evidence of active ground deformation on the mid ocean ridge axial seamount juan de fuca ridge april june 1988 since september 1987 a precision bottom pressure recorder bpr has been deployed within the summit caldera of axial seamount on the central juan de fuca ridge the instrument is capable of measuring pressure to 1 mbar resolution and recording these measurements at 64 samples per hour for up to 15 months after removal of oscillatory signals due to tidal and oceanographic effects and linear trends caused by sensor drift any significant change in the pressure record should indicate a change of depth associated with vertical ground movement in subaerial volcanic systems such ground movements commonly indicate active inflation or deflation of underlying magma bodies and are frequently coincident with rift eruptions axial seamount was selected for this pilot study for three primary reasons 1 its tectonic setting 2 the presence of a well formed summit caldera and 3 observational evidence of geologically recent volcanic activity results from the first 9 months of the bpr deployment revealed a significant change in pressure which is interpreted to represent a 15 cm subsidence of the caldera floor during two 2 to 3 week periods in april june 1988 also during these periods an anomalous decline in temperature at the site was recorded that is correlated with an apparent increase in current velocity at the axial seamount hydrothermal emissions study ashes vent field suggesting vigorous advection of cold water into the caldera concurrent oceanographic data from geosat and from current meter arrays do not indicate any large scale oceanographic phenomena capable of generating these simultaneous events one mechanism to explain simultaneous ground subsidence and temperature decline at the caldera center and increased bottom current at the caldera margin is the generation of a buoyant parcel of heated water in response to the intrusion or the eruption of magma associated with volcanic deflation such a parcel must have been sufficiently buoyant and proximal to induce horizontal entrainment currents capable of producing the bottom water conditions that were observed at both sites similar volcanic events also may have generated large midwater plumes that have been described previously along the southern juan de fuca ridge

mapping the u s west coast surface circulation a multiyear analysis of high frequency radar observations signals with phase speeds of o 10 and o 100 to 300 km day 1 and time scales of 2 to 3 weeks the signals with slow phase speed are only observed in southern california it is hypothesized that they are scattered and reflected by shoreline curvature and bathymetry change and do not penetrate north of point conception the seasonal transition of alongshore surfacecirculationforcedbyupwelling favorablewindsandtheirrelaxationiscapturedinfine detail submesoscaleeddies identifiedusingflowgeometry haverossbynumbersof0 1to3 diameters in the range of 10 to 60 km and persistence for 2 to 12 days the hfr surface currents resolve coastal surface ocean variability continuously across scales from

middepth flow near hydrothermal venting sites on the southern juan de fuca ridge long term moored current measurements around the southern end of the juan de fuca ridge show that flow parallels the ridge and may be intensified by its presence the mean flow is northward on the west side and southward on the east thus plumes emanating from the ridge probably are advected along the ridge before flowing away from the ridge other topographic features may be responsible for westward or eastward turning along the west side of the ridge we hypothesize a regional flow pattern with southward flow north of axial seamount northward flow south of axial and a convergence somewhere south of axial resulting in westward flow along the east side the flow may be southward everywhere above the ridge crest the long term mean flow is weaker and more variable and it includes tidal inertial and a dominant broadband 4 day oscillation this 4 day energy is maximum in the rift valley where the inertial is least decreases upward and away from the ridge and is more energetic in winter this oscillation is predominately a clockwise rotating feature which along with the presence of inertial oscillations suggests that it may be storm induced from the sea surface these observations along with those by cannon and pashinski 1990 suggest northward propagation flow variations across the ridge lasting one to a few months have mean speeds of 1 3 cm s and are capable of transporting plumes off axis to the west or east into the northerly or southerly flows respectively

moored wind temperature and current observations made during coastal ocean dynamics experiments 1 and 2 over the northern california continental shelf and upper slope moored observations of winds currents and temperature made over the northern california shelf and upper slope during the 1981 and 1982 upwelling seasons as part of the coastal ocean dynamics experiment code are described in both field experiments code 1 and code 2 the onset of the upwelling season is triggered by the strengthening of the north pacific high off northern california and signalled by the presence of water colder than 9 c near the bottom over the shelf vertical temperature stratification over the shelf is reduced during active upwelling local winds and subtidal currents over the shelf are strongly polarized in the alongshelf direction and the mean wind stress is directed equatorward response of alongshelf currents to wind forcing is similar at all depths over the shelf the response of the cross shelf current is more complex in the surface layer offshelf flow is significantly and positively correlated with the upwelling favorable alongshelf wind stress beneath this layer a weak return flow exists the thickness of the upper mixed layer varies greatly reaching 60 m during upwelling events thus direct wind forcing affects a substantial fraction of the water over the shelf low frequency wind stress current and temperature fields are adequately described by a few energetic empirical orthogonal functions with simple spatial structure the most energetic mode typically accounts for 75 or more of the variance of wind stress and temperature over the middle and inner shelf the most energetic current mode accounts for 90 or more of the variance is dominated by he alongshelf component and veers to the left with depth the low frequency alongshelf flow fluctuations are quasi barotropic with some vertical shear but no reversal with depth vertical shear in alongshelf current and the cross shelf density gradient obey the thermal wind relation the simple structure of the subdiurnal currents allow estimation of the alongshelf volume transport between the 60 and 130 m isobaths through three cross shelf transects in code 2 volume transport over the shelf is often nearly two dimensional but occasional large differences indicate significant mass exchange between the shelf and the adjacent upper slope correlation of low frequency currents and alongshelf wind stress shows the response of alongshelf current to be maximum near the surface and near midshelf where a 15 cm 1 alongshelf flow lags a 1 dyn cm 2 alongshelf wind stress by the order of 10 hours currents over the upper slope are not significantly correlated with local wind alongshelf transport over the shelf is highly correlated with local wind stress explaining 80 of the variance in the low frequency transport during code 2 volume transport is best correlated with wind stress approximately 30 km to the south winds in the code area during spring and summer are characterized by strong and persistent upwelling favorable winds interrupted by shorter periods of weak winds regression analysis indicates that in the absence of wind a poleward barotropic current jet exists over the shelf with a maximum amplitude over the inner shelf in the code area an upwelling favorable wind counters this jet over the shelf so that the alongshore flow is everywhere equator ward during strong wind events since the maximum response to wind forcing is found at midshelf and near surface the mean current over the upwelling season is strongly sheared in both the vertical and cross shelf directions mean flow over the outer shelf is surface intensified and is directed offshelf and equatorward while the deeper flow at midshelf and through most of the water column over the inner shelf is directed poleward

subtidal bottom pressure observed at axial seamount in the northeastern continental margin of the pacific ocean since september 1987 bottom pressure bp has been observed at axial seamount 45 57 5 n 130 00 3 w 1540 m depth located 450 km off the oregon coast on the juan de fuca ridge observations from 1987 to 1992 show that subtidal axial bp is dominated by barotropic 2 to 5 mbar fluctuations with frequencies 1 9 cycles per day cpd they are slightly smaller than subtidal bp observed 720 km to the west during the ocean storms experiment and a factor of 2 4 smaller than the subtidal fluctuations of adjusted sea level asl at the coast for the period september 1987 to july 1988 axial bp and ocean storms bp are significantly coherent coh2 0 5 except at intraseasonal frequencies 1 100 1 20 cpd and in a band 1 8 1 6 cpd of low axial bp variance in the coherent frequency bands the phase relationships between the two bp series suggest independent atmospheric forcing on the other hand axial bp and coastal asl are not coherent except at the fortnightly tidal frequency looking for possible forcing of axial bp by the curl of the wind stress curl over the ne pacific data analyses show that axial bp and curl derived from european centre for medium range weather forecasts winds are significantly coherent in only two frequency bands one band narrowly peaked near 1 9 1 cpd for curl in regions south of axial seamount and a 1 5 1 3 5 cpd band for curl in a large region nw of the seamount in the 1 5 1 3 5 band axial bp also has a small amplitude spectral peak associated with bottom trapped baroclinic currents near axial seamount remote axial bp curl coherence at some frequencies is qualitatively consistent with the local forcing theory of lippert and muller 1995 that attributes the coherence to stable phase relationships and the spatial characteristics of the bp curl transfer function however the axial bp curl comparison is inhibited by the lack of accurate estimates of curl within 400 km of the coast fully understanding the origins and dynamics of subtidal bp at axial seamount will require a knowledge of how the complex topography in the region affects the barotropic and baroclinic responses to atmospheric forcing as well as the propagation of rossby and other waves

observed dynamics of coastal flow at cape mendocino during coastal waves 1996 abstract airborne in situ and remote meteorological measurements from around cape mendocino california sampled during the coastal waves 1996 field program are analyzed for three different days 7 12 and 26 june 1996 two days conformed to typical summertime conditions with a strong northerly downcoast flow while the wind on the third day was weaker on the first 2 days the flow was supercritical in the sense that the froude number was larger than unity and these 2 days feature expansion fans in the lee of the cape on the third day no such phenomenon was observed all 3 days had a strong thermal wind caused by the marine inversion sloping down toward the coast on the first 2 days the flow aloft was westerly or northerly so that the thermal wind added to the background flow results in a strong jet on the third day the flow aloft was southerly and consequently even with the added thermal wind the northerly flow in the marine layer was too weak to be supercritical the main difference between t

characteristic patterns of the circulation in the santa barbara channel the subtidal near surface circulation in the santa barbara channel sbc and on the shelf north of point conception is described based on observations obtained during the 3 year period from 1993 to 1995 near surface currents in the channel are a superposition of a larger than sbc scale flow and a cyclonic circulation of variable intensity located inside the channel on seasonal timescales the larger than sbc scale flow near the surface is equatorward in spring and poleward from summer through winter the increase in equatorward flow in spring occurs concurrently with the increase in equatorward wind stress and the decrease in near surface temperatures and synthetic subsurface pressures ssps the flow reverses in late spring simultaneously with the increase in the along channel ssp difference and months before wind stress has reached its peak the period during which the cyclonic circulation within the sbc is strongest coincides with the period of strongest poleward flow through the eastern entrance a synoptic description of the circulation in the sbc is presented in terms of six characteristic patterns labeled upwelling relaxation cyclonic propagating cyclones flood east and flood west an analysis of the 5 and 45 m currents into empirical orthogonal functions eofs isolates 50 53 of the 5 m 45 m low frequency current variance into three two modes combining these modes with the mean current fields the modes have spatial patterns that correspond to the characteristic flow patterns subjectively deduced from inspection of daily averages of the near surface currents from late spring through fall the two largest 5 m current modes produce a repeating pattern of circulation in which the sequence of four states namely upwelling cyclonic relaxation and quiescent is traversed roughly every 16 days in addition to the large scale cyclonicity in the central sbc smaller cyclonic eddies form frequently in the eastern channel and travel toward the west with an average speed of 0 06 m s 1 the patterns described here develop in response to the wind stress and the along channel ssp gradient

ocean tides in the continental margin off the pacific northwest shelf a comparison of bottom pressure observations and global tide models shows that the regional distributions of the diurnal and semidiurnal tides off the oregon and washington shelves are determined mainly by the large scale amphidromic systems in the north pacific ocean these cause the tidal amplitudes to increase toward the northeast and the phase lags to increase toward the northwest within 200 500 km of the shelfbreak the curving continental boundary causes the cophase lines to be closely packed near cape mendocino and more widely spread in the bight to the north farther seaward the m2 tide is consistent with a kelvin wave propagating along the british columbia boundary 315 t while the k1 tide decays offshore more slowly than expected from kelvin wave theory a long term 4 2 year bottom pressure series at axial seamount 45 58 n 130 00 w depth 1540 m yields a nongravitational s 2 tide that is consistent with a large scale barotropic tide extending seaward from the coast at lower frequencies the observed mf amplitude matches recent global models while the mf phase lag is marginally earlier than model phases nearby mf currents are bottom trapped and consistent in phase with quasi geostrophic dynamics their magnitudes near the bottom are much larger than barotropic mf currents observed farther west in the north pacific the models reproduce the distributions of the diurnal and semidiurnal harmonic constants but with broad scale offsets in the amplitudes and phase lags these offsets cause errors standard deviation 3 0 cm in predicted time series of the diurnal and semidiurnal tides that fluctuate on fortnightly to interannual timescales the 29 seasonal variations of the errors are largest in winter and are modulated by 4 5 year fluctuations associated with the nodal cycle in situ measurements can be used to remove these regional offsets this would improve the temporal and spatial resolution of nontidal sea level estimates that are based on satellite altimeter data

a description of subtidal pressure field observations on the northern california continental shelf during the coastal ocean dynamics experiment during the coastal ocean dynamics experiment code along the northern california continental shelf in the spring and summer of 1981 and 1982 the first comprehensive effort to obtain all of the observations necessary to infer pressure fluctuations throughout the water column was made this is a description of the subtidal fluctuations in measured bottom pressure internal pressures inferred from moored conductivity and temperature observations and the water column total pressure anomalies computed from a combination of the two components the pressure field during code 2 april july 1982 is found to be more energetic than that in code 1 april july 1981 with more than 70 total pressure variance concentrated at frequencies of less than 15 days 1 the spatial structure of the pressure fluctuation field is characterized by coastal intensification and a tendency for poleward phase propagation like the pressures most of the code across shelf pressure difference variance is found at the lower frequencies with more than 60 of the total across shelf pressure difference variance at frequencies of less than 15 days 1 the code across shelf pressure differences are found to be in geostrophic balance with both alongshelf currents and the total alongshelf transport the alongshelf pressure difference variance is generally found to be concentrated at the lower frequencies much like that of the across shelf pressure differences most of the pressure and pressure difference variance is found to be highly coherent with wind stress the 20 day band pressure variability is apparently related to the response of the pressure field during so called relaxation events the barotropic component of the alongshelf geostrophic transport i e across shelf pressure difference has been found to be almost perfectly coherent with regional wind stress y and to propagate poleward within the code region at the same rate as y and the alongshelf pressure gradient is very important in accelerating the alongshelf flow the 5 day band pressure variability in the code region appears to result from local wind stress fluctuations the alongshelf pressure gradient was found to be of secondary importance relative to the wind in accelerating the alongshelf flow

variability on the california shelf forced by local and remote winds during the coastal ocean dynamics experiment the coastal response to local and remote wind forcing is examined using observations from the coastal dynamics experiment code which took place on the northern california coast during 1981 and 1982 the responses to local and remote forcing are determined from multivariate statistical cross spectral analysis covering periods from 12 to 2 5 days remote forcing is deduced from coastal sea level this analysis leads to discovery of a mode of sea level variability apparently a barotropic kelvin wave with much greater alongshore and across shelf scales than those of coastally trapped waves there is no measurable response to this mode in coastal temperature or velocity coastally trapped waves are also evident and have responses over the shelf much as predicted by theories which account for bottom friction the local response to wind differs markedly from coastally trapped waves showing the across shelf flow responsible for upwelling surface intensified temperature fluctuations caused by advection and mixing and even the alongshore pressure gradient partly responsible for the across shelf return flow which on the largest scale balances ekman transport unfortunately even the extensive code observations are inadequate to diagnose the dynamics of the across shelf flow or accurately determine the cross shelf heat flux supported by eddies and the fluctuating responses to local wind forcing

the response of stratified frictional flow of shelf and slope waters to fluctuating large scale low frequency wind forcing abstract numerical and analytical models are developed to discuss large scale low frequency wind driven fluctuations over the continental shelf and slope in the presence of realistic density stratification and bottom friction the models employ the long wave assumption that frequencies are small relative to the inertial frequency and that alongshore scales are large relative to cross cross shelf scales an attempt is made to make the effect of bottom friction on the flow as realistic as possible by taking into account the influence of surface gravity waves on bottom stress the results were obtained for sinusoidal wind forcing having frequency and alongshore wavenumber l and are described below a general criterion for barotropic shelf water response for wind forcing frequencies in the weather band 2 few weeks to 2 few days can be derived for the purpose of rapid calculation this criterion reduces approximately tohere ns2 is a shelf averaged value of the buoyancy frequency squared is

the global distribution of f h and the barotropic response of the ocean the barotropic response of the ocean over smoothly varying topography is directly related to the potential vorticity gradient f h a global estimate of f h and f h have been constructed from a high resolution digital topographic data base four different regimes of the barotropic response of the ocean are suggested by these maps 1 in the tropical latitudes from 20 s to 20 n f h h the response will be similar to a flat bottom sverdrup regime 2 in mid latitudes 20 to 70 north of 30 s f h h the response will be quasi stationary weak and dominated by nonlocal forcing flow along isolines of f h 3 in a number of small regions throughout the mid latitudes in both hemispheres f h h in these regions the local response flow across isolines of f h should be amplified and wavelike motions may occur over a broader bandwidth of frequencies 4 south of 30 s the mid ocean ridge system becomes zonal and isolates several large regions within closed lines of f h in these regions principally the abyssal plains of the southern ocean the low frequency barotropic response of the ocean may be wavelike in character and much stronger than the sverdrup response consequently this analysis suggests that the southern ocean may have a stronger barotropic response to wind forcing than the other five major ocean basins

five years of ground deformation monitoring on axial seamount using a bottom pressure recorder the results of five years of pressure measurements collected by a bottom pressure recorder deployed within the summit caldera of axial seamount on the central juan de fuca ridge are interpreted for monotonic offsets related to vertical seafloor movements results indicate five significant subsidence events during the observation period 3 7 years or an average of 1 35 events per year the displacements range from 3 10 cm with durations of 10 14 days these results indicate an active volcanic system and can be viewed as positive evidence for future attempts at seafloor volcanic observatories and response to active events on oceanic ridge crests advanced instrumentation based on multiple sensors has been deployed at the site to reinforce the results of this pilot experiment

large scale response to atmospheric forcing of shelf currents and coastal sea level off the west coast of north america may july 1981 and 1982 the response of alongshore currents v over the continental shelf and of coastal sea level along the pacific coast of north america to atmospheric forcing on large alongshore scales 100 2000 km during may july 1981 coastal ocean dynamics experiment code 1 and may july 1982 code 2 has been studied using sea level and wind measurements from coastal stations and buoys between 33 n and 48 n and using current measurements from five locations between 35 n and 48 n characteristics of the large scale response of v and to fluctuations in the alongshore component of the wind stress varied with latitude and with year in relation to variations in in 1981 large scale fluctuations were coherent within but not between separate domains north and south of 42 n in 1982 large scale coherent fluctuations were found only in a northern domain that extended much farther south to near 37 n accordingly in 1981 alongshore current v fluctuations from 39 n code were coherent with v from 35 n while in 1982 v fluctuations from 39 n were coherent with those north to 48 n in 1981 the northern domain fluctuations were forced by between 42 n and 45 n with southern domain forcing at 35 36 n in 1982 northern domain fluctuations were forced by over a region of much larger along shore extent 37 48 n high values of space lagged coherences between v and y y is the alongshore coordinate indicate that v at 39 n was strongly wind driven maximum squared coherences of v versus y are found with to the south by 100 300 km for low frequencies 0 23 cpd in 1981 0 14 cpd in 1982 and with from near local stations at higher indicating the importance of remote forcing at low frequencies and local forcing at high frequencies the response of v to y at 35 n and 43 n was more complicated but evidence for strong wind forcing is found in several frequency bands for v at 43 n during 1981 and 1982 and at 35 n during 1981 at 48 n v was forced in 1982 for 0 18 cpd by from locations 300 1400 km to the south

the large scale coastal wind field along the west coast of north america 1981 1982 we study the statistical properties of the coastal wind field along the west coast of north america for two summers 1981 and 1982 coastal ocean dynamics experiments 1 and 2 respectively and the intervening winter using measured winds and geostrophic winds calculated from fleet numerical oceanography center atmospheric pressure analyses summer wind fluctuations are driven primarily by the interaction between two relatively stationary pressure systems the north pacific subtropical high and southwest u s thermal low and by their interactions with propagating atmospheric systems to the north in particular propagating cyclones and associated fronts are often followed by a northeastward intensification of the high producing strong upwelling events along the california coast this summer event sequence occurs more frequently and is displaced farther to the south on average during summer 1981 winter wind fluctuations are primarily driven by propagating cyclones and anticyclones and they tend to have larger variance and space scales than in summer a preference for poleward equatorward propagation exists in summer winter and the largest time scales are observed in summer 1982 coastal atmospheric boundary layer processes substantially modify winds within 100 200 km of the coast consequently measured wind fluctuations are strongly polarized in the alongshore direction and have means and rms amplitudes that can vary considerably between nearby stations along the coast calculated wind fluctuations are less polarized in the alongshore direction and have alongshore correlation scales about 60 larger than those for measured winds they represent fluctuations with alongshore wavelengths of 900 km rather well but represent poorly those with smaller wavelengths and those due to coastal atmospheric boundary layer effects

subtidal sea level fluctuations in a large fjord system a cross spectral analysis is made of subtidal 0 01 0 5 cpd sea level ssl atmospheric pressure and wind fluctuations observed during 1966 1988 in the southern reaches of the fjord system formed by the straits of juan de fuca georgia and puget sound it shows that observed ssl can be largely explained by quasi steady inverse barometer compensation to atmospheric pressure and the propagation of adjusted sea level fluctuations from the nearby continental shelf with some local weather forcing in summer variations in coherence amplitudes and relative phase between seasons locations and frequencies support previous work that both barotropic and baroclinic processes have important influences in ssl within the fjord system

bottom trapped subinertial motions over midocean ridges in a stratified rotating fluid abstract linear analytical solutions for bottom trapped subinertial oscillatory flow over simple ridge topographies in a stratified two layer rotating fluid are presented results are compared to moored current meter observations of bottom intensified motions over the endeavour segment of juan de fuca ridge in the northeast pacific the solutions reproduce many of the observed features including preferential amplification of the clockwise rotary component of velocity over the ridge and increased velocity amplification with proximity to the ridge crest for a given internal deformation radius the degree of current amplification increases with increased bottom slope ridge height and oscillation frequency amplification decreases with increased width of the ridge relative to the deformation radius

diagenetic replacement of feldspars by titanium oxides in sandstones abstract titanium oxides are found to replace detrital microcline and albite in sandstones of the visingso group upper proterozoic southern sweden the mode of occurrence and crystal habit of the titanium oxides suggests diagenetic precipitation from solutions rich in titanium ions in dissolution voids of the feldspars and in feldspars replaced by calcite and clay minerals

intraseasonal oscillations in sea level along the west coast of the americas abstract hourly observations of coastal sea level at stations from peru to british columbia are analyzed for low frequency content a space time contour plot of sea level from four years of data during the 1971 75 period shows the meridional structure of the seasonal cycle and interannual variability associated with the 1972 73 el nino oscillations with intraseasonal periods of 36 73 days are also evident coherent over alongshore distances of several thousand kilometers further investigation using spectral methods and empirical orthogonal function analysis in the frequency domain reveals in particular that intraseasonal sea level variability has a peak in spectral density along the coasts of south america central america and mexico with high coherence from near the equator tumaco 2 n north to central california 34 n and south to at least callao 12 s phase propagation north of the equator is poleward at 150 200 kilometers day atmospheric pressure alongshore wind stress and wind stress cu

poleward propagating subinertial alongshore surface currents off the u s west coast 1 the network comprising 61 high frequency radar systems along the u s west coast uswc provides a unique high resolution and broad scale view of ocean surface circulation subinertial alongshore surface currents show poleward propagating signals with phase speeds of o 10 and o 100 300 km d 1 that are consistent with historical in situ observations off the uswc and that can be possibly interpreted as coastally trapped waves ctws the propagating signals in the slow mode are partly observed in southern california which may result from scattering and reflection of higher mode ctws due to curvature of shoreline and bathymetry near point conception california on the other hand considering the order of the phase speed in the slow mode the poleward propagating signals may be attributed to alongshore advection or pressure driven flows a statistical regression of coastal winds at national data buoy center buoys on the observed surface currents partitions locally and remotely wind forced components isolates footprints of the equatorward propagating storm events in winter off the uswc and shows the poleward propagating signals year round

the relationship between deep ocean currents and winds east of barbados abstract observations of currents collected at the polymode array iii cluster c 16 n 54 w are compared with radiosonde winds measured at barbados 13 n 62 w using a linear response analysis the winds and the currents are coherent throughout the water column 5400 m over the subinertial frequency range of 0 025 to 0 25 cpd the coherence is highest between the east west wind stress and north south currents over smooth topography the wind related ocean currents have a rms of 2 5 cm s 1 at 500 m and 1 1 cm s 1 at 4000 m and account for approximately one third of the total eddy kinetic energy the wind current phase is depth independent and does not vary significantly over the 200 km horizontal scale of the array the response amplitude is surface intensified and increases with decreasing frequency which is consistent with a deterministic theoretical model the coherence values and response estimates suggest an off resonant barotropic response to large scale wind forcing

axial seamount an active ridge axis volcano on the central juan de fuca ridge axial seamount some of the manuscripts in this special section refer to the edifice with the more precise name of axial volcano a large ridge axis volcano is located on the central segment of the juan de fuca ridge approximately 250 nautical miles west of the washington oregon british columbia coast currently both volcanically and hydrothermally active axial lies directly at the intersection of the cobb eickelberg seamount chain and the juan de fuca ridge figure 1 the volcanic activity associated with the seamount formation strongly interacts with and is affected by the normal seafloor spreading processes at the intersection because of this unique geologic setting its proximity to west coast ports and oceanographie institutions and its shallow depth axial has become the focus of a large number of scientific investigations over the past decade

characteristics of 4 day oscillations trapped by the juan de fuca ridge current meter observations from different studies along the crest of the juan de fuca ridge have been combined to show new features of the relatively large broad spectral peak centered near a period of about 4 days the coherence range of the 4 day oscillations has been extended to the extreme ends of the ridge and the trapped waves appear to propagate northward along the entire length of the ridge at about 1 m s spectral amplitudes are about double on the south end compared to the north end and a recent model for bottom trapped subinertial waves over topography shows this may be due to variations in ridge width allen and thomson 1993 new observations show coherence between temperatures and currents near the south cleft vent field and suggest 4 day oscillations can play a major role in the local advection of hydrothermal plumes these observations combined with earlier results demonstrate that 4 day oscillations are a significant ridge trapped feature and they suggest that other ridges may be important in transmitting energy over much longer distances

fluid control of localized mineral domains in limestone pressure solution structures grain to grain and stylolitic solution structures in two central appalachian siluro devonian limestone macroscale folds contain one of four distinct mineral assemblages that are characterized by the dominant iron phase mineral present 1 chloritegillitegpyritegcalciteg quartzgtio2ggoethite 2 chloritegillitegpyrite altered to iron oxide hydroxidegcalcite gquartzgtio2 3 chloritegilliteg magnetitegcalcitegquartz and 4 chloritegilliteggoethitegcalcitegquartzgtio2 optical reflectance microscopy and sem eds was used to characterize the mineralogy and mineral morphology of these structures geochemical modeling was used to constrain the conditions of formation and preservation the primary control on solution structure mineral assemblage was the redox conditions present in the solution structures during burial and deformation the redox conditions on the microscale may have been controlled by the local fluid chemistry and the presence absence of hydrocarbons and organic acids within the formation fluids and the influx of externally derived fluids by fracture formation during the folding process the wide variation in mineralogy of the solution structures shows that they were chemical factories where a variety of chemical reactions took place during rock dissolution in particular the formation of authigenic magnetite in solution structures has significant implications for paleomagnetic applications and use of anisotropy of anhysteretic remanent magnetization and anisotropy of magnetic susceptibility fabrics q 2005 elsevier ltd all rights reserved

variability of the wind stress curl over the north pacific implications for the oceanic response the subinertial frequency wavenumber structure and spatial coherence of wind stress curl and their spatial and temporal variability are described with the emphasis on characteristics which affect the ocean s response to the wind stress curl forcing function wind stress curl over the north pacific between 25 o and 60on was computed for 3 years 1985 1988 from the fleet numerical oceanography center wind product the range from winter peak to summer trough for the mean and variance are typically a factor of 3 4 and 10 respectively with superimposed interannual changes of up to a factor of 2 power spectra vary seasonally and interannually in an essentially frequency independent manner that is consistent with the curl variance however the spectrum over the period band 5 100 days often fails a statistical test for whiteness at the 95 level zonal and meridional wavenumber spectra were estimated for 13 sites distributed around the central eastern north pacific using the maximum likelihood method directional trends with frequency are comparable to those from earlier studies if 3 year long data segments are analyzed with approximate wavenumber symmetry except for the zonal term at mid latitudes for periods shorter than 10 days where eastward propagation is dominant however spectra for shorter data sections sometimes display eastward and westward excursions which are only weakly similar over distances of 1000 km and essentially dissimilar over longer separations the spatial correlation structure of wind stress curl is shown typically to have a main lobe of 1000 km and multiple intercorrelation lobes separated by 2000 km the strength and location of the intercorrelation peaks vary slowly with time these results suggest that curl behavior is more complex than was previously believed that the use of long term averages of or simple parameterizations for the frequency wavenumber spectrum of wind stress curl in model studies may be unrealistic and that more attention to actual curl characteristics at the time oceanic measurements are collected will be required to reconcile models with observations

the barotropic electromagnetic and pressure experiment 1 barotropic current response to atmospheric forcing during 1986 1987 an array of horizontal electrometers which measure the subinertial barotropic velocity was deployed for 11 months in the central north pacific to study atmospherically forced motions in a low eddy kinetic energy region significant coherence is found to be ubiquitous between the barotropic velocity and one or more surface atmospheric variables over the north pacific the maximum squared coherence between currents and wind stress curl at all periods greater than 3 days is typically 0 6 rarely below 0 4 and occasionally above 0 8 and is dominantly nonlocal although local coherence is seen at some sites especially at the shorter periods both the coherence and the intersite pattern similarity are strongest at the periods of relative maxima in the barotropic current autospectra e g at 6 8 10 14 and 20 50 days the locations at which the wind stress curl forces the motions at each site and for each period have been determined while there is substantial intersite variability some of the observed patterns of squared coherence over the north pacific are very similar to those predicted by simple linear smooth bottomed quasi geostrophic models of atmospherically forced barotropic currents the forcing location is occasionally found to be the same spot for all oceanic instruments especially at the autospectral maxima in barotropic current more commonly distinct forcing locations are found for each instrument even when closely spaced suggesting topographic influence in other cases multiple forcing locations are implicated for the motions at a single station all of this site and period dependent variability of the forcing location is incompatible with the simple models and is due either to the known spatial inhomogeneity of the curl forcing field or to topographic effects the importance of the former is emphasized using simple arguments based on analytic transfer functions between the atmospheric and oceanic variables and on observed wavenumber spectra for wind stress curl quantitative assessment of topographic effects must await suitable numerical models in addition maximum likelihood wavenumber spectra of the barotropic currents have been estimated in those bands with an adequate number of coherent sensors the wavenumbers at the spectral peaks are compatible with the dispersion relation for rossby waves modified by the observed large scale linearly sloping topography which shoals to the northeast the observed group velocities are in general quite consistent with the inferred forcing locations based on the ocean atmosphere coherences

sem study of authigenic rutile anatase and brookite in proterozoic sandstones from sweden abstract scanning electron microscopic examinations revealed interstitial rutile anatase and brookite to be common in upper proterozoic sandstones of the visingso group in southern sweden anatase is observed as either single discrete crystals or as numerous crystals filling and lining pore space rutile and brookite occur predominantly as clusters of crystals within interstitial cements on detrital grains e g feldspar and quartz or as overgrowths on detrital and authigenic titanium oxides these titanium oxides have been formed diagenetically from percolating pore solutions rich in titanium ions the source of titanium ions is suggested to be mainly detrital fe ti oxides sphene and biotite grains

coastal boundary conditions and the baroclinic structure of wind driven continental shelf currents abstract the generation of continental shelf currents by wind forcing is investigated by analytical and numerical methods the investigation is motivated by observations from the coastal ocean dynamics experiment a central assumption is that the vertical structure of the response over the inshore half of the shelf is controlled by the vertical distribution of the turbulent stress this suggests a two layer model of the wind driven circulation in which the upper layer represents a surface wind mixed layer and the lower layer represents the remainder of the fluid the response of this idealized dynamical model to wind forcing is examined and compared with observations in the 2 7 day period band for the alongshore velocity gain relative to local wind stress an onshore surface maximum and an offshore interior maximum are robustly reproduced by the model these features are evidently related to a dynamical transition over the inner half of the shelf in which the alongshore wind stress is balanced more by

water retention and volumetric characteristics of intact and re compacted loess a laboratory testing program was conducted to investigate the effects of microstructure on the water retention curve wrc and wetting drying induced volume change in loess the axis translation an

authigenesis of titania minerals and the mobility of ti new evidence from pro deltaic sandstones cretaceous scotian basin canada titania tio2 minerals are minor diagenetic phases in many sandstone shale successions but the conditions of ti mobility and titania authigenesis are poorly known here new modes of occurrence of authigenic titania minerals filling pores and replacing phytodetritus are documented from lower cretaceous prodeltaic sandstones in the offshore scotian basin of southeastern canada textural relationships suggest that titania minerals formed at the same time as kaolinite most commonly below lowstand sequence boundaries related to flux of meteoric water such authigenic titania is most abundant in thin bedded sandstones interbedded with thick prodeltaic mudstone in which fine grained detrital ti rich minerals are concentrated textures in titania that has replaced uncompacted phytodetritus suggest microbial mediation in near surface eodiagenesis eogenetic titania is enriched in phosphorus 0 6 p2o5 and may co occur with authigenic fluorapatite and crandallite crystals such titania resulted from prolonged flow of meteoric water that dissolved p from apatite and feldspar thereby enhancing ti solubility in basins with supply of immature sediment from granitic terranes and important diagenesis by meteoric water the assumption that ti is an immobile element and that rutile or other titania minerals are exclusively of detrital origin may not be valid probable mesodiagenetic titania has low p content suggesting that ti mobility under these conditions was facilitated by some other agent probably organic acids the results of this study illustrate that even in cases where titania minerals are volumetrically insignificant their microtextures and trace element chemistry can provide important insights into the character of fluid flow during diagenesis of siliciclastic rocks

the fluctuating longshore pressure gradient on the pacific northwest shelf a dynamical analysis abstract the majority of papers on pacific northwest shelf dynamics have emphasized the relationship between longshore wind stress 3 and longshore velocity v however attempts to illustrate a balance of momentum in the longshore direction have not been encouraging 3 sol h where h is water depth has insufficient magnitude to balance the vertically averaged longshore acceleration vt at least during summer in this paper it is demonstrated that the missing momentum is provided by the longshore pressure gradient force py the pressure gradient was estimated using tide gauge and atmospheric pressure data at stations separated by roughly 400 km seasonal and long term means from hickey and pola and in some cases nonseasonal monthly anomalies from enfield and allen were added to the sum of the tide gauge and atmospheric pressure data to form time series of total subsurface pressure the pressure data were multiplied by an offshore deny factor to simulate coastal trapping the analysis was performed

a poleward jet and an equatorward undercurrent observed off oregon and northern california during the 1997 98 el nino abstract the timing and intensity of the effects of the 1997 98 el nino on sea surface temperature sst and coastal sea level along the us west coast are examined using in situ time series measurements and the effects on upper ocean currents on the continental shelf and slope off oregon and northern california are examined using repeated shipborne adcp transects a mid shelf mooring off newport oregon and an hf surface current radar an initial transient positive anomaly was observed in both adjusted sea level and sst during may june 1997 followed by anomalously high coastal sea levels generally strongest during september 1997 through february 1998 and abruptly returned to normal in late february 1998 and by positive temperatures anomalies over the mid shelf that persisted longer into april 1998 low frequency coastal sea level anomalies propagated poleward at 2 1 m s poleward flow over the shelf and slope was enhanced at most depths during the el nino compared with following years northward currents in the upper 12 m over the continental shelf off newport oregon averaged 13 7 cm s stronger during august 1997 through february 1998 than during the same period the following year enhanced poleward flow was present at all latitudes sampled during november 1997 and february 1998 particularly over the continental slope these transects also provided clear views of a fall winter equatorward undercurrent which was both strongest and had the most alongshore similarity of form during the enso finally subsurface intensified anticyclonic eddies originating in the poleward undercurrent appear to be a recurrent feature of the circulation off newport late in the upwelling season

on subinertial oscillations trapped by the juan de fuca ridge northeast pacific spectra of currents measured along the 2100 m deep juan de fuca ridge in the northeast pacific have prominent tidal inertial and weather band 3 7 day period spectral peaks the weather band peak in particular has a number of interesting features it is strongest in close lateral proximity to the ridge and strongest near ridge depth intensification near the ridge is characteristic of trapped motion spectral peak intensities vary seasonally with largest amplitudes occurring in autumn and winter seasonal variation suggests that surface weather is forcing flow at depth together trapping and seasonality indicate opportunistic amplification of oscillatory motion at the ridge at all frequencies forcing topography and stratification together shape current and hydrographic distributions near the ridge effects of those interactions for subinertial motion are quantified here using a primitive equation numerical model forcing period 1 10 days and friction are the principal dependencies examined results show that flow over the juan de fuca ridge can be amplified by factors of 3 4 for diurnal and up to a factor of 7 for weather band frequencies amplification is ridge trapped with effects extending many hundreds of meters upward and extending 5 10 km laterally for 5 day period flow the strength and area of amplification increase with increasing period over the 1 to 10 day period band oscillatory weather band flow leads to vertical velocities on the order of 0 3 cm s 1 on ridge flanks which in turn cause periodic temperature t and salinity s variations with amplitudes of as much as 0 05 c and 0 01 practical salinity units respectively the vertical motion and consequent vertical displacement 100 m lead to isotherms that plunge below the crest alternately each side of the ridge a distribution observed in conductivity temperature depth transect data near the ridge crest cross ridge baroclinic pressure gradients caused by cyclically plunging isopycnals are in near geostrophic balance with the coriolis force associated with along ridge flow along ridge current amplification is therefore closely tied to isopycnal movement up and down ridge flanks since weather band oscillations lead to much larger cross ridge baroclinic pressure gradients than do diurnal motions of the same amplitude weather band forcing causes greater along ridge current amplification results vary strongly with forcing period and direction of forcing with respect to the ridge but depend only moderately on friction and turbulent mixing coefficients

the co evolution of fe oxides ti oxides and other microbially induced mineral precipitates in sandy sediments understanding the role of cyanobacteria in weathering and early diagenesis abstract changes in composition during the transition from sediment to rock are usually attributed to long complicated histories and atmospheric influences while the contribution of benthic mat building cyanobacteria is not typically considered here the goal is to understand the influence of cyanobacterial mats on mineral weathering in postdepositional settings of sandy shallow subaquatic environments laboratory incubation experiments were done using ilmenite sands and ilmenite enriched quartz sands colonized by cyanobacterial mats for five months at three temperatures 25 c and 37 c representative of postdepositional weathering regimes and 70 c corresponding to early diagenesis as a comparative control to represent abiotic processes ilmenite sands and ilmenite enriched quartz sands were also subjected to the same conditions without cyanobacterial colonization the precipitation of minerals on cyanobacterial cells and extracellular polymeric substances eps as well as the phase changes in natural ilmenites fetio3 were documented to determine if cyanobacteria influence mineral reaction pathways the precipitates ilmenite grains and permineralized cells were analyzed using complementary techniques of scanning electron microscopy sem x ray diffraction xrd and micro raman spectroscopy the results of this study show that a variety of pure and mixed mineral phases precipitate under postdepositional conditions t 70 c in wet sandy environments with or without cyanobacteria akaganeite anatase ankerite lepidocrocite gibbsite kaolinite and natrojarosite formed exclusively in the samples incubated with cyanobacteria in the samples incubated with cyanobacteria more mineral phases formed at 37 c suggesting that cyanobacteria play a greater role in weathering than in early diagenesis sulfate phases that formed in the presence of cyanobacteria differed in chemical composition from the abiotic precipitates as na al mg and si were incorporated into the structures of newly formed biotic phases understanding the possible fate of these precursor mineral phases will help redefine geochemical biosignatures that can be used for the detection of ancient microbial life in sedimentary rocks on earth as well as for future missions exploring life on other planets

the origin of eddy heat fluxes in the northern california upwelling regime observed eddy heat fluxes i e covariances between heat content and horizontal currents are analyzed with moored data from the coastal ocean dynamics experiment it is demonstrated that much of each sampled covariance arises from the separate correlations of currents and temperature with the upwelling variability which is attributed to the particular warming and cooling processes present thus a large part of the observed eddy heat fluxes is wind driven the remainder is consistent with being largely statistical noise in the observed covariance between those parts of the flow and temperature which are not correlated with the upwelling this also suggests that the wind driven part alone might be a better estimate of the ensemble average eddy heat flux

a local time dependent sverdrup balance in the eastern north pacific ocean direct observations of the dynamic balance between time dependent winds and deep ocean currents are described for the eastern north pacific ocean at 42 n 152 w currents from 150 to 4000 meters below the surface at frequencies from 0 01 to 0 1 cycle per day are significantly correlated with the wind stress curl derived from u s navy operational wind fields the horizontal currents are depth independent below 300 meters and they flow parallel to the potential vorticity gradient derived from the earth9s rotation and the large scale bottom topography these characteristics are expected for such periodic motions with horizontal scales larger than 500 kilometers and represent a generalized sverdrup balance between the atmospheric forcing and the oceanic response

hydrogeotechnical characterization of a metallurgical waste this paper presents the results of hydrogeotechnical characterization tests carried out on the metallurgical waste mw from a tailings impoundment located on the terraces of the moa river cuba characterization of the mw includes chemical and mineralogical analysis oedometer tests triaxial tests tensile strength tests determination of the water retention curve and shrinkage and permeability tests the mw which has a grain size distribution similar to that of a silt mainly contains iron and heavy metals minerals and has low plasticity consolidated undrained triaxial tests on remoulded samples indicate a dilative behaviour with a decrease in pore water pressure near failure the material is susceptible to liquefaction when subjected to a cyclic load in the triaxial test hydraulic conductivity soil stiffness and compressive and tensile strength of the mw have an important dependence on the degree of saturation and vary significantly during the drying process the results indicate that during t

permeability function for oil sands tailings undergoing volume change during drying the coefficient of permeability function is an important unsaturated soil property required when modeling seepage and contaminant transport phenomena inaccuracies in the estimation of the permeability function can lead to significant errors in numerical modeling results changes in void ratio and degree of saturation are factors that influence the permeability function presently available methodologies for estimating the unsaturated permeability function make the assumption that there is no volume change as soil suction is changed as a result volume changes are interpreted as changes in degree of saturation the commonly used estimation techniques for the permeability function are reasonable for soils such as sands that experience little volume change as soil suction is changed on the other hand inaccurate results are generated when soils undergo volume change as is the case with oil sands tailings revisions to previous methodologies are proposed to render the estimation of the permeability functio

observations of motional electromagnetic fields during emslab the long period 1 day behavior of the seafloor electromagnetic fields during emslab is considered in detail with an emphasis on interpretation in terms of oceanic motions the study begins with a summary of the physics of motional electromagnetic induction in which the seawater conductivity weighted vertically integrated velocity measured by the horizontal electric field is emphasized using frequency domain methods it is shown that seafloor and terrestrial magnetic variations have similar spectral shapes indicating a common origin but the seafloor electric field is not consistent with either at periods longer than 4 days suggesting an oceanic source the magnetic field variations are highly coherent across the emslab array at periods shorter than 9 days but the similarity decreases at longer periods probably due to long term instrumental drift the seafloor horizontal electric field data exhibit the broadband coherence characteristic of ionospheric sources only at periods shorter than 1 2 days and are essentially incoherent between 4 days and a week except in association with certain propagating wave phenomena the distinction between the depth averaged velocity inferred from the horizontal electric field and its point measurement by the vertical electric field is demonstrated with data some specific properties of the seafloor electric fields are then considered in detail the first of these is a 4 day wave observed to propagate from north to south along the east flank of the juan de fuca ridge the wavelength propagation sense and association with the ridge are all consistent with topographically trapped rossby wave behavior at a zero in the group velocity a second north to south propagating wave is seen at periods of 8 12 days in the middle of the emslab area with a probable wavelength of order 1000 km unresolved low frequency structures in the electric field are also mentioned these observations clearly demonstrate the power of electromagnetic array methods for the study of long period oceanic behavior

stochastically forced current fluctuations in vertical shear and over topography the effects of constant vertical shear of zonal velocity uniform meridional bottom slope and a deep meridional wall representing the mid atlantic ridge on the response of a linear two layer quasi geostrophic ocean to stochastic wind stress curl forcing are investigated the model is motivated by discrepancies in energy levels and distributions between recent observations and a similar model without shear or topography that predicted remote coherences relatively well the results indicate that the presence of mean shear can significantly enhance the wind generation of surface intensified oceanic kinetic energy at frequencies above the zero shear cutoff for free baroclinic waves the primary effect of the sloping topography is enhanced barotropic response near the barotropic topographic sverdrup resonance where topographic and planetary potential vorticity gradients cancel the wall inhibits the barotropic response and increases coherences on the mooring side of the wall remote coherences for 49 day period fluctuations are due to long barotropic waves as in the previous model so the present model only partially reconciles the previous discrepancies

circulation near axial seamount year long moored current measurements from 1987 to 1988 on the saddle 1860 m between axial volcano and brown bear seamount show an oscillating flow with a broadband frequency centered at about 4 days and a long term average flow of about 4 cm s southward the measurements at sill depth also suggest a possible alternating exchange of water north and south of the cobb eickelberg seamount chain with warmer water 0 05 c coming from the north however measurements near the top of the volcano at about 1400 m show a weaker but northward mean flow and the 4 day oscillation barely exists conductivity temperature and depth ctd observations on the east side of the volcano infer possible intensification of southward flow adjacent to the juan de fuca ridge similar to that found with combined ctd and current meter observations about 100 km to the south southward flow is hypothesized along the entire east side of the ridge on the west side the axial brown bear saddle may be near a convergence zone between southward and northward currents which then flow westward the highly energetic environment on the saddle suggests other gaps in the ridge and seamount chains may be important in determining the fate of the hydrothermal effluents the general oceanic flow at the top of the caldera however is more tenuous and the depth of change between these two regimes cannot be determined

wind driven modification of the alaskan coastal current 1 across shelf transects over the eastern flank of barrow canyon were obtained in august 2005 with an autonomous underwater vehicle auv here the shelf topography creates a choke point in which a substantial portion of pacific inflow from the bering strait is concentrated within 30 km of the coast providing an ideal setup for monitoring the flow with the auv four transects extending 10 km offshore of barrow alaska inshore of the 80 m isobath were used in conjunction with a process oriented numerical model to diagnose the wind driven modification of the alaskan coastal current poleward transports of 0 12 sv were consistent among all sections although the transport weighted temperature was about 1 c colder in the transect obtained during peak winds an idealized numerical model reproduces the observed hydrographic structure and across shelf circulation reasonably well in that 1 winds were not sufficient to reverse the poleward flow 2 upwelling was most pronounced in the nearshore and 3 the onshore return flow occurred throughout the interior as opposed to the bottom boundary layer the across shelf circulation provides a possible mechanism for a meltwater intrusion observed on the offshore side of the auv transect made during peak winds also of interest is that the observed anticyclonic shear was much stronger u y f than previously measured in the region

observations of wind forced deep ocean currents in the north pacific this study examines the atmospheric response of the deep ocean using 200 instrument years of moored current measurements from across the breadth of the mid latitude north pacific we have found evidence of a seasonal modulation in the ocean eddy kinetic energy beneath the thermocline at several locations north of 35 n this modulation is often in phase with the local atmospheric forcing function at frequencies between 0 1 and 0 01 cpd correlations between the local wind stress curl and the deep currents have been found for a few locations the local forced response is parallel to the potential vorticity gradient f h and consistent in amplitude with a local topographic sverdrup balance nonlocal forcing in the form of flow along isolines of potential vorticity has been estimated and it is comparable to the observed flow at some locations but the modeled flow is not correlated with the observations throughout the mid latitude north pacific the bottom slope tends to enhance the effect this suggests that topography narrows the available bandwidth for forced barotropic rossby waves facilitating a quasi steady topographic sverdrup response over most of the basin however the enhanced effect reduces the magnitude of the ocean s response to wind forcing nonlocally forced sverdrup currents flow along isolines of f h are the dominant component but are only of the order of 1 cm s 1 locally forced sverdrup currents flow across isolines of f h are typically of the order of 0 1 cm s 1 rms and are not commonly measured hence these wind forced variations are a background level signal in the mid latitude eddy kinetic energy in a few isolated areas the bottom slope reduces the effect in these regions the local sverdrup response is amplified and has been observed

the marine layer off northern california an example of supercritical channel flow abstract during the spring and summer northerly winds driven by the north pacific high pressure system are prevalent over the northern california continental shelf only interrupted for periods of a few days when weak or southerly winds occur in the course of the coastal ocean dynamics experiment code fixed station and observations were made to describe the temporal and spatial structure of the lower atmosphere and their relation to the strong upwelling of coastal waters in a region extending up to 40 km offshore and 100 km along the coast these observations suggest that atmospheric conditions during the spring and summer usually fall into one of three categories the surface wind can be everywhere weak pattern 1 it can blow at large speeds in a uniform pattern pattern 2 or finally the structure of the northerly surface wind can be complex with large changes in the wind speed and corresponding changes in the surface pressure over short spatial scales pattern 3 the latter pattern which o

predicting bimodal soil water characteristic curves failure of colluvial soil deposits induced by rainfall is a common geohazard in the natural terrain many colluvial soils are widely and gap graded with a minimal sand fraction in order to study the pore water pressures in such gap graded unsaturated soil deposits through a seepage analysis and to evaluate the stability of these soil deposits the soil water characteristic curves for gap graded soils must be known usually gap graded soils exhibit bimodal grain size and pore size distributions this technical note presents a theoretical continuum method for the determination of soil water characteristic curves for soils with a bimodal or multimodal pore size distribution based on the capillary law the water content in a multimodal soil is equal to the sum of water stored in each pore series in the soil therefore the bimodal or multimodal soil water characteristic curves can be obtained by combining the unimodal soil water characteristic curves for all components of the soil corresponding to the pore series weighted by the respective volumetric percentages the proposed method is verified using experimental soil water characteristics data of sand diatomaceous earth mixtures with dual porosity

behavior of coarse widely graded soils under low confining pressures colluvial soils are usually coarse and widely graded shallow seated failures occur frequently in colluvial soil deposits duringrain fallinfiltration thispaperinvestigatesthebehaviorofcoarse widelygradedsoilsunderverylowconfiningpressuresof5e25 kpa encountered in shallow seated failures isotropic consolidation tests drained triaxial tests and undrained triaxial tests were conducted on several widely graded soils with different coarse contents but with the same void ratio of 0 62 with increasing coarse content the soil microstructure changes froma fines controlledstructuretoacoarse controlledstructureafteracriticalcoarsecontentofapproximately70 siltysandwithgravelwith acoarsecontentclosetothecriticalvalueexhibitsthehighestcompressibilitybecauseofthepresenceoflargeinteraggregatepores evenunder very low confining pressures such soil still shows strong contractive behavior during drained loading and generates large positive pore water pressures during undrained loading this explains why shallow seated failures occur frequently in colluvial soil deposits caused by rainfall infiltration soilswithlowerorhighercoarsecontentsthanthecriticalvaluemayshowdilativebehaviorunderthesamelowconfiningpressures the critical statefriction angle increases with thecoarse content doi 10 1061 asce gt 1943 5606 0000755 2013american society of civil engineers ce database subject headings coarse grained soils compression landslides microstructure shear strength soil compaction soil pressure

oxygenated mesoproterozoic lake revealed through magnetic mineralogy terrestrial environments have been suggested as an oxic haven for eukaryotic life and diversification during portions of the proterozoic eon when the ocean was dominantly anoxic however iron speciation and fe al data from the ca 1 1 billion year old nonesuch formation deposited in a large lake and bearing a diverse assemblage of early eukaryotes are interpreted to indicate persistently anoxic conditions to shed light on these distinct hypotheses we analyzed two drill cores spanning the transgression into the lake and its subsequent shallowing while the proportion of highly reactive to total iron fehr fet is consistent through the sediments and typically in the range taken to be equivocal between anoxic and oxic conditions magnetic experiments and petrographic data reveal that iron exists in three distinct mineral assemblages resulting from an oxycline in the deepest waters reductive dissolution of iron oxides records an anoxic environment however the remainder of the sedimentary succession has iron oxide assemblages indicative of an oxygenated environment at intermediate water depths a mixed phase facies with hematite and magnetite indicates low oxygen conditions in the shallowest waters of the lake nearly every iron oxide has been oxidized to its most oxidized form hematite combining magnetics and textural analyses results in a more nuanced understanding of ambiguous geochemical signals and indicates that for much of its temporal duration and throughout much of its water column there was oxygen in the waters of paleolake nonesuch

vertical deformation monitoring at axial seamount since its 1998 eruption using deep sea pressure sensors pressure measurements made on the seafloor at depths between 1500 and 1700 m at axial seamount an active submarine volcano on the juan de fuca ridge in the northeast pacific ocean show evidence that it has been inflating since its 1998 eruption data from continuously recording bottom pressure sensors at the center of axial s caldera suggest that the rate of inflation was highest in the months right after the eruption 20 cm month and has since declined to a steady rate of 15 cm year independent campaign style pressure measurements made each year since 2000 at an array of seafloor benchmarks with a mobile pressure recorder mounted on a remotely operated vehicle also indicate uplift is occurring in the caldera at a rate up to 22f1 3 cm year relative to a point outside the caldera the repeatability of the campaign style pressure measurements progressively improved each year from f15 cm in 2000 to f0 9 cm in 2004 as errors were eliminated and the technique was refined assuming that the uplift has been continuous since the 1998 eruption these observations suggest that the center of the caldera has re inflated about 1 5f0 1 m thus recovering almost 50 of the 3 2 m of subsidence that was measured during the 1998 eruption this rate of inflation can be used to calculate a magma supply rate of 1410 6 m 3 year if this rate of inflation continues it also suggests a recurrence interval of 16 years between eruptions at axial assuming that it will be ready to erupt again when it has re inflated to 1998 levels d 2005 elsevier b v all rights reserved

ocean currents at axial volcano a northeastern pacific seamount 1 axial volcano is a magmatically active seamount that straddles the juan de fuca ridge jdfr with a summit depth of 1400 m the volcano intercepts deep ocean flows at a height well above that of the linear ridge adjoining it to the north and south multiyear yearlong observations of currents at axial show that mean flow circles the seamount in an anticyclonic sense consistent with dynamical constraints with means as large as 6 6 cm s 1 spectra of currents indicate prominent tidal inertial and in some cases weather band period 3 to 7 day peaks as has been seen elsewhere along the jdfr ridge for k1 o1 and s2 tidal currents at the seamount amplitudes are several times larger than the corresponding background amplitudes and rotation around the tidal current ellipses is anticyclonic m2 tidal currents show none of the same properties energy at the inertial frequency decreases by more than an order of magnitude from 100 m above to 400 m below the volcano s summit in contrast weather band wb period energy increases tenfold over the same depth range with wb energy all but unobservable at summit depth the presence of wb oscillations makes axial unlike other seamounts where long observations have been made the current meter observations also provide a picture of seasonal trends as expected during the period summer 1996 to spring 1997 largest amounts of wb energy are found during autumn and winter in contrast wb motion at axial volcano during winter 2000 was summer like in intensity a linear baroclinic model of forced damped azimuthal mode one oscillatory flow around an idealized axisymmetric seamount shows that amplification of diurnal flow should occur principally at the seamount summit while amplification of the wb should occur as the observations show on the seamount flanks model and measured phase relationships for temperature and current time series pairs circumscribing axial support the view that azimuthal mode one oscillations are prominent over the 0 8 to 6 day range for forcing period tc the model indicates that the principal topographic resonance as indicated by kinetic energy ke amplification occurs for a tc greater than 1 and less than 2 days with only mild dependence in that range on background stratification and seamount shape additional but weaker topographic resonances can occur at longer periods in model results but as tc becomes slightly larger than the frictional timescale topographic resonances no longer appear high dissipation and thus short frictional timescales reported by others in regions of rough sloping topography make topographic resonances at axial at periods greater than a few days somewhat unlikely the relatively broad wb spectral peaks at some axial sites are consequently more likely the result of spectral peaks in forcing than of topographic resonance

tio2 accessory minerals coarsening and transformation kinetics in pure and doped synthetic nanocrystalline materials abstract in this paper we review the distribution composition and relationships among the four tio2 minerals anatase brookite rutile and tio2 b and discuss the possible importance of a fifth phase tio2 ii which has a stability field at high pressure we also consider the geological application of kinetic data for the anatase to rutile transformation previous experimental studies of this reaction were carried out between 610 and 1000 c extrapolation using reported rate laws over geologic time results in predicted and natural distribution patterns that are broadly consistent experimental data reported here show enhanced anatase rutile transformation rates if the anatase is very finely crystalline we attribute the rapid transformation in these materials to a lower activation energy 60 kcal mol 1 compared to 80 148 kcal mol 1 reported previously rapid coarsening accompanies early rapid transformation declining coarsening rates correlate strongly with declining transformation rates and extrapolate to those calculated from published data for coarsely crystalline material the first formed crystals of rutile have average volumes approximately eight times greater than those of coexisting anatase suggesting that anatase must achieve a critical particle size before it transforms to rutile dopants can affect both coarsening and transformation rates y 1 retards both coarsening of anatase and its transformation to rutile however cr and ta have very little effect on coarsening rates but significantly reduce transformation rates cr in anatase lowers both the transformation activation energy 47 kcal mol 1 and the frequency factor 1011 hr 1 together these result in comparable transformation rates at temperatures 50 c higher than in pure anatase ta exerts a similar effect the distribution of the impurities within particles vs on the surface may largely explain differences between y and ta or cr results suggest that quantification of the dependence of the transformation kinetics on impurities may allow the interpretation of anatase rutile distribution patterns to provide time temperature information in low grade metasediments

sea level response to enso along the central california coast how the 1997 1998 event compares with the historic record abstract long term monthly sea level and sea surface temperature sst anomalies from central california show that during winter months positive anomalies are associated with el nino events and the negative ones with la nina events there is no significant impact on monthly mean anomalies associated with pacific decadal oscillations although there is a tendency for more extreme events and greater variance during positive decadal oscillations the very strong 1997 1998 el nino was analyzed with respect to the long term historic record to assess the forcing mechanisms for sea level and sst beginning in the spring of 1997 we observed several long period 30 days fluctuations in daily sea level with amplitudes of over 10 cm at san francisco california fluctuations of poleward long period alongshore wind stress anomalies awsa are coherent with the sea level anomalies however the wind stress cannot entirely account for the observed sea level signals the sea level fluctuations are also correlated with sea level fluctuations observed further south at los angeles and tumaco columbia which showed a poleward phase propagation of the sea level signal we suggest that the sea level fluctuations were to a greater degree forced by the passage of remotely generated and coastally trapped waves that were generated along the equator and propagated to the north along the west coast of north america however both local and remote awsa can significantly modulate the sea level signals the arrival of coastally trapped waves began in the spring of 1997 which is earlier than previous strong el nino events such as the 1982 1983 event

low frequency waves in the santa barbara channel observed by high frequency radar are antisymmetric with a mean propagation speed of 5k m d 1 and relative vorticity of order 0 1 f complex empirical orthogonal function decomposition in the 10 20 day passband partitions variance into two dominant modes the first mode represents the vortices with an average period of 14 4 days the second mode represents alongshore fluctuations with an average period of 13 3 days amplitude functions of the two modes correlate with in situ current time series at 5 and 45 m depths obtained from moorings at the east and west channel entrances suggesting coupling with the larger scale circulation of the northern southern california bight the observations support interpretation of mode 2 as a coastal trapped wave since the period and alongshore flow are consistent with previous observations and predictions we hypothesize that mode 1 is a resonant response of the santa barbara basin in the form of a trapped topographic rossby mode the spatial mode resembles the predicted pattern based on a simplified analytical model of the fundamental mode the amplitude of mode 1 is consistently large when the frequencies of modes 1 and 2 converge suggesting that the vortices are a basin scale resonant response to coastal trapped waves index terms 4520 oceanography physical eddies and mesoscale processes 4512 oceanography physical currents 4508 oceanography physical coriolis effects 4516 oceanography physical eastern boundary currents 4544 oceanography physical internal and inertial waves keywords propagating eddies santa barbara channel coastal trapped waves citation beckenbach e and l washburn 2004 low frequency waves in the santa barbara channel observed by high frequency radar j geophys res 109 c02010 doi 10 1029 2003jc001999

a seasonal signal in ocean currents to abyssal depths long term 9 32 month current meter records from the eastern north atlantic 41 n 59 n suggest that remote from the influence of the western boundary current eddy kinetic energy ke at all depths is principally a function of wind stress and stratification generated during the winter and early spring propagating to abyssal depths and decaying to a minimum in late summer although this seasonal variation in ke has not previously been described from the midlatitude ocean some theoretical basis for it is presented

the barotropic response of the subpolar north pacific to stochastic wind forcing in a recent observational study koblinsky et al 1989 attempted to demonstrate that the topographic sverdrup balance can account for mesoscale current fluctuations with periods between 10 and 100 days in the abyssal north pacific however the topographic sverdrup balance proved difficult to verify systematically over the north pacific in this paper the conditions required to obtain the topographic sverdrup balance are investigated through numerical experiments with a stochastically forced barotropic quasi geostrophic numerical model of the subpolar north pacific in the numerical experiments the topographic sverdrup balance emerges from area averages of the terms in the vorticity equation but only for periods longer than about 40 days when the averages are taken over 4 4 region this period increases when averages are taken over progressively smaller regions an examination of vorticity balances at individual points along sections through the model domain indicates that the topographic sverdrup balance is not obtained at individual points even for very long period motions the possibility of verifying topographic sverdrup dynamics with oceanic data is considered it is argued that topographically generated small scales in the velocity field reduce the likelihood that the topographic sverdrup balance can be systematically observed in velocity measurements from individual current meter moorings the results suggest that the vorticity balance is complex and that topographic sverdrup dynamics cannot be expected to provide an adequate explanation for the seasonal modulation of the abyssal eddy kinetic energy that is observed with moored instrumentation in the north pacific

normal modes of the world ocean part ii description of modes in the period range 8 to 80 hours abstract we have calculated normal modes with period between 8 and 80 h for a domain consisting of the arctic atlantic indian and pacific oceans in this period range the numerical model has 56 modes of which 13 are topographic vorticity waves all slower than 30 h the trapping sites for these modes are the siberian shelf the icelandic plateau the grand banks the falkland plateau and patagonian shelf the kerguelen plateau the new zealand and fiji plateaus and the hawaiian ridge predominantly planetary vorticity waves do not appear in the model at periods less than 80 h the 41 modes found between 30 and 8 h include basin modes in the north atlantic indian and equatorial pacific quarter wave resonances in the arabian sea bay of bengal and gulf of guinea and kelvin waves on the antarctic coast the pacific north american coast and the new zealand coast several vorticity and gravity modes exhibit an eastward circumglobal flow of energy that is confined to equatorial latitudes except where defl

authigenesis of titanium minerals in two proterozoic sedimentary rocks from southern and central sweden abstract the occurrence of authigenic titanium minerals rutile anatase brookite and sphene is recorded in two sequences of sedimentary rocks of proterozoic age namely the visingso group and the dala sandstone formation the rocks are sandstones shales and carbonates due to diagenesis of the visingso group and diagenesis to low grade metamorphism of the dala sandstone formation the unstable titanium bearing minerals mostly biotite and ilmenite released their titanium this titanium was involved in the formation of different titanium minerals either on the altered detrital particles mostly biotite and ilmenite or in pore spaces these titanium minerals are often found to attack silicate minerals such as quartz and feldspars due to higher temperature and pressure euhedral sphene a d rutile are more common in the dala sandstone formation

wind forced variability of the deep eastern north pacific observations of seafloor pressure and abyssal currents data from an array of bottom pressure gauges and a string of current meters in the vicinity of 47on 139ow are used to examine the deep ocean variability forced by ocean surface wind stress curl from august 1987 to june 1988 bottom geostrophic currents are computed from the pressure gauge array and these correspond well to the long period directly measured currents at 3000 m the supratidalperiod bottom pressure variations are coherent at 95 confidence with the wind stress curl in period bands of 3 4 days and 15 60 days but removed in distances of 400 and 700 km to the northwest and the southeast respectively a linear two layer hydrodynamic model is used to examine the theoretical forcing produced by random phased surface wind fields for the conditions of the eastern north pacific and the 15 to 60 day period observed response is reproduced credibly to model 3 to 15 day variations more realistic models are required currents are related to surface winds were derived from yearlong current meter records in a cluster of moorings north and east of barbados koblinsky and niiler 1982 showed that significant coherences existed between the 4 to 40 dayperiod east west pulsations of the trade winds r x above barbados and the north south currents v at all depths in the ocean at 15on 54ow the response amplitude of v to r x was depth and period dependent it decreased by a factor of 3 from 150 to 4000 m depths and increased by a factor of 5 from 8 to 40 day periods the interpretation of these data was that the deep ocean forcing was produced by large horizontal scale wind stress curl hereinafter referred to simply as curl due to westward propagating pulses in the trade winds with larger east west than north south scale the amplitude of the deep wind related currents was 1 3 cm s thus deep ocean forcing should be observable in many places where the mesoscale eddy energy is low theoretically wind forced deep ocean motions should depend upon wind stress curl mt iller and frankignoul 1981 using a model of randomly forced linear motions in a stratified infinite flat bottom beta plane ocean computed local coherences and showed that motions across the planetary vorticity gradient should exhibit the strongest coherence with the local wind stress curl niiler and koblinsky 1985 using current meter data demonstrated that such a dynamical link does in fact exist locally at 42on 152ow although at a shorter period than was predicted by milller and frankignoul both the amplitude and the phase of the currents that were forced across the planetary potential vorticity field orf h contours on a 150 km horizontal scale were predicted from the local surface wind stress computed from a similar 150 km scale wind field the 4000 m oscilla

application of remote wind forced coastal trapped wave theory to the oregon and washington coasts abstract the theory of coastal trapped waves generated by remote wind forcing clarke is used to calculate coastal subsurface pressure ssp and longshore velocity along the oregon and washington coasts for three two month periods summer of 1972 summer of 1978 and winter of 1977 the response in ssp and longshore velocity is assumed to be dominated by the mode one wave in every case coherence squared between observed and modeled ssp is significant at the 95 level over the entire low frequency band 0 2 cpd with an average phase difference less than 30 greater than 80 of the variance in coastal ssp is accounted for by the mode one coastal trapped wave ctw the ssp response off washington and oregon during summer is primarily 35 of the variance a result of wind forcing between san francisco and cape mendocino california wind stress in this region during summer is significantly larger than that off oregon and washington at low frequencies so that the ctw generated off california propagate

evidence for wind driven current fluctuations in the western north atlantic two subsurface current meter moorings were deployed for 20 months along 70 w in a low energy portion of the western north atlantic the resulting data were compared with estimates of the wind stress curl in an attempt to seek a relationship between currents below the mixed layer and meteorological forcing at subinertial frequencies currents and temperature tend to be significantly coherent with the curl and are most coherent with the curl at remote locations usually more than 500 km away from the mooring and generally to the east coherences generally decrease with increasing frequency the current response is surface intensified a linear stratified model for stochastically wind forced rossby waves in a flat bottomed ocean is presented as an attempt to rationalize the results the effort was not entirely successful so that it appears that a more realistic model perhaps including bottom topography and mean currents will be needed to rationalize these observations fully

microporosity structure of coarse granular soils to date the microporosity structures of coarse soils with various coarse fines contents are still not fully understood in this study the pore size distributions psds of five types of soil varying from gravel to clay were characterized using mercury intrusion porosimetry the soil with a coarse content below 70 i e fines content above 30 is found to have a fines controlled microstructure which is sensitive to water content changes such soil forms a dual porosity structure due to compaction in which both intraaggregate pores and interaggregate pores are dominant after saturation the dual porosity structure evolves into a unimodal porosity structure dominated by the intraaggregate pores during drying such soil exhibits a significant reduction of total volume the soil with a coarse content above 70 instead has a coarse controlled microstructure which is stable upon water content changes such soil maintains dual porosity structures no matter if the soil is compacted saturated or dried as an example of application the measured psds are used to predict the soil water characteristic curves swccs for the test soils and the predictions are consistent with the swccs measured in the laboratory

wetting front advancing column test for measuring unsaturated hydraulic conductivity unsaturated hydraulic conductivity is the primary soil parameter required when performing seepage analyses for unsaturated saturated soil systems unsaturated hydraulic conductivity is also one of

currents forced by stochastic winds with meridionally varying amplitude motivated by discrepancies between observations and previous theory we present a stochastically forced model of wind driven current fluctuations that includes the observed northward intensification of wind stress curl a feature absent from a previous model the model is linear barotropic and quasi geostrophic it is bounded by absorbing walls along lines of constant latitude in the north and south and is unbounded east and west the northward wind intensification causes a northward bias in the coherence of wind stress curl and currents that is similar to that observed art unanticipated secondary maximum occurs northeast of the mooring in the low frequency 37 day period meridional velocity coherence predictions