propagation of the great salinity anomaly of the 1990s around the northern north atlantic 1 time series of t and s extending through 2001 are used to describe propagation of the great salinity anomaly of the 1990s gsa 90s comparison of the distance time relations for the gsa 70s 80s and 90s reveals a substantial intensification of the large scale circulation in the northern north atlantic especially in the subarctic gyre between newfoundland and the faroes the advection rate of the gsa 70s 80s and 90s between newfoundland and the faroe shetland channel is conservatively estimated to have been 3 5 10 and 10 cm s respectively the circulation intensification apparently occurred within a decade between the gsa 70s and 80s during the next decade the advection rate increased from 10 to 13 cm s between newfoundland and iceland basin the gsa 90s was advected towards the faroe shetland channel by the northern iceland basin s branch of the north atlantic current whereas the contribution of the southern branch via the rockall trough was minimal

on the origin of the warm inflow to the nordic seas abstract warm and saline waters enter the nordic seas from the south as part of the warm to cold water transformation of the thermohaline circulation of the northern north atlantic one explanation for the origin of the nordic seas inflow is a shallow source hypothesis under which the inflow waters are a modification of upper ocean subtropical waters warm waters from the subtropical gyre are carried to the eastern north atlantic by the north atlantic current and branch northwards joined by poleward upper thermocline flow along the upper continental slope to provide the nordic seas inflow along this pathway the upper water column is progressively cooled and freshened by winter convection the subpolar mode water transformation process and this sets the inflow characteristics a deep source hypothesis provides an alternative explanation for the characteristics of the nordic seas inflow and the pathway delivering the waters to the inflow under this hypothesis inflow waters originate from the core of the mediterranean overflow waters in the gulf of cadiz carried northward at mid depth by the eastern boundary undercurrent in the subtropics continuing into the subpolar gyre along the eastern boundary and rising from depths near 1200m in the rockall trough to less than 600m to cross the wyville thomson ridge into the faroe shetland channel and thence to the nordic seas the deep source hypothesis focus is on lower thermocline source waters beneath the sill depth for the nordic seas inflow in contrast to the shallow source hypothesis focus of transformation of upper thermocline waters above the sill depth on the basis of regional water mass distributions geostrophic shear and direct current measurements we reject the deep source hypothesis in favor of the shallow source hypothesis rather than a flow of deep mediterranean overflow water along the eastern boundary rising from depth to feed the nordic seas the inflow is supplied directly by transformed north atlantic current waters from the same depth range as the inflow mediterranean overflow water is a constituent of the inflow but only through its contribution to defining the temperature salinity relationship of the interior of the subtropical gyre from which the north atlantic current draws its water rather than by direct northward advection of mediterranean outflow water via the eastern boundary undercurrent crossing from the subtropics into the subpolar domain instead the eastern boundary undercurrent wholly expels its transport of mediterranean overflow water into the eastern edge of the subtropical gyre creating the mid depth westward extending subtropical salinity plume for the lower thermocline isopycnal range of the core of the mediterranean overflow water measurements show that at the wyville thomson ridge the flow is southward and descending rather than northward and rising representing cold spillover from the faroese channels entraining warm upper ocean waters as the spillover plume descends and warms into the northern rockall trough no evidence is found in rockall trough northward of 54 n porcupine bank for direct advection of mediterranean overflow waters via an eastern boundary undercurrent extension and the very dilute mediterranean overflow waters in the trough reflect the interaction of the wyville thomson ridge plume descending into the trough from the north and lower thermocline waters delivered to the trough from the south

heterogeneity of initial 87sr 86sr ratios within a single pluton evidence from apatite strontium isotopic study abstract magmatic apatite in samples of the unmetamorphosed undeformed cretaceous pluton of the habu granodiorite southwestern japan was examined to determine its viability as an indicator of initial 87sr 86sr heterogeneity in magmatic bodies the habu granodiorite is a zoned pluton in the ryoke metamorphic belt of southwestern japan a published rb sr whole rock isochron age of 124 2 10 8 ma is significantly older than th u total pb monazite ages of ca 86 ma a rb sr mineral isochron of 90 0 2 5 ma for a sample of granodiorite from the margin of the pluton has an initial 87sr 86sr sri of 0 7056 0 0001 similar to a 87sr 86sr of 0 70539 for coexisting euhedral apatite similarly a rb sr mineral isochron of 91 4 2 5 ma for a sample of adamellite from the center of the pluton has an sri of 0 7068 0 0001 corresponding to a 87sr 86sr ratio of 0 70673 0 70684 for three fractions of coexisting euhedral apatite the uniformity of 87sr 86sr values of apatite in individual samples and accordance of 87sr 86sr values of apatite and sri from the mineral isochron suggest that magmatic apatite can be considered as a reliable indicator of sri in granitic rocks the sr isotopic compositions of euhedral apatite coupled with those determined through the mineral isochrons and whole rock data indicate that sri varies between samples from 0 7054 to 0 7074 this provides direct evidence of sri heterogeneity within a compositionally zoned pluton such heterogeneity can produce spurious whole rock age estimates in granitic plutons even where the true age of a pluton is uniform within measurable error assimilation cannot account for chemical differences between granodiorite and adamellite as well as sr isotopic heterogeneity it is likely that the heterogeneity of sri is caused by magma source materials

observational evidences of walker circulation change over the last 30 years contrasting with gcm results in order to examine the changes in walker circulation over the recent decades we analyzed the sea surface temperature sst deep convective activities upper tropospheric moistening sea level pressure slp and effective wind in the boundary layer over the 30 year period of 1979 2008 the analysis showed that the eastern tropical pacific has undergone cooling while the western pacific has undergone warming over the past three decades causing an increase in the east west sst gradient it is indicated that the tropical atmosphere should have responded to these sst changes increased deep convective activities and associated upper tropospheric moistening over the western pacific ascending region increased slp over the eastern pacific descending region in contrast to decreased slp over the western pacific ascending region and enhanced easterly wind in the boundary layer in response to the slp change these variations recognized from different data sets occur in tandem with each other strongly supporting the intensified walker circulation over the tropical pacific ocean since the sst trend was attributed to more frequent occurrences of central pacific type el nino in recent decades it is suggested that the decadal variation of el nino caused the intensified walker circulation over the past 30 years an analysis of current climate models shows that model results deviate greatly from the observed intensified walker circulation the uncertainties in the current climate models may be due to the natural variability dominating the forced signal over the tropical pacific during the last three decades in the twentieth century climate scenario runs by cmip3 cgcms

detection and attribution of atlantic salinity changes 1 an analysis of observed and modeled oceanic salinity changes shows that significant changes of salinity which are predicted in the world s oceans as a result of human influence are beginning to emerge a significant increase in salinity has been observed in recent decades in the 20n 50n latitude band of the atlantic ocean although changes at sub polar latitudes of the atlantic and in other ocean basins are not found to be significant compared to modeled internal variability an optimal detection analysis of spatial patterns of salinity trends detects a human influence on the observed salinity increases in the atlantic ocean these results indicate the growing potential for using observations to constrain important properties of the climate system s response to anthropogenic forcing

variations of the tropical atlantic and pacific sss minimum zones and their relations to the itcz and spcz rain bands 1979 2009 this study focuses on the time space variability of the low sea surface salinity sss waters extending zonally within 2 n 12 n in the atlantic and pacific and within 6 s 16 s in the western third of the pacific the analysis is based on a combination of in situ sss observations collected in the last three decades from voluntary observing ships tao triton and pirata moorings argo floats and few ctd profiles the mean latitudes of the atlantic and pacific low sss waters appear 1 3 further poleward than the evaporation minus precipitation e p minima linked to the inter tropical convergence zones itcz and south pacific convergence zone spcz at the seasonal time scale the e p minima migrate poleward in summer hemispheres leading the migration of the sss minima by 2 3 months in the atlantic itcz pacific spcz and in the eastern part of the pacific itcz on the other hand the seasonal displacements of e p and sss minima are in antiphase in the central and western parts of the pacific itcz at the interannual time scale the e p and sss minima migrate poleward during la nina events in the pacific and during the positive phase of the atlantic meridional dipole amd in the atlantic and vice versa during el nino and the negative phase of the amd we further document long term 1979 2009 meridional migrations of the e p and sss minima especially in the spcz region and discuss whether or not they are consistent with documented sst and wind stress trends

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

spatiotemporal variability of the south pacific convergence zone fresh pool eastern front from coral derived surface salinity data abstractdirect observations indicate a south eastward expansion of the south pacific convergence zone spcz fresh pool and a freshening trend since the 1970s understanding decadal and longer term variability of the spcz fresh pool and of the salinity front located at its southeastern margin has been limited by the scarcity of instrumental sea surface salinity sss measurements in this study we use coral 18o as a proxy for sss to extend the salinity record back to the 1880s from three different locations across the sss front fiji tonga and rarotonga ftr high percentages of observed sss variance are explained by multi coral 18o mean composite at each site at the interannual time scale the salinity front displacement over the last 200 years follows the el nino southern oscillation index enso the different el nino flavours are observable in the amplitude of the salinity front interannual displacement however we do not observe any significant changes in either the frequency or the amplitud

magmatic model for the mount st helens blast of may 18 1980 analytical and numerical solutions to the hydrodynamic equations of motion constrained by physical properties of juvenile ejecta in the mount st helens blast deposit were used to investigate magmatic conditions required to produce the initial devastating blast phase of the eruption of may 18 1980 evidence that the blast was magmatic includes equivalence in volume of juvenile blast ejecta to preemption inflation of the cone substantial vesicularity of this ejecta and continued vesiculation of large juvenile clasts after eruption observed or inferred ejecta velocities of 100 to 250 m s are shown to require 0 2 to 0 7 wt water vapor preexisting in magma unloaded by a landslide 200 to 900 m thick these conditions imply total magmatic water contents of 0 7 to 1 7 wt respectively such low required water content suggests that volcanic blasts may be regarded as a normal consequence of magma intrusion into an unstable edifice

steric sea level variations during 1957 1994 importance of salinity 1 spatially averaged 50 s 65 n temperature and salinity changes in the 0 3000 m layer during the 1957 1994 period resulted in a sea level rise at a mean rate of about 0 55 mm per year about 10 of this rate is due to a decrease of the volume mean salinity the magnitude of total steric sea level tssl changes and the ratio of thermosteric and halosteric anomalies to tssl anomaly are nonuniform geographically salinity effects are critically important to the tssl changes in some regions of the ocean for example the thermosteric anomaly is nearly compensated by the halosteric anomaly in the subpolar north atlantic this fact will cause erroneous heat content estimates based on altimetric observations from space if a climatological salinity is assumed based on the present historical archive of salinity data a decrease in global mean salinity has occurred this increase of fresh water would cause sea level rise at a rate of 1 3 0 5 mm yr if the added water comes from sources other than floating sea ice

infrasonic harmonic tremor and degassing bursts from halema uma u crater kilauea volcano hawaii 1 the formation evolution collapse and subsequent resurrection of a vent within halema uma u crater kilauea volcano produced energetic and varied degassing signals recorded by a nearby infrasound array between 2008 and early 2009 after 25 years of quiescence a vent clearing explosive burst on 19 march 2008 produced a clear complex acoustic signal near continuous harmonic infrasonic tremor followed this burst until 4 december 2008 when a period of decreased degassing occurred the tremor spectra suggest volume oscillation and reverberation of a shallow gas filled cavity beneath the vent the dominant tremor peak can be sustained through helmholtz oscillations of the cavity while the secondary tremor peak and overtones are interpreted assuming acoustic resonance the dominant tremor frequency matches the oscillation frequency of the gas emanating from the vent observed by video tremor spectra and power are also correlated with cavity geometry and dynamics with the cavity depth estimated at 219 m and volume 3 106 m3 in november 2008 over 21 varied degassing bursts were observed with extended burst durations and frequency content consistent with a transient release of gas exciting the cavity into resonance correlation of infrasound with seismicity suggests an open system connecting the atmosphere to the seismic excitation process at depth numerous degassing bursts produced very long period 0 03 0 1 hz infrasound the first recorded at kilauea indicative of long duration atmospheric accelerations kilauea infrasound appears controlled by the exsolution of gas from the magma and the interaction of this gas with the conduits and cavities confining it

a high resolution salinity time series 1993 2012 in the north atlantic from argo and altimeter data the study of salinity changes has been hampered by the lack of temporal and spatial resolution of the observations in order to improve the spatial and temporal distribution of salinity observations we used the gravest empirical mode gem technique to calculate high resolution salinity distributions as a function of dynamic height for the period 1993 2012 this technique combined argo and altimeter data to exploit the relationship between t s profiles and dynamic height in the north atlantic the method was valid in the upper 700 m mainly at and near the pathways of the north atlantic current nac but failed in regions with weak stratification or with ambiguities in the t s relationships coherent multiannual large scale variability was observed with many features present in all regions albeit with weaker amplitudes in the eastern basins some of the interannual features in the northeastern atlantic basins were unrelated to the variability further south and west pointing to an occasional advection of subtropical water in the eastern atlantic origin and advection of salinity anomalies with the nac from the north american basin into the western subpolar north atlantic are correlated with the state of the north atlantic oscillation nao and dampened by the surface freshwater fluxes other mechanisms influencing the salinity pattern are the changing location of the subpolar front also related to the nao the large multiyear variability in the 20 year time series obscured any potential trends caused by global warming only the rockall trough showed a salinity increase of 0 03 per decade

analysis of long period seismic waves excited by the may 18 1980 eruption of mount st helens a terrestrial monopole long period 100 to 260 s love and rayleigh waves excited by the eruption of mount st helens on may 18 1980 and recorded by ida sro and asro stations were analyzed to determine the mechanism of the eruption the amplitude radiation patterns of both rayleigh and love waves are two lobed with a nodal direction in e5 s for rayleigh waves and in n5 e for love waves these radiation patterns preclude any double couple mechanism the radiation pattern the initial phase the relatively large amplitude ratio of love to rayleigh waves and the existence of clear nodes in the radiation patterns of fundamental mode and higher mode rayleigh waves suggest that the source is represented by an almost horizontal less than 15 from the horizontal single force pointed toward s5 w the surface wave spectra fall off very rapidly at periods shorter than 75 s suggesting a very slow source process although the details of the source time history could not be determined a smooth bell shaped time function f o s t 1 2 f o l cos t for 0 t 2 and f o s t 0 for t 2 with 75 s is considered appropriate on the basis of comparison between synthetic and observed seismograms and of the shape of the source spectrum the peak value of the force f 0 is about 10 18 dynes the tailing end of the source time function could not be resolved and some overshoot may be added the magnitude and the time history of the force can be explained by a northward landslide followed by a lateral blast observed at the time of the eruption two distinct events about 110 s apart can be identified on body wave and short period surface wave records the first event may correspond to the earthquake which triggered the landslide and the lateral blast the second event appears to correspond to a second large earthquake and explosion which took place about 2 minutes after the first earthquake

the western mediterranean deep water a proxy for climate change reconstructions of mediterranean ocean temperature fields back to 1950 show a proxy relationship between heat content changes in the north atlantic and the western mediterranean deep water wmdw formed in the gulf of lions in winter because of consistent air sea heat fluxes over these areas strongly correlated to the north atlantic oscillation nao

on the temporally varying northward penetration of mediterranean overflow water and eastward penetration of labrador sea water abstract historical hydrographic data in the eastern north atlantic are used to suggest a connection between the northward penetration of mediterranean overflow water mow and the location of the subpolar front the latter of which is shown to vary with the north atlantic oscillation nao during persistent high nao periods when the subpolar front moves eastward waters in the subpolar gyre essentially block the northward flowing mow preventing its entry into the subpolar gyre conversely during low nao periods the subpolar front moves westward allowing mow to penetrate past porcupine bank into the subpolar gyre the impacts of an intermittent penetration of mow into the subpolar gyre including the possible effect on water mass transformations remain to be investigated

low frequency acoustic gravity waves from coseismic vertical deformation associated with the 2004 sumatra andaman earthquake mw 9 2 1 atmospheric pressure perturbations from the 2004 sumatra andaman earthquake mw 9 2 were observed by sensitive microbarographs at several global stations among these observations very low frequency acoustic gravity waves 1 4 2 8 mhz with a group velocity around 300 314 m s and amplitudes ranging between 1 and 12 pa can be clearly identified through data processing at four stations on the japanese islands and also at four international monitoring system ims stations around the indian ocean assuming several seismic source parameters for this great thrust earthquake we produce synthetic barograms using a realistic thermal structure in the atmosphere up to an altitude of 220 km for this modeling we incorporate the source dimensions in different zones the expanding velocity of the source region the vertical displacements of uplift and subsidence and their time constants combinations of these source parameters provide synthetic waveforms consistent with the general features of the observed low frequency records the results clearly indicate that the recorded waves may have been generated by large scale coseismic uplift and subsidence of the sea bottom and associated swelling and depression of the sea surface over the source region extending for 1500 km the uplift in the south central zone of the andaman nicobar regions may be substantially larger than in the other zones the time constant of the coseimic vertical deformation is found to be in the range of 1 0 1 5 min which may correspond to the time elapsed shortly before the generation of tsunami waves

was the 18 may 1980 lateral blast at mt st helens the product of two explosions the 18 may 1980 lateral blast at mt st helens has been interpreted as the product of a single explosion by some stratigraphers and as two closely spaced explosions by others the stratigraphic evidence that bears on this question is inconclusive strata change dramatically over short distances and this complexity provides wide latitude for interpretation some independent non stratigraphic evidence however suggests that the blast was the product of two explosions or clusters of explosions the independent evidence comes from eyewitness accounts and photographs from satellite sensors and from seismic records this paper reviews the pertinent evidence offers a new interpretation and concludes that the blast was indeed the product of two explosions or clusters of explosions

excitation mechanism of atmospheric pressure waves from the 1980 mount st helens eruption summary atmospheric pressure waves from the mount st helens eruption 1980 may 18 have been clearly recorded by a sensitive microbarograph at berkeley california the record shows three types of waves with different group velocities the pressure waves can be interpreted in terms of direct waves a1 antipodean travelling waves a2 and circumnavigating waves a3 all of which are composed of several acoustic gravity modes propagated in the lower atmosphere synthetic barograms appropriate to the berkeley station have been calculated on the basis of the dynamic response of the lower atmospheric structure together with various assumptions of source properties comparisons between synthetic and observed barograms provide estimates for ranges of the time history of upward particle velocity at the source source dimensions and the velocity of the source spreading over the blast zone as well as for the average dissipation effects over the circumferential path the results suggest that two major compression pulses on the a1 record correlate with the arrival of pressure waves from the first lateral blast and second vertical blast although the inferred interblast time interval is not consistent with that estimated from seismic observations

dilution of the northern north atlantic ocean in recent decades declining salinities signify that large amounts of fresh water have been added to the northern north atlantic ocean since the mid 1960s we estimate that the nordic seas and subpolar basins were diluted by an extra 19 000 5000 cubic kilometers of freshwater input between 1965 and 1995 fully half of that additional fresh water about 10 000 cubic kilometers infiltrated the system in the late 1960s at an approximate rate of 2000 cubic kilometers per year patterns of freshwater accumulation observed in the nordic seas suggest a century time scale to reach freshening thresholds critical to that portion of the atlantic meridional overturning circulation

blast dynamics at mount st helens on 18 may 1980 at 8 32 a m on 18 may 1980 failure of the upper part of the north slope of mount st helens triggered a lateral eruption the blast that devastated the conifer forests in a sector covering 500 km2 north of the volcano i present here a steady flow model for the blast dynamics and propose that through much of the devastated area the blast was a supersonic flow of a complex multiphase solid liquid vapour mixture the shape of the blast zone pressure temperature velocity mach number and density distributions within the flow positions of weak and strong internal shocks and mass flux energy flux and total energy are calculated the shape of blast zone was determined by the initial areal expansion from the reservoir by internal expansion and compression waves including shocks and by the density of the expanding mixture the pressure within the flow dropped rapidly away from the source of the blast until at a distance of 11 km the flow became underpressured relative to the surrounding atmosphere weak shocks within the flow subparallel to the east and west margins coalesced at about this distance into a strong mach disk shock across which the flow velocities would have dropped from supersonic to subsonic as the pressure rose back towards ambient the positions of the shocks may be reflected in differences in the patterns of felled trees at the limits of the devastated area the temperature had dropped only 20 from the reservoir temperature because the entrained solids thermally buffered the flow the dynamic and thermodynamic effects of the admixture of the surrounding atmosphere and the uprooted forest and soils into the flow are not considered the density of the flow decreased with distance until at the limits of the blast zone 20 25 km from the volcano the density became comparable with that of the surrounding dirty atmosphere and the flow became buoyant and ramped up into the atmosphere according to the model the mass flux per unit area at the source was 0 6 104 g s 1 cm 2 and the energy flux per unit area was 2 5 mw cm 2 from the measured total ejected mass 0 25 1015 g the total energy released during the eruption was 1024 erg or 24 megatons the model triggering of the eruption and the transition from unsteady to steady flow and applications to eyewitness observations and atmospheric effects are discussed in ref 1

strombolian explosions 2 eruption dynamics determined from acoustic measurements strombolian activity consists of a series of explosions due to the breaking of a large overpressurized bubble at the surface of the magma column acoustic pressure due to sound waves has been measured and analyzed at stromboli for more than 50 explosions three parts can be distinguished in the acoustic pressure waveform which are related to the behavior of the bubble before during and after its bursting before the sharp rise in acoustic pressure the signal is dominated by waves with a frequency of 2 hz which develop on the nose of the bubble they produce sound in air by imposing a rapid motion to the interface and one could detect a bubble travelling in the uppermost 30 m of the magma column when the bubble reaches the air magma interface its strong vibration driven by a large overpressure inside the gas generates the main event with a frequency around 9 hz after the bubble has burst kinematic waves of frequency around 4 5 hz are the main source of sound they develop at the surface of the magma left on the conduit side the three types of motion although determined independently give consistent results furthermore combining the results obtained for the two types of kinematic waves the magma viscosity is estimated to be of 300 65 pa s which is in good agreement with petrological constraints and corroborates the validity of our analysis this suggests that acoustic measurements constitute a powerful tool in the understanding of eruption dynamics

single station estimates of the seismic moment of the 1960 chilean and 1964 alaskan earthquakes using the mantle magnitudem m measurements are taken of the mantle magnitudem m developed and introduced in previous papers in the case of the 1960 chilean and 1964 alaskan earthquakes by far the largest events ever recorded instrumentally we show that them m algorithm recovers the seismic moment of these gigantic earthquakes with an accuracy typically 0 2 to 0 3 units of magnitude or a factor of 1 5 to 2 on the seismic moment comparable to that achieved on modern digital datasets in particular this study proves that the mantle magnitudem m does not saturate for large events as do standard magnitude scales but rather keeps growing with seismic moment even for the very largest earthquakes we further prove that the algorithm can be applied in unfavorable experimental conditions such as instruments with poor response at mantle periods seismograms clipped due to limited recording dynamics or even on microbarograph records of air coupled rayleigh waves

pressure wave generated by the mount st helens eruption histories of the air pressure wave radiated from the eruption of mount st helens on may 18 1980 were calculated for two models of the eruption cloud expansion the first considered the wave radiated from an accelerated plane surface while the second examined the wave radiated from an expanding hemisphere two histories of eruption cloud motion based on photographs were used peak positive overpressures were about the same for these cloud motion histories of expansion into a hemisphere was assumed if an accelerated planar source model was used the peak positive pressures have again about the same value in east and west direction but values are about half in the north and south direction observed peak overpressures at microbarograph stations are somewhat higher than the calculated with the most marked departures at the greater surface ranges these observed overpressures may have been about half the correct values however microbarograph records show a weaker rarefaction than calculated histories or none at all this can be explained in part by a lack of areal motion coherence in the slowing eruption cloud it is also possible the net ash cloud volume increased considerably after its vertical growth ceased and weakened the negative phase as well as lengthening the positive phase

geochemical mapping in aichi prefecture japan its significance as a useful dataset for geological mapping abstract since 1994 a geochemical mapping project has been undertaken in aichi prefecture central japan with the aim of establishing a database to contribute to environmental assessment in the region to date more than 1200 stream sediments have been collected and analyzed the samples were analyzed for 10 major elements by x ray fluorescence spectrometry and loss on ignition the analyses show that stream sediments from areas with sedimentary bedrock are enriched in sio 2 and mafic elements such as tio 2 and fe 2 o 3 compared to areas with granitic bedrock the sio 2 enrichment is mainly due to the amount of quartz and the enrichment in mafic elements is due to biotite both of which are derived from the sedimentary bedrock in contrast sediments derived from granitic bedrock are characterized by high abundances of elements contained in feldspars such as na 2 o and cao this contrast in elemental distribution e g na 2 o tio 2 ratio can be useful for geological mapping in the areas covered by vegetation and with poor bedrock exposure the relative abundances of ca na and k in the stream sediments suggest that the inagawa granite one of the main granite bodies in the study area can be classified into four distinct types this classification is distinct from previous classifications based on geological and petrochemical studies it is confirmed that analysis of geochemical compositions of stream sediments has considerable potential as a tool in geological studies including lithological mapping

salinity changes in the world ocean since 1950 in relation to changing surface freshwater fluxes global hydrographic and air sea freshwater flux datasets are used to investigate ocean salinity changes over 1950 2010 in relation to surface freshwater flux on multi decadal timescales surface salinity increases decreases in evaporation precipitation dominated regions the atlantic pacific salinity contrast increases and the upper thermocline salinity maximum increases while the salinity minimum of intermediate waters decreases potential trends in e p are examined for 1950 2010 using two reanalyses and 1979 2010 using four reanalyses and two blended products large differences in the 1950 2010 e p trend patterns are evident in several regions particularly the north atlantic for 1979 2010 some coherency in the spatial change patterns is evident but there is still a large spread in trend magnitude and sign between the six e p products however a robust pattern of increased e p in the southern hemisphere subtropical gyres is seen in all products there is also some evidence in the tropical pacific for a link between the spatial change patterns of salinity and e p associated with enso the water cycle amplification rate over specific regions is subsequently inferred from the observed 3 d salinity change field using a salt conservation equation in variable isopycnal volumes implicitly accounting for the migration of isopycnal surfaces inferred global changes of e p over 1950 2010 amount to an increase of 1 0 6 in net evaporation across the subtropics and an increase of 4 2 2 in net precipitation across subpolar latitudes amplification rates are approximately doubled over 1979 2010 consistent with accelerated broad scale warming but also coincident with much improved salinity sampling over the latter period

great salinity anomalies in the north atlantic abstract we revisited the great salinity anomaly of the 1970s gsa 70s dickson et al 1988 and documented the newly identified great salinity anomaly of the 1980s hence termed gsa 80s both propagated around the north atlantic in a similar fashion the advective mechanism initially proposed to explain the observed sequence of low salinity low temperature events during the gsa 70s apparently holds also for the gsa 80s the latter was successively observed in the west greenland current 1982 the labrador current 1983 the flemish pass 1984 near the charlie gibbs fracture zone 1984 1985 in the rockall channel 1985 south of iceland 1985 1988 in the north sea 1986 1987 norwegian sea 1987 1988 barents sea 1988 1989 and iceland sea 1989 1990 the advection speed of the gsa 80s seems to be greater than the one of the gsa 70s the 1980s anomaly reached the barents sea 6 to 7 years after peaking in the west greenland current while the 1970s anomaly traveled the same route in 8 to 10 years these anomalies however seem to be of different origin the gsa 70s was apparently boosted remotely by a freshwater sea ice pulse from the arctic via fram strait consequently the gsa 70s was accompanied by a large sea ice extent anomaly in the greenland and iceland seas which propagated into the labrador sea in contrast the gsa 80s was likely formed locally in the labrador sea baffin bay mainly because of the extremely severe winters of the early 1980s but supplemented with a possible contribution of the arctic freshwater outflow via the canadian archipelago facilitated by strong northerly winds which would have enhanced stability and ice formation this anomaly was also associated with a positive sea ice extent anomaly in the labrador sea baffin bay which however had no upstream precursor in the greenland sea thus the gsas are not necessarily caused solely by an increased export of freshwater and sea ice from the arctic via fram strait these results are corroborated by the early 1990s data when a new fresh cold anomaly was formed in the labrador sea and accompanied by a large positive sea ice extent anomaly the harsh winters of the early 1990s were however confined to the labrador sea baffin bay area while the atmospheric and oceanic conditions in the greenland iceland and irminger seas were normal the labrador sea baffin bay area appears therefore to play a key role in formation of gsas as well as in propagation of the gsas formed upstream a likely contribution of the enhanced canadian archipelago freshwater outflow to the gsa formation also seems to be significant two major modes of the gsa origin are thus identified remote generated by an enhanced arctic ocean freshwater export via either fram strait or the canadian archipelago and local resulting from severe winters in the labrador sea baffin bay both modes should be taken into account to model decadal variability of the coupled ocean ice atmosphere system in the north atlantic arctic basin

are great salinity anomalies advective abstract great salinity anomalies gsas have been observed to propagate around the north atlantic subpolar gyre similar anomalies occur in the third hadley centre coupled atmosphere ocean gcm hadcm3 of preindustrial climate it has been hypothesized that these salinity anomalies result from the advection of anomalously low salinity waters around the subpolar gyre here the consequences of using passive tracers in the hadcm3 climate model to tag the anomalously low salinity water associated with a gsa in the greenland and labrador seas are reported rather than predominantly advecting around the modeled subpolar gyre in accordance with the upper ocean salinity anomaly the tracers mix to intermediate depths before becoming incorporated into the model s north atlantic deep water horizontal advection of the tracer in the upper ocean is limited to around 1000 km compared with the gyre scale propagation of the salinity anomalies it is concluded that gsas are unlikely to be caused by the advection of

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

nd and sr isotopic mapping of the archaean proterozoic boundary in southeastern tanzania using granites as probes for crustal growth abstract granitoids of two different generations occur across the archaean proterozoic boundary in southeastern tanzania the first generation which is confined to the archaean tanzania craton yields rb sr whole rock isochron ages of 2600 ma and low mantle like initial 87sr 86sr ratios 0 702 0 704 these coupled with positive or near zero e nd values 0 2 to 2 0 suggest that these granitoids represent juvenile mantle material which was added to the continental crust at about 2600 ma the second generation of granitoids intrudes the palaeoproterozoic usagaran belt and is characterised by rb sr whole rock isochron ages of about 1900 ma these granitoids show sm nd crustal formation ages which are 200 to 600 ma older than their emplacement ages and negative e nd values 2 2 to 6 2 mixing calculations suggest that the proterozoic granitoids may have formed by partial melting of 2000 ma usagaran mantle derived material which had incorporated between 15 and 45 of an archaean component from the adjacent tanzania craton

chemical aspects of alteration of acidic tuffs and their application to siliceous deposits in order to evaluate fundamental chemical characteristics of acidic tuffs and to determine which of these characteristics in volcanogenic sediments is preserved during weathering processes we have analysed 41 pairs of ash samples each pair consists of 1 raw samples obtained from ash layers which consist of a mixture of volcanic glasses and clays and 2 glass shard aggregations extracted from the raw samples the migration of elements in the samples during alteration was examined using the analysed values of these pairs the results showed that certain compositional ratios of the glass shards do not basically change during alteration several diagrams showing these essentially constant ratios in acidic 65 sio2 volcanic glasses are presented these diagrams are helpful in identifying altered siliceous deposits derived from acidic tuffs and in discriminating such deposits from biogenically derived cherts

mount st helens eruption of 18 may 1980 air waves and explosive yield strong atmospheric acoustic gravity waves were recorded by sensitive microbarographs and seismographs at large distances from the mount st helens eruption of 18 may 1980 wave signatures were similar to those of waves from large nuclear explosions independent theoretical and empirical analyses indicate that the explosive yield of the eruption was approximately 35 megatons

metallogenic provinces geochemical provinces and regional geology what causes large scale patterns in low density geochemical maps of the c horizon of podzols in arctic europe the 2 mm fraction of 605 samples of the c horizon of podzols collected from an area of 188 000 km2 in the european arctic was analysed for more than 40 chemical elements the results were used to construct geochemical maps which showed clear regional distribution patterns notwithstanding the very low sample density of 1 site per 300 km2 some of these patterns fit established lithological boundaries others fit lineament structures in the area and underline the relative importance of certain tectonic directions some of which have not yet been delineated on existing geological maps some mark large scale hydrothermal events and related alteration finally some are connected with prominent known ore deposits occurring in the area however several large deposits and even famous metallogenic provinces fe ni cu are hardly or not at all reflected in the regional geochemical maps in their present definitions geochemical provinces and metallogenic provinces are thus not necessarily related special geochemical features can occur at very different scales the term geochemical province is so imprecise in terms of processes leading to regional scale geochemical features that it should be avoided low density geochemistry can be used to aid the interpretation of the geological evolution of large regions it can also be used to find prospective areas within such regions

ocean gyre circulation changes associated with the north atlantic oscillation abstract observational evidence is presented for interannual to interdecadal variability in the intensity of the north atlantic gyre circulation related to the atmospheric north atlantic oscillation nao patterns a two point baroclinic pressure difference between the subtropical and subpolar gyre centers an oceanic analogue to the much used sea level pressure slp based atmospheric nao indices is constructed from time series of potential energy anomaly pea derived from hydrographic measurements in the labrador basin and at station s near bermuda representing the upper 2000 db eastward baroclinic mass transport between the two centers the transport index indicates a gulf stream and north atlantic current that gradually weakened during the low nao period of the 1960s and then intensified in the subsequent 25 years of persistently high nao to a record peak in the 1990s the peak to peak amplitude difference was 15 20 megatons per second mt s 1 with a 43 yr mean of about 60 mt s 1 a change of 25 33

application of sr isotopes to geochemical mapping and provenance analysis the case of aichi prefecture central japan abstract geochemical maps expressing areal distributions of chemical elements in the earth s land surface have been published in several countries in relation to various global environment issues the authors have applied a radiogenic isotope ratio 87 sr 86 sr to geochemical mapping in order to understand the geological origin transportation and dispersion system of chemical elements in the earth s land surface the sr isotope ratio is a useful tracer for distinguishing the geological origin of surficial deposits especially in areas where surface exposure of bedrocks is low because it is not significantly altered by the processes of weathering and transportation most bedrocks in the japanese islands are covered by plants soils and urban areas in this study 142 of 1219 stream sediments 87 sr 86 sr values and the above average presence of granitic rocks in the study area compared with the surface exposure of the japan arc the first factor controlling the distribution of sr isotope ratios is the bedrock distributed around the sampling points regional variation in the 87 sr 86 sr value shows that it is higher in the western and southeastern parts where sedimentary rocks and metamorphic rocks are distributed and that it is lower mainly in the central part where granitic rocks are distributed the 87 rb 86 sr 87 sr 86 sr plot for stream sediments more clearly reveals the differences and similarities of bedrocks in some locations the distribution of sr isotope ratios does not correspond to that of bedrocks on the geological map one reason is the existence of unmapped bedrock for example small intrusive masses of granite the other is fluvial transportation and dispersion the distribution of the isotope ratios suggests that some stream sediments include surficial deposits from a few km upstream application of the sr isotope ratio to geochemical mapping is useful for revealing both the distribution of unexposed bedrocks and the transportation of surficial deposits information on unexposed bedrocks will be expected to contribute to the improvement of geological mapping

analysis of seismic body waves excited by the mount st helens eruption of may 18 1980 seismic body waves which were excited by the may 18 1980 eruption of mount st helens and recorded by the global digital seismographic network stations are analyzed to determine the nature and the time sequence of the events associated with the eruption the polarity of teleseismic p waves period 20s is identical at six stations which are distributed over a wide azimuthal range this observation together with a very small s to p amplitude ratio at 20 s suggests that the source is a nearly vertical single force a simple model shows that for seismic radiation a volcanic eruption can be represented by a single force applied in the direction opposite to the blast direction the time history of the vertical force suggests two distinct groups of events about 2 min apart each consisting of several subevents with a duration of about 25 s the magnitude of the force is approximately 2 6 10 12 n this vertical force is in contrast with the long period 150 s southward horizontal single force which has been determined by a previous study and interpreted to be due to the massive landslide an m s 5 2 earthquake initiated the eruption sequence the direction of the p wave first motion of this event observed at two nearby stations is consistent with the radiation pattern expected for the landslide and suggests that it represents the onset of the landslide the ground motions observed at station lon 67 km are dominated by rayleigh waves i e lamb pulse and provide tight constraints on the time sequence of the events

linear trends in salinity for the world ocean 1955 1998 1 quality controlled oceanographic profile salinity measurements from the world ocean database 2001 wod01 were used to calculate linear trends of zonally averaged salinity anomalies for running five year periods from 1955 1959 through 1994 1998 for the world ocean and the atlantic pacific and indian ocean basins from the surface to 3000 meters depth each basin exhibits large scale coherent trends most of the pacific is freshening with the exception of the subtropical south pacific the atlantic exhibits a deep freshening in the subpolar gyre and a shallower more intense increase in salinity in the tropics and subtropics the indian ocean is becoming more saline at all latitudes in the upper 150 meter layer with a subsurface freshening between 40 s and the equator in the 250 1000 meter layer there is freshening in both the weddell and ross seas

generation and propagation of infrasonic airwaves from volcanic explosions abstract analysis of infrasonic pressure waves generated by active volcanoes is essential to the understanding of volcanic explosion dynamics unlike seismic waves propagating in the earth infrasonic airwaves offer a relatively unfiltered representation of source motions at the vent during an eruption time varying acoustic propagation filters caused by changeable atmospheric conditions are minimal for microphones deployed at intermediate distances johnson et al j volcanol geotherm res in press