ka band backscattering from water surface at small incidence a wind wave tank study we report on an experiment conducted at the large pytheas wind wave facility in marseille to characterize the ka band radar return from water surfaces when observed at small incidence simultaneous measurements of capillary gravity to gravity wave height and slopes and normalized radar cross section nrcs were carried out for various wind speeds and scattering angles from this data set we construct an empirical two dimensional wave number spectrum accounting for the surface current to describe water surface motions from decimeter to millimeter scales some consistency tests are proposed to validate the surface wave spectrum which is then incorporated into simple analytical scattering models the resulting directional nrcs is found in overall good agreement with the experimental values comparisons are performed with oceanic models as well as in situ measurements over different types of natural surfaces the applicability of the present findings to oceanic as well as continental surfaces is discussed

reinterpretation of late quaternary sediment chronology of lake biwa japan from correlation with marine glacial interglacial cycles a review of published stratigraphic records of pollen sediment grain size diatoms and organic matter composition from lake biwa japan identifies four pre holocene episodes of milder climate increased surface runoff and enhanced aquatic productivity indicating intervals of warmer and wetter conditions which are interpreted as being interglacial correlation of these episodes to times of marine interglacial periods revises the age scale of the lake biwa sediment sequence which has been based on fission track dating the revised chronostratigraphic scale proposes an age of ca 430 000 yr b p for the base of the 250 m thick t bed instead of the former age of ca 700 000 yr b p

a numerical study of wave current interaction through surface and bottom stresses coastal ocean response to hurricane fran of 1996 1 a three dimensional wave current coupled modeling system is used to examine the influence of waves on coastal currents and sea level this coupled modeling system consists of the wave model wam cycle 4 and the princeton ocean model pom the results from this study show that it is important to incorporate surface wave effects into coastal storm surge and circulation models specifically we find that 1 storm surge models without coupled surface waves generally under estimate not only the peak surge but also the coastal water level drop which can also cause substantial impact on the coastal environment 2 introducing wave induced surface stress effect into storm surge models can significantly improve storm surge prediction 3 incorporating wave induced bottom stress into the coupled wave current model further improves storm surge prediction and 4 calibration of the wave module according to minimum error in significant wave height does not necessarily result in an optimum wave module in a wave current coupled system for current and storm surge prediction

the nonseismic tsunami observed in the bulgarian black sea on 7 may 2007 was it due to a submarine landslide 1 a tsunami like sea disturbance of nonseismic origin was observed on 7 may 2007 on the bulgarian black sea coast the maximum wave amplitude was three meters and the sea oscillations lasted for several hours the anomalous behaviour was seen in many places of the coast of bulgaria and was stronger in the north several accounts of eyewitnesses as well as reports of local port authorities and three tide gauge recordings are available and have been collected and analysed the tsunami could have been produced by a submarine landslide or by atmospheric pressure pulses here we explore the former hypothesis i e the possibility that the tsunami was induced by a landslide that may have occurred on the shelf margin off bulgaria by making use of numerical modelling we find that submarine mass movements taking place within a certain delimited source area off bulgaria may have generated tsunamis compatible with the observations

importance of peakedness in sea surface slope measurements and applications we recall the simple statistical concept that non gaussian distribution peakedness results from the compounding of random processes this idea is applied to observations and analysis of sea surface slopes as inferred using optical and microwave scattering measurements our study emphasizes the importance of identifying and quantifying the distribution variance and kurtosis from observations data are shown to indicate consistently non gaussian peakedness to indicate the need to report at least two parameters in an even order analysis and to indicate near equivalence between radar and optical data physical interpretation for observed infrequent steep slopes is given via compounding statistical processes where normally distributed short scale waves are modulated because of random fluctuations mainly associated with the underlying long wave field implications of non gaussian peakedness are provided for altimeter backscatter theory and for modeling wave breaking probability

wave spectrum retrieval from airborne sunglitter images abstract reconstruction and evolution of two dimensional spectra of surface waves in the gulf of mexico are derived from airborne sun glitter imagery as the proposed method is based on a linear transfer function deduced from the shape of the sunglitter brightness the absolute wavenumber elevation spectrum does not require any additional assumption or information about sky brightness wind or wave energy the detailed description of the airborne image processing method is given as demonstrated retrieved spectra agree well with nearby ndbc buoy data both for spectrum shape level and energy angular distribution the 180 degree wave direction ambiguity inherent to image derived spectra is eliminated by using cross correlation analysis between two consecutive images a case study corresponding to the spectral evolution with increasing distance from shore in slanting fetch conditions is then considered energy level and peak position transformation are consistent with established approximations and laws of wind sea development the technical requirements flight altitude image resolution view angles etc and applicability of the suggested methodology are also discussed these results demonstrate the potential efficiency of high resolution sea state monitoring from drones or light aircrafts using sunglitter imagery

a geosat altimeter wind speed algorithm and a method for altimeter wind speed algorithm development a geosat altimeter wind speed algorithm is derived by cross calibrating geosat and seasat altimeter estimates of the normalized radar cross section 0 and modifying an existing seasat altimeter wind speed model function to obtain a model function appropriate for geosat observations it is argued that the 0 distribution measured by an altimeter is relatively stable over a sufficiently large geographical region and a long enough time period systematic differences between 0 estimates from two altimeters can therefore be identified based on comparisons of their 0 histograms any such systematic differences can then be corrected using independent 0 estimates when this method is applied to the geosat and seasat altimeters a systematic difference between the two 0 histograms is shown to be consistent with differences between seasat altimeter and nadir seasat scatterometer estimates of 0 deduced independently by a previous study this supports the conclusions that 1 the 0 distribution is stable and 2 the seasat altimeter estimates of 0 were miscalibrated after modifying the existing seasat altimeter wind speed algorithm to account for this apparent 0 error the resulting geosat estimates of wind speed agree with high quality buoy observations to within an rms difference of less than 2 m s

azimuthal and radial variation of wind generated surface waves inside tropical cyclones abstractfor wind generated waves the wind wave triplets reference wind speed significant wave height and spectral peak wave period are intimately connected through the fetch or duration limited wave growth functions the full set of the triplets can be obtained knowing only one of the three together with the input of fetch duration information using the pair of fetch limited duration limited wave growth functions the air sea energy and momentum exchanges are functions of the wind wave triplets and they can be quantified with the wind wave growth functions previous studies have shown that the wave development inside hurricanes follows essentially the same growth functions established for steady wind forcing conditions this paper presents the analysis of wind wave triplets collected inside hurricane bonnie 1998 at category 2 stage along 10 transects radiating from the hurricane center a fetch model is formulated for any location inside the hurricane applying the fetch model to the 2d hurric

measuring sea surface mean square slope with a 36 ghz scanning radar altimeter values of sea surface mean square slope mss computed from the backscattered power falloff with incidence angle measured by an airborne 36 ghz scanning radar altimeter are presented when the mss values are plotted against the 10 m wind speed extrapolated from the 46 to 110 m aircraft height for wind speeds up to 7 m s 1 the values scatter about a curve which is scaled from that obtained by wu 1990 by a factor of 0 85 wu s result was a reanalysis of the optical measurements of cox and munk 1954 the offset between the microwave and optical curves is reasonable because one would expect the surface to appear smoother to the microwave wavelength than to the optical this is unlike the mss values inferred from absolute power measurements at nadir by 14 ghz satellite altimeters which indicate a higher mss under light wind conditions than the optical measurements indicate for wind speeds below 7 m s 1 the peak of the backscattered power distribution is observed at nadir but for higher speeds the peak shifts off nadir in the downwind direction

tangential stress beneath wind driven air water interfaces the detailed structure of the aqueous surface sublayer flow immediately adjacent to the wind driven air water interface is investigated in a laboratory wind wave flume using particle image velocimetry piv techniques the goal is to investigate quantitatively the character of the flow in this crucial very thin region which is often disrupted by microscale breaking events in this study we also examine critically the conclusions of okuda kawai toba 1977 who argued that for very short strongly forced wind wave conditions shear stress is the dominant mechanism for transmitting the atmospheric wind stress into the water motion waves and surface drift currents in strong contrast other authors have more recently observed very substantial normal stress contributions on the air side the availability of piv and associated image technology now permits a timely re examination of the results of okuda et al which have been influential in shaping present perceptions of the physics of this dynamically important region the piv technique used in the present study overcomes many of the inherent shortcomings of the hydrogen bubble measurements and allows reliable determination of the fluid velocity and shear within 200 m of the instantaneous wind driven air water interface the results obtained in this study are not in accord with the conclusions of okuda et al that the tangential stress component dominates the wind stress it is found that prior to the formation of wind waves the tangential stress contributes the entire wind stress as expected with increasing distance downwind the mean tangential stress level decreases marginally but as the wave field develops the total wind stress increases significantly thus the wave form drag represented by the difference between the total wind stress and the mean tangential stress also increases systematically with wave development and provides the major proportion of the wind stress once the waves have developed beyond their early growth stage this scenario reconciles the question of relative importance of normal and tangential stresses at an air water interface finally consideration is given to the extrapolation of these detailed laboratory results to the field where the present findings suggest that the sea surface is unlikely to become fully aerodynamically rough at least for moderate to strong winds

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

multifaceted re analysis of the enigmatic kitimat slide complex canada abstract repeat submarine landslides are challenging to study due to the tendency of subsequent slides to destroy previous deposits repeat slides are common in fjord head deltas where high amounts of sediment are focused in narrow valleys this study examines a well known slide deposit associated with the kitimat delta on canada s west coast that has been linked to tsunamigenic landslides in 1974 and 1975 for the first time we incorporate multibeam bathymetry to a multifaceted dataset including new high resolution acoustic data and sediment cores to examine the history of submarine slides at the kitimat delta based on morphological analysis and age modelling using 210pb and 14c data we determine that the complex surface morphology of the slide lobe consists of at least two large slide deposits that reach 5 km from the delta the known event that occurred in 1975 and an older event that occurred at 623 83 cal bp 95 confidence interval we demonstrate that slide deposits can be differentiated based on surface morphology and acoustic character this is confirmed by age modelling the 1975 slide resulted in a flow that ploughed through the seabed creating compression and translation along a basal shear plane resulting in deep deformation and a surface characterized by pressure ridges the 623 83 cal bp event resulted in a large amount of blocky slide material that overran the former seafloor and was transported 5 km from the delta front several buried events are observed at depth one of which occurred at 2592 84 cal bp and appears to be on the same order of magnitude as the 1975 event and showing very similar acoustic characteristics as for hazard implications we show submarine landslides of varying sizes have naturally occurred on this delta throughout the past several thousand years

ocean wave slope observations using radar backscatter and laser altimeters abstract combination of laser and radar aboard an aircraft is used to directly measure long gravity wave surface tilting simultaneously with nadir viewing microwave backscatter from the sea surface the presented dataset is extensive encompassing varied wind conditions over coastal and open ocean wave regimes laser derived slope statistics and ka band 36 ghz radar backscatter are detailed separately to document their respective variations versus near surface wind speed the slope statistics measured for 1 2 m show good agreement with cox and munk s oil slickened sea measurements a notable exception is elevated distribution peakedness and an observed wind dependence in this likely proxy for nonlinear wave wave interactions aircraft ka band radar data nearly mimic ku band satellite altimeter observations in their mean wind dependence the present calibrated radar data along with relevant observational and theoretical studies suggest a large 5 db bias in previous ka band results next wave

onset of submarine debris flow deposition far from original giant landslide submarine landslides can generate sediment laden flows whose scale is impressive individual flow deposits have been mapped that extend for 1 500 km offshore from northwest africa these are the longest run out sediment density flow deposits yet documented on earth this contribution analyses one of these deposits which contains ten times the mass of sediment transported annually by all of the world s rivers understanding how this type of submarine flow evolves is a significant problem because they are extremely difficult to monitor directly previous work has shown how progressive disintegration of landslide blocks can generate debris flow the deposit of which extends downslope from the original landslide we provide evidence that submarine flows can produce giant debris flow deposits that start several hundred kilometres from the original landslide encased within deposits of a more dilute flow type called turbidity current very little sediment was deposited across the intervening large expanse of sea floor where the flow was locally very erosive sediment deposition was finally triggered by a remarkably small but abrupt decrease in sea floor gradient from 0 05 degrees to 0 01 degrees this debris flow was probably generated by flow transformation from the decelerating turbidity current the alternative is that non channelized debris flow left almost no trace of its passage across one hundred kilometres of flat 0 2 degrees to 0 05 degrees sea floor our work shows that initially well mixed and highly erosive submarine flows can produce extensive debris flow deposits beyond subtle slope breaks located far out in the deep ocean

simulation of storm surge wave currents and inundation in the outer banks and chesapeake bay during hurricane isabel in 2003 the importance of waves 1 this paper investigates the effects of waves on storm surge currents and inundation in the outer banks and chesapeake bay during hurricane isabel in 2003 through detailed comparison between observed wind wave surge and inundation data and results from an integrated storm surge modeling system ch3d ssms ch3d ssms which includes coupled coastal and basin scale storm surge and wave models successfully simulated measured winds waves storm surge currents and inundation during isabel comprehensive modeling and data analysis revealed noticeable effects of waves on storm surge currents and inundation among the processes that represent wave effects radiation stress outside the estuaries and wave induced stress outside and inside the estuaries are more important than wave induced bottom stress in affecting the water level maximum surge was 3 m while maximum wave height was 20 m offshore and 2 5 m inside the chesapeake bay where the maximum wave induced water level reached 1 m significant waves reached 3 5 m and 16 s at duck pier north carolina and 1 6 m and 5 s at gloucester virginia at duck wave effects accounted for 36 cm or 20 of the peak surge elevation of 1 71 m inside the chesapeake bay wave effects account for 5 10 of observed peak surge level a two layer flow is found at kitty hawk north carolina during the peak of storm surge owing to the combined effects of wind and wave breaking higher surge elevations result when the 3 d surge model instead of the 2 d surge model is coupled with the 2 d wave model owing to its relatively lower bottom friction wave heights obtained with 3 and 2 d surge models show little difference

multistage collapse of eight western canary island landslides in the last 1 5 ma sedimentological and geochemical evidence from subunits in submarine flow deposits volcaniclastic turbidites in the madeira abyssal plain provide a record of major landslides from the western canary islands in the last 1 5 ma these volcaniclastic turbidites are composed of multiple fining upward turbidite sands known as subunits the subunits indicate that the landslides responsible for the sediment gravity flows occurred in multiple stages the subunits cannot result from flow reflection or splitting because the compositions of volcanic glasses from each individual subunit in an event bed are subtly different this indicates that each subunit represents a discrete failure as part of a multistage landslide this has significant implications for geohazard assessments as multistage failures reduce the magnitude of the associated tsunami the multistage failure mechanism reduces individual landslide volumes from up to 350 km3 to less than 100 km3 thus although multistage failure ultimately reduce the potential landslide and tsunami threat the landslide events may still generate significant tsunamis close to source

biogenic silica record in lake biwa of central japan over the past 145 000 years abstract the record of the biogenic silica flux bsf g cm 2 103yr 1 in lake biwa reflects changes in diatom productivity in the lake and provides information regarding changes in paleoclimatic conditions the bsf record of lake biwa demonstrates five periods over the past ca 145 000 yr when the bsf values were significantly greater than 7 5 g cm 2 103yr 1 and five intervals when they were lower the data imply that paleoclimatic conditions were warmer and wetter from ca 123 000 to 115 000 103 000 to 95 000 88 000 to 72 000 57 000 to 32 000 yr b p and around ca 6000 yr b p when the bsf values were greater and relatively dry and cold from ca 141 000 to 123 000 yr b p and during intervals between two of the five warm and wet episodes when the bsf values were lower time series of the bsf record can be correlated with the record of biogenic silica content in lake baikal and the marine oxygen isotope stages 1 through 6 furthermore the bsf values varied with much higher amplitude during the last interglaciation than during the last glaciation probably implying that the diatom productivity in lake biwa was likewise more variable and had a larger range under interglacial conditions than under glacial conditions

climato hydrological fluctuations printed in long lacustrine records in lake hovsgol mongolia abstract a provisional age model is proposed for hdp 04 sedimentary records from lake hovsgol on the mongolian plateau of a middle latitude zone during the brunhes epoch the model is established on the basis of two procedures first age model linear age model with some dates c 14 238 u 234 u 230 th and paleomagnetic events and a second age model with auto orbital tuning for the first age model the age model suggests that the mis 1 to mis 7 interval is included in the upper part and the mis 11 to mis 19 is included in the lower part in addition to the missing part of about 100 ky the glacial interglacial cycle is most clearly presented by aridity water level change three milankovitch parameters precession obliquity and eccentricity are detected in most datasets grain size is occasionally large in glacial intervals and small in interglacial ones in the upper part above the hiatus possibly related to material mobility with water level change change in erosion area and wind availability a deep depression cold stage comparable to glacial periods corresponded to an insolation minimum is detected at about the mis 5d in records indicating that this region is highly sensitive to solar insolation another depression found during the mis 11 interval also corresponded to a small insolation minimum showing that the interval was not a simple prolonged interglacial period

tectonic and climatic record of the lake biwa japan region provided by the sediments deposited since pliocene times abstract the sediments of lake biwa japan contain a potential record of eastern asian paleoclimates that date from the early pliocene a continuous drilled core of lake sediments with a recovery of 70 was obtained in 1982 1983 to allow study of this record dating of core samples by a combination of tephrochronology magnetostratigraphy and fission track methods has revealed that parts of the sedimentary record apparently are missing even though obvious discontinuities cannot readily be detected from lithostratigraphic and seismic data tectonically induced migration of the basin center from its former more southerly location may be responsible for several hiatuses in the sedimentary record which are more common in its earlier part the record during the brunhes epoch appears to be relatively complete sediments indicate warm cold changes in land vegetation which may record glacial cycles deeper sediments contain evidence of warmer climate late neogene flora tectonic events can be inferred from changes in sediment type and in sedimentation rates

momentum transfer over the coastal zone spatial variations of surface stress over the coastal shoaling zone are studied offshore of duck north carolina by the longez research aircraft equipped to measure both atmospheric turbulence and oceanic waves we find that the spatial variation of the friction velocity with offshore distance is much larger with offshore flow than with onshore flow in general the mean square slope of the short waves wavelength shorter than 2 m decreases with offshore distance while the mean square slope of the long waves wavelength longer than 2 m increases with offshore distance with onshore flow the friction velocity is strongly correlated with surface waves in addition the variation of the neutral drag coefficient is well correlated with the atmospheric bulk richardson number with offshore flow the observed momentum flux significantly decreases with offshore distance within the first few kilometer offshore the relationship between the friction velocity and the mean square slope of the short waves and the relationship between the neutral drag coefficient and the atmospheric bulk richardson number are obscured by the direct influence of the upstream land surface on the measured turbulence these relationships for offshore flow agree well with those for onshore flow if the fetch is beyond the immediate influence of the land surface the results in this study suggests that the effects of the strong turbulence advected from over the nearby land surface in offshore flow may lead to ambiguous physical interpretation of the correlation between the momentum flux and the wave state

off nadir radar altimetry the characteristics of nadir versus off nadir altimetry are reviewed and contrasted and a potentially serious problem has been pointed out that has been overlooked by earlier investigators who focused on the nongeophysical error sources in off nadir altimetry spatial gradients of radar cross section on the sea surface caused by wind or current gradients or the variation of radar cross section with incidence angle could introduce significant range errors in off nadir altimeter this potentially crippling effect can be overcome by leaving the traditional 13 ghz frequency and implementing the multibeam altimeter at 36 ghz a multibeam altimeter proposed for the eos earth observing system is described as well as a multimode airborne radar altimeter being developed to study problems inherent in off nadir altimetry

analysis of surface wind and roughness length evolution with fetch using a combination of airborne lidar and radar measurements 1 a combination of surface wind speed sws and sea state variables derived from quasi simultaneous airborne lidar and radar measurements made in the framework of the flux etat de mer et teledetection en condition de fetch variable fetch experiment is used to analyze the evolution of surface roughness length neutral drag coefficient and friction velocity coefficient with fetch in the first hundred kilometers offshore over the gulf of lion western mediterranean the study focuses on the tramontane mistral event documented in the afternoon of 24 march 1998 particular attention is given to sws derived from nadir lidar measurements the sws retrieval methodology developed and validated for open ocean conditions by flamant et al 1998 has been modified to account for the specificity of the coastal mediterranean environment complex mixture of continental and maritime aerosol turbid productive waters the lidar derived sws evolution with fetch observed on 24 march 1998 in the afternoon was validated against in situ and remote sensing measurements made from a buoy a ship as well as from the spaceborne altimeter topex the spatial variability in sws observed with the airborne lidar was controlled by the structure of the wake regions downstream of the massif central and the maritime alps delimiting the longitudinal extension of the mistral and was influenced by swell resulting from the action of a steady northeasterly flow coming from the ligurian sea in connection with intense alpine lee cyclogenesis these findings were supported by the other measurements it is further shown that based on a formulation of the dimensionless roughness dependance with wave age airborne lidar and radar measurements can be combined to provide insight into the evolution with fetch of roughness length neutral drag coefficient and friction velocity four distinct sea state regimes over a distance of 100 km could be identified from the remotely sensed variables obtained with this novel approach in connection with atmospheric forcing the dependance of lidar radar derived drag coefficient with lidar derived sws for the four regimes was found to be remarkably consistent with the relationship derived from the buoy measurements finally lidar radar derived friction velocities were found in good agreement with the buoy and in situ aircraft measurements

on the dependence of sea surface roughness on wave development abstract the aerodynamic roughness of the sea surface z0 is investigated using data from lake ontario from the north sea near the dutch coast and from an exposed site in the atlantic ocean off the coast of nova scotia scaling z0 by rms wave height gives consistent results for all three datasets except where wave heights in the atlantic ocean are dominated by swell the normalized roughness depends strongly on wave age younger waves traveling slower than the wind are rougher than mature waves alternatively the roughness may be normalized using the friction velocity u of the wind stress again young waves are rougher than mature waves this contradicts some recent deductions in the literature but the contradiction arises from attempts to describe z0 in laboratory tanks and in the field with a single simple parameterization here it is demonstrated that laboratory waves are inappropriate for direct comparison with field data being much smoother than their field equivalents in the open ocea

peakedness effects in near nadir radar observations of the sea surface the simulation and interpretation of microwave sea radar return in the near nadir region are still issues in view of the limitations of the geometrical optics approximation and the multiscale and non gaussian nature of the surface we show that an unambiguous and fully consistent physical approach can be reached in the framework of the physical optics the model is developed on the basis of various satellite and airborne c ku and ka band measurements using different reference surface roughness spectra as found the introduction of a peakedness correction based upon the excess kurtosis of slopes is necessary to obtain consistent analysis across the microwave frequency range the model yields accurate simulations for the omnidirectional near nadir normalized radar cross section in different frequency bands provided the spectrum satisfies some a priori constraints on the distribution of the total and filtered slopes

evidence of slumping sliding in krishna godavari offshore basin due to gas fluid movements abstract the krishna godavari kg offshore basin is one of the promising petroliferous basins of the eastern continental margin of india drilling in this basin proved the presence of gas hydrate deposits in the shallow marine sediments beyond 750 m water depths and provided lithologic and stratigraphic information we obtained multibeam swath bathymetry covering an area of about 4500 km 2 in water depths of 280 1800 m and about 1260 line km of high resolution seismic hrs records the general lithology of midslope deposits is comprised of nannofossil rich clay nannofossil bearing clay and foraminifera bearing clay the hrs records and bathymetry reveal evidence of slumping and sliding of the upper and midslope sediments which result in mass transport deposits mtd in the northwestern part of the study area these deposits exhibit 3 9 5 km widths and extend 10 13 km offshore the boundaries of the mtds are often demarcated by sharp truncation of finely layered sediments fls and the mtds are characterized by acoustically transparent zones in the hrs data average thickness of recent mtds varies with depth i e in the upper slope the thickness is about 45 m while in the lower slope it is about 60 m and in deeper offshore locations they attain a maximum thickness of about 90 m a direct indication for slumping and mass transportation of deposits is provided by the age reversal in 14 c ams dates observed in a sediment core located in the midslope region seismic profiling signatures provide indications of fluid gas movement we propose that the presence of steep topographic gradients high sedimentation rates a regional fault system diapirism fluid gas movement and neotectonic activity may have facilitated the slumping sliding of the upper slope sediments in the kg offshore basin

the southern ocean waves experiment part iii sea surface slope statistics and near nadir remote sensing abstract during the southern ocean waves experiment sowex registered ocean wave topography and backscattered power data at ka band 36 ghz were collected with the nasa scanning radar altimeter sra off the coast of tasmania under a wide range of wind and sea conditions from quiescent to gale force winds with 9 m significant wave height collection altitude varied from 35 m to over 1 km allowing determination of the sea surface mean square slope mss the directional wave spectrum and the detailed variation of backscattered power with incidence angle which deviated from a simple gaussian scattering model the non gaussian characteristics of the backscatter increased systematically with the mss suggesting that a global model to characterize ka band radar backscatter from the sea surface within 25 of nadir might be possible

a unified deep to shallow water wave breaking probability parameterization 1 breaking probabilities and breaking wave height distributions bwhds in deep intermediate and shallow water depth are compared and a generic parameterization is proposed to represent the observed variability of breaking parameters as a function of the nondimensional water depth in intermediate and deep water where waves of different scales may have markedly different breaking probabilities a bwhd as a function of wave frequency is proposed and validated with intermediate depth and deep water observational data the current study focuses on waves with frequencies between 0 55 and 3 45 times the peak frequency fp for the dominant frequency the integration of the frequency dependent bwhd provides a breaking probability that reproduces the known threshold type behavior of the breaking probability for dominant waves in shallow water the present breaking statistics parameterization is consistent with other independent formulations validated by shallow water breaking observations

an observation of the directional wave spectrum evolution from shoreline to fully developed abstract the surface contour radar scr is a 36 ghz computer controlled airborne system which produces ocean directional wave spectra with much higher angular resolution than pitch and roll buoys scr observations of the evolution of the fetch limited directional wave spectrum are presented which indicate the existence of a fully developed sea state the jonswap wave growth model for wave energy and frequency was in best agreement with the scr measurements the model of donelan et al correctly predicted the propagation direction of waves in the asymmetrical fetch situation nearshore the donelan et al parameterization is generalized to permit other growth algorithms to predict the correct direction of propagation in asymmetrical fetch situations

air water momentum flux observations over shoaling waves abstract this paper drab with simultaneous momentum flux observations from four towers placed at different depths along a shore normal line at the west end of lake ontario canada the towers were at nominal depths of 12 8 4 and 2 m in order to study the influence of shoaling waves on the air water momentum flux namely the effect of wave steepness and celerity on the aerodynamic roughness of the water surface analysis of the data have shown that the momentum fluxes cannot he explained by mean downwind speed alone u10 in contrast to open ocean experiments in which the wave maturity is generally near full development surface roughness z0 normalized on wave height was parameterized by both the inverse wave age u10 cp and the root mean square wave slope 0 with excellent correlation in each case r2 0 79 multiple regression using both the inverse wave age and the root mean square slope lead to the best results z0 2 26 u10 cp 1 82 3 83 r2 0 90 these findings are presented a

the dependence of sea surface roughness on the height and steepness of the waves it is proposed that the sea surface roughness zo can be predicted from the height and steepness of the waves zo hs a hs lp b where hs and lp are the significant wave height and peak wavelength for the combined sea and swell spectrum best estimates for the coefficients are a 1200 b 4 5 the proposed formula is shown to predict well the magnitude and behavior of the drag coefficient as observed in wave tanks lakes and the open ocean thus reconciling observations that previously had appeared disparate indeed the formula suggests that changes in roughness due to limited duration or fetch are of order 10 or less thus all deep water pure windseas regardless of fetch or duration extract momentum from the air at a rate similar to that predicted for a fully developed sea this is confirmed using published field data for a wide range of conditions over lakes and coastal seas only for field data corresponding to extremely young waves u10 cp 3 were there appreciable differences between the predicted and observed roughness values the latter being larger on average significant changes in roughness may be caused by shoaling or by swell a large increase in roughness is predicted for shoaling waves if the depth is less than about 0 2lp the presence of swell in the open ocean acts on average to significantly decrease the effective wave steepness and hence the mean roughness compared to that for a pure windsea thus the predicted open ocean roughness is at most wind speeds significantly less than is observed for pure wind waves on lakes only at high wind speeds such that the windsea dominates the swell do the mean open ocean values reach those for a fully developed sea

dimensionally consistent similarity relation of ocean surface friction coefficient in mixed seas abstractapplying wavelength scaling dimensionally consistent expressions of the ocean surface friction coefficient can be developed for both wind sea and mixed sea in the ocean for a wind sea with a monopeak wave spectrum the natural choice of the scaling wavelength is that of the spectral peak component for a mixed sea with a multipeak spectrum the peak component in the wind sea portion of the wave spectrum is not a good reference wavelength a much better scaling wavelength is the weighted average of swell and wind sea following the consideration of equivalent momentum in the wave field the resulting friction coefficient c 2 is referenced to the wind speed at one half of the scaling wavelength u 2 instead of c10 referenced to the neutral wind speed at 10 m elevation u10 although referencing the wind speed at a fixed elevation such as u10 is of practical necessity u 2 is physically significant as the free stream velocity in wave modulated boundary layer flows a simple procedure to apply the s

a case study of air sea interaction during swell conditions air sea interaction data from a situation with pronounced unidirectional swell have been analyzed measurements of turbulence at three levels 10 18 and 26 m above mean sea level together with directional wave buoy data from the site ostergarnsholm in the baltic sea were used the situation which lasted for 48 hours appeared in the aftermath of a gale the wind direction during the swell situation turned slowly within a 90 sector both during the gale phase and the swell phase the over water fetch was 150 km the wind speed during the swell phase was typically 4 m s 1 during the swell phase a wind maximum near or below the lowest wind speed measuring level 10 m was observed the net momentum flux was very small resulting in cd values 0 7 10 3 throughout the lowest 26 m covered by the tower measurements turbulence intensities in all three components remained high despite the low value of the kinematic momentum flux u w resulting in a reduction of the correlation coefficient for the longitudinal and vertical velocity from its typical value around 0 35 to between 0 2 and 0 and with some positive values at the higher measuring levels appearing abruptly at wave age c0 u10 equal to 1 2 turbulence spectra of the horizontal components were shown not to scale with height above the water surface in contrast to vertical velocity spectra for which such a variation was observed in the low frequency range in addition spectral peaks in the horizontal wind spectra were found at a frequency as low as 10 3 hz from a comparison with results from a previous study it was concluded that this turbulence is of the inactive kind being brought down from the upper parts of the boundary layer by pressure transport

the nature of small to medium earthquakes along the eastern mediterranean passive continental margins and their possible relationships to landslides and submarine salt tectonic related shallow faults

incorporation of stratification effects on the oceanic roughness length in the derivation of the neutral drag coefficient abstract based on the assumption that over the sea the roughness length of the wind profile scales with the wind stress a new formulation that describes the drag coefficient as a function of the given neutral drag coefficient and stability is derived the new formulation is compared to an earlier formulation where roughness changes with stability were ignored the two are then illustrated with data collected from both the marine remote sensing project 1979 and the tower ocean wave and radar dependence experiment 1984 it was found that when the surface roughness was allowed to depend on wind stress and therefore stability the stratification correction to the neutral drag coefficient was larger than for the case when the roughness length was not allowed to vary

comment on a study of the slope probability density function of the ocean waves from radar observations by d hauser et al 1 intermediate scale waves isw about 0 02 to 6 m long are the main contributor of the ocean surface roughness relevant to passive and active microwave remote sensing of the ocean while wind speed is the most important parameter determining the spectral composition of the ocean surface roughness analysis of field measurements indicates that the wave spectrum of isw is strongly modified by background waves the mean square slope derived from the wave spectrum is therefore also modified by the background wave condition investigation of ocean surface roughness without taking into account the sea state parameter can lead to incorrect conclusions 2 the paper by hauser et al 2008 hereinafter referred to as hcgm08 presented very interesting results on the properties of ocean surface roughness derived from c band 5 35 ghz radar observations they compared the filtered mean square slope obtained under the assumption of gaussian probability density function pdf of surface slopes with three published spectral models their interpretation of the empirical spectral model of hwang 2005 hereinafter referred to as h05 is inaccurate as a result they attributed the disagreement between their data with h05 to the discontinuity in the h05 spectrum caused by matching the empirically parameterized intermediate scale wave isw spectrum and an assumed equilibrium spectrum for the longer waves the issue of matching will be further discussed in section 2 their description on the comparison with h05 was verbal hcgm08 p 9 the result is shown in figure 1 here the analyses of hcgm08 produced two sets of mean square slope mss as a function of wind speed based on the assumption of gaussian shown in their figure 6d and nongaussian their figure 11b surface slope pdf they have noticed the large difference between the two sets of mss but no further comment or explanation was offered derivation of ocean surface roughness from radar backscattering cross section is a complex topic extensive discussions on the subject have been given in earlier publications e g jackson et al 1992 walsh et al 1998 results of mss computation using essentially the same approach of hcgm08 by jackson et al 1992 for ku band 14 ghz andwalsh et al 1998 for ka band 36 ghz are also shown in figure 1 together with the sun glitter data of cox and munk 1954 and the filtered mss of h05 spectral model integrated to an upper cutoff wave number kc suggested by jackson et al 1992 this cutoff wave number corresponds to surface wavelength about 4 7 times the radar wavelength the cutoff wave number used by hcgm08 is much higher corresponding to surface wavelength about 2 2 times the radar wavelength for their c band radar frequency 5 35 ghz kc is 24 rad m on the basis of the criterion of jackson et al 1992 and 51 rad m on the basis of hcgm08 also shown in their figure 1 are the filtered mean square slope derived from direct inversion of the backscattering cross section of ka band radar reported by vandemark et al 2004 further discussion of these data is deferred to section 3 3 after a close examination of their experimental conditions it becomes clear that the source of disagreement is quite different from that suggested by hauser et al and the hint was in fact given in h05 that is the mean square slope of the ocean surface is significantly modified by background waves hcgm08 did not provide too much information about the wind and wave conditions of their experiment however on the basis of the tabulated data presented in an earlier paper of the same experiment mouche et al 2005 the wavefields are strongly influenced by swell not related to the local wind condition in contrast the database used in constructing the h05 spectrum is wind sea dominant with mild swell presence section3 because radar remote sensingplays an increasingly more important role in oceanographic research and environmental monitoring and that an accurate interpretation of the remote sensing measurement requires a correct understanding of the ocean surface roughness in response to various geophysical parameters of interest such as wind air sea stability condition waves of various scales and currents of various sources a clarification of the properties of the ocean surface roughness spectrum is important i hope this note serves to correct the misinterpretation given by hauser et al 2008 regarding the ocean surface roughness spectrum and to call attention the important role of a missing parameter the background wave condition in their analysis

the southern ocean waves experiment part i overview and mean results the southern ocean waves experiment sowex was an international collaborative air sea interaction experiment in which a specially instrumented meteorological research aircraft simultaneously gathered atmospheric turbulence data in the marine boundary layer and sea surface topography data over the southern ocean for a wide range of wind speeds the aim was to increase present knowledge of severe sea state air sea interaction this first paper presents an overview of the experiment and a detailed discussion of the methodology and mean results a companion paper describes the findings on variability of the wind speed and wind stress and their relationship to variations in the underlying sea surface roughness

wind and waves in extreme hurricanes waves breaking at the ocean surface are important to the dynamical chemical and biological processes at the air sea interface the traditional view is that the white capping and aero dynamical surface roughness increase with wind speed up to a limiting value this view is fundamental to hurricane forecasting and climate research but it has never been verified at extreme winds here we show with observations that at high wind speeds white caps remain constant and at still higher wind speeds are joined and increasingly dominated by streaks of foam and spray at surface wind speeds of 40 m s the streaks merge into a white out the roughness begins to decrease and a high velocity surface jet begins to develop the roughness reduces to virtually zero by 80 m s wind speed rendering the surface aero dynamically extremely smooth in the most intense part of extreme or major hurricanes wind speed 50 m s a preliminary assessment shows that cross swell dominant in large regions of hurricanes allows the roughness under high wind conditions to increase considerably before it reduces to the same low values

environmental regime change at around 500 bce found in sediment cores from lake yogo japan possible impact of agricultural use abstract lake sediments record past environmental changes mineral grain size fluctuations found in sediment cores from the deepest basin of lake yogo located north of lake biwa are a good proxy for annual precipitation back to about 700 ce when a hydrological regime shift is postulated this study reports water organic matter and biogenic silica contents and grain size for an additional core from lake yogo and together with a detailed chronological study published elsewhere a new age model is established based on this new age model we propose that the hydrological regime shift occurred about 2500 years ago agricultural use of the catchment area might be responsible for this regime shift and resulted in the large overall average grain size several traces of disastrous events possibly caused by earthquakes in the region are also found in the core

multilevel tower observations of vertical eddy diffusivity and mixing length in the tropical cyclone boundary layer during landfalls abstractthis study analyzes the fast response 20 hz wind data collected by a multilevel tower during the landfalls of tropical storm lionrock 1006 typhoon fanapi 1011 and typhoon megi 1015

insights on the source of the 28 september 2018 sulawesi tsunami indonesia based on spectral analyses and numerical simulations the 28 september 2018 sulawesi tsunami has been a puzzle because extreme deadly tsunami waves were generated following an mw 7 5 strike slip earthquake while such earthquakes are not usually considered to produce large tsunamis here we obtained processed and analyzed two sea level records of the tsunami in the near field pantoloan located inside the palu bay and far field mamuju located outside the palu bay and conducted numerical simulations to shed light on the tsunami source the two tide gauges recorded maximum tsunami trough to crest heights of 380 and 24 cm respectively with respective dominating wave periods of 3 6 4 4 and 10 min and respective high energy wave duration of 5 5 and 14 h the two observed waveforms were significantly different with wave amplitude and period ratios of 16 and 3 respectively we infer tsunamigenic source dimensions of 3 4 4 1 km and 32 5 km for inside and outside of the palu bay respectively our numerical simulations fairly well reproduced both tsunami observations in pantoloan and mamuju except for the arrival time in mamuju however it was incapable of reproducing the maximum reported coastal amplitudes of 6 11 m it is possible that these two sources are different parts of the same tectonic source a bay oscillation mode of 85 min was revealed for the palu bay through numerical modeling actual sea surface disturbances and landslide generated waves were captured by two video recordings from inside the palu bay shortly after the earthquake it is possible that a large submarine landslide contributed to and intensified the sulawesi tsunami we identify the southern part of the palu bay around the latitude of 0 82os as the most likely location of a potential landslide based on our backward tsunami ray tracing analysis however marine geological data from the palu bay are required to confirm such hypothesis

directional wave spectra measured with the surface contour radar abstract the surface contour radar is a 36 ghz computer controlled airborne radar which generates a false color coded elevation map of the sea surface below the aircraft in real time and can routinely produce ocean directional wave spectra with post flight data processing which has much higher angular resolution than pitch and roll buoys when compared with waveriders and the xerb and edeco pitch and roll buoys there is good agreement among the nondirectional spectra there is also good agreement among the angles associated with a1 b1 and a2 b2 fourier coefficients of the spreading function for xerb endeco and the surface contour radar there are indications that the pitch and roll buoys in this study may have calibration problems with the magnitudes of the fourier coefficients of the spreading function and that the radar system determines the fourier coefficients with significantly less noise and bias the high spatial resolution and rapid mapping capability over extensive areas make the surface

a new opportunity to detect paleo earthquake events dating back to the past 10 millennia a record from lacustrine sediment bulk density and grain density profiles of the uppermost 90 cm portion of lacustrine sediment from lake suigetsu one of the five major lakes of lake mikatagoko located in central japan indicate the occurrence of at least 10 depositional events characterized by anomalously high density spikes two events are accompanied by turbidites the dates of the sedimentary events estimated here are correlated with the occurrence of destructive earthquakes since 1100 a d close examination of the sedimentological signatures recorded in the lake sediment and historical literature describing destructive earthquake phenomena provides a new opportunity to detect paleo earthquake events in a high seismic area having a long history

estimating palaeo water depth from the physical rock record abstract palaeo water depth and its change with time is a key factor in environmental analysis and in sedimentology in general the literature published on this topic and on related subjects however is substantial albeit scattered within and between different communities geologists oceanographers engineers physicists etc here i focus on proxies for palaeo bathymetry as obtained from the physical rock record floral faunal and chemical evidence for palaeo water depth being equally important must be dealt with elsewhere an assessment of the main depth related parameters in actualistic settings is presented and their applicability to the fossil sedimentary record discussed the outcome reveals the full complexity of this topic there is for example no such thing as an average wave base depth applicable to a wide range of fossil case settings this because wave and current climates in general and particularly so in neritic and coastal settings are intriguingly complex furthermore observations from modern oceans are not a priori applicable to fossil ones acknowledging these problems and limitations critically evaluated quantitative proposals for depth indicative facies and features in the sedimentary record are presented and error bars discussed

mass movement induced tsunami hazard on perialpine lake lucerne switzerland scenarios and numerical experiments previous studies of the sediments of lake lucerne have shown that massive subaqueous mass movements affecting unconsolidated sediments on lateral slopes are a common process in this lake and in view of historical reports describing damaging waves on the lake it was suggested that tsunamis generated by mass movements represent a considerable natural hazard on the lakeshores newly performed numerical simulations combining two dimensional depth averaged models for mass movement propagation and for tsunami generation propagation and inundation reproduce a number of reported tsunami effects four analysed mass movement scenarios three based on documented slope failures involving volumes of 5 5 to 20 8 106 m3 show peak wave heights of several metres and maximum runup of 6 to 10 m in the directly affected basins while effects in neighbouring basins are less drastic the tsunamis cause large scale inundation over distances of several hundred metres on flat alluvial plains close to the mass movement source areas basins at the ends of the lake experience regular water level oscillations with characteristic periods of several minutes the vulnerability of potentially affected areas has increased dramatically since the times of the damaging historical events recommending a thorough evaluation of the hazard

visual demonstration of three scale sea surface roughness under light wind conditions during the southern ocean waves experiment sowex an aircraft carried a down looking video camera to help document the sea surface reflected images of the aircraft were intermittently observed in the video recorded at 15 30 m height under light and variable wind conditions a numerical simulation was developed to relate image contrast to the gravity capillary wave contribution to sea surface mean square slope mss carnival fun house mirror type distortions of the image in the absence of the gravity capillary waves relate to intermediate scale wave persistence when wind forcing stops video image estimates of mss correlated better with 36 ghz scanning radar altimeter estimates than with the wind speed measured at 30 m height when the gravity capillary waves disappeared in the absence of wind forcing about one third of the 0 0015 residual mss was contributed by the dominant waves and about two thirds was contributed by the 1 10 m wavelength region near the shores of a lake in alaska reflected aircraft images were also observed indicating that the gravity capillary wave contribution to mss was only about 0 000 001 even though the wind speed at the 160 m aircraft height was 10 m s

slumping and shallow faulting related to the presence of salt on the continental slope and rise off north carolina abstract seismic reflection profiles and long and medium range sidescan sonar were used to investigate a salt diapir complex and area of slope instability near the base of the continental slope off north carolina within the area of investigation three diapirs are bounded on their upslope side by a scarp 60 m high and 50 km long the slope above the scarp is characterized by a series of shallow rotational normal faults the bottom below the scarp is furrowed by slide tracks which were probably carved by large blocks that broke off the scarp face and slid downslope leaving rubble and scree lobes extensive slumping in this area appears to be a result of uplift and faulting associated with salt intrusion which has fractured and oversteepened the slope leading to instability and failure sharply defined slide tracks suggest that slope failure above the breached diapir complex is a continuing process in contrast to much of the surrounding slope area where few instability features were observed

ormen lange an integrated study for the safe development of a deep water gas field within the storegga slide complex ne atlantic continental margin executive summary abstract a great effort has been undertaken to investigate potential geohazards in relation to the development of the ormen lange gas field offshore mid norway the field is located in the scar left after the giant tsunami generating storegga slide which occurred roughly 8150 years ago and the slide risk has consequently received particular focus the studies have been multi disciplinary in character and have involved a number of companies universities and research institutions the results of the project have lead to a significant advance in our understanding of the storegga slide in particular and submarine slope instability in general and played an important role in the approval of field development by norwegian authorities this special issue comprises 26 individual contributions in addition to this representing the wide span of topics addressed in the project and this introductory paper gives a brief summary of their contents

a note on nearshore wave features implications for wave generation abstract this paper analyses 10 years of wave data from the mediterranean spanish catalan coast considering the mean wave climate and storm events from the standpoint of wind wave momentum transfer and wave prediction the data registered by a buoy at about 12 km from the coastline revealed two main groups of wave storms with nw and e directions nw storms correspond to a fetch limited situation since the intense wind blows from land low pressure centres located over the mediterranean sea produce easterly storms near the coast the eastern winds from the sea are replaced by nw winds coming from meteorological patterns over northern spain and south western france wave storms are classified and studied to obtain their main features including spectral width wave length wave age and bimodality and discussed in terms of wind wave momentum transfer for operational wave predictions observations show a complex coastal wave climate fetch limited storms presented smaller spectral widths while varying wind situations presented larger widths due to the presence of bimodal spectra these wave features are highly relevant for wind ocean momentum transfer and thus for current and wave predictions the spectral width proved to be a good indicator of sea complexity and is thus applicable for improved wind drag estimations a new drag coefficient formulation is proposed based on existing wind dependent drag expressions but including also spectral wave properties a spectral width parameter that highlights the characteristics of wind wave generation under pre existing swell such a formulation once properly validated with field observations is expected to improve wind wave predictions

observations of sea surface mean square slope under light wind during the tropical ocean global atmosphere coupled ocean atmosphere response experiment observations of sea surface mean square slope mss were made with a scanning radar altimeter sra from a low flying research aircraft on a light wind day during the tropical ocean global atmosphere coupled ocean atmosphere response experiment wind speed measured at 60 to 90 m height and extrapolated to the 10 m level and mss were found to be positively correlated with correlation coefficients in some cases as high as those obtained for wind speed measurements on adjacent aircraft flying wingtip to wingtip with a 100 m lateral separation of their fuselages the sra measurements suggest a much larger azimuthal asymmetry in mss at 36 ghz than was observed in the seminal cox and munk optical experiment the sra measurements showed a crosswind to upwind ratio as low as of 0 26 at 1 8 m s 1 compared to the typical value of 0 8 for cox and munk for higher wind speed the mss becomes more isotropic the data suggest that waves generated by a wind speed less than 2 m s 1 are restricted to the downwind direction the crosswind to upwind ratio would probably have been even lower had it not been for an isotropic background mss caused by an assortment of swell

revisiting the definition of the drag coefficient in the marine atmospheric boundary layer abstract a new functional form of the neutral drag coefficient for moderate to high wind speeds in the marine atmospheric boundary layer for a range of field measurements as reported in the literature is proposed this new form is found to describe a wide variety of measurements recorded in the open ocean coast fetch limited seas and lakes with almost one and the same set of parameters this is the result of a reanalysis of the definition of the drag coefficient in the marine boundary layer which finds that a constant is missing from the traditional definition of the drag coefficient the constant arises because the neutral friction velocity over water surfaces is not directly proportional to the 10 m wind speed a consequence of the transition to rough flow at low wind speeds within the rough flow regime the neutral friction velocity is linearly dependent on the 10 m wind speed consequently within this rough regime the new definition of the drag coefficient is not a function of the wind speed

surficial sediment failures due to the 1929 grand banks earthquake st pierre slope a mw 7 2 earthquake centred beneath the upper laurentian fan of the sw newfoundland continental slope triggered a damaging turbidity current and tsunami on 18 november 1929 the turbidity current broke telecommunication cables and the tsunami killed 28 people and caused major infrastructure damage along the south coast of newfoundland both events are believed to have been derived from sediment mass failure as a result of the earthquake this study aims to identify the volume and kinematics of the 1929 slope failure in order to understand the geohazard potential of this style of sediment failure ultra high resolution seismic reflection and multibeam swath bathymetry data are used to determine 1 the dimension of the failure area 2 the thickness and volume of failed sediment 3 fault patterns and displacements and 4 styles of sediment failure the total failure area at st pierre slope is estimated to be 5200 km2 recognized by escarpments debris fields and eroded zones on the seafloor escarpments are typically 20 100 m high suggesting failed sediment consisted of this uppermost portion of the sediment column landslide deposits consist mostly of debris flows with evidence of translational retrogressive sliding in deeper water 1700 m and evidence of instantaneous sediment failure along fault scarps in shallower water 730 1300 m two failure mechanisms therefore seem to be involved in the 1929 submarine landslide faulting and translation the main surficial sediment failure concentrated along the deep water escarpments consisted of widely distributed translational retrogressive failure that liquefied to become a debris flow and rapidly evolved into a massive channelized turbidity current although most of the surficial failures occurred at these deeper head scarps their deep water location and retrogressive nature make them an unlikely main contributor to the tsunami generation the localized fault scarps in shallower water are a more likely candidate for the generation of the tsunami but further research is needed in order to address the characteristics of these fault scarps

comparison of model predictions with measurements of ku and ka band near nadir normalized radar cross sections of the sea surface from the genesis and rapid intensification processes experiment a comparison of model predictions with measurements of near nadir normalized radar cross sections nrcss of the sea surface at ku and ka bands is reported measurements of airborne precipitation radar second generation apr 2 from near nadir to 25 incidence angle along with simultaneous wind truth from dropsonde observations are compared with predictions of the cutoff invariant two scale model of sea scattering with the overall goal of assessing the model for possible future use in the apr 2 calibration process the performance of the model as a function of wind speed and incidence angle is therefore emphasized the measured data set acquired primarily during the 2010 genesis and rapid intensification processes grip experiment includes wind speeds from approximately 5 to 45 m s model comparisons are limited by uncertainties in the wind fields due to limited dropsonde coverage the data set is separated into more reliable containing wind speeds of 5 20 m s and less reliable wind speeds of 5 45 m s wind truth categories accordingly because a model of the sea spectrum is required for cutoff invariant model predictions comparisons with measured data are performed for three differing sea spectrum descriptions it is found that a bias of less than 1 db over the wind speed range 5 40 m s and a standard deviation less than 1 db over the wind speed range 10 40 m s can be achieved when using the unified sea spectrum description of elfouhaily the model also provides error levels that are near uniform with respect to both incidence angle and wind speed

the fetch experiment an overview the flux etat de la mer et teledetection en conditions de fetch variable fetch was aimed at studying the physical processes associated with air sea exchanges and mesoscale oceanic circulation in a coastal region dominated by frequent strong offshore winds the experiment took place in march april 1998 in the northwestern mediterranean sea gulf of lion observations were collected with the r v l atalante with an air sea interaction spar asis buoy with waverider buoys and with research aircraft equipped for in situ and remote sensing measurements the present paper is an introduction to the following special section which groups 12 papers including this one presenting results on turbulent flux measurements at the ocean surface on the behavior of the marine atmospheric boundary layer on the ocean waves characteristics on the ocean circulation and on remote sensing of surface parameters this overview presents the background and objectives of fetch the experimental setup and operations and the dominant atmospheric and oceanic conditions and introduces the different papers of the special section

preconditioning and triggering of offshore slope failures and turbidity currents revealed by most detailed monitoring yet at a fjord head delta rivers and turbidity currents are the two most important sediment transport processes by volume on earth various hypotheses have been proposed for triggering of turbidity currents offshore from river mouths including direct plunging of river discharge delta mouth bar flushing or slope failure caused by low tides and gas expansion earthquakes and rapid sedimentation during 2011 106 turbidity currents were monitored at squamish delta british columbia this enables statistical analysis of timing frequency and triggers the largest peaks in river discharge did not create hyperpycnal flows instead delayed delta lip failures occurred 8 11 h after flood peaks due to cumulative delta top sedimentation and tidally induced pore pressure changes elevated river discharge is thus a significant control on the timing and rate of turbidity currents but not directly due to plunging river water elevated river discharge and focusing of river discharge at low tides cause increased sediment transport across the delta lip which is the most significant of all controls on flow timing in this setting