magma fragmentation leading to ascent of buoyant ash rich plumes we demonstrate that the comparison between thermal radiation and infrasonic energies of explosions allows a quantitative discrimination between and characterization of strombolian and vulcanian type explosions which leads us to suggest that such an approach may be used as an index to further and quantitatively discriminate between eruptive styles

relative partitioning of acoustic and seismic energy during strombolian eruptions the relative elastic energy partitioning during strombolian eruptions can be estimated from acoustic pressure and seismic velocity records we outline methods for determining acoustic and seismic energies for sensors deployed within several kilometers of erupting vents we use these energies to introduce the concept of the volcano acoustic seismic ratio g or vasr which is the ratio of elastic energy propagated through the atmosphere and into the earth eruption vasr is a physical diagnostic of explosive degassing that is appropriate for comparing eruption mechanisms at individual and between various volcanoes here we assess acoustic and seismic energies and corresponding vasr for discrete strombolian explosive events at karymsky and erebus volcanoes we attribute the relatively high and stable vasr at erebus g 8 standard deviation 41 to repeatable source conditions occurring at the surface of a persistent lava lake with accompanying strong coupling to the atmosphere lower and more variable vasr at karymsky g 0 18 in 1998 to g 1 51 in 1991 with standard deviations of 93 and 313 respectively is attributed to changing conditions within a narrow partially choked conduit variable seismoacoustic energy partitioning for karymsky as manifested by the large vasr standard deviation suggests that conduit conditions affecting vasr which include magma properties conduit obstruction or fragmentation depths can evolve both during the course of an explosion and between successive events d 2005 elsevier b v all rights reserved

carbon isotope offsets between benthic foraminifer species of the genus cibicides cibicidoides in the glacial sub antarctic atlantic epibenthic foraminifer 13c measurements are valuable for reconstructing past bottom water dissolved inorganic carbon 13c 13cdic which are used to infer global ocean circulation patterns epibenthic 13c however may also reflect the influence of 13c depleted phytodetritus microhabitat changes and or variations in carbonate ion concentrations here we compare the 13c of two benthic foraminifer species cibicides kullenbergi and cibicides wuellerstorfi and their morphotypes in three sub antarctic atlantic sediment cores over several glacial interglacial transitions these species are commonly assumed to be epibenthic living above or directly below the sediment water interface while this might be consistent with the small 13c offset that we observe between these species during late pleistocene interglacial periods 13c 0 19 0 31 n 63 it is more difficult to reconcile with the significant 13c offset that is found between these species during glacial periods 13c 0 76 0 44 n 44 we test possible scenarios by analysing uvigerina spp 13c and benthic foraminifer abundances 1 c kullenbergi 13c is biased to light values either due to microhabitat shifts or phytodetritus effects and 2 c wuellerstorfi 13c is biased to heavy values relative to long term average conditions for instance by recording the sporadic occurrence of less depleted deep water 13cdic neither of these scenarios can be ruled out unequivocally however our findings emphasize that supposedly epibenthic foraminifer 13c in the sub antarctic atlantic may reflect several factors rather than being a sole function of bottom water 13cdic which directly bear on the interpretation of extremely light south atlantic 13c values at the last glacial maximum

anatomy of a lava dome collapse the 20 march 2000 event at soufriere hills volcano montserrat abstract a second extrusive phase of the currently ongoing 1995 2003 eruption of soufriere hills volcano shv montserrat commenced in mid november 1999 following 19 months during which no fresh lava had reached the surface by mid march 2000 a new andesite lava dome constructed within a collapse scar girdled by remnants of the 1995 1998 dome complex had attained an estimated volume of 29 3 million m3 mm3 on 20 march 2000 during a period of heavy rainfall on the island a significant collapse event ensued that removed 95 of the new lava dome 28 3 mm3 during 5 hours of activity that generated 40 pyroclastic flows and at least one magmatic explosion the associated ash cloud reached an altitude of 9 km and deposited ash on the island of guadeloupe to the southeast and a number of lahars and debris flows occurred in valleys on the flanks of shv a large quantity of observational data including contemporaneous field observations and continuous data from the broadband seismic network on montserrat allow a detailed reconstruction of this dome collapse event in contrast to most of the large dome collapses at shv the 20 march 2000 event is distinguished by a lack of short term precursory elevated seismicity at shallow depths beneath the lava dome broadband seismic amplitude data recorded during the event are used to infer the cumulative volume of collapsed dome as the collapse progressed these data indicate that the high velocity pyroclastic flows observed at the climax of the event removed by far the largest portion 68 of the lava dome at peak discharge rates estimated from the seismic record of 2 104 m3 s 1 following the 20 march 2000 collapse lava dome growth recommenced immediately and continued without significant interruption until another larger dome collapse occurred on 29 july 2001 the 29 july 2001 event also coincided with heavy rainfall on montserrat matthews et al 2002 geophys res lett 29 doi 10 1029 2002gl014863 and lacked precursory elevated seismic activity we attribute the initiation of the 20 march 2000 collapse to a prolonged spell of heavy rainfall on the lava dome prior to and during the event the precise causal mechanism remains controversial though some combination of mechanical erosion and or destabilization of a critically poised face of the lava dome the action of pressurized steam or water on potential failure surfaces within the dome rapid cooling of hot lava and small phreatic explosions seems likely anecdotal evidence exists for other rainfall induced activity on montserrat and the triggering of explosive or pyroclastic flow activity by rainfall has been noted at dome forming volcanoes elsewhere including merapi indonesia voight et al 2000 j volcanol geotherm res 100 69 138 unzen japan yamasato et al 1997 papers meteorol geophys 48 santiaguito guatemala smithsonian institution global volcanism network bull 15 1990 and mount st helens usa mastin 1994 geol soc am bull 106 175 185 hazard mitigation plans at dome forming volcanoes would therefore benefit from the inclusion of meteorological forecasting and rain monitoring equipment particularly in the tropics

character mass distribution and origin of tephra fall deposits from the 2009 eruption of redoubt volcano alaska highlighting the significance of particle aggregation abstract the 2009 eruption of redoubt volcano included 20 tephra producing explosions between march 15 2009 and april 4 2009 utc next generation radar nexrad data show that plumes reached heights between 4 6 km and 19 km asl and were distributed downwind along nearly all azimuths of the volcano explosions lasted between 0 8 mm thick including communities along the kenai peninsula 80 100 km and the city of anchorage 170 km trace ash on march 15 a small 4 6 km asl phreatic explosion containing minor non juvenile ash erupted through the summit ice cap the first five magmatic explosions events 1 5 occurred within a 6 hour period on march 23 plumes rose to heights between 5 5 km and 14 9 km asl during 2 to 20 minute duration explosions and were dispersed mainly along a nne trajectory trace ash fall was reported as far as fairbanks owing to a shift in wind direction and heavy snowfall during these events field discrimination among many of these layers was possible all deposits comprise a volumetrically significant amount of particle aggregates yet only event 5 deposits contain coarse clasts including glacier ice the most voluminous tephra fall was deposited on march 24 event 6 from a 15 minute explosion that sent a plume to 18 3 km asl and dispersed tephra to the wnw within 10 km of the vent this deposit contains 1 11 cm pumice clasts in a matrix of 1 2 mm aggregate lapilli a small dome was presumably emplaced between march 23 and march 26 and was subsequently destroyed during 1 14 minute magmatic explosions of events 7 8 march 26 that sent plumes between 8 2 km and 19 km asl ash fell along a broad swath to the ese covering communities along the kenai peninsula with up to 1 mm of ash proximal deposits are largely composed of aggregate lapilli of 1 2 mm with very little coarse juvenile material events 9 18 march 27 sent plumes between 5 2 km and 15 5 km asl during particle size data showing a preponderance of fine ash even in the most proximal locations along with the abundance of aggregate lapilli documented in most samples confirms that particle aggregation played a significant role in the 2009 eruption and induced premature fallout of fine ash

late quaternary variations in sea surface temperatures and their relationship to orbital forcing recorded in the southern ocean atlantic sector late quaternary summer sea surface temperatures ssts have been derived from radiolarian assemblages in the east atlantic sector of the southern ocean in the subantarctic and the polar frontal zone glacial ssts oxygen isotope stages 2 4 6 and 8 were 3 5 c cooler than today indicating northward displacements of the isotherms about 2 4 of latitudes during interglacials ssts almost reached modern levels oxygen isotope stages 7 and 9 or exceeded them by 2 3 c oxygen isotope stages 1 and 5 5 in the subantarctic atlantic ocean changes in sst and calcium carbonate content of the sediment precede variations in global ice volume in the range of the main milankovitch frequencies comparisons with the timing of north atlantic deep water nadw proxy records suggests that this early response in the subantarctic atlantic ocean is not triggered by the flux of nadw to the southern ocean

observations of volcanic lightning during the 2009 eruption of redoubt volcano abstract observations of volcanic lightning during the eruption of redoubt volcano in march and april 2009 were made with the lightning mapping array during the eruption twenty three distinct episodes of volcanic lightning were observed electrical activity occurred as either a volcanic lightning storm with up to thousands of lightning discharges or as a weak electrical event with only a handful of lightning discharges during the volcanic lightning storms we observed two phases of electrical activity the explosive phase and the plume phase the explosive phase consisted of very small discharges on the order of 10 100 m occurring directly above the vent while an explosive eruption was ongoing whereas the plume phase was comprised of discharges occurring throughout the plume subsequent to the explosive eruption the area of discharges during the explosive phase ranged from less than 1 km2 to 50 km2 or more the electrical activity at the beginning of the plume phase was dominated by small discharges over time the horizontal extent of the flashes increased with the largest flashes occurring at the end of the plume phase the distribution of the horizontal size of the discharges over the lifetime of the storm indicate that the charge structure of the plume evolved from a complex and clumpy structure to a more simple horizontally stratified structure plume height was shown to be a key factor in the quantity of lightning in a storm the volcanic lightning storms occurred in plumes with column heights greater than 10 km the tall plumes may contribute to the efficiency of charge generation through ice collisions by providing strong updrafts from the large thermal energy input from the eruption

multiparameter quantification of gas release during weak strombolian eruptions at pacaya volcano guatemala 1 activity at pacaya volcano guatemala is characterized by persistent degassing coupled at times with lava effusion and or coincident strombolian style explosions we used 0 25 hz sample rate sulfur dioxide emission data from a uv camera and coincident infrasound recordings to investigate the link between varied emission rates and infrasound events degassing rates varied on two scales during this study smaller more rapid variations on the scale of 1 to 3 minutes are superimposed on larger slower changes over 30 minutes to 1 hour the acoustic record was dominated by repeated n shaped events characteristic of strombolian explosions because of the high resolution of the gas measurements we were able to calculate gas masses for individual explosions from both datasets and find the two estimates agree within an order of magnitude the infrasound explosion records correlate with small pulses in degassing but the longer term degassing trends may represent a deeper process

interocean exchange of glacial north atlantic intermediate water evidence from subantarctic cd ca and carbon isotope measurements new measurements of cd ca ratios for glacial benthic foraminifera from the continental shelf and slope off tasmania and south australia are presented when combined with glacial carbon isotope measurements lynch stieglitz et al 1994 these data from the glacial subantarctic zone suggest that a water mass with a high value of the conservative tracer 13cas occupied not only the shallow 1 2 km portions of the atlantic and pacific oceans but was present in the glacial subantarctic as well the oceanic cd concentrations cdw predicted for the glacial subantarctic are intermediate between those from the glacial atlantic and the glacial pacific supporting the idea that glacial north atlantic intermediate water may have reached the intermediate depth pacific via the antarctic circumpolar circulation lynch stieglitz and fairbanks 1994

local seismic and infrasound observations of the 2009 explosive eruptions of redoubt volcano alaska article i nfo local seismic and infrasound data are used to characterize the march april 2009 eruptions of redoubt volca no alaska data are from a network of ten seismic stations ranging from 2 6 to 21 km from the vent and a single infrasound sensor 12 2 km from the vent measurements were made for more than 30 explosive erup tions including the 19 numbered events that were identified during the eruption response more than 30 smaller explosions were also identified measured parameters include onset time duration reduced dis placement dr pressure seismic energy and acoustic energy results were compared with complementary gas and lightning data based on ratios of pressure to dr and acoustic to seismic energy we find that the initial group of explosive eruptions on 23 24 march was relatively stronger seismically and included the four highest dr values we infer that these represent vent enlargement or stronger coupling between the magma and wall rocks one event at 12 31 ut on 23 march had an extremely high pressure of 250 pa for the initial pulse and was likely weakly seismically coupled a second group of explosive eruptions on 27 29 march was relatively stronger acoustically deposits were finer grained and of different lithology with less scoria and more dense clasts these two groups may represent different modes of gas release cumulative acoustic energy as a function of time correlates well with comparable lightning and so2 data suggesting that all three provide insight regarding different factors of gas release for the eruption as a whole the number of events identified depends on criteria measured and depends on the goals of the investigations overall the eruptions were substantially stronger than recent eruptions in alaska with some durations exceeding 1 h and pressures an order of magnitude higher

seismo acoustic evidence for an avalanche driven phreatic eruption through a beheaded hydrothermal system an example from the 2012 tongariro eruption abstract the 6 august 2012 te maari eruption comprises a complex eruption sequence including multiple eruption pulses a debris avalanche that propagated 2 km from the vent and the formation of a 500 m long arcuate chasm located 300 m from the main eruption vent the eruption included 6 distinct impulses that were coherent across a local infrasound network marking the eruption onset at 11 52 18 all times utc an eruption energy release of 3 1012 j was calculated using a body wave equation for radiated seismic energy a similar calculation based on the infrasound record shows that 90 of the acoustic energy was released from three impulses at onset times 11 52 20 20 of total eruption energy 11 52 27 50 and 11 52 31 20 these energy impulses may coincide with eyewitness accounts describing an initial eastward directed blast followed by a westward directed blast and a final vertical blast pre eruption seismic activity includes numerous small unlocatable micro earthquakes that began at 11 46 50 two larger high frequency earthquakes were recorded at 11 49 06 and 11 49 21 followed directly by a third earthquake at 11 50 17 the first event was located within the scarp based on an arrival time location from good first p arrival times and probably represents the onset of the debris avalanche the third event was a tornillo characterised by a 0 8 hz single frequency resonance and has a resonator attenuation factor of q 40 consistent with a bubbly fluid filled resonator this contrasts with a similar tornillo event occurring 2 5 weeks earlier having q 250 1000 consistent with a dusty gas charged resonator we surmise from pre eruption seismicity and the observed attenuation change that the debris avalanche resulted from the influx of fluids into the hydrothermal system causing destabilisation and failure the beheaded hydrothermal system may have then caused depressurisation frothing of the remaining gas charged system leading to the onset of explosive activity

comparison of atlantic and pacific paleochemical records for the last 215 000 years changes in deep ocean circulation and chemical inventories abstract detailed cd ca and 13 c data have been obtained for benthic foraminifera from western north atlantic and equatorial pacific sediment cores in the modern ocean both tracers are closely linked to nutrient distributions the sedimentary records for both tracers indicate that bottom waters overlying the atlantic site have been nutrient depleted relative to those at the pacific site over the last 215 000 years from this evidence it is reasonable to infer that there has been a continuous net flux of nutrient depleted water from the western north atlantic into the pacific this exchange has undergone significant fluctuations with the export of nutrient depleted atlantic water diminishing by about a factor of two relative to the inflow from southern ocean sources over the last 215 000 years carbon isotope fluctuations in both regions are dominated by variable storage of isotopically light carbon on continents with a lesser contribution from these deep ocean circulation changes the cadmium signal in the north atlantic is dominated by changes in deep ocean circulation patterns cadmium shows less variability in the pacific which may reflect changes in the global average cadmium content or minor changes in deep pacific circulation patterns using these records to estimate global averages it appears that glacial ocean water had 22 more cd and 0 46 less 13 c than the modern ocean these numbers are estimates which may be revised as more data become available although they are not likely to be as much as 20 in error for cd or 0 2 for 13 c relative north atlantic deep water nadw formation rates are modulated with a significant 41 kyr periodicity linked to obliquity induced variations in high latitude insolation nadw lags 8 2 kyr behind insolation however

an overview of the 2009 eruption of redoubt volcano alaska abstract in march 2009 redoubt volcano alaska erupted for the first time since 1990 explosions ejected plumes that disrupted international and domestic airspace sent lahars more than 35 km down the drift river to the coast and resulted in tephra fall on communities over 100 km away geodetic data suggest that magma began to ascend slowly from deep in the crust and reached mid to shallow crustal levels as early as may 2008 heat flux at the volcano during the precursory phase melted 4 of the drift glacier atop redoubt s summit petrologic data indicate the deeply sourced magma low silica andesite temporarily arrested at 9 11 km and or at 4 6 km depth where it encountered and mixed with segregated stored high silica andesite bodies the two magma compositions mixed to form intermediate silica andesite and all three magma types erupted during the earliest 2009 events only intermediate and high silica andesites were produced throughout the explosive and effusive phases of the eruption the explosive phase began with a phreatic explosion followed by a seismic swarm which signaled the start of lava effusion on march 22 shortly prior to the first magmatic explosion early on march 23 2009 utc more than 19 explosions or events were produced over 13 days from a single vent immediately south of the 1989 90 lava domes during that period multiple small pyroclastic density currents flowed primarily to the north and into glacial ravines three major lahars flooded the drift river terminal over 35 km down river on the coast tephra fall deposited on all aspects of the edifice and on several communities north and east of the volcano and at least two and possibly three lava domes were emplaced lightning accompanied almost all the explosions a shift in the eruptive character took place following event 9 on march 27 in terms of infrasound signal onsets the character of repeating earthquakes and the nature of tephra ejecta more than nine additional explosions occurred in the next two days followed by a hiatus in explosive activity between march 29 and april 4 during this hiatus effusion of a lava dome occurred whose growth slowed on or around april 2 the final explosion pulverized the very poorly vesicular dome on april 4 and was immediately followed by the extrusion of the final dome that ceased growing by july 1 2009 and reached 72 m m 3 in bulk volume the dome remains as of this writing effusion of the final dome in the first month produced blocky intermediate to high silica andesite lava which then expanded by means of lava injection beneath a fracturing and annealing cooling surface crust in the first week of may a seismic swarm accompanied extrusion of an intermediate to high silica andesite from the apex of the dome that was highly vesicular and characterized by lower p 2 o 5 content the dome remained stable throughout its growth period likely due to combined factors that include an emptied conduit system steady degassing through coalesced vesicles in the effusing lava and a large crater pit created by the previous explosions we estimate the total volume of erupted material from the 2009 eruption to be between 80 m and 120 m m 3 dense rock equivalent dre the aim of this report is to synthesize the results from various datasets gathered both during the eruption and retrospectively and which are represented by the papers in this publication we therefore provide an overall view of the 2009 eruption and an introduction to this special issue publication

long range acoustic observations of the eyjafjallajokull eruption iceland april may 2010 1 the april may 2010 summit eruption of eyjafjallajokull iceland was recorded by 14 atmospheric infrasound sensor arrays at ranges between 1 700 and 3 700 km indicating that infrasound from modest size eruptions can propagate for thousands of kilometers in atmospheric waveguides although variations in both atmospheric propagation conditions and background noise levels at the sensors generate fluctuations in signal to noise ratios and signal detectability array processing techniques successfully discriminate between volcanic infrasound and ambient coherent and incoherent noise the current global infrasound network is significantly more dense and sensitive than any previously operated network and signals from large volcanic explosions are routinely recorded because volcanic infrasound is generated during the explosive release of fluid into the atmosphere it is a strong indicator that an eruption has occurred therefore long range infrasonic monitoring may aid volcanic explosion detection by complementing other monitoring technologies especially in remote regions with sparse ground based instrument networks

feasibility study of spectral pattern recognition reveals distinct classes of volcanic tremor abstract systematic investigations of the similarities and differences among volcanic tremor at a range of volcano types may hold crucial information about the plausibility of inferred source mechanisms which in turn may be important for eruption forecasting however such studies are rare in part because of an intrinsic difficulty with identifying tremor signals within very long time series of volcano seismic data accordingly we develop an efficient tremor detection algorithm and identify over 12 000h of volcanic tremor on 24 stations at k lauea okmok pavlof and redoubt volcanoes we estimate spectral content over 5 minute tremor windows and apply a novel combination of principal component analysis pca and hierarchical clustering to identify patterns in the tremor spectra analyzing several stations from a given volcano together reveals different styles of tremor within individual volcanic settings in addition to identifying tremor properties common to all stations in a given network we find localized tremor signals including those related to processes such as lahars or dike intrusions that are only observed on some of the stations within a network subsequent application of our analysis to a combination of stations from the different volcanoes reveals that at least three main tremor classes can be detected across all settings whereas a regime with a ridge of high power distributed over 1 2hz and a gradual decay of spectral power towards higher frequencies is observed dominantly at three volcanoes k lauea okmok redoubt with magma reservoirs centered at less than 5km below sea level b s l a spectrum with a steeper slope and a narrower peak at 1 2hz is observed only in association with open vents k lauea and pavlof a third regime with a peak at approximately 3hz is confined to two stratovolcanoes pavlof and redoubt these observations suggest generic relationships between the spectral character of the observed signals and volcano characteristics such as magma viscosity storage depths and the physical properties of volcanic edifices similarities among the spectral patterns detected at stations 4km and 8 10km distance from the centers of volcanic activity respectively indicate that path effects do not strongly influence spectral shapes at distances of a few kilometers from the inferred source of the signals our preliminary work shows that a global comparison of tremor is feasible our results suggest that further work on data from a larger sample and diverse range of volcano types will reveal additional classes of tremor signals and plausibly identify fingerprints of source processes that are specific to volcano type but independent of volcano location

feldspar in type 4 6 ordinary chondrites metamorphic processing on the h and ll chondrite parent bodies abstract we have carried out a study of feldspar compositions in a suite of h and ll ordinary chondrites of petrologic types 4 5 and 6 in order to examine the process of recrystallization and equilibration of feldspar as the degree of metamorphism increases in the h chondrites there is little variation in feldspar compositions among the petrologic types suggesting that homogenization of chondrule mesostasis from which feldspar is presumed to have crystallized occurred before feldspar crystallization began the ll chondrites we studied are more complex in bjurbole l ll4 plagioclase in individual relict chondrules has distinct compositions with a range of an ab ratios and low or contents this heterogeneity is most likely attributable to original compositional heterogeneity among chondrule mesostases localized recrystallization of mesostasis must have occurred before diffusional equilibration took place in tuxtuac ll5 the an ab ratio of plagioclase is more homogeneous and plagioclase includes a significant or component in addition we observe what appears to be exsolution of k feldspar from albitic host grains in saint severin ll6 the an ab ratio of plagioclase is homogeneous but plagioclase compositions show a range of or contents corresponding to a patchy distribution of k in individual feldspar grains the observations in these ll chondrites are difficult to interpret with a simple model of progressive equilibration with increasing petrologic type we suggest that the current criteria for assigning petrologic types are poorly defined it is possible that the assigned petrologic types of these chondrites do not correlate with their peak temperatures we propose that feldspar compositions might record conditions during the heating stage of metamorphism and that the early stages of metamorphism may have occurred in the presence of fluids rather than under the dry conditions that are commonly assumed

investigating spectral distortion of local volcano infrasound by nonlinear propagation at sakurajima volcano japan author s maher s p matoza r s de groot hedlin c d gee k l fee d yokoo a

local infrasound observations of large ash explosions at augustine volcano alaska during january 11 28 2006 1 we present and interpret acoustic waveforms associated with a sequence of large explosion events that occurred during the initial stages of the 2006 eruption of augustine volcano alaska during january 11 28 2006 13 large explosion events created ash rich plumes that reached up to 14 km a s l and generated atmospheric pressure waves that were recorded on scale by a microphone located at a distance of 3 2 km from the active vent the variety of recorded waveforms included sharp n shaped waves with durations of a few seconds impulsive signals followed by complex codas and extended signals with emergent character and durations up to minutes peak amplitudes varied between 14 and 105 pa inferred acoustic energies ranged between 2 108 and 4 109 j a simple n shaped short duration signal recorded on january 11 2006 was associated with the vent opening blast that marked the beginning of the explosive eruption sequence during the following days waveforms with impulsive onsets and extended codas accompanied the eruptive activity which was characterized by explosion events that generated large ash clouds and pyroclastic flows along the flanks of the volcano continuous acoustic waveforms that lacked a clear onset were more common during this period on january 28 2006 the occurrence of four large explosion events marked the end of this explosive eruption phase at augustine volcano after a transitional period of about two days characterized by many small discrete bursts the eruption changed into a stage of more sustained and less explosive activity accompanied by the renewed growth of a summit lava dome

effects of midlatitude westerlies on the paleoproductivity at the agulhas bank slope during the penultimate glacial cycle evidence from coccolith sr ca ratios modern primary productivity on the agulhas bank off south africa has been proposed to be linked to the midlatitude westerlies a paleoproductivity record from this area may therefore resolve temporal changes in the westerly dynamics accordingly we produced a coccolith sr ca based paleoproductivity record from core md96 2080 agulhas bank slope during the penultimate glacial interglacial cycle deriving the productivity signal from sr ca requires a correction for a temperature effect here constrained using mg ca sea surface temperatures from the foraminifer globigerina bulloides from core md96 2080 phases of depressed productivity coincided with periods of stratification in the same core indicated by high relative abundances of the coccolithophore florisphaera profunda and with low relative abundances of the upwelling indicator g bulloides in the nearby cape basin these observations collectively suggest that productivity was regulated by upwelling throughout this region we infer that as in the present periods of low productivity result from a more northerly position of the westerlies potentially accompanied by subtropical front displacements and blockage of upwelling promoting easterlies productivity minima also coincide with periods of increased ice rafted detritus ird deposition on the agulhas plateau which also indicates extreme northward positions of the westerlies the influence of the westerlies appears to be obliquity conditioned as productivity minima and ird maxima occur during low obliquity intervals the dynamic connection between productivity and the westerlies is supported by coeval salinity changes in the south indian gyre that likewise respond sensitively to a poleward contraction of the westerlies

characterization and interpretation of volcanic activity at karymsky volcano kamchatka russia using observations of infrasound volcanic emissions and thermal imagery 2 a multiparameter data set including measurements of infrasound volcanic emissions and thermal imagery is used to characterize and interpret diverse volcanic activity observed during field campaigns in august 2011 and july 2012 at karymsky volcano kamchatka russia four activity types are visually identified and characterized according to so2 emission rate ash mass event duration peak temperature thermal radiation energy infrasound onset and frequency reduced infrasonic pressure and acoustic energy these activity types include 1 ash explosions 2 pulsatory degassing 3 gas jetting and 4 explosive eruption unique infrasound signals are associated with all four activity types suggesting that infrasound can be used to help remotely and continuously detect and characterize volcanic activity at karymsky and other similar volcanoes our observations suggest that so2 is emitted continuously though in varying abundance while ash is emitted discontinuously and is only associated with certain types of activity our data set supports previous models that attribute variations in surface activity to changes in conduit permeability at karymsky volcano evidence for a decrease in conduit permeability as a trigger for ash explosions and explosive eruption activity types is supported by weakened but still detectable so2 emission rates prior to eruption along with the highly impulsive infrasonic onset and large reduced infrasound pressure indicating high pressure at the vent we speculate that changes in conduit permeability at karymsky volcano result from changes in magma supply from the shallow crustal storage region though additional measurements are required to validate this hypothesis

last glacial sea surface temperatures and sea ice extent in the southern ocean atlantic indian sector a multiproxy approach 1 on the basis of the quantitative study of diatom radiolarian and planktic foraminiferal assemblages we estimated summer sea surface temperature ssst and sea ice extent at 50 sediment core localities in the atlantic and western indian sector of the southern ocean to reconstruct the last glacial environment at the glamap 18 to 15 ka equal to 21 500 to 18 000 calendar cal years bp and epilog 19 5 to 16 0 ka equal to 23 000 to 19 000 cal years bp time slices stratigraphic identification of the time slices was accomplished by a combination of ams 14c measurements benthic isotope and siliceous microfossil abundance records while the ssst estimates reveal greater surface water cooling than reconstructed by climap 1981 reaching a maximum in the area of the present subantarctic zone the sea ice reconstruction indicates that climap overestimated the expansion of the antarctic sea ice field especially for austral summer during winter the sea ice field was expanded by 60 70 compared to the present last glacial summer sea surface isotherms indicate a northward shift of the zonal bands of the antarctic circumpolar current and a relative expansion of the cold water realm south of the subantarctic front by 5 in latitude this coincides with a northward displacement of the zone of enhanced biogenic silica deposition and iceberg occurrence as a result of northward expansion of antarctic cold waters and a relatively small displacement of the subtropical front thermal gradients were steepened during the last glacial in the area of the present subtropical front the northward displacement of antarctic cold waters and the related deflection of southern ocean waters along the eastern boundary of south america may have resulted in a weakened cold water route across the drake passage in contrast the transport of warm and salty surface water from the indian into the atlantic ocean via the warm water route was not blocked allowing continuous but reduced import of heat into the south atlantic

changes in the mode of southern ocean circulation over the last glacial cycle revealed by foraminiferal stable isotopic variability benthic foraminiferal oxygen and carbon isotopic records from southern ocean sediment cores show that during the last glacial period the south atlantic sector of the deep southern ocean filled to roughly 2500 m with water uniformly low in 13c resulting in the appearance of a strong mid depth nutricline similar to those observed in glacial northern oceans concomitantly deep water isotopic gradients developed between the pacific and atlantic sectors of the southern ocean the 13c of benthic foraminifera in pacific sediments remained significantly higher than those in the atlantic during the glacial episode these two observations help to define the extent of what has become known as the southern ocean low 13c problem one explanation for this glacial distribution of 13c calls upon surface productivity overprints or changes in the microhabitat of benthic foraminifera to lower glacial age 13c values we show here however that glacial interglacial 13c shifts are similarly large everywhere in the deep south atlantic regardless of productivity regime or sedimentary environment furthermore the degree of isotopic decoupling between the atlantic and pacific basins is proportional to the magnitude of 13c change in the atlantic on all time scales thus we conclude that the profoundly altered distribution of 13c in the glacial southern ocean is most likely the result of deep ocean circulation changes while the characteristics of the southern ocean 13c records clearly point to reduced north atlantic deep water input during glacial periods the basinal differences suggest that the mode of southern ocean deep water formation must have been altered as well

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

the influence of air sea exchange on the isotopic composition of oceanic carbon observations and modeling although the carbon isotropic composition of ocean waters after they leave the surface ocean is determined by biological cycling air sea exchange affects the carbon isotopic composition of surface waters in two ways the equilibrium fractionation between oceanic and atmospheric carbon increases with decreasing temperature in southern ocean surface waters this isotopic equilibrium enriches delta sup 13 c relative to the delta sup 13 c expected from uptake and release of carbon by biological processes alone similarly surface waters in the subtropical gyres are depleted in delta sup 13 c due to extensive air sea exchange at warm temperatures countering the tendency toward isotopic equilibration with the atmosphere a relatively slow process are the effects of the equilibration of co sub 2 itself a much faster process in regions where there is a net transfer of isotopically light co sub 2 from the ocean to the atmosphere e g the equator surface waters become enriched in sup 13 c whereas in regions where isotopically light co sub 2 is entering the ocean e g the north atlantic surface waters become depleted in sup 13 c a compilation of high quality oceanic delta sup 13 c measurements along with experiments performed using a zonally averaged three basin dynamic ocean model are used to explore these processes 40 refs 14more figs 1 tab less

infrasonic observations of the june 2009 sarychev peak eruption kuril islands implications for infrasonic monitoring of remote explosive volcanism abstract sarychev peak sp located on ostrov matua kurils erupted explosively during 11 16 june 2009 whereas remote seismic stations did not record the eruption we report atmospheric infrasound acoustic wave 0 01 20 hz observations of the eruption at seven infrasound arrays located at ranges of 640 6400 km from sp the infrasound arrays consist of stations of the international monitoring system global infrasound network and additional stations operated by the korea institute of geoscience and mineral resources signals at the three closest recording stations is44 643 km petropavlovsk kamchatskiy kamchatka krai russia is45 1690 km ussuriysk russia and is30 1774 km isumi japan represent a detailed record of the explosion chronology that correlates well with an eruption chronology based on satellite data terra noaa mtsat the eruption chronology inferred from infrasound data has a higher temporal resolution than that obtained with satellite data atmosphere corrected infrasonic source locations determined from backazimuth cross bearings of first arrivals have a mean centroid 15 km from the true location of sp scatter in source locations of up to 100 km result from currently unresolved details of atmospheric propagation and source complexity we observe systematic time variations in trace velocity backazimuth deviation and signal frequency content at is44 preliminary investigation of atmospheric propagation from sp to is44 indicates that these variations can be attributed to solar tide variability in the thermosphere it is well known that additional information about active volcanic processes can be learned by deploying infrasonic sensors with seismometers at erupting volcanoes this study further highlights the significant potential of infrasound arrays for monitoring volcanic regions such as the kurils that have only sparse seismic network coverage

detecting hidden volcanic explosions from mt cleveland volcano alaska with infrasound and ground coupled airwaves 1 in alaska where many active volcanoes exist without ground based instrumentation the use of techniques suitable for distant monitoring is pivotal in this study we report regional scale seismic and infrasound observations of volcanic activity at mt cleveland between december 2011 and august 2012 during this period twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent and ground coupled acoustic waves were recorded at seismic stations across the aleutian arc several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data however many explosions eluded initial automated analyses of satellite data due to poor weather conditions infrasound and seismic monitoring provided effective means for detecting these hidden events we present results from the implementation of automatic infrasound and seismo acoustic eruption detection algorithms and review the challenges of real time volcano monitoring operations in remote regions we also model acoustic propagation in the northern pacific showing how tropospheric ducting effects allow infrasound to travel long distances across the aleutian arc the successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at mt cleveland

antarctic sea ice and the control of pleistocene climate instability a hypothesis is presented for the origin of pleistocene climate instability based on expansion of antarctic sea ice and associated changes in the oceans salinity structure the hypothesis assumes that thermohaline overturning is dominated by the reconfigured conveyor of toggweiler and samuels 1993b in which deepwater upwelling is restricted to high southern latitudes the reconfigured conveyor is shown to be potentially stabilized in an on mode by precipitation at high southern latitudes and potentially destabilized into on and off modes by the counteracting influence of antarctic sea ice the mechanism is clarified by the use of a hydraulic analogue we hypothesize that this mechanism accounts for dominant patterns of thermohaline overturning and climate instability between pleistocene warm and cold periods the hypothesis is shown to be consistent with a range of paleoceanographic evidence and to potentially account for details of observed rapid climate changes during glacial and interglacial periods including aspects of interhemispheric timing

infrasound observations of the 2008 explosive eruptions of okmok and kasatochi volcanoes alaska 1 the recent explosive eruptions of okmok and kasatochi volcanoes provide an opportunity to use seismic local infrasound distant infrasound array and remote sensing data in concert to better monitor volcanoes in the aleutian arc and to better understand the source processes the eruption of okmok volcano began on 12 july 2008 and included a seismically active phase that lasted continuously for about 10 h in contrast the eruption of kasatochi which began on 7 august 2008 consisted of five explosive events that lasted from 26 to 68 min each and had a cumulative duration of 3 4 h given the event times by local seismic stations the corresponding infrasound signals were found in the data recorded by local infrasound sensors and by distant infrasound arrays signals from the okmok eruption were detected by three international monitoring system ims arrays as far away as 4400 km signals from the kasatochi eruption were detected at greater distances up to 5200 km away by seven infrasound arrays including the ones that detected the event at okmok volcano back azimuth propagation and a simple acoustic wave propagation model in unison with known event times were used to confirm that the planar acoustic signals recorded at the arrays had originated from the eruptions the infrasound array data reflected the differences in eruption styles between okmok and kasatochi as the signals from kasatochi were of shorter duration of greater amplitude and detected over greater distances the infrasound array data were also able to distinguish between two types of tremor episodes that occurred at kasatochi volcano based on atmospheric disturbance

a new way to detect volcanic plumes 1 detection of volcanic plumes especially ash laden ones is important both for public health and aircraft safety a variety of geophysical tools and satellite data are used to monitor volcanic eruptions and to predict the movement of ash however satellite based methods are restricted by time of day and weather while radars are often unavailable because of cost portability here a method is proposed to detect volcanic plumes using gps signal strength data the strengths and limitations of the method are assessed using gps data collected during the 2008 and 2009 eruptions of the okmok and mt redoubt volcanoes plume detections using this gps technique are consistent with independently collected seismic and radar data

global morphology of infrasound propagation i atmospheric sound waves in the 0 02 10 hz region also known as infrasound exhibit long range global propagation characteristics measurable infrasound is produced around the globe on a daily basis by a variety of natural and man made sources as a result of weak classical attenuation 0 01 db km 1 at 0 1 hz these acoustic signals can propagate thousands of kilometers in tropospheric stratospheric and lower thermospheric ducts to model this propagation accurately detailed knowledge of the background atmospheric state variables the global winds and temperature fields from the ground to 170 km is required for infrasound propagation calculations we have developed a unique atmospheric specification system g2s that is capable of providing this information using acoustic ray tracing methods and detailed g2s atmospheric specifications we investigate the major aspects of the spatiotemporal variability of infrasound propagation characteristics

deep water mass geometry in the glacial atlantic ocean a review of constraints from the paleonutrient proxy cd ca 1 paleonutrient proxies currently provide the strongest constraints on the past spatial distribution of deep water masses we review the state of knowledge derived from the trace metal proxy cd ca for the atlantic ocean during the last glacial maximum lgm we compile published benthic foraminiferal cd ca data supplemented with new data to reconstruct meridional cd sections through the holocene and lgm atlantic holocene cd ca reflects the modern water masses north atlantic deep water nadw antarctic bottom water aabw and antarctic intermediate water aaiw reasonably well except for anomalously high values in the intermediate to mid depth far north atlantic lgm cd ca clearly shows that nadw was replaced by the shallower glacial north atlantic intermediate water gnaiw with significant northward expansion of aabw the boundary level between gnaiw and aabw was very abrupt occurring between 2200 and 2500 m modern water depth combined cd ca and cibicidoides d 13 c data allow us to also calculate the air sea signature of d 13 c d 13 cas the lgm atlantic can be explained entirely by mixing between high d 13 cas gnaiwand low d 13 cas aabw negative d 13 cas values in glacial aabw were likely caused by poor ventilation during formation probably associated with extensive sea ice coverage overall our knowledge base would benefit from improved data coverage in the south atlantic and southern ocean and a better understanding of ancillary effects on the cd ca proxy itself

application of an updated atmospheric model to explore volcano infrasound propagation and detection in alaska abstract winds and temperature gradients greatly affect the long range propagation of infrasound the spatio temporal variability of these parameters must therefore be accurately characterized to correctly interpret recorded infrasound at long distances specifically to differentiate between source and propagation effects here we present the first results of an open source reanalysis model termed alaska volcano observatory ground to space avo g2s constructed to accurately characterize the atmosphere and model long range infrasound propagation from volcanic eruptions in alaska we select a number of case studies to examine recent eruptions of alaskan volcanoes whose ash emissions posed a threat to air traffic including the two most recent eruptions of pavlof volcano and two typical explosions from cleveland volcano strong tropospheric ducting and low noise at the station during the 21 july 2015 explosion of cleveland volcano led to an automated detection of the explosion at an infrasound array 992 km away whereas low signal to noise ratio for the 6 november 2014 cleveland volcano explosion helps explain the non detection in real time of a predicted strong stratospheric arrival for the november 2014 pavlof eruption discrepancies between local seismic data and a distal infrasound array 460 km away cannot be solely explained by changes in atmospheric conditions though some features of the complex propagation predictions follow the trends in long range infrasound signals the most recent eruption of pavlof volcano in march 2016 shows minimal changes in propagation conditions throughout the eruption and therefore indicates that the signals detected at long range primarily reflect source processes these results show how detailed examination of the acoustic propagation conditions provides insight into detection capability and eruption dynamics future work will implement avo g2s and high resolution long range infrasound propagation modeling in real time for alaskan volcanoes of interest

glacial water mass geometry and the distribution of δ13c of σco2 in the western atlantic ocean 1 oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa cibicidoides and planulina from 25 new piston cores gravity cores and multicores from the brazil margin the cores span water depths from about 400 to 3000 m and intersect the major water masses in this region these new data fill a critical gap in the south atlantic ocean and provide the motivation for updating the classic glacial western atlantic 13c transect of duplessy et al 1988 the distribution of 13c of co2 requires the presence of three distinct water masses in the glacial atlantic ocean a shallow 1000 m southern source water mass with an end member 13c value of about 0 3 0 5 vpdb a middepth 1500 m northern source water mass with an end member value of about 1 5 and a deep 2000 m southern source water with an end member value of less than 0 2 and perhaps as low as the 0 9 values observed in the south atlantic sector of the southern ocean ninnemann and charles 2002 the origins of the water masses are supported by the meridional gradients in benthic foraminiferal 18o a revised glacial section of deep water 13c documents the positions and gradients among these end member intermediate and deep water masses the large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

infrasound generated by the 2016 2017 shallow submarine eruption of bogoslof volcano alaska the 2016 2017 shallow submarine eruption of bogoslof volcano produced numerous infrasound signals over 9 months that were recorded on six alaska volcano observatory avo arrays at ranges of 59 to over 800 km from the volcano the lack of geophysical monitoring near bogoslof and the repeated production of volcanic clouds to flight levels made monitoring by remote infrasound critical during the eruption for the first time avo relied extensively on automated infrasound detections from regional arrays to dispatch timely notifications of the ongoing activity most of the 70 eruptive events were detected on at least one array but no array detected all of the events mainly because atmospheric conditions were highly variable during the eruption acoustic propagation modeling helps explain some of the variation in array detections but also highlights limitations in regional propagation models to our knowledge this is the first example of well recorded infrasound from an explosive eruption occurring in shallow seawater providing extensive insights into eruption dynamics in this unique environment the dominance of low frequency infrasound 0 1 1 hz is attributed to eruptions occurring beneath tens of meters of seawater higher frequency infrasound signals were mostly limited to eruptions where the vent was isolated from major interaction with seawater or in several cases where a lava dome grew above sea level

on the use of remote infrasound and seismic stations to constrain the eruptive sequence and intensity for the 2014 kelud eruption the february 2014 eruption of kelud volcano indonesia destroyed most of the instruments near it we use remote seismic and infrasound sensors to reconstruct the eruptive sequence the first explosions were relatively weak seismic and infrasound events a major stratospheric ash injection occurred a few minutes later and produced long lasting atmospheric and ground coupled acoustic waves that were detected as far as 11 000 km by infrasound sensors and up to 2300 km away on seismometers a seismic event followed similar to 12 minutes later and was recorded 7000 km away by seismometers we estimate a volcanic intensity around 10 9 placing the 2014 kelud eruption between the 1980 mount st helens and 1991 pinatubo eruptions intensities we demonstrate how remote infrasound and seismic sensors are critical for the early detection of volcanic explosions and how they can help to constrain and understand eruptive sequences

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

evidence of atmospheric gravity waves during the 2008 eruption of okmok volcano from seismic and remote sensing observations 1 okmok volcano erupted on july 12 2008 following an 11 year hiatus detailed inspection of the syn eruptive seismograms revealed the presence of an ultra long period mode at a frequency of 1 7 mhz which is not a characteristic of the background seismic noise at okmok data collected by the national oceanic and atmospheric administration geostationary operational environmental satellite goes and national aeronautical and space administration moderate resolution imaging spectroradiometer modis sensors displayed the propagation of a vigorous ash and steam plume up to about 17 km above sea level we suggest that the observed ultra long period signals represent the response of the seismometer to changes in gravity associated with buoyancy oscillations set off in the lower atmosphere above okmok by the emplacement of the eruption column calculations based on simple modeling of these effects allowed estimation of peak atmospheric pressure perturbations associated with the eruption of less than 1 mbar

relationship between infrasound derived and buoyancy derived eruption plume volume estimates volume estimations for discrete plumes accompanying short lived eruptions are potentially possible using infrasound signals plumes emitted during short lived discrete eruptions have been modeled as discrete thermals or rooted thermals based on the one dimensional model for the rise of a discrete thermal the initial buoyancy f0 of a spherical thermal can theoretically be estimated from the maximum plume height and a vertical profile of ambient air density we here examine the relationship between infrasound derived volume vinf and the buoyancy derived volume vb as derived from f0 which depends on gravity acceleration and the difference in density between the thermal and surrounding air to understand how vinf relates to the dynamics of the eruption plume we analyze infrasound data accompanying vulcanian and phreatic eruptions at aso shinmoedake and lokon empung volcanoes to estimate vinf and consider vinf from other volcanoes we obtain a representative ratio of vb vinf of 16 by examining 53 events because the analyzed infrasound signals share a prominent pressure pulse at the onset we regard vinf as the volume of the plume at initiation i e as a jet instead we consider vb as the thermal volume when it has entrained a sufficient amount of the surrounding air and obtains f0 comparison of the bulk density of the jet and the discrete thermal yields a rate of volume change between both regimes by a factor of 1 8 32 which is consistent with the ratio of vb vinf our result provides an effective index to constrain erupted plume volume using infrasound data with real time monitoring systems

observation of infrasonic and gravity waves at soufriere hills volcano montserrat 1 the sudden ejection of material during an explosive eruption generates a broad spectrum of pressure oscillations from infrasonic to gravity waves an infrasonic array installed at 3 5 km from the soufriere hills volcano has successfully detected and located in real time the infrasound generated by several pyroclastic flows pf estimating mean flow speeds of 30 75 m s on july 29 and december 3 2008 two differential pressure transducers co located with the array recorded ultra long period ulp oscillations at frequencies of 0 97 and 3 5 mhz typical of atmospheric gravity waves associated with explosive eruptions the observation of gravity waves in the near field 6 km at frequencies as low as about 1 mhz is unprecedented during volcanic eruptions

evaluation of redoubt volcano s sulfur dioxide emissions by the ozone monitoring instrument abstract the 2009 eruption of redoubt volcano alaska provided a rare opportunity to compare satellite measurements of sulfur dioxide so2 by the ozone monitoring instrument omi with airborne so2 measurements by the alaska volcano observatory avo herein we 1 compare omi and airborne so2 column density values for redoubt s tropospheric plume 2 calculate daily so2 masses from mount redoubt for the first three months of the eruption 3 develop simple methods to convert daily measured so2 masses into emission rates to allow satellite data to be directly integrated with the airborne so2 emissions dataset 4 calculate cumulative so2 emissions from the eruption and 5 evaluate omi as a monitoring tool for high latitude degassing volcanoes a linear correlation r2 0 75 is observed between omi and airborne so2 column densities omi daily so2 masses for the sample period ranged from 60 1 kt on 24 march to below detection limit with an average daily so2 mass of 6 7 kt the highest so2 emissions were observed during the initial part of the explosive phase and the emissions exhibited an overall decreasing trend with time omi so2 emission rates were derived using three methods and compared to airborne measurements this comparison yields a linear correlation r2 0 82 with omi derived emission rates consistently lower than airborne measurements the comparison results suggest that omi s detection limit for high latitude springtime conditions varies from 2000 to 4000 t d cumulative so2 masses calculated from daily omi data for the sample period are estimated to range from 542 to 615 kt with approximately half of this so2 produced during the explosive phase of the eruption these cumulative masses are similar in magnitude to those estimated for the 1989 90 redoubt eruption strong correlations between daily omi so2 mass and both tephra mass and acoustic energy during the explosive phase of the eruption suggest that omi data may be used to infer relative eruption size and explosivity further when used in conjunction with complementary datasets omi daily so2 masses may be used to help distinguish explosive from effusive activity and identify changes in lava extrusion rates the results of this study suggest that omi is a useful volcano monitoring tool to complement airborne measurements capture explosive so2 emissions and provide high temporal resolution so2 emissions data that can be used with interdisciplinary datasets to illuminate volcanic processes

doppler weather radar observations of the 2009 eruption of redoubt volcano alaska abstract the u s geological survey usgs deployed a transportable doppler c band radar during the precursory stage of the 2009 eruption of redoubt volcano alaska that provided valuable information during subsequent explosive events we describe the capabilities of this new monitoring tool and present data captured during the redoubt eruption the minimax 250 c mm 250c radar detected seventeen of the nineteen largest explosive events between march 23 and april 4 2009 sixteen of these events reached the stratosphere above 10 km within 2 5 min of explosion onset high column and proximal cloud reflectivity values 50 to 60 dbz were observed from many of these events and were likely due to the formation of mm sized accretionary tephra ice pellets reflectivity data suggest that these pellets formed within the first few minutes of explosion onset rapid sedimentation of the mm sized pellets was observed as a decrease in maximum detection cloud height the volcanic cloud from the april 4 explosive event showed lower reflectivity values due to finer particle sizes related to dome collapse and related pyroclastic flows and lack of significant pellet formation eruption durations determined by the radar were within a factor of two compared to seismic and pressure sensor derived estimates and were not well correlated ash dispersion observed by the radar was primarily in the upper troposphere below 10 km but satellite observations indicate the presence of volcanogenic clouds in the stratosphere this study suggests that radar is a valuable complement to traditional seismic and satellite monitoring of explosive eruptions

duration amplitude relationships of volcanic tremor and earthquake swarms preceding and during the 2009 eruption of redoubt volcano alaska abstract duration amplitude relationships were studied for tremor episodes and earthquake swarms occurring during the 2009 eruption of redoubt volcano alaska duration amplitude distribution plots were generated daily from january 1 to may 31 and fit with both an exponential law and power law comparing r2 values of the fit for both laws showed that the exponential law fit better for days in which volcanic tremor and earthquake swarms occurred while the power law fit better for other days fitting segments of seismic data with both an exponential and a power law leads to a metric that has potential for volcano monitoring r2exp r2pow the ratio of the r2 fits using the exponential law and the power law the ratio r2exp r2pow tended to be greater than 1 when volcanic activity or precursory seismic activity was occurring and less than 1 when no volcano seismic activity was occurring duration amplitude plots were generated for episodes of volcanic tremor that were identified by the r2exp r2pow 1 method and compared in an attempt to identify changes that may have occurred during the eruption stronger episodes of volcanic tremor showed higher characteristic amplitudes maximum heights of the plumes generated by the explosions showed a positive correlation with the characteristic amplitude of the concurrent tremor

last glacial maximum paleochemistry and deepwater circulation in the southern ocean evidence from foraminiferal cadmium south atlantic benthic foraminiferal cd ca shows no glacial interglacial variation suggesting that the glacial contribution of north atlantic deep water to the southern ocean was not much different than at present in contrast cd ca in southeast indian ridge cores show lower glacial bottom water cd comparable to levels in intermediate depths of the north atlantic and significantly lower than in the deep south atlantic low glacial cd ca was also recorded in planktonic foraminifera suggesting a substantial decrease in the nutrient concentration of subantarctic surface water during the glacial maximum which most likely was caused by increased biological productivity the cd data are inconsistent with low glacial benthic foraminiferal 13c which suggest higher nutrient concentration we propose that the low cd ca in the southeast indian ridge records reflects a local source of nutrient depleted deepwater formed during the last glacial maximum by open ocean convection near the antarctic polar front downstream of the kerguelene plateau if this source was limited to the southeast indian basin then its impact on the overall chemistry of glacial circumpolar deepwater was rather small however if during glaciations open ocean convection became the dominant mode of bottom water formation it might have had a greater impact on cpdw chemistry

suborbital intermediate water variability inferred from paired benthic foraminiferal cd ca and δ13c in the tropical west atlantic and linking with north atlantic climates abstract paired benthic cd ca and 13c records have been generated along core m35003 in the western tropical atlantic decreased glacial water column dissolved cadmium cdw and increased benthic 13c indicate enhanced ventilation with nutrient deplete intermediate waters in line with similar inferences from other north atlantic mid depth records an abrupt early deglacial 13c collapse that is associated with a marked positive cdw anomaly indicates a transient collapse of mid depth ventilation from north atlantic sources conceivably in conjunction with the h1 meltwater anomaly the cdw record displays fine scale fluctuations that mimic the greenland dansgaard oeschger d o cycles and show decreased cdw during stadials this pattern is opposite to cdw variations in a deep water record from bermuda rise that display increased cdw concentrations during stadials the divergent pattern between mid depth and deep water cdw records indicates millennial scale switches between deep and shallow convection in the glacial north atlantic at the pace of the d o climatic cycles several high amplitude anomalies occur in the cdw record that reach levels similar to those observed today in the north pacific while a substantial nutrient increase in the mid depth north atlantic cannot be ruled out during these events changes of pore water chemistry and cd p fractionation during biological uptake offer alternative scenarios to explain the peak cdw maxima

vostok ice core provides 160 000 year record of atmospheric co2 direct evidence of past atmospheric co2 changes has been extended to the past 160 000 years from the vostok ice core these changes are most notably an inherent phenomenon of change between glacial and interglacial periods besides this major 100 000 year cycle the co2 record seems to exhibit a cyclic change with a period of some 21 000 years

infrasonic jet noise from volcanic eruptions 1 the lowermost section of a vulcanian or plinian volcanic eruption column may be thought of as a momentum driven turbulent free shear jet flow we propose that large amplitude and long duration infrasonic 20 hz signals recorded at ranges of tens of kilometers during powerful eruptions at mount st helens usa and tungurahua ecuador represent a low frequency form of jet noise a preliminary test of this hypothesis is made by comparing the observed infrasonic spectra to the empirically derived similarity spectra for pure air jets although the spectral shapes are in approximate agreement the observed volcanic signals have additional complexities not present in the pure air laboratory data these features may result from multiphase flow containing solid particles and liquid droplets very high temperatures and perhaps complex crater morphology however the overall similarity between the volcanic signals and jet noise indicates that broadband infrasound measurements at volcanoes may provide a quantitative link to eruption jet dynamics and would aid substantially in the remote assessment of volcanic hazard

glacial deep water geometry south atlantic benthic foraminiferal cd ca and δ13c evidence a depth transect of cores from 1268 to 3909 m water depth in the western south atlantic are ideally situated to monitor the interocean exchange of deep water and variations in the relative strength of northern and southern sources of deep water production benthic foraminiferal cd ca and 13c data suggest that glacial north atlantic intermediate water gnaiw extended at least as far south as 28 s in the western south atlantic the core of nutrient depleted water was situated at 1500 m above and below water masses with higher nutrient concentrations when examined in conjunction with published paired cd ca and 13c from intermediate depth cores from other basins it appears that the extent of gnaiw influence on the intermediate waters of the world s oceans was less than suggested previously differentiating among possible pathways for the glacial deep ocean 3 km requires a better understanding of the controls on cd ca and 13c values of benthic foraminifera

characterization of the 2008 kasatochi and okmok eruptions using remote infrasound arrays 1 the 2008 plinian eruptions of kasatochi and okmok volcanoes were recorded by six remote international monitoring system infrasound arrays high amplitude infrasound at these stations combined with remote sensing permits insight into important volcanic source parameters such as origin times durations and source characteristics infrasound from the 7 8 august kasatochi eruption consists of three well defined eruption pulses with the first two steam rich and the last ash rich pulse 2 is the most energetic and impulsive okmok produced over 9 h of continuous infrasound on 12 13 july acoustic propagation modeling for the okmok eruption and first kasatochi pulse predict thermospheric ducting and origin times consistent with seismic and satellite observations however theoretical acoustic origin times of pulses 2 3 are predicted to occur 15 min earlier than the seismic stratospheric ducting for these later pulses provides more consistent origin times although both volcanoes ejected ash into the stratosphere 15 km kasatochi produced higher amplitude infrasound than okmok previous studies have shown sustained infrasound with frequencies 2000 km and does not seem to be appreciably affected by changes in ash content between the eruption pulses

swelling of a lava plug associated with a vulcanian eruption at sakurajima volcano japan as revealed by infrasound record case study of the eruption on january 2 2007 in order to clarify the time relation of the expansion of a gas pocket and failure of its overlying plug of lava during vulcanian eruptions infrasound records and video images of the vulcanian eruption that occurred at sakurajima volcano on january 2 2007 were analyzed with respect to their origin times weak 3 pa and slowly increasing air pressure preceded the impulsive compression phase by 0 25 0 32 s and a longer period rarefaction phase of infrasound waves was recognized at all microphone stations the velocity of the compression phase was assumed to be supersonic ca 400 m s up to 850 m above the crater bottom from other recent explosions on the other hand the propagation velocity of the preceding weak signal was regarded to be similar to the air sound velocity because the lack of impulsiveness is unlikely to be related to the main compression phase therefore the estimated origin time of the main compression phase was delayed by 0 5 0 7 s from the preceding phase the origin time of the preceding phase coincided with the onset of the isotropic expansion process of the pressurized gas pocket which was obtained by the waveform inversion of the explosion earthquake in contrast the origin time of the main impulsive phase coincided with the time when the expansion rate reached its peak this observation suggests that the volumetric increase of the gas pocket caused swelling of the surface of the crater bottom and its subsequent failure when the expansion velocity exceeded a threshold level the main impulsive compression phase radiated with a high velocity by the sudden releases of the pressurized gases the volumetric change at the source was estimated to be 280 560 m3 from the preceding phase of the infrasound this volume change indicates that the vertical displacement of the swelling ground was on the order of 1 0 m assuming the radius of the lava plug was ca 10 m

deep water variability on the southern agulhas plateau interhemispheric links over the past 170 ka sortable silt mean grain sizes together with oxygen and carbon isotopic data produced on the benthic foraminiferal species fontbotia wuellerstorfi are used to construct high resolution records of near bottom flow vigour and deep water ventilation at a core site md02 2589 located at 2660 m water depth on the southern agulhas plateau the results suggest that during glacial periods marine oxygen isotope stages 2 and 6 mis 2 and mis 6 respectively there was a persistent contribution of a well ventilated water mass within the atlantic to indian oceanic gateway with a 13c signature similar to present day northern component water ncw e g north atlantic deep water nadw the records of chemical ventilation and near bottom flow vigor reflect changes in the advection of northern source waters and meridional variability in the location of the antarctic circumpolar current and its associated fronts we suggest that during termination ii tii changes in chemical ventilation are largely decoupled from near bottom physical flow speeds a mid tii climate optimum is associated with a low flow speed plateau concurrent with a period of increased ventilation shown in the benthic 13c of other southern ocean records but not in our benthic 13c of md02 2589 the climate optimum is followed by a period of southern cooling around 128 ka coincident with a stronger influence of ncw to interglacial levels at around 124 ka all proxy records show a near synchronous and rapid shift during the transition from mis 5a 4 73 ka this large event is attributed to a rapid decrease in nadw influence and replacement over the agulhas plateau by southern source waters

changes to the turbulent kinematics of a volcanic plume inferred from lightning data the 2009 redoubt volcano eruption produced a series of explosive events the largest of which produced episodes of volcanic lightning similar to thunderstorms flash energy spectra were calculated from lightning mapping data collected during the eruption the spectra were compared to the turbulence characteristics expected from each stage of plume development small flash length scales present at early times were associated with the gas thrust and initial convective stages increases in flash length scales and flash energy as the explosive events progressed were associated with an increase in volume of the plume spectra with a large range in flash length scales 0 2 10 km and a spectral peak at small flash length scales 1 km were associated with a superposition of spectra from gas thrust convective and umbrella ash cloud regions an approximate 5 3 power law slope was observed on the order of 10 min after gas thrust forcing had ended and the transition to a drifting ash cloud was underway which may reflect the dissipating state of the drifting ash cloud

infrasound from tungurahua volcano 2006 2008 strombolian to plinian eruptive activity abstract strombolian to plinian activity from tungurahua volcano ecuador has been recorded by the autonomous infrasound arrays of the acoustic surveillance for hazardous eruptions ashe project since early 2006 our studies suggest that acoustic energy release during large eruptions does appear to broadly scale with eruption intensity this manuscript provides a detailed chronology and characterization of tungurahua s eruptive activity between 2006 and 2008 and demonstrates the ability to constrain source parameters of significant eruptions such as onset duration and escalation at regional distances by combining infrasound and remote sensing techniques the ashe system in ecuador automatically detected over 20 000 volcanic explosions at an array 37 km from tungurahua and was successful at notifying the onset escalation and cessation of a hazardous february 2008 eruption with a latency of 5 min elevated infrasonic energy from sustained and intense tungurahua eruptions correlates well with ash column heights and their lateral extent during the study period the spectra of these sustained explosive eruptions appear to be recurrent readily recognizable and indicative of volcanic jetting and significant atmospheric ash injection the paroxysmal plinian phase of the august 2006 eruption produced an ash cloud that extended well into the stratosphere 24 km coinciding with a shift of the dominant jetting frequency from 0 25 hz to below 0 1 hz and radiation of over 5 107 w of acoustic power transient explosions were often marked by minor or no ash release and are presumed to be more gas rich a change in the acoustic spectrum of volcanic jetting was also detected in the transition from a sustained to collapsed eruption column at the end of the july 14 2006 eruption the jetting spectrum at tungurahua during a period of sustained pyroclastic density current production changes from a typical double peaked to a single peaked spectrum suggesting remote acoustic monitoring can help ascertain the stability and dynamics of an eruptive column

emplacement of the final lava dome of the 2009 eruption of redoubt volcano alaska abstract after more than 8 months of precursory activity and over 20 explosions in 12 days redoubt volcano alaska began to extrude the fourth and final lava dome of the 2009 eruption on april 4 by july 1 the dome had filled the pre 2009 summit crater and ceased to grow by means of analysis and annotations of time lapse webcam imagery oblique image photogrammetry techniques and capture and analysis of forward looking infrared flir images we tracked the volume textural effusive style and temperature changes in near real time over the entire growth period of the dome the first month of growth april 4 may 4 produced blocky intermediate to high silica andesite lava 59 62 3 wt sio 2 that initially formed a round dome expanding by endogenous growth breaking the surface crust in radial fractures and annealing them with warmer fresh lava on or around may 1 more finely fragmented and scoriaceous andesite lava 59 8 62 2 wt sio 2 began to appear at the top of the dome coincident with increased seismicity and gas emissions the more scoriaceous lava spread radially over the dome surface while the dome continued to expand from endogenous growth and blocky lava was exposed on the margins and south side of the dome by mid june the upper scoriaceous lava had covered 36 of the dome surface area vesicularity of the upper scoriaceous lava range from 55 to 66 some of the highest vesicularity measurements recorded from a lava dome we suggest that the stability of the final lava dome primarily resulted from sufficient fracturing and clearing of the conduit by preceding explosions that allowed efficient degassing of the magma during effusion the dome was thus able to grow until it was large enough to exceed the magmastatic pressure in the chamber effectively shutting off the eruption

volcanic eruption volume flux estimations from very long period infrasound signals we examine very long period infrasonic signals accompanying volcanic eruptions near active vents at lokon empung volcano in indonesia aso kuchinoerabujima and kirishima volcanoes in japan the excitation of the very long period pulse is associated with an explosion the emerging of an eruption column and a pyroclastic density current we model the excitation of the infrasound pulse assuming a monopole source to quantify the volume flux and cumulative volume of erupting material the infrasound derived volume flux and cumulative volume can be less than half of the video derived results a largely positive correlation can be seen between the infrasound derived volume flux and the maximum eruption column height therefore our result suggests that the analysis of very long period volcanic infrasound pulses can be helpful in estimating the maximum eruption column height

the δ13c in benthic foraminiferal tests of fontbotia wuellerstorfi schwager relative to the δ13c of dissolved inorganic carbon in southern ocean deep water implications for glacial ocean circulation models on a transect between 20 and 70 s in the eastern atlantic ocean and weddell sea water samples from 19 hydrographic stations and bottom water from 55 surface sediment samples taken with a multiple corer were investigated for the stable carbon isotopic composition of the total dissolved inorganic carbon 13c co2 these measurements were compared to 13c values determined on live specimens of the benthic foraminifer fontbotia wuellerstorfi and closely related genera from the same stations in addition at 16 stations the stable carbon isotope composition of sedimentary organic carbon was measured general deepwater and bottom water mass circulation patterns as inferred from the 13c co2 are in close agreement with those known from other nonconservative tracers very low 13c values of upper circumpolar deep water 0 3 pee dee belemnite pdb in the polar front region and the eastern limb of the weddell gyre coincide with nutrient maxima however a significant decoupling of the dissolved phosphate signal from the 13c co2 signal is indicated in the abyssal weddell sea we attribute this to temperature dependent fractionation processes during gas exchange of surface waters with the atmosphere at sites of bottom water formation multiple corer water from the sediment water interface is slightly 13c depleted relative to deepwater and bottom water 13 co2 the surface sediment organic carbon 13c is 3 to 4 lower south of the polar front than north of it and the 13corg in freshly accumulated phytodetritus is 3 to 4 lower than surface sediment organic carbon 13c comparison of live f wuellerstorfi 13c and related genera with bottom water 13c co2 exhibits at most stations between the subtropical front 41 s and the southern boundary of the antarctic circumpolar current 55 s a significant lowering of foraminiferal 13c values compilation of a mean last glacial interglacial 13c amplitude 13c from six published southern ocean cores results in a shift of 0 99 0 13 pdb this shift is greater than that in all other regions however all of these cores are from positions close to recent oceanic fronts thus for these peripheral areas of the southern ocean we suggest about half of the glacial interglacial shift can be explained by varying frontal zone positions and widths accompanied by a change in mode and height of export production

the seismicity of the 2009 redoubt eruption article redoubt volcano erupted in march 2009 following 6 months of precursory seismic activity the 4 5 month long eruptive sequence was accompanied by phreatic and magmatic explosions periods of steady dome growth lahars seismic swarms extended episodes of volcanic tremor and changes in the background seismicity rate this study presents a seismic chronology of the eruption and places it in context with the variety of other geological and geophysical data that were recorded during the eruptive period we highlight 6 notable seismic swarms 3 of which preceded large explosions the swarms varied from an hour to several days in duration and contained tens to over 7000 earthquakes many of the swarms were dominated by low frequency type earthquakes that contained families of repeating events seismic tremor varied considerably in frequency amplitude and duration during the eruption with distinct characteristics accompanying different types of volcanic activity the explosion signals during march 23 24 were the most energetic and the explosions on march 26 29 contained proportionally more low frequency energy 0 033 0 3 hz two seismic stations were particularly well suited to recording lahars that flowed down the drift river valley data from these stations showed that lahars were generated by the majority of the explosion events as well as during the continuous eruptive activity on march 29 when no large explosions occurred we also examine the seismicity which occurred outside of the explosion and swarm episodes and find several families of repeating vt earthquakes which begin shortly before the april 4 explosion and that continue

benthic isotope evidence for changes of the mediterranean outflow during the late quaternary a suit of sediment cores close to and south of the strait of gibraltar 12 36 n 500 2800 m water depth were analyzed for stable isotopes in epibenthic foraminifers cibicidoides wuellerstorfi and planulina ariminensis during peak glacial times the data exhibit higher 13c values of up to 1 6 at intermediate depths near the strait of gibraltar 36 n the values decrease to the south as evidenced by our data but also to the north as revealed by data of intermediate depth cores north of 38 n in duplessy et al 1987 thus the distribution pattern of 13c provides crucial evidence for an increased influence of nutrient depleted mediterranean outflow water mow on the glacial northeast atlantic hydrography during oxygen isotope terminations i and ii the meridional carbon isotope gradient indicates a significantly decreased but still active mow as deduced from the 18o fluctuations the temperatures of the mow in the atlantic were lower during glacial times by as much as 5 c during glacial times and during termination i the maximum 13c values of the mow correlate with minimum values of the north atlantic deep water nadw and vice versa this inverse response to climatic change of the carbon isotope signals of both water masses indicates that the supply of saline mow to the north atlantic may be less important for the formation of nadw than previously assumed

seismic observations of redoubt volcano alaska 1989 2010 and a conceptual model of the redoubt magmatic system abstract seismic activity at redoubt volcano alaska has been closely monitored since 1989 by a network of five to ten seismometers within 22 km of the volcano s summit major eruptions occurred in 1989 1990 and 2009 and were characterized by large volcanic explosions episodes of lava dome growth and failure pyroclastic flows and lahars seismic features of the 1989 1990 eruption were 1 weak precursory tremor and a short 23 hour long intense swarm of repetitive shallow long period lp events centered 1 4 km below the crater floor 2 shallow volcano tectonic vt and hybrid earthquakes that separated early episodes of dome growth 3 13 additional swarms of lp events at shallow depths precursory to many of the 25 explosions that occurred over the more than 128 day duration of eruptive activity and 4 a persistent cluster of vt earthquakes at 6 to 9 km depth in contrast the 2009 eruption was preceded by a pronounced increase in deep lp dlp events at lower crustal depths 25 to 38 km that began in mid december 2008 two months of discontinuous shallow volcanic tremor that started on january 23 2009 a strong phreatic explosion on march 15 and a 58 hour long swarm of repetitive shallow lp events the 2009 eruption consisted of at least 23 major explosions between march 23 and april 5 again accompanied by shallow vt earthquakes several episodes of shallow repetitive lp events and dome growth continuing until mid july increased vt earthquakes at 4 to 9 km depth began slowly in early april possibly defining a mid crustal magma source zone magmatic processes associated with the 2009 eruption seismically activated the same portions of the redoubt magmatic system as the 1989 1990 eruption although the time scales and intensity vary considerably among the two eruptions the occurrence of precursory dlp events suggests that the 2009 eruption may have involved the rise of magma from lower crustal depths based on the evolution of seismicity during the 1989 1990 and 2009 eruptions the redoubt magmatic system is envisioned to consist of a shallow system of cracks extending 1 to 2 km below the crater floor a magma storage or source region at roughly 3 to 9 km depth and a diffuse magma source region at 25 to 38 km depth close tracking of seismic activity allowed the alaska volcano observatory to successfully issue warnings prior to many of the hazardous explosive events that occurred in 2009