schmidt hammer exposure age dating shd performed on periglacial and related landforms in opplendskedalen geirangerfjellet norway implications for mid and late holocene climate variability schmidt hammer exposure age dating shd was applied to a variety of boulder dominated periglacial landforms in an attempt to establish a local mid late holocene chronology for the geirangerfjelle

size distributions and failure initiation of submarine and subaerial landslides abstract landslides are often viewed together with other natural hazards such as earthquakes and fires as phenomena whose size distribution obeys an inverse power law inverse power law distributions are the result of additive avalanche processes in which the final size cannot be predicted at the onset of the disturbance volume and area distributions of submarine landslides along the u s atlantic continental slope follow a lognormal distribution and not an inverse power law using monte carlo simulations we generated area distributions of submarine landslides that show a characteristic size and with few smaller and larger areas which can be described well by a lognormal distribution to generate these distributions we assumed that the area of slope failure depends on earthquake magnitude i e that failure occurs simultaneously over the area affected by horizontal ground shaking and does not cascade from nucleating points furthermore the downslope movement of displaced sediments does not entrain significant amounts of additional material our simulations fit well the area distribution of landslide sources along the atlantic continental margin if we assume that the slope has been subjected to earthquakes of magnitude 6 3 regions of submarine landslides whose area distributions obey inverse power laws may be controlled by different generation mechanisms such as the gradual development of fractures in the headwalls of cliffs the observation of a large number of small subaerial landslides being triggered by a single earthquake is also compatible with the hypothesis that failure occurs simultaneously in many locations within the area affected by ground shaking unlike submarine landslides which are found on large uniformly dipping slopes a single large landslide scarp cannot form on land because of the heterogeneous morphology and short slope distances of tectonically active subaerial regions however for a given earthquake magnitude the total area affected by subaerial landslides is comparable to that calculated by slope stability analysis for submarine landslides the area distribution of subaerial landslides from a single event may be determined by the size distribution of the morphology of the affected area not by the initiation process

paraglacial rock slope stability glaciation and deglaciation along with their associated climatic and non climatic processes modify slope stresses and influence slope stability paraglacial slope failures are those that are a part of or influenced by the transition from glacial conditions to non glacial conditions gravitational failure of rock slopes is a primary and dominant process of slope evolution in mountainous terrain and is the subject of this paper which 1 reviews the approaches taken for researching paraglacial rock slope failure patterns and processes 2 summarises the spatial and temporal patterns of post glacial failures 3 assesses the factors influencing slope stability during glaciation and deglaciation 4 explores some of the applications of paraglacial research and 5 highlights some of the outstanding issues to be resolved and provides recommendations for terminology relating to paraglacial slope processes

landslides and climate change in the italian dolomites since the late glacial abstract the paper deals with the relationship between the temporal occurrence of landslides and climatic changes in the italian dolomites since the late glacial after an introduction on the state of the art with particular reference to the alpine region the results of recent investigations in the two study sites are illustrated at cortina d ampezzo several landslides were dated mainly by the radiocarbon method the most ancient landslide event there involved large rock slides which affected the dolomitic slopes following the withdrawal of glaciers after the last glacial maximum lgm and also slides and flows mainly occurring in pelitic materials of the valley floors from 13 000 to 10 000 cal bp a later series of flows occurred between 5500 and 2500 cal bp in the upper badia valley alta badia the most ancient events go back to 10 000 and 9000 cal bp and correspond with earth flows that followed vast rotational slides affecting the bedrock up to a depth of about 50 m more recent earth flows involving more modest amounts of material took place between 6500 and 2300 cal bp by analysing the dates from the two study areas it was possible to correlate the recorded increase of landslide activity with the climatic changes occurring at the boundary between the late glacial and the holocene and between the atlantic and the subboreal and to compare the results with those derived from other european regions the types and causes of landslides taking place in these two periods were substantially different reflecting the different morphoclimatic conditions that existed in the two areas when these mass movements were triggered finally notwithstanding the importance of non climatic causes such as geological structural factors and possible human influences it is concluded that many of the dated landslides can be considered as indicators of climatic change

rock slope instabilities in sogn and fjordane county norway a detailed structural and geomorphological analysis rock slope failures form a frequent hazard to many populated mountain regions especially in western norway the topographical and meteorological characteristics increase the vulnerability for rock slope failures a major focus for studies in norway is to eciently nd and investigate possible future rock slope failures in order to prevent extensive humanitarian disasters the determination of the critical parameters involved in the development of rock slope failures is crucial in order to optimize hazard recognition in addition a better understanding of the spatial and temporal variability of prehistoric and historic rock slope failures as well as present day rock slope instabilities will optimize monitoring and further research on the susceptibility for future rock slope failures the primary aim of this study is to investigate the spatial and temporal distribution of rock slope instabilities within western norway it is further aimed to determine the controlling parameters on the development of rock slope instabilities within the study region the implemented approaches range from regional scale statistical analyses towards site specic numerical modelling while a focus is set on quantitative analyses within this thesis the main controlling parameters are dened for rockfalls and rock slope instabilities on a regional scale for the entire county of sogn fjordane western norway it is demonstrated that always a combination of several parameters is necessary to destabilize a mountain side rockfalls have the strongest spatial relation to the presence of bare rock as well as landslide deposits the degree of tectonic deformation and the geological lineament density large rock slope instabilities develop preferentially within relatively weak rock units such as phyllites or weathered mac gneisses and at convex slope breaks looking more into detail a strong structural control is conrmed by numerical modelling for the unstable rock slope at stampa susceptibility and hazard are assessed at dierent scales and with dierent measures quantitative rockfall susceptibility is mapped on a regional scale for the entire county of sogn fjordane based on the statistical analysis of a set of controlling factors in addition this statistical susceptibility model is combined with a physically based model restricting the susceptibility map to areas that are steep enough to represent a potential rockfall source this combination allows using road inventories with registered impact points instead of release areas for susceptibility modelling in contrast relative susceptibility and also hazard are assessed locally for single parts of the unstable rock slope at stampa based on morphology and past activity present day annual expectable frequencies for rock slope failures of certain volume classes are determined for the storfjord region in western norway based on magnitude frequency analyses furthermore a semi quantitative hazard estimation is obtained for each potential instability based on a qualitative susceptibility assessment of each instability in this region this phd thesis presents results of the rst attempts of quantitative statistical analyses of dierent inventories covering rock slope instabilities in norway it is shown that susceptibility and hazard can be assessed with dierent measures forming the basis for further decisions regarding risk assessment and mitigation

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

database and online map service on unstable rock slopes in norway from data perpetuation to public information abstract the unstable rock slope database is developed and maintained by the geological survey of norway as part of the systematic mapping of unstable rock slopes in norway this mapping aims to detect catastrophic rock slope failures before they occur more than 250 unstable slopes with post glacial deformation are detected up to now the main aims of the unstable rock slope database are 1 to serve as a national archive for unstable rock slopes in norway 2 to serve for data collection and storage during field mapping 3 to provide decision makers with hazard zones and other necessary information on unstable rock slopes for land use planning and mitigation and 4 to inform the public through an online map service the database is organized hierarchically with a main point for each unstable rock slope to which several feature classes and tables are linked this main point feature class includes several general attributes of the unstable rock slopes such as site name general and geological descriptions executed works recommendations technical parameters volume lithology mechanism and others displacement rates possible consequences as well as hazard and risk classification feature classes and tables linked to the main feature class include different scenarios of an unstable rock slope field observation points sampling points for dating displacement measurement stations lineaments unstable areas run out areas areas affected by secondary effects along with tables for hazard and risk classification and url links to further documentation and references the database on unstable rock slopes in norway will be publicly consultable through an online map service factsheets with key information on unstable rock slopes can be automatically generated and downloaded for each site areas of possible rock avalanche run out and their secondary effects displayed in the online map service along with hazard and risk assessments will become important tools for land use planning the present database will further evolve in the coming years as the systematic mapping progresses and as available techniques and tools evolve

moored wind temperature and current observations made during coastal ocean dynamics experiments 1 and 2 over the northern california continental shelf and upper slope moored observations of winds currents and temperature made over the northern california shelf and upper slope during the 1981 and 1982 upwelling seasons as part of the coastal ocean dynamics experiment code are described in both field experiments code 1 and code 2 the onset of the upwelling season is triggered by the strengthening of the north pacific high off northern california and signalled by the presence of water colder than 9 c near the bottom over the shelf vertical temperature stratification over the shelf is reduced during active upwelling local winds and subtidal currents over the shelf are strongly polarized in the alongshelf direction and the mean wind stress is directed equatorward response of alongshelf currents to wind forcing is similar at all depths over the shelf the response of the cross shelf current is more complex in the surface layer offshelf flow is significantly and positively correlated with the upwelling favorable alongshelf wind stress beneath this layer a weak return flow exists the thickness of the upper mixed layer varies greatly reaching 60 m during upwelling events thus direct wind forcing affects a substantial fraction of the water over the shelf low frequency wind stress current and temperature fields are adequately described by a few energetic empirical orthogonal functions with simple spatial structure the most energetic mode typically accounts for 75 or more of the variance of wind stress and temperature over the middle and inner shelf the most energetic current mode accounts for 90 or more of the variance is dominated by he alongshelf component and veers to the left with depth the low frequency alongshelf flow fluctuations are quasi barotropic with some vertical shear but no reversal with depth vertical shear in alongshelf current and the cross shelf density gradient obey the thermal wind relation the simple structure of the subdiurnal currents allow estimation of the alongshelf volume transport between the 60 and 130 m isobaths through three cross shelf transects in code 2 volume transport over the shelf is often nearly two dimensional but occasional large differences indicate significant mass exchange between the shelf and the adjacent upper slope correlation of low frequency currents and alongshelf wind stress shows the response of alongshelf current to be maximum near the surface and near midshelf where a 15 cm 1 alongshelf flow lags a 1 dyn cm 2 alongshelf wind stress by the order of 10 hours currents over the upper slope are not significantly correlated with local wind alongshelf transport over the shelf is highly correlated with local wind stress explaining 80 of the variance in the low frequency transport during code 2 volume transport is best correlated with wind stress approximately 30 km to the south winds in the code area during spring and summer are characterized by strong and persistent upwelling favorable winds interrupted by shorter periods of weak winds regression analysis indicates that in the absence of wind a poleward barotropic current jet exists over the shelf with a maximum amplitude over the inner shelf in the code area an upwelling favorable wind counters this jet over the shelf so that the alongshore flow is everywhere equator ward during strong wind events since the maximum response to wind forcing is found at midshelf and near surface the mean current over the upwelling season is strongly sheared in both the vertical and cross shelf directions mean flow over the outer shelf is surface intensified and is directed offshelf and equatorward while the deeper flow at midshelf and through most of the water column over the inner shelf is directed poleward

postglacial uplift neotectonics and seismicity in fennoscandia abstract fennoscandia has experienced major uplift in postglacial time which is assumed to reflect a glacial isostatic process connected to the melting of the last ice sheets extensive modelling of the isostatic movements show that the applied deglaciation and uplift model fit the observations well there are however areas with significant deviations between uplift measurements and regional model predictions the misfit between observations and the isostatic uplift modelling is interpreted here to reflect a tectonic component of the uplift the objective of the present investigation is to isolate this tectonic uplift component interestingly enough the areas found partly correspond to areas with pronounced seismic activity and the assumption that the postglacial rebound is responsible for much of the observed onshore seismicity is substantiated we conclude that there seems to be present day deformation along the shoreline of mid norway southern norway shoreline and mountain areas and along the swedish east coast with the centre northeast of the gulf of bothnia that cannot be explained by glacial isostasy not all of the deformations in these areas are necessarily co seismic the study suggests that such vertical deformations are small in magnitude and overprint the glacial rebound the deformations may be a consequence of the plio pleistocene erosional pattern which is of glacial origin

a linear stratified ocean model of the coastal undercurrent the linear stratified ocean model of mccreary 1981 is used to study the wind driven response of the ocean near an eastern coast the model can be regarded as an extension of the inviscid models of lighthill 1969 and of gill clarke 1974 that allows the vertical diffusion of heat and momentum into the deep ocean solutions are still found as expansions of vertical normal modes vertical mixing affects each mode as a linear drag with a drag coefficient that increases rapidly with mode number n a zonally uniform band of steady equatorward winds forces the ocean and the resulting flow field has many features in common with observations at eastern boundaries there is a surface equatorward jet and a poleward coastal undercurrent confined within 10 20 km of the coast both currents extend well poleward of the wind band upwelling does not reach great depths but occurs only above the core of the undercurrent weak downwelling occurs at greater depths there is offshore ekman drift in the surface mixed layer and return flow at a depth slightly above the core of the undercurrent the baroclinic alongshore pressure gradient field and the vertical mixing of heat and momentum are essential elements of the model dynamics but the beta and horizontal mixing are not low order vertical modes n 6 tend toward a two dimensional balance they generate the transverse circulation pattern associated with coastal ekman pumping

analyses of past and present rock slope instabilities in a fjord valley implications for hazard estimations abstract for quantitative hazard assessment it is necessary to define the magnitude frequency distribution and a temporal model of the landslide frequency this is often complicated for large rock slope failures due to the lack of significant numbers of large rock slope failures in inventories of a given homogeneous region or sparse information about the timing an inventory of 108 rock slope failure deposits within the fjords of the storfjord region including a relative rockslide chronostratigraphy was available for this study the temporal distribution of rock slope failures is characterized by a rapid response with a high frequency of failures directly after deglaciation followed by a lower constant frequency since 9 000 years bp for the entire storfjord region the largest recorded volumes failed directly after deglaciation volumes larger than 5 10 6 m 3 have not been recorded within the last 9 000 years in addition 17 rockslide scars and on the other hand 17 potential rock slope instabilities have been mapped at the northeastern flank of tafjord which is a branch of the storfjord volume frequency relations have been developed for the three inventories from tafjord comprising i fjord deposits ii rockslide scars and iii potential instabilities they result in very similar distributions over the entire volume range all three inventories are underlying the same processes that lead to destabilisation and finally failure additionally the compilation of the three inventories is independent and based on different methodologies the similarity of the volume frequency distributions is thus verifying the different inventories hence the obtained volume frequency relation can be used to assess the rockslide hazard for the study area present day annual expectable frequencies for different volume classes have been assessed based on the obtained volume frequency relation of the fjord deposits for example the average annual frequency for rock slope failures of v 1 10 6 m 3 originating from the northeastern flank of tafjord is 1 1670 based on a lognormal distribution this regional hazard can be used to improve previously existing qualitative susceptibility rankings for potential unstable rock slopes within the tafjord region the resulting probabilities are very low however the uncertainties of all hazard estimates are very high

from incipient slope instability through slope deformation to catastrophic failure different stages of failure development on the ivasnasen and vollan rock slopes western norway abstract the long term evolution of rock slope failures involves different stages from incipience of slope instability to catastrophic failure through a more or less long lasting slope deformation phase that also involves creeping or sliding topography lithology and structural inheritance are the main intrinsic factors that influence this evolution here we investigate the role of these intrinsic factors on the rock slope failure development of the ivasnasen and vollan rock slopes sunndal valley western norway using a multitechnique approach that includes geomorphologic and structural field mapping kinematic analysis terrestrial cosmogenic nuclide exposure dating topographic reconstruction and deformation quantification ivasnasen is a rock slope failure complex with several past rock slope failures and a present unstable rock slope located on a cataclinal nw facing slope and developed in augen gneiss vollan on the opposite valley side is a deep seated gravitational slope deformation dsgsd affecting the whole mountainside developed in quartzite in the upper part and micaschist in the lower part these different lithologies belong to different nappe complexes that were emplaced and folded into a series of syn and anticlines during the caledonian orogeny these folds lead to different lithologies being exposed in different structural orientations on the opposite valley flanks which in turn leads to different types and evolution of rock slope failures at ivasnasen the 45 55 nw dipping ductile foliation allowed for a fairly simple planar sliding mechanism for the 1 2 million m 3 post glacial rock slope failure failure occurred ca 3 3 ka ago after a short period of prefailure deformation for the present 2 2 million m 3 unstable rock slope at ivasnasen a steepening of the foliation at the toe impedes such a mechanism and up to 10 m of displacement has not lead to a catastrophic failure yet the vollan dsgsd is characterized by a steep major back scarp with its up to 130 m wide graben which opened along the subvertical foliation in the quartzite and a conspicuous array of counter scarps in the micaschist the morphologic features are explained by a flexural toppling mechanism in the micaschist which likely initiated in the lower slope section and propagated retrogressively until reaching the massive quartzite at the back scarp flexural toppling cannot solely explain the total along slope displacement of up to 200 m i e an elongation of 28 creep along a basal shear zone which may have developed in the hinge zone of the flexural toppling combined with shallow valley dipping joints likely accounts for the large elongation implications of this study for the hazard assessment of unstable rock slopes in norway include the relatively rapid development of instabilities in cataclinal slopes and the important insights on long term displacement rates gained from cosmogenic nuclide dating for a better understanding of the evolution of unstable rock slopes

analyzing complex rock slope deformation at stampa western norway by integrating geomorphology kinematics and numerical modeling abstract the unstable rock slope stampa above the village of flam norway shows signs of both active and postglacial gravitational deformation over an area of 11 km 2 detailed structural field mapping annual differential global navigation satellite system gnss surveys as well as geomorphic analysis of high resolution digital elevation models based on airborne and terrestrial laser scanning indicate that slope deformation is complex and spatially variable numerical modeling was used to investigate the influence of former rockslide activity and to better understand the failure mechanism field observations kinematic analysis and numerical modeling indicate a strong structural control of the unstable area based on the integration of the above analyses we propose that the failure mechanism is dominated by 1 a toppling component 2 subsiding bilinear wedge failure and 3 planar sliding along the foliation at the toe of the unstable slope using differential gnss 18 points were measured annually over a period of up to 6 years two of these points have an average yearly movement of around 10 mm year they are located at the frontal cliff on almost completely detached blocks with volumes smaller than 300 000 m 3 large fractures indicate deep seated gravitational deformation of volumes reaching several 100 million m 3 but the movement rates in these areas are below 2 mm year two different lobes of prehistoric rock slope failures were dated with terrestrial cosmogenic nuclides while the northern lobe gave an average age of 4 300 years bp the southern one resulted in two different ages 2 400 and 12 000 years bp which represent most likely multiple rockfall events this reflects the currently observable deformation style with unstable blocks in the northern part in between joasete and furekamben and no distinct blocks but a high rockfall activity around ramnanosi in the south with a relative susceptibility analysis it is concluded that small collapses of blocks along the frontal cliff will be more frequent larger collapses of free standing blocks along the cliff with volumes 100 000 m 3 thus large enough to reach the fjord cannot be ruled out a larger collapse involving several million m 3 is presently considered of very low likelihood

a description of subtidal pressure field observations on the northern california continental shelf during the coastal ocean dynamics experiment during the coastal ocean dynamics experiment code along the northern california continental shelf in the spring and summer of 1981 and 1982 the first comprehensive effort to obtain all of the observations necessary to infer pressure fluctuations throughout the water column was made this is a description of the subtidal fluctuations in measured bottom pressure internal pressures inferred from moored conductivity and temperature observations and the water column total pressure anomalies computed from a combination of the two components the pressure field during code 2 april july 1982 is found to be more energetic than that in code 1 april july 1981 with more than 70 total pressure variance concentrated at frequencies of less than 15 days 1 the spatial structure of the pressure fluctuation field is characterized by coastal intensification and a tendency for poleward phase propagation like the pressures most of the code across shelf pressure difference variance is found at the lower frequencies with more than 60 of the total across shelf pressure difference variance at frequencies of less than 15 days 1 the code across shelf pressure differences are found to be in geostrophic balance with both alongshelf currents and the total alongshelf transport the alongshelf pressure difference variance is generally found to be concentrated at the lower frequencies much like that of the across shelf pressure differences most of the pressure and pressure difference variance is found to be highly coherent with wind stress the 20 day band pressure variability is apparently related to the response of the pressure field during so called relaxation events the barotropic component of the alongshelf geostrophic transport i e across shelf pressure difference has been found to be almost perfectly coherent with regional wind stress y and to propagate poleward within the code region at the same rate as y and the alongshelf pressure gradient is very important in accelerating the alongshelf flow the 5 day band pressure variability in the code region appears to result from local wind stress fluctuations the alongshelf pressure gradient was found to be of secondary importance relative to the wind in accelerating the alongshelf flow

on the influence of wind stress curl on low frequency shelf water flow abstract an approximate solution for wind driven near barotropic flow over the continental shelf is obtained the solution shows that a wind stress with amplitude that increases offshore and then is relatively constant as observed during the coastal ocean dynamics experiments code results in two types of shear the horizontal shear is associated with the offshore increase of the wind stress which strengthens the flow the vertical shear is associated with the alongshore wind stress amplitude and its first two offshore derivatives for a wind stress structure similar to the one observed during code the dominant vertical shear is associated with 2 y x2 where y is the alongshore wind stress and x is the distance seaward from the coast physically 2 y x2 nonzero means that the surface ekman pumping will vary with x tilt isopycnals and produce a vertical shear in the alongshore velocity in accordance with the thermal wind relation the near barotropic solution for the alongshore velocity field

surface exposure dating of the flims landslide graubunden switzerland abstract sixteen boulder and bedrock surfaces related to the flims landslide volume 8 12 km3 were dated with 36cl and 10be exposure ages range from 4900 250 yr to 15 440 1480 yr including corrections made due to snow cover and karst erosion ages of 11 410 590 yr and 13 340 1090 yr were obtained on bedrock surfaces outside of the landslide zone these are minima for deglaciation of segnes valley and provide constraints on possible amounts of inherited nuclides based on seven boulder ages which range from 8200 260 to 9520 990 yr a mean of 8900 700 years is calculated for the flims landslide we exclude three outliers one significantly older and two significantly younger than the others and the ages from the cassons bedrock site from the mean calculation the latter is excluded as shielding due to snow and vegetation cover is difficult to constrain there the oldest boulder on the landslide yielded an age 15440 1480 yr more than 5000 years older than any other boulder age suggesting that it included the surface of the pre slide bedrock the exposure ages are consistent with a single failure event the erratics and patches of till lying on the landslide debris must have been carried piggy back on top of the landslide rather than having been deposited by the late pleistocene vorderrhein glacier the flims rockslide is about the same age as the kofels 9800 yr and kandertal 9600 yr rockslides all three occurred during the marked transition to warmer wetter conditions during the early holocene

exhaustion and steady state models for predicting landslide hazards in the canadian rocky mountains abstract the temporal distribution of landslides can be evaluated by steady state and exhaustion models the probability of landsliding remains constant through time in the steady state model but the probability decreases in the exhaustion model as more slopes fail rock sliding down bedding surfaces on overdip slopes exhausts hazardous sites to leave stable dipslope landforms in kananaskis country in the canadian rocky mountains the distribution of rock slides in this area can be better explained by the exhaustion model than by the steady state model

numerical model simulations of continental shelf flows off northern california abstract the three dimensional circulation on the continental shelf off northern california in the wind events and shelf transport west experiment region during summer 2001 is studied using the primitive equation regional ocean modeling system roms the simulations are performed with realistic topography and initial stratification in a limited area domain with a high resolution grid forcing consists of measured wind stress and heat flux values obtained from a west surface buoy the general response shows a southward coastal upwelling jet of up to 1 m s 1 and a weakening or reversal of currents inshore of the jet when upwelling winds relax model results are compared to west moored velocity and temperature measurements at five locations to codar surface current observations between pt reyes and bodega bay and to hydrographic measurements along shipboard survey lines the model performs reasonably well with the highest depth averaged velocity correlation 0 81 at the inshore mooring 40 m water depth and lowest correlation 0 68 at the mid depth mooring 90 m depth the model shows generally stronger velocities than those observed especially at the inshore moorings and a lack in complete reversal of southward velocities observed when upwelling winds relax the comparison of surface velocities with codar measurements shows good agreement of the mean and the dominant mode of variability the hydrography compares closely at the southern and northern edges of the survey region correlation coefficients between 0 90 and 0 97 with weaker correlations at the three interior survey lines correlation coefficients between 0 44 and 0 76 mean model fields over the summer upwelling period show slight coastal jet separation off pt arena and significant separation off pt reyes the cape regions also experience relatively strong bottom velocities and nonlinearity in the surface flow across shelf velocity sections examined along the shelf reveal a double jet structure that appears just north of bodega bay and shows the offshore jet strengthening to the south we examine the dynamics during an upwelling and subsequent relaxation event in may 2001 in which the west measurements show evidence of a strong flow response the alongshelf variability in the upwelling and relaxation response introduced by pt reyes is evident analysis of term balances from the depth averaged momentum equations helps to clarify the event dynamics in different regions over the shelf a clear pattern in the nonlinear advection term is due to the spatial acceleration of the southward jet around the capes of pt arena and pt reyes during upwelling results from a three dimensional lagrangian analysis of water parcel displacement show significant southward displacement in the coastal jet region including a strong signal from the double jet alongshelf variability in parcel displacements and upwelling source waters due to the presence of pt arena and pt reyes is also apparent from the lagrangian fields a cyclonic eddy like recirculation feature offshore of pt arena prior to the upwelling event causes large patches of onshore displaced parcels additionally across shelf variability in the response of water parcels along the d line includes decreased vertical displacement and increased alongshelf displacement in the offshore direction

the role of material properties and landscape morphology on landslide size distributions abstract it has been observed that landslide size distribution shows power law scaling for large landslide areas with a roll over for landslides below a certain threshold which frequently coincides with the modal peak of the distribution the physical reasons leading to this distribution are not yet fully understood the analysis of non cumulative size distribution of two landslide inventories in the italian alps confirms the existence of a power law scaling with exponent of 2 56 0 02 and demonstrates that the roll over is not due to under sampling since it occurs at landslide sizes significantly larger than mapping resolution the control of topography on landslide size distribution is investigated by a topographic analysis using the virtual tiling method we observe a power law scaling of topography with a roll over for finer scales which is comparable with that of landslide size distribution the control of material properties on landslide size and geometry is examined through deterministic and probabilistic 2d limit equilibrium slope stability analyses incoherent materials favour shallow landslides with no limitation in size cohesive materials favour deep landslides and show a limitation for small sizes multilayered materials with depth dependent strength show a limitation for both small and large landslides the joint probability of 1 the probability that a slope with a given size and slope gradient is unstable i e failure probability from probabilistic stability analysis and 2 the probability that a slope with a given size and slope gradient exists topographic analysis allows to build synthetic size distributions which show both power law scaling and roll over for multilayered materials we obtain a scaling exponent of the power law of 2 58 0 02 we suggest that the power law scaling in landslide size distribution results in the study area from the constraint of topography and the presence of multilayered materials or depth dependent strength the roll over is an intrinsic characteristic of the size distribution due to the contribution of cohesion to slope stability

examples of multiple rock slope collapses from kofels otz valley austria and western norway abstract this paper describes the effects of large massive rock slope failures on subsequent slope stability three examples of large rock slope failures from the austrian alps and norway demonstrate that failure increases the probability of further collapses at kofels austria a holocene rock slope failure several km3 in size filled the otz valley the morphology of the deposits indicates that at least one subsequent failure occurred along the head scarp of the first failure most likely a slide of similar size debris of the second landslide slid over the older deposits forming the famous kofels frictionite at least three rock slope failures all of them in excess of 106 m3 occurred from the same mountainside within the last 6000 8000 years at tafjord in western norway the most recent of these failures in 1934 triggered a destructive tsunami five large failures with volumes 50 000m3 occurred at ramnefjell norway within 50 years two of them caused considerable damage and a large number of death due to the formation of destructive tsunamis two dimensional finite element models of rock slope stability before and after the kofels and tafjord landslides show that massive rock slope failures produce a irregular slopes parts of which are as steep or steeper than the slope before failure and which represent new zones of instability and b zones of weakness related to slow slope deformation and related cracking

climatic implications of reconstructed early mid pliocene equilibrium line altitudes in the mcmurdo dry valleys antarctica early mid pliocene moraines in the mcmurdo dry valleys antarctica are more extensive than the present alpine glaciers in this region indicating substantial climatic differences between the early mid pliocene and the present to quantify this difference in the glacier climate regime we estimated the equilibrium line altitude ela change since the early mid pliocene by calculating the modern ela and reconstructing the elas of four alpine glaciers in wright and taylor valleys at their early mid pliocene maxima the area altitude balance ratio method was used on modern and reconstructed early mid pliocene hypsometry in wright and victoria valleys mass balance data identify present day elas of 800 1600 ma s l and an average balance ratio of 1 1 the estimated elas of the much larger early mid pliocene glaciers in wright and taylor valleys range from 600 to 950 170 m a s l and thus are 250 600 170 m lower than modern elas in these valleys the depressed elas during the early mid pliocene most likely indicate a wetter and therefore warmer climate in the dry valleys during this period than previous studies have recognized

the role of a longshore pressure gradient in pacific northwest coastal dynamics abstract in this paper we demonstrate the importance of the seasonal barotropic longshore pressure gradient force to pacific northwest coastal dynamics values of the seasonal longshore pressure gradient corrected for gauge height relative to a level surface hickey and pola 1982 and for year to year variations enfield and alien 1980 were included in the two dimensional time dependent baroclinic finite difference model of hamilton and rattray 1978 as an external force observed wind stress stratification and bottom topography were included in the model and comparisons were made with current meter data in each of the three seasonal situations observed in the northwest pressure gradient force southward opposing local wind stress winter pressure gradient force northward opposing local wind stress summer and pressure gradient force and local wind stress both southward spring three important features of the seasonal circulation are shown to depend on the existence of the pressure gradient

geological model of the aknes rockslide western norway abstract aknes is known as the most hazardous rockslide area in norway at present and is among the most investigated rockslides in the world representing an exceptional natural laboratory this study focuses on structural geology and the usage of geophysical methods to interpret and understand the structural geometry of the rockslide area the interpretations are further used to build a geological model of the site this is a large rockslide with an estimated volume of 35 40 million m 3 derron et al 2005 defined by a back scarp a basal shear zone at about 50 m depth and an interpreted toe zone where the sliding surface daylights the surface the rockslide is divided into four sub domains experiencing extension in the upper part and compression in the lower part structural mapping of the area indicates that the foliation of the gneiss plays an important role in the development of this rockslide the upper boundary zone of the rockslide is seen as a back scarp that is controlled by and parallel to the pre existing steep foliation planes where the foliation is not favourably orientated in regard to the extensional trend the back scarp follows a pre existing fracture set or forms a relay structure the foliation in the lower part dipping 30 to 35 to s sse seems to control the development of the basal sliding surface with its subordinate low angle trust surfaces which daylights at different levels the sliding surfaces are sub parallel to the topographic slope and are located along mica rich layers in the foliation geophysical surveys using ground penetrating radar gpr refraction seismic and 2d resistivity profiling give a coherent understanding of undulating basal sliding surface in the subsurface the geophysical surveys map the subsurface in great detail to a depth ranging from 30 40 m for gpr to approximately 125 m for refraction seismic and 2d resistivity profiling this gives a good control on the depth and lateral extent of the basal sliding surface and its subordinate low angle thrusts drill cores and borehole logging add important information with regard to geological understanding of the subsurface fracture frequency fault rock occurrences geophysical properties and groundwater conditions both in outcrops and or drill cores constrain the geometrical and kinematic model of aknes rockslide

runout analysis of a large rockfall in the dolomites italian alps using lidar derived particle sizes and shapes lidar data were used to quantify and analyse a rockfall event which occurred in 2003 in the western dolomites italian alps in addition to previously existing airborne laserscanning als data high resolution terrestrial laserscanning tls data were collected by using the original point clouds the volume axial ratio and runout length of single boulders as well as the surface roughness in the runout zone of the rockfall were derived the total volume of the rockfall event of approximately 10 000 m was estimated by a reconstruction of the pre event surface at the detachment zone the analysis of the laser scanning data of the accumulation zone revealed a power law scaling for boulder volumes larger than 8 m the dependence of runout length on boulder volume is complex it is moderated by particle sphericity in addition we used als and tls data to derive the spatial distribution of surface roughness on the talus cone tls allow for more accurate roughness mapping than als data but for most applications the point density of als data seems to be sufficiently high to derive measures of roughness different sampling approaches for plane fitting on the scale of 5 m did not show significant effects besides the computational time the results of our analyses provide important perspectives for rockfall modelling and process understanding with potential applications in both applied natural hazards and pure geomorphological research copyright 2012 john wiley sons ltd

size distribution of submarine landslides along the u s atlantic margin abstract assessment of the probability for destructive landslide generated tsunamis depends on the knowledge of the number size and frequency of large submarine landslides this paper investigates the size distribution of submarine landslides along the u s atlantic continental slope and rise using the size of the landslide source regions landslide failure scars landslide scars along the margin identified in a detailed bathymetric digital elevation model dem have areas that range between 0 89 km2 and 2410 km2 and volumes between 0 002 km3 and 179 km3 the area to volume relationship of these failure scars is almost linear inverse power law exponent close to 1 suggesting a fairly uniform failure thickness of a few 10s of meters in each event with only rare deep excavating landslides the cumulative volume distribution of the failure scars is very well described by a log normal distribution rather than by an inverse power law the most commonly used distribution for both subaerial and submarine landslides a log normal distribution centered on a volume of 0 86 km3 may indicate that landslides preferentially mobilize a moderate amount of material on the order of 1 km3 rather than large landslides or very small ones alternatively the log normal distribution may reflect an inverse power law distribution modified by a size dependent probability of observing landslide scars in the bathymetry data if the latter is the case an inverse power law distribution with an exponent of 1 3 0 3 modified by a size dependent conditional probability of identifying more failure scars with increasing landslide size fits the observed size distribution this exponent value is similar to the predicted exponent of 1 2 0 3 for subaerial landslides in unconsolidated material both the log normal and modified inverse power law distributions of the observed failure scar volumes suggest that large landslides which have the greatest potential to generate damaging tsunamis occur infrequently along the margin

statistical analysis of rockfall volume distributions implications for rockfall dynamics we analyze the volume distribution of natural rockfalls on different geological settings i e calcareous cliffs in the french alps grenoble area and granite yosemite cliffs california sierra and different volume ranges i e regional and worldwide catalogs contrary to previous studies that included several types of landslides we restrict our analysis to rockfall sources which originated on subvertical cliffs for the three data sets we find that the rockfall volumes follow a power law distribution with a similar exponent value within error bars this power law distribution was also proposed for rockfall volumes that occurred along road cuts all these results argue for a recurrent power law distribution of rockfall volumes on subvertical cliffs for a large range of rockfall sizes 102 1010 m3 regardless of the geological settings and of the preexisting geometry of fracture patterns that are drastically different on the three studied areas the power law distribution for rockfall volumes could emerge from two types of processes first the observed power law distribution of rockfall volumes is similar to the one reported for both fragmentation experiments and fragmentation models this argues for the geometry of rock mass fragment sizes to possibly control the rockfall volumes this way neither cascade nor avalanche processes would influence the rockfall volume distribution second without any requirement of scale invariant quenched heterogeneity patterns the rock mass dynamics can arise from avalanche processes driven by fluctuations of the rock mass properties e g cohesion or friction angle this model may also explain the power law distribution reported for landslides involving unconsolidated materials we find that the exponent values of rockfall volume on subvertical cliffs 0 5 0 2 is significantly smaller than the 1 2 0 3 value reported for mixed landslide types this change of exponents can be driven by the material strength which controls the in situ topographic slope values as simulated in numerical models of landslides densmore et al 1998 champel et al 2002 index terms 5104 physical properties of rocks fracture and flow 1815 hydrology erosion and sedimentation 8122 tectonophysics dynamics gravity and tectonics

entrainment of debris in rock avalanches an analysis of a long run out mechanism many rock avalanches entrain and liquefy saturated soil from their paths evidence for this includes mud displaced from the margins of rock avalanche deposits substrate material smeared along the base of deposits extrusion of liquefied soil upward through the deposits and increases of volume a hypothesis first suggested in 1881 and since reinforced by several authors suggests that entrainment of substrate material increases mobility although the process has been discussed in the literature for more than 100 years few detailed and quantitative descriptions exist the main purpose of this paper is to describe two recent cases from british columbia canada where rockslides entrained substrate on a very large scale influencing the character of the events estimated volume balance curves based on detailed field mapping are provided for both cases dynamic analyses are carried out using a numerical model and using the same set of rheological parameters the mechanism of material entrainment and displacement is discussed the data suggest that rapid rock failures entraining very large quantities of saturated substrate material represent a special type of landslide transitional between rock avalanche and debris avalanche many rock avalanches can thus be seen as end members of a continuum of phenomena involving rock failure followed by interaction with saturated substrate

rock slope failure following late pleistocene deglaciation on tectonically stable mountainous terrain the ages of 31 postglacial rock slope failures rsfs in scotland and nw ireland derived from 89 cosmogenic isotope exposure ages are employed to analyse the temporal pattern of failure and its relationship to the timing of deglaciation rates of glacio isostatic crustal uplift and periods of rapid climate change rsf ages span almost the whole period since ice sheet retreat from 18 2 1 2 ka to 1 7 0 2 ka or from 17 1 1 0 ka to 1 5 0 1 ka depending on the production rate used in 10 be age calculation but catastrophic failure of rock slopes was w4 6 times more frequent prior to w11 7 ka than during the holocene 95 of dated rsfs at sites deglaciated during retreat of the last ice sheet occurred within w5400 years after deglaciation with peak rsf activity 1600e1700 years after deglaciation this time lag is inferred to represent 1 stress release initiated by deglacial unloading leading to 2 time dependent rock mass strength degradation through progressive failure plane development and ultimately 3 to either spontaneous kinematic release or failure triggered by some extrinsic mechanism by contrast 11 dated rsfs at sites reoccupied by glacier ice during the younger dryas stade yds of w12 9e11 7 ka exhibit no clear temporal pattern suggesting that glacial reoccupance during the yds was ineffective in preconditioning a renewed cycle of enhanced rsf activity comparison of timing of individual rsfs with that of deglaciation and rapid warming events at w14 7 ka and w11 7 ka suggests that glacial debuttressing enhanced joint waterpressuresduringdeglaciationandthawofpermafrosticeinrockjointscouldhavetriggeredfailurein only a small number of cases conversely the timing of maximum rsf activity following ice sheet deglaciation corresponds broadly with maximum rates of glacio isostatic crustal uplift suggesting that the two are linked by enhanced seismic activity a seismic failure trigger is consistent with full slope failure at all sites where failure planes are clearly defined our results indicate that numerous rsfs must have occurred in areas that were reoccupied by glacier ice during the yds but have not been identified because runout debris was removed by yds glaciers more generally they provide the first reliably dated body of evidence to support the view that retreat of the last ice sheets in tectonically stable mountainous terrain initiated a period of enhanced rock slope failure due to deglacial unloading and probably lateglacial seismic activity implying that most undated rsfs in such areas are probably of lateglacial or veryearly holocene age they also demonstrate however that a low frequency of rsf activity extended throughout the holocene

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

equilibrium structure and dynamics of the california current system this paper addresses the structure and dynamical mechanisms of regional and mesoscale physical variability in the subtropical northeast pacific ocean using the regional oceanic modeling system roms the model is configured with a u s west coast domain that spans the california current system ccs with a mesoscale horizontal resolution up to as fine as 3 5 km its mean seasonal forcing is by momentum heat and water fluxes at the surface and adaptive nudging to gyre scale fields at the open water boundaries its equilibrium solutions show realistic mean and seasonal states and vigorous mesoscale eddies fronts and filaments the level of eddy kinetic energy eke in the model is comparable to drifter and altimeter estimates in the solutions with sufficiently fine resolution because the model lacks nonseasonal transient forcing the authors conclude that the dominant mesoscale variability in the ccs is intrinsic rather than transiently forced the primary eddy generation mechanism is the baroclinic instability of upwelling alongshore currents there is progressive movement of meanseasonal currents and eddy energy offshore and downward into the oceanic interior in an annually recurrent cycle the associated offshore eddy heat fluxes provide the principal balance against nearshore cooling by mean ekman transport and upwelling the currents are highly nonuniform along the coast with important influences by capes and ridges in both maintaining mean standing eddies and launching transient filaments and fronts

a modeling study of shelf circulation off northern california in the region of the coastal ocean dynamics experiment 2 simulations and comparisons with observations 1 this is the second part of a modeling study of wind forced flow on the continental shelf off northern california in the region 37 40 n of the coastal ocean dynamics experiment code gan and allen 2002 analyzed the shelf flow response to idealized wind stress forcing in a process oriented study the study here applies forcing from observed winds and heat flux for april may 1982 and compares the model results with moored current and temperature measurements the princeton ocean model pom is used in a three dimensional limited area domain with a high resolution curvilinear grid approximately 1 km horizontal spacing 60 vertical levels and realistic coastline and bottom topography the objectives of the study are to simulate the response of the shelf circulation field to time varying observed wind stress and heat flux to compare model results with oceanographic observations to establish confidence in the model and to subsequently analyze the model fields and the model dynamical balances to help understand the behavior of the observed flow the model variables show overall good agreement with corresponding observations similar to the conclusions by gan and allen 2002 it is found that the alongshore variability of upwelling is mainly controlled by the interaction of the wind forced shelf flow with the coastline and bottom topography different dynamical regimes in the regions north and south of the coastal capes formed by pt reyes and pt arena and in the more uniform region between these capes are identified and investigated the results demonstrate that the coastal capes play a dominant role in causing alongshore variability of the upwelling flow including the setup of an alongshore pressure gradient that forces northward currents during relaxation of southward upwelling favorable winds an analysis of the balance of terms in the equation for potential temperature indicates that across shore temperature advection is the major contributor to the cooling of coastal water during upwelling with a larger magnitude to the south of the capes to the north of the capes however alongshore temperature advection is the dominant contributor to the colder water near the coast

detailed dem analysis of a rockslide scar to characterize the basal sliding surface of active rockslides 1 the basal sliding surfaces in large rockslides are often composed of several surfaces and possess a complex geometry the exact morphology and location in three dimensions of the sliding surface remains generally unknown in spite of extensive field and subsurface investigations such as those at the aknes rockslide western norway this knowledge is crucial for volume estimations failure mechanisms and numerical slope stability modeling this paper focuses on the geomorphologic characterization of the basal sliding surface of a postglacial rockslide scar in the vicinity of aknes this scar displays a stepped basal sliding surface formed by dip slopes of the gneiss foliation linked together by steeply dipping fractures a detailed characterization of the rockslide scar by means of high resolution digital elevation models permits statistical parameters of dip angle spacing persistence and roughness of foliation surfaces and step fractures to be obtained the characteristics are used for stochastic simulations of stepped basal sliding surfaces at the aknes rockslide these findings are compared with previous models based on geophysical investigations this study discusses the investigation of rockslide scars and rock outcrops for a better understanding of potential rockslides this work identifies possible basal sliding surface locations which is a valuable input for volume estimates design and location of monitoring instrumentation and numerical slope stability modeling

relaxation from upwelling in the coastal ocean dynamics experiment a relaxation of the upwelling system on the northern california shelf occurs when upwelling favorable winds decay or reverse observations from the coastal ocean dynamics experiment are used to investigate this process with emphasis on the near surface temperature evolution models of relaxation warming are tested for the surface layer 0 30 m over midshelf with the result that the surface heat flux and poleward alongshelf advection can account for the observed temperature behavior onshore advection of the upwelled isopycnal field is a relatively unimportant contribution the warming patterns that are observed and which provide the gradients for the advective process have wedgelike shapes warmest inshore and in the south of the experimental area these patterns appear to be related to a topographic influence of point reyes possibly through the generation of gradients in the wind field remote advection of warm water from as far south as san francisco occasionally occurs as well the nature of the relaxation mechanism has general implications a new warm saline nutrient rich water mass may be formed in the surface layer since the warming processes are not the reverse of the cooling an important asymmetry is present it causes time variable upwelling to generate conditions very different from steady upwelling a new upwelling front is created during each event with upwelled water seaward of it and reversed alongshelf flow contributes to the warming and exchange mechanisms the system cannot be described or understood without the irreversible processes during upwelling and relaxation or without a mixed layer

a comparison of empirical and dynamical hindcasts of low frequency wind driven motions over a continental shelf three approaches to hindcasting low frequency wind driven shelf currents bottom pressure and adjusted sea level are compared at two locations along the west coast of the united states the purely empirical approach is a multiple input linear regression in which alongshelf wind stress records at various time lags are fit to the observations the empirical fowe first order wave equation approach assumes the dynamics of a single wind forced frictionally damped coastal trapped wave and adjusts the choice of free wave phase speed and frictional decay time to produce the best hindcast of the oceanographic observable the dynamical fowe approach uses the full theory of wind forced long coastal 1 rapped waves to hindcast observables with no adjustment of the free wave parameters to improve the fit the results are similar for both hindcast locations the purely empirical approach produces the best fit in a least squares sense but offers little dynamical insight at both locations using more than two wind records one local and one 500 km to the south does not significantly improve the hindcast the other two approaches perform nearly as well as the purely empirical approach however the empirical fowe approach can lead to dynamical inconsistencies because the optimal phase speed may be different for different variables or for the same variable observed at different cross shelf locations further local forcing along with remote forcing can bias the results leading to lower phase speed and friction time estimates than are appropriate for the remotely forced signal the dynamical fowe approach offers the most physical insight and produces results which are consistent between variables and at different cross shelf locations further it is the only approach of the three which can be used as a true forecasting tool its performance is however also degraded by strong local forcing suggesting that more dynamical sophistication is required

subaqueous rock avalanche deposits exposed by post glacial isostatic rebound innfjorddalen western norway abstract this paper presents a detailed description of deposits and landforms of multiple rock avalanches in western norway one of which fell onto water saturated sediments in innfjorddalen below the former water level deposits of the latter are now exposed on the valley floor due to post glacial isostatic rebound at least three rock avalanches from the same source at grafonnfjellet mountain have occurred during late glacial and post glacial time and their deposits are distributed over an area of 1 44 km 2 in the valley these rock avalanches have volumes of 15 1 10 6 m 3 5 4 10 6 m 3 and 0 3 10 6 m 3 and yielded cosmogenic radionuclide 10 be ages of 14 3 1 4 ka 8 79 0 94 ka and 1 028 0 380 ka respectively the youngest event dates within uncertainty limits to a historic rock avalanche in the year 1611 12 ce the rock avalanches formed a stratified succession of deposits the rock avalanche deposits 1 38 m 2 have lobate forms have frontal rims and parallel ridges extend across the valley floor and up the opposite slope and form dams on the valley floor isolated hills comprised of rock boulders 0 61 km 2 interpreted to be toma hills are disconnected from the main rock avalanche deposits by a 520 m wide zone of deformed valley fill sediments trenches and a ground penetrating radar survey of these deposits indicate large scale deformation or liquefaction numerical runout modeling of the rock avalanches with the code dan3d supports the interpretation of their landforms and sources and highlights their runout behavior

seasonal cycles of currents temperatures winds and sea level over the northeast pacific continental shelf 35 n to 48 n seasonal cycles of coastal wind stress adjusted sea level asl shelf currents and water temperatures off the west coast of north america 35 n to 48 n are estimated by fitting annual and semiannual harmonics to data from 1981 1983 longer records 9 34 years of monthly asl indicate that these two harmonics adequately represent the long term monthly average seasonal cycle and that the current measurement period is long enough to estimate the seasonal cycles we characterize the differences between fall winter and spring summer as follows for fall winter monthly mean winds north of 35 n are northward for 3 6 months longer in the north than in the south south of 35 n the mean winds are near zero or weakly southward monthly mean alongshore currents are northward over midshelf and shelf break at all locations sampled at depths of 35 m and deeper and are associated with high coastal sea levels and relatively warm water temperatures for spring summer monthly mean wind stresses are southward at all latitudes for 3 6 months longer in the south than in the north sea levels are low and water temperatures are relatively cool monthly mean currents at 35 m depth over the shelf are southward for 1 6 months longer at the shelf break than over midshelf and longer in the north than in the south while the deeper currents are less southward or northward the magnitudes of the seasonal cycles of all variables are maximum between approximately 38 n and 43 n generally decreasing slightly to the north and greatly to the south at each location the seasonal cycle of the alongshore current from 35 m depth at midshelf leads the sea level slightly and both lead the wind stress and temperatures by 1 2 months the seasonal cycles of all variables show a south to north progression south leads north by 1 2 months at 48 n annual mean currents at 50 m depth over the shelf break oppose the annual mean wind northward wind and southward current similarly at 35 n annual mean currents at 35 m depth over both midshelf and shelf break are opposed to the annual mean wind southward wind and northward current from 35 n to 43 n both summer and winter regimes are dominated by strongly fluctuating currents

a modeling study of shelf circulation off northern california in the region of the coastal ocean dynamics experiment response to relaxation of upwelling winds 1 a two part modeling study of the wind forced flow on the continental shelf off northern california in the region 37 40 n of the coastal ocean dynamics experiment code is pursued this paper involves a process oriented study with idealized wind stress forcing gan and allen 2002 involves forcing with observed winds and heat flux for april may 1982 and comparison of model results with code observations a characteristic but previously unexplained response observed during code following the weakening or relaxation of southward upwelling favorable winds is the time dependent development of northward currents over the inner shelf next to the coast the presence of northward winds is not necessary for this occurrence the objective in this paper is to investigate the dynamics of the shelf flow response to upwelling wind relaxation events under idealized conditions in the basic case experiment a spatially uniform upwelling favorable southward wind stress of 0 1 pa is applied to the ocean initially at rest the stress is held constant for 10 days and then decreased linearly to zero over 3 days in response to the southward wind stress southward alongshore currents develop on the shelf accompanied by upwelling of cold dense water near the coast considerable spatial variability in the shelf flow clearly related to the alongshore variations in coastline and bottom topography is found the alongshore currents tend to separate from the coast south of capes and the coldest surface water is found at those locations as the winds decrease northward currents similar to those observed develop on the inner shelf next to the coast at many alongshore locations examination of the alongshore momentum balances shows that the northward currents are forced by a northward pressure gradient force associated with negative alongshore pressure gradients these pressure gradients are set up by the interaction of the wind forced flow with the alongshore variations in shelf topography in general negative alongshore pressure gradients intensified off pt reyes and pt arena by the gradient wind balance are found south of capes the negative pressure gradients geostrophically balance onshore flow at depth and upwelling is strengthened in these locations north of capes positive pressure gradients that are primarily in balance with nonlinear advective effects are found after the winds cease the forced across shelf circulation weakens and the resulting unbalanced negative pressure gradients south of the capes accelerate the alongshore currents northward processes with similar dynamics are found embedded in the more complex coastal ocean response to observed time varying winds by gan and allen 2002

a general model of paraglacial landscape response a unifying attribute of all forms of paraglacial response is that deglaciation results in the exposure of unstable or metastable sediment sources that are subsequently tapped by a wide variety of processes over a wide range of timescales the paraglacial period in different geomorphological contexts is therefore con ditioned by two variables glacially conditioned sediment release and rate of sediment reworking under steady state conditions the latter may be approximated by an exhaustion model in which sediment yield is related to the amount of remaining available sediment by a negative exponential function this model offers an approximation for the behaviour of primary paraglacial systems in which glacigenic sediment sources are not replenished the long term behaviour of secondary primarily uvial paraglacial systems in which sediment inputs include both in situ and reworked glacigenic sediment appears intrinsically more complex but consistent with an exhaustion model if initial sediment avai

dynamics of wind driven upwelling and relaxation between monterey bay and point arena local regional and gyre scale controls 1 in north and central california equatorward winds drive equatorward flows and the upwelling of cold dense water over the shelf during the midspring and summer upwelling season when the winds temporarily weaken the upwelling flows between point reyes and point arena relax becoming strongly poleward over the shelf analytical and numerical models are used to describe the effect of alongshore variability of winds bathymetry and basin scale pressure gradients on the strength of upwelling and its relaxation alongshore winds weaken to the south of point reyes and the shelf becomes narrower from point reyes to monterey bay both of these lead to reduced upwelling at and to the north of point reyes causing an alongshore gradient of temperature and density on the shelf these alongshore gradients lead to an along isobath pressure gradient over the shelf that drive the relaxation flows a simple analytical model is used to explain the dynamics magnitude and structure of the relaxation flows the modeling also suggests that the depth of origin of the upwelled waters and thus their temperature is controlled by the along isobath pressure gradient that exists over the continental slope this along slope pressure gradient is also responsible for the california undercurrent in this region this pressure gradient is not generated in a model of the californian coast extending from 32 n to 42 n and integrated for several months suggesting it is caused by dynamics whose spatial or temporal scales are larger than the californian coast and or longer than several months

planetary wave propagation off california and its effect on zooplankton abstract lagged correlation of dynamic height from the gappy california cooperative oceanic fisheries investigation calcofi with monthly san diego sea level for the period 1949 2001 shows that the dynamic height propagates westward at 4 10 cm s 1 about double the speed of the large scale low frequency rossby wave 2 2 cm s 1 ocean topography experiment topex poseidon jason 1 s along track sea level height estimates since january 1993 filtered interannually propagate westward at 4 3 cm s 1 verifying that observed westward propagation is about double that expected including the effect of the mean california current on the rossby wave propagation does not explain the discrepancy but rather slightly increases it if variations in the ocean depth in the calcofi region are also taken into account the westward propagation is still only about one half that observed standard theory therefore does not explain the observations because of the westward propagation interannual variations in alongshore ge

magnitude and frequency of rock falls and rock slides along the main transportation corridors of southwestern british columbia the two main transportation corridors of southwestern british columbia are subject to a range of rock slope movements rock falls rock slides and rock avalanches that pose significant risks to r

on subinertial flow in submarine canyons effect of geometry shelf break canyons on the west coast of canada and the united states have been observed to be regions of enhanced upwelling during southward currents compared to the surrounding shelf break most shelf break canyons from oregon north cross only part of the continental shelf cutting from the shelf break toward the coast but end on the continental shelf well below the mixed layer juan de fuca canyon on the other hand cuts the continental shelf from the slope to and actually continues into the strait of juan de fuca this difference in geometry has a very strong effect on the subinertial flow around the canyon model canyon shapes which include convergent bathymetric contours are constructed and motivated for juan de fuca canyon and a typical shelf break canyon geostrophic analytic solutions show that the in canyon flow in juan de fuca canyon is generated by first order geostrophic dynamics whereas in the majority of canyons of which astoria is an example in canyon flow is generated by higher order effects this difference is postulated to lead to the observed very deep upwelling over juan de fuca canyon compared to more moderate episodic upwelling over astoria canyon

a method for estimating wind driven frictional time dependent stratified shelf and slope water flow abstract friction the alongshore pressure gradient and time dependent effects are all of lowest order importance in the dynamics of wind driven fluctuating currents and sea levels on continental shelves previous work has shown that when all these effects are included the ocean response can be described by an infinite sum of coastal trapped waves whose amplitudes satisfy a fully coupled infinite set of forced first order wave equations we present a practical method for solving this coupled set of equations for general low frequency large scale wind stress forcing as input convergence properties of the solution are examined analytically for the same accuracy more modes are required to describe alongshore currents than sea level and fewer modes are required to describe barotropic than depth dependent motion as an example numerical calculations were carried out for a model of the west florida shelf the sea level field was effectively described by one mode but the alongshore velocity field was not

subtidal currents over the central california slope evidence for offshore veering of the undercurrent and for direct wind driven slope currents abstract in february 1991 an array of six current meter moorings was deployed for one year across the central california outer shelf and slope the main line of the array extended 30 km offshore of the shelf break out to water depths of 1400 m a more sparsely instrumented line displaced 30 km to the northwest extended 14 km offshore though shorter the northern line spanned similar water depths because the gradient of the topography steepened in the northern region a poleward flow pattern typical of the california undercurrent was seen across both lines in the array over most of the year the poleward flow was surface intensified in general the portion of the undercurrent that crossed the southern line had larger amplitudes and penetrated more deeply into the water column than the portion that crossed the northern line transport over the year ranged from 0 to 2 5 sverdrups sv poleward across the southern line 0 to 1 sv poleward across the northern line we suggest the difference in transport was caused by topographic constraints which tended to force the poleward flow offshore of the northern measurement sites the slope of the topography steepened too abruptly to allow the poleward flow to follow isobaths when currents were strong when current velocities lessened a more coherent flow pattern was seen across both lines in the array in general the poleward flow patterns in the undercurrent were not affected by local winds or by the local alongshore pressure gradient nor was a strong seasonal pattern evident rather unexpectedly a small but statistically significant fraction of the current variance over the mid and outer slope was driven by the surface wind stress an alongshelf wind stress caused currents to flow along the slope parallel to the wind field down to depths of 400 m below the surface and out to distances of 2 rossby radii past the shelf break the transfer functions were weak 3 4 cm s per dyn cm 2 but comparable to wind driven current amplitudes of 4 6 cm s per unit wind stress over the middle shelf equatorward alongshelf winds also caused water from 200 300 m over the slope to upwell onto the shelf as the surface water moved offshore

transport and retention in an upwelling region the role of across shelf structure abstract the paradox of upwelling is the relationship between strong wind forcing nutrient enrichment and shelf productivity here we investigate how across shelf structure in velocity and hydrography plays a role in the retention inshore and export offshore of particles such as nutrients plankton and larvae we examine the spatial structure of the coastal currents during wind driven upwelling and relaxation on the northern californian shelf the field work was conducted as part of the wind events and shelf transport west project a 5 year nsf coop funded study of the role of wind driven transport in shelf productivity off bodega bay northern california from 2000 to 2003 we combine shipboard velocity profiles adcp and water properties from hydrographic surveys during the upwelling season to examine the mean across shelf structure of the hydrography and velocity fields during three contrasting upwelling seasons and throughout the upwelling relaxation cycle we also present results from two winter seasons that serve as contrast to the upwelling seasons during all three upwelling seasons clear spatial structure is evident in velocity and hydrography across the shelf exemplified by current reversals inshore and the presence of a persistent upwelling jet at the shelf break this jet feature changes in structure and distance from the coast under different wind forcing regimes the jet also changes from the north of our region where it is a single narrow jet adjacent to the coast and to the south of our region where it broadens and at times two jets become evident we present observations of the california under current which was observed at the outer edge of our domain during all three upwelling seasons the observed across shelf structure could aid both in the retention of plankton inshore during periods of upwelling followed by relaxation and in the export of plankton offshore in the upwelling jet

giant landslides topography and erosion abstract distributions of slope angles in tectonically active mountain belts point to the development of threshold conditions where hillslopes attain a critical inclination or height at which they fail readily because of limitations in material strength it has been proposed that hillslopes adjust to rapid uplift and bedrock incision through an increase in the rate of relief limiting landsliding rather than gradual slope steepening here we test this concept by investigating the relationship between mean local relief h which we take to be a proxy of long term erosion rates e and the occurrence of over 300 of the largest v 10 8 m 3 terrestrial landslides on earth we find that nearly two thirds of these giant landslides have occurred in the steepest 5 of the earth s land surface where relief is close to its proposed upper strength limit they are primarily located in deeply incised valleys along fault bounded fringes of active mountain belts and in volcanic arcs this distribution coincides with areas of high long term erosion rates 4 mm yr 1 confirming that giant landslides contribute to rapid denudation of mountains most of the eroded volume is concentrated in the smallest but steepest parts of mountain belts and volcanic arcs first order estimates of minimum erosion rates accomplished by the largest landslides are 0 01 mm yr 1 these rates are between 1 and 10 of the late pleistocene to holocene mean erosion rates in a given area importantly the landslide erosion rates show a nonlinear increase with mean local relief suggesting that the contribution of giant landslides in total and per event increases significantly with increasing overall erosion rates however giant landslides also occur in areas of lower than average relief h 300 700 m irrespective of whether threshold hillslopes have developed or not factors contributing to these failures include soft rocks extensive low angle discontinuities high rates of fluvial bedrock incision and tectonically driven deformation and slope loading

timing and periodicity of paraglacial rock slope failures in the scottish highlands abstract many formerly glaciated mountains exhibit a high density of postglacial rock slope failures rsfs in the form of rockslides rock avalanches or deep seated gravitational slope deformations such rsfs are often termed paraglacial as they reflect pre conditioning by glaciation and deglaciation the temporal pattern of paraglacial rsfs is unknown we employ 47 cosmogenic isotope exposure ages obtained for 17 catastrophic rsfs in the scottish highlands to test models of changes in rsf frequency since deglaciation our results show that rsf activity spans almost the entire postglacial period from 17 ka until 1 5 ka and that the periodicity of sampled postglacial rsfs is statistically indistinguishable from a pattern of uniform periodicity 1 ka 1 our data do not conform to proposed models of declining rsf frequency with time elapsed since deglaciation but suggest that the temporal distribution of postglacial rsfs is best described by a combination of rapid response enhanced rsf frequency during or immediately after deglaciation followed by approximately constant periodicity our findings are consistent with near surface fracturing of rock when glacially induced confining stresses are removed causing some failures during or immediately after deglaciation and reducing other slopes to critical conditional stability so that failure is triggered by progressive rock mass weakening or by transient triggering mechanisms neither permafrost degradation thaw of ice in joints nor seismic activity offers a general explanation for triggering scottish rsfs but could be contributory in some cases the quasi constant periodicity inferred for holocene rsfs implies that the probability of rsfs in this seismically quiescent intraplate area has not changed in the past 10 ka and that further though infrequent catastrophic rsfs are likely to occur in the future

anatomy of the kitimat fiord system british columbia abstract the geomorphic complexity of the kitimat fiord system on the active margin of british columbia canada is analysed from several perspectives sub glacial landforms and sediments show that grounded ice exiting the fiord system at the last glacial maximum streamed down moresby trough towards the queen charlotte trough mouth fan after brief halts on the inner shelf grounded ice margins cleared the fiord threshold perhaps by c 15 5 ka cal yrs bp and certainly before 13 ka cal yrs bp just outside the fiords meltwater plumes deposited stratified glaciomarine sediments interbedded with submarine slides inside the fiords thick glaciomarine sediments were deposited and large transverse moraines formed during temporary halts in retreat several glacial outburst floods eroded the kitkiata moraine and deposited distinctive mud deposits postglacial sedimentation on fiord floors has been spatially variable drifts of mud 90 m thick corresponding with areas of low current velocity alternate with areas of non deposition and erosion corresponding with areas of high velocity the fiord system hosts more than a hundred morphologically diverse fan deltas that can be classified in the prior and bornhold 1989 1990 system submarine mass transport was most frequent immediately following ice retreat 15 5 11 5 ka cal yrs bp the largest event 1 2 km 3 involved failure of glaciomarine sediment on a submarine moraine at squally channel and consequent movement of material into the adjacent deep basin this event occurred post 13 ka cal yrs bp in the postglacial phase mass transport continued on a lesser scale up to the present day most intensively in kitimat arm from the perspective of glacial landforms postglacial sedimentation and mass transport this pacific active margin fiord system has some parallels with fiord systems on canada s east coast passive margin and with norwegian fiords but the intensive development of holocene fan deltas is strongly distinctive

the benner pass rock avalanche cluster suggests a close relation between long term slope deformation dsgsds and translational rock slides and catastrophic failure abstract in mountain ranges deep seated gravitational slope deformations dsgsds and extremely rapid mass wastings of rock 105 m3 in volume catastrophic rock slope failures crf are present yet their mutual relation is poorly documented near the brenner pass 1370 m asl in the eastern alps five catastrophic rock slope failures of medium to high grade metamorphites are clustered brenner pass cluster bpc and three of them are related to dsgsds the catastrophic rock slope failures involved volumes from 12 to 110 mm3 and show fahrboeschung angles of 10 27 numerical dating 14c 234u 230th suggests that all catastrophic slope failures of the bpc occurred between 13 5 and 6 2 ka three of the crf events may have occurred during the younger dryas 12 7 11 7 ka whereas two events occurred during the holocene backwater basins dammed up by the crfs range from 2 5 km2 ridnaun rock avalanche to 15 5 km2 stilfes rock avalanche three of the catastrophic rock slope failures are associated with and developed as a partial failure of a dsgsd this suggests that progressively slow deformation of slopes ultimately exceeded a stability threshold resulting in catastrophic rock slope failures the initial kinematic mechanisms of failure vary between large scale toppling wedge sliding and planar sliding and are strongly controlled by the structural setting of the slopes a direct connection of catastrophic mass wasting with specific palaeoclimatic conditions e g phases of enhanced precipitation is not indicated however this does not exclude specific meteorological situations e g occurrence of short term heavy rainfall that may have expedited slope instability and perhaps even triggered catastrophic events attempts to correlate catastrophic rock slope failures with specific palaeoclimatic regimes are still encumbered by substantial methodical uncertainties and imprecisions as well as the scarcity of dated crf events the mapped distribution of crfs unequivocally indicates that structural predisposition is the most significant long term control in forming crf clusters

fragmentation in the val pola rock avalanche italian alps 1 grain size data from the deposit of the 1987 val pola rock avalanche central italian alps are compared with data concerning rock avalanching rock fragmentation and comminution the weibull distribution fits a small part of the entire particle size distribution of debris samples with a mean value of the curve shape factor of 0 54 0 28 this is typical of multiple comminution or fragmentation with much shearing a fractal distribution fits over a greater size range computed fractal dimensions range between 1 3 and 3 2 within the deposit with average values of about 2 6 2 7 these values cover the range between the theoretical values of the plane of weakness model 1 97 and the pillar of strength model 2 84 and are close to the theoretical value for the constrained comminution model 2 58 these suggest that both texturally mature and immature deposits are present and that more than a single comminution process acted during the rock avalanche motion variation of the grain size distribution within the deposit and grain size segregation show as trends in the fractal dimension and arise from variation in the fragmentation process a variety of different physical and empirical laws suggest that 1 30 of the energy expended in the rock avalanche was consumed in fragmentation

hf radar observations of surface circulation off bodega bay northern california usa 1 two high frequency radar stations codar were installed along the northern california coast in may 2001 comparisons of radar data with acoustic doppler current profiler adcp current data and near surface drifter tracks indicate considerable agreement with minimum rms differences of order 0 05 0 15 m s and average drifter hf radar track separation rates of 5 3 km d radar data resolve the three main sources of intraseasonal current variability in the area 1 upwelling relaxation dynamics 2 tidal and diurnal forcing and 3 inertial currents subtidal fluctuations are the largest component of variability accounting for 45 75 of the variance wind driven dynamics are the dominant source of this subtidal variability 67 of subtidal variability both upwelling and relaxation periods exhibit consistent patterns of surface velocity with nearshore currents being slower and more poleward than offshore currents which are strongly equatorward analysis of tidal and inertial variability indicate that current fluctuations are polarized toward clockwise rotation and are generally weaker and more linearly polarized near the coast m2 tidal current ellipses switch direction of rotation at the shelf break suggesting the presence of internal tidal waves currents in all frequency bands are deflected and accelerated around pt reyes and there are indications of increased current variability and changes in flow direction near cordell bank the presence of considerable cross shore and alongshore gradients in the strength and direction of surface flow patterns and in particular weak poleward currents over the inner shelf could have important consequences for plankton retention in the area

magnitude frequency relation for rockfall scars using a terrestrial laser scanner abstract the analysis of the three dimensional rockfall scar geometry provides clues for the understanding of the failure mechanisms acting on cliffs of the conditioning factors and on the frequency of the events in this paper a supervised step by step methodology is presented for establishing the statistical magnitude frequency relation of rockfall scar volumes using a point cloud from terrestrial laser scanner tls data the methodology includes a procedure for identifying discontinuity surfaces calculating the areas of those which are exposed and the height of rockfall scars in the estimation of the rockfall scar volume a key issue is the consideration of the minimum spacing of the discontinuity sets to differentiate between step path surfaces and undulated ones having obtained the distributions of both the basal area and height of the scar across the slope the volume of the rockfall scars is calculated stochastically by multiplication of these two parameters by means of a monte carlo simulation both distributions of the basal area and of the rockfall scar volume are found to be power law with the exponent b ranging from 0 9 to 1 2 the relation obtained might be used as a first approach of rockfall magnitude frequency curves in large cliffs

transferability of a calibrated numerical model of rock avalanche run out application to 20 rock avalanches on the nuussuaq peninsula west greenland long run out rock avalanches are one of the most hazardous geomorphic processes and risk assessments of the potential threat they pose are often reliant on numerical modelling of their potential run out distance the development of such models requires a thorough understanding of past flow behaviour inferred from deposits emplaced by previous events despite this few records exist of multiple rock avalanches that occurred in conditions sufficiently consistent to develop a set of more generalised and hence transferrable rules we conduct field and imagery based mapping and use numerical modelling to investigate the emplacement of 20 adjacent rock avalanches on the southern flanks of the nuussuaq peninsula west greenland the rock avalanches run out towards the vaigat strait and are sourced from a range of coastal mountains of relatively uniform geology we calibrate a three dimensional continuum dynamic flow code volcflow with data from a modern well constrained event that occurred at paatuut ad 2000 the best fit model assumes a constant retarding stress with a collisional stress coefficient simulating run out to within 0 3 of that observed this calibration was then used to model the emplacement of deposits from five other neighbouring rock avalanches before simulating the general characteristics of a further 14 rock avalanche deposits on simplified topography our findings illustrate that a single calibration of volcflow can account for the observed deposit morphology of a uniquely large collection of rock avalanche deposits emplaced by a series of events spanning a large volume range although the prevailing approach of tuning models to a specific case may be useful for detailed back analysis of that event we show that more generally applied models even using a single pair of rheological parameters can be used to model potential rock avalanches of varied volumes in a region and therefore to assess the risks that they pose

comparison of observed and model computed low frequency circulation and hydrography on the new england shelf 1 the finite volume coastal ocean model fvcom is configured to study the interannual variability of circulation in the gulf of maine gom and georges bank the fvcom gom system incorporates realistic time dependent surface forcing derived from a high resolution mesoscale meteorological model mm5 and assimilation of observed quantities including sea surface temperature and salinity and temperature fields on the open boundary an evaluation of fvcom gom model skill on the new england shelf is made by comparison of computed fields and data collected during the coastal mixing and optics cmo program august 1996 june 1997 model mean currents for the full cmo period compare well in both magnitude and direction in fall and winter but overpredict the westward flow in spring the direction and ellipticity of the subtidal variability correspond but computed magnitudes are around 20 below observed partially due to underprediction of the variability by mm5 response of subtidal currents to wind forcing shows the model captures the directional dependence as well as seasonal variability of the lag hydrographic results show that fvcom gom resolves the spatial and temporal evolution of the temperature and salinity fields the model computed surface salinity field compares well except in may when there is no indication of the fresh surface layer from the connecticut river discharge noted in the observations analysis of model computed results indicates that the plume was unable to extend to the mooring location due to the presence of a westward mean model computed flow during that time that was stronger than observed overall fvcom gom captures well the dynamics of the mean and subtidal flow on the new england shelf

scattering of coastal trapped waves by irregularities in coastline and topography abstract the scattering of freely propapting coastal trapped waves ctws by large variations in coastline and topography is studied using a numerical model which accomodates arbitrary density stratification bathymetry and coastline particular attention is paid to the role of stratification which in moderate amounts can eliminate backscattered free waves which occur theoretically in a barotropic ocean numerical simulations using widening and narrowing shelf topographies show that the strength of the forward scattering into transmitted ctw modes is proportional to a topographic warp factor which estimates the severity of the topographic irregularities the forward scattering is further amplified by density stratification within the scattering region itself the strengths of the scattered wave induced currents exhibit substantial variation over short spatial scales there is generally a marked intensification of the flow within the scattering region and rapid variations in phase on narrowing shelves