earthquakes faulting and stress in the los angeles basin since 1920 fourteen moderate sized m l 4 9 6 4 earthquakes have been reported in the los angeles basin these events are associated with both mappable surficial faults and concealed faults beneath the basin sediments to determine the style of faulting and state of stress in the basin single event focal mechanisms for 244 earthquakes of m 2 5 that have occurred during 1977 1989 have been calculated fifty nine percent of the events are strike slip and are mostly located near two of the major northwest striking right lateral strike slip faults in the basin the newport inglewood fault and the palos verdes fault the 1988 pasadena and the 1988 upland earthquakes showed left lateral strike slip on northeast striking faults numerous small earthquakes in the eastern part of the basin show left lateral strike slip faulting and form a northeast trend near yorba linda thirty two percent of the events have reverse mechanisms and are distributed along two broad zones the first the elysian park fold and thrust belt coincides with anticlines along the eastern and northern flank of the los angeles basin extending into santa monica bay the second the torrance wilmington fold and thrust belt coincides with anticlines mapped on the southwest flank of the basin and extends from offshore newport beach to the northwest into santa monica bay oblique faulting that could be inferred by the merging of strike slip and compressional tectonics does not occur in the basin instead the coexistence of zones of thrusting and large strike slip faults in the basin suggests that the thrust and strike slip movements are mostly decoupled a few normal faulting mechanisms appear to be related to faulting orthogonal to the axes of plunging anticlines the trend of the maximum horizontal stress varies from n1 w to n31 e across the basin and consistently forms high angles with the fold axes the stress field that exists along the flanks of the basin has a vertical minimum stress axis this stress field and ongoing folding and thrusting suggest that tectonic deformation is concentrated along the flanks of the deep central basin today the deformation of the basin consists of uplift and crustal thickening and lateral block movement to accommodate the north south compression across the basin

quantifying upper ocean turbulence driven by surface waves 1 nearly all operational ocean models use air sea fluxes and the ocean shear and stratification to estimate upper ocean boundary layer mixing rates this approach implicitly parameterizes surface wave effects in terms of these inputs here we test this assumption using parallel experiments in a lake with small waves and in the open ocean with much bigger waves under the same wind stress and adjusting for buoyancy flux we find the mixed layer average turbulent vertical kinetic energy in the open ocean typically twice that in the lake the increase is consistent with models of langmuir turbulence in which the wave stokes drift and not wave breaking is the dominant mechanism by which waves energize turbulence in the mixed layer applying these same theories globally we find enhanced mixing and deeper mixed layers resulting from the inclusion of langmuir turbulence in the boundary layer parameterization especially in the southern ocean

directional wind wave coupling in fully coupled atmosphere wave ocean models results from cblast hurricane abstractthe extreme high winds intense rainfall large ocean waves and copious sea spray in hurricanes push the surface exchange parameters for temperature water vapor and momentum into untested regimes the coupled boundary layer air sea transfer cblast hurricane program is aimed at developing improved coupling parameterizations using the observations collected during the cblast hurricane field program for the next generation hurricane research prediction models hurricane induced surface waves that determine the surface stress are highly asymmetric which can affect storm structure and intensity significantly much of the stress is supported by waves in the wavelength range of 0 1 10 m which is the unresolved spectral tail in present wave models a directional wind wave coupling method is developed to include effects of directionality of the wind and waves in hurricanes the surface stress vector is calculated using the two dimensional wave spectra from a wave model with an added short wave s

directional spectra of hurricane generated waves in the gulf of mexico 1 hurricane induced directional wave spectra in the gulf of mexico are investigated based on the measurements collected at 12 buoys during 7 hurricane events in recent years focusing on hurricane generated wave spectra we only consider the wave measurements at the buoys within eight times the radius of the hurricane maximum wind speed rmax from the hurricane center a series of numerical experiments using a third generation spectral wave prediction model were carried out to gain insight into the mechanism controlling the directional and frequency distributions of hurricane wave energy it is found that hurricane wave spectra are almost swell dominated except for the right rear quadrant of a hurricane with respect to the forward direction where the local strong winds control the spectra despite the complexity of a hurricane wind field most of the spectra are mono modal similar to those under fetch limited unidirectional winds however bi modal spectra were also found in both measurements and model results four types of bi modal spectra have been observed type i happens far away 6 rmax from a hurricane type ii is bi modal in frequency with significant differences in direction it happens in the two left quadrants when the direction of hurricane winds deviates considerably from the swell direction type iii is bi modal in frequency in almost the same wave direction with two close peaks it occurs when the energy of locally generated wind sea is only partially transferred to the swell energy by non linear wave wave interactions type iv was observed in shallow waters owing to coastal effects

an asymptotic theory for the interaction of waves and currents in coastal waters a multi scale asymptotic theory is derived for the evolution and interaction of currents and surface gravity waves in water of finite depth under conditions typical of coastal shelf waters outside the surf zone the theory provides a practical and useful model with which wave current coupling may be explored without the necessity of resolving features of the flow on space and time scales of the primary gravity wave oscillations the essential nature of the dynamical interaction is currents modulating the slowly evolving phase of the wave field and waves providing both phase averaged forcing of long infra gravity waves and wave averaged vortex and bernoulli head forces and hydrostatic static set up for the low frequency current and sea level evolution equations analogous relations are derived for wave averaged material tracers and density stratification that include advection by horizontal stokes drift and by a vertical stokes pseudo velocity that is the incompressible companion to the horizontal stokes velocity illustrative solutions are analysed for the special case of depth independent currents and tracers associated with an incident surface wave field and a vortex with o 1 rossby number above continental shelf topography

hurricane directional wave spectrum spatial variation in the open ocean abstract the sea surface directional wave spectrum was measured for the first time in all quadrants of a hurricane s inner core over open water the nasa airborne scanning radar altimeter sra carried aboard one of the noaa wp 3d hurricane research aircraft at 1 5 km height acquired the open ocean data on 24 august 1998 when bonnie a large hurricane with 1 min sustained surface winds of nearly 50 m s 1 was about 400 km east of abaco island bahamas the noaa aircraft spent more than five hours within 180 km of the eye and made five eye penetrations grayscale coded images of hurricane bonnie wave topography include individual waves as high as 19 m peak to trough the dominant waves generally propagated at significant angles to the downwind direction at some positions three different wave fields of comparable energy crossed each other partitioning the sra directional wave spectra enabled determination of the characteristics of the various components of the hurricane wave field and mapping of their sp

deep flows in the yucatan channel and their relation to changes in the loop current extension 1 the first attempt to establish a relation between the loop current extension and deep flows in yucatan channel was made by maul et al 1985 it was unsuccessful probably because of the low spatial resolution of their observations from september 8 1999 to june 17 2000 eight moorings with acoustic doppler current profilers current meters and thermometers were deployed across the yucatan channel the data from these arrays were used to compute time series of the transports below the level of the deepest isotherm observed in the florida straits as required by a simple box model that restricts deep exchanges with the gulf of mexico to the yucatan channel the surface extension of the loop current was inferred from 3 day advanced very high resolution radiometer imagery from october to may when temperature gradients were sufficient to map the warm water unambiguously the deep transports appear at first unrelated to the rate of change of the loop current extension but filtering the series with a 20 day running mean increases the correlation between the low pass series to 0 62 and up to 0 83 with a lag of 8 5 days with loop current changes leading the deep flows the cumulative deep transport a quantity that favors lower frequencies is very well related correlations 0 9 to the surface extension of the loop current also with a lag of about a week these lags are not statistically significant but suggest a timescale for internal adjustment processes in the gulf of mexico the empirical orthogonal function of the current best related to the area extension of the loop current represents a unidirectional flow across the entire deep section flowing either toward or from the gulf of mexico and includes a strong expression of the yucatan undercurrent

forecasting and hindcasting waves with the swan model in the southern california bight abstract the naval research laboratory created a wave forecasting system in support of the nearshore canyon experiment ncex field program the outer nest of this prediction system encompassed the southern california bight this forecasting system is described in this paper with analysis of results via comparison to the extensive buoy network in the region there are a number of potential errors two of which are poor resolution of islands in the bight which have a strong impact on nearshore wave climate and the use of the stationary assumption for computations these two problems have straightforward solutions but the solutions are computationally expensive so an operational user must carefully consider their cost the authors study the impact of these two types of error relative to other errors such as error in boundary forcing using several hindcasts performed after the completion of ncex it is found that with buoy observations as ground truth the stationary assumption leads to a modest increase in root mean square error this is due to relatively poor prediction of the timing of swell arrivals and local sea growth decay the model results are found to be sensitive to the resolution of islands however coarse resolution does not incur an appreciable penalty in terms of error statistics computed via comparison to buoy observations suggesting that other errors dominate inaccuracy in representation of the local atmospheric forcing likely has a significant impact on wave model error perhaps most importantly the accuracy of directional distribution of wave energy at the open ocean boundaries appears to be a critical limitation on the accuracy of the model data comparisons inside the bight

effects of the gulf stream on ocean waves in the present study a third generation numerical wave model is used to study effects of a straight gulf stream and a gulf stream ring on ocean waves in swell and storm conditions the model accounts for all relevant processes of propagation generation and dissipation of the waves including current effects without imposing a priori restraints on the spectral development of the waves the dominating mechanism affecting the waves appears to be current induced refraction even though the short crestedness of the incoming waves tends to mask its effects also in swell conditions depending on wind and wave conditions refraction may trap locally generated waves in the straight gulf stream or it may reflect wave energy back to the open ocean in the gulf stream ring refraction induces a considerable variation in significant wave height and short crestedness but it hardly affects the mean wave direction in storm conditions the processes of generation and dissipation are considerably enhanced in countercurrent situations and reduced following current situations

a case study of wave current interaction near an oceanic front high resolution directional wave spectrum data were obtained from two nasa airborne radars during the frontal air sea interaction experiment fasinex in february 1986 the observations show a significant change in the wave number spectrum across the front on the basis of surveys from a towed sensor and on satellite imagery the front location and current field are estimated a numerical model is developed for the wave current interaction and is used to model the wave refraction across the frontal current a parametric study is performed to demonstrate the effects of current meandering the main consequence of meandering is the formation of caustics and shadow zone regions in which the wave energy is significantly enhanced or reduced spectral simulation along the aircraft track reveals a reduction of more than 60 in wave energy in the shadow zone this is consistent with the observations

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

toward a k profile parameterization of langmuir turbulence in shallow coastal shelves abstractinteraction between the wind driven shear current and the stokes drift velocity induced by surface gravity waves gives rise to langmuir turbulence in the upper ocean langmuir turbulence consists of langmuir circulation lc characterized by a wide range of scales in unstratified shallow water the largest scales of langmuir turbulence engulf the entire water column and thus are referred to as full depth lc large eddy simulations less of langmuir turbulence with full depth lc in a wind driven shear current have revealed that vertical mixing due to lc erodes the bottom log law velocity profile inducing a profile resembling a wake law furthermore in the interior of the water column two sources of reynolds shear stress turbulent nonlocal transport and local stokes drift shear production can combine to lead to negative mean velocity shear meanwhile near the surface stokes drift shear serves to intensify small scale eddies leading to enhanced vertical mixing and disruption of the surface

frequency of ring separations from the loop current in the gulf of mexico a revised estimate the most energetic events in the circulation of the gulf of mexico are the separation of large anticyclonic rings from the loop current building on previous work the authors examine all the apparent rings since july 1973 this new dataset includes the satellite altimetry since 1992 providing a set of 34 consecutive ring formations the primary advantage of altimetry is that the data remain available in the summer one finding is that the ambiguity of whether or not a ring has separated is reduced but not eliminated the uncertainty with which separation events can be specified remains approximately 4 weeks even with nearly continuous data primary peaks in the distribution of separation intervals are found at 6 and 11 months with a smaller peak at 9 months if the spectrum is smoothed heavily enough a peak in the distribution can be formed nearer 12 months but this near annual peak is a result more of the smoothing than of the data

on the seasonal variability of the currents in the straits of florida and yucatan channel 1 seasonal variability in the major passages of the caribbean are investigated using 5 years of wind and current observations explorer of the seas combined with a 3 year 1 12 simulation seasonal fluctuations in the florida and yucatan passages are both characterized by semiannual cycles with transport maxima in summer and winter and minima in spring and fall in the straits of florida seasonal variability is associated with surface intensified fluctuations of the florida current and can be largely explained by along channel winds and wind stress curl over the atlantic ocean in the yucatan channel seasonal variability is more barotropic and does not covary with wind forcing but rather is associated with fluctuations of an anticyclonic recirculation to the south of the channel upstream the seasonality in the grenada passage also covaries with seasonality in the yucatan and florida passages although the grenada passage carries only a small fraction of the total inflow to the caribbean recent in situ estimates of the mean transport in the yucatan channel differ by 7 sv 30 5 sv explorer of the seas 23 1 sv canek an assessment of sampling errors biases and interannual variability seem to account for no more than 2 sv leaving no satisfactory explanation for the difference in explorer of the seas data flows in the straits of florida and yucatan channel display similar vertical shear structure while canek data exhibit significantly lower shears in the upper 500 m which account for all the transport difference

mean flow in the gulf of mexico abstract several independent data sources suggest that there is a net upper layer mass flux o 3 sv sv 106 m3 s 1 to the west in the central gulf of mexico even though the western gulf is a closed basin a plausible explanation is that this net flux is pumped downward by the convergent wind driven ekman pumping as is typical of all midlatitude anticlyclonic gyres the downward flux can follow isopycnals to depths o 500 600 m and deeper by eddy mixing a mechanism for forcing deep water to the south through the yucatan channel is provided by the intrusion and ring shedding cycle of the loop current potential vorticity maps show that a deep flow from the western gulf back to the yucatan channel is likely

climatology of ocean features in the gulf of mexico using satellite remote sensing data a climatology of various ocean features in the gulf of mexico gom was developed using the combination of satellite remote sensing and in situ data that spanned periods as long as 32 years twelve separate statistics were created some of which described characteristics of the loop current while others are involved with warm core rings that separate from the loop current and cold core rings these statistics examined the frequency with which the loop current was found in the gom the orientation of the loop current the frequency of intrusion of loop current water onto the west florida shelf and into the gom common water region ring separation period from the loop current ring dissipation ring speed ring path frequency of ring water in the western gom and the frequency of warm and cold core rings wcrs and ccrs respectively in the gom the results indicate that ccrs were principally responsible for mass and heat redistribution in the eastern gom egom and wcrs are responsible for mass and heat redistribution in the western gom wgom the average period for wcr separation from the loop current was 11 months and the range from 5 to 19 months wcrs moved through the wgom most often using the central path i e their trajectory was found between 24 and 26 n latitude and they decreased to about 55 of their initial size when they reach the western wall of the gom ccrs were most often found in the egom and their frequency of occurrence in the egom surpassed that of wcrs anywhere in the gom

evolution and kinematics of a loop current eddy in the gulf of mexico during 1985 the large eddy that broke off from the loop current in july 1985 was the most extensively studied eddy ever to appear in the gulf of mexico other investigators have described its early evolution based on lagrangian drifters and its later evolution using moored current meters in the western gulf this paper provides additional insight on the early evolution of the eddy using results from air dropped expendable bathythermographs and air dropped expendable current profilers in early may a hydrographic ship survey in mid july and a detailed ship survey in august using expendable bathythermographs and a current profiler the may survey established a center of circulation at about 26 n but showed that the eddy had not separated from the loop current a maximum velocity of 171 cm s was observed near the northern edge of the feature the evidence suggests that a large elongated eddy then separated from the loop current and later split into two smaller eddies the july hydrographic cruise showed a clear separation of the large eddy from the loop current to the southeast two weeks later the august survey showed an asymmetric eddy with the maximum surface current 178 cm s south of the center of circulation and 132 cm s to the north a western eddy named ghost eddy then separated from an eastern eddy named fast eddy using the current profiles and data from the drifters we constructed a simple kinematic feature model for eddies in the gulf of mexico

loop current eddy paths in the western gulf of mexico abstract the paths of anticyclonic loop current eddies in the western gulf of mexico have been investigated using argos tracked drifters accompanied by hydrographic surveys the analysis used orbit parameters derived from a least square fit of a translating ellipse kinematic model and showed that paths from four quite different eddies had a number of similar features they are a general increase in rotational period over time clockwise rotation of ellipse axes that slows with time and often becomes stationary in the far western gulf swirl velocities that decay quite slowly and a tendency of the eddies to have low divergence in three cases 20 to 30 day oscillations of the orbit parameters were observed translation velocities of the orbits showed the characteristic stalls and sprints that have been previously observed in two cases stalls and deviations from solid body rotation could be attributed to the presence of vigorous lower continental slope cyclones situated to the northwest of the eddies in

wave current interaction near the gulf stream during the surface wave dynamics experiment this paper presents a case study on the wave current interaction near the local curvature of a gulf stream meander the wave data were obtained from in situ measurements by a pitch roll discus buoy during the surface wave dynamics experiment swade conducted off wallops island virginia from october 1990 to march 1991 owing to the advection of the gulf stream by the semidiurnal tide the discus buoy was alternately located outside and inside the gulf stream the directional wave measurements from the buoy show the changes in wave direction wave energy and directional spreading when waves encountered the current in the gulf stream meanders a wave refraction model using the ray tracing method with an estimated gulf stream velocity field and meandering condition was used to simulate wave refraction patterns and to estimate wave parameters at relative locations corresponding to buoy measurements the numerical simulation shows that a focusing zone of wave rays was formed near the boundary and behind the crest of a simulated gulf stream meander the focusing of wave rays causes changes in wave direction increases in wave energy and decreases in wave directional spreading which are in good agreement with the results from the buoy measurements

hurricane directional wave spectrum spatial variation at landfall abstract the nasa scanning radar altimeter sra flew aboard one of the noaa wp 3d hurricane research aircraft to document the sea surface directional wave spectrum in the region between charleston south carolina and cape hatteras north carolina as hurricane bonnie was making landfall near wilmington north carolina on 26 august 1998 two days earlier the sra had documented the hurricane wave field spatial variation in open water when bonnie was 400 km east of abaco island bahamas bonnie was similar in size during the two flights the maximum wind speed was lower during the landfall flight 39 m s 1 than it had been during the first flight 46 m s 1 also bonnie was moving faster prior to landfall 9 5 m s 1 than when it was encountered in the open ocean 5 m s 1 the open ocean wave height spatial variation indicated that hurricane bonnie would have produced waves of 10 m height on the shore northeast of wilmington had it not been for the continental shelf the gradual shoaling distributed t

seasonal variability and simulation of groundwater flow in a prairie wetland wetlands in regional discharge areas of the red river valley of eastern north dakota provide runoff flood protection and wildlife habitat two years of groundwater and soil water monitoring were used to characterize the hydrology of a 500 ha wetland 24 km north west of grand forks the objective was to describe monitor and model important water budget processes from november through march 1990 and 1991 the water table dropped as water flowed towards frost in the vadose zone where saturated soils occurred near the surface the water table rose quickly in the spring a later larger rise occurred where the water table and capillary fringe were deeper during the summer precipitation was rapidly depleted by evapotranspiration et the low hydraulic conductivity of the clayey lacustrine sediments 0 1 2 m yr combined with a small horizontal hydraulic gradient results in minimal lateral and maximum vertical flow the us geological survey modflow code was used to simulate vertical saturated flow by including actual et estimated from potential evaporation and using the recharge option to represent vadose flow the model provided good correspondence between observed and simulated hydrographs these results suggest that a shallow vertical flow of ground and soil water dominates the hydrological budget simulation of unusually dry conditions such as those experienced during the 1930s indicates that water levels in the wetland would reach a steady state about 0 3 m lower than normal within two to three years less winter vadose storage would decrease the water level rise in spring and early summer but would have a minimal impact on the overall yearly water budget

in situ measurements of an energetic wave event in the arctic marginal ice zone r v lance serendipitously encountered an energetic wave event around 77 n 26 e on 2 may 2010 onboard gps records interpreted as the surface wave signal show the largest waves recorded in the arctic region with ice cover comparing the measurements with a spectral wave model indicated three phases of interaction 1 wave blocking by ice 2 strong attenuation of wave energy and fracturing of ice by wave forcing and 3 uninhibited propagation of the peak waves and an extension of allowed waves to higher frequencies above the peak wave properties during fracturing of ice cover indicated increased groupiness wave ice interaction presented binary behavior there was zero transmission in unbroken ice and total transmission in fractured ice the fractured ice front traveled at some fraction of the wave group speed findings do not motivate new dissipation schemes for wave models though they do indicate the need for two way wave ice coupling

a loop current intrusion case study on the west florida shelf the gulf of mexico loop current intruded upon the west florida continental shelf in june 2000 in situ currents and hydrography along with satellite temperature and altimetry measurements are used to describe this event and its effects on the shelf a strong southward current is observed to flow along the shelf slope seaward of the intruded water boundary this current transported cold nutrient rich water from the north thereby producing anomalous hydrographic features near the shelf break 80 m isobath an array of moored velocity profilers reveals that the currents landward of the intruded water are independent of the loop current and primarily driven by local winds a series of idealized numerical model simulations inclusive of forcing by both the loop current and local winds confirm the observational findings that the shelfbreak currents are largely loop current controlled while the shelf currents are largely controlled by the local winds

the surface circulation of the caribbean sea and the gulf of mexico as inferred from satellite altimetry the surface circulation of the caribbean sea and gulf of mexico is studied using 13 years of satellite altimetry data variability in the caribbean sea is evident over several time scales at the annual scale sea surface height ssh varies mainly by a seasonal steric effect interannually a longer cycle affects the ssh slope across the current and hence the intensity of the caribbean current this cycle is found to be related to changes in the wind intensity the wind stress curl and el nino southern oscillation at shorter time scales eddies and meanders are observed in the caribbean current and their propagation speed is explained by baroclinic instabilities under the combined effect of vertical shear and the b effect then the loop current lc is considered focusing on the anticyclonic eddies shed by it and the intrusion of the lc into the gulf of mexico through time twelve of the 21 anticyclonic eddies observed to detach from the lc are shed from july to september suggesting a seasonality in the timing of these events also a relation is found between the intrusion of the lc into the gulf of mexico and the size of the eddies shed from it larger intrusions trigger smaller eddies a series of extreme lc intrusions into the gulf of mexico when the lc is observed as far as 928w are described the analyses herein suggest that the frequency of such events has increased in recent years with only one event occurring in 1993 versus three from 2002 to 2006 transport through the straits of florida appears to decrease during these extreme intrusions

observational study of marine atmospheric boundary layer characteristics during swell abstract by combining simultaneous data from an instrumented air sea interaction spar asis buoy and a 30 m tower profiles of wind and turbulence characteristics have been obtained at several heights from about 1 to 30 m above the water surface during swell conditions five cases formed as averages over time periods ranging from 2 5 to 9 5 h representing quasi steady conditions have been selected they represent a range of typical wave age and include wind following swell cases and cross swell cases for relatively large wave age the wind profile exhibits a well defined maximum in the height range 5 10 m for more modest wave age this maximum turns into a sharp knee in the wind profile below the maximum or knee the wind increases rapidly with height above that point the wind is very nearly constant up to the highest measuring level on the tower 30 m analysis of balloon data from one day with swell indicates that the layer with constant wind in fact extends to the top of the boundary layer

a global perspective on langmuir turbulence in the ocean surface boundary layer the turbulent mixing in thin ocean surface boundary layers osbl which occupy the upper 100 m or so of the ocean control the exchange of heat and trace gases between the atmosphere and ocean here we show that current parameterizations of this turbulent mixing lead to systematic and substantial errors in the depth of the osbl in global climate models which then leads to biases in sea surface temperature one reason we argue is that current parameterizations are missing key surface wave processes that force langmuir turbulence that deepens the osbl more rapidly than steady wind forcing scaling arguments are presented to identify two dimensionless parameters that measure the importance of wave forcing against wind forcing and against buoyancy forcing a global perspective on the occurrence of wave forced turbulence is developed using re analysis data to compute these parameters globally the diagnostic study developed here suggests that turbulent energy available for mixing the osbl is under estimated without forcing by surface waves wave forcing and hence langmuir turbulence could be important over wide areas of the ocean and in all seasons in the southern ocean we conclude that surface wave forced langmuir turbulence is an important process in the osbl that requires parameterization citation belcher s e et al 2012 a global perspective on langmuir turbulence in the ocean surface boundary layer geophys res lett 39 l18605 doi 10 1029 2012gl052932

wave current interaction study in the gulf of alaska for detection of eddies by synthetic aperture radar high resolution ers i synthetic aperture radar sar images are used to detect a mesoscale eddy such features limit dispersal of pollock larvae and therefore likely influence recruitment of fish in the gulf of alaska during high sea states and high winds the direct surface signature of the eddy was not clearly visible but the wave refraction in the eddy area was observed the rays of the wave field are traced out directly from the sar image the ray pattern gives information on the refraction pattern and on the relative variation of the wave energy along a ray through wave current interaction these observations are simulated by a ray tracing model which incorporates a surface current field associated with the eddy the numerical results of the model show that the waves are refracted and diverge in the eddy field with energy density decreasing the model data comparison for each ray shows the model predictions are in good agreement with the sar data

some observations of wave current interaction abstract using data collected during the scawvex project the effect of depth and current changes particularly tidal on waves and the effect of waves on tidal currents were examined the possible interaction mechanisms between waves tides and surges are reviewed these include the effective surface wind stress bottom friction depth and current refraction and modulation of the absolute and relative wave period the usefulness of tidal periodicity in identifying both interactions in wave parameters and the effects of the waves on the tide is noted for correct analysis to obtain wave free tidal conditions or tidally averaged wave statistics it is particularly important to understand the interaction mechanisms for example the amplitude of the tidal current was found to be reduced in periods of high waves ideally waves and currents should always be measured simultaneously since the correct determination of either in shallow water requires knowledge of the other various remote sensing systems which can potentially do this are discussed since the algorithms are quite complex and may depend on a good first guess the future probably lies in combining remote sensing plus modelling together with ground truth in situ data

mesoscale variability in the northeastern tropical pacific forcing mechanisms and eddy properties 1 the generation mechanisms and properties of the mesoscale eddies in the northeastern tropical pacific netp are studied using a series of numerical solutions and satellite observations the spatial and temporal resolution of mountain wind jets over the gulfs of tehuantepec and papagayo are essential for an accurate modeling of the regional mesoscale variability three previously proposed eddy generation mechanisms are the local transient wind forcing the combined low frequency wind and boundary forcing and the remote equatorial kelvin wave forcing in our model the transient wind forcing was represented by wind fields with synoptic variability and the remote equatorial kelvin wave forcing by 5 day open boundary conditions with interannual variability solutions with and without high frequency forcings are contrasted to evaluate the contributions of the three mechanisms the combined low frequency wind and boundary forcing is the primary eddy forcing mechanism in the netp in the tehuantepec region the high frequency wind forcing contributes more to the mesoscale variability than the remote equatorial kelvin wave forcing while in the papagayo region their contributions are comparable eddies in the tehuantepec and papagayo regions are larger in both amplitude and size and are more likely to deflect equatorward than eddies in the rest of the netp the maximum temperature anomaly of eddies is at around 50 m depth eddies with lifetimes 6 weeks are more likely anticyclonic while eddies with lifetimes 6 weeks are more likely cyclonic the anticyclone dominance for large amplitude long lived eddies is the combined consequence of wind driven asymmetric dipole spin up and the evolutionary fragility of large amplitude cyclones

contrasting styles of swell driven coastal erosion examples from kwazulu natal south africa during 2006 2007 the kwazulu natal coast of south africa was exposed to several large swell events ho 3 m near the peak of the lunar nodal cycle causing shoreline recession the largest swell hs 8 5 m struck the coast on the march equinox 18th 20th and generated a strong storm return flow observations made before during and after record dramatic coastal erosion shoreline recession of up to 40 m and substantial property damage this swell event removed the semi continuous nearshore bar system and conditioned the coast such that lesser subsequent swell events accomplished much greater amounts of coastal erosion than expected up to 100 m at certain erosion hotspots because waves reached the coast without significant energy dissipation subsequent bar generation rebuilt the inshore bars within six months the styles of erosion during the march 07 event and other 2007 swells were markedly different lesser swells are focused by headlands and result in megarip development and activation of erosion hotspots the march 07 event still water level was raised equinoctial spring high tide and a storm surge of 0 33 0 45 m to a level that rendered most headlands and erosion hotspots ineffective and resulted in laterally extensive erosion of soft shorelines results record cumulative effects of successive swell events on coastal behaviour that proved to be critical in enabling erosion to proceed at rapid rates after the coast had been initially destabilized unlike hurricanes and tsunamis surges associated with swell events are relatively minor and therefore extensive erosion is linked with high lunar tides there is circumstantial evidence that swell induced erosion follows the broad 18 6 yr lunar nodal tidal cycle when the chances of large swells coinciding with high water levels are increased

the signature of inertial and tidal currents in offshore wave records the roughness of the sea surface can be affected by strong currents here long records of surface wave heights from buoy observations in the northeastern pacific ocean are examined the data show the influence of tidal currents but the first evidence of wave height modulation up to 20 at a frequency that is slightly higher than the local inertial frequency is also found this finding shows the effect on surface waves of nearinertialcurrents whicharetypicallythemostenergeticcurrentsin theopenocean theresulthasimplications for wave forecasting but also provides valuable information on the frequency strength and intermittency of the associated near inertial motions

hurricane forced upwelling and chlorophyll a enhancement within cold core cyclones in the gulf of mexico 1 clear skies subsequent to hurricane ivan s passage across the gulf of mexico in september 2004 provided a unique opportunity to investigate upper ocean responses to a major hurricane oceanic cyclonic circulation was rapidly intensified by the hurricane s wind field 59 62 m s 1 maximizing upwelling and surface cooling 3 7 c in two large areas along ivan s track upward isothermal displacements of 50 65 m computed from wind stress and sea surface height changes caused rapid ventilation of thermoclines and nutriclines leading to phytoplankton blooms with peak concentrations 3 4 days later wind speed changes along ivan s track demonstrated that the cool waters 20 26 c provided immediate negative feedback to the hurricane s intensity although our study focused on a relatively small ocean area it revealed that mesoscale cyclones in addition to warm anticyclones may play an important role in producing along track hurricane intensity changes