initial observations of polar mesospheric summer echoes using the eiscat svalbard radar polar mesospheric summer echoes pmse have been observed at various frequencies from mf to uhf and at various latitudes here we report the observation of pmse over svalbard 79 n at 500 mhz although pmse have been reported earlier at such high latitude at vhf notably around 50 mhz they had hitherto not been reported at such high frequency as 500 mhz furthermore this observation represents the first one using a frequency between 224mhz and 933mhz the pmse scattering mechanism is still open to debate and is certainly frequency dependent the new observations at 500 mhz will help to identify the transition frequency between different mechanisms

geochemistry and isotopes of fluids from sulphur springs valles caldera new mexico abstract detailed geochemistry supported by geologic mapping has been used to investigate sulphur springs an acid sulfate hot spring system that issues from the western flank of the resurgent dome inside valles caldera the most intense activity occurs at the intersection of faults offsetting caldera fill deposits and post caldera rhyolites three geothermal wells in the area have encountered pressures 4 8000 mg l these conditions cause argillic alterations throughout a large area non condensible gases consist of roughly 99 co 2 with minor amounts of h 2 s h 2 and ch 4 empirical gas geothermometry suggests a deep reservoir temperature of 215 to 280 c comparison of 13 c and 18 o between caco 3 from well cuttings and co 2 from fumarole steam indicates a fractionation temperature between 200 and 300 c by decarbonation of hydrothermally altered paleozoic limestone and vein calcite in the reservoir rocks tritium concentrations obtained from steam condensed in a mudpot and deep reservoir fluids baca 13 278 c are 2 1 and 1 0 t u respectively suggesting the steam originates from a reservoir whose water is mostly 50 yrs old deuterium contents of fumarole steam deep reservoir fluid and local meteoric water are practically identical even though 18 o contents range through 4 thus precipitation on the resurgent dome of the caldera could recharge the hydrothermal system by slow percolation from analysis of d and 18 o values between fumarol steam and deep reservoir fluid steam reaches the surface either 1 by vaporizing relatively shallow groundwater at 200 c or 2 by means of a two stage boiling process through an intermediate level reservoir at roughly 200 c although many characteristics of known vapor dominated geothermal systems are found at sulphur springs fundamental differences exist in temperature and pressure of our postulated vapor zone we propose that the reservoir beneath sulphur springs is too small or too poorly confined to sustain a true vapor dominated system and that the sulphur springs system may be a dying vapor dominated system that has practically boiled itself dry

first measurements of tidal modes in the lower thermosphere by the eiscat svalbard radar first measurements by the eiscat svalbard radar of ion velocities in the lower thermosphere show the presence of strong tidal or quasi tidal modes with periods of 24 12 and 8 hours the diurnal mode shows no variation of phase with height above 100 km in contrast the semidiurnal and terdiurnal modes show a steady variation of phase with height corresponding to vertical wavelengths of about 40 km and 30 km respectively in addition there is evidence at 93 km the lowest height measured of a planetary wave with a period of 2 3 days

mineral assemblages and oxygen and sulphur fugacities in natural water rock interaction processes abstract several mineral assemblages capable of buffering oxygen and sulphur fugacity and theoretical calculations were used to determine the fugacities of these two gas species over a temperature range between 150 and 350 c computed values were compared with those calculated from the composition of the geothermal fluids of larderello travale bagnore and piancastagnaio italy the geysers usa and cerro prieto mexico the possible hydrothermal mineral assemblages that best fit the field data are those containing minerals frequently found in many geothermal fields epidote chlorite k feldspar quartz and pyrite these assemblages can be used in place of the classical buffers based on iron oxides and sulphides

identification of density stratified waters in the late pleistocene north atlantic a faunal derivation abstract an expanded study of the radiolarian cycladophora davisiana in late pleistocene north atlantic marine sediments shows that over the last several hundred thousand years this species exhibits large variations in relative abundance the c davisiana curves in the north atlantic cores are quite similar with easily recognizable features common to all records minor deviations from the general pattern of this species abundance apparently reflect the response of c davisiana to specific oceanographic conditions characteristic of a particular area within the north atlantic c davisiana occurs today in high abundance 20 only in the sea of okhotsk extensive winter and early spring sea ice cover coupled with low surface water salinities during summer and fall is responsible for maintaining near freezing subsurface temperatures in this northwest pacific marginal sea as well as relatively stable temperatures and salinities at depths below a shallow subsurface temperature minimum during periods in the late pleistocene high c davisiana abundances 20 in the north atlantic were probably associated with oceanographic properties similar to those that exist in the sea of okhotsk today because of the relationship between relatively stable subsurface temperatures and salinities and high abundance levels of c davisiana analysis of this species abundance pattern at several locations throughout the high latitude north atlantic should assist in identifying source areas of deep water formation and determining the duration of deep convective processes at these sites

cycles steps and co2 paleoceanography in the united states from 1983 1986 the field of paleoceanography experienced continued growth during the last three years the first international conference on paleoceanography was held in zurich switzerland in july 1983 and a new journal devoted to the topic paleoceanography american geophysical union washington d c began publication in spring 1986 edited by dr james kennett of the university of rhode island nine legs of the r v glomar challenger concentrated upon paleoceanographic topics legs 71 75 in the south atlantic leg 81 in the north atlantic leg 85 in the equatorial pacific leg 86 in the northwest pacific and leg 90 in the southwest pacific several special symposia and conferences resulted in volumes of collected papers dealing with topics such as climate variability hansen and takahashi 1984 the global carbon cycle sundquist and broecker 1985 catastrophes and earth history berggren and van couvering 1984 orbital insolation and periodicity berger et al 1984 and coastal upwelling suess and thiede 1983 some very useful books have been published which summarize existing information on radiolaria anderson 1983 neogene planktonic foraminifera kennett and srinivasan 1983 calcareous nannofossils haq 1983 1984 and biostratigraphy bolli et al 1983

interpretation of downhole data and development of a conceptual model for the redondo creek area of the baca geothermal field available drilling records downhole surveys and surface discharge measurements from the wells drilled in the redondo creek area through 1981 were examined to determine the depths at which the wells penetrate permeable zones and thereby define those locations at which the pressure temperature measurements actually correspond to the reservoir conditions the results of these individual well analyses are used to estimate the initial pressure and temperature distributions of the reservoir system in the redondo creek area this information together with the well stratigraphy and the zones of fracture permeability penetrated by the wells is presented on vertical sections across the area the extent of a two phase region at the top of the reservoir system is also estimated using the pressure temperature distributions and the measured carbon dioxide content of the surface discharge from the baca wells the conceptual model presented provides the framework needed for detailed reservoir engineering studies 34 references 26 figures

noble gas evidence for two fluids in the baca valles caldera geothermal reservoir noble gas elemental and isotopic abundances were measured in steam from four wells in the baca geothermal reservoir located in the valles caldera new mexico the 40ar36ar ratio and noble gas elemental abundances relative to 36ar are all strongly correlated with 1 36ar the inverse of the argon content ratios of n produced 21ne and radiogenic 40ar to total 4he dominantly radiogenic are nearly constant at 2 1 10 8 and 0 20 respectively the 3he4he ratio covers a restricted range of 3 9 to 4 8 times atmospheric the high 3he content of the gas indicates the presence of a helium component ultimately derived from the mantle kr and xe isotopic compositions are close to atmospheric excess 129xe is 0 25 of the total 129xe the high degree of linear correlation among the various noble gas results strongly suggests that the baca reservoir contains two distinct fluids that are produced in varying proportions from individual wells the noble gases in fluid a 2900 mg 1 c1 are air like but with lighter gases and isotopes preferentially enriched the fluid a 36ar content is low only 13 that of 10 c air saturated water asw the second fluid b 1700 mg 1 c1 is the dominant carrier of the radiogenic and mantle derived gases the heavier non radiogenic gases are preferentially enriched in fluid b and its 36ar content is very low only 5 7 asw the source of the noble gases in fluid a is tentatively ascribed to leaching of the relatively young 1 4 m y volcanic bandelier tuff the radiogenic gases and mantle derived helium in fluid b suggest a deeper source possibly including gases escaping from a magma

hydrothermal brecciation in the jemez fault zone valles caldera new mexico results from continental scientific drilling program core hole vc 1 an unusual breccia sequence penetrated in the lower 30 m of continental scientific drilling program core hole vc 1 total depth 856 m records a complex hydrothermal history culminating in hydraulic rock rupture and associated alteration at the edge of the quaternary valles caldera the breccias both tectonic and hydrothermal in origin were formed in the jemez fault zone near the intersection of this major regional structure with the caldera s ring fracture margin tectonic breccias in the sequence are contorted crushed and sheared coexisting hydrothermal breccias lack such frictional textures but display matrix flow foliation and prominent clast rounding features characteristic of fluidization these hydrothermal breccias were intensely altered during at least five major stages to quartz illite phengite pyrite aggregates traces of molybdenite occur locally this assemblage indicates interaction with hydrothermal fluid at temperatures in excess of 200 c the extrapolated present maximum temperature of 184 c in the breccia zone therefore represents considerable cooling since these phases were formed fluid inclusions in the breccias also preserve evidence of the prior passage of hotter fluids the inclusions are principally two phase liquid rich secondary in origin and concentrated in hydrothermal quartz older high salinity inclusions unrelated to brecciation homogenize in the temperature range 189 246 c younger inclusions in part of interbreccia origin are low salinity and homogenize in the temperature range 230 283 c locally coexisting liquid and vapor rich inclusions document periodic boiling of the dilute fluids these fluid inclusion data along with the probable age of the hydrothermal breccias 1 5 ma the assumed depth at which they developed about 515 m and the contemporaneous state of stress extensional can be combined to model hydrothermal brecciation at the vc 1 site the minimum fluid pressure pfr required to hydrofracture these rocks was probably about 7 5 mpa 0 0146 mpa m a boiling point versus depth curve based on these pfr values graphically defines the physical conditions prevailing when the breccias were formed when fluid pressure at the assumed depth of brecciation exceeded that curve in response to rapid release of confining pressure possibly augmented by renewed heating flashing hydrothermal fluid fractured the enclosing rock large overpressures most likely induced by sudden seismic cracking of a hydrothermally sealed portion of the jemez fault zone led to local fluidization of the resulting breccias late quartz veining hydrothermal alteration and molybdenite mineralization were probably produced by the fluids responsible for brecciation

time gcm results for the quasi two day wave to understand how the quasi two day wave qtdw interacts with the mean flow and migrating tides we perturbed the lower boundary of the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm to excite the qtdw results from our initial model runs computed for a perpetual january 15th show wave amplitudes in wind and temperature that are in qualitative agreement with previous model results and observations the wave period and amplitude change over the duration of the model run and it is expected that this results from changes in the zonal mean zonal winds evidence supporting nonlinear interactions between the qtdw and the migrating tides is presented

climatology of the migrating terdiurnal tide tw3 in saber timed temperatures 1 the present paper is focused on the global spatial altitude and latitude structure and seasonal and interannual temporal variability of the migrating terdiurnal tide tw3 seen in 8 years 2002 2009 of observations of the kinetic temperature measured by the saber instrument on the timed satellite the tides migrating and nonmigrating and the planetary waves zonally traveling and stationary are simultaneously extracted from the satellite data it is found that the saber tw3 tide is dominated by different hough modes below and above 80 to 90 km height in the mesosphere it reflects mainly the evanescent feature of the first symmetric mode and in the lower thermosphere propagating modes with shorter vertical wavelengths dominate its structure the seasonal behavior of the terdiurnal tide at low latitudes is dominated by an annual variation with local summer amplification while that at midlatitudes is a combination of semiannual variation with maxima in equinoxes and an annual variability with winter enhancement the hough modes of the solar heating from waccm heating to a large extent determine the predominantly antisymmetric features of the saber tw3 tide during the solstice but are not able to explain well the predominant symmetric features in the equinoxes the tw3 tide reveals some interannual variability with a period of quasi 2 years which indicates an enhancement during the eastward phase of the stratospheric qbo

geology water geochemistry and geothermal potential of the jemez springs area canon de san diego new mexico abstract studies of the geology geochemistry of thermal waters and of one exploratory geothermal well show that two related hot spring systems discharge in canon de san diego at soda dam 48 c and jemez springs 72 c the hot springs discharge from separate strands of the jemez fault zone which trends northeastward towards the center of valles caldera exploration drilling to precambrian basement beneath jemez springs encountered a hot aquifer 68 c at the top of paleozoic limestone of appropriate temperature and composition to be the local source of the fluids in the surface hot springs at jemez springs comparisons of the soluble elements na li cl and b arguments based on isotopic evidence and chemical geothermometry indicate that the hot spring fluids are derivatives of the deep geothermal fluid within valles caldera no hot aquifer was discovered in or on top of precambrian basement it appears that low to moderate temperature geothermal reservoirs

the 8 hour tide in the arctic mesosphere and lower thermosphere an all sky vhf meteor radar at esrange 68 n 21 e near kiruna in northern sweden has been used to investigate the 8 hour tide in the arctic mesosphere and lower thermosphere we present a climatology of the 8 hour tide over the period october 1999 to april 2001 the tide appears to be a persistent feature of the arctic atmosphere although a large day to day variability of the tidal amplitude is observed at times the 8 hour tide reaches amplitudes over 30 m s 1 the amplitude of the tide increases with height across the observed height range of 80 100 km monthly mean tidal amplitudes range from 2 m s 1 to values as large as 10 m s 1 a clear seasonal behavior is apparent with maximum amplitudes observed in the autumn vertical wavelengths are shortest in winter and spring 25 35 km and longest in summer and autumn 50 90 km at least on some occasions the vertical wave number relationships between the 8 12 and 24 hour tides suggest that the 8 hour tide is being generated by nonlinear interaction between the 12 and 24 hour tides

long term observations of the arctic mesosphere with the mst radar at poker flat alaska in this report we summarize the results of 22 months of observations of arctic mesosphere echoes with the 50 mhz radar at poker flat alaska operation with a partially complete system began in february 1979 and has continued on a nearly continuous basis to the present time the altitude range of the mesospheric echoes obtained during this period shows a pronounced seasonal variation during summer months the mesospheric echoes are relatively continuous in time and extend from about 80 to 100 km with an unexpectedly strong peak in signal to noise ratio at about 85 km in contrast in nonsummer months mesospheric echoes are less intense and occur at lower altitudes in the range from 55 to 80 km these lower altitude nonsummer echoes are observed primarily during daytime hours when energetic auroral particle precipitation as determined by the poker flat 30 mhz riometer is present

gas geochemistry of the valles caldera region new mexico and comparisons with gases at yellowstone long valley and other geothermal systems abstract noncondensible gases from hot springs fumaroles and deep wells within the valles caldera geothermal system 210 300 c consist of roughly 98 5 mol co 2 0 5 mol h 2 s and 1 mol other components 3 he 4 he ratios indicate a deep magmatic source r r a up to 6 whereas 13 c co 2 values 3 to 5 do not discriminate between a mantle magmatic source and a source from subjacent hydrothermally altered paleozoic carbonate rocks regional gases from sites within a 50 km radius beyond valles caldera are relatively enriched in co 2 and he but depleted in h 2 s compared to valles gases regional gases have r r a values 1 2 due to more interaction with the crust and or less contribution from the mantle carbon sources for regional co 2 are varied during 1982 1998 repeat analyses of gases from intracaldera sites at sulphur springs showed relatively constant ch 4 h 2 and h 2 s contents the only exception was gas from footbath spring 1987 1993 which experienced increases in these three components during drilling and testing of scientific wells vc 2a and vc 2b present day valles gases contain substantially less n 2 than fluid inclusion gases trapped in deep early stage post caldera vein minerals this suggests that the long lived valles hydrothermal system ca 1 myr has depleted subsurface paleozoic sedimentary rocks of nitrogen when compared with gases from many other geothermal systems valles caldera gases are relatively enriched in he but depleted in ch 4 n 2 and ar in this respect valles gases resemble end member hydrothermal and magmatic gases discharged at hot spots galapagos kilauea and yellowstone

climate and ocean variability during the middle and late holocene recorded in laminated sediments from alfonso basin gulf of california mexico a laminated sequence core bap96 cp 24 38 12 n 110 33 24 w 390 m depth from the alfonso basin in bay of la paz southern gulf of california contains a record of paleoceanographic and paleoclimatic changes of the past 7900 yr radiolarian assemblages and magnetic susceptibility are used as proxies of oceanographic and climatic variability the records provide a regional scenario of the middle and late holocene suggesting two major climatic regimes and several millennial scale events conditions relatively warmer and drier than today occurred from 7700 to 2500 cal yr bp promoting the intensification of evaporation processes and the prevalence of the gulf of california water in the basin these conditions correlate with strong droughts in the middle holocene of north america and with minimal incursion of tropical waters into the gulf of california proxies indicate a warm scenario and the dominance of the equatorial surface water in the alfonso basin from 2400 to 700 cal yr bp suggesting the intensification of enso cycles a climatic signal between 1038 and 963 cal yr bp may be correlated with global signal of the medieval warm period several cooling events are recognized at 5730 3360 2700 1280 and 820 cal yr bp and are associated with intensification of northwest winds leading to upwellings and enhanced productivity in the basin

tidal variability in the ionospheric dynamo region 1 the seasonal and interannual variability of migrating sun synchronous and nonmigrating solar atmospheric tides at altitudes between 100 and 116 km are investigated using temperature measurements made with the saber instrument on the timed spacecraft during 2002 2006 quasi biennial variations of order 10 15 in migrating diurnal and semidiurnal tidal amplitudes are found presumably due to modulation by the quasi biennial oscillation qbo as the tides propagate from their troposphere and stratospheric sources to the lower thermosphere a number of nonmigrating tidal components are found that have the potential to produce significant longitudinal variability of the total tidal fields the most prominent of these i e those that appear at amplitudes of order 5 10 k in a 5 year mean climatology include the zonally symmetric s 0 diurnal tide d0 the eastward propagating diurnal and semidiurnal tides with zonal wave numbers s 2 de2 and se2 and s 3 de3 and se3 and the following westward propagating waves diurnal s 2 dw2 semidiurnal s 1 sw1 s 3 sw3 and s 4 sw4 and terdiurnal s 5 tw5 these waves can be plausibly accounted for by nonlinear interaction between migrating tidal components and stationary planetary waves with s 1 or s 2 or by longitudinal variations of tropospheric thermal forcing additional waves that occur during some years or undergo phase cancellation within construction of a 5 year climatology include dw5 se1 se4 sw6 te1 tw1 and tw7 it is anticipated that the winds that accompany all of these waves in the 100 170 km region will impose longitudinal variability in the electric fields produced through the ionospheric dynamo mechanism thereby modulating vertical motion of the equatorial ionosphere and the concomitant plasma densities in addition to the wave 4 modulation of the equatorial ionosphere that has recently been discovered and replicated in modeling studies the waves revealed here will generate wave 1 sw1 sw3 d0 dw2 wave 2 sw4 tw1 wave 3 de2 se1 wave 4 de3 se2 dw5 sw6 te1 tw7 wave 5 se3 and wave 6 se4 components of this ionospheric variability depending on year and time of year however the absolute and relative efficiencies with which these waves produce electric fields remains to be determined

the terdiurnal tide in the mesosphere and lower thermosphere over london canada 43 n 81 w radars have been used successfully for many years to measure atmospheric diurnal and semidiurnal tides but studies of the atmospheric terdiurnal tide have only rarely been reported to date in the literature in this paper we investigate the amplitude phase and vertical wavelength for the terdiurnal tide using the university of western ontario uwo 2 mhz radar near london canada emphasis is placed on short term monthly seasonal and annual variations of the terdiurnal tide the results of the present study bring out certain new aspects of the terdiurnal tide at midlatitudes in the northern hemisphere we show that terdiurnal tides have significant amplitudes in the mesosphere and lower thermosphere indeed the terdiurnal amplitudes are often comparable to the diurnal ones we also draw attention to the annual variability and especially highlight the occurrence of the terdiurnal tide in non winter months for example the occurrence of the terdiurnal tide in spring months is not uncommon thus it seems that the 8 hour component observed over london canada cannot be explained by the terdiurnal tide being due to solar heating alone particular cases of the terdiurnal tide are examined and the observed amplitude and phase profiles of the terdiurnal tide at certain times of the year are discussed in terms of nonlinear interaction between the diurnal and semidiurnal tides we suspect that this effect may also explain the fact that diurnal and semidiurnal tides at our station often seem suppressed relative to other sites thayaparan et al 1995a on the basis of our previous and present observations it is also possible that large terdiurnal amplitudes observed at certain times of the year may be partly explained in terms of tidal gravity wave interactions however this possibility needs to be further investigated in the future

a review of gravity wave saturation processes effects and variability in the middle atmosphere this paper provides a review of our current understanding of the processes responsible for gravity wave saturation as well as the principal effects and variability of saturation in the lower and middle atmosphere we discuss the theoretical and observational evidence for linear and nonlinear saturation processes and examine the consequences of saturation for wave amplitude limits momentum and energy fluxes the diffusion of heat and constituents and the establishment of a near universal vertical wavenumber spectrum recent studies of gravity wave variability are reviewed and are seen to provide insights into the significant causes of wave variability throughout the atmosphere

mean winds tides and quasi 2 day wave in the polar lower thermosphere observed in european incoherent scatter eiscat 8 day run data in november 2003 1 simultaneous european incoherent scatter eiscat radar observations using two eiscat radars the tromso 69 6 n 19 2 e uhf radar and the eiscat svalbard radar longyearbyen 78 2 n 16 0 e were conducted for 8 consecutive days from 11 to 19 november 2003 to study the lower thermospheric wind dynamics in the polar region altitude profiles of the amplitudes of the diurnal and semidiurnal components at tromso and longyearbyen are similar the semidiurnal amplitudes in the meridional and zonal components exhibit maxima at 105 107 km with values of 70 90 m s 1 the semidiurnal phases vary with roughly a 30 km vertical wavelength between 98 and 110 km the quasi 2 day wave q2dw was not detected in the lower thermosphere at either tromso or longyearbyen during the period while it was found between 70 and 82 km in the mesosphere with the colocated tromso mf radar this observational result suggests that in general the q2dw attenuates in the mesosphere and cannot penetrate into the lower thermosphere in winter ion drag acceleration of the wind is generally negligible below 107 km at tromso and below 118 km at longyearbyen but significant ion drag acceleration is found above these heights a comparison of mean wind and tidal amplitudes and phases with national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model predictions for the period shows some agreement

light lithophile element boron lithium abundances in the valles caldera new mexico vc 1 core hole boron and lithium abundance distributions are very different in the sedimentary and volcanic sections of the vc 1 core hole valles caldera new mexico in the sedimentary section the wide variations in boron and lithium abundances probably reflect both diagenesis and introduction of these elements in early hydrothermal fluids late higher temperature fluids appear to have leached boron and lithium from some rocks adjacent to fault zones and aquifers the correlation of boron with lithium suggests that these elements behave in similar ways during diagenesis and hydrothermal alteration the small variation of boron and lithium abundances in most of the vitreous volcanic rocks from the upper part of the core implies that their source was relatively homogeneous following primary devitrification boron appears to have been stable but lithium was mobile boron may have been stabilized by the development of boron bearing submicroscopic phenocrysts in the lavas or boron may be less soluble than lithium in relatively cool groundwater

on the role of an anisotropic gravity wave spectrum in maintaining the circulation of the middle atmosphere the spectral parameterization of gravity wave momentum deposition proposed by medvedev and klaassen has been incorporated into the canadian middle atmosphere model numerical experiments show that an anisotropic gravity wave source significantly improves the middle atmosphere circulation compared to an isotropic source these results suggest that at least in midlatitudes the gravity waves primarily responsible for the momentum deposition at mesospheric heights are launched with observed phase velocities which are primarily in the same direction as the mean wind at tropospheric source heights

solar tides as revealed by measurements of mesosphere temperature by the mls experiment on uars abstract temperatures between 25 and 86 km measured by the microwave limb sounder mls experiment on the upper atmosphere research satellite uars are analyzed to delineate diurnal semidiurnal and terdiurnal tidal structures and stationary planetary waves these fourier components are determined from temperatures averaged in bins covering 5 latitude 30 longitude and 1 h in local time this study confirms the presence of diurnal nonmigrating tides with zonal wavenumbers s 0 2 3 s 0 s 0 implying westward eastward propagation and semidiurnal tides with s 1 and 3 and some components of lesser importance that were previously determined from uars wind measurements near 95 km the seasonal latitudinal and height structures of these components are now revealed and utilized to aid in interpreting their behaviors and ascertaining their origins new discoveries include the terdiurnal s 2 and s 4 components and trapped nonmigrating diurnal tides with s 0 and s 2 the former are like

holocene laminated sediments from the southern gulf of california geochemical mineral magnetic and microfossil study geochemical magnetic mineral analyses and microfossils radiolarians are used to characterise a holocene laminated sequence from the alfonso basin northern bay of la paz southern gulf of california in most cases dark and light laminae show similar bulk chemical compositions and magnetic mineral properties however dark laminae contain relatively more terrigenous elements al si fe k and mg supporting a pluvial origin related to the volcanic siliceous tuffs around the bay of la paz in light laminae calcium content is higher representing biogenic input the magnetic signal is dominated by low coercivity fine grained low titanium titanomagnetites and magnetite hysteresis ratio parameters in domain state plots show that samples fall in the pseudo single domain field indicating mixtures of single and multi domain particles variations in hysteresis saturation magne tisation parameters for dark and light laminae reflect changes in relative mineral concentration results indicate a dominant volcanic source for magnetic minerals into the basin associated with variable pluvial and or aeolian transport low radiolarian abundance in dark laminae seems to be associated with larger penetration and longer residence time of oligotrophic subtropical waters into the bay that occurred during el nino southern oscillation enso events light laminae are the result of episodic pulses of high productivity we suggest that dark light laminae result from oceanographic and climatic cyclic processes with main terrigenous input variation possibly associated with enso forcing of pluvial influx and or latitudinal migration of the intertropical convergence zone the laminated sequence of the alfonso basin formed a non annual depositional system in contrast to the varved sediments characteristic of the central gulf of california basins copyright 2010 john wiley sons ltd

vertical water mass circulation and the distribution of radiolaria in surface sediments of the gulf of california abstract quantitative analysis of microfossils from sediment cores taken in the gulf of california shows that the distribution of radiolaria is controlled by both surface ocean conditions and vertical circulation patterns in this marginal sea fifty four surface sediment samples from intermediate water depths were used in this study samples were taken from surface scrapings of box cores or large diameter gravity cores to insure that the samples represented recent deposition q mode factor analysis was used to divide the radiolarian population found in the gulf of california into three assemblages the first is made up of species typical of the gulf these species are in general not a major part of the open ocean radiolarian fauna the general geographic distribution of this assemblage shows a maximum abundance in the north central part of the gulf where warmer high salinity water is found this assemblage is also important in areas of upwelling the second fauna is dominated by radiolaria typical of the subtropical pacific ocean this assemblage dominates in the southern part of the gulf the last assemblage is dominated by species commonly found in the eastern boundary of the north pacific and is found in areas of upwelling within the gulf of california analysis shows that the first two assemblages are strongly influenced by the vertical structure of the southern part of the gulf of california the gulf assemblage shows a maximum in samples taken between 600 and 800 m water depth the subtropical assemblage shows high values in shallow sites and in samples taken in water depths greater than 800 m and a distinct minimum at intermediate depths the fauna typical of the north pacific eastern boundary current shows no depth preference the maximum in the gulf assemblage coincides with the depth of strong southerly flow of warmer higher salinity water out of the gulf of california this suggests that the abundance of the gulf assemblage in the southern end of the gulf of california is in part controlled by advection and thus vertical circulation has an important part in controlling the distribution of radiolaria in the sediments of the gulf of california

a sr isotopic comparison between thermal waters rocks and hydrothermal calcites long valley caldera california abstract the 87 sr 86 sr values of thermal waters and hydrothermal calcites of the long valley caldera geothermal system are more radiogenic than those of young intracaldera volcanic rocks five thermal waters display 87 sr 86 sr of 0 7081 0 7078 but show systematically lighter values from west to east in the direction of lateral flow we believe the decrease in ratio from west to east signifies increased interaction of deeply circulating thermal water with relatively fresh volcanic rocks filling the caldera depression all types of pre syn and post caldera volcanic rocks in the west and central caldera have 87 sr 86 sr m between about 0 7060 and 0 7072 and values for sierra nevada granodiorites adjacent to the caldera are similar sierran pre intrusive metavolcanic and metasedimentary rocks can have considerably higher sr isotope ratios 0 7061 0 7246 and 0 7090 0 7250 respectively hydrothermally altered volcanic rocks inside the caldera have 87 sr 86 sr m slightly heavier than their fresh volcanic equivalents and hydrothermal calcites 0 7068 0 7105 occupy a midrange of values between the volcanic plutonic rocks and the sierran metamorphic rocks these data indicate that the long valley geothermal reservoir is first equilibrated in a basement complex that contains at least some metasedimentary rocks reequilibration of sr isotope ratios to lower values occurs in thermal waters as convecting geothermal fluids flow through the isotopically lighter volcanic rocks of the caldera fill

n2 ar he compositions in fluid inclusions indicators of fluid source abstract a quadrupole mass spectrometer was used to measure bulk samples of conservative gas species n 2 ar and he in fluid inclusions from a variety of hydrothermal systems analyses of these tracer elements help determine 1 1 if gases extracted by bulk inclusion analyses can provide accurate measurement of n 2 ar he in active and fossil geothermal systems 2 2 if hydrothermal fluids associated with paleogeothermal systems in a continental setting follow n 2 ar he systematics similar to th the western pacific rim active geothermal systems specifically new zealand and 3 3 whether different deposit types systematically vary with regard to n 2 ar he the n 2 ar he ratios of fluid inclusion volatiles released from recently deposited minerals from the valles system are similar to those of present day valles thermal waters those inclusion samples from deep within the valles system below a regional aquitard increase in n 2 compositions for inclusions from the questa and copper flat porphyry deposits are n 2 rich similar to those of arc related volcanic gases whereas those from taylor creek sn deposit appear to be mixtures of magmatic and crustal components n 2 ar he ratios of the precambrian tribag deposit suggest a basalt source but significant levels of self generated he from u and th in the inclusion fluids are also possible inclusions from two epithermal deposits with low salinity inclusions have n 2 ar he ratios trending towards air saturated meteoric waters asw and those inclusions with higher salinities indicate minor to no asw component the n 2 ar he ratios in fresnillo and cochiti inclusions which have magmatic helium isotopic ratios indicate additions of magmatic gases to meteoric fluids inclusions from sediment hosted deposits that contain hydrocarbon bearing brines are he rich as are meteoric waters with a long residence time in the crust at relevant pressure temperature composition conditions henry s law constants of n 2 ar and he are similar and thus the relative amounts of these species trapped under boiling conditions will not vary appreciably from solubility controlled amounts in coexisting liquid furthermore there is no evidence of he loss or gain in inclusions by diffusion process data from the various systems that were examined indicate that fluid inclusion n 2 ar he compositions may be related to magmatic fluid sedimentary brine deep circulating meteoric fluid and shallow circulating meteoric fluid sources which we modified from those proposed by giggenbach 1986 relationships between the n 2 ar he tracer gases and other measurable quantities in fluid inclusions are indicated to be helpful in understanding fluid mixing processes in paleogeothermal systems

the hydrothermal outflow plume of valles caldera new mexico and a comparison with other outflow plumes stratigraphic temperature gradient hydrogeochemical and hydrologic data have been integrated with geologic data from previous studies to show the structural configuration of the valles caldera hydrothermal ouflow plume hydrologic data suggest that 25 50 of the discharge of the valles outflow is confined to the jemez fault zone which predates caldera formation thermal gradient data from bores penetrating the plume show that shallow gradients are highest in the vicinity of the jemez fault zone up to 190 c km shallow heat flow above the hydrothermal plume is as high as 500 mw m 2 near core hole vc 1 jemez fault zone to 200 mw m 2 at fenton hill jemez plateau chemical and isotopic data indicate that two source reservoirs within the caldera redondo creek and sulphur springs reservoirs are parents to mixed fluids flowing in the hydrothermal plume however isotopic data borehole data basic geology and inverse relations between temperature and chloride content at major hot springs indicate that no single reservoir fluid and no single diluting fluid are involved in mixing the valles caldera hydrothermal plume is structurally dominated by lateral flow through a belt of vertical conduits jemez fault zone that strike away from the source reservoir stratigraphically confined flow is present but dispersed over a wide area in relatively impermeable rocks the valles configuration is contrasted with the configuration of the hydrothermal plume at roosevelt hot springs which is dominated by lateral flow through a near surface widespread permeable aquifer data from 12 other representative geothermal systems show that outflow plumes occur in a variety of magmatic and tectonic settings have varying reservoir compositions and have different flow characteristics although temperature reversals are commonly observed in wells penetrating outflow plumes reversals are not observed in all plumes less information is available on the absolute age of hydrothermal outflow plumes although the data show that they can be as old as 106 years and display episodic behavior

radiolarian distribution in the water column southern gulf of california and its implication in thanatocoenose constitution abstract the geographical and depth distributions of five radiolarian plankton assemblages defined through q mode factor analysis of 24 plankton samples demonstrate a direct correspondence to the distribution of oceanographic water masses in the southern gulf of california two assemblages are associated exclusively with water masses of the mixed layer two represent only subsurface water masses and one is important in both surface and subsurface environments the lithomelissa thoracites group and peridium spinipes are predominant species in water that is formed at the surface of the guaymas basin and subsequently is subducted southward into the carmen basin plagiocantha panarium is the predominant species in upwelled surface water at the carmen basin while tetrapyle octhacanta and botryostrobus scutum follow the incursion of the subtropical water mass into the gulf of california through the pescadero and farallon basins druppatractus variabilis and porodiscus sp b occur conspicuously in the upper layer of the pacific intermediate water between approximately 400 and 700 m water depth statistical correlation between plankton and sediment assemblages supports previous evidence that the radiolarian thanatocoenose in the gulf of california is composed primarily of species from the surface mixed layer two exceptions to this are observed in the data first the upwelling plankton assemblage was not well correlated to the sediment assemblage and second input to the sediment during glacial stages appears to be dominated by subsurface forms

reservoir processes and fluid origins in the baca geothermal system valles caldera new mexico at the baca geothermal field in the valles caldera new mexico 19 deep wells were drilled in an attempt to develop a 50 mwe megawatts electric power plant the chemical and isotopic compositions of steam and water samples have been used to indicate uniquely the origin of reservoir fluids and natural reservoir processes two distinct reservoir fluids exist at baca these fluids originate from the same deep high temperature 335 c saline 2500 mg kg cl parent water but have had different histories during upflow one fluid from wells 4 and 13 is isotopically light high in radiogenic noble gases co2 and hco3 and low in ca it has a temperature of 290 295 c and a reservoir chloride near 1900 mg kg this fluid resulted from rapid upward flow through 1 1 to 1 4 m y old bandelier tuff reservoir rocks after long residence in pre bandelier 7 m y sediments and precambrian basement rocks and 25 dilution with high altitude cold groundwater from redondo peak the other water from wells 15 19 and 24 moved slowly through the bandelier tuff and cooled conductively with minor steam loss for well 19 from 335 c to 280 260 c apparently short residence in old basement rocks has left this water with low radiogenic gases conductive cooling without mixing has kept the original chloride and relatively heavy isotope composition of the deep water the recharge to the deep parent water is not well understood but may be from lower elevation precipitation outside the valles caldera area gases are in equilibrium in all liquid reservoir fluids at near reservoir temperatures and the concentrations of atmospheric gases are similar to those of air saturated water indicating little boiling and steam loss all water solutes and gases in the reservoir fluids originate from air saturated meteoric recharge water watermineral reactions and rock leaching with the possible exception of excess 3he that must have an ultimate mantle source this gas could originate directly from magma or from leaching of intrusive volcanic rocks beneath the bandelier

modeling and analysis of the structure and generation of the terdiurnal tide the terdiurnal or 8 h tide has been seen in a number of midlatitude radar measurements and has recently been mapped globally at 95 km a series of calculations and model simulations are used to examine the processes responsible for generating this tide and for its strong hemispheric asymmetry the model tidal structure deviates significantly from the structure of a single hough mode in contrast to the diurnal tide the dominant cause of the hemispheric asymmetry is the sensitivity of the propagation to the background state particularly the static stability several conceptual views of the tide are explored to give a heuristic view of this asymmetry this analysis predicts that particular modes are prohibited from propagating in large regions of the summer mesosphere the tide occurs naturally in a three dimensional nonlinear model extending from the tropopause to the lower thermosphere the model tide shows a number of features in common with observations including amplitude maxima in midlatitudes a wintertime peak and zonal winds larger than meridional winds the tidal amplitude in the model is weaker than observed at 95 km several interactive model integrations are performed to determine the forcing mechanism for the tide these calculations indicate that the direct solar forcing of the terdiurnal tide is the dominant mechanism occurring in the model at middle and high latitudes nonlinear interactions contribute to the low latitude tide

hydrothermal alteration in the baca geothermal system redondo dome valles caldera new mexico thermal fluids circulating in the active hydrothermal system of the resurgent redondo dome of the valles caldera have interacted with their diverse host rocks to produce well zoned alteration assemblages which not only help locate permeable fluid channels but also provide insight into the system s thermal history the alteration shows that fluid flow has been confined principally to steeply dipping normal faults and subsidiary fractures as well as thin stratigraphic aquifers permeability along many of these channels has been reduced or locally eliminated by hydrothermal self sealing alteration from the surface through the base of the miocene paliza canyon formation is of three distinctive types argillic propylitic and phyllic argillic alteration forms a blanket above the deep water table in formerly permeable nonwelded tuffs beneath the argillic zone pervasive propylitic alteration is weakly developed in felsic host rocks but locally intense in deep intermediate composition volcanics strong phyllic alteration is commonly but not invariably associated with major active thermal fluid channels phyllic zones yielding no fluid were clearly once permeable but now are hydrothermally sealed high temperature alteration phases at baca are presently found at much lower temperatures we suggest either that isotherms have collapsed due to gradual cooling of the system that they have retreated without overall heat loss due to uplift of the redondo dome that the system has shifted laterally or that it has contracted due to a drop in the water table the deepest well b 12 3423 m in the dome may have penetrated through the base of the active hydrothermal system below a depth of 2440 m in this well hydrothermal veining largely disappears and the rocks resemble those developed by isochemical thermal metamorphism the transition is reflected by temperature logs which show a conductive thermal gradient below 2440 m this depth may mark the dome s neutral plane which separates an upper permeable zone of extensional fracturing from a lower less permeable compressional regime the baca hydrothermal system is similar to those which have formed ore deposits in other calderas particularly creede colorado type epithermal silver base metal veins and stockworks recent scientific drilling has also intersected a deep zone of strong phyllic alteration and molybdenum mineralization in the valles caldera s ring fracture system a setting which localized a large stockwork molybdenite orebody in the nearby questa caldera

seasonal variations of the terdiurnal tide in the mesosphere and lower thermosphere a model study observations of the terdiurnal 8 hour tidal wind oscillations in the mesosphere and lower thermosphere mlt reveal strong seasonal and latitudinal variations the tidal amplitudes reach a maximum of about 15 20 m s 1 at midlatitudes in winter the vertical phase progression corresponds to very long vertical wavelengths during summer the amplitudes are typically weaker and the phases are less regular first simulations of the terdiurnal tide with the spectral mesosphere lower thermosphere model are presented the model explicitly accounts for the solar thermal excitation in the middle and upper atmosphere and reproduces the salient features of the terdiurnal wind oscillations well the preferential solar excitation of antisymmetric terdiurnal modes capable of propagating into the mlt combined with an asymmetric atmospheric response appears to be primarily responsible for the observed seasonal variations nonlinear interactions of the diurnal and semidiurnal tides are demonstrated to make a noticeable in situ contribution to the excitation of the terdiurnal tide at 95 100 km especially during equinox

seasonal trends and preservation biases of polycystine radiolaria in the northern california current system we analyzed a 2 year sediment trap record of 76 species of radiolaria from three locations across the northern california current system q mode factor analysis identifies the fundamental trends in the radiolarian data with a five factor model that explains 86 of the trap data the factor assemblages that emerge from this analysis have temporal and spatial aspects that reflect fundamental oceanographic features of the eastern north pacific the most dominant process revealed by this analysis is related to the seasonality of the california current two factors illustrate this the california current factor which has highest loadings during summer and fall and the winter factor which is most important in the winter and spring together they account for 75 of the information in the trap samples from the two moorings located in the coastal region extending to 300 km offshore the oceanic environment sampled by the mooring 650 km offshore is strongly influenced by transitional waters and those from the central and subarctic gyres loadings of the three factors related to these oceanographic regions show marked differences between years which illustrates the latitudinal variability in the divergence of the north pacific current spatial distributions of the trap factors in surface sediments beneath the california current system generally agree with the temporal and spatial patterns they exhibit in the traps nonetheless the trap factor model can only describe up to 50 of the radiolarian sediment data which means the species ratios in the sediment traps are significantly different than those in the sediments a factor model using only robust species reveals the same basic trends as the first analysis but the culled model is able to describe a larger fraction of the sediment data 63 91 in sediments directly beneath the mooring sites however the increase in the amount of sediment data explained by the culled model is not distributed equally across all factors but is due to very high estimates of one factor in the coastal sediments the california current factor at the nearshore mooring site 130 km offshore this factor explains 69 of the sediment data versus only 32 of the data in the traps where it was derived this discrepancy suggests that either these two years of trap data are anomalous and have underestimated the predominance of the california current assemblage over long time periods or the culled factor model rather than eliminating the dissolution bias actually overemphasizes the importance of well preserved species in the coastal environment

the distribution of arsenic iii and arsenic v in geothermal waters examples from the massif central of france the island of dominica in the leeward islands of the caribbean the valles caldera of new mexico u s a and southwest bulgaria abstract data for as iii as v and total as for various types of geothermal spring water are given the different species of as were separated at the time of sampling after filtration acidification and dilution where necessary using an anion exchange method total as as iii and as v were determined by flameless atomic absorption spectrometry the total as content ranges from 5 to 1800 g l 1 samples from dominica show evidence of different sulfur arsenic oxidation kinetics as iii being the major component 85 99 in fluids from deep levels of the geothermal reservoir and also 99 in oxidized waters of the acid sulfate type the bicarbonate spring water of the valles caldera new mexico contains more as iii than as v but there as v is the major component of the acid sulfate springs as iii proves to be the predominant form 60 100 in the warm alkaline waters from southwest bulgaria a selection of co 2 rich spring waters from the central massif france cezallier is analysed two groups are distinguished on the basis of major element chemistry and total as content oxidized forms are mainly encountered in the first group including a well sample containing 0 5 as iii the as iii content of the second group ranges from 10 to 70 these preliminary results indicate that the fluids directly related to hydrothermal systems contain mainly as iii whereas acid sulfate springs have a variable as iii content bicarbonate waters are generally enriched in oxidized as in the absence of springs or sinks within a geothermal region the total as concentration may display conservative properties but both as iii and as v may be reactive during mixing and cooling

tidal oscillations of the arctic upper mesosphere and lower thermosphere in winter the upper mesosphere and lower thermosphere of the northern polar cap was investigated using fabry perot interferometer measurements of the horizontal wind velocity in the lower thermosphere meridian scanning photometer observations of atomic oxygen green line brightness in the lower thermosphere and michelson interferometer records of the infrared meinel oh bands brightness and rotational temperature in the upper mesosphere tidal airglow oscillations in the absence of local solar heating were studied using a superposed epoch analysis of observations obtained around three new moon intervals november 9 22 1993 december 7 20 1993 and january 4 17 1994 in eureka 80 n tidal harmonics were uncovered with an iterated least chi squared fit and their existence in the data tested using a goodness of fit probability against a null hypothesis of no oscillations no single dominant tide was found at all times and altitudes of the winter arctic upper mesosphere and lower thermosphere the horizontal wind velocity of the lower thermosphere exhibited all the first three harmonics of the tide with the largest amplitude oscillations shown by the diurnal component of the meridional wave speed the atmospheric layer near the mesopause that contributes to the oh airglow emission experienced terdiurnal oscillations throughout the winter season theoretical polarization relations for evanescent tides considerations of energy density propagation with altitude and a day by day analysis of the zonal and meridional wind speed and temperature all indicate that the terdiurnal tide observed on november was an evanescent zonally symmetric tide other data indicate propagating tides migrating tides or a mixture of both

valles caldera region new mexico and the emerging continental scientific drilling program valles caldera is best known in recent years as an excellent example of a resurgent caldera smith and bailey 1968 and as the site of a high temperature geothermal system dondanville 1978 however valles caldera and the surrounding jemez mountains volcanic field possess a rich history of geologic research that dates back to the late 1800s through the years the research focus has changed as different economic and scientific factors have exerted their influence early work emphasized mining activity while modern work has stressed volcanology and later geothermal development only in the last 5 years has it been possible to view the region as a dynamic integrated magma hydrothermal system having a complex evolution lasting more than 13 m y gardner et al 1986 goff and nielson 1986 self et al 1986

a strontium isotope study of the vc 1 core hole and associated hydrothermal fluids and rocks from valles caldera jemez mountains new mexico chemical and strontium isotopic analyses have been performed on 10 geothermal waters from the valles caldera jemez mountain region as well as 10 rock samples collected in the vc 1 scientific core hole the 87sr 86sr values of other rocks sampled in the jemez mountains have also been used in this study to understand relations between the fluids and rocks of the volcanically driven geothermal system and the lateral outflow plume discharging down the jemez fault zone the strontium content of groundwater is linked to the host rock composition the aquifer temperature and therefore the solubility of sr containing minerals low sr concentrations in the fluid are found with a high temperature and or volcanic host rocks whereas high sr concentrations are characteristic of a low temperature and or a paleozoic sedimentary aquifer important variations of the 87sr 86sr value in hydrothermal waters 0 70842 0 72193 are related to chemical composition sr content and host rocks for vc 1 core samples the sr isotopic ratios are also markedly variable 0 70459 0 75686 low for the quaternary volcanics and high for the paleozoic sedimentary rocks the same observation is made for other jemez mountains rocks 0 70465 0 8163 with in addition high 87sr 86sr values for precambrian crystalline rocks a good correspondence is generally found between the waters and the reservoir rocks studied here which indicates that isotopic equilibrium is rapidly attained the following suite of hydraulically related fluids displays a progressive enrichment in radiogenic strontium baca wells 87sr 86sr 0 7084 0 7094 vc 1 core hole at 483 m 0 7152 0 7154 main jemez spring 0 7217 and soda dam 0 7219 this trend is associated with flow through paleozoic rocks and with the length of the flow path from the center of valles caldera primary geothermal fluids toward san diego canyon along the jemez fault zone derivative waters

oceanographic conditions associated with high abundances of the radiolarian cycladophora davisiana abstract the cosmopolitan radiolarian cycladophora davisiana usually comprises less than 5 of the radiolarian fauna in holocene sediments in recent sediments from the sea of okhotsk however this species frequently represents more than 20 of the radiolarian assemblage at times during the late pleistocene abundances of this species in excess of 40 are recorded in marine sediments from high latitude oceans 40 of both hemispheres the sea of okhotsk apparently represents a modern analogue of climatic and oceanographic conditions that existed throughout large portions of high latitude oceans at times during the late pleistocene the near surface water structure of the sea of okhotsk is characterized by a low salinity surface layer with a strong temperature minimum near its base the low surface salinities are responsible for maintaining near freezing subsurface temperatures as well as establishing relatively stable temperatures and salinities at depths below the temperature minimum this water structure is produced at least in part by intense freezing of sea ice in winter with subsequent summer melting the physical characteristics of the upper water column affect the abundance and activity of shallow dwelling flora and fauna while providing a stable subsurface environment for deeper dwelling fauna

depth related radiolarian assemblage in the water column and surface sediments of the japan sea plankton tows and surface sediments from the japan sea a marginal sea of the northwestern pacific were examined to study the depth distribution of modern radiolarians the depth distribution patterns between the living assemblage in the water column and the thanatocoenose in surface sediments are similar to each other indicating that the depth related assemblage in sediments is closely related to the living depths of major species four clear restrictions of many species to discrete depth zones are recognized in the water column from the surface down to 2000 m 1 upper subsurface water species which are abundant from 40 to 120 m larcopyle butschlii juvenile form spirocyrtis subscalaris spongodiscus resurgens and lipmanella virchowii 2 lower subsurface water species which are abundant from 40 to 300 m larcopyle butschlii adult form ceratocyrtis histricosa and spongotrochus glacialis 3 intermediate water species which have population maxima from 160 to 300 m ceratospyris borealis and 4 deep water species which have maxima between 1000 and 2000 m cycladophora davisiana and actinomma boreale only a few specimens of a boreale were found in the water column ranging from 1000 to 2000 m depth although this is a dominant species in surface sediments from depths below 2000 m of which the dominance increases with water depth a boreale may live mainly in the bottom water cycladophora davisiana and a boreale which characterize the japan sea deep assemblage are naturally shallow or intermediate dwellers in other oceans on the other hand the typical deep dwellers e g cornutella profunda cyrtopera languncula and peripyramis circumtexta of other oceans have not been found in the japan sea such a peculiar deep assemblage is a result of the deep circulation system in the japan sea and the shallow depths of the sills around it

evidence for nonlinear coupling of planetary waves and tides in the antarctic mesopause analyses of hourly mean meridional and zonal winds near 95 km observed with the meteor radar system at molodezhnaya station 68 s 45 e during 1990 reveal the presence of long period 2 18 day waves with dominant periods corresponding to those of rossby normal modes modified by mean zonal winds time varying analyses indicate that although significant contributions at planetary wave periods persist with nearly constant periods for intervals of days to weeks temporal variability of these periods is observed over longer intervals tidal motions which mainly consist of the semidiurnal and the diurnal periods demonstrate considerable modulation of their amplitudes that vary with time the observed tidal amplitude modulations are investigated through bispectral analyses the results of these analyses suggest nonlinear interactions of quadratic form between oscillations with periods in the range of 2 to 19 days and the diurnal and semidiurnal tides at various intervals during 1990

satellite observations of thermospheric tides results from the wind imaging interferometer on uars thermospheric winds measured by the wind imaging interferometer windii on the upper atmosphere research satellite are analyzed for migrating solar tides the data cover a 2 year period commencing february 1992 and are obtained from the atomic oxygen o 1s 557 7 nm emission which provides observations of the 90 to 200 km altitude range during daytime and the 90 to 110 km range at night the subtropical lower thermosphere is dominated by the diurnal propagating tide which exhibits a vertical wavelength of approximately 22 km grows in amplitude up to 95 km and decays rapidly above where molecular diffusion greatly reduces the vertical shears although the phase remains fairly uniform throughout the year a pronounced semiannual oscillation is observed in the diurnal tide amplitude at both 20 n and 20 s the meridional and zonal wind components attain their maximum values at equinox of approximately 70 and 40 m s respectively while the solstitial minima are nearly a factor of 2 smaller at 35 n the diurnal tide semiannual amplitude oscillation is still present in the lower thermosphere but above 100 km it is replaced by an annual cycle with a maximum in july and august this contrasts with 35 s where the july august peak is absent and the semiannual oscillation extends to 110 km at midlatitudes the zonal and meridional winds are of similar magnitude and no significant hemispheric asymmetries in amplitudes are observed in the lower thermosphere the semidiurnal tide amplitude exhibits an annual oscillation with maximum values of 30 to 40 m s occurring in june july near 100 km at 35 n 35 s and the equator a bimodal structure in the seasonal variation of the semidiurnal phase is observed this feature is characterized by rapid equinoctial transitions and is particularly well defined at the equator examination of the equatorial middle thermosphere indicates that the semidiurnal tide attains its maximum amplitude at 140 km and exhibits a vertical wavelength of approximately 60 km these findings indicate the predominance of the antisymmetric 2 3 hough mode in the tropics

terdiurnal tide in the extended canadian middle atmospheric model cmam 1 we use the extended canadian middle atmosphere model cmam a general circulation model gcm to investigate the nature of the terdiurnal tide temperature and horizontal winds from a model run are analyzed to delineate the character of this tide for zonal wave numbers s 5 to 5 descriptions of the annual mean amplitudes seasonal variations and total tide superposed from the migrating and 10 nonmigrating components are provided the amplitudes and vertical wavelengths of the various components and the total terdiurnal tide are found to depend strongly on season latitude and altitude the migrating terdiurnal component maximizes at mid and high latitudes with significant amplitudes annual mean amplitude in wind temperature 10 m s k in the upper mesosphere and lower thermosphere mlt region between 80 and 100 km maximum amplitudes occur in winter in both hemispheres whereas above 100 km maximum amplitudes occur during solstices for the zonal wind field the nonmigrating terdiurnal components te5 te3 te4 tw4 and tw5 tend to peak at 50 n s with amplitudes between 2 and 8 m s the other nonmigrating components maximize in the polar regions with amplitudes of 2 10 m s possible generation mechanisms solar heating and nonlinear interactions for the migrating terdiurnal tide in the mlt region are also examined correlation analysis indicates that nonlinear interactions between the migrating diurnal and semidiurnal tides are unlikely to be the source of the migrating terdiurnal tide

coordinated observations of 8 and 6 hr tides in the mesosphere and lower thermosphere by three meteor radars near 60 s latitude

a shallow attenuating anomaly inside the ring fracture of the valles caldera new mexico abstract spectral ratios of teleseismic direct and scattered p waves observed in the valles caldera new mexico show a systematic pattern of low amplitudes at sites inside the caldera relative to sites on or outside the ring fracture waveforms recorded at caldera stations are considerably more complex than those recorded outside the caldera the data used in this study were collected during a passive seismic monitoring experiment conducted in 1987 twenty four teleseismic events were recorded on two linear arrays spanning the caldera to first order the pattern of low amplitudes did not vary with source incidence angle or azimuth of approach and could not be explained by anomalous amplification at the ring fracture this observation suggests the presence of a shallow attenuating zone associated with the caldera fill material inside of the ring fracture we estimated the general features of the caldera s near surface structure for the two dimensional vertical cross section beneath the array using a modification of the aki larner discrete wavenumber method to forward model the observed amplitude variations our results indicate that the caldera fill material must be subdivided into at least two distinct zones a strongly attenuating lower zone extending to depths in excess of 4 km and a mildly attenuating surface layer to fit the data we had to assign an unrealistically low value to seismic q in the deeper attenuating anomaly we attribute this to the inability of the aki larner method to account for strong re direction of energy away from the caldera due to local heterogeneity that we could not include within the low q anomaly this interpretation is consistent with the pervasive fractured hydrothermal system that is known to exist in the caldera fill material

geothermal resources of rifts a comparison of the rio grande rift and the salton trough the rio grande rift and the salton trough are the best developed rift systems in the united states and both share many features common to rifts in general including geothermal resources these two rifts have different tectonic and magmatic histories however and these differences are reflected in the nature of their geothermal resources the salton trough is a well developed and successful rift it is the landward extension of the gulf of california spreading center which has separated baja california from the remainder of mexico quaternary silicic magmatization has occurred and several of the geothermal resources are associated with recent rhyolitic intrusions such resources tend to be high temperature 200 c greenschist facies metamorphism has been observed in several of the geothermal wells localized upper crustal melting is a distinct possibility and there is increasing speculation that very high temperature 300 c geothermal fluids may underlie a large portion of the central trough at depths in excess of 4 km low temperature geothermal resources associated with shallow hydrothermal convection are less common and tend to be located on the flanks of the trough or in the coachella valley to the north of the zone of active rifting in contrast the rio grande rift is less well developed recent volcanism consists primarily of mantle derived basalts which have not had sufficient residence time within the crust to generate significant crustal melting the geothermal resources within the rio grande rift do not correlate well with these young basalts rather the quantity of geothermal resources are low temperature 100 c and result from forced hydrothermal convection which discharges at constrictions within or at the end of the major sedimentary basins high temperature resources are less common and the only discovered example is the valles caldera of northern new mexico t 250 300 c the deep interiors of the sedimentary basins of the rio grande rift do not appear to be major geothermal exploration targets

incoherent scatter radar study of the terdiurnal tide in the e and f region heights at arecibo 1 we report the analysis of the terdiurnal tide in the meridional wind from 90 to 350 km at a low latitude station our data is based on nine days of consecutive observation made by the arecibo incoherent scatter radar during january 14 23 2010 the terdiurnal tide is observed to be prominent at e region heights in the first four days jan 14 18 and at the f region heights in the last five days jan 18 23 the terdiurnal tide is among the two strongest tidal components in both regions the vertical wavelength of the terdiurnal tide is about 100 km and 950 km for the altitude range of 128 to 142 km and 180 to 320 km respectively the f region terdiurnal tide amplitude is found to be well correlated with the background meridional wind in the lower f region our analysis does not reveal any evidence that non linear interaction between diurnal and semidiurnal tides is important for the f region terdiurnal tide

global structure and seasonal and interannual variability of the migrating diurnal tide seen in the saber timed temperatures between 20 and 120 km 1 the present paper is focused on the global spatial altitude and latitude structure and seasonal and interannual variability of the migrating diurnal tide derived from the sounding of the atmosphere using broadband emission radiometry thermosphere ionosphere mesosphere energetics and dynamics saber timed temperature measurements for 6 full years january 2002 to december 2007 the tidal results are obtained by a new analysis method where the tides migrating and nonmigrating and the planetary waves zonally traveling and stationary are simultaneously extracted from the satellite data it has been found that above 70 km height the saber migrating diurnal tide reflects mainly the distinctive features of the first symmetric propagating 1 1 mode while below this height it reflects the features of the first symmetric trapped 1 2 mode the trapped component amplifies near 50 km and its phase is close to 1600 lt the seasonal behavior of the diurnal tide over the equator is dominated by semiannual variation with a primary maximum in february march 18 k average amplitude for 6 years and a secondary maximum in august september 15 k the tidal amplitude grows rapidly in the mesosphere lower thermosphere however it undergoes some decay near 90 km defining ubiquitous double peaked vertical structure a very rapid reduction in amplitude is detected at heights near 115 km however above this level the diurnal tide amplifies again the vertical wavelength of the propagating diurnal tide is 20 km over the equator at middle latitudes it is not very different from that over the equator but its magnitude depends on the season in the winter it is longer than that in summer the interannual variability of the diurnal tide indicates a clear correlation with the stratospheric quasi biennial oscillation

comparison of the auroral e region neutral winds derived with the european incoherent scatter radar and predicted by the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model a comparison study of the auroral e region neutral wind has been conducted using the european incoherent scatter eiscat radar observations and thermosphere ionosphere mesosphere electro dynamics general circulation model time gcm predictions the daily mean wind data as well as diurnal and semidiurnal tidal wind data are compared for the three seasons summer equinox and winter between 95 and 119 km fairly good agreement is found in the altitude profile of the mean zonal wind between the eiscat observation and the time gcm prediction for summer indicating the parameterization of gravity waves employed in the time gcm is adequate for this feature the meridional mean wind amplitude predicted by the time gcm is considerably smaller than that observed by eiscat and the predicted wind is slightly northward for all the seasons above 100 km generally good agreement is found for the amplitude of the diurnal tide especially the summer prediction while disagreements between the model and observational results are found for the corresponding phases the semidiurnal amplitude predicted by the time gcm is much smaller than that observed by eiscat and relatively large differences of the semidiurnal phase between the observations and predictions are found for all seasons these comparison results suggest that further advancements in the gravity wave parameterization as well as the addition of planetary wave effects are needed to predict more realistic lower thermospheric winds at high latitude

on the occurrence and variability of the terdiurnal tide in the equatorial mesosphere and lower thermosphere and a comparison with the kyushu gcm 1 we studied the occurrence characteristics and variability of the terdiurnal tide 8 hour period in the equatorial mesosphere and lower thermosphere mlt using a meteor radar at koto tabang 0 2 s 100 3 e and mf radars at tirunelveli 8 7 n 77 8 e and pameungpeuk 7 4 s 107 4 e these locations one being located right over the equator and the other two at conjugate points around the equator within 10 form a unique experimental setup to study equatorial mlt dynamics the terdiurnal tide exists as a distinct wave signature at all three locations while the daily amplitudes can be as large as 15 m s 1 the monthly mean amplitudes lie between 1 and 10 m s 1 the amplitude of the terdiurnal tide at pameungpeuk is generally smaller than that observed at tirunelveli and koto tabang the seasonal variation in amplitude shows both annual and semiannual oscillations of 1 m s 1 at all three locations the present observations combined with previous reports indicate that the timing of the primary maximum of the terdiurnal tide amplitude shifts from autumn to late spring and early summer as one moves from high latitudes to the equator all with respect to the northern hemisphere the amplitudes and seasonal variation in the present observations show good comparison with that simulated by the general circulation model gcm developed by kyushu university japan this study supports the occurrence of nonlinear interaction between diurnal and semidiurnal tides and shows that gravity waves play an important role in the generation of the terdiurnal tide

the use of tritium in groundwater to determine fluid mean residence times of valles caldera hydrothermal fluids new mexico usa abstract naturally and artificially produced 3 h in precipitation is used to place limits on mean residence times of fluids associated with the valles caldera geothermal reservoir the 3 h concentrations in precipitation are used to calculate fluid mean residence times using two end member cases piston flow and well mixed reservoirs these simplified models using 3 h yield relative fluid mean residence times in different portions of the system in situ 3 h production in the reservoir through neutron interaction with 6 li is considered and only very low levels of 3 h 0 01 t u are contributed to the waters by this process calculations using the end member cases at valles caldera indicate that mean residence times of geothermal waters in the reservoir are between 3000 and 10 000 years the results also show that the two distinct subsystems of the main reservoir are associated with different fluid mean residence times waters in the redondo creek subsystem are older 4300 to 10 000 years than waters in the sulphur springs subsystem 2000 4400 years comparison of the results of the end member cases with those obtained using more sophisticated methods indicates that the two end member cases with the use of 3 h can provide acceptable limits order of magnitude on a fluid s mean residence time and volumes within a reservoir

paleoceanography and the diachrony of radiolarian events in the eastern equatorial pacific the development of an orbitally tuned time scale for the odp leg 138 sites provides biostratigraphers a very high resolution chronostratigraphic framework with this framework we are better able to define which of the first and last appearances of species appear to be synchronous in addition the geographic distribution of sites provides the means with which the detailed spatial patterns of invasion of new species and the extinction of older species can be mapped these maps not only provide information on the process of evolution migration and extinction they can also be related to water mass distributions and near surface circulation of the ocean of 39 radiolarian events studied at 11 sites in the eastern equatorial pacific 28 were found to have a minimum range in their estimated age that exceeded 0 15 m y the temporal pattern of first and last appearances of these diachronous events have coherent spatial patterns that indicate shifts in the areas of high oceanographic gradients over the past 10 ma these changes in the locations of high gradient regions suggest that the south equatorial current sec was north of its present position prior to approximately 7 ma there was a southward shift in the northern boundary of this current between approximately 6 and 7 ma and the development of a relatively strong gradient between the northeastern and northwestern sites between approximately 3 7 and 3 4 ma there was a very slight northward shift in the northern boundary of the sec and the steep gradients between the northeastern and northwestern sites may have disappeared this change is thought to be associated with the closing of the isthmus of panama the temporal spatial patterns of diachronous events younger than 3 4 ma are consistent with patterns of circulation in the modern ocean

biogenic and abiogenic components of laminated hemipelagic sediments in the central gulf of california abstract alternating light and dark submillimeter to millimeter thick layered sediments rhythmites are found along the slopes of the central and southern gulf of california where a strong oxygen minimum zone intersects the sediment water interface two short intervals of distinct alternations were sampled lamina by lamina from two cores in the central gulf both cores are from the slope of the guaymas basin one core is from the mainland side the other core is from the baja side each lamina sample was analyzed for its opal micro floral assemblage textural character trace metal and bulk chemical cu mn fe ni zn ca k al sio2 and c org content and mineralogy on both sides of the gulf the light laminae contain more diatom frustules up to 90 and less terrigenous and organic material than the dark laminae the sediment is predominantly silt sized the dark laminae contain more terrigenous material which is primarily clay size on both sides of the gulf the light laminae apparently represent sedimentation during the dry winter season of northwesterly winds whereas the dark laminae represent the wet summer season of southeasterly winds

structure of the terdiurnal tide at 95 km satellite wind observations from the high resolution doppler interferometer hrdi instrument on the upper atmosphere research satellite uars are used to describe the latitudinal structure and seasonal variation of the terdiurnal 8 hour atmospheric tide at 95 km the amplitude of the annual average tide is 5 m s meridional and 15 m s zonal within the range observed 60 s to 60 n the maximum amplitudes are found during fall and winter at midlatitudes only weak temporal correlations with the diurnal and semidiurnal tides are seen on the monthly time scales resolved

global distribution and interannual variations of mesospheric and lower thermospheric neutral wind diurnal tide 1 migrating tide 1 using the timed doppler interferometer tidi mesospheric and lower thermospheric neutral wind multiyear data set 2002 2007 and ncar time general circulation models gcm 1 2 annual run results 2002 2005 at the tidi sampling points we study the migrating diurnal tide s global distribution interannual and seasonal variations in connection with the mean zonal wind interannual variations a strong quasi biennial oscillation qbo effect on the diurnal tide was observed in the tidi data and reproduced to a lesser degree in the time gcm run the migrating diurnal tide amplitude is larger during the eastward phase of the stratospheric qbo and weaker during the westward phase westward mesospheric equatorial mean zonal winds appeared during the eastward phase of the stratospheric qbo in 2002 2004 and 2006 the strongest qbo effect on both the migrating diurnal tide and mean zonal winds was observed during the march equinox the stronger tides may be related to the weaker gravity wave filtering in the stratosphere during the eastward phase stratospheric qbo the tidi data also exhibit large interhemispheric asymmetry the westward mean zonal winds in the mesosphere appeared to be associated with the enhanced diurnal tide the time gcm 1 2 diurnal tide amplitudes are in general smaller than those observed by the tidi instrument limited vertical spatial resolution for the time cgm 1 2 is suggested as the cause future improvements are expected with a higher spatial resolution in the model