instability waves in the equatorial atlantic ocean abstract evidence is presented for the generation of planetary waves by barotropic instability within the cyclonic shear region of the atlantic ocean s south equatorial current sec immediately following the springtime intensification of the southeast trade wind which accelerates the sec westward a packet of waves with central periodicity of around 25 days is observed lasting for about three cycles independent wavenumber analyses on 1983 and 1984 data give newly identical zonal wavelengths and phase speed estimates of around 1100 km and 50 cm s 1 the waves are anisotropic and spatially inhomogeneous with generation confined primarily to the mixed layer an energetics analysis using 1983 data centered upon the equator at 28 w shows a rapid increase in total perturbation energy tpe reaching values of 2000 erg cm 3 within two weeks the subsequent decrease in tpe at this location is due primarily to meridional pressure work divergence baroclinic instability is negligible because both the meridional

the unpredictable nature of internal tides on continental shelves abstractpackets of nonlinear internal waves nliws in a small area of the mid atlantic bight were 10 times more energetic during a local neap tide than during the preceding spring tide this counterintuitive result cannot be explained if the waves are generated near the shelf break by the local barotropic tide since changes in shelfbreak stratification explain only a small fraction of the variability in barotropic to baroclinic conversion instead this study suggests that the occurrence of strong nliws was caused by the shoaling of distantly generated internal tides with amplitudes that are uncorrelated with the local spring neap cycle an extensive set of moored observations show that nliws are correlated with the internal tide but uncorrelated with barotropic tide using harmonic analysis of a 40 day record this study associates steady phase motions at the shelf break with waves generated by the local barotropic tide and variable phase motions with the shoaling of distantly generated internal tides

energy transport by nonlinear internal waves wintertime stratification on oregon s continental shelf often produces a near bottom layer of densefluid that acts as an internal waveguide on which nonlinear internal waves propagate shipboard profiling and bottom lander observations capture disturbances that exhibit properties of internal solitary waves bores and gravity currents wave like pulses are highly turbulent instantaneous bed stresses are 1 n m 2 resuspending bottom sediments into the water column and raising them 30 m above the seafloor the waves cross shelf transport of fluid counters the time averaged ekman transport in the bottom boundary layer in the nonlinear internal waves we have observed the kinetic energy is roughly equal to the available potential energy and is o 0 1 mj per m of coastline the energy transported by these waves includes a nonlinear advection term huei that is negligible in linear internal waves unlike linear internal waves the pressure velocity energy flux hupi includes important contributions from nonhydrostatic effects and surface displacement it is found that statistically huei 2hupi vertical profiles indicate that up z is more important in transporting energy near the seafloor while ue z dominates farther from the bottom with the wave speed c estimated from weakly nonlinear wave theory it is verified experimentally that the total energy transported by the waves hupi huei chei the high but intermittent energyflux by the waves is in an averaged sense o 100 w per m of coastline this is similar to independent estimates of the shoreward energy flux in the semidiurnal internal tide at the shelfbreak

stochastic inversion of thermal data in a sedimentary basin resolving spatial variability summary the concept of spatial stochastic processes and the techniques of geostatistics and stochastic inversion are presented as a means for evaluating the spatial variability of thermal properties and temperature in sedimentary basins data from the uinta basin of ne utah are used to demonstrate the analysis bottom hole temperatures from oil and gas wells provide the best opportunity for a spatial analysis because of the large number and wide distribution of data errors in bottom hole temperatures are not too large to preclude their use and stochastic inversion provides an optimum method for removing random noise while retaining spatial resolution corrected bottom hole temperatures from 235 wells in the uinta basin are used to estimate a average geothermal gradient as a function of position in the basin and b temperature gradients in individual formations also as a function of position in the basin the latter analysis yields a high resolution estimate of temperature gradient and temperature throughout the basin the temperature field shows variations of up to 50 c at a depth of 4 km and is estimated to be accurate to better than 5 c this variation in temperature is consistent with conductive and advective mechanisms of heat transfer in a heterogeneous medium

geophysical and petrological evidence for the presence of an anomalous upper mantle beneath the sahara basins algeria abstract north of 20 n the northwest part of the stable african shield is characterized by an anomalous high heat flow zone 80 110 mw m 2 this east west elongated zone is oblique to major proterozoic structural units and cannot be related to differences in crustal heat production maximum heat flow occurs in the southern part of the sahara basins 100 120 mw m 2 only a mantle heat flow contribution of 60 70 mw m 2 can account for this very high surface heat flow the estimated geotherms suggest that the temperature of upper mantle is anomalously high and partial melting may be present at shallow depths this hypothesis is supported by the existence of a long wavelength negative component of the gravity field that corresponds with the high heat flow axis and with the very low lithospheric s wave velocities 4 2 4 4 km s down to 160 km obtained from surface wave studies in addition the chemistry of the scarce cenozoic melilitite lavas illizi volcanic district geographically associated with the thermal anomaly as well as the mineralogy of their inclusions phlogopitized garnet spinel peridotite and alkali clinopyroxenite show that the upper mantle beneath this region is locally highly metasomatised and partially melted from these preliminary results it appears that the northwest african upper mantle has been modified by recent thermal rejuvenation processes including gas transfer that are likely to be more extensive in the southern part of the sahara basins

seafloor pressure measurements of nonlinear internal waves highly resolved pressure measurements on the seafloor over new jersey s continental shelf reveal the pressure signature of nonlinear internal waves of depression as negative pressure perturbations the sign of the perturbation is determined by the dominance of the internal hydrostatic pressure p 0 due to isopycnal displacement over the contributions of external hydrostatic pressure 0gh h is surface displacement and nonhydrostatic pressure p 0 each of opposite sign to p 0 this measurement represents experimental confirmation of the wave induced pressure signal inferred in a previous study by moum and smyth

reflection of the internal tide in upper loch linnhe a scottish fjord abstract results from an observational study of the internal tide of upper loch linnhe a fjord on the west coast of scotland are presented between november 1992 and june 1993 moorings containing current meters measuring velocity temperature and salinity were deployed at two sites in the loch observations of the horizontal velocities show the presence of an energetic first mode linear internal tide at the m 2 frequency with surface amplitudes of up to 0 57 m s 1 cf 0 03 m s 1 for the barotropic component independent evidence of the m 2 internal tide is provided by vertical velocities inferred from salinity and temperature variations in june 1993 an undulating ctd was used to study the horizontal propagation of the semi diurnal internal tide the results show that over the inner reaches of the loch the internal tide behaves as a standing wave with a large proportion of the internal tide energy being reflected at the landward end of the loch using the phase relationship between the velocity components from the mooring data it is demonstrated that there is a significant standing wave component present throughout the 7 month observational period closer to the sill the undulating ctd observations show the formation of an intense hydraulic jump on the flood tide suggesting the area immediately landward of the sill to be a region of complicated dynamics and high dissipation

tracking solitary waves below land fast ice 1 data from two acoustic doppler current profilers separated by 76 m and deployed through land fast ice in the canadian arctic archipelago in may 2002 are examined the three velocity components were sampled intermittently at 1 minute intervals over a 3 week period to 19 m below the ice water interface the vertical structure was resolved using empirical orthogonal functions eof while the shallow water korteweg de vries kdv and deep water benjamin ono bo theoretical solutions were used to guide a pseudo wavelet analysis of the horizontal structure numerous instances of near simultaneous spikes were detected in the empirical mode 1 time series a 3 5 hour period on 21 may 2002 containing two disturbances was examined in detail wavelet scalograms suggested that there was a 20 minute lag in the first disturbance and 16 minutes in the second the scalogram values indicated that kdv was more consistent with the waveshapewave shapes than bo theory the character of the two events was very different the first had a broader spatial distribution than the second and the measured translational speed was reasonably consistent with that of a mode 1 kdv solitary wave the second event had a much slower propagation speed and a near surface maximum in the vertical velocity eigenvector suggesting a mode 2 wave it is suggested that ice keels from a nearby pressure ridge could be the source

heat flow of the eastern canadian rifted continental margin revisited continental shelves are regions where heat flow is not measured directly by conventional marine techniques but estimated from oil exploration data with possible bias in order to overcome this problem we recently proposed a method based on neural networks geophys j int 2006 166 115 that provides better constraints on thermal conductivity it allowed us to derive 161 heat flow estimates on the eastern margin of canada where previous studies had concluded to the existence of heat flow higher than that in the adjacent continent and ocean we conversely found rather homogeneous values 45 55 mw m 2 all along and across the margins from labrador to nova scotia the difference seems essentially related to the porosity of sediments that was not taken into account in previous studies our results support a high asymmetry for the conjugate iberian canadian margins and could indicate that mantle heat flow increases abruptly from the canadian shield to the margins

the thermal regime of south african continental margins abstract we present thermal data from 100 oil exploration boreholes on the continental margins of south africa near surface temperature profiles are constrained with temperatures acquired during reservoir tests corrected bottom hole temperatures and seafloor temperatures the thermal conductivity profiles are estimated from geophysical well logs using a neural network method available data allow us to determine 41 new heat flow values computed from depth ranges greater than 1000 m located on the western and southern continental margins of south africa we believe that the variations in surface heat flow are not controlled by the contribution of the sediments or the basement but rather by the mantle heat flow an upper bound of 30 mw m 2 for the mantle heat flow on the interior of the continent can be inferred from the lowest available estimates located near the coastline on the southern continental margin on both continental margins heat flow values reach a maximum of about 60 mw m 2 100 km away from the shore and consistently decrease further away towards values typically encountered in old oceanic domains 50 mw m 2 this indicates that 1 the mantle heat flow increases over a short distance at the edge of the continent which is consistent with studies on the effect of continents on mantle convection and 2 it may increase to a value greater than heat flow on the adjacent ocean as a possible consequence of the effect of the transition between thin oceanic lithosphere and thick and cold continental lithosphere on mantle convection

upwelling rebound ephemeral secondary pycnoclines and the creation of a near bottom wave guide over the monterey bay continental shelf several sequential upwelling events were observed in fall 2012 using measurements from the outer half of the continental shelf in monterey bay during which the infiltration of dense water onto the shelf created a secondary near bottom pycnocline this deep pycnocline existed in concert with the near surface pycnocline and enabled the propagation of near bottom cold semidiurnal internal tidal bores as well as energetic high frequency nonlinear internal waves of elevation iwoe the iwoe occurred within 20 m of the bottom had amplitudes of 8 24 m periods of 6 45 min and depth integrated energy fluxes up to 200 w m 1 iribarren numbers 0 03 indicate that these iwoe were nonbreaking in this region of the shelf these observations further demonstrate how regional upwelling dynamics and the resulting bulk cross margin hydrography is a first order control on the ability of internal waves at tidal and higher frequencies to propagate through continental shelf waters

the morning glory an extraordinary atmospheric undular bore summary observations made during an expedition in october 1980 to study morning glory wind squalfs in the gulf of carpentaria region of northern australia are described during a ten day period in burketown north queensland six squalls were documented on consecutive mornings 8 1 3 october including two moving from the south an apparently unusual direction the unique data gathered from the latter confirm that these have the same character as their north easterly counterparts that is they are undular bores the origin of southerly glories remains uncertain but at least in some cases appears to be linked with the northeast advance of a frontal trough across central australia while the data are equivocal it seems possible that the motion of the front into the developing nqcturnal inversion could generate waves or hydraulic type disturbances which run along the inversion layer ahead of the front as proposed by tepper 1950 the efficacy of such a mechanism is demonstrated by a simple laboratory experiment evidence is presented which suggests that morning glory type events occur elsewhere in the world sometimes as precursors to cold fronts observations in the gulf of carpentaria region show that they are effective triggers of deep convection when they advance into air with a sufficient degree of conditional instability

internal tides observed by an acoustic doppler current profiler abstract previous studies of knight inlet british columbia revealed the presence of a strong internal m2 tide most of the energy was found to be in either the first or second dynamic modes due to difficulties in sampling of the surface layer objective estimates of the distribution of tidal energy and reflection coefficients until now have been impossible to obtain during june and july 1989 an intense acoustic doppler current profiler adcp sampling of the inlet was conducted these results are used to show the existence of a strong semidiurnal flow in the baroclinic field the authors propose that the horizontal phase information inherent in the spatial sampling by the adcp can be used to resolve the distribution of energy between dynamic modes through a least squares fit of the data to a simple free wave propagation model of the inlet the authors arrive at objective estimates of the distribution of m2 internal tide energy the fitting procedure is found to be sensitive to fluctuations in the

a linear relationship between enso intensity and tropical instability wave activity in the eastern pacific ocean the interannual variations of tropical instability waves tiws in the eastern pacific ocean and their relationships with enso intensity are studied using a 28 year long coupled atmosphere ocean general circulation model cgcm simulation the activity of tiws is measured by the root mean square value of the 50 day high pass filtered sea surface temperature sst perturbations produced in the simulation the cgcm realistically produces two branches of large tiw activity near the equator one at 2 n and the other at 2 s it is found that along both branches there are linear relationships between the year to year variations of tiw activity and those of enso intensity tiw activity is enhanced or reduced in proportion to the nino3 sst anomalies with larger activity in la nina years and smaller activity in el nino years it is found that enso modulates tiw activity in both branches primarily by changing the latitudinal sst gradient associated with the sst front immediately north of the equator weaker correlations are found between the year to year variations of tiw activity and those of the ocean current shears between the south equatorial current and the equatorial undercurrent or the north equatorial countercurrent this cgcm study suggests that the baroclinic instability associated with the northern sst front is a major generation mechanism for both the northern and southern tiw branches in the eastern pacific ocean

formation temperatures determined from stochastic inversion of borehole observations summary hole temperature bht observations are generally influenced by drilling induced thermal disturbances which must be corrected for this paper presents a correction method based on a 1 d conductive finite element model and an inverse procedure for parameter estimation while the technique may be applied to any section of the borehole this paper focuses on the correction of bottom hole temperatures model parameters are mud temperature during drilling and circulation at the depth of bht observations borehole radius thermal parameters of mud and formation and the equilibrium formation temperature data are one or more successive bhts and their standard deviations prior to inversion the model parameters are assigned reasonable values and standard deviations that reflect the confidence in those values a high level of confidence implies small standard deviations and vice versa the process of inversion extracts the most likely values of all free parameters including the equilibrium formation temperature furthermore the initial uncertainties in all parameters and data are propagated into uncertainties in the final parameter estimates the formation temperature estimate is an unbiased estimate of the true formation temperature when the u priori parameter estimates and their standard deviations are consistent with the actual physical conditions in the borehole and the formation the method on average yields 5 10 per cent higher equilibrium temperature estimates than does the horner plot method and displays a strong consistency with temperature obtained during production tests this is of importance to the understanding of terrestrial heat flow density patterns and thermal structure of sedimentary basins and to the modelling of hydrocarbon generation the theory and results from the processing of 41 bht series from 27 industrial wells in the north sea central graben are presented

scale interaction between tropical instability waves and low frequency oceanic flows 1 tropical instability waves tiws prevailing in the tropical pacific and atlantic oceans interact with the low frequency oceanic flow it is known that tiws act as negative feedback to enso through a thermal process in this study we examine the dynamical eddy feedback of tiws we show that in terms of physical processes the dynamical tiw feedback is very similar to the atmospheric synoptic eddy feedback in the extratropics for example the mean seasonal eddy vorticity flux of tiws can be largely explained by the left hand rule which states that eddy vorticity fluxes are predominantly directed toward the left hand side of the oceanic flow therefore they act as positive feedback to the low frequency oceanic flow we also show that the positive eddy feedback is obtained from eddy structure changes induced by the low frequency flow

reliable modelling of the source rock transformation ratio abstract basic modelling results are reliable only if they are accompanied by error bars which reflect modelling uncertainties estimation of error bars by repeated forward calculations monte carlo simulation can be time consuming due to the calculation time of basin models applications in exploration hence call for new techniques in error analysis a fast analytical method has been developed for the calculation of error bars on the source rock transformation ratio the method is a stochastic generalization of the traditional deterministic approach which is reproduced in the deterministic limit of vanishing parameter uncertainties assuming normally distributed errors in the kinetic parameters and in the source rock temperature history the marginal cumulative distribution function of the source rock transformation ratio can be determined at arbitrary times during source rock evolution from this distribution different statistical moments such as the mean standard deviation median and mode of the transformation ratio can be obtained the parameters of the stochastic model comprise the distribution parameters in the joint normal distribution of uncertainty in the average kinetic parameters and standard deviations and correlation scales of uncertainty in the surface temperature history heat flow history thermal resistivity history and burial history the temperature history uncertainty can be reduced by the addition of temperature constraints at specified times e g at the present the marginal cumulative distribution function of the source rock transformation ratio is fast to compute monte carlo simulating the transformation ratio at a particular time during basin evolution hence reduces to drawing random outcomes from the distribution function which is many orders of magnitude faster than recalculating the basin model the method is useful whenever a reliable value or a stochastic simulation of the source rock transformation ratio is needed and can be applied with one two and three dimensional basin modelling systems

lateral dispersion over the continental shelf analysis of dye release experiments lateral dispersion over the continental shelf was examined using dye studies performed as a part of the coastal mixing and optics experiment four experiments performed at intermediate depths each lasting 2 5 5 days were examined in some cases the dye patches remained fairly homogeneous both vertically and horizontally throughout an experiment in other cases significant patchiness was observed on scales ranging from 2 to 10 m vertically and a few hundred meters to a few kilometers horizontally the observations showed that the dye distributions were significantly influenced by shearing and straining on scales of 5 10 m in the vertical and 1 10 km in the horizontal superimposed on these larger scale distortions were simultaneous increases in the horizontal second moments of the dye patches with corresponding horizontal diffusivities based on a fickian diffusion model of 0 3 4 9 m 2 s 1 analysis of the dye data in concert with shear estimates from shipboard acoustic doppler current profiler observations showed that the existing paradigms of shear dispersion and dispersion by interleaving water masses cannot account for the observed diffusive spreading of the dye patches this result suggests that some other mechanisms provided an additional diffusivity of order 0 2 4 6 m 2 s 1 an alternative mechanism dispersion by vortical motions caused by the relaxation of diapycnal mixing events may explain the observed dispersion in some cases

heat flow measurement in lacustrine or oceanic sediments without recording bottom temperature variations water bottom temperature variations btv introduce many uncertainties into heat flow density hfd values determined from the temperature depth t z plot from a one time probe insertion into the top few meters of sediments the btv have to be carefully monitored for a number of years up to the date of the probe measurements this makes the method time consuming and economically unattractive in this paper we present the theory for a promising new technique the method does not require monitoring of the btv but does require at least two t z profiles separated in time by only a few months a generalized inversion of the btv history using the separated t z data and any other a priori information that is available is then performed in the frequency domain to give the most probable bayesian estimates of various parameters and their error bounds numerical examples show that the inversion can resolve not only the hfd but also the mean sediment surface temperature and gives information on the longer term trend as well as details of the btv over the previous year these together with thermal properties structure are the factors that contribute most to the shape of the time dependent t z profiles used in a typical situation where a uniform half space with a background hfd 60 mw m 2 has been perturbed by complex btv with a maximum variation of 1 8 k using a misguessed hfd of 90 100 mw m 2 in the inversion of two t z profiles taken 3 months apart over a 2 to 5 m section results in a posteriori hfd of 58 11 m w m 2 although the technique gives an optimally determined mean hfd its principal value lies in the ability to place reliable error bounds on the mean

observations of polarity reversal in shoaling nonlinear internal waves observations off the new jersey coast document the shoaling of three groups of nonlinear internal waves of depression over 35 km across the shelf each wave group experienced changing background conditions along its shoreward transit despite different wave environments a clear pattern emerges nearly symmetric waves propagating into shallow water develop an asymmetric shape in the wave reference frame the leading edge accelerates causing the front face to broaden while the trailing face remains steep this trend continues until the front edge and face of the leading depression wave become unidentifiable and a near bottom elevation wave emerges formed from the trailing face of the initial depression wave and the leading face of the following wave the transition from depression to elevation waves is diagnosed by the integrated wave vorticity which changes sign as the wave s polarity changes sign this transition is predicted by the sign change of the coefficient of the nonlinear term in the kdv equation when evaluated using observed profiles of stratification and velocity

the pressure disturbance of a nonlinear internal wave train observations from a lander fixed to the seafloor over the continental shelf in 124 m of water provide highly resolved velocity measurements through nonlinear internal waves of elevation from these measurements we determine for the first time the non hydrostatic pressure disturbance p nh in nonlinear internal waves for near bottom waves of elevation ranging in amplitude a from 12 to 33 m the value of p nh evaluated at the seafloor changes sign from 0 to and back in accordance with weakly nonlinear theory peak values of vert p nh vert range from 25 to 90 n m 2 the external hydrostatic pressure disturbance due to the surface displacement eta h is inferred from horizontal accelerations for elevation waves eta h peak values range from 0 1 to 9 mm 1 to 90 n m 2 the internal hydrostatic pressure perturbation p wh caused by isopycnal displacement is inferred from measured streamlines and an ambient density profile its value at the seafloor is 0 for elevation waves peak values range from 100 to 300 n m 2 vert eta h vert and seafloor values of vert p nh vert p wh all increase monotonically with a since vert p nh vert and p wh increase at roughly the same rate with a no clear trend arises in the degree to which waves become more or less non hydrostatic as a changes a distinct bottom pressure signature is determined for bottom trapped nonlinear waves of elevation a wave train consisting of a sequence of positive pressure perturbations dominated by p wh by inference a train of surface trapped nonlinear internal waves of depression will consist of a sequence of negative pressure perturbations a result of this analysis is that significant properties of the waves can be discerned from a simple adequately resolved bottom pressure measurement

an upper limit to palaeo heat flow theory and examples from the danish central graben abstract the surface heat flow yields a condensed expression of the subsurface thermal regime while the present heat flow can be measured as the product of thermal conductivity and temperature gradient resolution of the past surface heat flow variations calls for indirect methods such as the modelling of vitrinite reflectance and other organic maturity indicators which represent integrals of the past temperature history this paper argues that regarding the reflectance of vitrinite which is the most common maturity indicator the feature of the past thermal regime which can survive the effects of measuring and modelling uncertainties is the maximum temperature present or past how the maximum temperature was obtained is only rarely resolved given maximum temperature burial history thermal conductivity structure and surface temperature history the one dimensional steady state heat equation yields an approximate upper limit to the surface heat flow artificial examples show that the past heat flow may be similar to the maximum heat flow constraint when the past was significantly warmer than the present however this requires a delicate balancing of burial history and heat flow history to occur the thermal relaxation rate of the hot past must compensate for heating due to burial generally the past heat flow may be well below the maximum constraint examples from the central graben show that vitrinite reflectance samples of upper jurassic age constrain the maximum palaeo heat flow back to 150 ma this is due to the very rapid and significant sedimentation of upper jurassic sediments resulting in immediate deep burial of vitrinite the data of the present study are consistent with a early cretaceous heat flow elevated by about 20 30 above the present and with a heat flow throughout the cenzoic only marginally higher than the present however the data are also fully consistent with a time independent background heat flow history this illustrates the limits of resolution in palaeo thermal reconstruction based on vitrinite reflectance and temperature data the problem is one of finding the space of admissible solutions rather than one of finding a single solution

internal solitary waves in the warm pool of the western equatorial pacific abstract during the spring tides of late november 1992 early january and early february 1993 solitary internal wave packets were observed at 2 s 156 15 e in the western equatorial pacific apparently generated in the nuguria island group 3 s 153 e the waves propagate northeastward at 2 4 2 8 m s 1 appearing in fixed phase with the underlying semidiurnal baroclinic tide the initial solitary wave crests have downward displacements in excess of 60 m and peak velocities greater than 80 cm s 1 groups of 1 3 crests are observed with vertical structure resembling a first mode internal wave and horizontal variability consistent with third order comb kdv solitons many of the packets exhibit an overall organization reminiscent of undular bores this borelike behavior is confined primarily to the upper 70 m not sharing the mode one dependency of the crests the solitons displace the ambient equatorial currents including the equatorial undercurrent both vertically 80 m and laterally 1 2 km with l

variability of the observed midlatitude storm tracks in relation to low frequency changes in the circulation pattern abstract the principal modes of month to month variability of the wintertime storm tracks over the north pacific and north atlantic are identified by empirical orthogonal function analysis of the root mean square statistics of bandpass 2 5 6 day filtered geopotential height data for 19 yr one of the two leading modes depicts fluctuations in the level of synoptic scale activity without any noticeable spatial displacement of the storm track axes whereas the other mode is associated with meridional shifts of the storm tracks from their time averaged positions higher order modes are indicative of diversion or truncation of cyclone tracks in particular geographical regions it is demonstrated that the leading storm track modes are linked to some of the best known monthly averaged teleconnection patterns the dipolar western pacific and western atlantic patterns for the monthly mean flow are seen to be accompanied by marked changes in the intensity of the storm tracks over the western oceans whereas the m

estimating kinetic parameters for organic reactions from geological data an example from the gippsland basin australia abstract an examination has been made of strategies to estimate kinetic parameters activation energy and pre exponential factor for organic reactions from geological data least squares regression and a direct search algorithm were applied to a set of sterane isomerization data from volador 1 an oil exploration well in the gippsland basin australia the best fit kinetic parameters depend on the number and quality of data points used as well as the thermal history because both the data and thermal history have intrinsic uncertainties a range of kinetic parameters can explain the data to a specified level of misfit for reasonable variations in the thermal history the effective kinetic parameters for the data from volador 1 are e 75 100kj mol and a 10 1 10 5 s it is observed that the range of acceptable parameter pairs has a linear relation of the form ln a a be and the slope b is dependent on the thermal history small departures of either parameter from this relation lead to significant variations in the predicted values for the reaction progress

mise en evidence d importantes variations regionales du flux de chaleur en algerie evaluation of heat flow in 230 oil wells using temperature measurements bottom hole temperature and temperature of fluids in drill stem test and various rock porosity data reveals a high heat flow average 82 19 mw m 2 associated with the algerian sahara basins the isopleth map exhibits significant regional variations overprinted by short wavelength anomalies that in general are related to the local geological structure on a regional scale we observe an essentially north south zonation that is not directly related to the major structural units except for the northern alpine domain the southern area at the border of the hoggar precambrian basement is characterized by very high heat flow values 90 130 mw m 2 the anomalies define a major axis generally east west which seems to affect the northern part of the african plate from the canaries to libya locally some relationships with extensional miocene pliocene quaternary volcanism suggest an association with recent mantle thermal events

the thermal conductivity and heat flow density of the jeanne d arc basin offshore eastern canada abstract in an effort to understand the present day thermal structure of the jeanne d arc basin we derive matrix thermal conductivity values using a geometric mean model from thermal conductivity values of thirteen lithologic end members of which seven are measurements on materials from the jeanne d arc basin and lithological data temperature corrections to thermal conductivity are made for both matrix and pore water in situ thermal conductivities were obtained after correcting for the effect of porosity which we estimated from both lithological information and digital well logs calculated thermal conductivities of the formations range from 1 46 to 2 65 w m 1 k 1 the heterogeneity of formation thermal conductivity is caused by at least two factors the first is lithological variation due to facies change the second is due to different degrees of compaction under compacted intervals overpressure zones are characteristically of lower thermal conductivity the surface heat flow density calculated with an inverse method in seventeen wells varies from 37 8 to 60 7 mw m 2 this study indicates that surface heat flow density values estimated without porosity corrections may be 15 higher than those with porosity corrections we also demonstrate the sensitivity of modelled timing of maturation to thermal conductivity estimations

a climatology of waves in the equatorial region abstract propagating anomalies of moisture and moist deep convection in the tropics are organized into a variety of large scale modes these include but are not limited to the so called intraseasonal oscillations convectively coupled waves similar to those predicted by shallow water theory on the equatorial beta plane and tropical depression type disturbances along with the annual and diurnal cycles these modes act and interact to control much of the variance of tropical convection analyses of 10 yr of outgoing longwave radiation olr and precipitable water pw data are carried out to develop comparative climatologies of these wavelike modes the analysis relaxes the commonly used cross equatorial symmetry constraints which allows study of the portions of the wavelike processes that are asymmetric across the equator mean background states are found for olr and for pw as functions of day of the year examination of anomalies together with the background reveals much about how the waves are affec

internal hydraulic flows on the continental shelf high drag states over a small bank observations of currents hydrography and turbulence provide unambiguous evidence for hydraulic control of flow over an isolated three dimensional topographic feature on oregon s continental shelf the flow becomes critical at the crest of the bank forming a strong supercritical downslope flow in the lower layer farther downstream internal hydraulic jumps form as the bottom flow becomes subcritical as a consequence turbulence is greatly enhanced in the bottom boundary layer in the sheared interface above the swiftly flowing bottom current and in the internal hydraulic jump the dissipation rate of turbulent energy is consistent with the mean energy removal rate for a hydraulic jump in an idealized two layer flow this enhanced turbulence constitutes a high drag state of the flow in which the form drag introduced by the topography exerts significant influence on the flow around it and mixing is increased 102 103 times the background values

the dynamics of low frequency variability in a simple model of the global atmosphere abstract we examine the dynamics of low frequency variability in a simple global model with zonally homogeneous boundary conditions low frequency structure comprises trains of nearly equivalent barotropic rossby waves with weak eastward phase velocities and strong eastward group velocities these low frequency eddies are strongly coupled to synoptic activity the flux of vorticity by synoptic waves acts both to reinforce the low frequency eddies and to retard their eastward propagation mechanistic experiments with an imposed forcing show that the synoptic scale vorticity fluxes are organized by the low frequency flow the behavior is generally similar to that found in previous studies of blocks the present work shows that strong mutual interactions between the low and synoptic frequencies also characterize less dramatic low frequency flows

observations of intratidal variability of flows over a sill contraction combination in a chilean fjord underway velocity measurements were carried out for the first time in a chilean fjord using an acoustic doppler velocimeter with the purpose of elucidating the intratidal variability of flows through a pass paso galvarino the pass included a sill where the bottom sloped by roughly 30 and a coastline contraction of 90 the relatively small dimensions of the pass allowed for rapid sampling of the flow evolution throughout the tidal cycle the backscattered sound signal from the velocimeter and from an echo sounder were used to describe the vertical excursions of the pycnocline throughout the domain and to identify regions of enhanced vertical mixing within the pass the spatial variability of the flow in the pass was consistent with uniform two layer flow at the narrowest section of the contraction the pycnocline dropped sharply around both maximum flood and maximum ebb while the flow accelerated downstream relative to the tidal flow the slope of the pycnocline changed sign from flood to ebb which was atypical of other fjord observations but could be explained by the transitions from subcritical to supercritical flow these transitions switched location at either side of the narrowest section of the contraction leeward of this section increased sound backscatter suggested intensified turbulence that extended over a greater area during ebb than during flood because the distance between the point of pycnocline drop and the end of the pass was longer during ebb enhanced vertical mixing within the pass was reflected in the tidally averaged fields by a three layer flow that consisted of near surface and near bottom flow converging toward the pass and flow around the pycnocline diverging away from the pass

initiation of a solitary wave family in the demise of a nocturnal thunderstorm density current abstract this paper describes the characteristics and evolving nature of a vigorous thunderstorm density current very early in the morning of 9 may 1981 in oklahoma because the ambient lower atmosphere was stratified interesting interactions between the outflow current and the ambient environment resulted the leading portion of the current was modulated by at least three gravity wavelike perturbations of horizontal spacing 12 km which initially coexisted with it however as the current evolved it initiated an undular borelike disturbance which propagated ahead into the stable boundary layer carrying cold outflow air in large amplitude rolls eventually the wave family left the decelerating outflow air in its wake this borelike disturbance resembles the australian morning glory phenomenon and appears to represent an early stage in the development of a solitary wave family the observations resemble other reported morning glories and solitary waves as well their laboratory and numerically simulated

sediment resuspension and mixing by resonantly generated internal solitary waves the observation of internal solitary waves isws propagating upstream along a strongly stratified bottom layer on the california shelf is reported an increased concentration of particulates in the water column accompanies the passage of these isw packets the estimated local richardson number in the bottom vicinity is around 1 4 and a vertical coefficient of eddy diffusivity of order 1022 m2 s21 is associated with the upstream propagating leading isw the leading isw gave rise to reversed flow in an 8 m layer above the bottom it is argued that the upstream propagating isws were generated by resonant flow over bottom topography internal waves generated in this way seem to be frequent in the record of a month long experiment model results suggest that the isws can carry up to 73 of such generated long wave energy the ocean conditions at the site are similar to those of other coastal sites which suggests that the phenomenon described here may be common

long term observations of tropical instability waves abstract reynolds sea surface temperature sst data showing tropical instability waves tiws in the tropical pacific are analyzed along with current measurements from the tropical atmosphere ocean tao buoy array and wind speeds from the european remote sensing satellite ers 1 and 2 scatterometers tiws are visible as undulations in the sst cold fronts that delineate the northern and southern boundaries of the cold tongue in the equatorial pacific the sst pattern results from advection of the sst front by instabilities in the near surface equatorial currents although the waves are seen on both sides of the pacific cold tongue and north of the equator in the atlantic they are most intense and thereby most observable in the north equatorial pacific the combination of data used in this analysis provides information about these waves the factors controlling them and their coupling to the atmosphere on annual and interannual timescales on annual timescales the tiws generally establish a strong

mode 2 waves on the continental shelf ephemeral components of the nonlinear internal wavefield 1 shoreward propagating mode 2 nonlinear waves appear sporadically in mooring records obtained off the coast of new jersey in the summer of 2006 individual mode 2 packets were tracked between two moorings separated by 1 km however packets could not be tracked between moorings separated by greater distances from one another 10 km the inability to track individual packets large distances through the mooring array combined with detailed observations from a ship suggest that these waves are short lived the evolution of the ship tracked wave group was recorded using acoustic backscatter acoustic doppler current profilers and turbulence profiling the leading mode 2 wave quickly changed form and developed a tail of short small amplitude mode 1 waves the wavelength of the mode 1 oscillations agreed with that expected for a copropagating tail on the basis of linear theory turbulent dissipation in the mixed layer and radiation of the short mode 1 waves contributed to rapid energy loss in the leading mode 2 wave consistent with the observed decay rate and short life span of only a few hours the energy in the leading mode 2 wave was 10 100 times smaller than the energy of mode 1 nonlinear internal waves observed during the experiment however the magnitudes of wave localized turbulent dissipation were similar

horizontal variability of high frequency nonlinear internal waves in massachusetts bay detected by an array of seafloor pressure sensors a two dimensional array of fourteen seafloor pressure sensors was deployed to measure properties of tidally generated nonlinear high frequency internal waves over a 14 km by 12 km area west of stellwagen bank in massachusetts bay during summer 2009 thirteen high frequency internal wave packets propagated through the region over 6 5 days one packet every semidiurnal cycle propagation speed and direction of wave packets were determined by triangulation using arrival times and distances between triads of sensor locations wavefront curvature ranged from straight to radially spreading with wave speeds generally faster to the south waves propagated to the southwest rotating to more westward with shoreward propagation linear theory predicts a relationship between kinetic energy and bottom pressure variance of internal waves that is sensitive to sheared background currents water depth and stratification by comparison to seafloor acoustic doppler current profiler measurements observations nonetheless show a strong relationship between kinetic energy and bottom pressure variance this is presumably due to phase locking of the wave packets to the internal tide that dominates background currents and to horizontally uniform and relatively constant stratification throughout the study this relationship was used to qualitatively describe variations in kinetic energy of the high frequency wave packets in general high frequency internal wave kinetic energy was greater near the southern extent of wavefronts and greatly decreased upon propagating shoreward of the 40 m isobath this article is protected by copyright all rights reserved

sediment resuspension mechanisms associated with internal waves in coastal waters 1 large amplitude vertically trapped internal waves can induce sizable velocities and trigger hydrodynamic instabilities in the bottom boundary layer thereby contributing to the resuspension of sediments and the maintenance of sediment concentration in the water column we discuss numerical simulations of several different situations in which the boundary layer in the wave footprint undergoes hydrodynamic instability with a resultant increase in the incidence of spatiotemporal structures that could facilitate sediment resuspension for the case of internal solitary waves we provide bounds in parameter space separating regions in which internal waves can be expected to efficiently resuspend sediment from those in which the boundary layer in the wave footprint is both laminar and stable a notable finding is that the onset of instability is a strong function of the background current the lagrangian transport of passive particles due to the instability is explored and some quantitative measures of the efficiency of the particle transport process are provided we subsequently discuss the evolution of the power spectra of the bottom shear stress with time and find that while the general characteristics of the instability are robust lowering either the reynolds number or the strength of the background current leads to an increase in the typical length scales associated with the mature instability finally we discuss instabilities during the internal wave generation process and alternative instability mechanisms when the bottom is not flat

topographic form drag on tides and low frequency flow observations of nonlinear lee waves over a tall submarine ridge near palau abstracttowed shipboard and moored observations show internal gravity waves over a tall supercritical submarine ridge that reaches to 1000 m below the ocean surface in the tropical western pacific

bottom pressure observations of deep sea internal hydrostatic and non hydrostatic motions in the ocean sloping bottom topography is important for the generation and dissipation of internal waves here the transition of such waves to turbulence is demonstrated using an accurate bottom pressure sensor that was moored with an acoustic doppler current profiler and high resolution thermistor string on the sloping side of the ocean guyot great meteor seamount water depth 549 m the site is dominated by the passage of strong frontal bores moving upslope once or twice every tidal period with a trail of high frequency internal waves the bore amplitude and precise timing of bore passage vary every tide a bore induces mainly non hydrostatic pressure while the trailing waves induce mainly internal hydrostatic pressure these separate internal wave pressure terms are independently estimated using current and temperature data respectively in the bottom pressure time series the passage of a bore is barely visible but the trailing high frequency internal waves are a bore is obscured by higher frequency pressure variations up to similar to 4 x 10 3 cpd approximate to 80n cpd cycles per day n the large scale buoyancy frequency these motions dominate the turbulent state of internal tides above a sloping bottom in contrast with previous bottom pressure observations in other areas infra gravity surface waves contribute little to these pressure variations in the same frequency range here such waves do not incur observed pressure this is verified in a consistency test for large reynolds number turbulence using high resolution temperature data the high frequency quasi turbulent internal motions are visible in detailed temperature and acoustic echo images revealing a nearly permanently wave turbulent tide going up and down the bottom slope over the entire observational period the spectral slope and variance of bottom pressure are equivalent to internal hydrostatic pressure due to internal waves in the lower 100 m above the bottom by non hydrostatic pressure due to high frequency internal waves and large scale overturning the observations suggest a transition between large scale internal waves small scale internal tidal waves residing on thin similar to 1 m stratified layers and turbulence

internal solitary waves control offshore extension of mud depocenters on the nw iberian shelf abstract hydrodynamic conditions and near bottom sediment transport on the nw iberian shelf associated with a 5 day storm in september 2014 were monitored during the post storm relaxation period active bottom sediment transport by internal solitary waves isws on a mid shelf mud depocenter located in between 110 and 130 m water depth wd was observed to explore the potential of internal waves in sediment transport and its link to development of mid shelf mud depocenters we apply a weakly nonlinear model based on the variable coefficient gardner equation to estimate the flow fields and bottom shear stress induced by shoaling of mode 1 long internal solitary waves shoreward propagation of the isws in three representative periods pre intra and post storm is simulated respectively transformation of the internal wave from a single sech2 shape characterized by negative polarity and small amplitude to a dispersive trailing wave packet with varying amplitude and inverse polarity are satisfactorily reproduced model results indicate enhancement of the maximum orbital velocity of the isws during and after the storm on the outer shelf 130 220 m wd including the seaward margin of the mud depocenter bottom shear stress consequently becomes strong enough 0 1 pa to winnow unconsolidated sediment and constrains the offshore extension of the depocenter the enhanced bottom orbital velocity and the asymmetry in the excursion direction of mode 1 long isws in the post storm period prove to be efficient in transporting fine grained sediment across shelf our results suggest that mid shelf mud depocenters are not necessarily areas under permanently calm conditions where fine grained sediment can settle straightforwardly they could also result from convergent sediment transport from both onshore and offshore directions and sediment may go through numerous cycles of resuspension transport deposition before its ultimate lasting burial

measurements of form and frictional drags over a rough topographic bank pressuredifferencesacrosstopographygenerateaform dragthatopposestheflow in the watercolumn and viscous and pressureforcesacting on roughnesselements of the topographic surface generatea frictionaldrag on the bottom form drag and bottom roughness lengths were estimated over the east flower garden bank efgb in the gulf of mexico by combining an array of bottom pressure measurements and profiles of velocity and turbulent kinetic dissipation rates the efgb is a coral bank about 6km wide and 10km long located at the shelf edge that rises from 100 m water depth to about 18m below the sea surface the average frictional drag coefficient over the entire bank was estimated as 0 006 using roughness lengths that ranged from 0 001cm for relatively smooth portions of the bank to 1 10cm for very rough portions over the corals the measured form drag over the bank showed multiple time scale variability diurnal tides and lowfrequency motions with periods ranging from 4 to 17 days generated form drags of about 2000nm 21 with average drag coefficients ranging between 0 03 and 0 22 which are a factor of 5 35 times larger than the average frictional drag coefficient both linear wave and quadratic drag laws have similarities with the observed form drag the form dragis an important flow retardation mechanismevenin the presence of the large frictional drag associated with coral reefs and requires parameterization

the formation of internal bores in the atmosphere a laboratory model summary recently several atmospheric observations have been interpreted as internal undular bores or internal solitary waves evolving from internal bores that propagate along low level temperature inversions it has been speculated that such disturbances are generated by some type of gravity current such as cold fronts sea breeze fronts and thunderstorm outflows interacting with an existing temperature inversion in this paper we describe a systematic laboratory study in a water channel of internal bores and their generation by the movement of gravity currents through a two layer model of the atmosphere we compare the results of our laboratory experiments with previous theories and numerical simulations and with several detailed atmospheric observations of internal bores at different stages of development

the problem of heat flow density determination from inaccurate data abstract we present an inverse method for processing rough data from oil wells in order to evaluate the heat flow density assuming that the evaluations of temperatures and thermal resistivities present gaussian uncertainties we give formulas for computing the optimal value of the heat flow density and its standard deviation a synthetic example using likely assumptions on various uncertainties leads to the prediction that a standard deviation of about 10 mw m 2 could apply to heat flow estimates from oil well data for typical situations

heat flow in the westernmost part of the alpine mediterranean system the rif morocco abstract heat flow density hfd and thermal gradient calculated on the basis of oil well data in the rif vary from 50 to 90 mw m 2 and from 20 to 50 c km respectively short term variations in the west can be attributed to water circulation and lateral heat conductivities contrast along the pre rif thrusting front and at the limits between the main structural units the gharb basin the south rifian ridges and the pre rif nappe high hfd and thermal gradient values are determined in the southwest of the study area this zone extends the central moroccan massif which is well known by its high thermal manifestations the external rif shows a tendency of increasing hfd toward northeastern morocco and the alboran sea in agreement with the geophysical observations electrical conductive structures great negative bouguer anomaly shear velocity attenuation high upper mantle p velocity the thermal structure of the external rif would be a consequence of the presence at subcrustal depths of hot and low density asthenospheric material overlying a high velocity lithospheric body beneath the rif betic belt

the response of a strongly stratified fjord to energetic tidal forcing abstract the response of upper loch linnhe a strongly stratified scottish fjord to energetic tidal forcing is studied by new analysis of two observational data sets using a ship mounted acoustic doppler current profiler adcp and an undulating conductivity temperature depth ctd we are able to repeatedly sample over a tidal cycle at sufficiently high spatial and temporal resolutions to clearly define the tidal variability in the vertical and horizontal away from the near sill region horizontal velocities are generally orientated along the longitudinal axis of the fjord analysis of the along fjord velocities shows that at the m2 frequency there is a strong 1st mode internal tide with maximum horizontal velocity amplitudes of 23 4 cm s 1 the observed vertical structure of the complex amplitudes of the horizontal velocities are in close agreement with normal mode theory along fjord variations of the fitted amplitude and phase lags from further analysis of the two independent data sets show that the 1st mode internal tide is behaving as a standing wave within the near sill region the circulation is complicated by the formation of a horizontal gyre and a large perturbation in the density field on the flood tide these features are a response to the flood tide currents advecting denser water into the fjord in the form of a strong jet due to the narrow entrance sill being off centre to the axis of the fjord the strong flood tide jet gives rise to eddy formation as the incoming flood tide water is denser than the resident surface water of the fjord the tidal jet sinks and advects the resident water landwards giving rise to the observed density perturbations

internal wave directional spectra using an acoustic doppler current profiler an acoustic doppler current profiler was deployed through land fast ice near resolute northwest territories it recorded a distinct train of high frequency periods 30 0 min horizontal flow without a corresponding coherent vertical velocity component attributed to a density driven along isopycnal flow created by salt rejection emanating from a broad shelf to the northeast

observations of highly nonlinear internal solitons over the continental shelf surface disturbances caused by strong near surface internal waves are widely seen in coastal regions as bands of slick and rough water propagating shoreward these surface slicks are typically manifestations of optical and radar backscatter properties above internal solitons and have strong surface current pulses associated with them during a recent experiment studying coastal internal waves extremely strong solitary internal wave packets were observed over a three week period on a very shallow and strongly stratified pycnocline off northern oregon during periods of strongest tidal forcing solitons were consistently observed on the leading edge of a semidiurnal internal tide bore with pycnocline displacements up to 25m downward from a 7m initial depth in the first few solitons the extreme nonlinearity of these internal waves is believed to be unique in ocean observations this note characterizes these highly nonlinear solitary internal waves siw and presents a second order kdv model which reproduces the form of the displacements and the small change in soliton width with amplitude predicted by this model

the energetics and tidally induced reverse renewal in a two silled fjord a laterally integrated two dimensional numerical model is used to examine the influence of the m2 tide on the circulation in the saguenay fjord a two silled fjord with a large inner and a small outer basin located on the north shore of the st lawrence estuary it is found that the m2 tide is more vigorous in the outer than in the inner basin and that more vertical mixing occurs in the outer basin therefore the density at depth in the outer basin decreases faster than it does in the inner basin and the resulting horizontal pressure gradient causes a bottom flow of water from the inner to the outer basin across the inner sill this reverse renewal is evident in both the available observations and the simulation according to the model much of the m2 energy withdrawn from the surface tide is fed into the internal tide significant tidal energy is also advected by the mean flow velocity approximately 25 of the net energy flux into the fjord is dissipated within 2 km of the outer sill because of the baroclinic pressure i e the total pressure but with the influence of the surface displacement removed the subtidal circulation is associated with very large energy fluxes within the fjord these fluxes are much larger than the net rate at which tidal energy enters the fjord and they are greater than the subtidal advective energy flux they represent a large redistribution of energy within the fjord and their horizontal divergence along the fjord is almost in balance with the time rate of change of potential energy when a flux richardson number is calculated for the inner basin below sill depth a value of 0 075 is obtained which is close to values found for other fjords

high resolution heat flow density in the lower congo basin 1 heat flow density hfd has been derived in the lower congo basin from 293 conventional probe measurements 424 oil exploration data and about 1 000 000 bottom simulating reflector bsr values each set of data provides independent estimates of temperature gradients associated with specific uncertainties and geographic distributions but a statistical comparison in overlapping domains shows a relatively good consistency in situ conductivity has been measured in conventional surveys and estimated from rock composition and porosity in oil exploration boreholes in the deep offshore measurements and estimates are consistently low and increase significantly toward the shelf domain thermal conductivity does not change significantly in the interval between the water bottom and the bsr and can be estimated from the surface measurements to provide an inference of hfd the combined sets of hfd in the lower congo basin cover the overall domain of the continental margin and a part of the oceanic domain high resolution imaging of the bsr by three dimensional 3 d seismic studies provides in addition good quality nominal resolution of 500 m in the deep offshore at short length scales on the order of kilometers large variations of hfd from 30 to 140 mwm 2 exist above salt diapirs and canyons related to heat refraction on the other hand no small scale effect related to fluid flow has been detected although active venting is known at larger length scale hfd in the deep offshore is different on both sides of the congo submarine channel 54 8 mwm 2 to the north and 48 12 mwm 2 to the south which are also characterized by different basin tectonic styles at the margin scale hfd is significantly different in the oceanic domain 42 3 mwm 2 the deep continental offshore 52 10 mwm 2 and the continental shelf 65 15 mwm 2 a progressive reduction of the radiogenic heat contribution in the extended continental crust is the more likely the cause of these differences mantle heat flow below the continental margin is consequently high compared to that expected 15 mwm 2 for old shields such as congo

left hand rule for synoptic eddy feedback on low frequency flow 1 in this study scale interaction between synoptic eddies and low frequency flow is investigated the synoptic eddy feedback is a key process in sustaining the low frequency flow we show clear evidence using ncep reanalysis data that there is a general underlying rule the left hand rule governing the synoptic eddy feedback onto low frequency flow this rule states that eddy vorticity fluxes are directed preferentially about 90 degrees toward their left hand side so that they converge into cyclonic flow and diverge from anticyclonic flow therefore the eddy vorticity flux plays a positive role in reinforcing low frequency flow citation kug j s and f f jin 2009 left hand rule for synoptic eddy feedback on low frequency flow geophys res lett 36 l05709 doi 10 1029 2008gl036435

geothermics of the essaouira basin in morocco the mean values of geothermal gradient and heat flow density have been estimated from bottom hole temperatures taken from 75 petroleum exploration wells in the essaouira basin in morocco and are fo

enhanced turbulence due to the superposition of internal gravity waves and a coastal upwelling jet to vertical aspect ratios of 10 2 to 10 3 median value 300 these patches are clearly defined by regions of low richardson number and occur where and when the linear superposition of the three dominant shear constituents near inertial m2 and thermal wind interferes constructively this is most pronounced at the base of the coastal jet where the thermal wind shear is largest while the effect of the turbulence stress divergence on the jet is small compared to geostrophy 1 it is significant in the second order force balance governing secondary circulation the timescale associated with the decay of the thermal wind shear via turbulence stress is o 10 days we confirm that the vertical salt flux due to mixing is comparable to the net ekman transport of salt onto the shelf within the bottom boundary layer because numerical models of coastal circulation lack turbulence in midwater column any vertical transport of scalars including salt and heat must be achieved inshore of the 40 m isobath this is inconsistent with the observations presented in this study in which significant vertical turbulent salt transport is found to exist across the entire shelf

modelling the variability of heat flow due to the random thermal conductivity of the crust summary analytical solutions for the mean heat flow and its error bounds have been obtained by solving the steady state heat conduction equation following a stochastic analytical approach incorporating gaussian uncertainties in the thermal conductivity this study on the uncertainty analysis to quantify the variability in the heat flow along with its associated error statistics has been applied to the latur earthquake region of the indian shield results obtained show that the mean heat flow and its error bounds are highly dependent on the random components of the thermal conductivity such as its coefficient of variability and its correlation length scale hence the study can be used to quantify the error statistics in the heat flow field for any given region

stochastic modeling of the thermal structure to decipher the lithospheric thickness application to dharwar craton a wide range of speculation regarding lithospheric thermal thickness in a region calls for quantifying the uncertainties associated with model parameters in this paper we present an attempt to decipher it by solving the differential equations governing the heat transfer through the lithosphere adequately quantifying the temperature field is very important since it is highly dependent on the controlling thermal parameters thermal conductivity is modeled as a random parameter with a known mean value and correlation structure we compute the temperatures in the crust and lithospheric mantle along with their error bounds using an analytical solution to the steady state heat equation and the adomian method of decomposition we apply these solutions in the archean dharwar craton which is divided into western dharwar craton wdc and eastern dharwar craton edc we obtain a moho temperature estimate of 304 58 c in wdc whilst in edc it is 375 74 c for a 20 coefficient of variability in thermal conductivity the range of lithospheric thickness obtained for wdc is 150 280 km and 110 160 km for the edc these values are in agreement with other geophysical and geological findings in the region the thermal lithosphere obtained from this study is based on the mantle solidus and the surface wave seismological studies considering radial anisotropy reveal that the lithosphere is characterized by higher shear wave velocities and decrease at the lithosphere asthenosphere boundary average shear velocity model for two different cratonic blocks edc and wdc is used to show the lab thickness for the eastern and western dharwar craton the two independent studies show a correlation in the lithospheric thickness

near bed solibores over the continental slope in the faeroe shetland channel abstract on two occasions within a 12 day measurement period in the faeroe shetland channel strongly nonlinear wave trains were observed at the sea bed propagating up the continental slope in water depths 450 m the events were separated by a period of 4 days and whilst resembling in appearance a density current running up a slope are termed solibores displaying the properties of both turbulent internal bores and nonlinear internal solitary waves isw each solibore displays a steep leading edge followed by a train of nonlinear waves with amplitudes of o 10 m and periods of 5 20 min wave induced particle velocities are consistent with isw whilst a zone of strong horizontal convergence at the leading edge of the solibores causes the formation of a rotor with flow in the opposite sense to a forward overturning surface wave in both cases upward vertical velocities 10 cm s 1 are immediately followed by a return downward flow of equal magnitude a ctd and microstructure transect conducted during the passage of the first solibore illustrates its behaviour as an up slope intrusion of cold dense water with concurrent rates of turbulent dissipation e of o 10 7 w kg 1 and resulting in short term maximum vertical diffusivities kz of o 10 1 m2 s 1 in the long term however kz 140 days which again indicate intermittency in periods of enhanced sediment flux the solibores are consistent with the results of numerical and laboratory experiments on hydraulic jumps resulting from shoaling isw the influence of the slope is proposed to be the reason for their slightly different forms and effects on sediment transport thus the first solibore propagating directly up the slope is proposed to result from an overturning hydraulic jump caused by kinematic instabilities and which subsequently forms a horizontal density intrusion the second solibore represents a dispersive wave train due its oblique direction of propagation which reduces the effective bottom slope allowing dispersion to balance nonlinear effects and prohibiting overturning

energy fluxes due to the surface and internal tides in knight inlet british columbia abstract a laterally integrated two dimensional nonlinear numerical model is used to examine the flux of m2 tidal energy in knight inlet the simulated flux of tidal energy into the inlet is somewhat smaller than that estimated using the change in phase of the m2 tidal height along the inlet a method that does not account for the effect of the internal tide on the surface elevation the simulated energy flux into the inlet is close to the energy flux of the internal tide away from the sill determined from observations using an acoustic doppler current profiler adcp the net flux due to the internal tide is significantly less than 1 2 of the rate at which energy is removed from the surface tide earlier linear models of the internal tide produced energy fluxes that agreed with those estimated from the phase change of the tidal height but were larger than the fluxes that could be found in the observations the reason for this discrepancy is not that these simple models neglected nonlinear effects b

inversion of temperature measurements in lake sediment summary the problem of determining heat flow density hfd from temperature data obtained in lake sediments is formulated using an iterated linear inverse theory with numerical results presented in the forms of probability density function and sensitivity coefficient the galerkin finite element method and a weighted finite difference scheme are used in the spatial and temporal domains respectively to allow for layered structure in the sediments and for transient disturbances arising from lake bottom temperature variation btv with time when a record of btv is lacking inversion of temperature data from a single probe penetration gives an unreliable estimate of hfd this difficulty is alleviated by using multiple probe measurements which if taken at intervals of several months prove adequate for a reliable estimation of the hfd and the most recent part of btv thermal properties of the sediments however must be accurately known a priori because a simultaneous estimation of hfd btv and the thermal properties remains unattainable in a practical case hfd is usually resolved to the same extent that thermal conductivity is known a priori

a model for temperature variations in sedimentary basins due to random radiogenic heat sources summary the thermal structure of a sedimentary basin is controlled by its thermal conductivity its boundary conditions water flow rate of sedimentation and erosion and radiogenic heat sources the radiogenic heat production in the sediments is known to vary over several orders of magnitude with the lowest values in evaporites and carbonates and the highest values in black shales due to a paucity of information available on the existing heat sources this parameter can be represented with a known mean value and a gaussian correlation structure rather than a deterministic function in this paper the 1 d steady state thermal structure in a sedimentary basin has been modelled in a stochastic framework with a random radiogenic heat source and analytical expressions for the first two moments of the temperature field have been obtained a synthetic example has been examined to quantify the error bounds on the temperature field due to uncertainties in the radiogenic heat sources

measurement of tidal form drag using seafloor pressure sensors abstractas currents flow over rough topography the pressure difference between the up and downstream sides results in form drag a force that opposes the flow measuring form drag is valuable because it can be used to estimate the loss of energy from currents as they interact with topography an array of bottom pressure sensors was used to measure the tidal form drag on a sloping ridge in 200 m of water that forms a 1 km headland at the surface in puget sound washington the form drag per unit length of the ridge reached 1 104 n m 1 during peak flood tides the tidally averaged power removed from the tidal currents by form drag was 0 2 w m 2 which is 30 times larger than power losses to friction form drag is best parameterized by a linear wave drag law as opposed to a bluff body drag law because the flow is stratified and both internal waves and eddies are generated on the sloping topography maximum turbulent kinetic energy dissipation rates of 5 10 5 w kg 1 were measured with a microstructure pr

structure and generation of turbulence at interfaces strained by internal solitary waves propagating shoreward over the continental shelf abstract detailed observations of the structure within internal solitary waves propagating shoreward over oregon s continental shelf reveal the evolving nature of interfaces as they become unstable and break creating turbulent flow a persistent feature is high acoustic backscatter beginning in the vicinity of the wave trough and continuing through its trailing edge and wake this is demonstrated to be due to enhanced density microstructure increased small scale strain ahead of the wave trough compresses select density interfaces thereby locally increasing stratification this is followed by a sequence of overturning high density microstructure and turbulence at the interface which is coincident with the high acoustic backscatter the richardson number estimated from observations is larger than 1 4 indicating that the interface is stable however density profiles reveal these preturbulent interfaces to be o 10 cm thick much thinner than can be resolved with shipboard velocity measurements by as

surface heat flow and the mantle contribution on the margins of australia 1 we present thermal data from 473 oil exploration wells in australia and new zealand approximately 2300 bottom hole temperatures are corrected to form a homogeneous set along with 86 temperatures from reservoir tests thermal conductivity profiles are estimated from a set of geophysical well logs using a recently developed neural network approach retaining wells in which temperature and thermal conductivity data overlap over an interval greater than 1000 m we estimate 10 heat flow values in the taranaki basin of new zealand and 270 values in the northwestern western and southern margins and in the intracontinental canning basin of australia the values are in the range 30 80 mw m 2 as a result of several differences in the data and methods our heat flow values are 10 20 mw m 2 lower compared to previously published estimates for the same wells in new zealand for australia our values are consistent with previously measured values and trends in the continental and marine regions on the northwestern and southeastern margins we interpret the variations as reflecting changes in the nature of the underlying basement consistent with onshore data it is inferred that the archean crust is depleted in radiogenic elements compared to proterozoic regions and that recent volcanism affects the eastern paleozoic area after removing from surface heat flow the sediment contributions including a permanent radiogenic heat component and a transient sedimentation effect a simple crustal model suggests that mantle heat flow on the continental margin bordering the pilbara craton is higher than below the craton itself moreover heat flow corrected for the sediment contributions is markedly lower in the petrel intracontinental basin than in the adjacent margin although the crust is thinner below this latter region as both are underlaid by the same basement this observation may indicate that the mantle contribution is also higher below that margin such a higher mantle heat flow on old continental margins is consistent with experiments of fluid convection below an insulating lid and suggests that the thermal regime of the continental lithosphere never returns to its prerift state as usually assumed by several thermomechanical models of evolution of continental margins

a kinematic mechanism for positive feedback between synoptic eddies and nao 1 a kinematic mechanism for the positive feedback between the north atlantic oscillation nao and synoptic eddies are depicted based on observational data analyses using three point rescaled covariance statistics of band pass filtered 2 8 days synoptic eddy fields we examined observed eddy structure changes associated with winter mean nao anomalous flow it is demonstrated that the nao flow anomalies systematically deform the structures of recurring synoptic eddies to generate seasonal mean eddy vorticity flux anomalies predominately directed to the left hand side of the nao flow anomalies these anomalous eddy vorticity fluxes converge into the cyclonic center and diverge from the anticyclonic center of the anomalous nao flow and thus enhance the nao flow

internal wave turbulence pressure above sloping sea bottoms an accurate bottom pressure sensor has been moored at different sites varying from a shallow sea strait via open ocean guyots to a 1900 m deep gulf of mexico all sites show more or less sloping bottom topography focusing on frequencies sigma higher than tidal the pressure records are remarkably similar to within the 95 statistical significance bounds in the internal gravity wave continuum iwc band up to buoyancy frequency n the iwc has a relatively uniform spectral slope log p sigma alpha log sigma alpha 2 1 3 the spectral collapse is confirmed from independent internal hydrostatic pressure estimate which suggests a saturated iwc for sigma n all pressure spectra transit to a bulge that differs in magnitude this bulge is commonly attributed to long surface waves for the present data it is suggested to be due to stratified turbulence internal wave coupling which is typically large over sloping topography the bulge drops off at a more or less common frequency of 2 3 x 10 2 hz which is probably related with typical turbulent overturning scales

solitary waves in the lower atmosphere solitary waves are of intense interest in the physical and mathematical sciences1 these nonlinear waves often seem to have a primary role in the asymptotic description of propagating disturbances in inland lakes and coastal waters2 4 in the thermocline of the open sea5 and in the lower atmosphere6 7 we present here new acoustic sounder observations of complex tropospheric solitary wave disturbances at tennant creek in the arid interior of australia fig 1 a description and interpretation of a new type of visible wave phenomena over northern australia which appear as thin propagating cumulus cloud lines and a discussion of observations at burketown on the gulf of carpentaria of a new class of low altitude propagating solitary wave roll clouds which originate to the south these observations when correlated with observations at tennant creek indicate that solitary wave generating disturbances in the form of internal bores8 9 propagate over large distances

thermal regime and hydrodynamics in tunisia and algeria the thermal regime of algeria and tunisia and its relation to hydrodynamics is studied by means of available geological and geothermal and petroleum data heat flow densities in the area range from 60mwm 2 to 141mwm 2 several paleozoic to tertiary aquifers have been identified together with potential recharge and discharge areas the area is a transition zone between the african and european plates the more tectonically active northern alpine domain does not exhibit an obvious geothermal trend and high heat flow anomalies that occur there may be related to structure rather than hydrodynamics the more stable southern saharan tectonic domain with background heat flow of approximately 80mwm 2 exhibits anomalous zones correlated to the hydrodynamic regime with low values in recharge areas algerian tinrhert and high plateaux and values in discharge areas tunisian jeffara and algerian tademait the hydrodynamic perturbation to the normal heat flow is estimated to be as great as 10 20mwm 2 in recharg

the sulu sea internal soliton experiment abstract we present the results of a comprehensive study of large amplitude internal solitons generated in the sulu sea in the philippines by intense tidal flow over a sharp bathymetric feature surface signatures of these waves have been observed in images from the dmsp landsat and nimbus 7 satellites and the space shuttle sir a synthetic aperture radar a two week experiment was conducted in the sulu sea in may 1980 from r v oceanograher during which a three mooring phased array of current meters and thermistors was implanted near the wave source and at 82 km and 200 km from the source seventeen soliton packets were observed whose properties underwent significant change as they propagated across the sea vertical profiles of density temperature and acoustic backscatter as well as radar and photographic surface signatures were obtained from the ship data from satellites moorings and the ship give unprecedented information on the spatial and temporal characteristics of solitary waves which ha

heat flow density values and paleoclimate determined from stochastic inversion of four temperature depth profiles from the superior province of the canadian shield abstract it has long been recognized that terrestrial heat flow density observations from boreholes may be biased due to non steady surface temperature conditions this calls for paleoclimatic corrections which have conventionally been obtained by solving a forward problem based on the equation of heat conduction and models of the surface temperature history and the thermal properties structure while computationally convenient the forward method fails 1 1 to provide a stringent quantitative representation of all available data with confidence limits 2 2 to extract all available information in an optimum manner 3 3 to provide confidence limits on the parameters of interest a stochastic inverse method which overcomes these shortcomings is described the method treats the surface temperature history the thermal conductivity structure and the background heat flow as unknowns which have been constrained a priori with soft bounds the bounds ensure numerical stability and prevent unrealistic solutions when the a priori hypothesis is safe the technique is applied to geothermal data from four 600 m deep boreholes in the superior province of the canadian shield the examples show how it is possible to constrain simultaneously the recent surface temperature history and the steady state background heat flow from shallow geothermal data and furthermore show how uncertainty about the average ground temperature during the wisconsin glaciation may be taken into account