coastal southerlies and alongshore surges of the west coast of north america evidence of mesoscale topographically trapped response to synoptic forcing abstract one of the most important warm season weather phenomena of the west coast of north america is the temporal transition from northerly to southerly flow within a few hundred kilometers offshore from the coastal mountains such wind shifts are often accompanied by cooler temperatures higher pressure and a change from nearly cloud free to low overcast conditions the more vigorous coastal transitions termed alongshore surges are characterized by an abrupt change in wind direction a sudden increase in wind speed to 15 m s 1 or more a precipitous temperature drop exceeding 10 c and a sharp rise in sea level pressure this paper presents two detailed case studies of topographically trapped coastal southerlies the strong surge event of 15 17 may 1985 and the far weaker case of 3 7 may 1982 it is shown that coastal southerlies and alongshore surges are controlled by the alongshore pressure gradients created by the synoptic scale flow at low levels and within approximately one rossby radius of th

local atmospheric forcing during the coastal ocean dynamics experiment 1 a description of the marine boundary layer and atmospheric conditions over a northern california upwelling region as part of the coastal ocean dynamics experiment code meteorological instruments were deployed on buoys and at coastal stations and instrumented aircraft flights and coastal soundings were made to study the three dimensional structure of the marine boundary layer over the continental shelf off northern california during the 1981 and 1982 upwelling seasons these measurements show that after the atmospheric spring transition the airflow in the marine layer is dominated by the north pacific high and the surface wind field over the shelf is characterized by periods of strong 7 15 m s upwelling favorable alongshelf winds lasting for up to 30 days interrupted by shorter periods of much weaker winds directed either equatorward or poleward these periods of weak or reversed winds typically last several days and are called wind relaxations even though they are primarily associated with coastally trapped perturbations of the marine layer along the central and northern california coast and not with a large scale weakening of the north pacific high the atmospheric boundary layer measurements made in code suggest a simple conceptual model which can explain much of the physiology or structure of the marine layer and associated surface wind field during periods of persistent upwelling favorable winds during these periods which represent the quasi steady state regime during the upwelling season the inversion base of the marine layer drops eastward toward the coast until it intersects the coastal mountain range at a height of several hundred meters and the associated thermal wind produces an alongshelf wind jet which has a maximum speed just below the inversion base turbulent mixing tends to homogenize any stratification in the marine layer beneath the jet and couple the jet to the ocean surface producing strong upwelling favorable winds over the shelf day night heating cooling over the narrow coastal strip beneath the marine layer generates a weak cross coast secondary circulation which causes the core of the alongshelf jet to drop in elevation and shift onshore this diurnal change in the marine layer structure explains both the daytime acceleration of the surface winds observed over and near the coast and its offshore decay and the associated offshore increase in the subdiurnal alongshelf wind thus the quasi steady component of the wind stress has a significant curl over the inner shelf during periods of active upwelling this mean summer atmospheric boundary layer regime is occasionally interrupted by synoptic and or mesoscale events or anomalous conditions analysis of the code observations suggests five types of events two primarily synoptic scale conditions which lead to stronger than normal upwelling favorable winds over the shelf and three primarily mesoscale events which lead to wind relaxation about half of the wind relaxation events observed in 1981 and 1982 are believed to be associated with either coastal trapped gravity currents or internal kelvin waves which propagate north ward in the marine layer along the central and northern california coastal mountain range

origin of fine scale wind stress curl structures in the benguela and canary upwelling systems numerous studies have shown the primary importance of wind stress curl in coastal upwelling dynamics the main goal of this new analysis is to describe the quikscat surface wind stress curl at various scales in the benguela and canary upwelling systems the dominant spatial pattern is characterized by cyclonic curl near continental boundaries and anticyclonic curl offshore in association with equatorward alongshore upwelling favorable wind stress at a smaller scale we demonstrate the sensitivity of the quikscat wind stress curl to coastal processes related to sea surface temperature sst mesoscale fluctuations by presenting a linear relationship between the curl and crosswind sst gradients despite the spatial and temporal sensitivity of the underlying thermal coupling coefficient a local analysis of the fraction of the curl ascribed to sst variability shows that sst is a main driver of the wind stress curl variability and magnitude over the upwelling extension zone 100 300 km from the coast in both the canary and benguela systems closer to the shore the curl patterns derived from quikscat observations are only loosely related to sst wind interactions as a working hypothesis they can also be associated with the coastline geometry and orographic effects that are likely to play an important role in local cooling processes

effects of wind stress and wind stress curl variability on coastal upwelling abstract aircraft measurements during the winter 1989 shelf mixed layer experiment smile and summer 1982 coastal ocean dynamics experiment code were used to characterize the spatial variation of the low level wind and wind stress over the northern california shelf the curl of the wind stress was calculated from directly measured turbulent stress components the accuracy of the computed curl was estimated to be adequate to map the spatial structure wintertime measurements showed a concentration of large positive curl over 1 pa 100 km 1 west of point arena regardless of wind direction due to the effects of the coastal topography on the wind fields results from summertime measurements showed a similar local maximum of positive curl west of point arena larger curl values over 3 5 pa 100 km 1 however were observed across a hydraulic jump propagating from stewarts point for highly supercritical marine boundary layer flow a two layer vertically integrated numerical model of coastal upwellin

3d fold growth in transpression abstract geological folds in transpression are inherently 3d structures hence their growth and rotation behavior is studied using 3d numerical finite element simulations upright single layer buckle folds in newtonian materials are considered which grow from an initial point like perturbation due to a combination of in plane shortening and shearing i e transpression the resulting fold growth exhibits three components 1 fold amplification vertical 2 fold elongation parallel to fold axis and 3 sequential fold growth perpendicular to axial plane of new anti and synforms adjacent to the initial fold generally the fold growth rates are smaller for shearing dominated than for shortening dominated transpression in spite of the growth rate the folding behavior is very similar for the different convergence angles the two lateral directions always exhibit similar growth rates implying that the bulk fold structure occupies an increasing roughly circular area fold axes are always parallel to the major horizontal principal strain axis max i e long axis of the horizontal finite strain ellipse which is initially also parallel to the major horizontal instantaneous stretching axis isa max after initiation the fold axes rotate together with max sequential folds appearing later do not initiate parallel to isa max but parallel to max i e parallel to the already existing folds and also rotate with max therefore fold axes do not correspond to passive material lines and hinge migration takes place as a consequence the fold axis orientation parallel to max is independent of convergence angle and viscosity ratio therefore a triangular relationship between convergence angle amount of shortening and fold axis orientation exists if two of these values are known the third can be determined this relationship is applied to the zagros fold and thrust belt to estimate the degree of strain partitioning between the simply folded belt and the bordering strike slip fault system

numerical simulation of topographically forced mesoscale variability in a well mixed marine layer abstract a simple nonlinear numerical model of a well mixed marine layer is used to study topographically forced mesoscale variability off coastal california the model is used to simulate a persistent wind maximum observed near point conception during northwesterly winds the model also demonstrates the development of a coastally trapped kelvin wave and a marine layer eddy when the large scale forcing is suddenly reduced the model is a one layer two dimensional gridpoint model with idealized coastal topography the model assumes that potential temperature and wind are constant with height in the layer and that the layer is capped by an inversion effects of diabatic heating water vapor entrainment and spatial variations of potential temperature are neglected in order to focus on topographic effects the model solves for the two horizontal components of the marine layer wind and the marine layer height a comparison of the model results with observations taken near point conception during the 1983 o

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

objective maps of near surface flow states near point conception california abstract objective streamfunction and velocity potential maps of three commonly observed flow states near point conception california are derived from moored current meter and drifter observations the states are defined using current meter data drifter data are sorted by flow state and averaged within spatial bins to resolve their spatial structures spatial correlations of drifter data show the along shelf and cross shelf decorrelation distances are approximately 45 and 25 km respectively this information is used to make the objective streamfunction and velocity potential maps the total velocity is represented as the sum of the rotational nondivergent streamfunction component and the irrotational divergent velocity potential component the velocity derived from the streamfunction is much stronger than that derived from the velocity potential the streamfunction is sufficiently well resolved to make meaningful vorticity maps the velocity potential indicates a source term in the western santa bar

circulation in the santa maria basin california during 1998 1 moored observations and numerical model results are used to describe the circulation during 1998 in santa maria basin smb and santa barbara channel sbc located to the northwest and southeast respectively of a bend in the southern california coastline singular value decomposition svd analysis of observed wind stress and currents yields a first mode that represents large scale alongshore flow variability that appears to be wind driven and a second mode which mostly represents flow variability in sbc and appears coherent with wind stress shear there a three dimensional numerical ocean circulation model is used to simulate the flow the model derived surface heat flux is most similar to observation derived values in summer and least similar in winter and more similar in smb than in sbc empirical orthogonal function eof analysis of the coriolis and pressure gradient terms for modeled near surface currents supports the hypothesis that the large scale flow variability of the first mode is wind driven it further suggests that an alongshore pressure gradient drives the poleward flow along sbc s northern shelf wind stress curl of which the shear along sbc is a part or its gradient may govern such a pressure gradient although this could not be ascertained modeled and observed currents are similar in their directions but both the annual mean and variance tend to be smaller for modeled flow svd analysis shows that modeled and observed flows have similar modes of variability remotely driven flow may play a role in smb especially in summer

flow around a coastal bend a model of the santa barbara channel eddy a steady equatorward wind stress is applied over a two layer ocean infinitely deep lower layer west of an otherwise straight meridional coast with a right angle bend initial t 10 days response consists of an equatorward current kelvin wave that triggers a cyclone around the bend through viscous production and advection of vorticity a process akin to eddy shedding in flows without rotation the response at large times is governed by a kelvin wave forced by the equatorward weakening of the assumed positive wind stress curl which produces a poleward current near the coast application to the santa barbara channel cyclone is discussed and the cyclone formation process is further demonstrated with a three dimensional model with topography and stratification

fracture zones constrained by neutral surfaces in a fault related fold insights from the kelasu tectonic zone kuqa depression abstract stress variation associated with folding is one of the controlling factors in the development of tectonic fractures however little attention has been paid to the influence of neutral surfaces during folding on fracture distribution in a fault related fold in this study we take the cretaceous bashijiqike formation in the kuqa depression as an example and analyze the distribution of tectonic fractures in fault related folds by core observation and logging data analysis three fracture zones are identified in a fault related fold a tensile zone a transition zone and a compressive zone which may be constrained by two neutral surfaces of fold well correlation reveals that the tensile zone and the transition zone reach the maximum thickness at the fold hinge and get thinner in the fold limbs a 2d viscoelastic stress field model of a fault related fold was constructed to further investigate the mechanism of fracturing statistical and numerical analysis reveal that the tensile zone and the transition zone become thicker with decreasing interlimb angle stress variation associated with folding is the first level of control over the general pattern of fracture distribution while faulting is a secondary control over the development of local fractures in a fault related fold

methods for determining deformation history for chocolate tablet boudinage with fibrous crystals abstract chocolate tablet boudinage with fibrous crystal growths between the boudinaged plates from two localities were studied in one from leytron valais switzerland the deformation history was found to be a succession of plane strain increments with the shortening direction perpendicular to the boudinaged sheet and the extension direction showing a progressive change in orientation within the sheet the incremental and finite strains were evaluated the other specimen from parys mountain anglesey great britain was found to have a more complex history with diachronous break up of the competent layer and flattening strain increments it was found that under these circumstances the direct graphical methods of determining finite and incremental strains gave inconsistent results a numerical model was developed which allowed the simulation of chocolate tablet structure with a complex deformation history the model was applied to the anglesey specimen and three possible strain histories for this structure were tried

numerical simulations of parasitic folding in multilayers we use the finite element method to simulate slow viscous newtonian flow in two dimensions without gravity and to model asymmetric sand z shaped and symmetric m shaped parasitic folds during multilayer folding during multilayer folding the matrix between stiffer layers shows a deformation close to pure shear in the hinge area and a combination of pure and simple shear in the limb areas thinner layers placed between thicker layers develop symmetric parasitic folds in the hinge and eventually asymmetric parasitic folds in the limbs of the larger fold our results verify numerically the theory that asymmetric parasitic folds develop from symmetric buckle folds that are sheared by the hingeward relative displacement of the thick layers in the limbs of the first order fold to develop asymmetric shapes the amplitudes of the parasitic folds must exceed a critical value before the first order fold begins to amplify otherwise the parasitic folds are unfolded during flattening that takes place in the limb area between the thick layers more than five thin layers are necessary to generate distinct asymmetric parasitic folds for the applied model setting more layers generate higher amplification rates in the thin layers and hence higher amplitudes 2006 elsevier ltd all rights reserved

book reviewthe techniques of modern structural geology vol 1 strain analysis j g ramsay and m i huber academic press london 1983 xiii 307 pp us 55 00 28 00 hardcover

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

statistical aspects of surface drifter observations of circulation in the santa barbara channel argos tracked drifters are used to study the near surface circulation in the santa barbara channel the mean consists of a cyclonic cell in the western santa barbara channel with weaker flow in the eastern channel drifter mean velocities agree well with record means from near surface current meters at the eastern entrance to the channel drifter velocities are biased toward outflow eastward velocity conditions drifter variability at synoptic and seasonal scales shows a tendency for upwelling and eastward flow in spring a strong cyclonic circulation in summer poleward relaxation in fall and weak variable circulation in winter drifter estimates of eddy stress divergence indicate advective terms play a secondary role in the mean surface momentum balance lagrangian time and space scales are about 1 day and under 10 km respectively the mismatch between lagrangian and eulerian timescales indicates advective terms are important to the fluctuating circulation

outcrop scale tomography insights into the 3d structure of multiphase boudins abstract we analyze the 3d geomorphology of a boudinaged amphibolite layer encased in marble using meter scale tomography by serial sectioning high resolution imaging and 3d reconstruction of a 2 m block from a quarry in the high grade core of the naxos core complex local uncertainties in the model are resolved by dissolution of marble in selected slabs yielding a large highly accurate 3d model results show five generations of brittle extension of the amphibolite in ductile marble although examination of the boudinaged layer on the outside of the block only suggested one generation most prominent are the rotated domino boudins where part of the dilatancy between domino boudins can be shown to be due to later reactivation shear fractures between domino boudins have relatively large throw gradients indicating ductile rupture layer parallel stretch as measured by reconstruction of domino boudins decreases with amphibolite layer thickness although the layer has undergone the same bulk stretch everywhere this suggests that with decreasing layer thickness deformation becomes delocalized offering tantalizing glimpses of rheology under metamorphic conditions

northerly surface winds over the eastern north pacific ocean in spring and summer 1 persistent spring and summer northerly surface winds are the defining climatological feature of the western coast of north america especially south of the oregon coast northerly surface winds are important for upwelling and a vast array of other biological oceanic and atmospheric processes intermittence in northerly coastal surface wind is characterized and wind events are quantitatively defined using coastal buoy data south of cape mendocino on the northern california coast the defined wind events are then used as a basis for composites in order to explain the spatial evolution of various atmospheric and oceanic processes wind events involve large scale changes in the three dimensional atmospheric circulation including the eastern north pacific subtropical anticyclone and southeast trade winds composites of qscat satellite scatterometer wind estimates from 1999 to 2005 based on a single coastal buoy indicate that wind events typically last 72 96 h and result in anomalies in surface wind and ekman pumping that extend over 1000 km from the west coast of north america it may be useful to consider ocean circulation and dependent ecosystem dynamics and the distribution of temperature moisture and aerosols in the atmospheric boundary layer in the context of wind events defined herein

wind forcing of the coastal circulation off north and northwest iberia comparison of atmospheric models 1 comparisons between observed winds and winds from reanalysis national centers for environmental prediction ncep reanalysis 1 and 2 and forecast meteorological models high resolution limited area model hirlam agencia estatal de meteorologia 0 2 and atmospheric research mesoscale model version 5 meteogalicia with 30 km and 10 km resolution have been performed for the coastal region around northwest and north iberia during a typical autumn downwelling period september december 2002 observations at buoys and coastal stations and quikscat derived winds were employed the analyzed period was dominated by southerly and southwesterly winds associated to the passage of low pressure systems our results show that the westward component is higher on the north coast than on the west coast and that winds are intensified at the western north coast in this situation the performance is similar in all model products in general terms but only hirlam represents the reduction of winds in the cantabrian sea and ncep and mm5 overestimate the magnitude of south southwest winds spatial differences in winds are also obtained for upwelling favorable events associated either with a high pressure system north from iberia at the beginning of the autumn transition northeasterly winds or with conditions after the passage of a low pressure system northwesterly winds the existence of sea surface temperature sst gradients in the coastal region implies that higher resolution boundary sst products for meteorological models are necessary finally the effect of these wind products on the coastal circulation was assessed with a 3 d numerical simulation differences in the expansion confinement of river plumes and the surface speed of the slope current are induced by differences in wind patterns over the shelf and slope area among atmospheric models

a new geodynamic interpretation for the south portuguese zone sw iberia and the iberian pyrite belt genesis 1 the south portuguese zone spz constitutes the southernmost segment of the variscan iberian massif it is bounded to the north by the beja acebuches ophiolitic complex and related accretionary wedge to the south lie the iberian pyrite belt ipb and flysch deposits forming the southern extent of the zone structural analysis within the spanish side of the spz supports continuous south propagating deformation evolving from early synmetamorphic thrusting in the internal zone to thin skinned tectonics in the southern external domain the accretion of the spz to the ossa morena zone is also witnessed by the presence of various melanges observed throughout the investigated area part of the melanges observed in the ipb are related to the volcanics and mineralizations setting a key point to understand the ipb mineralizations genesis is to constrain the volcanogenic model one underestimated feature is the large amount of submarine calc alkaline ignimbritic facies implying the presence of caldera structures within the province such correlation between caldera environment and ore deposits strongly suggests that the ipb developed in a continental arc our geodynamic model proposes an early north directed subduction associated with the obduction of the oceanic crust toward the south southward this episode is immediately followed by the development of the accretionary prism while farther south a second subduction zone responsible for the arc setting of the ipb initiates subsequent visean continental collision is associated with the deposit of the south propagating flysch and the present geometry of the spz

stress orientation and fracturing during three dimensional buckling numerical simulation and application to chocolate tablet structures in folded turbidites sw portugal abstract two orthogonal sets of veins both orthogonal to bedding form chocolate tablet structures on the limbs of folded quartzwackes of carboniferous turbidites in sw portugal structural observations suggest that 1 mode 1 fractures transverse to the fold axes formed while fold amplitudes were small and limbs were under layer subparallel compression and 2 mode 1 fractures parallel to the fold axes formed while fold amplitudes were large and limbs were brought to be under layer subparallel tension we performed two and three dimensional numerical simulations investigating the evolution of stress orientations during viscous folding to test whether and how these two successive sets of fractures were related to folding we employed ellipses and ellipsoids for the visualization and quantification of the local stress field the numerical simulations show a change in the orientation of the local 1 direction by almost 90 with respect to the bedding plane in the fold limbs the coeval 3 direction rotates from parallel to the fold axis at low fold amplitudes to orthogonal to the fold axis at high fold amplitudes the stress orientation changes faster in multilayers than in single layers the numerical simulations are consistent with observation and provide a mechanical interpretation for the formation of the chocolate tablet structures through consecutive sets of fractures on rotating limbs of folded competent layers

intermittent existence of a southern californian upwelling cell during submillennial climate change of the last 60 kyr 1 application of a high resolution multiproxy approach to a sedimentary section drilled at ocean drilling program site 1017 located under a highly active upwelling cell off point conception california provides clear evidence for surface ocean productivity shifts on submillennial timescales during the last 60 kyr the proxies include bulk sediment major and minor elements organic carbon and carbonate concentrations 15n and planktonic foraminiferal species assemblage and carbon isotope determinations the collective results demonstrate that marine productivity in this area was not simply linearly related to cold and warm cycles except during the millennial scale climate oscillations of marine isotope stage mis 3 during that interval the upwelling cell and resulting high productivity were active during warm interstadial events and were largely inactive during cool stadial events however the last glacial maximum was also relatively productive productivity increased dramatically during the bolling warm interval while the allerod and younger dryas were much less productive high coccolithophorid abundance commenced during the earliest holocene after 10 ka the complexity of the productivity response was probably related to interplay between local winds as well as california undercurrent strength

circulation in the point conception santa barbara channel region during spring and early summer 1983 fifteen current moorings were deployed around the periphery of santa barbara channel and over the continental shelf to the west off point conception data from these moorings have been used to describe the regional circulation and to address problems of wind forcing and the spatial coherency scales for current fluctuations the mean circulation in santa barbara channel was dominated by a westward jet which occupied the northwestern portion of the channel current and temperature fluctuations were generally well correlated among all locations around the channel and time lags suggested cyclonic propagation of events around the channel the time fluctuations were dominated by a relatively few low frequency events it was impossible to determine exactly either the driving mechanisms for these events or their relationships to regional flow the flow regime was considerably different off point conception than in the channel locally wind driven upwelling was observed in both the mean and fluctuating flows and the time scales of current variability i e spectral shapes mimicked those of the local winds a dramatic change in the regime off point conception occurred in late may before the transition currents and sea levels had been well correlated in time with both local and remote winds after late may the relation to fluctuating winds was less clear and the alongshore structure of sea level variability had changed radically

large scale structure of the spring transition in the coastal ocean off western north america past measurements off the coast of central oregon and washington have shown that the rapid change from northward monthly mean winter winds to southward summer winds forces a spring transition of the coastal ocean sea levels and temperatures drop and mean surface currents shift from northward to southward current and water temperature data from 35 n to 48 n from 1981 and 1982 and sea level and wind stress data from 1971 1975 and 1980 1983 show the transition to have a large alongshore scale typically 500 to 2000 km the large scale wind stress appears to be the forcing mechanism at latitudes north of approximately 37 n south of 37 n sea level usually falls more gradually before the northern transition event both wind and sea level events generally progress from south to north over a 3 to 10 day period but this is not always true several aspects of the spring transition reflect coastal trapped wave dynamics previous studies at 45 n found persistent vertical shear of the southward summer current associated with a cross shelf density gradient during 1982 the shear and the density front develop over the shelf break immediately after the transition at 43 n and to the south but they are much less persistent than at 48 n the stronger winds between 38 n and 42 n and the narrower shelf result in an offshore displacement of the density front and vertical shear past the shelf break leaving the water over the shelf less stratified and more subject to barotropic reversals of the current than that farther north where the front stays closer to the coast

on the inner shelf circulation in the northern gulf of cadiz southern portuguese shelf abstract a new look at the inner shelf circulation in the northern gulf of cadiz sw iberian peninsula is taken results reveal the introduction of a sharp spatial heterogeneity in the wind field by the coastal geometry around cape st vincent and nearby mountain chains direct observations taken in november december 2001 reveal the alternating nature of the coastal flow along the sw iberian peninsula featuring a sharp current inversion on time scales of less than 2 days along shore gradients of the oceanic wind stress were detected which may contribute to the coastal circulation patterns in the region over the observational period the sea level variability in the gulf of cadiz is better explained by the action of along shore winds outside the gulf than by local winds this is confirmed by a scale analysis done on the vertically integrated momentum equation it is shown that to a first approximation the expected behaviour of the inner shelf flow responds to linear dynamics in this approximation the along shore sea level slope 5 cm over 100 km is the dominant term overriding the linear bottom and surface stress terms this suggests control by large scale atmospheric pressure systems and negligible dynamical influence from local wind stress

evolution of the specific surface area of snow during high temperature gradient metamorphism the structural evolution of low density snow under a high temperature gradient over a short period usually takes place in the surface layers on clear cold nights in this paper x ray computed microtomography microct was combined with numerical simulations to investigate the temperature gradient metamorphism tgm on different types of snow precipitation particles pp small rounded particles rgsr and large rounded particles rglr were each observed in high temperature gradients 100 500 k m 1 at a mean temperature of 4 c the specific surface area ssa was used to characterize the tgm which were influenced by both the magnitude of the temperature gradient and the initial snow structures pp samples experienced a logarithmic decrease of ssa with time and the depth hoar structures created under high tgm 500 k m 1 have higher ssa compared to those under lower tgm unlike previous observations for initial rounded and connected structures like rglr samples the ssa increased during tgm simulated normal vapor flux distributions for different snow types were used to help understand the structural evolution under tgm understanding the ssa increase is important in order to predict the enhanced uptake of chemical species by snow or increase in snow albedo

effects of small scale wind on coastal upwelling with application to point conception a three dimensional limited area ocean general circulation model is used to study the response of the coastal ocean to small scale wind forcing the model considers an idealized forcing of a semi infinite upwelling favorable wind with a large positive wind curl at one end such a wind pattern is commonly found in the vicinity of capes and points where the synoptic scale wind is disturbed by coastal mountain ranges the model study includes both process and hindcast studies the process study considers the upwelling spinup and relaxation driven by a positive wind curl it also examines the model sensitivity to wind patterns and an external pressure force the model results show that a strong poleward alongshore pressure gradient is set up by a positive wind curl this pressure force drives an inshore poleward current into the upwelling region during active wind forcing and it causes a surge of warm water into the upwelling zone during wind relaxation the hindcast study is applied to the 1983 organization of persistent upwelling structures opus observations near point conception off central california the simulation uses an idealized geometry but with observed winds during opus a sudden reversal of the surface equatorward currents occurred in the midst of a steady upwelling favorable wind this unexpected coastal flow feature was faithfully reproduced in the model simulation

wind induced currents and bottom trapped waves in the santa barbara channel the santa barbara channel sbc is a coastal basin about 100 km long bounded by the southern california mainland on the north and by a chain of islands on the south the sbc is at most 50 km wide and just over 600 m deep the nature of current and wind variance peaks in the 2 4 day and 4 6 day bands in the channel are analyzed from january to july 1984 for both bands the dominant empirical mode of the currents is highly coherent with the dominant empirical mode of the winds over this region surface intensification of currents is revealed by measurements made between 25 and 300 m in contrast the deeper currents are characterized by bottom trapping evidence for baroclinic bottom trapped topographic rossby waves is found on the northern shelf at the western mouth of the channel in both frequency bands at 30 m the distribution of phases shows currents at the center of the western mouth leading the southern interisland passes by about 0 3 day and the eastern mouth by about 0 6 day in both bands co and quadrature vectors of currents and winds describe this wind current system in detail it is speculated from spatial and temporal eigenfunctions of currents and winds and from available satellite images that the dominant current mode described above is a channelwide response to upwelling north of point conception northwestward of the sbc the upwelling related currents cause a net inflow of mass into the western end of the channel which is compensated by an outflow passing through both the interisland passes and through the eastern mouth of the channel as a result of the narrowness and shallowness of the passes and of the shallowness of the southern shelf in general high flow speeds are attained there that the authors speculate seem to force deep high frequency motions both at the center of the sbc and at the northern half of its western mouth

sensitivity of coastal currents near point conception to forcing by three different winds ecmwf coamps and blended ssm i ecmwf buoy winds previous observational and modeling studies have indicated the importance of finescale winds in determining the circulation near point conception in the santa maria basin smb and the santa barbara channel sbc california there has not been a systematic attempt however to analyze and quantify the sensitivity of the near surface circulation to different wind data here a regional circulation model of the smb and sbc is driven using three wind datasets the european centre for medium range weather forecasts ecmwf 110 km 110 km horizontal grid the coupled ocean atmosphere mesoscale prediction system coamps 9 km 9 km horizontal grid and a blended wind product that combines special sensor microwave imager ssm i ecmwf and buoy and coastal wind data and that is referred to as seb a springtime period march may 1999 in which equatorward wind dominates and wind stress curls are strong is chosen for the study two groups of experiments are conducted with and without assimilating moored temperature observations the focus is on long time scales of greater than weeks and on mean currents comparisons between these experiments and between model and observation show that the circulation driven by the ecmwf wind is much weaker than that by the other two winds on the other hand the seb dataset shows locally intensified wind stress curls behind capes and coastal bends whereas these wind stress curls are weak in coamps it is found that these small scale variations in the wind field force alongshore inhomogeneous pressure gradients that in turn can significantly affect the near coast currents the result is that modeled currents forced by seb agree better with observations than do those produced by coamps empirical orthogonal function analyses were conducted on the near surface currents sea level wind and wind stress curl the mode 1 current 40 is unidirectional i e generally equatorward or poleward and correlates well with the mode 1 wind 90 the mode 2 current 20 is cyclonic in the sbc and poleward inshore and equatorward offshore in the smb it correlates well with mode 1 sea level 70 which suggests that mode 2 currents are driven by the pressure gradient it is significant that neither mode 2 current nor mode 1 sea level correlates well with mode 1 wind stress curl 70 rather they correlate well with the time integral of the mode 1 wind stress curl these conclusions support a previous theoretical idea that cyclonic circulation in the sbc and the inshore currents of the smb are both driven by alongshore pressure setup induced by the time integral of the wind stress curl rather than by the wind stress curl itself this idea of a pressure setup is consistent with the differences found between the currents driven by coamps and seb winds

poleward flow off central california during the spring and summer of 1981 and 1984 currents and winds measured over the continental shelf and upper continental slope during the first half of 1984 are analyzed to determine the character of the flow off central california point conception to san francisco the mean flow was poleward from point conception to point sur in opposition to the equatorward wind stress the mean flow was equatorward north of point sur fluctuations in alongshore currents over the shelf were highly correlated with local winds everywhere except off point conception where currents were not only uncorrelated with wind but also poorly correlated with currents farther north north of point buchon there is evidence for poleward propagation of shelf current variability at 175 200 cm s the correlation between currents and local wind forcing dropped considerably beyond the shelf break only 10 15 km offshore from the shelf moorings during extended periods of weak equatorward winds the poleward shelf flow south of point sur spreads farther offshore over the continental slope a three week period of calm winds in july 1984 resulted in a 100 km wide tongue of poleward flow extending 300 km along the california coast similar but somewhat weaker poleward surface flow occurred during the same period in 1981 a 2 to 3 week period of calm winds in late june and early july 1981 resulted in a 100 km wide tongue of poleward flow extending at least 150 km along the california coast in contrast to the poleward flow on the shelf which appears to be normal during spring and summer the poleward surface flow observed over the slope in july 1981 and 1984 is unusual based on historical hydrographic surveys off the central california coast poleward surface flow over the continental slope occurs seasonally in the winter but is not generally observed after february

theory of chocolate tablet boudinage two dimensional boudinage in a flattening type of bulk deformation with equal layer parallel extensions in all directions leads to the development of roundish or polygonal outlines of boudins in plan view as combined experimental and theoretical studies show chocolate tablet boudinage with two sets of mutually perpendicular boudin axes may form in different ways 1 unequal layer parallel extension in the matrix results in one set of extension fractures forming perpendicular to the greatest principal stress in the matrix once these long narrow boudins are formed the greatest principal stress in the brittle layer becomes approximately parallel to the long axis of the boudin as a result a second set of fractures forms normal to the first set 2 in lineated rocks the anisotropy of tensile strength leads to the sequential formation of two sets of extension fractures parallel and perpendicular to the lineation depending on the orientation of the lineation the boudin axes may or may not be parallel to the principal stresses in the matrix 3 boudins with rectangular plan view may also form when two successive events of unidirectional boudinage are superposed on one another irrespective of the direction of principal extensional strain rate in the matrix the second generation extension fractures are likely to form approximately perpendicular to the first generation boudin axes

orographically trapped coastal wind events in the pacific northwest and their oceanic response three ageostrophic orographically trapped wind events in the coastal zone of the pacific northwest are examined time series of wind speed wind direction air temperature sea level pressure ocean currents and ocean temperature are utilized to establish the general features of these events and to characterize the oceanic response it is suggested that these atmospheric events are highly nonlinear bores or gravity currents rather than quasi linear kelvin waves observed oceanic responses include a drop in sea surface temperature sst of 1 3 c offshore to approximately 150 km approximately the atmospheric rossby radius and a rise in sst of similar magnitude within 15 km of the shore a set of reduced gravity fully nonlinear single layer models is utilized to investigate the dynamics of the atmospheric features and their oceanic response and a possible air sea interaction the models reproduce several of the first order features of the air and sea phenomena such as the development of the atmospheric front and the wake of near inertial waves in the ocean

fluid assisted particulate flow of turbidites at very low temperature a key to tight folding in a submarine variscan foreland basin of sw europe 1 the problem addressed in this article is how sedimentary formations like turbidites in a foreland basin which include layers with apparently great competence contrast can be tightly folded in a regular manner under very low temperature and pressure this raises two major issues the rheological behavior of the rocks at the time of folding and the role played by fluids in order to understand very low temperature folding and the structural evolution of a submarine foreland basin we carried out detailed structural work in turbidites with alternating sandstone and shale for which estimated peak temperature conditions were top diagenetic to very low grade metamorphism folds are tight to isoclinal with local collapsed hinges which implies that the incompetent shale was mobile enough to flow away from strongly flattened areas we did not find evidence for cataclastic flow or crystal plasticity at mesoscopic and microscopic scales other structures mostly boudins foliations conjugate brittle faults and quartz veins associated with folds denote anisotropic compaction by fluid extraction during regional shortening this is possible if the folded rocks were unconsolidated fluid saturated sediments the estimated low peak temperature is consistent with the shale being unlithified poorly cemented grains are free to slide past one another under shallow burial or high pore pressure conditions following this line of thought we consider independent particulate flow assisted by fluids under very low confining pressure bean bag analogy as the rock deformation mechanism active during the described intense folding similar deformation is likely occurring and has occurred in other submarine accretionary wedges

stress evolution during 3d single layer visco elastic buckle folding implications for the initiation of fractures abstract buckle folds of sedimentary strata commonly feature a variety of different fracture sets some fracture sets including outer arc tensile fractures and inner arc shear fractures at the fold hinge zones are well understood by the extensional and compressional strain stress pattern however other commonly observed fracture sets including tensile fractures parallel to the fold axis tensile fractures cutting through the limb extensional faults at the fold hinge and other shear fractures of various orientations in the fold limb fail to be intuitively explained by the strain stress regimes during the buckling process to obtain a better understanding of the conditions for the initiation of the various fractures sets associated with single layer cylindrical buckle folds a 3d finite element modeling approach using a maxwell visco elastic rheology is utilized the influences of three model parameters with significant influence on fracture initiation are considered burial depth viscosity and permeability it is concluded that these parameters are critical for the initiation of major fracture sets at the hinge zone with varying degrees the numerical simulation results further show that the buckling process fails to explain most of the fracture sets occurring in the limb unless the process of erosional unloading as a post fold phenomenon is considered for fracture sets that only develop under unrealistic boundary conditions the results demonstrate that their development is realistic for a perclinal fold geometry in summary a more thorough understanding of fractures sets associated with buckle folds is obtained based on the simulation of in situ stress conditions during the structural development of buckle folds

coupled ocean atmosphere nested modeling of the adriatic sea during winter and spring 2001 1 realistic simulations of the adriatic sea for over 125 days are conducted using the navy coastal ocean model with atmospheric forcing provided by the coupled ocean atmosphere mesoscale prediction system coamps is a registered trademark of the naval research laboratory coamps in two separate simulations of the adriatic a nested 2 km resolution ocean model is forced by the inner 4 km and outer 36 km nests of the atmospheric model two meteorological stations and two acoustic doppler current profiler observation sites are used to evaluate modeled atmosphere and ocean velocity fields for 28 january 4 june 2001 modeled observed correlations of atmospheric 10 m velocity are greater than 0 85 for both resolution models oceanic 5 and 25 m current fluctuations from both simulations generally match the magnitude and orientation of the observations the 4 km resolution atmospheric model is differentiated from the 36 km resolution model by its ability to resolve the small scale flow structures of the bora wind and by its better agreement with observed wind velocity statistics the ocean simulation forced by the 4 km resolution model is distinguished from the one forced by the 36 km resolution model by its ability to reproduce the expected double gyre circulation in the northern adriatic and by its ability to better capture the magnitude and shape of the observed depth dependent velocity correlation with wind at the deeper site though the 36 km forced ocean model agrees better with many observed velocity statistics the 4 km forced ocean model produces the highest correlations with observations exceeding 0 78 at subsurface depths that are most strongly correlated with winds

surface boundary layer variability off northern california usa during upwelling abstract a five element mooring array is used to study surface boundary layer transport over the northern california shelf from may to august 2001 in this region upwelling favorable winds increase in strength offshore leading to a strong positive wind stress curl we examine the cross shelf variation in surface ekman transport calculated from the wind stress and the actual surface boundary layer transport estimated from oceanic observations the two quantities are highly correlated with a regression slope near one both the ekman transport and surface boundary layer transport imply curl driven upwelling rates of about 3 10 4 m s 1 between the 40 and 90 m isobaths 1 5 and 11 0 km from the coast respectively and curl driven upwelling rates about 1 5 10 4 m s 1 between the 90 and 130 m isobaths 11 0 and 28 4 km from the coast respectively thus curl driven upwelling extends to at least 25 km from the coast in contrast upwelling driven by the adjustment to the coastal boundary condition occurs primarily inshore of the 40 m isobath the upwelling rates implied by the differentiating the 40 m transport observations with the coastal boundary condition are up to 8 10 4 m s 1 the estimated upwelling rates and the temperature nitrate relationship imply curl driven vertical nitrate flux divergences are about half of those driven by coastal boundary upwelling

shipboard acoustic doppler profiler velocity observations near point conception spring 1983 during april 1983 shipboard doppler acoustic log current profiles were collected in an effort to characterize the flow field near points conception and arguello california subsurface velocity maps derived from these profiles have been used to describe spatial flow structures both on and off the shelf and to investigate flow variability as a function of time and of wind stress persistent westward flow out of the northern half of the santa barbara channel and eastward flow into its southern half were observed regardless of the direction of the local wind stress during one well documented upwelling favorable wind event currents responded in the form of an energetic maximum 21 m speeds of 60 cm s 1 offshore squirt of cold water during weak or downwelling favorable winds currents continuous with the santa barbara channel outflow were observed flowing to the northwest following the local isobaths before turning offshore west of point arguello evidence for wind forcing of current fluctuations nearshore between the points and north of point arguello was found lack of a thermal wind balance between directly measured velocity shear and horizontal density gradient was explained by the presence of large accelerations in the momentum equations lack of a consistent relation between velocity and temperature gradient illustrates the difficulty in estimating velocity from temperature information alone in this area

polyphase development of chocolate tablet boudins in the sat zone kumaun lesser himalaya india abstract a combination of two groups of boudins exposed in orthogonal sections is observed as chocolate tablet structures in the south almora thrust sat zone kumaun lesser himalaya evidence from boudin associated veins fractures folds and microstructures suggest that the chocolate tablet boudins were developed as a consequence of layer parallel stretching in two orthogonal directions during two successive phases of ductile shearing in the sat zone the early phase of top to nw shearing is speculated as a pre himalayan deformation during which the early boudins were developed this deformation was superposed by a late phase of top to sw himalayan shearing and development of the attendant late boudins it is concluded that the interference of two phases of successively developed boudins has resulted into development of the chocolate tablet structures in the sat fluid inclusion and microstructures indicate a low temperature about 300 c growth of the chocolate tablet boudins the finite strain analysis reveals that a maximum strain ratio rs of 1 7 was accumulated during the pre himalayan phase of deformation whereas rs was of the order of 2 1 in the himalayan phase of deformation

satellite observations of small coastal ocean eddies in the southern california bight this study describes the characteristics of extensive small scale coastal ocean eddies in the southern california bight these surface features were primarily detected by using ers 1 and ers 2 synthetic aperture radar sar satellite imagery from 1992 to 1998 the eddies predominantly cyclonic in their rotation appeared to result from several forcing mechanisms they were mainly observed within the santa barbara channel and the santa monica san pedro basin regions and appeared to be seasonal in their distribution observed eddy diameters were all less than 50 km with over 70 less than 10 km the sar data were complemented by sea surface temperature measurements derived from advanced very high resolution radiometer satellite imagery as well as in situ data from moorings and drifters that provided substantial verification of the small scale eddies these findings are significant in that the eddies were in general smaller in size and more abundant than previously reported additionally these results provide further evidence of the complex near surface circulation within the southern california bight with important implications for nutrient flux productivity plankton patchiness larval transport and recruitment and dispersal of pollutants

short term upwelling events at the western african coast related to synoptic atmospheric structures as derived from satellite observations satellite scatterometers provide continuously valuable surface wind speed and direction estimates over the global ocean on a regular grid both in space and time the level 3 data derived from the advanced scatterometer ascat available at 1 4 spatial resolution hereafter as25 and quick scatterometer quikscat available on 1 2 and 1 4 horizontal grids qs50 and qs25 respectively are studied at regional scales in both the benguela and canary upwelling systems they are compared to the european center for medium range weather forecast surface wind analysis with insight into their intrinsic and actual spatial resolutions in the coastal band the finest spatial patterns are found in the qs25 winds and are o 75 km this demonstrates the sensitivity of the high resolution satellite derived winds to coastal processes related to sea surface temperature sst perturbations and land sea transition next short lived upwelling episodes sues calculated from sst anomalies are defined consistently with the qs25 actual resolution these cold events refer to local short lived perturbations that add to seasonal upwelling variability we characterize concomitant atmospheric synoptic conditions for sues identified at chosen latitudes and highlight two subregions in both upwelling systems with contrasted patterns for the alongshore wind stress component and curl the complexity of the latter patterns is closely linked to local short term sst variability closer to the shore numerical sensitivity experiments show that the imbalance between ekman transport and ekman pumping has an impact on ocean dynamics wind reduction in the coastal qs25 forcing partially induced by orography tends to reduce coastal sst cooling

3d numerical modeling of forward folding and reverse unfolding of a viscous single layer implications for the formation of folds and fold patterns abstract the main aims of this study are to show i that non cylindrical three dimensional 3d fold shapes and patterns can form during a single unidirectional shortening event and ii that numerical reverse modeling of 3d folding is a feasible method to reconstruct the formation of 3d buckle folds 3d viscous newtonian single layer folding is numerically simulated with the finite element method to investigate the formation of fold shapes during one shortening event an initially flat layer rests on a matrix with smaller viscosity and is shortened in one direction parallel to the layering forward modeling with different initial geometrical perturbations on the flat layer and different lateral boundary conditions generates non cylindrical 3d fold shapes and patterns the simulations show that in reality the initial layer geometry and the boundary conditions strongly control the final fold geometry fold geometries produced from the forward folding models are used as initial setting in numerical reverse folding models with parameters identical to those of forward models these reverse models accurately reconstruct the initial geometry of forward models with also only one extension event parallel to the previous shortening direction the starting geometry of the forward models is inaccurately reconstructed by the reverse models if a significantly different viscosity ratio than in the forward models is used this work demonstrates that reverse modeling has a high potential for reconstructing the deformation history of folded regions and rheological constraints such as viscosity ratio reverse models may be applied to natural 3d fold shapes and patterns in order to determine if they formed i during a single or multiple deformation events and ii as active buckle folds with a viscosity ratio 1 or as passive kinematic folds without buckling this approach may find much application to fold interference patterns in particular

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

a small scale oceanic eddy off the coast of west africa studied by multi sensor satellite and surface drifter data a small scale oceanic eddy which was generated in autumn 2011 at the headland of cap vert off the coast of senegal west africa and then propagated westward into the open north atlantic ocean is studied by multi sensor satellite and surface drifter data the eddy was generated after a sudden increase of the trade winds causing an enhanced southward flow and upwelling at the coast of senegal after this wind burst event an extremely nonlinear cyclonic eddy with a radius of about 10 to 20 km evolved downstream of cap vert with rossby number larger than one our analysis suggests that the eddy was generated by flow separation at the headland of cap vert the eddy was tracked on its way into the open north atlantic ocean from satellites over 31 days via its sea surface temperature and chlorophyll a chl signature and by a satellite tracked surface drifter the satellite images show that this small scale eddy transported nutrients from the upwelling region westward into the oligotrophic north atlantic thus giving rise to enhanced chl concentration there maximum chl concentration was encountered few days after vortex generation which is consistent with a delayed plankton growth following nutrient supply into the euphotic zone within the eddy furthermore the eddy was imaged by the synthetic aperture radar sar onboard the envisat satellite it is shown that the radar signatures of cold eddies result from damping of short surface waves by biogenic surface films which arise from surface active material secreted by the biota in the cold eddy as well as by the change of the stability of the air sea interface highlights processes during the onset of coastal upwelling off west africa multi sensor remote sensing and in situ observations highly nonlinear small scale eddy generation at cap vert nrcs reduction in parts of the eddy due to biogenic surface films

coastal perturbations of marine layer winds wind stress and wind stress curl along california and baja california in june 1999 abstract month long simulations using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model mm5 with a horizontal resolution of 9 km have been used to investigate perturbations of topographically forced wind stress and wind stress curl during upwelling favorable winds along the california and baja california coasts during june 1999 the dominant spatial inhomogeneity of the wind stress and wind stress curl is near the coast wind and wind stress maxima are found in the lees of major capes near the coastline positive wind stress curl occurs in a narrow band near the coast while the region farther offshore is characterized by a broad band of weak negative curl curvature of the coastline such as along the southern california bight forces the northerly flow toward the east and generates positive wind stress curl even if the magnitude of the stress is constant the largest wind stress curl is simulated in the lees of point conception and the santa ba

fold thrust structures where have all the buckles gone special publication title folding and fracturing of rocks 50 years of research since the seminal text book of j g ramsay we dedicate the paper to the memory of martin casey 1948 2008 who did much through good humored argument to ensure that buckling ideas were not lost to what he called the ramping club the thrust belt community the fold thrust research group has been funded by interoil oilsearch and santos we thank paul griffiths and anonymous referee for comments together with hermann lebit for scientific editing the views expressed here of course remain those of the authors

structural evolution of the southernmost segment of the west european variscides the south portuguese zone sw iberia abstract the south portuguese zone spz represents the southernmost unit of the iberian massif it is mainly composed of three structural domains from north to south the beja acebuches ophiolitic complex baoc the pulo do lobo antiform pla and the iberian pyrite belt ipb this study proposes a structural analysis of the spanish part of the spz that allows us to point out two main kinds of deformation one accommodated by early top to the south and following sinistral strike slip tectonics in the northern part of the spz and the other by top to the south thrusting in a wide southern branch this transition underlining the strain partitioning is analysed by lattice preferred orientation of quartz using the texture goniometry method it shows that the deformation is accommodated in the pla at low to middle temperature by basal and prismatic a slip quartz textures suggest increasing thermal conditions of deformation from thrust to strike slip tectonics our work within the ipb allows us to present a sequence of deformation showing a primary south verging ductile thrusting and coeval crustal thickening in response to the thin skinned tectonics the progressive deformation generated backthrusts while it turns shallower southward these features are summarised in an interpretative cross section of the spz that underlines the main structural style of deformation the fore mentioned southward propagating thin skinned thrusts

three dimensional folding of an embedded viscous layer in pure shear a thick plate analysis is carried out to first order in interface slope for three dimensional folding of a single linear viscous layer of thickness h and viscosity embedded in a uniform viscous medium with viscosity 1 layer and medium are subject to a basic state of homogeneous pure shear with principal directions of strain rate x and y lying in the plane of the layer the solution is explicitly carried out for a fold perturbation in interface shape that is symmetric with respect to the principal strain rate axes f cos lx cos my but it is shown to apply to an arbitrary perturbation in the x y plane the growth rate of the perturbation is found to be are the principal strain rates of the basic state the wavenumber of the most rapidly growing perturbation d is the same as that obtained for a cylindrical perturbation m 0 in a basic state of plane strain yy 0 for maximum rate of shortening parallel to x the cylindrical fold form with axis normal to x m l 0 grows most rapidly for any ratio of yy xx 1 if yy xx all fold forms grow at the same rate and in particular an egg carton fold form is not preterentially amplified the velocity field for the perturbing flow consists of a poloidal field which solely determines the growth of the fold form and a toroidal field with non zero component of vorticity about the axis normal to the layer the latter is required to satisfy both of the two independent shear traction continuity conditions at interfaces there is no coupling between the two fields three dimensional fold forms in the appalachian plateau province in western pennsylvania are described

wind stress curl forcing of the coastal ocean near point conception california near point conception california the atmospheric flow separates from the coast and a large wind stress curl results direct spatial wind field observations from 20 aircraft overflights in the spring of 1983 suggest that ekman pumping of on average 4 m day21 contributes to the local dynamics during strong and persistent upwelling events the curl driven ekman pumping reaches up to 20 m day21 a single complex empirical orthogonal function explains more than 72 of the spatial and temporal wind stress variance it reveals large wind stress curl at the center of the western santa barbara channel entrance this dominant mode correlates strongly r 2 5 0 79 with the wind stress observed at a moored buoy the location of largest ekman pumping in the ocean indicated by this mode coincides with the location of a laterally sheared cyclonic flow cold upwelled waters enter the santa barbara channel along its southern perimeter while warm and thus buoyant waters from the southern california bight exit the channel along its northern perimeter buoy wind stress and lateral current shear at 30 m depth correlate significantly at periods of about 3 5 and 6 days with phase lags of about 0 5 and 2 days respectively hydrographic observations from 1983 do not however indicate effects of ekman pumping on the internal mass field as winds vary in speed and direction at daily timescales this contrasts with 1984 observations that do indicate strong doming of isopycnals over the center of the channel at its western entrance winds prior to and during hydrographic observations in the spring of 1984 were both stronger and more steady than they were in 1983 cyclonic shears reach 0 4 f at the entrance of the santa barbara channel near point conception here f is the planetary vorticity the thermal wind balance explains the lateral shear of the alongchannel surface flow rather well

supercritical marine layer flow along a smoothly varying coastline abstract a model for hydraulically supercritical atmospheric marine layer flow along a smoothly varying coastline is formulated and solved numerically the model is motivated by a recent comparison of code observations to a simple hydraulic theory which suggested the presence of an expansion fan and a compression jump downstream of topographic features the marine layer is modeled as a homogeneous rotating fluid layer decelerated by surface friction and forced by imposed upper level pressure gradients the equations are solved by a characteristic based gridpoint scheme the results indicate that the expansion fan is a robust feature that persists under most conditions in the present more realistic model but is dramatically altered in structure by the presence of friction while the jump may weaken rapidly offshore due mainly to offshore variations of the layer height upstream of the jump the agreement between observations and model predictions is good enough to suggest that a first order description of

baroclinic eddy generation at a sharp corner in a rotating system laboratory experiments were conducted to investigate the generation of anticyclonic gyres by separation of a surface current from a coast in a rotating two layer system the experiments were motivated by the hypothesis that the flow of coastal currents around capes can generate oceanic eddies as well as by the observation of gyres at the mouths of various straits in the experiments the gyre is formed when the current which flows with the coast to its right if one is oriented in the downstream direction encounters a sharp convex corner the current overshoots the corner loops to the right and reattaches to the coast downstream of the corner between the current loop and the coast is an anticyclone whose width grows with time if a countercurrent flows under the surface current a similar separation in the lower layer results in the generation of a cyclone as well under some circumstances the cyclone and anticyclone advect each other away from the coast as a heton previous studies on related systems found that the corner must be sufficiently sharp for a gyre to form i show that for a very sharp corner the angle made by the corner must be above a critical value of between 40 and 45 for a gyre to form this is in contrast to nonrotating flows of comparable rayleigh number which will separate from a sharp corner at virtually any angle for angles below the critical value the current profile downstream of the corner changes as a function of corner angle indicating that it is the stagnation of the flow nearest the wall which causes the anticyclone to form this stagnation is reminiscent of the two dimensional nonrotating picture of viscous boundary layer dynamics forcing separation of a boundary current however the gyre grows more slowly when the lower layer is much thicker than the upper layer indicating that baroclinic processes are at least quantitatively important in the generation of the gyre by varying the initial condition of the current it is shown that the gyre formation is not a product of the interaction of the nose of the current with the corner in conclusion the experiments indicate that the basic mechanism of gyre formation may be viscous boundary effects as in nonrotating systems but that rotation tends to inhibit eddy generation while baroclinic effects tend to enhance it

observations of the coastal upwelling region near 34 30 n of california spring 1981 abstract coordinated meteorological and oceanographic ctd measurements were made near point conception california during march april 1981 the goal of the observations was to study coastal upwelling and the local characteristics of the assumed wind driving results showed substantial topographically induced spatial structure in the near surface winds with weaker winds generally occurring within the santa barbara channel the 1981 spring transition event was monitored by mews of hydrographic and sea level measurements the details of the event suggest that it was not entirely driven by lead wind stress the mean sea surface temperature pattern suggests the existence of an upwelling center between points arguello and conception the individual sea surface temperature charts are all dominated by patchiness on a scale of 5 15 km the nature of these structures is not well understood but on the one occasion when a patch was isolated by a ctd survey its structure penetrated to at 1east 50 db

how facies and diagenesis affect fracturing of limestone beds and reservoir permeability in limestone marl alternations abstract facies and diagenetic heterogeneities in carbonate reservoir rocks affect both fracture distribution and fracture permeability many studies focussed on fracture patterns in limestone marl alternations as e g fluid flow models are based on laterally continuous beds here we examine 4010 fractures in multiple layers of limestone marl alternations using a modified scan line method the studied successions belong to the blue lias formation hettangian sinemurian exposed on the coast of the bristol channel united kingdom we combine methods of sedimentology and structural geology with rock physics to gain a better understanding of the role of facies diagenesis and petrophysical properties tensile and compressive strength hardness porosity on the distribution of fractures fracture orientation density spacing and height fracture distribution varies significantly despite similar bed thicknesses indicating that planar bedding planes i e well bedded limestones wbl and beds with bedding plane irregularities i e semi nodular limestones snl must be distinguished snl show higher percentages of non stratabound fractures 67 while they are more stratabound in wbl 57 additionally beds with variable bed thicknesses in scale of 15 m long beds exhibit a wide range of fracture spacing whereas fractures in beds with more continuous bed thicknesses are more regularly spaced considering all lithologies the percentage of non stratabound fractures increases proportionally with caco 3 content three subsections studied in detail reveal different main sedimentological and diagenetic features from early lithified over differentially compacted to physically compacted all of them are characterised by dissimilar percentages of stratabound and non stratabound fractures in limestone beds and marl interbeds our findings demonstrate that the distribution of fractures in individual well bedded limestones is not necessarily representative for successions of limestone marl alternations multiple layers should therefore be studied in outcrop analogues as basis for fluid flow models of reservoirs composed of such lithologies

subtidal inner shelf circulation near point conception california 1 we discuss connections between inner shelf and mid shelf circulation near point conception california as well as the wind forcing of inner shelf circulation point conception marks the southern edge of a major upwelling zone that extends from oregon to central california the coastline makes a sharp eastward turn at point conception and the santa barbara channel to the east is generally assumed to be an upwelling shadow consistent with this regional division inner shelf currents are strongly correlated with wind north of point conception but not in the santa barbara channel one exception to this generalization is a location in the santa barbara channel near a pass that cuts through the coastal mountains where local winds have a dominant cross shore component and directly drive cross shore currents over the inner shelf inner shelf currents in the santa barbara channel when compared with mid shelf currents in that area are weaker but strongly correlated by contrast inner shelf currents north of point conception show a far greater incidence of poleward flow than is seen over the mid shelf in that area poleward flow events lasting 1 5 days transport warm water from the santa barbara channel around point conception to the central california coast these events are associated with relaxation of the generally equatorward wind but not always with mid shelf flow reversals