quasi lagrangian large eddy simulations of cross equatorial flow in the east pacific atmospheric boundary layer using a large eddy simulation les the atmospheric boundary layer abl is numerically modeled along 958w from 88 st o 48n during boreal autumn and compared to observations from the east pacific investigation of climate processes in the coupled ocean atmosphere system epic 2001 since the local abl winds are predominantly southerly in this season a quasi lagrangian forcing is used in which the abl air column is forced as if it were advecting northward with the mean september october 2001 meridional wind across the equatorial cold tongue and the rapidly warming ssts to the north pressure gradients and large scale zonal advective tendencies are prescribed as a function of latitude where possible observations from the epic 2001 experiment are used for forcing and for comparison with model results the abl s modeled vertical structure accords with the conceptual model of wallace et al and agrees well with observations surface stability accounts for the minimum in surface wind over the equatorial cold tongue and the maximum over the warm water to the north stability of the lower abl over the cold tongue allows a jet to accelerate at about 500 m height relatively uncoupled to the frictional surface layer vertical mixing over the warm water to the north distributes this momentum to the surface additional simulations were performed to explore the modeled abl s sensitivity to pressure gradients zonal advection free tropospheric humidity and initial conditions the model abl was robust changing the forcings resulted in little change in the modeled structure the strongest sensitivity was of stratocumulus clouds over the cold tongue to cloud top radiative cooling once formed at the southern edge of the cold tongue modeled stratocumulus clouds demonstrate a remarkable ability to maintain themselves over the cold tongue in the absence of surface fluxes by radiative cooling at their tops the persistence of thin stratocumulus clouds in this lagrangian model suggests that horizontal advection of condensate might be an important process in determining cloudiness over the cold tongue

cessation reactivation of polygonal faulting and effects on fluid flow in the voring basin norwegian margin polygonal faults mainly oriented n50 n110 and n170 are abundant in the upper part of the mud dominated kai formation upper miocene lower pliocene of the voring basin a second less developed tier of polygonal faults oriented n20 n80 and n140 exists at the base of the overlying naust formation upper pliocene present the faults abruptly terminate upward below a thick interval of debris flows we propose a dynamic model in which 1 the development of polygonal faults discontinues temporarily as a result of a change in regional sedimentation leading to inactive polygonal faults 2 rapid emplacement of debris flows in the late pleistocene creates a new interval of polygonal faults in the lower part of the naust formation immediately beneath the debris flow and some faults penetrate into the underlying kai formation 3 some polygonal faults within the kai formation are reactivated and propagated upward into the base of the naust formation the high interconnectivity between faulted layers allows the fluids to reach shallower depths forming well expressed pipes and pockmarks on the sea floor the model of cessation reactivation of polygonal faults constrains the sealing capacity of sedimentary cover over the reservoirs and helps to reconstruct the fluid migration history through the sedimentary column

multiple source euler deconvolution rapid three dimensional 3 d source location methods can be extremely useful in framing a subsurface structural model from gravity or magnetic data however existing implementations of euler deconvolution are limited to a single source in each window this can be a significant limitation in areas of complex structure we have generalized the method to the multiple source case and implemented the 3 d algorithm results from synthetic data and from the gold acres mining district in nevada suggest that the new algorithm can be a useful interpretive tool

sedimentological characteristics heavy metal distribution and magnetic properties in subtidal sediments ria de pontevedra nw spain the rias of nw spain are coastal ecosystems of high biological productivity and great economic importance they are intensively exploited by man for fish and shellfish there are a number of important centres of population and industrial activity along their margins which serve as sources of contamination in this context it is desirable to achieve the best possible understanding of the physico chemical processes that control spatial and temporal variations in the geochemical mineralogical and sedimentological characteristics of near surface sediments in the ria de pontevedra and in particular the distribution and mobility of heavy metal contaminants thus adequate environmental planning can be achieved for this site and understanding gained for comparable contexts core samples were examined from the inner middle and outer parts of the ria grain size distributions reflect the presence of two main populations one dominated by silt and clay derived mainly from terrestrial sources and the other by fine sand to coarse silt which is derived mainly from continental shelf and ria mouth sources mineralogical analysis shows an abundance of terrestrial intensive weathering products near the ria head a dominance of shelf derived sediment towards the mouth and the presence of several diagenetic minerals whose nature varies with location within the ria in the inner ria the near surface sediments are slightly enriched in pb cu and zn from anthropogenic sources these sediments are fine grained and have a high organic content hence they have a higher potential to sorb contaminants than the coarser grained less organic rich sediments of the mid and outer ria the estimated sedimentation rates for the fine grained organic rich sediments from the inner part of the ria are about 1 mm year 1 the dominant authigenic minerals in the inner ria are iron sulphides whereas in the mid and outer ria iron silicates and oxyhydroxides are more important these differences in authigenic iron mineralogy are clearly reflected by the magnetic properties of the sediments

tropical instability wave energetics observations from the tropical instability wave experiment ocean velocity data from an array of subsurface moorings deployed from may 1990 to june 1991 during the tropical instability wave experiment are used to study the energetics of planetary waves in the vicinity of the equator at 1408w such waves observed from august to december 1990 were initiated by barotropic instability arising primarily from the cyclonic shear region of the south equatorial current and equatorial undercurrent just north of the equator subsequently local barotropic production continued to maintain and modulate these tropical instability waves through a combination of cyclonic shear and meridional velocity component divergence just north of the equator the end of the wave season coincided with the propagation past the array of a large intraseasonal kelvin wave

methane related carbonate cements in pockmarks of the north sea abstract some pockmarks on the norwegian continental shelf contain patches of cemented sediment that can provide hardgrounds attractive to a variety of benthonic organisms detailed examination of a sandstone sample from a pockmark in norwegian block 25 7 in the north sea has revealed the presence of mg calcite and aragonite cements some of the latter forming botryoids all cement types are characterized by extremely light carbon isotopic compositions with a mean 13c value of 56 1 pdb which shows that the cements contain carbonate produced by oxidation of biogenic methane oxidation occurred in both the oxic and anoxic diagenetic zones trace amounts of interstitial methane mean 13c 40 8 and higher hydrocarbon gases up to c5 with a c1 cn ratio of 0 855 0 874 in the pockmark sediments indicate that some thermogenic methane may be mixed with the biogenic gas

sea bed pockmarks related to fluid migration from mesozoic bedrock strata in the skagerrak offshore norway abstract in the deepest part of the skagerrak the sea floor morphology and the subsurface geology have been mapped from multibeam echo sounder data seismic data and bedrock cores an area of high pockmark density occurs along the shallowest part of a gentle ridge in the central norwegian trench where a middle jurassic sandstone unit subcrops below 30 40 m of late weichselian sediments in contrast few pockmarks occur at the seabed where lower and upper jurassic shales and clayey siltstones subcrop the concentration of pockmarks above the middle jurassic sandstone unit is thus attributed to seepage of gas or liquids migrating up dip from deeper parts of the sedimentary basin in the skagerrak more than 90 of the observed pockmarks occur above mesozoic sedimentary rocks while less than 10 occur in areas of palaeozoic metasediments or crystalline rocks a linear concentration of pockmarks is observed above a fault that terminates at the base of the quaternary succession and this is therefore attributed to seepage of gas or liquids along the fault plane the density of pockmarks is low in areas with thick successions of quaternary sediments indicating that the pockmarks are not related to seepage of biogenic gas from these deposits pockmarks in the skagerrak are thus caused by seepage of thermogenic gas and or other pore fluids from deeper sources and their distribution may help to improve our understanding of the fluid system and migration regime of this part of the north sea

air sea heat exchange along the northern sea surface temperature front in the eastern tropical pacific abstract the atmospheric response to the oceanic forcing in the eastern pacific along the northern equatorial sea surface temperature sst front is investigated in terms of sensible and latent heat flux during the 6 month period from 28 july 1999 to 27 january 2000 and the 7 month period from 28 june 2000 to 27 january 2001 of particular interest is the atmospheric boundary layer abl response to oceanic tropical instability waves tiws that distort the sst front during may january in normal years in previous studies time series of surface heat fluxes clearly show the influence of tiws but the relationship to spatial patterns of sst and wind speed has been inferred only from sparse in situ data in this study satellite observations are used as a basis for compositing in situ data from moorings to compensate for the lack of a spatially dense mooring array the variability in the position of the sst front caused by westward propagating tiws enables fixed mooring locations to measure the abl response

identification and numerical modelling of hydrocarbon leakage in the lower congo basin implications on the genesis of km wide seafloor mounded structures abstract we present a combined approach of interpretation of 2d seismic reflection data and numerical modelling of hydrocarbon generation and migration across the southern slope of the lower congo basin in order to investigate the factors controlling timing and distribution of hydrocarbon leakage in this area we identified three main families of past and present day leakage features 1 mid upper miocene seismic chimneys concentrated basinwards and ending up on buried pockmarks 2 plio pleistocene chimneys rather clustered to the east of the study area and ending up in seafloor pockmarks and 3 fewer scattered chimneys identified within the miocene sequences ending up in shallow enhanced reflectors flat spots stratigraphic and structural elements seem to control the distribution of these features at least two major events of leakage occurred during the middle late miocene and intermittently during the pliocene present external factors as sediment supply are associated to the miocene leakage event whilst internal structural elements probably triggered the pliocene to present day leakage a major seabed morphological feature represented by a margin paralleled belt of more than 1 km wide mounds was identified above growth faults to the east of the study area data constrained 2d hc generation and migration modelling suggests a genetic link between these structures and vertical migration leakage of thermogenic methane sourced from either currently mature oligo miocene source rocks or secondary cracking and further expulsion from over mature upper cretaceous source rocks hence the mounds are likely to represent a lineation of methane derived carbonate build ups despite the natural limitations of a 2d migration model when combined and calibrated with observations from seismic data it can be used as a valid tool to assess petroleum migration routes in sedimentary basins to the best of our knowledge this is the first integrated approach combining both seismic observations and numerical modelling carried out in the angola basin

contributions to atmospheric methane by natural seepages on the uk continental shelf natural gas seepages occur on the united kingdom s continental shelf and although published reports suggest that they are very rare the petroleum industry has identified but not publicly reported many more there is also very little data on the flux of gas from seabed seepages and even less on the contribution of seepages to atmospheric concentrations of gases such as methane potential gas source rocks include quaternary peats as well as petroliferous source rocks such as the carboniferous coal measures and the upper jurassic kimmeridge clays there are also other organic rich sediments which are potential source rocks together these cover a considerable part of the u k continental shelf analogue seismic reflection pinger profiles acquired during the british geological survey s regional mapping programme have been reviewed to identify water column targets including fish and plumes of gas bubbles the ability to distinguish targets is critical to an assessment of the distribution of gas seepages both theoretical predictions of target identity and the habits of shoaling fish have been investigated in order to identify a method of distinction data from seabed seepages and measurements of seepage rates have been used to establish likely ranges of gas flux rates and the sizes of gas bubbles the likelihood that a rising bubble will survive and escape into the atmosphere is determined primarily by bubble size and water depth methane the principal constituent of seepage gas is relatively unreactive and sparingly soluble the studies have enabled a new estimate of the distribution of gas seepages on the u k continental shelf and of the contribution to atmospheric methane levels the results suggest that natural gas seepages are significantly more important as a source of methane than had hitherto been established it is estimated that between 120 000 and 3 5 mtonnes of methane per year come from a continental shelf area of about 600 000 km2 this represents between 2 and 40 of the total united kingdom methane emission it is suggested that similar contributions arise from other continental shelf areas worldwide and that geological sources of atmospheric methane are more significant than is generally acknowledged

hydrocarbon leakage through focused fluid flow systems in continental margins transport of liquid and gaseous hydrocarbons through focused fluid flow systems is a widespread process in continental margins and sedimentary basins which is gaining increased attention in the assessment of geohazards environment conservation and securing fossil energy resources studying the abundance distribution and drivers for this process is crucial for understanding its role in 1 the dynamics of gas hydrate accumulation and destabilization 2 submarine slope stability and related tsunamis 3 the plethora of chemosynthetic benthic ecosystems that develop in deep seep sites and 4 the input of greenhouse gases e g methane into the ocean atmosphere system which may influence the atmospheric carbon budget and earth s paleo and present climate new ocean exploration tools provide ever more data and improve our understanding of these systems however the subject still suffers from a lack of interdisciplinary knowledge dissemination the ongoing international debate about the timing and the processes that control fluid expulsion in sedimentary basins is fuelled by their implications for structural and petroleum geology because fluids expelled at cold seeps originate at depth they represent open windows into the underlying petroleum systems and are valuable indicators for the reservoir systems they may also help in deciphering past and predicting future climate change because worldwide release of large amounts of fluids may have an impact on the chemistry of the ocean and atmosphere

satellite measurements reveal persistent small scale features in ocean winds four year averages of 25 kilometer resolution measurements of near surface wind speed and direction over the global ocean from the quikscat satellite radar scatterometer reveal the existence of surprisingly persistent small scale features in the dynamically and thermodynamically important curl and divergence of the wind stress air sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields as are the influences of islands and coastal mountains ocean currents such as the gulf stream generate distinctive patterns in the curl field these previously unresolved features have important implications for oceanographic and air sea interaction research

atmospheric manifestation of tropical instability wave observed by quikscat and tropical rain measuring mission observations from two new spaceborne microwave instruments in 1999 clearly reveal the atmospheric manifestation of tropical instability waves north of the pacific equatorial cold tongue a unique zonal temporal band pass filter enables the isolation of the propagating signals and the determination of their phase differences the phase differences between the propagation of wind and sea surface temperature sst signals observed from space and the vertical wind profiles measured from a research ship are consistent with the hypothesis that the coupling between wind and sst is caused by buoyancy instability and mixing which reduces the wind shear in the atmospheric boundary layer the coupling causes higher evaporative cooling over the warm phase and infers a negative thermal feedback

mesoscale wind stress sst coupled perturbations in the kuroshio extension abstract mesoscale perturbations of wind stress ms and sea surface temperature sstms in the kuroshio extension ke are analyzed using long term high resolution satellite observations mesoscale wind stress and sst perturbations are first extracted using a locally weighted regression loess method and then analyzed using statistical methods including linear regression singular value decomposition svd and the inverse method the coupling coefficient between mesoscale wind stress magnitude ms and sstms and those between mesoscale wind stress divergence curl and downwind crosswind sst gradients exhibit distinct seasonal variability with large values in winter and small values in summer consistent with previous studies the three leading svd modes for ms and sstms show highly consistent variability in both spatial patterns and temporal expansion coefficients and the temporal expansion coefficients exhibit distinct seasonal and interannual variability these modes are associated with inherent seasonal variability of ms and sstms and interannual variability of the ke jet dynamic state based on the observed coupling relationships between wind stress divergence curl and downwind crosswind sst gradients an empirical model for mesoscale wind stress vector perturbations x y ms f sst is established this model solves x y ms from their divergence and curl estimated from sst gradient data using an inverse method this newly established x y ms f sst model produces reasonably consistent solutions compared to the one established based on the empirical relationship between ms and sstms furthermore this model could separate divergence only and curl only wind stress perturbations to study their respective effects and thus is promising and will contribute to ocean dynamic analyses

avoidable euler errors the use and abuse of euler deconvolution applied to potential fields window based euler deconvolution is commonly applied to magnetic and sometimes to gravity interpretation problems for the deconvolution to be geologically meaningful care must be taken to choose parameters properly the following proposed process design rules are based partly on mathematical analysis and partly on experience 1 the interpretation problem must be expressible in terms of simple structures with integer structural index si and appropriate to the expected geology and geophysical source 2 the field must be sampled adequately with no significant aliasing 3 the grid interval must fit the data and the problem neither meaninglessly overgridded nor so sparsely gridded as to misrepresent relevant detail 4 the required gradient data measured or calculated must be valid with sufficiently low noise adequate representation of necessary wavelengths and no edge related ringing 5 the deconvolution window size must be at least twice the original data spacing line spacing or observed grid spacing and more than half the desired depth of investigation 6 the ubiquitous sprays of spurious solutions must be reduced or eliminated by judicious use of clustering and reliability criteria or else recognized and ignored during interpretation 7 the process should be carried out using cartesian coordinates if the software is a cartesian implementation of the euler deconvolution algorithm most accessible implementations are cartesian if these rules are not adhered to the process is likely to yield grossly misleading results an example from southern africa demonstrates the effects of poor parameter choices

preliminary mapping of void fractions and sound speeds in gassy marine sediments from subbottom profiles bubbles of gas usually methane in marine sediments affect the load bearing properties of the seabed and act as a natural reservoir of greenhouse gas this paper describes a simple method which can be applied to historical and future subbottom profiles to infer bubble void fractions and map the vertical and horizontal distributions of gassy sediments and the associated sound speed perturbations even with single frequency insonification it operates by identifying horizontal features in the geology and interpreting any perceived change of depth in these as a bubble mediated change in sound speed

coupled ocean atmospheric waves on the equatorial front striking 20 30 day sea surface temperature waves observed along the equatorial front in the later half of the year are generally believed to be of an oceanic origin here we report the detection of atmospheric waves that are unambiguously tied to these oceanic waves using new satellite measurements of surface winds a general circulation model simulation reveals that these atmospheric waves have a shallow vertical structure trapped in the planetary boundary layer pbl unlike el nino southern oscillation where changes in deep convection are the cause of anomalous winds vertical wave motion penetrates well above the pbl and is likely to impact the distribution and transport of climatically important gas species such as ozone and dimethyl sulfide

seafloor facies related to upward methane flux within a giant pockmark of the lower congo basin the origin of the cold fluid venting from a giant pockmark within the lower congo basin has been elucidated based upon results of precise mapping submersible dives gravity coring and isotopic analyses realized under a total ifremer cooperative project zaiango and biozaire projects during four dives of the ifremer rov victor 6000 the bottom was filmed hard and soft samples were lifted from the sediment and water samples were collected with a ctd rosette system the detailed dip map shows that the 800 m wide giant pockmark is a composite feature due to the coalescence of multiple 100 m wide depressions that displays a broad range of biological mineralogical and chemical features on the seafloor leading to a seafloor anomaly recorded on the multibeam imagery methane rich fluids migrating through the sedimentary column from a buried palaeochannel clearly react with the sulphate rich circulating sea water to produce hydrogen sulphide and bicarbonate ions this situation leads to a concentrical arrangement of the sedimentary facies with methane related features in the centre and sulphide related features at the periphery this organization is correlated with high levels of methane up to 20 mol l measured in the centre of the giant pockmark responsible for the crystallization of gas hydrates at the bottom in this model the concentrical organization of mineralogical and biological features reflects a geochemical partitioning related to the peripheral progressive mixing of the methane flux

local and remote atmospheric response to tropical instability waves a global view from space a la nina took place in the equatorial pacific in 1999 and strong tropical instability waves tiws developed causing large meanders of a sea surface temperature sst front between the equator and 3 n high resolution satellite measurements are used to describe the variability of sst surface wind velocity column integrated water vapor cloud liquid water and precipitation associated with these strong tiws in 1999 coherent ocean atmosphere patterns emerge in both the pacific and atlantic revealing rich regional characteristics in the far eastern pacific southeasterly trades strengthen weaken over positive negative sst anomalies apparently due to enhanced reduced mixing with high speed winds aloft in the central pacific we find evidence that sst induced sea level pressure changes also contribute substantially to wind fluctuations similar sst wind covariability also exists in the southern hemisphere along 2 s but the wind variability induced by unit sst anomaly is much larger than that north of the equator in the central pacific where the equatorial front is broad the northern sst pattern has a large meridional scale and reaches as far north as 6 n further to the north in the intertropical convergence zone itcz where local sst anomalies are small significant variability is found in clouds and precipitation which is further correlated with surface wind convergence in the atlantic tiw signals in sst are strongly trapped near the equator but they induce significant remote response in the itcz which takes a more southern position than its pacific counterpart and thus more susceptible to tiw influence

geometry and structure associated to gas charged sediments and recent growth faults in the ebro delta spain abstract in the ebro delta ne spain small to large scale synsedimentary deformation has been observed by means of high and low resolution seismics correlated with a network of wells lithoseismic units involved are middle upper pleistocene clays and gravels and holocene deltaic sequence gassy sediments and large river floor pockmarks are identified from seismic profiles along the ebro delta gas charged sediments are identified by zones of acoustic turbidity and other acoustic anomalies on seismic profiles most of the gas is believed to be biogenic in origin resulting from the decay of organic matter contained within rapidly developing shelf margin deltas a group of large symmetric river floor pockmarks also occurs along the inner delta plain both on the river floor surface and buried in the sediment column listric fault geometry is a typical scope shaped plane with a steep upper surface 40 60 that passes downward into a horizontal shear plane the shear plane appears seismically as chaotic and convoluted high amplitude reflectors and is correlated with well data showing layers that include gravel sand and clays associated structural features include reverse drag of reflectors antithetic faults and fluid escapes methane water the growth faulting along the ebro delta includes a break away and thin near surface layer created by overstepping of a sandy holocene delta slope the over steeping lies down dip from growth faults along the shelf break the overall growth faults province appears to represent a deeper seated general movement of the delta mass involving differential loading overpressure of fluids diapiric movements and extensional tectonics that cause listric faults and associated structures at different scales the recent growth faults are regularly spaced with the distance between successive faults controlled by the depth to the detachment layer three main fault systems have been identified a first or primary system spaced 5 2 10 5 km above a detachment layer at 55 95 m deep a second system spaced 3 5 6 km and a third system spaced 1 5 2 5 km above a detachment layer at 25 30 m the slope angle calculated by empirical equations ranges between 0 5 and 1 0 for the three systems

an empirical model for surface wind stress response to sst forcing induced by tropical instability waves tiws in the eastern equatorial pacific abstract high resolution space based observations reveal significant two way air sea interactions associated with tropical instability waves tiws their roles in budgets of heat salt momentum and biogeochemical fields in the tropical oceans have been recently demonstrated however dynamical model based simulations of the atmospheric response to tiw induced sea surface temperature ssttiw perturbations remain a great challenge because of the limitation in spatial resolution and realistic representations of the related processes in the atmospheric planetary boundary layer pbl and their interactions with the overlying free troposphere using microwave remote sensing data an empirical model is derived to depict wind stress perturbations induced by tiw related sst forcing in the eastern tropical pacific ocean wind data are based on space time blending of quick scatterometer quikscat direction interval retrieval with thresholded nudging dirth satellite observations and ncep analysis fields sst d

an embedding method for improving interannual variability simulations in a hybrid coupled model of the tropical pacific ocean atmosphere system an embedding approach is developed and tested to improve el nino southern oscillation enso simulations in a hybrid coupled model hcm focusing on the ocean thermocline effects on sea surface temperature sst in the eastern equatorial pacific the noaa gfdl modular ocean model mom 3 is coupled to a statistical atmospheric model that estimates wind stress anomalies based on a singular value decomposition svd of the covariance between observed wind stress and sst anomalies analogous to the cane zebiak cz coupled model a separate sst anomaly model is explicitly embedded into the z coordinate ocean general circulation model ogcm the three components exchange predicted anomalies within the coupled system the ogcm provides anomalies of ocean currents in the surface mixed layer and the thermocline depth which are used to calculate sst anomalies from the embedded sst model wind anomalies are then determined according to the statistical atmospheric model which in turn force the ogcm results from uncoupled and coupled runs with and without the embedding are compared with the standard coupling the system exhibits similar behavior to previous hcms including interannual variability with a dominant quasi biennial oscillation and a westward propagation of sst anomalies on the equator these characteristics suggest that the horizontal advection is playing a more important role than the vertical advection in determining sst changes over the eastern equatorial pacific incorporating the embedded sst anomaly model with which the thermocline effects on sst can be enhanced in the eastern equatorial pacific has a significant impact on performance of the hcm the embedded hcm exhibits more realistic sst variability and coupled behavior characterized by 3 4 yr oscillations and a more standing sst pattern along the equator the results support the hypothesis that current physical parameterizations in the ogcm provide insufficient thermal linkage between the thermocline and the sea surface in the eastern equatorial pacific it is demonstrated that the long known deficiency of some ogcms in their depiction of the thermocline and its interactions with sst may contribute to unrealistic coupled variability in hcms of enso the embedding approach not only provides a diagnosis for parameterization deficiencies in current ogcms but pending progress on this difficult problem provides a straightforward means to bypass it and improve coupled model performance

gas venting and late quaternary sedimentation in the persian arabian gulf abstract high resolution 3 5 khz echo sounding profiles and piston cores were used to reconstruct the microtopography and late quaternary depositional history of the persian gulf perversive throughout the seafloor of the gulf is an extensive network of pockmarks formed by seepages of thermogenic gas these gas seeps and bottom water exiting the gulf via the strait of hormuz are the most significant processes controlling present day sedimentation in the region erosion by these seeps has been so intense in the baiban shelf in the strait of hormuz as to create a hoodoo like terrain on the outer shelf the surfical geology of the gulf documents a short lived transgression 29 400 to 22 800 years ago during the wisconsin regression which began 125 000 years ago the wisconsin regressive maxima when sea level dropped to 120 130 m about 21 000 20 000 years ago and the climate was dry and eolian and paralic sedimentation characterized the gulf the holocene transgression 18 000 to 12 000 years ago when the climate was more humid than during the climax of the wisconsin regression a dry phase 12 000 to 9000 years ago when the persian gulf was a site of eolian and carbonate deposition and the present sediment cycle during the last 9000 years under a more humid regime it was during the present cycle that southeast trending marl lobes were deposited off iran arabia acquired its hyper arid climate about 3000 years ago and the gulf attained its present configuration about 1000 years ago as a result of the construction of the tigris euphrates delta at its head and tectonism and aggradation along its arabian and iranian flanks

improving sst anomaly simulations in a layer ocean model with an embedded entrainment temperature submodel abstract in this study an improved sea surface temperature sst anomaly ssta solution for the tropical pacific is presented by explicitly embedding into a layer ocean general circulation model ogcm a separate ssta submodel with an empirical parameterization for the temperature of subsurface water entrained into the ocean mixed layer te instead of using subsurface temperature directly from the ogcm te anomalies for the embedded ssta submodel are calculated from a historical data based empirical procedure in terms of sea level sl anomalies simulated from the ogcm an inverse modeling approach is first adopted to estimate te anomalies from the ssta equation using observed sst and simulated upper ocean currents from the ogcm a relationship between te and sl anomalies is then obtained by utilizing an empirical orthogonal function eof analysis technique the empirical te parameterization optimally leads to a better balanced depiction of the subsurface effect on sst variability by the mean upwelli

gas charged sediments on the inner continental shelf off western india abstract high resolution seismic reflection profiles on the inner continental shelf less than 60 m water depth off india from 10 n to 22 n show 5 35 m of weakly stratified acoustically transparent clays at water depths of 15 50 m the subbottom profiles are characterized by anomalous seismic signatures in the form of acoustic maskings these extend from the underlying late pleistocene unconformity often stretching along the bedding planes and occasionally surfacing on the sea bed these acoustic maskings could be due to shallow hydrocarbon gases mainly methane which might have been derived from biogenic sources or geothermal processes or both

new evidence of perfect overlapping of haploops and pockmarks field is it a coincidence abstract in the shallow waters of the bay of concarneau south brittany france previous studies reported a dense settlement of the species haploops tube dwelling bioengineer amphipod that perfectly overlaps a field of pockmarks a possible mechanistic link may therefore exist between the haploops colonies and the shallow pockmarks to test this hypothesis interferometry sonar and sub bottom profiler chirp data were acquired in two new areas located in the marine estuary of the loire river la lambarde and le croisic the new sites share the same sedimentary and geological characteristics as those found in the bay of concarneau the three sites are similarly located in shallow and muddy environments above a faulted middle eocene formation that is incised by paleo valleys despite different hydrodynamic conditions and estuarine influence in the two new investigated areas the haploops also settle within the pockmarks field limits to better constrain the association pockmarks haploops we compared the sedimentary features seismic signatures and total organic carbon toc content of the sediment active pockmark chimneys displaying highly reworked profiles and slightly higher toc contents suggest a local deeper source of organic matter which might be an important source of nutrient for the haploops in southern brittany the pockmarks haploops spatial overlap is not a simple coincidence and may therefore present a general pattern for identification of settlement preferences of the specie

barometric pressure variations associated with eastern pacific tropical instability waves abstract barometric pressure surface temperature and wind time series in the eastern equatorial pacific are analyzed to determine if oceanic tropical instability wave tiw sea surface temperature variations cause barometric pressure gradients large enough to influence the atmospheric boundary layer during the study period from april 2001 to september 2002 11 tiws propagated westward past 110 w causing a spectral peak at 20 30 days in the sea surface temperature sst meridional difference between 2 n 110 w and 0 110 w likewise the meridional pressure difference also had a spectral peak in the 20 30 day tiw band cross spectral analysis shows that within the tiw band sst induced pressure variations were roughly 0 1 hpa c 1 in magnitude the resulting pressure gradient force is comparable in magnitude to other terms in the meridional momentum balance implications about the role of the boundary layer capping in the adjustment to sst forcing are discussed

observed horizontal temperature advection by tropical instability waves 1 velocity data from moored current meters is combined with satellite sea surface temperature sst to compute oceanic mixed layer temperature advection by tropical instability waves tiws for the years 2002 to 2005 it is found that this process heats the equatorial mixed layer at an annual mean rate of 0 8 c month at 0 n 140 w and 2 8 c month at 0 n 110 w at 0 n 110 w approximately 25 of the heating is contributed by zonal temperature advection a process that has often been assumed to be negligible from a nine month segment of data may 2004 february 2005 the zonal temperature advection at 2 n 140 w has been estimated to be approximately 0 7 c month much larger than the equatorial value for the same time period thus the data supports a recent hypothesis that tropical instability waves contribute a significant mean zonal temperature advection with off equatorial maxima to the equatorial mixed layer heat budget comparisons with numerical model results suggest that current ocean general circulation models can realistically simulate important aspects of tropical eddy mixed layer interactions

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

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

geological controls on focused fluid flow associated with seafloor seeps in the lower congo basin a synthesis of backscatter imagery coupled with a large 3d seismic dataset in the lower congo basin lcb reveals a patchy distribution of features interpreted to be associated with fluid seepage from 300 m to 2500 m water depth with the exception of one region of anomalous backscatter positive relief mounds all inferred seep sites occur in negative relief pockmarks the extensive 3d seismic dataset in the lcb offers a unique opportunity to study the plumbing system that is feeding surface cold seep systems and in general to reconstruct the relationship between tectonics and fluid flow in continental margins the fluid seeps in the lcb are associated with morphologically stratigraphically or tectonically controlled focused fluid flow the integration of the geophysical datasets backscatter imagery coupled to 3d seismic clearly indicates that fluid seeps are not randomly distributed but their seabed organization reflects 1 the location of the underlying structure reservoir or trap where the fluids are coming from 2 the geometry and morphology of the reservoir trap and 3 the discontinuities in the sedimentary column along which fluids have migrated in the lcb seafloor pockmarks are always associated with underlying tectonic structures fault zones salt diapirs polygonal faults or buried sedimentary bodies turbiditic channels erosional surfaces whereas they never occur above sub horizontal parallel stratified fine grained sediments even if triggering processes can not be clearly defined here we propose a model of seafloor fluid seep organization which represents a new tool for identifying the geometry of flow pathways and the underlying buried bodies where the fluids are originating from this qualitative 3d model provides insight into the geohydrologic processes of continental margins

expulsion of shallow gas in the skagerrak evidence from sub bottom profiling seismic hydroacoustical and geochemical data a combined high resolution seismic sub bottom profiling and multi beam echo sounding survey in the skagerrak danish sector of the north sea together with gas analyses at a station along the profile exhibit the expulsion of gas mainly methane and the presence of gas charged sediments at shallow depth the echo soundings yield detailed insight into the distribution and shape of typical sea floor features associated with gas seepage such as pockmarks the pockmarks reach dimensions of 800 m in length 300 m in width and 15 m in depth with the long axis running parallel to the slope of the norwegian trench processing of the multi channel high resolution seismic data and the digitally recorded sub bottom profiler signals indicate an internal compressional velocity of about 1050 m s 1 within the gas charged sediments reaching from the sea floor to a sub bottom depth of about 23 m using the lateral distribution and thickness of the gas charged sediments in conjunction with a mean concentration of gas of 3000 ppb the present amount of trapped gas is estimated to be 6 45 1011 g ch4 the flux of methane through the sea bed into the water column appears to be 7 2 1010 g ch4 per year to explain the small difference in size between the methane pool in near surface sediments and the annual flux through the sea bed a constantly high supply of methane from leaking hydrocarbon reservoirs at greater depths has to be active

metalliferous mining geophysics state of the art in the last decade of the 20th century and the beginning of the new millennium the downturn in mining activity experienced during the 1990s did not preclude significant new developments in various areas of mining geophysics the methodology for acquiring and compiling data has kept pace with the latest technological developments from global positioning system navigation to raster displays and parallel computing wavelet transforms principal component analysis and fractals have begun to find successful applications in both processing and interpretation of geophysical data methods of quantitatively interpreting inverting anomalies in terms of 2 d and 3 d models of causative bodies are becoming common for the first time it is possible to make airborne gravity gradient measurements suitable for use in mineral exploration lower transmitter frequencies for airborne time domain electromagnetic em systems have enabled surveys in areas where conductive cover previously screened basement conductors the use of approximation algorithms has allowed the transformation of either time domai

the influence of sea surface temperature on surface wind in the eastern equatorial pacific seasonal and interannual variability abstract the climate of the eastern pacific exhibits a pronounced equatorial asymmetry boundary layer air originating in the southern hemisphere trades crosses the equator and flows into the intertropical convergence zone itcz whose southern limit is nearly always located at least 4 to the north of the equator the sea surface temperature sst distribution is characterized by a prominent cold tongue centered 1 s a strong frontal zone centered 2 n and a warm eastward current centered near 5 n the surface wind field exhibits a pronounced horizontal divergence as the air flows northward across the oceanic frontal zone these features vary in strength in response to the annual cycle and the el nino southern oscillation phenomenon the northward cross equatorial surface winds the cold tongue and the frontal zone all tend to be strongest during the cold season july through november during the cold season of the coldest years when the cold tongue is most prominent the cross equatorial flow t

seismic evidence for fluid escape from mesozoic cuesta type topography in the skagerrak abstract gas and fluid dynamic processes in the mesozoic to recent strata of the southern slope and center of the norwegian trench skagerrak have been analyzed by high resolution multi channel seismic data collected with a watergun as the seismic source on board of rv heincke in spring 2003 three profiles across the southern slope and the center of the trench and four profiles cover the north eastern termination of the trench the data resolve the quaternary succession and the subcropping mesozoic strata the separating unconformity shows a typical cuesta topography caused by glacial erosion on the slope contourite drifts are present above a water depth of approximately 400 m internal reflections of the quaternary are obscured by acoustic turbidity particularly phase reversed bright reflections occurring in the entire lower jurassic to upper cretaceous succession suggest the presence of fluids therein sea floor pockmarks have been observed on the southern slope and in the center of the trench both slope and trench pockmarks are vertically correlated with the sub crop of fluid charged mesozoic rocks beneath which indicate lateral fluid escape from porous mesozoic rocks fluids that migrate towards a slope pockmark are capable to wash out gas from the quaternary leaving gas free patches behind since no thermogenic gas has ever been measured in core samples from the slope and trench freshwater seepage is a possible explanation in this case the water outflow might represent artesian springs

seismic velocities from the yaquina forearc basin off peru evidence for free gas within the gas hydrate stability zone multichannel seismic mcs data from the yaquina forearc basin off peru reveal a complex distribution of gas and gas hydrate related reflections lateral variations of the reflection pattern at the assumed base of the gas hydrate stability zone in terms of continuity amplitude and signal attenuation underneath are observed as well as the possible occurrence of paleo bottom simulating reflectors bsrs phase reversed reflections above the bottom simulating reflector point to free gas within the gas hydrate stability zone ghsz to constrain the interpretation of the observed reflection pattern we calculated the velocity distribution along the mcs line from high resolution ocean bottom hydrophone recordings with two independent methods heat flux values estimated on the basis of the velocity depth functions increase with decreasing amplitude of the bsr and peak near chemoherms these results suggest a model of the yaquina basin where free gas is trapped under parts of the bsr and within the ghsz particularly under the seafloor and under an erosional unconformity the hypothesis of a paleo bsr that reflects the uplift of the base of the hydrate stability zone caused by the deposition of a particular sediment sequence is supported by the estimated heat flux values

anaerobic oxidation of methane aom in marine sediments from the skagerrak denmark i geochemical and microbiological analyses abstract the organic rich sediments of the skagerrak contain high quantities of shallow gas of mostly biogenic origin that is transported to the sediment surface by diffusion the sulfate methane transition zone smtz where anaerobic oxidation of methane aom and sulfate reduction occur functions as a methane barrier for this upward diffusing methane to investigate the regulation of aom and sulfate reduction rates srr and the controls on the efficiency of methane consumption pore water concentrations and microbial rates of aom sulfate reduction and methanogenesis were determined in three gravity cores collected along the slope of the norwegian trench in the skagerrak srr occurred in two distinct peaks at the sediment surface and the smtz the latter often exceeding the peak aom rates that occurred at the bottom of the smtz highest rates of both aom and srr were observed in a core from a pockmark where advective methane transport occurred generating high methane and sulfate fluxes but even at this site with a shallow smtz the entire flux of methane was oxidized below the sediment surface aom srr and methanogenesis seem to be closely associated and strongly regulated by sulfate concentrations which were in turn regulated by the methane flux rate measurements of srr aom and methanogenesis revealed a tight coupling of these processes bicarbonate based methanogenesis occurred at moderate sulfate concentrations 5 mm above the aom zone but seemed to be inhibited in the depth where aom occurred the unbalanced stoichiometry of aom and srr in the smtz was more pronounced in rate measurements than in methane and sulfate fluxes and seemed more likely be related to enhanced srr in this zone than an underestimation of methane fluxes

modern analogues to middle ordovician sedimentary mounds and washout depressions abstract mounds and depressions containing dense fossil accumulations occur in a bed of middle ordovician age in the upper ottawa valley canada the appearance of these relict seabed features is similar to modern features containing dense accumulations of live species in the north sea it is suggested that the middle ordovician fossil accumulations relied on a similar local upward flux of minerals and nourishment as north sea communities which live in areas where sediments contain light hydrocarbon gases if further petrological and sedimentological studies on the middle ordovician deposits could confirm such a relationship then it would be the first time relict or fossil pockmarks were found in the sedimentary column

control of tropical instability waves in the pacific westward propagating waves with periods of 20 30 days and wavelengths of 1 100km are a prominent feature of sea surface temperatures ssts in the equatorial pacific and atlantic oceans they have been attributed to instabilities due to current shear we compare sst observations from the spaceborne along track scanning radiometer atsr and toga tao moored buoys with ssts from a model of the tropical pacific forced with observed daily windstress data the phases of the strongest tropical instability waves tiws in the model are in closer correspondence with those observed than we would expect if these waves simply developed from infinitesimal disturbances in which case their phases would be arbitrary if we filter out the intraseasonal component of the windstress all phase correspondence is lost we conclude that the phases of these waves are not arbitrary but partially determined by the intraseasonal winds the subsurface evolution of the model suggests a possible control mechanism is through interaction with remotely forced subsurface kelvin and rossby waves this is supported by an experiment which shows how zonal wind bursts in the west pacific can modify the tiw field but other mechanisms such as local feedbacks are also possible

sverdrup and nonlinear dynamics of the pacific equatorial currents abstract the sverdrup circulation in the tropical pacific is constructed from satellite scatterometer winds compared with measured ocean currents and diagnosed in an ocean gcm previous depictions of the sverdrup circulation near the equator have shown only weak vertically integrated flows here it is shown that the actual transports are not weak this discrepancy could be due either to inaccuracies in the wind forcing or to sverdrup dynamics being too simple in this region scatterometer winds show a strip of positive curl along the sst front north of the equator in the eastern pacific that is due to wind speed changes induced by the front including that additional element of curl forcing greatly improves the realism of the sverdrup representation but the magnitudes of the equatorial transport are still too small by a factor of about 2 although the nonlinear advective and friction terms are small in the model momentum balance they are o 1 in the vorticity balance especially because their meridi

elongate depressions on the southern slope of the norwegian trench skagerrak morphology and evolution abstract multibeam echosounder surveys conducted on the southern slope of the norwegian trench between norway and denmark show that elongate depressions interpreted as current modified pockmarks are widespread in water depths of 100 500 m in the holocene recent succession the long axes of the depressions are oriented at an angle of about 15 downslope relative to the depth contours the long axes appear to almost exactly parallel the effective bottom currents in this part of the skagerrak the present current directions were probably established about 4000 years ago following a major shift in the oceanographic circulation pattern the most characteristic feature of the depressions is their large size with maximum depths of 45 m widths of 400 m and lengths of 2 km strong bottom currents continuously transport particles thrown into suspension by the seepage process away from the pockmarks and prevent further deposition continuous seepage of shallow gas at fixed pockmark sites over long time periods combined with generally high sedimentation rates are thought to be responsible for the exceptional size of many depressions the shallow gas probably has a mixed biogenic thermogenic origin however the thermogenic component is considered to be most important for the formation of pockmarks seepage from permeable layers in the jurassic cretaceous bedrock is evidenced by linear rows of depressions above these horizons while pockmarks above sub surface faults indicate gas seeps also from there in shallow water areas the shape and size of pockmarks are locally dependent on their location with respect to giant sand waves which trend sub parallel to the depth contours and are interpreted to be of late weichselian to early holocene age in deeper water areas the pockmarks have been further modified by gravity slides caused by collapse of steep pockmark walls

seafloor gas seeps triggered by a northern california earthquake abstract a series of marine surveys using high resolution seismic reflection and side scan sonar profiling was conducted on the klamath river delta from 1977 to 1985 in november 1980 near the middle of this 8 year time period a major earthquake magnitude 7 occurred in the area the earthquake caused liquefaction of shelf deposits off the klamath river and while mapping the sediment failures we observed an inordinate number of gas vents and acoustic anomalies in the sediment gas charging and water column gas clouds our analyses indicate that a change in gas seepage occurred after the earthquake there was a marked increase in gas abundance immediately after the earthquake a gradual decrease over the next year and stabilization at pre earthquake gas levels within five years or less the acoustic anomalies were observed in pre quaternary rocks as well as in surficial holocene deposits and gas seeps overlay truncated anticlines faults and syncline exposures thus the gas released may have been in part thermogenic in origin a large area 20 km 2 on the delta failed during the earthquake and the abundance of gas seeps and craters in the area suggests that sediment degassing may have been an important process contributing to failure

a seeping sea floor in a ria environment ria de vigo nw spain the occurrence of gas accumulations in the ria de vigo nw spain have been characterized by the authors in previous research pockmarks frequently appear on seismic and sonar records covering ca 45 of the sea floor of the study area which indicates that gas expulsion is not an uncommon phenomena in the coastal ria environment here we report the occurrence of gas seepage for the first time along the coast of nw spain side scan sonar echo sounder and high resolution seismic techniques were used for mapping gas expulsion features some expulsion pockmarks sit over elongated features that represent bottom marks created by anthropogenic activity thus these anthropogenic sites may act as preferential venting zones for gas as well as being potential hazards on a muddy sea bed such as that of the ria where gas accumulates just below the surface of the sea floor

analysis of gravity field to reconstruct the structure of omo basin in sw ethiopia and implications for hydrocarbon potential abstract the omo basin in south western ethiopia at the kenyan boundary is a northern extension of the trans boundary turkana rift it is an early pliocene north south trending depression bounded on either side by normal faulting the omo river flows in the middle of the basin and empties itself at its southern end into lake turkana the structural pattern of the omo basin is determined from 2d and 3d analyses of the gravity field the basin is an asymmetric half graben formed by and localized within the ns nne trending early pliocene normal faults it is built up on the older nw trending structures that were reactivated and affected the recent ns faults automatic depth determination techniques and 3d inversion are used to estimate depth to the basement and determine the sedimentary thickness the results indicate over 4 km thick sediments were deposited over the graben the omo basin lies within the east african rift system and appears to connect the generally nw trending oil rich muglad melut basins of south sudan and the highly prospective and similarly trending anza graben of kenya the omo basin contains thick sequence of sediments and appears to be a promising future site of intensive hydrocarbon exploration

euler deconvolution using differential similarity transformations of gravity or magnetic anomalies euler deconvolution of gravity and magnetic anomalies can be used to estimate the coordinates of a simple point source and the level of a constant background in the deconvolved field by testing a series of structural indices by using differential similarity transformations dsts joint estimations of the source coordinates the structural index and the coefficients of a linear background trend become possible dsts calculated from the derivatives of the interpreted field depend on the position of a chosen central point of similarity with respect to the source position on this basis techniques for euler deconvolution of anomalous fields are presented the theoretical formulations of dst and the deduced sets of equations for euler deconvolution are tested and verified on model and field examples of magnetic anomalies caused by one point and two point sources such as thin and thick dikes semi infinite and finite sills contacts steps faulted beds etc the possibility of an optimum estimation of the structural index can be used to define a second acceptance criterion along with the criterion of relative standard deviations the joint application of these two criteria ensures the selection of reliable results the suggested dst techniques are suitable for initial rapid estimations of the source type depth and plane location they may be applied to either profile or gridded data acquired from onecomponent measurements as well as from gradient or three component measurements additional data on the density or magnetization of the sources are not necessary

the historical development of the magnetic method in exploration the magnetic method perhaps the oldest of geophysical exploration techniques blossomed after the advent of airborne surveys in world war ii with improvements in instrumentation navigation and platform compensation it is now possible to map the entire crustal section at a variety of scales from strongly magnetic basement at regional scale to weakly magnetic sedimentary contacts at local scale methods of data filtering display and interpretation have also advanced especially with the availability of low cost high performance personal computers and color raster graphics the magnetic method is the primary exploration tool in the search for minerals in other arenas the magnetic method has evolved from its sole use for mapping basement structure to include a wide range of new applications such as locating intrasedimentary faults defining subtle lithologic contacts mapping salt domes in weakly magnetic sediments and better defining targets through 3d inversion these new applications have increased the method s utility in all realms of exploration in the search for minerals oil and gas geothermal resources and groundwater and for a variety of other purposes such as natural hazards assessment mapping impact structures and engineering and environmental studies

a modeling study of the impact of tropical instability waves on the heat budget of the eastern equatorial pacific a numerical simulation is used to investigate the mixed layer heat balance of the tropical pacific ocean including the equatorial cold tongue and the region of vortices associated with tropical instability waves tiws the study is motivated by a need to quantify the effects that tiws have on the climatological heat budget of the cold tongue mixed layer there has been some discrepancy between observations indicating very large equatorward heat transport by tiws and models that disagree on the full three dimensional budget validation of the model reveals that the tiw induced circulation patterns are realistic but may have amplitudes about 15 weaker than those in the observations the sst budget within tropical instabilities is first examined in a frame of reference moving with the associated tropical instability vortices tivs zonal advection of temperature anomalies and meridional advection of temperature by current anomalies dominate horizontal advection these effects strongly heat the cold cusps and slightly cool the downwelling areas located at the leading edge of the vortices cooling by vertical mixing is structured at the vortex scale and almost compensates for horizontal advective heating in the cold cusps in contrast to some previous studies tiw induced vertical advection is found to be negligible in the sst budget cooling by this term is only significant below the mixed layer the effect of tiws on the climatological heat budget is then investigated for the region bounded by 2 s 6 n 160 90 w where instabilities are most active tiwinduced horizontal advection leads to a warming of 0 84 c month 1 which is of the same order as the 0 77 c month 1 warming effect of atmospheric fluxes while the mean currents and vertical mixing cool the upper ocean by 0 59 c month 1 and 1 06 c month 1 respectively the cooling effect of tiw induced vertical advection is also negligible in the long term surface layer heat budget and only becomes significant below the mixed layer the results above and in particular the absence of cancellation between horizontal and vertical tiw induced eddy advection are robust in three other sensitivity experiments involving different mixing parameterizations and increased vertical resolution

observations of coupling between surface wind stress and sea surface temperature in the eastern tropical pacific satellite measurements of surface wind stress from the quikscat scatterometer and sea surface temperature sst from the tropical rainfall measuring mission microwave imager are analyzed for the three month period 21 july 20 october 1999 to investigate ocean atmosphere coupling in the eastern tropical pacific oceanic tropical instability waves tiws with periods of 20 40 days and wavelengths of 1000 2000 km perturb the sst fronts that bracket both sides of the equatorial cold tongue which is centered near 1 8s to the east of 1308w these perturbations are characterized by cusp shaped features that propagate systematically westward on both sides of the equator the space time structures of these sst perturbations are reproduced with remarkable detail in the surface wind stress field the wind stress divergence is shown to be linearly related to the downwind component of the sst gradient with a response on the south side of the cold tongue that is about twice that on the north side the wind stress curl is linearly related to the crosswind component of the sst gradient with a response that is approximately half that of the wind stress divergence response to the downwind sst gradient the perturbed sst and wind stress fields propagate synchronously westward with the tiws this close coupling between sst and wind stress supports the wallace et al hypothesis that surface winds vary in response to sst modification of atmospheric boundary layer stability