arctic ocean deep water masses in the western iceland sea the icelandic danish contribution to the international greenland sea project was devoted to a study of the distribution and transport of water masses in the western iceland sea each year in september from 1987 to 1991 temperature and salinity were observed on a station net in the area off east greenland from the denmark strait in the south to 72 30 n the data reveal that the deep water column of the western iceland sea is occupied by a number of slightly different water masses which all can be traced back to a formation in the arctic ocean it is especially noticeable that in some years almost undiluted eurasian basin deep water can be observed as far south as the denmark strait

on the stability of ocean overflows author posting cambridge university press 2008 this article is posted here by permission of cambridge university press for personal use not for redistribution the definitive version was published in journal of fluid mechanics 602 2008 241 266 doi 10 1017 s0022112008000827

oceanic propagation of a potential tsunami from the la palma island 1 the likelihood of a large scale tsunami from the la palma island is considered small by most nevertheless the potential catastrophic consequences call for attention here we report on numerical simulations of a tsunami that might result from the extreme case of a flank collapse of the cumbre vieja volcano at the la palma island done by combining a multimaterial model for the wave generation with boussinesq models for the far field propagation our simulations show that the slide speed is close to critical effectively generating an initial wave of several hundred meters height our main focus is the wave propagation which is genuinely dispersive in the far field propagation becomes increasingly complex due to the combined effects of dispersion refraction and interference in the direction of propagation constructive interference of the trailing waves are found to decrease the decay of the maximum amplitude with distance compared to classical asymptotic theory at transatlantic distances thus the commonly used hydrostatic models fail to describe the propagation consequences of the la palma scenario would be largest at the canary islands but our findings also suggests that the whole central atlantic would face grave consequences however the largest surface elevations are smaller than the most pessimistic reports found in literature we also find undular bores towards the shorelines of america

on the transfer of momentum from a granular landslide to a water wave abstract the momentum flux from a landslide at impact in a water body is the driving force behind the generation of landslide tsunamis analysis of this problem is presented and used to derive idealized theoretical relationships for the maximum wave amplitude in the near field zone this is accomplished for momentum transfer using both hydrostatic and hydrodynamic assumptions for rapidly evolving near field waves with a supercritical densimetric froude number the maximum wave amplitude is also constrained according to the fluid continuity equation simplification of the hydrostatic momentum equation is also presented by considering fluid acceleration resulting in an expression that is independent of length and time scales during wave generation the results of the novel momentum based equations are in agreement with laboratory data collected using high speed digital cameras for granular landslides and previously published experimental data used to develop a semi empirical equation furthermore the results provide new insight on the range of applicability of theoretical and semi empirical equations for predicting the maximum near field wave amplitude of landslide generated tsunamis

numerical simulation of waves generated by landslides using a multiple fluid navier stokes model abstract this work reports on the application and experimental validation for idealized geometries of a multiple fluid navier stokes model of waves generated by rigid and deforming slides with the purpose of improving predictive simulations of landslide tsunamis in such simulations the computational domain is divided into water air and slide regions all treated as newtonian fluids for rigid slides a penalty method allows for parts of the fluid domain to behave as a solid with the latter method the coupling between a rigid slide and water is implicitly computed rather than specifying a known slide kinematics two different volume of fluid algorithms are tested for tracking interfaces between actual fluid regions the simulated kinematics of a semi elliptical block moving down a water covered plane slope is first compared to an earlier analytical solution results for the vertical fall of a rectangular block in water are then compared to earlier experimental results finally more realistic simulations of two and three dimensional wedges sliding down an incline are compared to earlier experiments overall in all cases solid block velocities and free surface deformations are accurately reproduced in the model provided that a sufficiently resolved discretization is used the potential of the model is then illustrated on more complex scenarios involving waves caused by multi block or deformable slides

stratigraphic and geochemical evidence for the depositional environment of the early archaean isua supracrustal belt southern west greenland the highly deformed c 3800 ma isua supracrustal belt is a fragment of a more extensive early archaean sedimentary and volcanic succession intruded by and tectonically intercalated with tonalitic and granitic amftsoq gneisses in the period 3800 3600 ma the supracrustal rocks recrystallised under amphibolite facies conditions between 3800 and 3600 ma in the late archaean and locally at c 1800 ma layered sequences of rock of sedimentary and probable volcanic origin form over 50 of the belt bodies of high mg al basic rocks and ultramafic rocks were intruded into the layered sequences prior to isoclinal folding and intrusion of amitsoq gneisses the layered rocks which are 1 km thick are divided into two sequences that are in faulted contact with each other the way up of these sequences has been determined from facing directions of locally preserved graded layering in felsic metasediments at several localities the overall upwards change in sedimentary succession is interpreted as showing change from dominantly basic to dominantly felsic volcanism which provided the major clastic component of the sediments clastic sedimentation took place against a background of chemical sedimentation shown by interlayers of banded iron formation metachert and calc silicate rocks throughout the sequences the felsic rocks locally preserve graded bedding and possible conglomerate structures indicating deposition from turbidite flows and possibly as debris flows nodules in the felsic rocks contain structures interpreted as fiamme there is an irregular enrichment in k2o na2o in many of the felsic rocks at constant sio2 and al2o3 content interpreted as owing to alteration of original andesitic to dacitic volcanic rocks banded iron formations locally contain conglomeratic structures suggesting sedimentary reworking possibly under shallow water conditions lithological and geochemical characters of the clastic components of the supracrustal sequences are consistent with derivation from felsic and basic volcanic rocks and do not require a continental source

numerical analysis of landslide generated impulse waves affected by the reservoir geometry abstract impulse waves generated by landslides are a potential major hazard for the operation of hydropower reservoirs as they pose a serious threat to the dam to residents and to properties along the shoreline a number of experimental studies have been conducted based on generalized models to predict the wave characteristics but using the results from these models to predict landslide generated impulse waves may result in significant errors due to wave reflection caused by changes in the reservoir width to investigate the effects of reservoir geometry on the characteristics of landslide generated waves during propagation 14 numerical experiments were performed using tsunami squares the real sized numerical models were based on statistical data from the yangtze river and a generalized cross section of the gongjiafang landslide located in the three gorges reservoir china two types of generalized reservoir geometries were investigated namely with converging and diverging reservoir widths it is shown that the wave amplitudes decrease with increasing reservoir width while wave heights and troughs have a complicated dependence on changes in reservoir width compared to the amplitudes of the leading waves the wavelengths and start up time of wave amplitudes were more affected in the converging reservoir models by variations in the reservoir width

the production of north atlantic deep water sources rates and pathways updating an earlier account by dickson et al 1990 this paper reviews the initial development phase of north atlantic deep water nadw production from the points where the dense inflows from nordic seas cross the greenland scotland ridge to the point off south greenland where the buildup of new production appears almost complete in particular three long term current meter arrays totaling 91 instruments and set at 160 km intervals south from the denmark strait sill are used to validate earlier short term arrays by others and in combination with these earlier arrays to describe the downstream evolution of mean speed depth and entrainment the variability of the overflow current in space and time and the likely contribution of the other three main constituents of nadw production at densities greater than 27 8 from the points of overflow 5 6 sv the transport within this range increases by entrainment and confluence with other contributory streams to around 13 3 sv at cape farewell while recirculating elements prevent us from determining the net southgoing transport a nadw transport of this order appears consistent with recent estimates of net abyssal flow passing south through the north and south atlantic

a numerical study of the run up generated by three dimensional landslides 1 a large set of numerical experiments are designed to examine the maximum run up generated by three dimensional 3 d submerged and subaerial solid body landslides a depth integrated numerical model is utilized allowing for the efficient simulation of landslides in shallow and intermediate water six dimensionless parameters are introduced the slide thickness the slide wave number a slide shape parameter the horizontal aspect ratio of the slide the specific gravity of the slide mass and the slope of the beach six sets of simulations are first presented wherein one of the six dimensionless parameters are singularly varied this allows for the identification of parameter dependence on maximum run up after combining the dependencies a number of relationships appear most notably a very clear division between the near and far field is observed where here the far field is defined as the region displaced from the projection of the landslide on the nearby beach where edge waves may dominate the wave pattern for submerged slides a nondimensional estimation of the maximum run up just landward of the slide is found as well as the location and magnitude of the secondary run up peak this secondary peak is due to the propagation of edge waves and is in some cases larger than the peak immediately landward of the slide the results presented in this paper may be useful for preliminary hazard assessment where a simple and quick estimation of the maximum run up height and locations are required additionally the formulas developed will be particularly beneficial to those developing 3 d landslide experiments

tsunamis generated by long and thin granular landslides in a large flume in this experimental study granular material is released down slope to investigate landslide generated waves starting with a known volume and initial position of the landslide source detailed data are obtained on the velocity and thickness of the granular flow the shape and location of the submarine landslide deposit the amplitude and shape of the near field wave the far field wave evolution and the wave runup elevation on a smooth impermeable slope the experiments are performed on a 6 7 m long 30 slope on which gravity accelerates the landslides into a 2 1 m wide and 33 0 m long wave flume that terminates with a 27 runup ramp for a fixed landslide volume of 0 34 m3 tests are conducted in a range of still water depths from 0 05 to 0 50 m observations from high speed cameras and measurements from wave probes indicate that the granular landslide moves as a long and thin train of material and that only a portion of the landslide termed the effective mass is engaged in activating the leading wave the wave behavior is highly dependent on the water depth relative to the size of the landslide in deeper water the near field wave behaves as a stable solitary like wave while in shallower water the wave behaves as a breaking dissipative bore overall the physical model observations are in good agreement with the results of existing empirical equations when the effective mass is used to predict the maximum near field wave amplitude the far field amplitude and the runup of tsunamis generated by granular landslides

numerical modeling of tsunami waves generated by the flank collapse of the cumbre vieja volcano la palma canary islands tsunami source and near field effects 1 in this work we study waves generated by the potential collapse of the west flank of the cumbre vieja volcano cvv la palma canary island spain through numerical simulations performed in two stages i the initial slide motion and resulting free surface elevation are first calculated using a 3d navier stokes model ii generated waves are then input into a 2d horizontal boussinesq model to further simulate propagation to the nearby islands unlike in earlier work on cvv besides a similar extreme slide volume scenario of 450 km3 in our simulations i we consider several slide scenarios featuring different volumes i e 20 40 80 km3 which partly result from a geotechnical slope stability analysis ii we use a more accurate bathymetry and iii an incompressible version of a multiple fluid material navier stokes model we find wave trains for each scenario share common features in terms of wave directivity frequency and time evolution but maximum elevations near cvv significantly differ ranging from 600 to 1200 m for increasing slide volume additionally our computations show that significant energy transfer from slide to waves only lasts for a short duration order 200 s which justifies concentrating our best modeling efforts on the early slide motion phase the anticipated consequences of such wave trains on la palma and other canary islands are assessed in detail in the paper

on the hydrography of denmark strait using 111 shipboard hydrographic sections across denmark strait occupied between 1990 and 2012 we characterize the mean conditions at the sill quantify the water mass constituents and describe the dominant features of the denmark strait overflow water dsow the mean vertical sections of temperature salinity and density reveal the presence of circulation components found upstream of the sill in particular the shelfbreak east greenland current egc and the separated egc these correspond to hydrographic fronts consistent with surface intensified southward flow deeper in the water column the isopycnals slope oppositely indicative of bottom intensified flow of dsow an end member analysis indicates that the deepest part of denmark strait is dominated by arctic origin water with only small amounts of atlantic origin water on the western side of the strait the overflow water is a mixture of both constituents with a contribution from polar surface water weakly stratified boluses of dense water are present in 41 of the occupations revealing that this is a common configuration of dsow the bolus water is primarily arctic origin water and constitutes the densest portion of the overflow the boluses have become warmer and saltier over the 22 year record which can be explained by changes in end member properties and their relative contributions to bolus composition

is the faroe bank channel overflow hydraulically controlled abstract the overflow of dense water from the nordic seas through the faroe bank channel fbc has attributes suggesting hydraulic control primarily an asymmetry across the sill reminiscent of flow over a dam however this aspect has never been confirmed by any quantitative measure nor is the position of the control section known this paper presents a comparison of several different techniques for assessing the hydraulic criticality of oceanic overflows applied to data from a set of velocity and hydrographic sections across the fbc these include 1 the cross stream variation in the local froude number including a modified form that accounts for stratification and vertical shear 2 rotating hydraulic solutions using a constant potential vorticity layer in a channel of parabolic cross section and 3 direct computation of shallow water wave speeds from the observed overflow structure though differences exist the three methods give similar answers suggesting that the fbc is indeed controlled with a

on the effect of the water body geometry on landslide tsunamis physical insight from laboratory tests and 2d to 3d wave parameter transformation preliminary landslide tsunami hazard assessment is commonly based on empirical equations derived from wave channel 2d or wave basin 3d experiments the far field wave in 2d can easily be an order of magnitude larger than in 3d the present study systematically investigates the effect of the water body geometry on the wave characteristics in the near and far field subaerial landslide tsunami tests were conducted relying upon both a 2d and a 3d physical model undertaken with identical boundary conditions the test parameters included two water depths three rigid slides as well as various slide release positions empirical equations for 3d offshore and laterally onshore wave properties are presented and compared with previous work a direct comparison of the wave features reveals that the waves decay in 2d 3d onshore and 3d offshore with x 0 30 r 0 67 and r 1 0 where x 2d and r 3d describe the distance from the impact zone in 2d four wave types are observed whereas only the two least non linear types were observed in 3d this finding is further analysed with wavelet spectra for a large slide froude number f relative slide thickness s and relative slide mass m the 3d wave heights in the slide impact zone can be as large as in 2d however for small f s and m the 3d waves are considerably smaller both in the near and far field a novel method is presented and validated to transform data from 2d studies to 3d this method may have favourable implications on preliminary landslide tsunami hazard assessment

variability of the denmark strait overflow a numerical study mesoscale variability in the denmark strait overflow is investigated using a version of the miami isopycnic coordinate ocean model that includes a recently developed intermittent and vigorous turbulent and diffusive diapycnal mixing scheme earlier idealized modeling work on the subject is further extended in that a realistic replica of the shelf slope topography and irregular coastline geometry of the denmark strait area is also employed compared with earlier studies our experiments reveal that 1 the introduction of the new diapycnal scheme and the true shelf slope topography do not affect the formation of the intense cyclonic eddies south of the sill and along the continental slope and 2 the new diapycnal scheme has a significant effect on the bottom plume in that the distribution volume transport and properties of the bottom plume appear to be more realistic and more in line with what is observed the first conclusion adds support to the vortex stretching mechanism suggested in earlier studies as the cause for the formation of the cyclonic eddies this mechanism is therefore a robust feature and provides an explanation for the observed variability in the denmark strait overflow the second conclusion underscores the importance of including realistic parameterizations of diapycnal mixing in isopycnal coordinate ocean models specifically the results show that the water that descends along the bottom south of the sill becomes lighter and is more voluminous compared to experiments without the new mixing scheme even when including the mixing scheme the bottom plume separates into distinct boluses of enhanced thickness moreover these boluses are also associated with water of anomalously high density as well as with the cyclonic eddies in the upper water column

extinction of the northern oceanic deep convection in an ensemble of climate model simulations of the 20th and 21st centuries we study the variability and the evolution of oceanic deep convection in the northern north atlantic and the nordic seas from 1850 to 2100 using an ensemble of 12 climate model simulations with ec earth during the historical period the model shows a realistic localization of the main sites of deep convection with the labrador sea accounting for most of the deep convective mixing in the northern hemisphere labrador convection is partly driven by the nao correlation of 0 6 and controls part of the variability of the amoc at the decadal time scale correlation of 0 6 when convection leads by 3 4 years deep convective activity in the labrador sea starts to decline and to become shallower in the beginning of the twentieth century the decline is primarily caused by a decrease of the sensible heat loss to the atmosphere in winter resulting from increasingly warm atmospheric conditions it occurs stepwise and is mainly the consequence of two severe drops in deep convective activity during the 1920s and the 1990s these two events can both be linked to the low frequency variability of the nao a warming of the sub surface resulting from reduced convective mixing combines with an increasing influx of freshwater from the nordic seas to rapidly strengthen the surface stratification and prevent any possible resurgence of deep convection in the labrador sea after the 2020s deep convection in the greenland sea starts to decline in the 2020s until complete extinction in 2100 as a response to the extinction of deep convection in the labrador and greenland seas the amoc undergoes a linear decline at a rate of about 0 3 sv per decade during the twenty first century

ritter island volcano lateral collapse and the tsunami of 1888 summary in the early morning of 1888 march 13 roughly 5 km 3 of ritter island volcano fell violently into the sea northeast of new guinea this event the largest lateral collapse of an island volcano to be recorded in historical time flung devastating tsunami tens of metres high on to adjacent shores several hundred kilometres away observers on new guinea chronicled 3 min period waves up to 8 m high that lasted for as long as 3 h these accounts represent the best available first hand information on tsunami generated by a major volcano lateral collapse in this article we simulate the ritter island landslide as constrained by a 1985 sonar survey of its debris field and compare predicted tsunami with historical observations the best agreement occurs for landslides travelling at 40 m s 1 but velocities up to 80 m s 1 cannot be excluded the ritter island debris dropped little more than 800 m vertically and moved slowly compared with landslides that descend into deeper water basal friction block models predict that slides with shorter falls should attain lower peak velocities and that 40 ms 1 is perfectly compatible with the geometry and runout extent of the ritter island landslide the consensus between theory and observation for the ritter island waves increases our confidence in the existence of mega tsunami produced by oceanic volcano collapses two to three orders of magnitude larger in scale

the tsunami phenomenon abstract with human activity increasingly concentrating on coasts tsunamis from japanese tsu harbour nami wave are a major natural hazard to today s society stimulated by disastrous tsunami impacts in recent years for instance in south east asia 2004 or in japan 2011 tsunami science has significantly flourished which has brought great advances in hazard assessment and mitigation plans based on tsunami research of the last decades this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view starting with the wave features tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy loss at the coast tsunamis typically show wave shoaling funnelling and resonance effects as well as a significant run up and backflow tsunami waves are caused by a sudden displacement of the water column due to a number of various trigger mechanisms such are earthquakes as the main trigger submarine and subaerial mass wastings volcanic activity atmospheric disturbances meteotsunamis and cosmic impacts as is demonstrated by giving corresponding examples from the past tsunamis are known to have a significant sedimentary and geomorphological off and onshore response so called tsunamites form allochthonous high energy deposits that are left at the coast during tsunami landfall tsunami deposits show typical sedimentary features as basal erosional unconformities fining upward and landward a high content of marine fossils rip up clasts from underlying units and mud caps all reflecting the hydrodynamic processes during inundation the on and offshore behaviour of tsunamis and related sedimentary processes can be simulated using hydro and morphodynamic numerical models the paper provides an overview of the basic tsunami modelling techniques including discretisation guidelines for appropriate temporal and spatial resolution as well as the nesting method furthermore the boussinesq approximation a simplification of the three dimensional navier stokes equations is presented as a basic theory behind numerical tsunami models which adequately reflects the non linear dispersive wave behaviour of tsunamis the fully non linear boussinesq equations allow the simulation of tsunamis e g in the form of n waves based on the various subtopics presented recommendations for future multidisciplinary tsunami research are made it is especially discussed how the combination of sedimentary and geomorphological tsunami field traces and numerical modelling techniques can contribute to derive locally relevant tsunami sources and to improve the assessment of tsunami hazards considering the individual pre history and physiogeographical setting of a specific region

interannual changes in the overflow from the nordic seas into the atlantic ocean through denmark strait the global thermohaline circulation is an important part of earth s climate system cold dense water formed in the nordic seas enters the atlantic ocean as overflows across the sills of the greenland scotland ridge the denmark strait overflow dso is one of the main sources of north atlantic deep water until now the dso has been believed to be stable on interannual timescales here for the first time evidence is presented from a 4 year program of observations showing that overflow transports in 1999 2000 were approximately 30 higher than previous estimates later transports decreased remarkably during the observation period coincident with a temporary temperature increase of about 0 5 c

debris flow generated tsunamis and their dependence on debris flow dynamics abstract debris flow generated tsunamis can be extremely dangerous for lakeside settlements and infrastructure debris flow composition strongly affects debris flow thickness and velocity and therefore also the generated tsunami this interaction is however poorly understood we investigate the effects of debris flow volume composition gravel sand clay water and subaerial outflow slope on wave celerity and amplitude in a small scale physical model consisting of an inclined outflow channel which transits into a three dimensional water reservoir we find that upon debouching a debris flow pushes the water forward until wave celerity exceeds subaqueous debris flow velocity i e froude number wave celerity has the strongest relation with debris flow velocity debris flow velocity increases with increasing water and clay content up to 22 which both lubricate the flow far field leading wave amplitude has the strongest relation with debris flow momentum velocity times effective mass which is mostly a function of debris flow thickness water and clay content we test the applicability of published semi empirical equations for predicting tsunami amplitude generated by dry landslides and show that they are to some extent also applicable to debris flow potential scale effects especially considering the smallest waves and water depths could influence the applicability of these predictors and translation of the results to the field scale our results demonstrate the importance of debris flow composition on tsunami generation and evolution and thus the necessity of including flow composition in predictive simulation models

three dimensional modeling of tsunami generation due to a submarine mudslide abstract submarine landslides are a common cause of tsunamis in coastal and estuarine areas to study this phenomenon a numerical model is developed to simulate tsunami generation due to a viscous mudslide on a gentle uniform slope a formulation of the dynamics of the problem is presented where the mudslide is treated as an incompressible three dimensional viscous flow seawater is treated as an inviscid fluid and the water motion is assumed irrotational the long wave approximation is adopted for both water waves and the mudslide the resulting differential equations are solved by a finite difference method the focus of this paper is to examine the effects of the longitudinal spreading as well as the transversal spreading of the slide upon surface wave generation and the spreading of water waves sideways three dimensional pictures are presented for successive profiles of the mud surface the horizontal velocities of the mudslide the evolution of the surface elevations and the velocities of the w

earliest part of earth s stratigraphic record a reappraisal of the 3 7 ga isua greenland supracrustal sequence investigations of the isua supracrustal rocks in west greenland allow us to identify the protoliths and alteration history for most isua rocks the protoliths consisted of alternating basalt and banded iron formation this sequence was invaded by dunitic sills metamorphosed and later intruded by felsic gneisses pervasive carbonation and k metasomatism produced a sequence of lithologies mimicking those found in modern platform deposits however the protoliths could have originated in a purely oceanic environment with no sialic detrital components the isua sequence probably consists of several tectonic panels some of which are cut by 3810 ma felsic intrusive rocks

hydraulic estimates of denmark strait overflow 1 upper bounds of the denmark strait deep water overflow from the nordic seas into the north atlantic are estimated using rotating hydraulic theory the calculations are made for the real bottom topography of the strait and are based on hydrographic sections surveyed during a dedicated field experiment in the area results are presented for zero as well as finite but constant potential vorticity and it is shown that the differences in outcome between these two approaches are only minor the calculated interface configurations are found to be in good agreement with those observed and the theoretically obtained transports conform with earlier estimates

hydraulic control of sill flow with bottom friction abstract the hydraulics of strait and sill flow with friction is examined using a reduced gravity model it is shown that friction moves the critical or control point from the sill to a location downstream if the strait has constant width the control point lies where the bottom slope is the negative of the drag coefficient cd if cd exceeds the bottom slope everywhere the flow cannot be controlled in the classical sense that energy and flow force are minimized friction also decreases the minimum obstacle height required to establish hydraulically controlled flow in the classical laboratory towing experiment also friction greatly encourages the establishment of stationary hydraulic jumps in the lee of the sill and under certain conditions gives rise to stationary jumps on the upstream face of the obstacle some consequences of these results for deep ocean overflows are given using the iceland faroe overflow as an example

on the effective capacity of the dense water reservoir for the nordic seas overflow some effects of topography and wind stress abstractthe overflow of the dense water mass across the greenland scotland ridge gsr from the nordic seas drives the atlantic meridional overturning circulation amoc the nordic seas is a large basin with an enormous reservoir capacity the volume of the dense water above the gsr sill depth in the nordic seas according to previous estimates is sufficient to supply decades of overflow transport this large capacity buffers overflow s responses to atmospheric variations and prevents an abrupt shutdown of the amoc in this study the authors use a numerical and an analytical model to show that the effective reservoir capacity of the nordic seas is actually much smaller than what was estimated previously basin scale oceanic circulation is nearly geostrophic and its streamlines are basically the same as the isobaths the vast majority of the dense water is stored inside closed geostrophic contours in the deep basin and thus is not freely available to the overflow the positive wind stress curl in the no

cyclogenesis in the denmark strait overflow plume a densely spaced hydrographic survey of the northern irminger basin together with satellite tracked near surface drifters confirm the intense mesoscale variability within and above the denmark strait overflow in particular the drifters show distinct cyclonic vortices over the downslope edge of the outflow plume growing perturbations such as these can be attributed to the baroclinic instability of a density current a primitive equation model with periodic boundaries is used to simulate the destabilization of an idealized dense filament on a continental slope that resembles the northeastern irminger basin unstable waves evolve rapidly if the initial temperature profile is perturbed with a sinusoidal anomaly that exceeds a certain cutoff wavelength as the waves grow to large amplitudes isolated eddies of both signs develop anticyclones form initially within the dense filament and are rich in overflow water in contrast cyclones form initially with their center in the ambient water but wrap outflow water around their center thus containing a mixture of both water types the nonlinear advection of waters that were originally located within the front between both water masses contributes most significantly to the stronger intensification of the cyclones in comparison with anticyclones the frontal waters carry positive relative vorticity into the center of the cyclone the process bears therefore some resemblance to atmospheric frontal cyclogenesis after saturation there is a bottom jet of overflow water that is confined by counterrotating eddies anticyclones upslope and cyclones downslope of the overflow core the parameter dependence of the maximum growth rate is studied and the implications of eddy induced mixing for the water mass modification is discussed

topographic control of oceanic flows in deep passages and straits saddle points between neighboring deep ocean basins are the sites of unidirectional flow from one basin to the next depending on the source of bottom water flow in these sites appears to be topographically controlled so the interface between the bottom water and the water above adjusts itself to permit bottom water flow from the basin that contains a source of bottom water into the next examples in the atlantic include flow in the romanche fracture zone the vema channel the ceara abyssal plain the anegada jungfern passage and the discovery gap but there are many more theoretical predictions of volume flux using a method that requires only conductivity temperature depth data archives and detailed knowledge of bathymetry near the saddle point are compared with volume flux estimates using current meters and or geostrophic estimates for seven cases the ratio of prediction to volume flux estimate ranges from 1 0 to 2 7 some ocean straits that separate adjacent seas are also found to critically control bidirectional flows between basins theory of the influence of rotation on such critical flows is reviewed predictions of volume flux in eight cases are compared with ocean estimates of volume flux from traditional methods

high frequency variability in the circulation and hydrography of the denmark strait overflow from a high resolution numerical model abstractinitial results are presented from a yearlong high resolution 2 km numerical simulation covering the east greenland shelf and the iceland and irminger seas the model hydrography and circulation in the vicinity of denmark strait show good agreement with available observational datasets this study focuses on the variability of the denmark strait overflow dso by detecting and characterizing boluses and pulses which are the two dominant mesoscale features in the strait the authors estimate that the yearly mean southward volume flux of the dso is about 30 greater in the presence of boluses and pulses on average boluses pulses are 57 1 27 5 h long occur every 3 2 5 5 days and are more frequent during the summer winter boluses pulses increase decrease the overflow cross sectional area and temperatures around the overflow interface are colder warmer by about 2 6 c 1 8 c the lateral extent of the boluses is much greater than that of the pulses in both cases the along stra

experimental analysis of tsunamis generated by the impact of landslides with high mobility abstract landslides into water can generate massive tsunamis which are major natural hazards in coastal regions in this study waves were generated in a series of 41 laboratory experiments by releasing 4 different slide volumes ranging from 0 1 0 4 m3 of highly mobile material down a 6 73 m long slope into a reservoir of depth varying from 0 15 0 65 m to achieve a wide range of dimensionless landslide parameter values water is used as the sliding material and with zero internal shear strength it is representative of the upper limit of high landslide mobility the slide characteristics of thickness and velocity were measured at impact using high speed cameras and the time series of the resulting changes in water surface elevation were measured using nine wave probes along the 33 8 m long flume the experimental results indicate that in the near field the maximum wave amplitude is dependent on the landslide thickness and velocity and is relatively independent of the reservoir water depth as waves propagate to the far field the depth limited breaking reduces the wave amplitude such that the maximum wave amplitude is highly dependent on the reservoir depth the wave breaking limit which differentiates the breaking from the non breaking waves is defined by the relationship am h 0 6 that is very closely adhered to for all source volumes and reservoir depths the time and length over which the waves are generated are determined from the digital imagery and are used to describe the scales of the momentum transfer these observations are compared with previously published empirical and theoretical equations for granular landslides and positively buoyant avalanches indicating that water is a useful source material for simulating highly mobile landslides since these parameters are difficult to obtain in field cases a simplification of the theoretical equation is presented and this yields reasonable results for the maximum wave amplitude generated by slides with high mobility

probabilistic hazard analysis of impulse waves generated by multiple subaerial landslides and its application to wu gorge in three gorges reservoir china abstract subaerial landslides can generate impulse waves in reservoirs fjords and other water bodies and cause severe damage to the shipping industry infrastructure and human communities along the shorelines compared with deterministic hazard models probabilistic hazard analysis is an important tool for assessing the intensity and exceedance probability of impulse waves generated by multiple landslide sources which are essential for evidence based risk mitigation and contingency planning this paper proposes a methodological procedure for systematic probabilistic hazard analysis of impulse waves generated by subaerial landslides considering all relevant landslide sources and multiple uncertainties i e landslide mechanisms triggering scenarios and material parameters the main steps include 1 definition of the source parameters by parameterizing the epistemic and aleatory uncertainties in this respect the logic tree event tree and monte carlo models were used to organize the uncertainties of landslide mechanism models parametric scenarios and material parameters respectively 2 estimation of generated waves based on a landslide dynamic analytical model and previously validated empirical wave models derived from prototype scaled experiments and 3 aggregation of the hazard analysis results in the form of hazard maps and probability maps under parametric scenarios and a specific scenario considering the wu gorge in the three gorges reservoir as a case study soil slides and unstable rock slopes were analyzed to quantify the wave hazard along the reservoir under parametric and specific scenarios while considering rainfall and water level fluctuations the results show considerable wave hazard in the wu gorge for a 20 year return period the maximum expected height of propagation waves is 14 41 m the probability of experiencing propagation waves higher than 2 m in 20 years is over 50 in the river segment with high landslide density the results of the probabilistic wave hazard analysis could be aggregated and disaggregated to accommodate specific requirements of wave risk management

synoptic sections of the denmark strait overflow we report on a rapid high resolution survey of the denmark strait overflow dso as it crosses the sill the first such program to incorporate full water column velocity profiles in addition to conventional hydrographic measurements seven transects with expendable profilers over the course of one week are used to estimate volume transport as a function of density our observations reveal the presence of a strongly barotropic flow associated with the nearly vertical front dividing the arctic and atlantic waters the seven section mean transport of water denser than 27 8 is 2 7 0 6sv while the mean transport of water colder than 2 0 c is 3 8 0 8 sv although this is larger than the 2 9 sv of 2 c water measured by a 1973 current meter array we find that a sampling of our sections equivalent to the extent of that array also measures 2 9sv of cold water both the structure and magnitude of the measured flow are reproduced well by a high resolution numerical model of buoyancy driven exchange with realistic topography

denmark strait overflow for last glacial maximum to holocene conditions 1 the denmark strait plays an important role as a dense water gateway between the arctic and the subpolar north atlantic previous studies have shown that the volume transport over the sill is limited by hydraulic constraints a regional ocean circulation model roms with a horizontal resolution of 1 20 degree and 30 sigma layers in the vertical is applied to study the through flow characteristics for last glacial maximum to holocene conditions the bathymetry of the gateway region is obtained from a geodynamic model that takes into account the differential ice loading of the adjacent continents first the upstream reservoir conditions are systematically changed to test hydraulic limitations for altered bathymetry generally the through flow is less than the predicted maximal value from hydraulic theory by almost 50 the results indicate that the reduction in gateway depth and aperture owing to glacial isostatic processes alone lead to a considerable further reduction of the overflow by approximately 33 compared to the present day second the through flow is modeled using average density profiles and wind stress from global model data the reduction in the density driven part of the overflow is partly compensated by an enhanced wind stress but is still reduced by a factor of 5 owing to the narrowing of the strait during the glacial and the increased northerly wind the north icelandic irminger current was strongly reduced but still existent

physical modeling of tsunamis generated by three dimensional deformable granular landslides 1 tsunamis generated by deformable granular landslides are physically modeled in a three dimensional tsunami wave basin based on the generalized froude similarity the dynamic landslide impact characteristics were controlled by means of a novel pneumatic landslide generator the wave amplitudes periods and wavelengths are related to the landslide parameters at impact with the landslide froude number being a dominant parameter between 1 and 15 of the landslide kinetic energy at impact is converted into the wave train energy the wave amplitudes decay in radial and angular directions from the landslide axis the first wave crest mostly travels with speeds close to the theoretical approximation of the solitary wave speed the measured tsunami wave profiles were either of the nonlinear oscillatory or nonlinear transition type depending primarily on the landslide froude number and relative slide thickness at impact the generated waves range from shallow to deep water depth regimes with the majority being in the intermediate water depth regime wave characteristics are compared with other two and three dimensional landslide tsunami studies and the results are discussed

sources to the east greenland current and its contribution to the denmark strait overflow data from the east greenland current in 2002 are evaluated using optimum multiparameter analysis the current is followed from north of fram strait to the denmark strait sill and the contributions of different source waters in mass fractions are deduced from the results it can be concluded that at least in spring 2002 the east greenland current was the main source for the waters found at the denmark strait sill contributing to the overflow into the north atlantic the east greenland current carried water masses from different source regions in the arctic ocean the west spitsbergen current and the greenland sea the results agree well with the known circulation of the western nordic seas but also add knowledge both to the quantification and to the mixing processes showing the importance of the locally formed greenland sea arctic intermediate water for the east greenland current and the denmark strait

evolution and dynamics of the flow through herald canyon in the western chukchi sea abstract the flow of summer and winter pacific water masses through herald canyon is investigated using data from a high resolution hydrographic velocity survey conducted in summer 2004 the survey was part of the russian american long term census of the arctic rusalca program and consisted of four cross canyon transects occupied over a 2 day period at the time of the survey dense winter water was entering the western side of the canyon from the chukchi sea flowing alongside a poleward jet of summer water on the canyon s eastern flank as the dense water progressed northward it switched sides of the canyon and underwent a sudden increase in layer thickness this coincided with vertical mixing near the interface of the winter and summer water producing a new water mass mode exiting the canyon all of these features are consistent with the notion of hydraulic activity occurring in the canyon a three layer hydraulic theory is applied to the flow which suggests that it is supercritical and that hydraulic control is likely a lock exchange formulation accurately predicts the northward transport of the winter water the origin of the winter water and the manner in which it drains into the canyon is investigated using satellite ice concentration data atmospheric re analysis fields historical in situ data and a simple circulation model finally the fate of the pacific water exiting the canyon and its connection to the chukchi shelfbreak current is discussed

improved landslide tsunami prediction effects of block model parameters and slide model 1 subaerial landslide tsunamis and impulse waves are caused by mass movements impacting into a water body and the hazards they pose have to be reliably assessed empirical equations developed with physical froude model studies can be an efficient method for such predictions the present study improves this methodology and addresses two significant shortcomings in detail for the first time these are the effect of three commonly ignored block model parameters and whether the slide is represented by a rigid block or a deformable granular material a total of 144 block slide tests were conducted in a wave flume under systematic variation of three important block model parameters the slide froude number the relative slide thickness and the relative slide mass empirical equations for the maximum wave amplitude height and period as well as their evolution with propagation distance are derived for most wave parameters remarkably small data scatter is achieved the combined influence of the three block model parameters affects the wave amplitude and wave height by up to a factor of two the newly derived equations for block slides are then related to published equations for granular slides this comparison reveals that block slides do not necessarily generate larger waves than granular slides as often argued in the technical literature in fact it is shown that they may also generate significant smaller waves the new findings can readily be integrated in existing hazard assessment methodologies and they explain a large part of the discrepancy between previously published data

denmark strait overflow comparing model results and hydraulic transport estimates 1 the transport of dense water through denmark strait is investigated with a high resolution numerical model the results are compared with different transport estimates from rotating hydraulic theory in order to evaluate such theories with respect to the interpretation of hydrographic data generally estimates far upstream result in upper transport limitations that can be appropriately scaled to give time mean transport estimates whereas estimates from the sill entrance region can provide a good approximation of the variable transport

sph numerical simulation of tsunami wave forces impinged on bridge superstructures abstract this paper addresses numerically derived tsunami wave loads on bridge superstructures using smoothed particle hydrodynamics sph which is a type of mesh free methods although there exist some relationships for the case of impinged loads on bridges exerted by regular sinusoidal waves for the case of solitary waves such as tsunamis no relation has yet been proposed in the literature this shortcoming is partly due to the lack of understanding the mechanism of wave action on the bridge superstructures in this study three water depths three wave amplitudes and four submergence depths of the deck are considered for the process of numerical investigation of tsunami induced loads on bridge superstructures the bridge elevation is chosen such that its deck may become either completely emerged partially submerged or completely submerged upon occurrence of the tsunami event comparison of the numerical results with the experiment recordings approves high level of accuracy of the sph scheme based on the obtained results from the numerical modeling the maximum applied horizontal and vertical forces to the bridge superstructure are presented for each configuration of water depths wave amplitudes and deck elevations in this way the maximum clockwise counterclockwise moments induced at the center of the structure are also determined simple non dimensional equations are proposed for computing the tsunami induced forces and moments to the bridge superstructures which can be used for designing the bridge superstructures at the coastal areas

frontogenesis and variability in denmark strait and its influence on overflow water abstracta high resolution numerical model together with in situ and satellite observations is used to explore the nature and dynamics of the dominant high frequency from one day to one week var

recognizable primary volcanic and sedimentary features in a low strain domain of the highly deformed oldest known 3 7 3 8 gyr greenstone belt isua west greenland a low strain domain has been identified in the metamorphosed mostly highly deformed volcanic and sedimentary rocks of the early archaean isua supracrustal belt this domain contains well preserved volcanic and sedimentary features including basaltic pillow lavas pillow breccia heterogeneous volcanic breccia amygdules in metabasalt and polymict conglomerate dominated by recrystallized chert and volcanic clasts the low strain domain is bounded by highly deformed rocks mostly derived from basalt chert and banded iron formation these discoveries demonstrate that some primary features have escaped the pervasive metasomatism dominant in other parts of the belt and furthermore strengthen the characterization of the isua supracrustals as a typical greenstone belt

upstream separation in a rotating channel flow the question of upstream separation of a current of dense rotating fluid below a stagnant layer of lower density that is critically controlled by a weir is addressed in laboratory experiments that follow from theoretical calculations for a constant potential vorticity flow in a gradually varying channel it is shown that a range of parameters lead to upstream separation in all cases the flow reattaches before reaching the sill crest so that a closed gyre is produced in laboratory experiments separation and reattachment was observed in numerous cases where the theory predicts closed gyres although the shape and size of the gyre are in accordance with theory the circulation within the gyre differs markedly from theoretical predictions the mechanism that feeds energy into the gyre appears to be an important unsolved problem the results indicate that upstream separation is a fact and that the dynamics of the gyre is significant so the gyre dynamics may modify the volume flux of fluid over the weir

on the nature of the mesoscale variability in denmark strait abstracttime series data from a mooring in the center of denmark strait and a collection of shipboard hydrographic sections occupied across the sill are used to elucidate the mesoscale variability of the dense overflow water in the strait two dominant reoccurring features are identified that are referred to as a bolus and a pulse a bolus is a large weakly stratified lens of overflow water associated with cyclonic rotation and a modest increase in along stream speed of 0 1 m s 1 when a bolus passes through the strait the interface height of the overflow layer increases by 60 m and the bottom temperature decreases by 0 4 c by contrast a pulse is characterized by anticyclonic rotation a strong increase in along stream speed of 0 25 m s 1 a decrease in interface height of 90 m and no significant bottom temperature signal it is estimated that on average boluses pulses pass through the strait every 3 4 5 4 days with no seasonal signal to their frequency both features have the strongest along

composite modelling of subaerial landslide tsunamis in different water body geometries and novel insight into slide and wave kinematics this article addresses subaerial landslide tsunamis with a composite experimental numerical modelling approach a shortcoming of generic empirical equations used for hazard assessment is that they are commonly based on the two idealised water body geometries of a wave channel 2d or a wave basin 3d a recent systematic comparison of 2d and 3d physical block model tests revealed wave amplitude differences of up to a factor of 17 the present article investigates two of these recently presented 2d 3d test pairs in detail involving a solitary like wave scenario 1 and stokes like waves scenario 2 results discussed include slide and water particle kinematics and novel pressure measurements on the slide front instantaneous slide water interaction power graphs are derived and potential and kinetic wave energies are analysed solitary wave theory is found most appropriate to describe the wave kinematics associated with scenario 1 whereas stokes theory accurately describes the tsunami in scenario 2 the data of both scenarios are further used to calibrate the smoothed particle hydrodynamics sph code dualsphysics v3 1 which includes a discrete element method dem based model to simulate the slide ramp interaction five intermediate geometries lying between the ideal 2d and 3d cases are then investigated purely numerically for a channel geometry with a diverging side wall angle of 7 5 the wave amplitudes along the slide axes were found to lie approximately halfway between the values observed in 2d and 3d at 45 the amplitudes are practically identical to those in 3d the study finally discusses the implications of the findings for engineering applications and illustrates the potential and current limitations of dualsphysics for landslide tsunami hazard assessment

impulse waves in reservoirs generated by landslides into shallow water abstract landslides sliding into shallow water often block watercourses and in addition landslide induced impulse waves may result in risks to the safety of the reservoir or waterways over a wide area such impulse waves differ from those from landslides into deep water which slide underwater completely this study conducted twenty five groups of orthogonal experiments of landslide induced impulse waves in shallow water where the froude numbers ranged between 0 6 and 2 0 based on the experimental results dimensionless functions of the parameters such as amplitude wavelength and jet flow height of the initial landslide induced waves in shallow water were derived the predictions from these formulae are very close to those obtained from the experiments further a source model of landslide induced waves in shallow water was built based on formulae derived from the experiments and wave propagation and run up were calculated with the boussinesq type equations model the newly built model of landslide induced waves in shallow water was used to calculate and analyze two representative examples from landslides in the three gorges in china namely the qianjiangping landslide induced impulse wave event and the xintan landslide induced impulse wave event comparison of the calculations with data from multiple sources indicated that our model for landslide induced waves in shallow water had high accuracy our model for landslide induced waves in shallow water may help in the predictive analysis of impulse waves and mitigation works for this type of event in reservoirs worldwide

initial pb of the amitsoq gneiss revisited implications for the timing of early archaean crustal evolution in west greenland reply abstract the rapid change in 207 pb 206 pb ratio during early earth history provides a powerful constraint for temporal resolution of archaean crustal evolution new and published data for amitsoq gneiss feldspars and whole rocks define the earth s least radiogenic silicate pb known until now the most important feature of the data is that independent of the exact slope of the regression in a common pb diagram a very well defined intercept with plausible terrestrial pb evolution lines is obtained between 3 63 and 3 66 ga identical to a combined pb pb regression age of 3654 73 ma mswd 17 6 we conclude that the magmatic precursors of the amitsoq orthogneisses separated from a depleted mantle like source at ca 3 65 ga this contrasts sharply with claims based on ion probe u pb zircon dating that the amitsoq gneisses had a prolonged episodic magmatic evolution extending from ca 3 87 to 3 60 ga pb isotopes offer no evidence that any amitsoq gneiss analysed until now began its evolution in the crust as long ago as 3 85 ga we propose that zircons significantly older than 3 65 ga were inherited from chemically evolved rocks as old as ca 3 85 ga geochemical arguments are presented to support this proposal new feldspar and whole rock pb isotope data are also reported for sheets of quartz dioritic gneiss on akilia island that yield the oldest zircon u pb age clusters in the range 3 84 3 87 ga these sheets are discordant to a metasedimentary enclave containing accessory apatite with graphite inclusions whose c isotope ratios are regarded as biogenic in origin as above pb isotopes in the sheets are consistent with a magmatic age of 3 65 ga which we regard as the true minimum age for these waterlain sediments and their possibly biogenic markers additional pb isotope data as well as limited published sm nd and u pb zircon data on the akilia enclaves themselves suggest an age between ca 3 65 and 3 70 ga for their original deposition some 150 200 ma younger than proposed previously thus the question of overlap of earliest life with a bolide impact scenario terminating 3 80 ga as on the moon becomes irrelevant

protoliths of the 3 8 3 7 ga isua greenstone belt west greenland abstract the isua greenstone belt fig 1 contains the oldest known relatively well preserved metavolcanic and metasedimentary rocks on earth the rocks are all deformed and many were substantially altered by metasomatism but both the deformation and metasomatism were heterogeneous transitional stages can be seen from relatively well preserved primary volcanic and sedimentary structures to schists in which all primary features have been obliterated likewise different kinds and different episodes of metasomatic alteration can be seen that produced a diversity of different compositions and metamorphic mineral assemblages from similar protoliths new geological mapping has traced out gradations between the best preserved protoliths and their diverse deformed and metasomatised equivalents by this means the primary nature of the schists that make up most of the isua greenstone belt was reinterpreted and a new map that better portrays the primary nature of the rocks has been produced the previously mapped stratigraphy was found to be of little value in understanding the geology stratigraphic units were defined by different and diverse criteria such as current composition structure metamorphic texture and inferred protoliths much of this stratigraphy represents a misinterpretation of the primary nature of the rocks the new work indicates that most of the isua greenstone belt consists of fault bounded rock packages mainly derived from basaltic and high mg basaltic pillow lava and pillow lava breccia chert bif and a minor component of clastic sedimentary rocks derived from chert and basaltic volcanic rocks a previously mapped extensive unit of felsic volcanic rocks was found to be derived from metasomatised basaltic pillow lava and pillow breccia intruded by numerous sheets of tonalite

mesoscale variability in denmark strait the pv outflow hypothesis abstract the outflow through denmark strait shows remarkable mesoscale variability characterized by the continuous formation of intense mesoscale cyclones just south of the sill these cyclones have a diameter of about 30 km and clear signatures at the sea surface and in currents measured near the bottom they have a remnant of arctic intermediate water aiw in their core the authors hypothesis is that these cyclones are formed by stretching of the high potential vorticity pv water column that outflows through denmark strait the light upper layer of the outflow the east greenland current remains on the surface in the irminger sea while the dense overflow water descends the east greenland continental slope the midlevel waters mostly aiw could thus be stretched by more than 100 which would induce very strong cyclonic relative vorticity the main test of this new hypothesis is by way of numerical experiments carried out with an isopycnal coordinate ocean model configured to have a marginal sea

forecasting impulse waves generated by subaerial landslides 1 subaerial landslides falling into reservoirs or open seas generate impulsive water waves that are usually referred to as a class of tsunami waves it is important to study landslide generated waves occurring both in closed water basins where the waves interact with the shorelines and eventually the dam and in open seas where the generated waves can travel and deliver devastating damages hundreds of kilometers away in order to gain insight on subaerial landslide generated waves the italian national dam office recently funded an experimental and numerical research program geared to better understand and forecast tsunamis waves this paper introduces the experimental work which has been carried out in order to define empirical formulations able to forecast the principal features of the generated waves in a three dimensional water body as a function of the landslide movement wave types observed during the experiments are here characterized using a wavelet analysis approach new forecasting formulations named rid formulas are defined on the basis of the experimental study and tested using an artificial neural network model results are finally compared to those presented in past experimental studies

the faroe bank channel deep water overflow in the late 1950s it was recognised that a considerable transport of water from the deeper reaches of the norwegian sea into the atlantic takes place through the faroe bank channel which thereby serves as an important source for the renewal of the north atlantic deep water consequently substantial efforts have over the past decades been dedicated towards quantifying the overflow as well as clarifying the underlying dynamics in the present review an attempt is made to summarise the main body of the observational results as well as some theoretical considerations regarding the dynamical mechanisms the most prominent characteristic of the faroe bank channel overflow is that it is a persistent phenomenon with a yearly average deep water viz t 5degreesc transport of around 2 sv using inviscid rotating hydraulics the flow through the controlling section at the sill furthermore can be reasonably well predicted on the basis of upstream conditions in the norwegian sea after passing the threshold the descending overflow plume is subject to intense mixing a process very much in the focus of ongoing research c 2004 elsevier ltd all rights reserved

numerical modelling of landslide tsunami propagation in a wide range of idealised water body geometries abstract large landslide tsunamis are caused by mass movements such as landslides or rock falls impacting into a water body research of these phenomena is essentially based on the two idealised water body geometries i wave flume 2d laterally confined wave propagation and ii wave basin 3d unconfined wave propagation the wave height in 2d and 3d differs by over one order of magnitude in the far field further the wave characteristics in intermediate geometries are currently not well understood this article focuses on numerical landslide tsunami propagation in the far field to quantify the effect of the water body geometry the hydrodynamic numerical model swash based on the non hydrostatic non linear shallow water equations was used to simulate approximate linear stokes cnoidal and solitary waves in 6 different idealised water body geometries this includes 2d 3d as well as intermediate geometries consisting of channels with diverging side walls the wavefront length was found to be an excellent parameter to correlate the wave decay along the slide axis in all these geometries in agreement with green s law and with diffraction theory in 3d semi theoretical equations to predict the wave magnitude of the idealised waves at any desired point of the water bodies are also presented further simulations of experimental landslide tsunami time series were performed in 2d to quantify the effect of frequency dispersion this process may be negligible for solitary and cnoidal like waves for initial landslide tsunami hazard assessment but becomes more important for stokes like waves in deeper water the findings herein significantly improve the reliability of initial landslide tsunami hazard assessment in water body geometries between 2d and 3d as demonstrated with the 2014 landslide tsunami event in lake askja

hydrographic observations in denmark strait in fall 1997 and their implications for the entrainment into the overflow plume denmark strait is the most important exit for water masses formed in the arctic mediterranean sea and supplies a substantial fraction of the north atlantic deep water observations obtained from rv aranda in august september 1997 indicate that the water crossing the 620m deep sill is mainly drawn from the intermediate waters of the east greenland current the overflow plume was stratified and capped by a less saline layer as it descended beyond 2000m the presence of a low salinity lid implies that entrainment of ambient water is small and that the downstream evolution of the plume characteristics is due to mixing within the plume between the initial overflow waters low salinity but dense water from the east greenland current flowing over the shelf may cross the shelf break south of the sill and add a less dense fraction to the overflow

applicability of smoothed particle hydrodynamics for estimation of sea wave impact on coastal structures abstract the present work describes the validation of an sph based technique for wave loading on coastal structures the so called dualsphysics numerical model has been used for the scope the attention is focused on wave impact on vertical structures and storm return walls for vertical quay walls the numerical results have been compared with analytical and semi empirical solutions later on the wave impact on storm return walls has been modelled and the results have been compared with experimental data regular and random waves have been simulated despite the model limitations e g lack of an active wave absorption system good agreement is achieved with the formulae predictions and experimental results which proves that dualsphysics model is becoming an alternative to some classical approaches and can be used as complementary tool for the preliminary design of coastal structures