jean andre de luc and nature s chronology abstract jean andre de luc or deluc 1727 1817 who first proposed the term geology almost in its modern sense was one of the most prominent geologists of his time his theory of the earth published in several versions between 1778 and 1809 divided geohistory in binary manner into two distinct phases the fossiliferous strata had been formed during a prehuman ancient history of immense but unquantifiable duration then the present continents had emerged above sea level in a sudden physical revolution at the start of the earth s modern history of human occupation de luc argued that the rates of actual causes or observable processes erosion deposition volcanic activity etc provided natural chronometers that proved that the modern world was only a few millennia in age and he identified the natural revolution at its start as none other than the flood recorded in genesis so nature s chronology could be constructed from natural evidence to match the well established historical science of chronology based on textual evidence from ancient cultures de luc s natural chronology was restricted to the recent past but it provided a template for later geologists to develop a geochronology extending into the depths of geohistory the historical importance of de luc s work has only been obscured by the myth of intrinsic conflict between science and religion

marine controlled source electromagnetics with geothermal purposes central gulf of california mexico abstract we acquired and interpreted data from two controlled source electromagnetic profiles in the gulf of california off the coast of santa rosalia baja california sur mexico this area is interesting from the geothermal point of view due to its proximity to the guaymas basin the la reforma caldera and the las tres virgenes volcano the first with intense submarine hydrothermal manifestations and the final one with a geothermal field in production the survey consisted of the deployment of 10 ocean bottom electromagnetic receivers distributed along two 14 km long profiles these sensors recorded the two horizontal components of the electric and magnetic fields the source consisted of a horizontal 200 m electric dipole towed behind the vessel the processed data were inverted to estimate the subsurface distribution of electrical resistivity using a finite element two dimensional multi frequency program resulting in adequate fits between observed and calculated data to estimate how well the models are constrained by the data sensitivity tests were applied to the models the tests were based on the jacobian matrix and a perturbation analysis of selected features of the model they show that the model in its central part is well constrained by the data down to a depth of about 2 5 km with the perturbation approach 16 resistivity features out of the 19 tested turned out to be well constrained by the data the estimated resistivity distribution was compared with the information obtained from other geophysical methods bathymetry gravity and 2d multi channel seismic reflection resulting in reasonably good correlations between them for the first profile we find a remarkable similarity with the current conceptual models proposed in the literature for a volcanic geothermal system where an altered conductive clay cap overlays another with higher electrical resistivity the second profile shows agreements with anomalies detected with echo sounder bathymetry suggesting the existence of hydrothermal manifestations

large scale dynamics of the mesosphere and lower thermosphere an analysis using the extended canadian middle atmosphere model the extended canadian middle atmosphere model is used to investigate the large scale dynamics of the mesosphere and lower thermosphere mlt it is shown that the 4 day wave is substantially amplified in southern polar winter in the presence of instabilities arising from strong vertical shears in the mlt zonal mean zonal winds brought about by parameterized nonorographic gravity wave drag a weaker 4 day wave in northern polar winter is attributed to the weaker wind shears that result from weaker parameterized wave drag the 2 day wave also exhibits a strong dependence on zonal wind shears in agreement with previous modeling studies in the equatorial upper mesosphere the migrating diurnal tide provides most of the resolved westward wave forcing which varies semiannually in conjunction with the tide itself resolved forcing by eastward traveling disturbances is dominated by smaller scales nonmigrating tides and other planetary scale waves play only a minor role in the zonal mean zonal momentum budget in the tropics at these heights resolved waves are shown to play a significant role in the zonal mean meridional momentum budget in the mlt impacting significantly on gradient wind balance balance fails at low latitudes as a result of a strong reynolds stress associated with the migrating diurnal tide an effect which is most pronounced at equinox when the tide is strongest resolved and parameterized waves account for most of the imbalance at higher latitudes in summer this results in the gradient wind underestimating the actual eastward wind reversal by up to 40

hydrothermal mounds and young ocean crust of the galapagos preliminary deep sea drilling results leg 70 a total of 32 holes at 5 sites near 1 n 86 w drilled on deep sea drilling project dsdp leg 70 november december 1979 provide unique data on the origin of the hydrothermal mounds on the south flank of the galapagos spreading center hydrothermal sediments primarily mn oxide and nontronite are restricted to the immediate vicinity of the mounds 100 m and are probably formed by the interaction of upward percolating hydrothermal solutions with sea water and pelagic sediments above locally permeable zones of ocean crust mounds as much as 25 m in height form in less than a few 10 5 yrs and geothermal and geochemical gradients indicate that they are actively forming today the lack of alteration of upper basement rocks directly below the mounds and throughout the galapagos region indicates that the source of the hydrothermal solutions is deeper in the crust

biogeography of planktonic foraminifera and regional carbon isotope variations productivity and water masses in late cretaceous europe the first appearances of species of marginotruncana planktonic foraminifera are found stratigraphically earlier in boreal northwestern germany than in the tethys helvetoglobotruncana helvetica bolli is rare in northwestern germany and common in the tethys its stratigraphic range is probably comparable between both areas the biogeographic patterns are discussed with respect to influences of water depths based on isotope evidence for the depth distribution of species of hedbergella praeglobotruncana and rotalipora and water temperatures the regional variation of 13c values of cenomanian turonian pelagic carbonates was mapped for the european epicontinental basins and the southern european shelf helvetic zone of the alps the highest 13c values up to 5 were found in northwestern germany and the eastern north sea and are coincident with an upwelling zone numerically predicted by three independent climate models intermediate values in france and england 2 4 correspond to predicted weak upwelling lowest values occur in the alpine helvetic zone and the south german regensburg area 1 2 and coincide with predicted absence of upwelling the 13c values are interpreted as indicators of increased biogenic productivity in the upwelling zone semiquantitative nannofossil data suggest abundance patterns influenced by latitude neritic oceanic gradients and productivity observations agree with east to west wind driven surface current systems regional differences in nutrient supply and subsequently different primary productivity could have been a major factor controlling the evolution and the biogeographic distribution of planktonic foraminifera in cenomanian turonian europe

pore pressures and permeabilities measured in marine sediments with a tethered probe a new probe for measuring pore fluid pressures in marine sediments has been constructed and tested in two hydrologic environments on the juan de fuca ridge the instrument utilizes a highly incompliant high sensitivity differential pressure transducer and a small 4mm diameter sensing probe that telescopes within a larger diameter 1 5 m long currently 2 5 m strength member the small probe diameter and the low compliancy serve to minimize the time required for pressures to approach equilibrium after penetration observed decay times are short enough to permit the instrument to be used in a tethered mode the mechanical configuration enables the small diameter probe to penetrate the sediments without buckling and to be pulled out without bending this allows multiple penetrations to be completed during a single instrument lowering ten measurements were made during the development and testing of the instrument in fine grained turbidite sediments on the juan de fuca ridge four penetrations were uninterrupted by mechanical disturbances or instrumentational problems and although equilibrium conditions were approached during only one penetration 2 7 hours maximum undisturbed decay period all provided useful constraints on equilibrium pore pressures values at two sites where sediment cover is thick and heat flow relatively low were unresolvably different from hydrostatic values estimated from two penetrations located within a few hundred meters of a hydrothermal vent field within the sedimented axial valley of the northern juan de fuca ridge middle valley exceeded hydrostatic and yielded pressure gradients of roughly 0 5 kpa m 1 permeabilities were estimated from the rates of decay of the penetration transients values ranged from 5 10 16 to 1 10 14 m2 and agreed well with values measured on core samples collected near the probe penetrations which ranged from 8 10 16 to 1 10 14 m2 using the values determined from the probe measurements from middle valley the implied rate of fluid flow upward through the sediments in the vicinity of the vent field is roughly 5 10 10 m s 1 or 15 mm yr 1 with the current practical limit of resolution of roughly 10 10 m s 1 3 mm yr 1 this direct measurement technique provides a means of determining pore fluid flow rates that is roughly 1 order of magnitude more sensitive than the method of estimating the rate of flow from the perturbation of the conductive thermal regime measured by typical marine heat flow instruments

diagenesis of sandstones in the back arc basins of the western pacific ocean sandstones occur in back arc basins of the western pacific at dsdp sites 299 sea of japan 297 northern shikoku basin 445 and 446 daito ridge and basin province 453 mariana trough 286 new hebrides basin and 285 south fiji basin these sandstones are dominantly volcaniclastic arenites derived from andesitic island arcs the degree of sandstone diagenesis is dependent on original composition burial rate heat flow history of the basin and timing of sandstone deposition with respect to rifting processes and associated high heat flow sandstones containing a larger proportion of volcaniclastic components showed more diagenetic effects than sandstones containing a significant volume of other rock fragments and mineral components sandstones deposited during early stages of rifting sites 445 446 with a slow burial rate and high crustal heat flow showed the greatest degree of downhole diagenetic change these diagenetic changes include early pore space reduction and rim cementation by clay minerals followed later by calcite and subsequent pore fill cementation by clinoptilolite heulandite analcite and later calcite replacement of recognizable volcanic rock fragments by chert calcite and zeolites was observed in the deepest part of the hole sandstones deposited after rifting under conditions of associated lower heat flow showed considerably less diagenetic changes particularly if burial was rapid the high heat flow associated with earliest rifting associated fluid circulation driven by thermal convection and slow burial rate controlled the diagenetic history of these sandstones thus timing of sandstone deposition with rifting stage and associated burial rates were key factors in controlling sandstone diagenesis in back arc basins

observations of the two day wave in windii data during january 1993 analysis of variations in the zonal and meridional wind observed by the wind imaging interferometer windii on the upper atmosphere research satellite uars from january 19 to january 31 1993 reveal a strong quasi two day wave qtdw signature these observations were taken during the time of peak amplitude for this qtdw event wu et al 1993 and extend from 41 n to 71 s daytime and nighttime results are presented for the altitude ranges 90 to 150 km and 90 to 102 km respectively the qtdw is found to occur with significant amplitude well into the winter hemisphere and lower thermosphere its latitudinal structure below 103 km is found to be similar to that calculated by hagan et al 1993 using the background wind profile of portniagin and solov yeva 1992 the peak amplitude occurs at 94 km with a magnitude of about 50 m s for the meridional wind and 30 m s for the zonal wind mean profiles from the summer midlatitudes show a secondary maximum in amplitude near 115 km and a node at 130 km above 130 km the wave appears to be evanescent

horizontal structure of the geomagnetic 2 day variation 1 principal component analysis was applied to 30 year geomagnetic field data of six observatories in low latitudes to extract the longitudinal structure of the geomagnetic 2 day variation it was revealed that characteristics of the 2 day variation agree well with those of the quasi 2 day wave observed in the middle atmosphere it propagates westward with a zonal wave number 3 and the monthly mean amplitude of the variation is largest in january and july in addition an investigation into the latitudinal profile of the variation clarified that the amplitude of the 2 day variation is largest in the equatorial region although it extends to the middle latitudes a previous result of spherical harmonics analysis of geomagnetic field data was reanalyzed to identify the global horizontal pattern of overhead currents responsible for the geomagnetic 2 day variation the results showed that the 2 day variation is attributed to westward propagating current vortices the foci of which are located along the equator all these features can be explained by a scenario in which there exists a 2 day wave in the ionosphere whose horizontal structure and temporal variation resemble those in the middle atmosphere and the wind drives electric fields and currents in the ionosphere through dynamo action

amplitude phase and period variations of the quasi 2 day wave in the mesosphere and lower thermosphere over london canada 43 n 81 w during 1993 and 1994 because there is as yet no conclusive evidence pointing to the source of the quasi 2 day wave further observations are required in order to resolve questions about the generating mechanism as well as to better understand the role of the wave in the middle atmosphere in this paper we investigate the period amplitude phase and vertical wavelength for the quasi 2 day wave in the mesosphere and lower thermosphere using the university of western ontario 2 mhz radar near london canada and in addition we look at possible coupling with atmospheric tides the results of the present study bring out certain new aspects of the quasi 2 day wave at midlatitude in the northern hemisphere that have not been previously reported in particular we show that the period of the quasi 2 day wave determined from our study is smaller 46 47 hours than the 51 to 52 h period generally suggested by other northern hemisphere results and our periods also showed variability as a function of time we also draw attention to the annual variability and especially highlight the occurrence of the wave in nonsummer months for example a brief occurrence in april is not uncommon our study also contributes additional midlatitude geographical data that should aid in developing a better picture of the quasi 2 day wave

oblique propagation of monsoon gravity waves during the northern hemisphere 2007 summer we present a combination of satellite observation and high resolution model output to understand monsoon convection as a source of high latitude mesospheric gravity waves gws the gws generated over the northern hemisphere nh monsoon region during the 2007 summer and the role of the winds in focusing these gws toward the high latitude middle atmosphere are analyzed using the saber timed satellite temperature data and the high resolution nogaps alpha model results in the nh above the stratosphere the monsoon gw momentum flux gwmf exhibits a poleward tilt that follows the slanted structure of the easterly jet the correlation coefficients 0 5 between the time series of nh tropical stratospheric gwmf and the global winds also have a slanted structure that coincide with the easterly jet confirming the modeling theory that stratospheric monsoon gws are refracted into the summer easterly jet and can reach the high latitude mesosphere since polar mesospheric clouds pmcs are sensitive indicators of changes in the polar summer mesosphere we compared the time series of tropical stratospheric gwmf to the pmc occurrence frequency of obtained from the cips aim satellite data to assess the influence of this wave focusing in the mesosphere there is a significant positive correlation between the high latitude pmc of and the tropical stratospheric gwmf suggesting a definite influence of monsoon gws on the high latitude mesosphere the disagreement in correlation at the end of the pmc season is attributed to the enhancement of the quasi 5 day planetary wave dominating over the influence of monsoon gws on pmcs

estimation of lateral hydrothermal flow distance from spatial variations in oceanic heat flow measured heat flow in young oceanic crust is generally less than predicted by lithospheric cooling models even where thick sediments had been expected to isolate the crust from the ocean and hence eliminate hydrothermal heat transfer at isolated sites with basement outcrops or topographic highs however heat flow sometimes exceeds the model predictions it thus appears that water migrates and upwells at distant sites hence transferring heat laterally simple estimates of the lateral flow distance can be made when heat flow data have adequate areal sampling the data can be parametrized by distance from the presumed upwelling site and integrated to estimate the area from which heat must be transferred along the juan de fuca ridge the minimum effective lateral flow distances are 8 km for 3 5 ma crust and 2 km for younger 1 ma crust

two day wave observations of uars microwave limb sounder mesospheric water vapor and temperature 1 a two day wave disturbance is observed in the mesospheric temperature and water vapor on the basis of new version data from the upper atmosphere research satellite microwave limb sounder using two data segments during the austral summers january february of 1992 and 1993 and the asynoptic mapping method a strong wave signal is identified as having zonal wave number 3 and a westward period of about 2 1 days the wave amplitudes are located near the core of the summer easterly jet with strongest wave amplitudes as large as 11 k and 0 35 part per million by volume near the mesopause the temperature and water vapor wave strengths are highly correlated in time but their peaks are almost longitudinally out of phase poleward heat flux associated with upward wave energy propagation in the southern hemisphere points to baroclinic instability as the cause for the wave appearance a growing wave signature in water vapor is observed in regions of strong meridional gradient of water vapor near the mesopause wave breaking is suggested as moist polar air is displaced into the much drier subtropics and wave amplitude decays

verification of large scale rapid transport in the lower thermosphere tracking the exhaust plume of sts 107 from launch to the antarctic 1 new analysis of the doppler shift of o2 airglow spectra recorded by the timed doppler interferometer tidi and the high resolution doppler imager hrdi have provided conclusive evidence that the shuttle main engine exhaust plume generated in the lower thermosphere by the launch of sts 107 and imaged by the global ultraviolet imager guvi instrument on timed was transported to the antarctic in 80 h supporting a key inference from the initial study by stevens et al 2005 these new results were aided by improved knowledge of the effects of instrumental and satellite artifacts imposed on the doppler spectra sts 107 launched on 16 january 2003 and the neutral wind near its launch trajectory and nearby volume was sampled within minutes by tidi these initial observations suggested that the northernmost end of the shuttle s exhaust plume would move northeast and that the southern end would move southeast motions that were identified in imagery acquired during the next orbit of timed the direction and magnitude of plume motion inferred from guvi images obtained 12 26 and 50 h after launch were again confirmed by tidi and hrdi the appearance of the plume over the antarctic 80 h after launch inferred from earlier work by the appearance of iron ablated from the shuttle s main engines was consistent with neutral winds measured by the satellite doppler instruments over the antarctic the transport of the plume from the coast of florida to the antarctic was aided by the favorable phase and strong amplitude of a 2 day planetary wave of wave number three in the southern hemisphere on 18 january 2003 the existence of the 2 day wave was deduced from zonally averaged and combined tidi and hrdi neutral wind observations we conclude that the existence of strong and sustained winds in the mlt significantly greater than expected from empirical and theoretical models is indisputable and provides compelling evidence supporting the global scale nature of thermospheric winds with magnitude greater than 100 m s observed by larsen 2002 from 40 years of sounding rocket chemical release experiments

longitude structure of the ionosphere f region from topex poseidon and ground based data during january 20 30 1993 including the quasi 2 day oscillation the global structure of the f region ionosphere during january 20 30 1993 is examined with emphasis on longitudinal variations the database consists of total electron content tec measurements from the topex poseidon dual frequency altimeter experiment from 66 to 66 geographic latitude for prenoon and premidnight conditions and hourly f o f 2 and hmf 2 values from eight ionosonde stations between 42 and 26 geographic latitude in the pacific sector the 10 day averaged daytime tec data reveal latitude versus longitude structures whose salient features are captured within 10 tec units by the 1990 international reference ionosphere iri 90 and which can be explained by dynamically induced neutral composition changes due to a combination of solar and magnetically driven circulation systems the premidnight tec data at low latitudes reveal the double banded structure of the equatorial ionization anomaly with however pronounced variations in amplitude and position as a function of geomagnetic longitude none of these features which probably reflect some combination of electric field and neutral wind effects are captured by iri 90 time series analyses of the f 0 f 2 and hmf 2 data and space time fourier spectra of the tec data reveal the presence of a quasi 2 day qtd oscillation in the ionosphere which is associated with qtd wind and temperature oscillations in the mesosphere and lower thermosphere previously documented for this time period the satellite based qtd results are subject to significant caveats described herein nevertheless the topex poseidon tec data set clearly represents an important resource for global studies of ionospheric structure and plasmaneutral interactions

eliassen palm fluxes of the 2 day wave abstract high resolution doppler imager hrdi winds and temperatures are used to diagnose a 2 day wave event detected in the southern hemisphere during january 1994 a novel aspect of this study is the focus upon the wave fluxes throughout the 65 100 km range and their relationship to the background state a wave packet composed of zonal wavenumbers 2 3 and 4 propagates westward with a phase speed near 60 m s 1 the periods associated with zonal wavenumbers 2 3 and 4 are 3 5 2 1 and 1 7 days respectively the morphology of the 2 day temperature and wind fields is consistent with that of a developing baroclinic wave the divergence of the eliassen palm flux of zonal wavenumbers 2 4 is dominated by the vertical convergence of meridional heat flux the wave driving or eliassen palm flux divergence per unit mass is predominantly westward with magnitudes on the order of 5 m s 1 day 1 a steady state quasigeostrophic model of the mean meridionai circulation is used to estimate the mean wind respon

crustal processes at spreading centers recent discoveries and research on mid ocean ridges mor s in the last four years have greatly increased our knowledge of this fundamental type of plate boundary the last iugg review of mor research was in 1975 aumento et al 1975 and its omission as a topic in 1978 may have reflected a feeling that spreading centers were reasonably well understood since that time however there has been a surfeit of important new observations and exciting research and there is now a turmoil of innovative ideas about the processes which create and leave their imprint on two thirds of the earth s crust new seismic measurements have been made and interpreted as evidence for the existence of shallow axial magma chambers amc beneath intermediate total opening rate 5 9 cm yr and fast 9 18 cm yr spreading centers fig 1 yet there is controversy as to whether they are steady state whether they persist beneath slow ridges as well in the steady state what the dimensions and shape of the chamber are its relation to oceanic crustal stratigraphy and its relation to observations in ophiolites black smoker hydrothermal vents have been discovered in the pacific spewing forth 350 c fluids blackened by polymetallic sulfide precipitates this discovery is embroiled in debate as to how long the vents last whether they occur at slow spreading rates as well whether the enormous heat flux of the vents freeze the magma chamber even at fast spreading rates their influence on geochemical balances in the ocean and the value of the sulfide deposits commercially it has been found that our initial view of mor s as two dimensional linear structures has served us well as an initial working model but must be significantly modified to account for variations in tectonic volcanic and hydrothermal activity along strike as well as for episodicity of these processes deep sea drilling project dsdp samples have raised fundamental questions about formation of the magnetic source layer hydrothermal circulation and fault mechanisms along the mor spreading centers which penetrate existing lithosphere along strike as propagating rifts have modified our views of how plate boundaries reorient themselves and how v shaped magnetic and topographic trends are formed we have also found that transform faults may modify spreading center processes for some distance away from their intersections with mor s and that rigid plate transform faults may fail to develop at fast spreading centers under certain conditions resulting in en echelon overlapping of spreading centers this review will focus on these developments and several others only example references to these topics will be given in the text and many important topics will not be discussed directly e g petrology and geochemistry mantle convection research on lithosphere older than 1 m y however i have tried to compile and have included an extensive bibliography for u s research on a broader range of mor topics for mid 1978 to mid 1982 which is the main purpose of this report pre 1978 references are occasionally included where appropriate abstracts are not included

sensitivity of mesospheric mean flow planetary waves and tides to strength of gravity wave drag a global circulation model which extends from the surface to 125 km is used to study how the strength of gravity wave drag affects the dynamics of the mesosphere the strength of gravity wave drag has a strong influence on the zonal mean state of the mesosphere in particular the magnitude and variability of the summer mesopause temperature and the shear on the top of the mesospheric jets this change in the zonal mean state strongly affects the susceptibility of the mesosphere to baroclinic and or barotropic instability and hence the formation of the 2 day wave the 2 day wave in turn interacts nonlinearly with the diurnal tide producing secondary waves and a reduction in amplitude of the diurnal tide previous studies with quasi linear mechanistic tidal models have captured some semiannual variation in tidal amplitude through direct interactions between tides and gravity waves our fully nonlinear global circulation model results support an alternative explanation in terms of interactions between planetary waves and tides

the tropical stratopause in the ukmo stratospheric analyses evidence for a 2 day wave and inertial circulations summary large scale atmospheric motions near the low latitude stratopause in the uk meteorological office stratospheric analyses during the northern hemisphere winter are investigated focusing in particular on the 2 day wave and inertial eddies the 2 day wave is a westward propagating planetary wave which appears recurrently in the summer subtropical upper stratosphere and mesosphere space time spectral analysis of the assimilated fields of temperature and winds and high resolution transport of water vapour reveal large amplitude breaking planetary waves in the summer subtropics principally a 2 day wave 3 and a wave 1 of a period near 7 days a region of anomalous zonal mean meridional gradient of potential vorticity also exists pointing to a barotropic instability mechanism for the origin of the 2 day wave by contrast the winter subtropics are characterized by mixing on less than planetary scales during the period considered occurring during the easterly phase of the stratospheric semi annual oscillation water vapour is mixed turbulently into gyres and drawn in narrow filaments out of the southern hemisphere the potential vorticity field displays vertically layered zonally asymmetric variations the behaviour of the model assimilated fields is supported by along track water vapour distribution observed by the microwave limb sounder aboard the upper atmosphere research satellite shows evidences for intermittent filamentary mixing in the northern subtropics and a 2 day wave signature in the summer subtropics based on these results a possible mechanism connecting the initiation of the austral 2 day wave events to strong planetary wave activity in the winter is proposed the winter planetary waves provide the background conditions for development of inertial instabilities at low latitudes of the winter hemisphere which in turn create conditions favourable for barotropic instability of the summer subtropical easterly jet

the quasi 2 day wave and spatial temporal variability of the oh emission and ionosphere 1 the quasi 2 day wave qtdw during january 2006 is investigated using sounding of the atmosphere using broadband emission radiometry saber observations of oh airglow and temperature in the mesosphere and lower thermosphere mlt and champ in situ electron density observations at an altitude of 360 km the zonal structure of the qtdw during early 2006 in the southern hemisphere mlt and low latitude ionosphere is dominated by westward propagating zonal wave number 3 w3 and eastward propagating zonal wave number 2 e2 components however the observed longitude variability is not fully described by the e2 and w3 components of the qtdw the remaining longitude variability is attributed to the presence of nonmigrating tides and secondary waves generated by the nonlinear interaction of the qtdw with migrating tides the nonmigrating tides are a combination of those that are generated in situ by qtdw tide nonlinear interactions and those of tropospheric origin that propagate upward into the mlt the results presented demonstrate that nonmigrating tides and secondary waves are of considerable importance for determining the total longitude variability during periods of enhanced qtdw activity the general similarity between the qtdw in oh airglow and temperature indicates that variations in atomic oxygen concentrations due to vertical winds during the qtdw are the primary driver of the qtdw in the oh airglow emission however there are some differences in the oh airglow and temperature that we consider to be connected to changes in eddy diffusion due to changes in gravity waves during the qtdw last although similar zonal structure of the qtdw is observed in the ionosphere the observed longitude variations are not well represented by the qtdw components indicating that nonmigrating tides play a critical role in determining longitudinal variability in the ionosphere during the qtdw the importance of nonmigrating tides in the ionosphere may be related to the relative efficiency of the qtdw and different nonmigrating tides in the generation of electric fields

provenance stratigraphic architecture and hydrogeologic influence of turbidites on the mid ocean ridge flank of northwestern cascadia basin pacific ocean abstract the northwestern edge of cascadia basin north pacific ocean is unusual because late pliocene to holocene turbidites lap onto juvenile oceanic crust of the juan de fuca ridge subsidence of the ridge flank combines with irregular westward progradation of the turbidite facies to create a stratigraphic section that coarsens and thickens upward the sand provenance is mixed individual turbidity currents have funneled into the area through several shelf slope and abyssal floor conduits including vancouver valley juan de fuca channel barkley canyon and nitinat canyon local bathymetric blockage deflection and reflection of flow paths by basement relief remobilization by intrabasinal submarine slides and debris flows episodic channel switching and sporadic overbank flooding have combined to produce erratic recurrence intervals for the turbidity currents only the tallest basement highs have remained isolated from turbidite deposition during the last 500 000 years spatial and temporal differences in sediment accumulation are important because they modulate the three dimensional responses of compaction and consolidation those changes in physical properties govern where and when hydraulic communication with the underlying basement shuts down the basal hemipelagic layer of cascadia basin transforms to an effective hydrologic seal seepage rates 1 mm yr once the sediment basalt interface is buried by 100 150 m of strata rapid accumulation of turbidites therefore accelerates the hydrogeologic conversion of igneous basement from open to sealed

temporal modulation of the four peaked longitudinal structure of the equatorial ionosphere by the 2 day planetary wave 1 observations of electron densities by the constellation observing system for meteorology ionosphere and climate in august to october 2008 have shown a prominent four peaked longitudinal structure in the height of the f2 layer hmf2 in the equatorial ionosphere the development of this ionospheric structure in daytime is found to be consistent with the forcing by the eastward propagating nonmigrating diurnal tide with zonal wave number 3 de3 it is believed that tidal winds can modify the e region electric fields and subsequently produce variations in the ionosphere through the dynamo effect this study reveals that the amplitude of the hmf2 four peaked longitudinal structure is subject to a 2 day periodic modulation on certain intervals in the two month time period simultaneously wind measurements from the skiymet meteor radar at thumba 8 5 n 77 e india indicate corresponding 2 day planetary wave activity in the mesosphere and lower thermosphere mlt the 2 day planetary wave has both zonal and meridional wind components and it is the variability in the zonal component that most closely corresponds to f2 layer changes the zonal wind observations by the radar also show that the amplitude of the diurnal tide is modulated by the 2 day wave this study suggests that the identified 2 day variation of the hmf2 four peaked longitudinal structure in the equatorial ionosphere is caused by the interaction between the de3 tide and the 2 day planetary wave

zonal wave numbers of the summertime 2 day planetary wave observed in the mesosphere by eos aura microwave limb sounder 1 recent observations and theoretical work suggest that the 2 day planetary wave in the summertime mesosphere is composed of multiple superposed zonal wave numbers here we use eos aura microwave limb sounder mls temperature data to determine the component zonal wave numbers of the 2 day wave in the mesosphere at latitudes of 70 s to 70 n from 2004 to 2009 we consider the effect of aliasing between different wave numbers and note that significant aliasing can occur and result in spurious signals particularly at high latitudes in winter the seasonal evolution of the different wave numbers is investigated and found to be very different between the northern and southern hemispheres in both hemispheres the wave is dominated by westward traveling waves of zonal wave number 3 and 4 w3 and w4 however in the southern hemisphere the wave is dominated by the w3 component but in the northern hemisphere the w3 component is smaller and the w4 component is often of similar or larger amplitude a small amplitude westward traveling zonal wave number 2 w2 wave is also evident in both hemispheres in the northern hemisphere the w2 amplitudes never exceed 3 k the w3 amplitudes can reach 3 5 k and the w4 can be the largest component reaching amplitudes of 4 k in the southern hemisphere the w2 amplitudes can reach up to 3 5 k the w3 amplitudes can be much larger reaching 12 k and the w4 amplitudes are smaller than in the northern hemisphere in 4 out of 5 years not exceeding 3 k the northern hemisphere w4 can reach large amplitudes in august when the w3 is small which means that the late summer northern hemisphere quasi 2 day wave is usually a w4 oscillation rather than the familiar w3 in contrast in the southern hemisphere the w3 is often larger than the w4 around the summer solstice and there are no episodes observed where the wave becomes dominated by the w4 for an extended period of time a high degree of interannual variability is evident particularly in the southern hemisphere where the w3 peak amplitudes vary from 12 k in january 2006 to 3 k in january 2009 the height latitude structure of the w4 suggests that this wave is a 4 0 rossby gravity wave

first observations of mesospheric dynamics with a partial reflection radar in hawaii 22 n 160 w we present here an overview of the wind measurements made during the first year of operation of a partial reflection radar system in hawaii the system operates at 1 98 mhz and provides wind estimates between 60 and 100 km at 2 km intervals our wind observations reveal a zonal mean motion that has several features in common with the mesopause semiannual oscillation msao seen at more equatorial latitudes but which is influenced as well by the seasonal variations of the mesospheric jet structure at higher latitudes major features of the zonal mean wind structure include a downward progression of strong eastward and westward phases of the msao from january to july coinciding with the period during which the msao and the annual cycle of the zonal mean wind at higher latitudes are in phase this results in an eastward maximum of 60 ms 1 near 80 km during january and february which descends rapidly and a westward maximum of 50 ms near 85 km during march and april which descends much more slowly the second msao cycle is greatly suppressed relative to the first due to the reversal of the correlation between this and the annual cycle at higher latitudes from july to december mean eastward motions occur primarily above 85 km early in this cycle and throughout the height range at later times planetary wave activity is seen to contribute substantial variability during times of eastward mean flow and to have a smaller role when zonal mean motions are westward tidal and 2 day motions are found to be large and variable with the maximum 2 day amplitudes occurring during february and august the largest diurnal tides were observed during october and november march and april and july and august while the semi diurnal amplitudes exhibited a minimum from april to june

global observations of 2 day wave coupling to the diurnal tide in a high altitude forecast assimilation system we examine wave components in a high altitude forecast assimilation system that arise from nonlinear interaction between the diurnal tide and the westward traveling quasi 2 day wave the process yields a westward traveling sum wave with zonal wavenumber 4 and a period of 16 hours and an eastward traveling difference wave with zonal wavenumber 2 and a period of 2 days while the eastward 2 day wave has been reported in satellite temperatures the westward 16 hour wave lies outside the nyquist limits of resolution of twice daily local time satellite sampling hourly output from a high altitude forecast assimilation model is used to diagnose the nonlinear quadriad a steady state primitive equation model forced by tide 2 day wave advection is used to intepret the nonlinear wave products the westward 16 hour wave maximizes in the midlatitude winter mesosphere and behaves like an inertia gravity wave the nonlinearly generated component of the eastward 2 day wave maximizes at high latitudes in the lower thermosphere and only weakly penetrates to low latitudes the 16 hour and the eastward 2 day waves are of comparable amplitude and alias to the same apparent frequency when viewed from a satellite perspective

intraseasonal and interannual variability of the quasi 2 day wave in the northern hemisphere summer mesosphere this study uses global synoptic meteorological fields from a high altitude data assimilation system to investigate the quasi 2 day wave q2dw and migrating diurnal tide during the northern hemisphere nh summers of 2007 2009 by applying a two dimensional fast fourier transform to meridional wind and temperature fields we identify q2dw source regions and diagnose propagation of q2dw activity into the upper mesosphere and lower thermosphere we find that the q2dw in nh summer is composed primarily of westward propagating zonal wave number 3 and wave number 4 components that originate within baroclinically unstable regions along the equatorward flank of the summer midlatitude easterly jet the amplitude of the wave number 3 q2dw tends to peak in july while the amplitude of the wave number 4 q2dw tends to peak in late june and again in early august the seasonal mean q2dw amplitudes are largest in 2009 when the amplitude of the migrating diurnal tide in the upper mesosphere near 30 n was relatively weak however there is no evidence of rapid amplification of the q2dw via nonlinear interaction with the diurnal tide instead variations of q2dw amplitudes during nh summer appear to be linked to variations in the strength and location of the mesospheric easterly jet from one summer to the next with a stronger jet producing larger q2dw amplitudes linear instability model calculations based on the assimilated wind fields indicate that the fastest growing modes are zonal wave numbers 3 and 4 with periods near 2 days that originate in the vicinity of the easterly jet

the galapagos spreading center at 86 w a detailed geothermal field study appendix is available with entire article on microfiche orderfrom american geophysical union 2000 florida avenue n w washington d c 20009 document j80 013 01 00 payment mustaccompany order we report here measurements of the heat flow field of the galapagos spreading center on crust of age less than 1 0 m y the 443 measurements in an area of about 570 km2 reveal the general planform of the geothermal flux and permit the first truly areal estimate of the near axis conductive heat flux the intrusion process and associated hydrothermal circulation dominate the surface heat flow pattern with circulation apparently continuing beyond the limits of our survey the areal average of the conductive heat flux is 7 1 0 8 hfu 295 33 mw m2 about one third the heat flux predicted by plate models the remaining heat is apparently removed by venting of hydrothermal waters at the spreading axis and through basalt outcrops and hydrothermal mounds off axis the pattern of surface heat flux is lineated parallel to the axis and the strongly lineated topography sharp lateral gradients in the heat flow greater than 10 hfu km near escarpments and commonly expressed as high heat flow at the tops of the scarps and lower heat flow in the valleys may indicate a local concentration of the circulation by surface fault systems and or variable sediment thickness

evidence for a traveling two day wave in the middle atmosphere evidence is presented for the existence of a wave number 3 westward traveling 2 day oscillation in the temperature measurements made by the nimbus 5 scr and nimbus 6 pmr instruments the wave has largest amplitude in the mesosphere at low latitudes of the summer hemisphere and has a markedly asymmetrical meridional structure it is suggested that the wave may be a free wave similar to the 5 day wave identified in nimbus 5 scr data by rodgers 1976 the vertical structure shows little phase tilt and a slight indication of an increase in amplitude with height

ionospheric vertical plasma drift perturbations due to the quasi 2 day wave the thermosphere ionosphere mesosphere electrodynamics general circulation model is utilized to study the vertical e b drift perturbations due to the westward quasi 2 day wave with zonal wave numbers 2 and 3 w2 and w3 the simulations show that both wind components contribute directly and significantly to the vertical drift which is not merely confined to low latitudes the vertical drifts at the equator induced by the total wind perturbations of w2 are comparable with that at middle latitudes while the vertical drifts from w3 are much stronger at middle latitudes than at the equator the ion drift perturbations induced by the zonal and meridional wind perturbations of w2 are nearly in phase with each other whereas the phase discrepancies of the ion drift induced by the individual wind component of w3 are much larger this is because the wind perturbations of w2 and w3 have different latitudinal structures and phases which result in different ionospheric responses through wind dynamo

the 2 day wave in the middle atmosphere observations and theory a recurrent global scale 2 day oscillation in the middle atmosphere is well documented in a variety of data sources meteor wind partial reflection satellite and rocketsonde the observed period is almost invariably near 2 1 days and the zonal structure has been established as a westward propagating wave number 3 mode observations also indicate that the meridional wind component maximizes near the equator and dominates the wind field at low latitudes these features suggest the disturbance s identification with the wave number 3 rossby gravity normal mode of a windless isothermal atmosphere such modes are found to exist largely independent of the mean fields the eigenperiods are only modestly altered by mean wind variations on the lowest three scale heights and the influence on the mode structure is local the vertical growth of amplitude is enhanced in regions of weak westerly wind relative to the wave and equatorward temperature gradient while the vertical growth rate is retarded and amplitudes may even decay in regions of strong westerlies or poleward temperature gradient in realistic mean fields the third rossby gravity mode has magnified responses very near 2 25 days in both equinox and solstice conditions the horizontal structure remains largely intact in the lowest levels however considerable asymmetry is introduced in the solstice upper stratosphere and mesosphere by the magnified vertical growth of amplitude in the summer hemisphere the latter results from the moderate easterlies and equatorward temperature gradient characteristic of the region as for the simple eigenstructure the meridional wind component in this region maximizes near the equator and dominates the wind field up to mid latitudes

chemical evidence for advection of hydrothermal solutions in the sediments of the galapagos mounds hydrothermal field pore water profiles of ca mg f po4 3 and mn in the galapagos mounds hydrothermal field are believed to reflect in part upwelling of hydrothermal solutions through the sediments concentration depth profiles in a low heat flow area just north of the mounds field display diagenetic changes typical of those found in pore waters underlying highly productive surface waters consistent with the inference of no water flow or very slow downwelling w 5 cm yr of bottom water through these sediments rates of upward advection calculated from mounds field pore water profiles of ca mg and f profiles agree well with each other averaging about 1 cm yr in the pelagic sediments near the mounds and 15 30 cm yr within the hydrothermal mounds themselves the upward advection also modifies the shape of po4 3 and mn profiles advection rates inferred from the pore water data are generally in reasonable agreement with those made from heat flow data the higher ca and lower mg f po4 3 and mn concentrations in mounds field pore waters compared with those of the low heat flow area suggest chemical exchange between the solution and basalt prior to upwelling li k rb sr and so4 concentrations are indistinguishable from bottom water this suggests very high effective water rock ratios during the reactions which produced the upwelling solutions perhaps due to extensive prior alteration of basalt adjacent to the flow path of water through the crust inferred reaction temperatures are between 70 150 c

the quasi 2 day wave activities during 2007 austral summer period as revealed by whole atmosphere community climate model the quasi 2 day wave qtdw observed during 2007 austral summer period is well reproduced in an reanalysis produced by the data assimilation version of the whole atmosphere community climate model waccm data assimilation research testbed developed at national center for atmospheric research ncar it is found that the qtdw peaked 3 times from january to february but with different zonal wave numbers diagnostic analysis shows that the mean flow instabilities refractive index and critical layers of qtdws are fundamental for their propagation and amplification and thus the temporal variations of the background wind are responsible for the different wave number structures at different times the westward propagating wave number 2 mode w2 grew and maximized in the first half of january when the mean flow instabilities related to the summer easterly jet were enclosed by the critical layers of the westward propagating wave number 3 w3 and wave number 4 w4 modes this prevented w3 and w4 from approaching and extracting energy from the unstable region the w2 decayed rapidly thereafter due to the recession of critical layer and thus the lack of additional amplification by the mean flow instability the w3 peaked in late january when the instabilities were still encircled by the critical layer of w4 the attenuation of w3 afterward was also due to the disappearance of critical layer and thus the lack of overreflection finally the w4 peaked in late february when both the instability and critical layer were appropriate

on modeling migrating solar tides recent updates and extensions to a steady state two dimensional linearized model of global scale atmospheric waves have facilitated improved calculations of the subset of those waves which are subharmonics of a solar day and propagate with the apparent motion of the sun the model improvements are briefly described and some updated predictions of the migrating solar diurnal component are highlighted the latter represent the first numerical modeling effort to examine the seasonal variability of the migrating diurnal harmonic as it propagates into the mesosphere and lower thermosphere

origin of elevated sediment permeability in a hydrothermal seepage zone eastern flank of the juan de fuca ridge and implications for transport of fluid and heat elevated sediment porosity and permeability may help to focus upward fluid seepage observed over a buried basement high on the eastern flank of the juan de fuca ridge consolidation and permeability tests of fine grained hemipelagic and turbidite sediments from the seepage site and from nearby sites that are not experiencing seepage indicate that sediments at the seepage site primarily hemipelagic have 10 15 higher porosity and 10 higher permeability at a given depth and 10 100 lower hydraulic impedance for the 40 m thick sediment column the correlation of consolidation and permeability properties with sediment type rather than location indicates that the relatively high porosity and permeability do not result from fluid flow but are intrinsic properties of the hemipelagic sediment on the basis of measured sediment properties fluid pressure at the top of basement is 5 kpa greater than hydrostatic a simple circulation model that incorporates this estimate and proximity to the nearest basement outcrops 4 20 km suggests that local basement permeability is between 3 10 13 and 3 10 11 m2 within the range measured in nearby boreholes the measured sediment properties combined with other published data indicate that a few tens of meters of fine grained terrigenous hemipelagic or calcareous marine sediment effectively seal the basement aquifer whereas much thicker siliceous or pelagic sediment may support thermally and chemically significant fluid flow the large contrast in hydraulic impedance among sediment columns of different types could cause regional variation in the evolution of ridge flank hydrothermal systems and in the contribution of seepage to ridge flank fluxes

coordinated global radar observations of tidal and planetary waves in the mesosphere and lower thermosphere during january 20 30 1993 a multi instrument global campaign involving incoherent scatter medium frequency and meteor wind radars was conducted during the period of january 20 30 1993 to study the dynamics of the mesosphere and lower thermosphere data obtained from 15 radar stations covering a wide latitude range have been used to determine the global distribution of planetary and tidal waves during this 10 day campaign spectral analysis of the neutral winds measured by the radars in the altitude range from 80 to 130 km indicates the existence of a strong 48 hour wave near 90 km at latitudes between 40 n and 40 s that is present up to 108 km at 18 n the semidiurnal tide is large at middle and high latitudes near 90 km and is predominant above 110 km while the diurnal tide is observed to be particularly important in the upper mesosphere near 40 latitude a least squares fit to the radar data is performed to obtain the amplitudes and phases of the tidal and 48 hour waves comparison with national center for atmospheric research thermosphere ionosphere mesosphere general circulation model shows that the predictions from the model agree reasonably well with the observed global morphology of tidal wave amplitudes

observations of the quasi two day wave in the middle and lower atmosphere over christmas island we present analyses of data collected at christmas island in the mesosphere and lower thermosphere using a meteor echo detection and collection system medac in addition to data collected in the troposphere and lower stratosphere using a clear air stratosphere troposphere st radar these data which provide 5 years of semicontinuous horizontal wind velocity estimates are analyzed to determine the temporal structure of the quasi two day wave in the middle and lower atmosphere our results show the presence of strong wave activity in the middle atmosphere during late january and early february as well as a secondary maxima in june august for each of the years we have data however the magnitude and duration of the wave events observed in late january and early february exhibit interannual variability

two day wave traveling westward with wave number 1 during the sudden stratospheric warming in january 2017 quasi two day wave qtdw propagating westward with wavenumber number 1 w1 in january 2017 is studied using global temperature observed by saber and wind observed by a meteor radar at fuke china 19 0on 109 8oe the amplitude of w1 significantly enhances during january 2017 when two stratospheric warming events occur the temperature perturbation of w1 reaches maximum amplitude of more than 6k at latitude 15o around 84 km and 95 km the structure of temperature w1 is symmetric with regard to the equator the temporal variation of w1 is consistent with the stationary planetary wave with wavenumber 2 spw2 but contrary to the qtdw propagating westward with wavenumber 3 w3 when spw2 is large during two sudden stratospheric warming events energy transfers from w3 to w1 two bursts of the two day wave in meridional wind observed by the meteor radar are just corresponding to the local maxima of w3 and w1 respectively we conclude that during january 2017 w1 is generated by the nonlinear interaction between spw2 and w3 spw2 which is modulated by the quasi 16 day perturbation in the stratosphere plays a key role in the energy transmission from w3 to w1 and it is responsible for the 16 day variation of w1

observations of the quasi 2 day wave from the high resolution doppler imager on uars a strong westward traveling oscillation with a period of 2 days and zonal wave number 3 is observed in the mesospheric and lower thermospheric winds from the high resolution doppler imager on the upper atmosphere research satellite the important events happen in january july and september october of which the occurrence in january is the strongest with an amplitude over 60ms 1 detailed analyses for the periods of january 1992 and january 1993 reveal a cause and effect relationship in the wave developing process at 95km the global structures of the wave amplitude and phase are also presented

an eastward propagating two day wave evidence for nonlinear planetary wave and tidal coupling in the mesosphere and lower thermosphere 1 temperature observations from the saber instrument on the timed spacecraft are used to investigate the structure and evolution of an eastward propagating zonal wavenumber 2 disturbance with a period near two days this oscillation obtains a maximum amplitude of nearly 10 k in the southern hemisphere mid latitudes during late january the timing and location of this planetary wave is coincident with the regular quasi two day wave intensification that occurs annually in late january the period wavenumber and spatial structure of the eastward propagating two day wave are consistent with a wave that results from a nonlinear interaction between the quasi two day wave and the migrating diurnal tide the existence of an eastward propagating wave with a period near two days coincident with the westward propagating two day wave will have an impact on the interpretation of ground based observations analysis of the saber temperature observations are utilized to determine the structure and evolution of both this eastward propagating two day wave and the classic westward propagating zonal wavenumber 3 quasi two day wave during january 2005

short term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave 1 the migrating diurnal tide is one of the dominant dynamical features in the low latitudes of the earth s mesosphere and lower thermosphere mlt region representing the atmospheric response to the largest component of solar forcing ground based observations of the tide have resolved short term variations attributed to nonlinear interactions between the tide and planetary waves that are also in the region using the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm we simulate a quasi 2 day wave qtdw event under late january conditions in this case sideband sum and difference child waves are resolved indicating that a nonlinear interaction is occurring between the qtdw and the tide the migrating diurnal tide in the mlt displays local amplitude decreases of 20 40 as well as a shortening of vertical wavelength by roughly 4 km examining the physical mechanisms driving the interaction nonlinear advection is found to result in amplification of the tide in some regions and damping in others manifesting as increased smoothing of the tidal structure when the qtdw is present in the mlt additionally the qtdw also enhances the easterly summer mean wind jet that can also account for changes in tidal amplitude and vertical wavelength we find that qtdw induced background atmosphere changes in time gcm can drive tidal variability at levels greater than nonlinear advection a possibility not previously considered

responses of quasi 2 day waves in the mlt region to the 2013 ssw revealed by a meteor radar chain we present an analysis of the responses of quasi 2 day waves qtdws to the 2013 sudden stratosphere warming ssw in the mesosphere and lower thermosphere mlt region the study is based on data collected by a meteor radar chain along the 120 e meridian in the northern hemisphere which consists of four stations at mohe 52 5 n 122 3 e beijing 40 3 n 116 2 e wuhan 30 5 n 114 6 e and sanya 18 3 n 109 6 e it is the first time that an enhancement of the qtdw in the neutral wind during the 2013 ssw is observed in the midlatitudes in the northern hemisphere during the ssw the amplification of the qtdw in the low latitudes is the most prominent and the direction of the mean zonal wind shows clear reversion from eastward to westward the consistent variations of the qtdws and the mean neutral wind at the four stations are very likely associated with the ssw

simultaneous observations of the july 1996 2 day wave event using the super dual auroral radar network and the high resolution doppler imager simultaneous observations of a 2 day wave using the super dual auroral radar network superdarn and the upper atmospheric research satellite based uars high resolution doppler imager hrdi are presented recent comparisons of superdarn data with data from the saskatoon mf radar hall et al 1997 demonstrate that superdarn data at ranges close to the radar is most likely due to scatter from meteor trails and can be used to trace neutral winds in the meteor region this study exploits this near range scatter to observe the winds during july 1996 during the study period a clear 2 day wave event was observed in both the radar data and in the hrdi data comparisons between the two data sets show similarities and distinct differences both instruments observed a wave of similar amplitude in the same time interval both instruments indicated a westward propagating wave with zonal wave number 3 hrdi observed the wave to form and diminish at earlier times than superdarn observed in addition there were distinct differences between the winds observed by hrdi at the radar longitudes and the winds observed by the radars many of the differences may be explained by the latitude difference between the radars and the northern most latitude observed by hrdi

the 6 5 day wave and its seasonal variability in the middle and upper atmosphere 1 the zonal wave number 1 planetary wave of period near 6 5 days is a robust feature in the mesosphere and lower thermosphere mlt region with prominent seasonal variability as revealed by ground based and satellite observations this wave and its seasonal variability are well reproduced in a recent one model year run of the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm with its lower boundary specified according to the national centers for environmental prediction analysis year 1993 wavelet analysis of the model output shows that in the mlt region the wave maximizes before and after the equinoxes and minimizes at solstices the wave amplitudes at the equinoxes are smaller than the peaks before and after but are still larger than the wave amplitudes at solstices however at the lower boundary near 30 km the wave peaks are predominantly between fall and the following spring by examining the episodes of maximum and minimum wave amplitude and by conducting additional control experiments using the time gcm the structure of this planetary wave and the factors determining the wave characteristics and seasonal variability are studied in detail it is found that the wave source mean wind structure instability and the critical layers of the wave can all affect the wave response in the mlt region and can have a strong seasonal dependence before and after equinox the wave follows the waveguide and propagates from the stratosphere to the summer mesosphere mesopause where it may amplify due to baroclinic barotropic instability such instability is usually absent from the equinoctial atmosphere so that there is no wave amplification at equinox at solstice the wave decays significantly when propagating away from its winter source due to the strong eastward winter stratospheric jet in the summer side the westward jet is also strong and the meridional and vertical extension of the critical layer of the wave is large enough to enclose the instability in the summer mesosphere mesopause at middle to high latitudes the wave is thus reflected away and prevented from reaching and amplifying at the unstable region the seasonal variation of the quasi two day wave which has zonal phase speed similar to the 6 5 day wave is also studied using similar diagnostics it is further shown that within certain seasonal window periods the variability in the mlt especially the summer mlt may closely track the lower atmospheric variability associated with these waves

heat transfer through the sediments of the mounds hydrothermal area galapagos spreading center at 86 w heat transfer processes at the mounds area of the galapagos spreading center at 86 w are revealed by temperatures measured at 10 m intervals in the 30 10m sediment at each of 12 holes at dsdp leg 70 sites 506 509 and by temperatures of up to five thermistors on eleven 8 12 m long piston cores the 325 needle probe values show a significant linear increase of thermal conductivity with depth in each core about half of the temperature thermal resistance profiles are nonlinear and are fit to a steady state vertical pore water advection model results indicate high and variable total heat flow and localized hydrothermal discharge at 10 8 m s associated with individual mounds recharge is indicated at similar rates in the low heat flow belt 5 km south of the mounds and is suggested at slower rates in the intermediate heat flow 0 17 0 42 w m2 belt surrounding the mounds heat flow high possible slow entrained recharge within 100 m of discharging mounds is suggested also suggested is strong local discharge along the major fault bounding the mounds crustal block to the north about 95 km north of the spreading axis at dsdp site 510 temperatures in the 114 m sediment cover on 2 7 m y crust are linear consistent with the suggestion that the hydraulic resistance of this layer is sufficient to seal off free hydrothermal exchange between basement and bottom water the combination of heat flow data and the physical properties data of karato and becker this issue suggests that 50 m of sediment may be a threshold thickness for sealing of hydrothermal circulation within basement where the topography is smooth we suggest that the formation of mounds may be associated with the forced localization of hydrothermal discharge through the sediment as its thickness approaches this threshold value

satellite observations of mean winds and tides in the lower thermosphere 1 aliasing and sampling issues 1 the canadian middle atmosphere model a general circulation model extending up to 200 km is used to analyze the impact of aliasing and data gaps on satellite observations of zonal mean winds and migrating tides in the lower thermosphere focus is placed on measurements from the wind imaging interferometer windii mock data sets are constructed by sampling daily zonal mean and migrating tides from the model like the satellite previously unverified assumptions that satellite observations of the zonal mean zonal winds and the meridional component of the diurnal tide winds are largely unaffected by aliasing are confirmed of the two the meridional component of the diurnal tide is more robust the amplitude of the zonal component of the diurnal tide is not strongly affected by aliasing tidal phase is nearly unaffected gaps in the windii data do not adversely affect the results provided sufficient local time coverage is available the analysis suggests that more subtle features in the windii observations such as the tidally driven cell like structures in the zonal mean meridional wind at low latitudes may be observable issues pertaining to the sampling interval and the use of daytime only data are also addressed sampling every second or third day provides nearly as good results as sampling every day and that using daytime only data results in substantial biases in the zonal mean zonal winds in the lower thermosphere the latter underscores the importance of the accurate removal of the migrating diurnal tide from climatologies generated from daytime only satellite data

john joly 1857 1933 and his determinations of the age of the earth abstract john joly 1857 1933 was one of ireland s most eminent scientists of the late nineteenth and early twentieth centuries who made important discoveries in physics geology and photography he was also a respected and influential diplomat for trinity college dublin and various irish organizations including the royal dublin society measuring the age of the earth occupied his mind for some considerable time a problem he was to address using a diverse range of methods his sodium method of 1899 for which he is best known was hailed by many as revolutionary but it was later superseded by other techniques including the utilization of radiometric dating methodologies although joly himself carried out much research in this area he never fully accepted the large age estimates that radioactivity yielded nevertheless joly s work in geochronology was innovative and important for it challenged earlier methods of arriving at the earth s age particularly those of lord kelvin although his findings and conclusions were later discredited he should be remembered for his valuable contribution to this important and fundamental debate in the geological sciences

porosity and hydraulic properties of sediments from the galapagos spreading center and their relation to hydrothermal circulation in the oceanic crust density and porosity of sediments were measured on dsdp legs 69 and 70 samples from the galapagos spreading center permeability and the hydraulic impedance of each sediment layer were estimated from measured values of porosity the gradients of porosity and density with depth where sediment layers are thin or approx 50 m thick are anomalously high compared with those of other areas and with the upper part of thicker sediment layers in this area a good correlation was found between the anomalous porosity and density gradients and the present day heat flow we interpret these observations to suggest that these high gradients may be due to active hydrothermal circulation through a thin sediment cover which is inhibited by a thicker sediment layer and that the pattern of hydrothermal circulation may be essentially fixed with the moving plate hydraulic impedance of the sediment layer was estimated from the observed depth variation of porosity and was shown to increase rapidly with its thickness our interpretation that a threshold thickness of about 50 m would inhibit direct diffuse discharge or recharge of hydrothermal flow through the undisturbed sediment layer yields an average permeability of the underlying basement layer of about 3 6 x 10 supmore 14 m sup 2 30 60 mdarcies less

the quasi two day wave observed in the equatorial middle atmosphere an oscillation with a period near 2 days is found in radar wind measurements made in the upper mesosphere and lower thermosphere at christmas island 2 n 157 w in the central pacific the oscillation is particularly strong in the meridional wind component and seems to be present almost continuously ir the 80 100 km height region although some intermittency is evident wave amplitudes are especially large about one month after the solstices in july august and in january february at times coincident with large 2 day wave events in the summer mesosphere at extratropical latitudes power spectral and complex demodulation techniques are used to study the amplitude and frequency variations of the oscillation as a function of height and time downward phase propagation is found consistent with upward energy propagation and with a vertical wavelength of about 70 km an unusual feature is a shift in wave period from near 50 hours in july august to 48 hours in january february when the largest amplitudes up to 45 m s 1 are observed a 16 hour oscillation is also found at times when the 2 day wave amplitudes are largest the observations are consistent with the 2 day wave being a manifestation of the 3 0 rossby gravity normal mode another weaker oscillation is also found in the meridional wind field at a period near 44 hours this oscillation may be due to the 2 0 normal mode

oceanic ridge crest processes oceanic ridge crest processes constitute a vigorous frontier of multidisciplinary research with global ramifications in the earth atmospheric and biologic sciences this deep ocean frontier is gradually opening in response to investigations which are elucidating the role of these processes in the lithosphere hydrosphere atmosphere and biosphere and the application of advanced instrumental and interpretive techniques which are increasing the quality and quantity of data these techniques include crustal drilling with borehole logging deep sea drilling project reports high resolution bathymetry sea beam etc side scan sonar seamarc i and ii gloria etc imagery with video and photography multichannel seismics determination of water column properties ctd with rosette sampler etc and submersible applications

geothermal regimes of the costa rica rift east pacific investigated by drilling dsdp ipod legs 68 69 and 70 drilling durin deep sea drilling project legs 68 69 and 70 on the southern limb of the costa rica rift was used to study geothermal processes in the ocean crust two areas were drilled one was a geothermally hot site on 6 2 m y old crust where topography is smooth heat flow is close to that predicted by conductive cooling of the lithosphere 200 mwm 2 and hydrothermal circulation may be sealed within the crust the other was on 3 9 m y old crust where rough topography is associated with low heat flow 15 to 50 mwm 2 and possible open convection of sea water at both sites about 250 m of siliceous calcareous sediments overlies igneous basement in the hot area it blankets the topography whereas in the cold area basement outcrops still occur operations included numerous down hole experiments in both areas and hydraulic piston coring of a 230 m sediment section in the hot area diagenesis of the sediments appears closely related to temperature at the hot site chert was found near basement and the chemistry of pore fluids sampled from both sediments and basement is strongly influenced by reactions within the basement strong lateral gradients in the composition of pore fluids occur in the sediments at the cold site no chert was found and bacterial processes within the sediment dominated the chemistry of the pore fluids basaltic basement in both areas consists mainly of pillow lavas and thin flows with occasional more massive units the basalt is relatively magnesian the degree of alteration is very small in the cold area but much more extensive in the hot area ease of drilling also shows a strong contrast basement penetration reached 562 m in the hot area and was halted because of lack of time at the cold site 43 m of basement was cored only with difficulty the most intensive in hole experiments were conducted in the hot area successful runs with the borehole televiewer allowed basement lithology to be determined and showed the presence of more and less fractured zones pulse tests using a single borehole packer gave values of basement permeability of about 2 to 40 millidarcies numerous temperature logs established a broadly conductive in situ temperature gradient with temperatures reaching 120 c at 562 m into the basement however anomalously low temperatures in the upper part of the hole which persisted after drilling disturbance had decayed away showed that cold ocean water was flowing down the hole and into the basement at about 90 m below the base of the sediments at rates of about 80 to 100 m hr the packer records indicate a pressure at this depth of 10 bars below hydrostatic costa rica rift united scientific team made up of shipboard participants on legs 68 501 69 and 70 who were in reverse alphabetical order

marine tectonics processes at mid ocean ridges the use of multibeam echo sounders and various side looking sonar systems has greatly increased our knowledge and understanding of mid ocean ridge mor processes since the last iugg review on mid ocean ridge research macdonald 1983 the extensive use of swath mapping tools such as sea beam deep tow seamarc i and ii the application of multichannel seismic reflection techniques to the detection of axial magma chambers and the use of satellite data in the study of oceanic lithosphere have rejuvenated marine tectonics and have generated and stimulated a large number of important contributions this review will focus on what we feel were the major developments in marine tectonics with an emphasis on mid ocean ridges in the last four years certain topics such as marine seismicity and satellite studies are only briefly mentionned for reference and will be covered in greater detail in other reviews because of the exponential growth in the number of publications related to mors during 1982 1986 only a few references pertinent to each of the major research topics will be quoted in the text as examples but the reader will find an extensive bibliography at the end of the text references published prior to 1982 were added only where appropriate

subionospheric vlf signal perturbations possibly related to earthquakes a likely vlf subionospheric signal effect related to seismic activity was first reported by hayakawa et al 1996a b in association with the great kobe earthquake we have analyzed similar data during periods around 10 other great earthquakes magnitude m 6 in order to understand the main features of such an effect the following characteristics emerged from our analysis the effect appears as a transient oscillation with a 5 to 10 day period which is initiated a few days before a large earthquake and decays over a few days to weeks after it it is mainly related to crustal earthquakes it appears when resonant atmospheric oscillations with periods in a range of 5 11 days exist before the earthquake the seismic influence on the vlf signal is probably explained by the generation of long period gravity waves during the earthquake process and their intensification at heights of 70 90 km

global distribution and variability of quasi 2 day waves based on the nogaps alpha reanalysis model this study presents the analysis of 14 months january 2009 february 2010 of continuous hourly nogaps alpha reanalysis data used for examining the quasi 2 day wave otdw the global structure and seasonal variability of the eastward and westward traveling qtdws in all meteorological fields geopotential height zonal and meridional wind and temperature have been studied the use of hourly reanalysis data allows a comprehensive understanding of the global spatial temporal qtdw distribution by simultaneous separations of all tides and planetary waves the wave characteristics amplitudes and phases are presented in latitude range 80 and altitudes from 15 to 95 km two different types of eastward traveling waves are identified i waves at middle and high latitudes with zonal wave numbers 2 and 3 which are observed in the local winters and ii waves observed predominantly over the equator with zonal wave number 2 which do not have a well defined seasonal variability but show some enhancement between june and august while the first type waves are seen in all meteorological fields the second ones are not seen in the meridional wind and belong to the ultra fast kelvin waves two different types of westward traveling waves have been identified as well i waves at middle and high latitudes with zonal wave numbers 2 3 and 4 which are observed mainly in summer hemisphere and ii waves observed predominantly over the equator with zonal wave numbers 1 2 and 3 enhanced predominantly at both solstices but are seen in other seasons as well while the first type waves are seen in all meteorological fields the second ones are observed in the meridional wind and are rossby gravity normal modes

attribution of ionospheric vertical plasma drift perturbations to large scale waves and the dependence on solar activity 1 in this study we quantify the contribution of individual large scale waves to ionospheric electrodynamics and examine the dependence of the ionospheric perturbations on solar activity we focus on migrating diurnal tide dw1 plus mean winds migrating semidiurnal tide sw2 quasi stationary planetary wave one qspw1 and nonmigrating semidiurnal westward wave one sw1 under northern winter conditions when qspw1 and sw1 are climatologically strong from thermosphere ionosphere mesosphere electrodynamics general circulation model simulations under solar minimum conditions it is found that the mean winds and dw1 produce a wave two pattern in equatorial vertical e bdrift that is upward in the morning and around dusk the modeled sw2 also produces a wave two pattern in the ionospheric vertical drift that is nearly a half wave cycle out of phase with that due to mean winds and dw1 sw1 can cause large vertical drifts around dawn while qspw1 does not have any direct impact on the vertical drift wind components of both sw2 and sw1 become large at middle to high latitudes in the e region and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift likely through modulating the e region wind dynamo the most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk reflecting the more dominant role of large f region pedersen conductivity and of the f region dynamo under high solar activity therefore the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions not only because variability is more identifiable in a quieter background but also because the e region wind dynamo is more significant these numerical experiments also demonstrate that the amplitudes phases and latitudinal and vertical structures of large scale waves are important in quantifying the ionospheric responses

impact of crustal evolution on changes of the seismic properties of the uppermost ocean crust one of the most important observations of oceanic crustal evolution is that the uppermost part of the igneous crust layer 2a appears to thin and eventually disappear as its seismic velocity doubles from approximately 2 2 to 4 5 km s 1 in the first 40 m y the most likely cause is decreasing porosity in extruded basalts that compose the uppermost igneous crust by filling cracks with hydrothermally generated minerals a by product of off axis hydrothermal circulation and alteration of basalts new insights from two recent papers on crustal hydrothermal circulation patterns and modeling of the effects of crack geometry distributions upon seismic velocities provide guidance to relate filling of cracks within the basement to seismic velocity increases a qualitative model of layer 2a crustal evolution is outlined that satisfies many geophysical and geochemical observations some seemingly unrelated somewhat surprisingly the crustal age at which layer 2a seismic velocities reach their maximum value is primarily controlled by the integrated permeability of the overlying sediment which in turn controls the hydrologic regime necessary for secondary mineral precipitation speculative predictions can be used to verify refine or invalidate this dynamic model of crustal evolution major scientific and technical obstacles must be overcome before a definitive model can be quantified with such a rigorous model of crustal upper crustal evolution in hand remote geophysical sensing tools can begin to fulfill the promise of interpreting the physical state composition and past history of oceanic crust

two day wave structure and mean flow interactions observed by radar and high resolution doppler imager data obtained with four mf and meteor radars at equatorial and subtropical sites and with the high resolution doppler imager hrdi instrument aboard the uars satellite were used to examine the structure wave mean flow interactions and potential sources of the 2 day wave in the middle atmosphere during three southern hemisphere summers the three wave events were highly transient having typical durations of 20 to 30 days and exhibiting modulation at shorter periods temporal variations were found to exhibit good correlations between radar and hrdi data radar and hrdi data were used to estimate those components of the eliassen palm flux that could be assessed with these data meridional fluxes of momentum and heat were computed using hrdi data and agree reasonably with the momentum fluxes computed from radar data at discrete locations these fluxes were found to exhibit consistent latitudinal structures each year suggesting systematic wave excitation and wave mean flow interactions meridional momentum flux gradients were seen to be anticorrelated with zonal wind accelerations in a manner consistent with wave forcing of the large scale circulation the apparent wave mean flow interactions suggest that the 2 day wave could be a transient response to baroclinic instability of the summer hemisphere mesospheric jet a calculation of the meridional gradient of quasi geostrophic potential vorticity using hrdi winds and the cospar international reference atmosphere cira 1986 temperatures exhibits a region of instability in the lower and middle mesosphere extending into subtropical latitudes and provides additional evidence of a possible source of this motion via baroclinic instability of the summer hemisphere jet structure

dynamics of the equatorial mesosphere first results with a new generation partial reflection radar the first observations of mesospheric winds made between january august 1990 with an mf partial reflection radar located on christmas island 2 n 157 w in the central pacific are described the mean zonal winds are in general westward but show clear evidence for a wave driven circulation power spectral studies indicate that waves are present over a wide range of periods ultra fast kelvin waves are especially evident in january march with peak amplitudes 20 ms 1 and intrinsic phase speeds of 150 ms 1 indicated the kelvin waves are estimated to contribute an eastward acceleration of up to 10 ms 1 day 1 gravity wave amplitudes are also found to be almost as large as those observed at mid latitude sites which suggests that convection is a major source of gravity wave activity

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

observations of the quasi 2 day wave in the mesosphere and lower thermosphere over yamagawa and wakkanai 1 mesospheric lower thermospheric mlt winds observed at yamagawa 31 2 n 130 6 e and wakkanai 45 4 n 141 7 e using the spaced antenna technique have been analyzed to study features of the quasi 2 day oscillations we have used 4 5 years 1996 2000 of near continuous data for the analysis our results are consistent with the reports at other midlatitude sites the analysis reveals that the wave features observed at these two stations are similar the occurrence of the wave event probably the same is seen at both stations during the same days the wave is found every year with the maximum amplitude in the summer months the meridional component has larger amplitudes than the zonal component comparing the amplitudes at the two stations we find that the values observed at yamagawa are larger than those at wakkanai the amplitude appears to attain its maximum value at around 90 km at both stations substantial year to year variations are observed in the 2 day wave amplitude the average wave period observed at yamagawa and wakkanai is approximately 48 hours the study also explores the dependence of the 2 day wave on the background atmospheric circulation however further analysis on wave events is needed to obtain a better understanding of this aspect the results of the present study are also compared with the earlier meteor radar observations in kyoto japan and some other midlatitude observations further coordinated studies are suggested to investigate horizontal structure and generating mechanism of the 2 day wave

heat flow sediment and pore fluid chemistry and hydrothermal circulation on the east flank of alarcon ridge gulf of california new seismic heat flow sediment and pore fluid geochemistry data from the east flank of alarcon ridge at the mouth of the gulf of california provide evidence for vigorous hydrothermal circulation within young oceanic crust formed at a moderate rate spreading center data and samples were collected 9 20 km from the ridge axis to assess the hydrologic state of 0 30 0 65 ma seafloor conductive heat flow values are 15 55 of that input at the base of the lithosphere heat flow is highest near the center of a sediment covered trough and lowest along the trough margins suggesting that trough bounding faults and basement exposures may help to focus hydrothermal recharge sediment and pore fluid geochemistry data in combination with reactive transport modeling indicate that conditions within the shallow sediments are dominantly diffusive and reactive in two locations but that bottom seawater recharges through the thin sediment layer with velocities on the order of 2 10 mm yr at other sites seafloor heat flow appears to be entirely conductive which is consistent with the slow rate of seepage inferred from pore fluid observations and modeling fluid recharge through sediments requires that basement is underpressured relative to hydrostatic conditions we interpret these observations and inferences to indicate vigorous fluid flow in basement and secondary seepage through overlying sediments the heat flow deficit along the 11 km alarcon basin transect averages 440 mw m 2 equivalent to heat output of 5 mw per kilometer of spreading axis this heat output is similar to the combined focused and diffusive heat output of a single basement outcrop on the east flank of juan de fuca ridge and suggests that sites of concentrated heat and fluid outflow may exist on the east flank of alarcon ridge fl 2001 published by elsevier science b v

alteration of the oceanic crust implications for geochemical cycles of lithium and boron abstract fresh tholeiitic basalt glass has been reacted with seawater at 150 c water rock mass ratio of 10 and fresh diabase has been reacted with a na k ca cl fluid at 375 c water rock mass ratios of 1 2 and 5 to understand better the role of temperature basalt composition and water rock mass ratio on the direction and magnitude of b and li exchange during basalt alteration at 150 c slight but nevertheless significant amounts of b and li were removed from seawater and incorporated into a dominantly smectite alteration phase at 375 c however b and li were leached from basalt b behaved as a soluble element and attained concentrations in solution limited only by the b concentration in basalt and the water rock mass ratio li however was less mobile for example at water rock mass ratios of 1 2 and 5 the percent of li leached from basalt was 58 70 and 92 respectively this suggests some mineralogic control on li mobility during hydrothermal alteration of basalt especially at low water rock mass ratios in general these results as well as those for b are consistent with the temperature dependent chemistry of altered seafloor basalt and the chemistry of ridge crest hydrothermal fluids based on the distribution and chemistry of products of seafloor weathering low 150 c and high temperature hydrothermal alteration of basalt and the chemistry of ridge crest hydrothermal fluids it was estimated that alteration of the oceanic crust is a li source for seawater this is not true for b however since the hot spring flux estimated for b is balanced by low temperature basalt alteration these data coupled with b and li flux estimates for other processes e g continental weathering clay mineral adsorption authigenic silicate formation and formation of siliceous skeletal material yield new insight into the b and li geochemical cycles calculations performed here indicate relatively good agreement between the magnitude of b and li sources and sinks the geochemical cycle of b however may be affected by serpentinization of mantle derived peridotite in oceanic fracture zones serpentinites are conspicuously enriched in b and if the b source for these rocks is seawater then an additional b sink exists which must be integrated into the b geochemical cycle however until more data are available in terms of areal extent of serpentinization serpentite chemistry and isotopic composition the importance of b in these rocks with respect to the b geochemical cycle remains speculative at best

surficial permeability of the axial valley seafloor endeavour segment juan de fuca ridge 1 hydrothermal systems at mid ocean spreading centers play a fundamental role in earth s geothermal budget one underexamined facet of marine hydrothermal systems is the role that permeability of the uppermost seafloor veneer plays in the distribution of hydrothermal fluid as both the initial and final vertical gateway for subsurface fluid circulation uppermost seafloor permeability may influence the local spatial distribution of hydrothermal flow a method of deriving a photomosaic from seafloor video was developed and utilized to estimate relative surface permeability in an active hydrothermal area on the endeavour segment of the juan de fuca ridge the mosaic resolves seafloor geology of the axial valley seafloor at submeter resolution over an area greater than 1 km2 results indicate that the valley walls and basal talus slope are topographically rugged and unsedimented providing minimal resistance to fluid transmission elsewhere the axial valley floor is capped by an unbroken blanket of low permeability sediment resisting fluid exchange with the subsurface reservoir active fluid emission sites were restricted to the high permeability zone at the base of the western wall a series of inactive fossil hydrothermal structures form a linear trend along the western bounding wall oriented orthogonal to the spreading axis high temperature vent locations appear to have migrated over 100 m along ridge strike over the decade between surveys while initially an expression of subsurface faulting this spatial pattern suggests that increases in seafloor permeability from sedimentation may be at least a secondary contributing factor in regulating fluid flow across the seafloor interface

passive off axis convection through the southern flank of the costa rica rift pore fluids are passively convecting through young oceanic sediments and crust around deep sea drilling project dsdp site 504 on the southern flank of the costa rica rift as inferred from a variety of geological geochemical and geothermal observations the presence of a fluid circulation system is supported by new data collected on ocean drilling program odp leg 111 and a predrilling survey cruise over the heavily sedimented 5 9 ma site during the latter elongated heat flow anomalies were mapped subparallel to structural strike with individual measurements of twice the regional mean value and strong lateral and vertical geochemical gradients were detected in pore waters squeezed from sediment cores also there is a strong correlation between heat flow bathymetry sediment thickness and inferred fluid velocities up through the sediments on an earlier dsdp leg an 8 bar underpressure was measured in the upper 200 m of basement beneath thick sediment cover although the forces which drive passive circulation are not well understood it has generally been thought that the length scale of heat flow variations provides a good indication of the depth of hydrothermal circulation within the oceanic crust this assumption was based on analytical and numerical analyses of relatively simple porous media models deep crustal convection had been inferred near site 504 based on the geometry of surface heat flow anomalies with a wavelength of 4 7 km but appears to be precluded by low crustal permeability as measured in dsdp hole 504b the widely varied geothermal and hydrogeological observations near site 504 are readily explained by a model which combines 1 basement relief 2 irregular sediment drape 3 largely conductive heat transfer through the sediments overlying the crust and 4 thermal and geochemical homogenization of pore fluids at the sediment basement interface which results from 5 topographically induced passive hydrothermal circulation with large aspect ratio convection cells this convection involves mainly the permeable upper 200 300 m of crust the deeper crust is not involved this convection is induced through a combination of buoyancy fluxes due to heating from below and topographic variations on the seafloor and at the basement sediment interface this model was designed to incorporate data from both near the sediment surface and deep within boreholes it is successful in duplicating numerous field observations

a numerical simulation of the two day wave near the stratopause abstract the middle atmosphere version of the national center for atmospheric research community climate model 2 maccm2 mechanistic model is used to simulate several aspects of the observed two day wave near the stratopause and its possible connection with inertial instability model experiments show that for a prescribed initial wind condition with strong horizontal wind variation in the tropics inertial instability can trigger the two day wave an increase in horizontal wind curvature fostered by inertial instability circulation barotropically destabilizes the easterly jet in low summer latitudes and allows first the growth of the wavenumber 4 and then the wavenumber 3 component of the two day wave near the stratopause the two day wave eliassen palm flux is directed equatorward away from the wave s critical line source and westerly momentum is transported into the easterly jet core by the wave while much of the wavenumber 4 energy is confined near the stratopause the wavenumber 3 energy can prop

mapping the fluid flow of the mariana mounds ridge flank hydrothermal system pore water chemical tracers we present a conceptual model of fluid circulation in a ridge flank hydrothermal system the mariana mounds the model is based on chemical data from pore waters extracted from piston cores and from push cores collected by deep sea research vessel alvin in small meter sized mounds situated on a local topographic high these mounds are located within a region of heat flow exceeding that calculated from a conductive model and are zones of strong pore water upflow we have interpreted the chemical data with time dependent transport reaction models to estimate pore water velocities in the mounds themselves pore water velocities reach several meters per year to kilometers per year within about 100 m from these zones of focused upflow velocities decrease to several centimeters per year up to tens of centimeters per year a larger area of low heat flow surrounds these heat flow and topographic highs with upwelling pore water velocities less than 2 cm yr in some nearby cores downwelling of bottom seawater is evident but at speeds less than 2 cm yr downwelling through the sediments appears to be a minor source of seawater recharge to the basaltic basement we conclude that the principal source of seawater recharge to basement is where basement outcrops exist most likely a scarp about 2 4 km to the east and southeast of the study area

observation of the two day wave near the southern summer stratopause temperature and h2o measurements from the upper atmospheric research satellite microwave limb sounder uars mls data sets during southern hemisphere summer of 1991 92 are analyzed using the asynoptic mapping method results show a prominent wavenumber 3 two day wave confined to latitudes between 60 s and 4 n and to altitudes above 2 hpa the temperature wave amplitude increases upward to the upper limit of the observations and maximizes at 2 0 k near 0 465 hpa the h2o wave amplitude reaches a maximum of 0 25 ppmv near 1 hpa evidence suggestive of wave breaking and meridional mixing associated with the interaction between this wave and a lower frequency wavenumber 1 is shown

measurements of plume flow from a hydrothermal vent field simultaneous velocity temperature and conductivity data were taken in the convective flow emanating from a hydrothermal vent field located at 10 56 n 103 41 w on the east pacific rise the horizontal profiles obtained indicate that the flow field approaches an ideal plume in the temperature and velocity distribution such parameters as total heat flow and maximum plume height can be estimated using either the velocity or the temperature information the results of these independent calculations are in close agreement yielding a total heat flow from this vent site of 3 7 0 8 mw and a maximum height of 150 10 m the nonlinear effects of large temperature variations on heat capacity and volume changes slightly alter the calculations applied to obtain these values

the two day wave in eos mls temperature and wind measurements during 2004 2005 winter 1 two day wave observations during january march 2005 are reported using the recently launched microwave limb sounder mls aboard nasa s earth observing system aura mission wave induced disturbances in temperature water vapor carbon monoxide and mls line of sight wind appear in early january peak near the end of january and persist until late february temperature and wind amplitudes as large as 9 k and 50 m s are observed near 90 km the wave disturbance is initially confined in the mid to low summer latitudes where the climatological summer easterly jet exhibits strong shear the wave then develops features akin to the third rossby gravity global normal mode with a weak temperature disturbance in the winter hemisphere anti symmetric about the equator and wind disturbance over the equator strong wind perturbation episode around 17 23 january 2005 in the mid latitude southern hemisphere coincides with a particularly intense solar proton event