a subtropical oceanic ring of magnitude storm in the eastern north atlantic physical chemical and biological properties a subtropical oceanic ring of magnitude storm that budded from the azores current was studied in the eastern north atlantic ocean in april 1999 the cyclonic eddy called leticia was centred at 32 4 n 28 7 w and extended across more than 200 km in an east west direction leticia had been previously detected by means of topex poseidon altimetry data and further intensively investigated using expendable bathythermograph and conductivity temperature depth stations the altimeter surface signature of the eddy revealed a 20 cm sea level depression an upward displacement of the 16 c isotherm of 125 m was linked to the eddy centre and geostrophic transport of the amount of water swirling cyclonically was 7 sv the temperature nitrate and oxygen anomalies on the 0 26 5 isopycnal surface inside leticia were 0 4 c 1 mol l 1 and 0 3 ml l 1 respectively with respect to surrounding waters shallowing 50 m of the deep chlorophyll maximum 0 3 mg m 3 was observed at the eddy centre associated with vertical displacements of the isotherms 100 m within the photic layer vertical excursions of the isopycnals and the deep chlorophyll maximum of more than 30 m were observed over temporal scales of a few 3 6 h integrated nitrate concentration over the photic layer was 4 fold higher inside leticia than outside however primary production rates were only slightly higher eddy diffusive fluxes across the nitracline located 30 m below the deep chlorophyll maximum ranged from 0 02 to 0 10 mmol no3 m 2 d 1 and explained 25 of the nitrate required to sustain the estimated new production 0 24 0 48 mmol no3 m 2 d 1

generation and propagation of near inertial waves in a baroclinic current on the tasmanian shelf abstractnear inertial waves niws are often an energetic component of the internal wave field on windy continental shelves the effect of baroclinic geostrophic currents which introduce both rela

breaking of internal waves and turbulent dissipation in an anticyclonic mode water eddy abstracta four month glider mission was analyzed to assess turbulent dissipation in an anticyclonic eddy at the western boundary of the subtropical north atlantic the eddy radius 60 km had a c

near inertial internal wave interactions with mesoscale fronts observations and models moored observations of near inertial currents and buoyancy fluctuations from the frontal air sea interaction experiment fasinex may be understood as nearinertial internal waves reflecting off sheared background currents the fasinex moored array measured upper ocean currents temperature and conductivity between january and june 1986 in a region of the sargasso sea heavily populated by strong upper ocean fronts the background jets associated with these features have typical cross front scales of 20km maximum currents of 0 5 m s 1 and relative vorticities of 0 3 in the vicinity of fronts observed near inertial currents have short horizontal scales show no clear horizontal phase structure and trace out elongated current ellipses with elevated across front over along front variance during these periods inertial band pass buoyancy fluctuations often correlate with major axis currents wkb ray tracing models of propagating monochromatic plane waves exhibit horizontal phase propagation and correlations between minor axis currents and buoyancy and thus cannot explain these results models of near inertial internal waves reflected or trapped by a barotropic frontal jet produce mode like structures with short horizontal scales little horizontal phase propagation and anisotropic current ellipses aligned primarily cross front model buoyancy may correlate with one or both current ellipse components depending on the incidence angle of the wave and the degree to which it reflects completely reflected waves with horizontal scales similar to those of the front and near normal incidence angle produce current ellipses and correlation patterns consistent with the observations

tentative engineering approach to scour around breakwaters in random waves an approach by which the scour depth and protection layer width around the head of vertical wall breakwaters the scour and deposition depths as well as the protection layer widths at the round head of rubble mound breakwaters in random waves can be derived is presented here the formulas for scour depth by sumer and fredsoe 1997 for vertical wall breakwaters for regular waves and fredsoe and sumer 1997 for rubble mound breakwaters for irregular waves are used they are combined with describing the waves as a stationary gaussian narrow band random process to derive the scour and deposition depths as well as protection layer widths in random waves comparisons are made between the present approach and the fredsoe and sumer 1997 random wave scour data for rubble mound breakwaters

on the response of the ocean to a moving storm the nonlinear dynamics abstract a novel and efficient numerical method is used to investigate the nonlinear equations of motion for the upper layer of a two layer ocean in which the lower layer is infinitely deep and at rest the efficiency is achieved by seeking solutions that are in a steady state translating in equilibrium with the storm oscillations are found in the wake of the storm two features of the response are attributed to the nonlinear terms in the equation of motion 1 a rapid transition from a maximum in the downwelling phase to a maximum in the upwelling phase of each oscillation followed by a gradual relaxation to the next downwelling maximum and 2 a displacement of the maximum response usually to the right of the storm track by 40 km it is shown that the horizontal pressure gradient terms can be neglected from the momentum equations for fast large storms in which case a lagrangian integration can be performed following fluid particles this enables feature 1 to be attributed to the along tra

a three dimensional baroclinic model of the irish sea formation of the thermal fronts and associated circulation a high resolution three dimensional baroclinic shelf sea model is developed and applied to the determination of the various processes influencing the generation and position of thermal fronts and the associated circulation in the irish sea the model has a horizontal grid resolution of approximately 3 6 km by 3 0 km and can resolve the thermal fronts in the region in particular in the western irish sea although the grid is not sufficiently fine to resolve small scale features along these fronts produced by baroclinic instabilities using meteorological forcing from dublin airport located close to the center of the region and tidal forcing a series of numerical experiments were performed to examine the processes influencing the location and dynamics of thermal fronts and associated circulation in the irish sea the results show a reasonable qualitative agreement with observations of the thermal stratification and the associated circulation in the western irish sea the ability of the model to reproduce the main features of the frontal structures in the region having been established it is used to examine the interannual variability of the density flow field calculations using meteorological forcing from different years show that the western irish sea fronts and the associated cyclonic circulation are persistent features although exact details of the fronts and their times of formation and breakdown show a large interannual variability model results also reveal a patch of thermal stratification in the northern part of the eastern irish sea with northward thermal density driven currents in this region

influence of a cold water bottom dome on internal wave trapping 1 a numerical model of a cross section through a cold water bottom dome is used to examine the influence of wind forcing frequency dome length and density field upon the variability of internal waves in the region forcing at super inertial frequencies produces internal waves in the frontal regions that propagate into the centre of the dome producing a standing wave the wavelength of the internal wave depends upon water depth forcing frequency and stratification at the edges of the dome internal waves are trapped by the bottom fronts at sub inertial forcing waves are trapped close to the dome s boundary giving different mixing to that found with super inertial forcing these calculations suggest significant differences in internal wave spectra in domes compared with open sea observations these spectral differences would be a critical test of the model s dynamics

trapped near inertial waves and enhanced chlorophyll distributions waves with near inertial frequencies were observed along a front associated with a large mesoscale feature in the sargasso sea during the late summer of 1987 high subsurface chlorophyll concentrations occurred on the edge of this front coincident with the wave packets the amplitude of the waves increased with time and kinetic energy propagated downward reducing 20 m richardson numbers in the thermocline to 1 or less chlorophyll levels were episodic showing no periodicity coincident with wave dynamics however on two occasions chlorophyll concentration increased from 1 mg chl m 3 several hours after the waves penetrated the thermocline it was hypothesized that mixing associated with shear instabilities stimulated new production a diffusivity model combined with nutrient data produced a phytoplankton bloom that accounted for only one of the maxima the other increase in chlorophyll may have been the result of horizontal advection of the wave packets near the front

forced ocean response during the frontal air sea interaction experiment a central hypothesis of the frontal air sea interaction experiment fasinex was that the strong gradients in the upper ocean associated with ocean fronts would spatially modulate the response of the ocean to local atmospheric forcing to test this hypothesis measurements of near surface meteorology and upper ocean variability were made for 5 months from an array of moorings and for one of those 5 months from two ships a number of fronts passed through the moored array and the moored meteorological and current meter data were used to examine the response of the upper ocean to atmospheric forcing at subinertial and near inertial frequencies at low frequencies an ekmanlike frictionally driven component in the mixed layer and a more deeply penetrating component thought to be forced by ekman pumping were found strong near inertial response was found in the mixed layer the near inertial motion showed considerable spatial variability in the seasonal thermocline here it was evident that the structure of the front influenced the downward propagating near inertial internal waves data were also obtained by profiling instruments deployed along cross frontal sections these data were used to examine the spatial and temporal variability of the internal waves microstructure and dissipation and the relation of that variability to oceanic fronts and atmospheric events the spectral densities of the components of the internal waves that rotated clockwise with increasing depth were higher in regions of negative relative vorticity than those predicted by garrett and munk munk 1981 and estimates of clockwise and total shear were highest in regions of negative relative vorticity in the strong shear of the ocean front significant anisotropy of the internal wave field was observed and kinetic energy dissipation levels relative to the rate of work by the wind were higher than previously reported

strong inertial currents and marginal internal wave stability in the central north sea solar insolation stabilizes the water column and suppresses vertical exchange observations from the central north sea clearly show that increased heating in summer is accompanied by enhanced de stabilizing vertical current differences shear surprisingly to such extent that the equilibrium state is marginally stable under calm weather conditions the shear is predominantly generated by near inertial motions while the internal wave spectrum primarily results from nonlinear interaction between the dominating tidal and near inertial motions in terms of the associated enhanced vertical mixing across the largest vertical temperature gradients shelf seas are not different from the abyssal ocean despite the proximity to energy sources near boundaries in the former by the lack of sufficiently strong wind and tidal mixing this internal mixing is considered to be responsible for the diapycnal transport of nutrients leading to the observed increase in near surface values and triggering the late summer phytoplankton bloom

progressive rollover fault propagation folding a possible kinematic mechanism to generate regional scale recumbent folds in shallow foreland belts the occurrence of strongly overturned to recumbent anticlines in shallow foreland thrust fold belts is not well explained by the available geometric models of thrust related folding when a very large amount of forward shear cannot be assumed and for growth anticlines when the tectonic uplift rate is greater than the sedimentation rate we have developed new geometries for fault propagation folding progressive rollover fault propagation folding that are suitable for overcoming these problems in our configuration an outer right way up sector and an overturned sector can grow simultaneously in the forelimb of the tip anticline they are linked to a recumbent leading syncline a semiquantitative computation of fracture strain during folding allowed us to define six homo eneously strained rock panels the location of the most strained panels suggests that an anticlinal breakthrough or a synclinal breakthrough is likely to affect the structure later in its evolution the outer morphology of the tip anticline in progressive rollover fault propagation folding resembles a fault bend fold this model produces geometries suitable for hydrocarbon trapping

strain patterns and shortening in a folded thrust sheet an example from the southern appalachians abstract total strain patterns estimated across the pulaski thrust sheet of the southwest virginia appalachians show an approximately homogeneous plane strain deformation associated with folding and distortion above a subsurface decollement estimated strains are low 1 2 x z

the effect of a bottom shelf front upon the generation and propagation of near inertial internal waves in the coastal ocean abstract a three dimensional nonlinear baroclinic model in cross sectional form is used to study the generation and propagation of wind forced near inertial internal waves in a coastal region in the presence of a bottom front initially calculations are performed with the front in an infinite domain region by this means coastal effects are removed the initial response is in terms of inertial oscillations in the surface layer however in the frontal area these are modified by interaction through the nonlinear momentum terms with regions of positive and negative vorticity associated with the alongfront flow this leads to a change in amplitude phase and frequency of the inertial current and a resulting ekman pumping that drives near inertial internal waves in the frontal region on the positive vorticity side of the front these waves are at the superinertial frequency and rapidly propagate away on the negative side they are at the subinertial frequency and are trapped and inertial energy leaks to dep

processes influencing the non linear interaction between inertial oscillations near inertial internal waves and internal tides 1 a numerical model of the hebrides shelf edge represented by a cross section is used to examine the non linear interactions producing energy at the fm2 frequency calculations show that in the near coastal ocean this is primarily due to coupling between wind induced inertial oscillations although near inertial internal waves are present and the m2 internal tide the major non linear interaction and hence largest fm2 currents occurs in the region of the thermocline and is associated with shear in the inertial oscillation and the vertical velocity due to the internal tide this non linear process represents an important contribution to the energy cascade from the wind and tide into higher frequency waves and eventually mixing the fm2 current is shown to be a maximum in the shelf edge region and hence measurements in this area will be particularly valuable in determining the extent to which models can represent non linear processes

the relation of near inertial motions observed in the mixed layer during the jasin 1978 experiment to the local wind stress and to the quasi geostrophic flow field abstract oscillations with near inertial frequencies were an energetic component of the upper ocean velocity field observed at each of two moorings separated by 44 km during the joint air sea interaction jasin experiment during the late summer of 1978 at each mooring the amplitude of the inertial motion was highest in the mixed layer where it was nearly depth independent previous work pollard and millard 1970 pollard 1980 had found that the amplitude and phase of inertial motion in the mixed layer was related to the local wind stress in this case the loacal winds measured at each mooring were coherent but the time series of mixed layer near inertial motion at one mooring bore little resemblance to that at the other mooring during jasin 1978 the differences in the inertial response at the two moorings coincided with differences in the quasi geostrophic flow field in the vicinity of the two moorings inclusion of the horizontal gradients of the quasi geostrophic flow in model equations prov

observations of near inertial surface currents off oregon decorrelation time and length scales 1 high resolution km in space and hourly in time surface currents observed by an array of high frequency radars off oregon are analyzed to quantify the decorrelation time and length scales of their near inertial motions the near inertial surface currents are dominantly clockwise with amplitudes of 9 12 cm s 1 however they appear asymmetric and elliptical as a result of counterclockwise inertial motions with magnitudes in a range of 2 5 cm s 1 the decorrelation time and length scales are computed from the decay slope of the near inertial peak and the spatial coherence in the near inertial frequency band respectively decorrelation time scales of clockwise near inertial motions increase from 2 days nearshore within 30 km from the coast to 6 days offshore and their length scales increase from 30 to 90 km seaward possibly due to coastal inhibition the local spatial coherence has an exponentially decaying structure for both clockwise and counterclockwise rotations and their phases propagate northwestward offshore for clockwise and northeastward onshore for counterclockwise rotations

scour below marine pipelines in shoaling conditions for random waves abstract this paper provides an approach by which the scour depth below pipelines in shoaling conditions beneath non breaking and breaking random waves can be derived here the scour depth formula in shoaling conditions for regular non breaking and breaking waves with normal incidence to the pipeline presented by cevik and yuksel cevik e and yuksel y 1999 scour under submarine pipelines in waves in shoaling conditions asce j waterw port coast ocean eng 125 1 9 19 combined with the wave height distribution including shoaling and breaking waves presented by mendez et al mendez f j losada i j and medina r 2004 transformation model of wave height distribution on planar beaches coast eng 50 3 97 115 are used moreover the approach is based on describing the wave motion as a stationary gaussian narrow band random process an example of calculation is also presented

sequential restoration and unstraining of structural cross sections applications to extensional terranes we restore cross sections using a strain minimization strategy that concentrates displacement on known faults and on slip systems within fault blocks growth strata are used to sequentially restore cross sections and the misfit of rigidly restored fault blocks is used to determine the internal strain within each fault block texture mapping allows data e g seismic profile photograph of an analog model or outcrop to be imaged onto the restored state and the image is translated rotated and unstrained during the restoration growth strata are stripped layer by layer to sequentially restore a cross section this approach determines the history of deformation including the activity of faults and the internal strain accumulated during each growth increment during each increment of growth a cross section is initially restored to a horizontal datum assuming that deformation is by rigid body translations and rotations of fault blocks fault blocks are unstrained by dividing them into smaller triangular elements that accommodate the internal deformation within each fault block translations and rotations of the smaller rigid elements within each fault block produce a least squares minimized best fit after attaining a best fit of rigid elements continuity is regained by moving initially coincident triangle vertices to a common centroid the change in shape of the triangular elements in regaining continuity is a measure of strain at that location assuming homogeneous strain within each triangular element sequential restoration and unstraining determines the spatial variation and temporal evolution of strain orientations and magnitudes calculated at each vertex during each increment of restoration the method is tested on an analog sandbox model of deformation in the hanging wall of a listric normal fault and on two seismic profiles a listric normal fault system from the gulf of mexico and a graben developed over salt from the north sea the sequential restoration accurately determines the sequence of faulting in the analog model and provides insights into the development of the natural examples the restoration method determines the orientations and magnitudes of strain which can be used to predict the orientation intensity and timing of small scale deformation features

influence of coastal fronts on near inertial internal waves 1 a numerical model with a coastal boundary and near shore surface or bottom front is used to examine the role of the coast and front upon the generation and propagation of wind induced near inertial internal waves when stratification extends to the coast near inertial internal waves are produced at the coastal boundary however when the near shore region is well mixed the source of near inertial internal wave production is the front near inertial internal waves generated on the positive vorticity side of the front propagate away in the horizontal those generated on the negative vorticity side are trapped although some vertical propagation occurs when a coastal boundary is included significant inertial currents are found at depth phase shifted by 180 from the surface this goes some way to explain the recent observed distributions of inertial energy found in near coastal measurements

a fine resolution numerical model of the iceland farœ front with open boundary conditions an eddy resolving limited area primitive equation model of the iceland far frontal region is developed the spatial and temporal evolution of the front is examined on time scales of up to 2 months experiments are performed changing the open boundary conditions at the lateral boundaries using passive and active open boundary conditions the experiment with the passive open boundary conditions reproduces many observed features of the iceland far frontal region discrepancies between these results and observations in the area are noted in particular the western end of the front drifts too far north the model is then forced at the lateral boundaries using two contrasting barotropic velocity fields improvements in the results are noted comparison of the results illustrate to what extent and how far field currents can affect the dynamics of this frontal region the east icelandic current is found to have the following important effect on the front maintaining its vertical structure and confining the western end of the front to more southerly latitudes

interaction of superinertial waves with submesoscale cyclonic filaments in the north wall of the gulf stream abstracthigh resolution nearly lagrangian observations of velocity and density made in the north wall of the gulf stream reveal banded shear structures characteristic of near inertial waves niws here the current follows submesoscale dynamics with rossby and richardson numbers near one and the vertical vorticity is positive this allows for a unique analysis of the interaction of niws with a submesoscale current dominated by cyclonic as opposed to anticyclonic vorticity rotary spectra reveal that the vertical shear vector rotates primarily clockwise with depth and with time at frequencies near and above the local coriolis frequency f at some depths more than half of the measured shear variance is explained by clockwise rotary motions with frequencies between f and 1 7f the dominant superinertial frequencies are consistent with those inferred from a dispersion relation for niws in submesoscale currents that depends on the observed aspect ratio of the wave shear as well as the vertical vorticity

wind induced motion in the vicinity of a bottom density front response to forcing frequency 1 a numerical model is used to examine the influence of nonlinear processes in the vicinity of a shallow sea bottom density front upon the depth of penetration of the wind s momentum at both superinertial and subinertial frequencies calculations show that nonlinear effects associated with differences in vorticity across the frontal jet significantly influence the depth of penetration of the wind s momentum and internal wave propagation differences in wind induced current amplitude and phase at depth due to nonlinear effects give rise to substantial vertical velocity in the frontal region which drives near bed currents and forces internal waves at superinertial frequencies internal waves propagate away from the positive vorticity side of the front however at depth internal waves are generated and current amplitude increases in the region of sloping density surfaces associated with the front on the negative vorticity side due to an effective inertial frequency below inertial the wind s energy can propagate deeper into the water column wind forcing at subinertial frequencies does not lead to internal wave propagation on the positive vorticity side of the front the wind s momentum cannot diffuse to depth due to turbulence suppression by stable stratification the ability of the wind s momentum to penetrate to a greater depth in a frontal region through nonlinear effects suggests that these may be important processes influencing wind mixing in frontal regions

space time scales of shear in the north pacific abstractthe spatial temporal and directional characteristics of shear are examined in the upper 1400 m of the north pacific during late spring with an array of five profiling moorings deployed from 25 to 37 n 1330 km and simultaneous shipboard transects past them the array extended from a regime of moderate wind generation at the north to south of the critical latitude 28 8 n where parametric subharmonic instability psi can transfer energy from semidiurnal tides to near inertial motions analyses are done in an isopycnal following frame to minimize contamination by doppler shifting approximately 60 of rms shear at vertical scales 20m and 80 for vertical scales 80 m is contained in near inertial motions an inertial back rotation technique is used to index shipboard observations to a common time and to compute integral time scales of the shear layers persistence times are o 7 days at most moorings but o 25 days at the critical latitude simultaneous shipboard transects show that these sh

strain fabric associated with the meade thrust sheet implications for cross section balancing abstract emplacement of the meade thrust sheet southeastern idaho u s a was accompanied by the development of a strain fabric and significant footwall deformation characteristics of the strain fabric are based on strain estimates using pressure solution cleavage and deformed fossils within the jurassic twin creek formation the strain fabric formed during early layer parallel shortening at the thrust front and accommodates from 10 to 35 shortening within the incipient thrust sheet footwall strata were later folded above a detachment at the base of the twin creek formation and the early strain fabric was passively rotated the structural development of this area consisting of 1 strain fabric development 2 folding of the footwall and 3 the truncation of footwall structures by imbricates of the meade thrust are placed in a relative time frame to aid in section reconstruction the passive reorientation of the strain fabric and the truncation and incorporation of footwall structures into the thrust sheet are used as kinematic and geometric constraints for cross section balancing we present a sequential retrodeformation of the meade thrust sheet in which strain is removed from the cross section at the appropriate geometric stages in the deformation these sections illustrate some methods by which strain data can be incorporated into cross sections and also indicate the difficulty involved in balancing cross sections of internally deformed thrust sheets interpretation of these sections suggests that a significant amount of footwall deformation accompanied the emplacement of the meade thrust sheet and that footwall deformation is strongly controlled by the local stratigraphic package the sections also illustrate that the earliest deformation within a thrust sheet may be unrelated to motion on the underlying incipient thrust and that the trace of a thrust fault which cuts previously deformed strata will not restore to a typical ramp and flat geometry

observation of tropical cyclone induced shallow water currents in taiwan strait the data from three stations equipped with acoustic doppler current profilers adcps deployed in the shallow water of the taiwan strait tws were used to study the shallow coastal ocean response to five quasi continuous tropical cyclone tc events in the late summer 2006 we revealed that in the forced stage when the large and strong tc bilis transited the geostrophic currents were formed which dominated the whole event while the strong but relatively small one saomai or the weak one bopha primarily leaded to the generation of ekman currents in the relaxation stage the barotropic subinertial waves and or the baroclinic near inertial oscillations nios were triggered typically during the transit of the saomai subinertial waves were induced which demonstrated a period of 2 8 4 1 days and a mean alongshore phase velocity of 14 9 3 2 m s in the form of free barotropic continental shelf waves however the nios are only notable in the area in which the water column is stably stratified and also where the wind stress is dominated by the clockwise component and accompanied by high frequency near inertial variations we also demonstrated that due to the damping effects the nonlinear wave wave interaction e g between nio and semidiurnal tide in our case together with the well known bottom friction led to the rapid decay of the observed tc induced near inertial currents giving a typical e folding time scale of 1 3 inertial periods moreover such nonlinear wave wave interaction was even found to play a major role during the spring tide in tws

one dimensional ocean surface layer modeling a problem and a solution abstract the first part of this paper is generic it demonstrates a problem associated with one dimensional ocean surface layer model comparisons with ocean observations unlike three dimensional simulations or the real ocean kinetic energy can inexorably build up in one dimensional simulations which artificially enhances mixing adding a sink term to the momentum equations counteracts this behavior the sink term is a surrogate for energy divergence available to three dimensional models but not to one dimensional models the remainder of the paper deals with the mellor yamada boundary layer model there exists prior evidence that the model s summertime surface temperatures are too warm due to overly shallow mixed layer depths if one adds a sink term to approximate three dimensional model behavior the warming problem is exacerbated creating added incentive to seek an appropriate model change guided by laboratory data a richardson number dependent dissipation is introduced and this simple modificat

the velocity structure of the upper ocean in the presence of surface forcing and mesoscale oceanic eddies one goal of the joint air sea interaction experiment jasin was to investigate the structure of the near surface velocity field and to attempt to quantify what fraction of that field was related to the local wind toward that end in the late summer of 1978 two moorings were deployed in the northern rockall trough with oceanographic instrumentation concentrated in the upper 100m of the ocean simultaneous observations were made of the surface winds at each mooring and adjacent to one of the moorings of the velocity field at depths from 79 to 1000m energetic eddy like circulation dominated the velocity field in the jasin area at depths shallower than approximately 800m however both the velocity and the vertical shear of horizontal velocity showed variability that increased with proximity to the surface empirical orthogonal functions computed to separate the velocity data into uncorrelated modes of variability showed that over 97 of the variability in the upper 300m was distributed among only three vertical modes the first function had little depth dependence the second had strong depth independent flow in the depth range of the mixed layer and weak flow in the opposite direction at all depths below and the third had strong flow near the surface strong flow in the opposite direction just below the base of the mixed layer and weaker flow at all other depths function 1 alone provided a near complete description of the velocity variability below 85m where the flows associated with the eddy like circulation and the barotropic semidiurnal tide were the dominant components at 85m and above all three functions were necessary to provide a complete description temporal variability of function 2 was coherent with the local wind stress at the inertial frequency but at lower frequencies resulted in transport in the mixed layer to the southeast that was not coherent with the local wind low frequency temporal variability of function 3 was coherent with the local wind stress at these frequencies the velocity vector of function 3 nearest the surface was directed to the right of the wind stress vector and the velocity vector just below the base of the mixed layer was directed to the left of the wind stress thus forcing by the local wind can account for some but not all of the increased variability found near the surface

horizontal variability of near inertial oscillations associated with the passage of a typhoon 1 surface currents to the east of okinawa island were observed by using hf high frequency ocean radars in august september 1995 during that period a typhoon passed near the observation area and the horizontal variability of near inertial oscillations associated with the typhoon passage was estimated in addition the near inertial amplitudes and horizontal wave number vectors were estimated these estimations showed that the near inertial amplitude was large in the offshore area and small near the coast the maximum near inertial wavelength was estimated to be in the order of 1000 km and the near inertial wave direction was southward and changed to northwestward on 23 august in 1995 a slab model incorporating low frequency currents was used to calculate near inertial currents it was found that the amplitude of calculated near inertial oscillations was also large in the offshore area moreover the phase propagation direction of the near inertial waves was southward and changed to northwestward or westward on 22 august the growth rate obtained from the dispersion relation was large in the offshore area where the near inertial amplitude was large

predicting strain using forward modelling of restored cross sections application to rollover anticlines over listric normal faults a strategy to predict strain across geological structures based on previous techniques is modified and evaluated and a practical application is shown the technique which employs cross section restoration combined with kinematic forward modelling consists of restoring a section placing circular strain markers on different domains of the restoration and forward modelling the restored section with strain markers until the present day stage is reached the restoration algorithm employed must be also used to forward model the structure the ellipses in the forward modelled section allow determining the strain state of the structure and may indirectly predict orientation and distribution of minor structures such as small scale fractures the forward model may be frozen at different time steps different growth stages allowing prediction of both spatial and temporal variation of strain the method is evaluated through its application to two stages of a clay experiment that includes strain markers and its geometry and deformation history are well documented providing a strong control on the results to demonstrate the method s potential it is successfully applied to a depth converted seismic profile in the central sumatra basin indonesia this allowed us to gain insight into the deformation undergone by rollover anticlines over listric normal faults

tidally driven vorticity diurnal shear and turbulence atop fieberling seamount abstract fine and microstructure profiles collected over fieberling seamount at 32 26 n in the eastern north pacific reveal a variety of intensified baroclinic motions driven by astronomical diurnal tides the forced response consists of three phenomena coexisting in a layer 200 m thick above the summit plain i an anticyclonic vortex cap of core relative vorticity 0 5f ii diurnal fluctuations of 15 cm s 1 amplitude and 200 m vertical wavelength and iii turbulence levels corresponding to an eddy diffusivity e 10 10 4 m2 s 1 the vortex cannot be explained by taylor proudman dynamics because of its 0 3fn2 negative potential vorticity anomaly the 0 3f fortnightly cycle in the vortex s strength suggests that it is at least partially maintained against dissipative erosion by tidal rectification the diurnal motions are slightly subinertial turning clockwise in time and counterclockwise with depth over the summit plain they also exhibit a fortnightly cycle in their amplitude pointing to

model studies of near inertial motion on the continental shelf off northeast spain a three dimensional two dimensional one dimensional model comparison study 1 a three dimensional nonlinear model of the balearic sea region is used to examine the spatial distribution of wind induced near inertial internal waves results from the model are compared with those from two dimensional cross section and single point models in the case of motion induced by a wind pulse there is no significant along shelf flow and comparable solutions are obtained from the three and two dimensional models however when forced with a realistic wind a significant along shelf flow is produced that is larger in the cross section model than in the three dimensional model because of the absence of an along shelf pressure gradient associated with this change in flow are important differences in across shelf currents and temperature fields that influence the distribution of near inertial motion since the point model cannot take account of internal pressure gradients near inertial internal waves are absent however when some account of barotropic pressure gradients related to local wind stress are included currents and inertial oscillations were in better agreement with the three dimensional model than with the cross section model although the major features of the wind induced deepening of the thermocline could be reproduced by the single point model the absence of internal waves and mixing associated with them lead to a sharper thermocline than in the three dimensional model comparison of two and one dimensional models with the full three dimensional model shows some severe limitations in the simpler models

on the behavior of internal waves in the wakes of storms abstract the rossby adjustment process in the wake of a storm is studied with a view to finding within the context of linear theory how wave dispersion in both the vertical and meridional directions spreads energy which is initially confined entirely to the mixed layer comparisons are made between three cases 1 a periodic storm on the f plane where dispersion is purely vertical 2 a bounded storm on the f plane and 3 a bounded storm centered 2700 km from the equator on an equatorial beta plane particular attention is paid to the initial rate of loss of energy from the mixed layer and some simple formulas which work very well in the cases studied are derived these show that the rate of loss goes up when the mixed layer depth is increased and also that the rate scales as the square of the wavenumber values of the rates are sufficient to provide a major source of energy for internal waves below the mixed layer the often observed tendency for phase lines to propagate upward is found in all case

inertial oscillations on the continental shelf of the gulf of lions observations and theory abstract observations in the gulf of lions northwestern mediterranean sea in summer have shown that gusts of wind lasting a few days generate transient upwellings and inertial motions oscillations at the inertial frequency were observed in current meter data near the shore and at a frequency 10 greater in the temperature data vertical coherences in current meter data show a strong baroclinic mode at frequencies greater than inertial frequency a simple one dimensional two layer transient model suggests that these motions are associated with two different physical processes the first process describes the local response of the ocean to meteorological forcing the second is associated with the propagation of long internal waves generated in the transient phase of the geostrophic adjustment process as suggested by the model the direction of propagation of the internal waves is computed from current and temperature data measured at one point and it is found that the shore is the source zone

continuous restoration of deformed shapes through the construction of a reverse displacement gradient and its application to granite emplacement in central north china this paper presents a new technique to restore 2d 3d deformed shapes by minimization of the misfit between measured and theoretical reverse displacement gradients owing to its relatively direct and objective nature the procedure ensures continuity of displacement across the boundaries between abutting elements the procedure also minimizes the additional distortion of the elements that results from the compatibility of retro deformation between abutting elements we apply the technique to the mesozoic fangshan granodioritic pluton fgp in western beijing central north china based upon the measured strain of deformed enclaves about 78 area of the present central zone can be restored by retro deformation of the marginal and transitional zones as a result of the emplacement of the central zone deformation also occurred in both the outer zones and the wall rocks predominantly by ductile flow the associated deformation in the outer zones with or without the involvement of the wall rocks created space for the emplacement of the central zone in addition vertical expansion was effective in creating space for subsequent emplacement producing approximately one third of the volume created by later expansion thus ballooning is a viable mechanism for emplacement of the fgp

including strain data in balanced cross sections abstract almost all published balanced cross sections include cleaved and or strained rocks and may therefore violate the requirement that bed lengths and formation areas are preserved between undeformed and deformed states knowledge of distortions presence and type of cleavage and overprinting relations in poly deformed segments are necessary to define area changes related to volume loss strike elongation and poly deformation work in the southern and central appalachians has shown variation in structural complexity and changing deformation styles both along and across the thrust belt this necessitates separate treatment of individual sheets during balancing regions of little or no interstratal slip pinning points should be chosen for each thrust sheet and each fold strain in the sheet in external sheets where deformation intensity increases towards thrusts pin points should be back limb inflection points in intermediate and internal sheets where cleavage is approximately coeval with folding pin points should be at fold hinges where cleavage and strain are heterogeneously developed throughout a stratigraphic sequence a line length balance using massive relatively uncleaved beds e g knox group southern appalachians can be used as a basis for restoring the section unstraining of deformed layers given strain data and cleavage trajectories for individual thrust sheets provides line lengths and formation areas which can be fitted to the key bed of the undeformed section cleavages which partially or fully postdate folding indicate continued shortening in the thrust wedge and modify earlier pinning points in upper sheets these cleavages and poly deformed segments are difficult to restore as strain data are generally scarce in the metamorphosed internal thrust sheets

new chemical bio optical and physical observations of upper ocean response to the passage of a mesoscale eddy off bermuda a mesoscale eddy advected across the bermuda testbed mooring site over a 30 day period centered on july 14 1995 temperature and current measurements along with biogeochemical measurements were used to characterize the biological response of the upper ocean associated with the introduction of nitrate into the euphotic layer due to the doming of isotherms associated with the eddy complementary shipboard data showed an anomalous water mass which extended from a depth of 50 to 1000 m manifesting as a cold surface expression and warm anomaly at depth although mesoscale eddies are frequently observed in the sargasso sea the present observations are particularly unique because of the high temporal resolution measurements of the new instrumentation deployed on the mooring analyzers that measure nitrate plus nitrite were placed at depths of 80 and 200 m and bio optical sensors were located at depths of 20 35 45 71 and 86 m peak nitrate values of nearly 3 0 mm at 80 m and chlorophyll a values of 1 4 mg m 23 at 71 m were observed as well as a 25 to 30 meter shoaling of the 1 light level depth a doppler shift from the inertial period 22 8 hours to 25 2 hours was observed in several time series records due to the movement of the eddy across the mooring inertial pumping brought cold nutrient rich waters farther into the euphotic zone than would occur solely by isothermal lifting silicic acid was depleted to undetectable levels owing to the growth of diatoms within the eddy the chlorophyll a values associated with the eddy appear to be the largest recorded during the 8 years of the ongoing u s jgofs bermuda atlantic time series study bats program

vorticity balance off the south shore of oahu hawaii derived by high frequency radio doppler current observations abstracthigh frequency radio doppler surface current observations off the south shore of oahu hawaii are used to calculate the vorticity equation at a 2 km spatial resolution in terms of a time

deriving inertial wave characteristics from surface drifter velocities frequency variability in the tropical pacific two techniques have been developed for estimating statistics of inertial oscillations from satellite tracked drifters these techniques overcome the difficulties inherent in estimating such statistics from data dependent upon space coordinates that are a function of time application of these techniques to tropical surface drifter data collected during the norpax epocs and toga programs reveals a latitude dependent statistically significant blue shift of inertial wave frequency the latitudinal dependence of the blue shift is similar to predictions based on global internal wave spectral models with a superposition of frequency shifting due to modification of the effective local inertial frequency by the presence of strongly sheared zonal mean currents within 12 of the equator

tidal currents in the northwestern adriatic high frequency radio observations and numerical model predictions the results of a two year long deployment of high frequency radars along the italian coast of the northern adriatic are analyzed to characterize the surface tidal currents m2 and k1 ellipses are aligned with the basin axis and exhibit large eccentricities in the middle of the basin decreasing toward the italian coast comparisons are made with a 3d finite element non linear numerical model of the tides complex correlations between modeled and observed tidal currents show a remarkable agreement in the middle of the basin with magnitudes reaching 0 985 and average phases of 6 4 deg however the magnitudes drop to 0 5 within 20 30 km from the italian coast where the modeled currents amplitudes are underestimated by 2cm s and the phases lag the observed phases by 60 deg this shallow region less than 30 m deep is characterized by low salinity water originating at the po river and laterally sheared coastal flows the radars may have captured the influence of stratification or mean sheared flows both absent from the model the model parameterization of bottom friction may also inadequately represent the effects of real bottom friction on the vertical current shear

inertial oscillations in the korea strait inertial oscillations io are examined in the korea strait based on measurements from 13 acoustic doppler current profilers covering the time period may 1999 through march 2000 strong io responses to wind stress occur during summer a simple linear model predicts that winter wind stress is expected to generate inertial responses of the same order of magnitude as those in summer however the observed winter io response is much weaker than predicted during summer the currents within the mixed layer and below the mixed layer are of comparable amplitude but in opposite directions the depth at which the currents reverse directions varies throughout the year as the mixed layer deepens from about 40 m during summer to the bottom of the water column in november during winter the velocity structure is more uniform in depth with currents in the same direction throughout the water column one possible explanation for these phenomena is related to the combined effect of the strait boundaries and the strong summer stratification the stratification prevents the wind stress momentum flux from mixing downward below the thermocline and thus allows the development of a bottom current separate from the surface current such a velocity structure is necessary to satisfy the no flow condition through the land boundaries

drifting buoy in the field of flow of two eddies on east thulean rise northeast atlantic the track of an argos buoy drogued at a depth of 70 m over a year s deployment from april 18 1989 to april 18 1990 in the ne atlantic is described the mean speed of the buoy over a year s period was 1 4 cm s 1 to the ne for 320 days there was little net movement and during this time the buoy spent 66 days in a cyclonic eddy and 130 days in an anticyclonic eddy the anticyclonic eddy diameter was about 200 km and the buoy completed 21 complete revolutions around the eddy center at a radius of 55 km the rotation rate was 10 days in the eye of the anticyclonic eddy the rotation rate was 36 hours the inertial period for the latitude 51 5 n was 15 3 hours and inertial motions were occasionally marked in the anticyclonic eddy the observed inertial period was about half an hour longer than the inertial period corresponding to the latitude both eddies appeared to be partially trapped to east thulean rise water depth 3000 m and moved at a mean speed of about 1 cm s 1 to the nw along the rise following water depth contours though the anticyclonic eddy was stationary for about 50 days over the more central region of the rise the track of an imperfectly drogued buoy in a circular eddy field is then examined analytically a simple balance of stress forces on the drogued assembly is assumed and commonly adopted assumptions for the stress forces are made with assumptions the idealized study shows that under conditions of a steady surface stress a surface wind or current for example a buoy can remain trapped within an eddy field and show no tendency for steady translation in the direction of the surface stress for a clockwise eddy the displacement of the buoy s track is to the right of the surface stress direction for larger surface stresses or time varying winds the buoy may be blown out of an eddy of limited extent

impact of nonlinear waves on the dissipation of internal tidal energy at a shelf break the vertical and temporal structure of the dissipation of turbulent kinetic energy within the internal tide at a location 5 km shoreward of the shelf break on the malin shelf has been determined using a combination of the free falling light yo yo profiler and acoustic doppler current profilers two distinct internal wave regimes were encountered period i in which large amplitude high frequency nonlinear internal waves niws occurred around neap tides and period ii in which the internal wave spectral continuum was not dominated by any particular frequency band around spring tides empirical orthogonal function analysis shows that for the low frequency waves 76 of the variance was described by mode 1 rising to 95 for the high frequency waves during period i the dissipation and vertical mixing were characterized by the niws and 70 of the dissipation occurred in the bottom boundary layer during period ii the depth integrated dissipation was more evenly distributed throughout the tidal cycle whereas vertical mixing was greatly enhanced during a single hour long episode of elevated thermocline dissipation coincident with weakened stratification during both periods i and ii 30 of the total measured dissipation occurred within the thermocline when averaged over 12 4 hours the remainder occurred within the bottom boundary layer bbl tidal average values for depth integrated dissipation and vertical eddy diffusivity for period i ii were 1 1 10 2 w m 2 4 0 10 2 w m 2 and 5 cm2 s 1 12 cm2 s 1 respectively decay rates and internal damping are discussed and vertical heat fluxes are estimated observed dissipation rates are compared with a simple model for bbl dissipation

on the loss of wind induced near inertial energy to turbulent mixing in the upper ocean wind induced near inertial energy has been believed to be an important source for generating the ocean mixing required to maintain the global meridional overturning circulation in the present study the near inertial energy budget in a realistic 1 12 degrees model of the north atlantic ocean driven by synoptically varying wind forcing is examined the authors find that nearly 70 of the wind induced near inertial energy at the sea surface is lost to turbulent mixing within the top 200 m and hence is not available to generate diapycnal mixing at greater depth assuming this result can be extended to the global ocean it is estimated that the wind induced near inertial energy available for ocean mixing at depth is at most 0 1 tw this confirms a recent suggestion that the role of wind induced near inertial energy in sustaining the global overturning circulation might have been overemphasized

restoration of cross sections through unfaulted variably strained strata data on the dip of bedding and the state of strain at specific locations within a cross section constrain the restoration of unfaulted two dimensional variably strained strata there are two major categories for restoration of such strata the first is one step restoration which involves retro deforming the strain ellipses into their corresponding unit circles while simultaneously removing dips from associated beds this procedure is appropriate if strain indicators record the transformation of the strata from the undeformed state to present deformation the second category pertains to situations in which strain indicators record the transformation of the present deformed state from an intermediate deformed state the second category requires multiple step restoration for the one step restoration procedure presented in this paper the first task is to determine the transformation constants that describe development of observed strain and bedding for each location the next task is to determine the retro deformation constants which relate points in their present deformed state to their locations in the undeformed state retro deformation constants are related to the spatial derivatives of the cartesian retro deformation displacements functions u x y and v x y for movements in the x and y directions respectively the spatial derivatives of these functions at locations of observed strain and the displacements of selected points about these sites are the basis for constructing continuous retro deformation displacements functions for the deformed section as a whole the retro deformation displacements functions are then invoked to restore the cross section this procedure is illustrated with an example cross section from the appalachian fold belt and the example shows that the section may be satisfactorily restored in this way it is just as likely however that the strain indicators for the example section are a measure of the transformation of the cross section from a prior deformed state to the present deformation accordingly multiple step restoration is required first to an intermediate less deformed state and then to the undeformed state two sets of retro deformation displacement functions are then needed i e one set for transformation to an intermediate state followed by a second to the undeformed state this procedure was done for the appalachian fold thrust belt example restoring first the present deformed section to an intermediate state derived from the regional fold history in turn intermediate state points were transformed to an undeformed state assuming knowledge of an undeformed stratal thickness and assuming that cross sectional area has been preserved this procedure is technically different to that used in the one step procedure but conceptually similar the objective once again is to discover appropriate retro deformation displacements functions

burial and scour of short cylinders under combined random waves and currents including effects of second order wave asymmetry abstract this paper provides an approach by which the burial and scour of short cylinders under combined second order random waves and currents can be derived here the formulas for burial and scour for regular waves plus currents presented by catano lopera and garcia catano lopera y a and garcia m h 2006 burial of short cylinders induced by scour under combined waves and currents asce j waterway port coastal and ocean eng 132 6 439 449 catano lopera y a and garcia m h 2007 geometry of scour hole around and the influence of the angle of attack on the burial of finite cylinders under combined flows ocean eng 34 5 6 856 869 are used together with stokes second order wave theory by assuming the basic harmonic wave motion to be a stationary gaussian narrow band random process an example of calculation is also presented

evaluation analysis and prediction of geologic structures abstract balanced cross sections claim to be better because they apply a rigorous set of rules to develop the conceptual model of the structures present in an area balanced cross sections can be further improved and become more useful to understanding real physical problems by collection of additional data such as seismic reflection surveys collection of additional stratigraphic data or collection of rock fabric information the additional information validates the initial model and provides details on deformation conditions and on local rock responses to the deformation although individual cross sections are two dimensional the objective of evaluation and analysis of deformed regions should be three dimensional whenever possible to recognize the challenges of the real world subsurface system analysis derived from the hydrologic community emphasizes conceptual model development through model verification validation uncertainty quantification benchmarking and meta analysis their approach includes many steps informally used by the structural geology community but in a much more explicit way newer geological applications of structural geology would benefit from this more rigorous approach for designing and doing performance predictions as technological needs become more socially sensitive such as for carbon storage sites new areas of energy exploration in higher population density areas or for nuclear waste storage facilities

application of an unstructured mesh model to the determination of the baroclinic circulation of the irish sea 1 a three dimensional finite volume model with horizontally varying but fixed in time mesh is used to compute the baroclinic circulation of the irish sea during 1995 tidal forcing was applied along the model s open boundary with meteorological forcing taken from observations initial calculations were performed with a mesh that had high resolution in the well mixed near coastal region a necessary requirement in order to reproduce tides in the region although offshore in the stratified area the mesh was slightly coarser than that used in earlier finite difference models subsequent calculations were performed using an enhanced resolution which is significantly finer than earlier finite difference models in the offshore region which is thermally stratified in summer due to solar heating and low tidal mixing this produces a cold water bottom dome separated from the well mixed shallow water regions by strong tidal fronts calculations show that both model meshes can reproduce the observed major features of the baroclinic circulation of the western irish sea with the coarse mesh model giving comparable results to earlier finite difference models in the case of the finer mesh model there are sharper horizontal density gradients in the region of the fronts which show the presence of baroclinic instability and associated small scale variability as observed in satellite images but not found in the coarser mesh model due to lack of resolution results from the fine mesh model show significantly more spatial variability comparable to that found in the measurements

a shallow subtropical subducting westward propagating eddy swesty swesty is a shallow subtropical subducting westward propagating eddy that was observed to move across the eastern basin of the north atlantic at a latitude near 25 n the eddy was first detected by the movement and temperature of a drogued argos buoy near 23 w 26 n in february 1993 by december 1993 the drogued buoy had moved 1000 km westward to 33 w and a winter eddy survey was made from rrs charles darwin the eddy was about 100 km in diameter and had a centre water mass core at a depth of 190 m with characteristic temperature 19 9 c and salinity 37 06 psu but was best resolved by properties related to vertical gradient structure e g brunt vaisala frequency temperature perturbation structure the eddy was particularly flat with a height to width aspect ratio of only ca 0 14 and a vertical decay scale of ca 250 m for temperature displacements maximum azimuthal currents were ca 16 cm s 1 at a depth of 175 m and the eddy azimuthal transport was only 3 sv however the potential vorticity in the eddy core was 1 5 x 10 11 rad ms 1 comparable with other deep anticyclonic lenses and lower than background values by a factor of ten the eddy appeared slightly elliptical with a detectable sea surface cooling ca 0 2 c over its centre three argos buoys with drogues set at a depth of 200 m were deployed near the centre of the eddy and one buoy continued looping westward for a further ca 800 km the drogued argos buoy results showed that the eddy moved westward at ca 100 km month 1 and about half this westward rate was attributed to self propagation during this ca 1650 km continuously drogued journey the eddy only slipped southward by about one degree of latitude and so was perhaps resisting the southward component of flow of the subtropical gyre the buoy results suggested that the central rotation rate increased with time but the eddy became smaller the initial rotation period of the central core was ca 8 d giving a corresponding normalized relative vorticity of 0 3 about 400 d later the period of core rotation was ca 5 d with normalized relative vorticity of 0 5 some of the increase in central rotation rate was attributed to subduction effects variance spectra and filtered components of velocity were derived from the buoy positions kinetic energy levels in the eddy ca 73 cm 2 s 2 were markedly elevated with respect to background levels ca 29 cm 2 s 2 the core properties of the eddy indicated a winter formation near 27 n 22 w and hydrographic sections showed that the eddy would be sinking at a rate of about 40 m a 1 by the second year the subducted water parcel the eddy core was sufficiently deep below the surface of the ocean to escape further effects of winter mixing

the near surface dynamics of coastal upwelling abstract an attempt is made to examine some observational and theoretical aspects of upper ocean dynamics in regions of strong coastal upwelling upper ocean is roughly defined as about the upper 10 30 m of the water column for most systems first the basic surface ekman and mixed layers are discussed including some of the modifications due to upwelling next coastal upwelling fronts and their associated circulation are treated finally areas of strongly three dimensional upwelling are classified and discussed horizontal advection of heat and momentum appear to be generally important for the near surface dynamics of coastal upwelling and these phenomena make realistic theoretical treatments especially difficult

inertial oscillations in the upper ocean during the mixed layer dynamics experiment mildex surface currents in the near inertial frequency band were analyzed from 18 day long measurements taken in october november 1983 as part of the mixed layer dynamics experiment the currents below two drifting platforms separated by 55 km were found to have differed in their inertial response to a frontal passage on november 1 by 10 cm s 1 wind records from the two platforms were used to compute the predicted inertial currents with a simple slab model of the wind driven flow the model currents reproduced most of the features of the observed inertial currents including the disparity between the two locations following the november 1 frontal passage the disparity was due to differences in the weak winds preceding the frontal passage which account for inertial currents of 5 cm s 1 in opposing directions at the two platforms at the time of the front these differences or small scale 50 km structure in the wind field were responsible for the disparity rather than the slight difference in the arrival time 2 hours of the front at the two locations

mesoscale eddy internal wave coupling part i symmetry wave capture and results from the mid ocean dynamics experiment abstract vertical profiles of horizontal velocity obtained during the mid ocean dynamics experiment mode provided the first published estimates of the high vertical wavenumber structure of horizontal velocity the data were interpreted as being representative of the background internal wave field and thus despite some evidence of excess downward energy propagation associated with coherent near inertial features that was interpreted in terms of atmospheric generation these data provided the basis for a revision to the garrett and munk spectral model these data are reinterpreted through the lens of 30 years of research rather than representing the background wave field atmospheric generation or even near inertial wave trapping the coherent high wavenumber features are characteristic of internal wave capture in a mesoscale strain field wave capture represents a generalization of critical layer events for flows lacking the spatial symmetry inherent in a parallel shear flow or isolated vortex

three dimensional modal model of wind induced flow in a sea region abstract the solution of the linear three dimensional hydrodynamic equations describing wind induced flow in a sea region is developed using the galerkin method through the vertical a basis set of b splines is shown to have some computational advantages over a set of eigenfunctions vertical modes however a basis set of modes leads to a system of essentially uncoupled equations and current profiles can be interpreted in terms of vertical modes the influence of wind induced surface turbulence and turbulence at depth due to tidal motion upon current profiles in both deep 260 m and shallow 35 m sea regions is examined the variation in the angle between surface current and surface wind for different viscosity profiles and the effect of bottom friction upon it is considered the magnitude and direction of the surface current is significantly influenced by surface eddy viscosity however viscosity at depth due to tidal motion also has an important effect upon the surface current the time evolution of current structure following the sudden onset of a wind is examined using the modal model calculations show that the rate of damping of the internal modes is inversely proportional to the square of the depth consequently wind induced current structure takes longer to reach a steady state in a deep sea region than a shallow area the influence of sea surface elevation gradients in determining the direction of surface current is also considered

pencil structure and strain in weakly deformed mudstone and siltstone abstract weakly deformed mudstone and siltstone middle ordovician knobs formation of the appalachian valley and ridge province south western virginia u s a show strain dependent transitions between bedding fissility pencil structure and cleavage pencil structures are associated with a bulk inhomogeneous shortening deformation where minimum principal strain z ranges between 9 and 26 shortening assuming a plane strain and constant volume where strains are less bedding fissility dominates pencil fragments are defined by intersecting fracture sets subparallel to the pre existing bedding fissility and cleavage their long axes are both parallel to the bedding cleavage intersection and to the inferred y axis of the tectonic strain ellipsoid pencil development is considered to result from fracturing along both fabric anisotropies during weathering and post tectonic stress relaxation pencils show variations in size and shape depending on lithology grain size and composition degree of initial clay preferred orientation degree of cleavage development type of cleavage total bulk strain and degree of strain homogeneity their shape l w however is a direct measure of total y z strain since strain determinations from chlorite pressure fringes on framboidal pyrite within the pencil fragments give y z 0 913 0 019 l w pencil structure is therefore a potential strain marker in weakly deformed rocks

near inertial wave wake of hurricanes katrina and rita over mesoscale oceanic eddies abstract tropical cyclones tcs katrina and rita moved as major hurricanes over energetic geostrophic ocean features in the gulf of mexico increased and reduced oceanic mixed layer oml cooling was measured following the passage of both storms over cyclonic and anticyclonic geostrophic relative vorticity g respectively this contrasting thermal response is investigated here in terms of the evolution of the storms near inertial wave wake in geostrophic eddies observational data and ray tracing techniques in realistic geostrophic flow indicate that tc forced oml near inertial waves are trapped in regions of negative g where they rapidly propagate into the thermocline these anticyclonic rotating regimes coincided with the distribution of reduced oml cooling because rapid downward dispersion of near inertial energy reduced the amount of kinetic energy available to increase vertical shears at the oml base by contrast tc forced oml near inertial waves were stalled in upper layers of cyclonic circula

on the interaction between internal tides and wind induced near inertial currents at the shelf edge 1 numerical calculations are performed at the shelf edge to examine the role of nonlinear processes in transferring energy from the m2 tide and wind induced currents close to the inertial frequency f into a wave at the sum of their frequencies termed the fm2 frequency a numerical model of the hebrides shelf edge represented by a cross section initially with idealized topography and subsequently with realistic topography is used in these calculations results show that in the near coastal ocean currents at the fm2 frequency are primarily due to coupling between wind induced inertial oscillations and the m2 internal tide a major source is associated with vertical shear in the inertial oscillations and the vertical velocity due to the internal tide a secondary source is due to the nonlinear momentum advection term in the case in which eddy viscosity is computed from a turbulence energy model shear across the thermocline is larger than when a constant viscosity is used the reduction in shear with a constant viscosity reduces the role of the nonlinear term involving vertical shear and hence the magnitude of the fm2 current in the region of the thermocline increasing the wind stress leads to a deeper thermocline and hence the location of maximum fm2 current in the water column changing the vertical stratification influences the intensity of the inertial oscillations in the surface layer and the distribution of the internal tide and hence changes the pattern of fm2 currents results with realistic topography confirm the major conclusions

scour below pipelines and around vertical piles in random waves an approach by which the scour depth and scour width below a fixed pipeline and scour depth around a circular vertical pile in random waves can be derived is presented here the scour depth formulas by sumer and fredsoe asce j waterw port coastal ocean eng 116 1990 307 for pipelines and sumer et al asce j waterw port coastal ocean eng 114 1992 599 for vertical piles as well as the scour width formula by sumer and fredsoe the mechanics of scour in the marine environment world scientific singapore 2002 for pipelines combined with describing the waves as a stationary gaussian narrow band random process are used to derive the cumulative distribution functions of the scour depths and width comparisons are made between the present approach and random wave scour data tentative approaches to related random wave scour cases are also suggested

internal wave trapping and mixing in a cold water dome 1 a cross sectional nonlinear numerical model of a shallow sea basin containing a cold water dome is used to examine the influence of wind frequency and dome characteristics upon internal waves and mixing at superinertial forcing frequencies nonlinear effects in the frontal regions of the dome give rise to propagating internal waves which are reflected by the dome s fronts this reflection gives a standing internal wave trapped within the dome the spatial variability of the wave is determined by forcing frequency stratification and dome length the magnitude of the internal wave and the length of the dome are related to the horizontal distribution of density in the frontal region at the inertial frequency there is little internal wave propagation while at subinertial forcing frequencies the internal wave is trapped in the frontal region and energy cannot radiate away consequently vertical mixing is enhanced in the frontal regions while in the center of the dome the mixed layer increases due to the vertical diffusion of the wind s momentum to depth as in a single point model in the case of wind forcing at a superinertial frequency there is less mixing in the frontal region with internal wave propagation leading to mixing in the center of the dome these calculations suggest that the breakdown of cold water domes in response to winter wind events may be due to a number of mixing processes depending upon wind frequency

scour below submarine pipelines under irregular wave attack abstract submarine pipelines are widely used coastal structures and scour around them can influence their stability in this study scour around rigid submarine pipelines under normal incidence irregular wave attack on horizontal and 1 10 sloping beaches is studied this paper presents experimental results concerning scour under irregular wave attack multiple regression analysis is used to develop models to predict the scour depth under pipelines under the influence of irregular wave attack the representative wave parameters that characterize the irregular sea state that causes the same scour depth as regular wave attack were determined