the unpredictable nature of internal tides on continental shelves abstractpackets of nonlinear internal waves nliws in a small area of the mid atlantic bight were 10 times more energetic during a local neap tide than during the preceding spring tide this counterintuitive result cannot be explained if the waves are generated near the shelf break by the local barotropic tide since changes in shelfbreak stratification explain only a small fraction of the variability in barotropic to baroclinic conversion instead this study suggests that the occurrence of strong nliws was caused by the shoaling of distantly generated internal tides with amplitudes that are uncorrelated with the local spring neap cycle an extensive set of moored observations show that nliws are correlated with the internal tide but uncorrelated with barotropic tide using harmonic analysis of a 40 day record this study associates steady phase motions at the shelf break with waves generated by the local barotropic tide and variable phase motions with the shoaling of distantly generated internal tides

observations of the internal tide in monterey canyon abstract data from two shipboard experiments in 1994 designed to observe the semidiurnal internal tide in monterey canyon reveal semidiurnal currents of about 20 cm s 1 which is an order of magnitude larger than the estimated barotropic tidal currents the kinetic and potential energy evidenced by isopycnal displacements of about 50 m was greatest along paths following the characteristics calculated from linear theory these energy ray paths are oriented nearly parallel to the canyon floor and may originate from large bathymetric features beyond the mouth of monterey bay energy propagated shoreward during the april experiment itex1 whereas a standing wave that is an internal seiche was observed in october itex2 the difference is attributed to changes in stratification between the two experiments higher energy levels were present during itex1 which took place near the spring phase of the fortnightly 14 8 days cycle in sea level while itex2 occurred close to the neap phase further evide

sedimentology of a marine intermontane pleistocene gilbert type fan delta complex in the crati basin calabria southern italy the crati basin is a pliocene holocene extensional basin filled by the progradation of different types of marine fan delta systems coarse grained gilbert type fan deltas developed during the pleistocene they represent the sedimentary response to a strong differential uplift involving the basin margins and the basin itself the differential uplift was responsible for the fragmentation of the basin into several sub basins into which these fan deltas prograded the protection and lateral confinement by structural highs steep coastlines and the absence of strong tidal action in the adjacent ionian sea allowed the regular progradation of these fan deltas in the restricted gulfs and narrow embayments of the crati basin for the classical gilbert type fan deltas in lacustrine settings homopycnal inflow favours a rapid mixing of water masses and deposition of sediment close to the river mouth in the case of the example described here the density contrast between the sea water and the inflowing river water caused the separation of the muddy fraction from the coarse sandy and conglomeratic part of the sediment this allowed the development of steep mud poor coarse grained delta foresets slope instability features slump scars conglomeratic flow slides are fairly scarce in the proximal parts of the san lorenzo del vallo system towards the north where protection from the ionian sea was less they increase in importance

the latitudinal dependence of shear and mixing in the pacific transiting the critical latitude for psi abstractturbulent mixing rates are inferred from measurements spanning 25 37 n in the pacific ocean the observations were made as part of the internal waves across the pacific experiment designed to investigate the long range fate of the low mode internal tide propagating north from hawaii previous and companion results argue that near a critical latitude of 29 n the internal tide loses energy to high mode near inertial motions through parametric subharmonic instability here the authors estimate mixing from several variations of the finescale shear strain parameterization as well as thorpe scale analysis of overturns though all estimated diffusivities are modest in magnitude average diffusivity in the top kilometer shows a factor of 2 4 elevation near and equatorward of 29 n however given intrinsic uncertainty and the strong temporal variability of diffusivity observed in long mooring records the meridional mixing pattern is found to be near the edge of statistical significance

holocene relative sea level changes and coastal vegetation history at kentra moss argyll northwest scotland abstract a late holocene fall in relative sea level in northwest scotland from ca 1 3mm yr 1 to ca 1 0 mm yr 1 is interpreted from lithostratigraphic biostratigraphic chronostratigraphic and numerical analyses of fossil tidal marsh and acidic peat bog communities elevated by isostatic uplift pollen diatom and stratigraphic data from contemporary depositional environments are used to define the indicative range 0 2 m and reference water level mean high water of spring tides or highest astronomical tide of thirteen dated sea level index points no holocene intertidal sediments are recorded above 7 7 m od and all sea level index points are younger than ca 4 kyr b p in parts of kentra moss beyond the limit of holocene intertidal clastic sedimentation raised bog communities were established by at least 8 3 kyr b p these age and altitude parameters differ from those interpolated for the main postglacial shoreline but support a regional model in which isostatic uplift continues at present in the kentra moss area

on sampling the ocean using underwater gliders surface to 1000 m and back took 5 6 h and covered 5 3 km resulting in a horizontal speed of 0 26 m s 1 seasoar undulated between the surface and 400 m completing a cycle in 11 min while covering 2 6 km for a speed of 3 9 m s 1 adjacent profiles of temperature and salinity are compared between the two platforms to prove that each is accurate spray and seasoar data are compared through sections isopycnal spatial series and wave number spectra the relative slowness of the glider results in the projection of high frequency oceanic variability such as internal waves onto spatial structure the projection is caused by doppler smearing because of finite speed and aliasing due to discrete sampling the projected variability is apparent in properties measured on depth surfaces or in isopycnal depth no projected variability is seen in observations of properties on constant density surfaces because internal waves are intrinsically filtered wave number spectra suggest that projected variability affects properties at constant depth at wavelengths shorter than 30 km these results imply that isobaric quantities like geostrophic shear are valid at wavelengths longer than 30 km while isopycnal quantities like spice may be analyzed for scales as small as a glider measures

internal tidal energy fluxes in the south china sea from density and velocity measurements by gliders 1 internal tidal energy fluxes were obtained from june 2011 to august 2011 using underwater gliders in the south china sea spray gliders profiled every 2 h to 500 m which is deep enough given the shallow thermocline to compute mode 1 fluxes from vertical mode fits to tidal displacements and currents westward mode 1 diurnal and semidiurnal fluxes exceeded 40 and 30 kw m 1 to our knowledge these flux observations are the first from both velocity and density measurements by gliders fluxes compare well with a mooring near a generation site in southern luzon strait and a regional model furthermore the zonal depth structure of the internal tide is obtained by binning measurements which cover four spring neap cycles and over 100 km along 20 39 n westward phase propagation is found for currents and displacements while roughly constant phase is found along beams both these features of the phase suggest a narrow banded internal tide semidiurnal energy density is largest along a raypath which coincides with generation sites on both the eastern and western ridges in luzon strait diurnal energy density is surface intensified consistent with relatively shallower diurnal raypaths emanating from the eastern ridge

tidally generated internal wave attractors between double ridges a study is presented of the generation of internal tides by barotropic tidal flow over topography in the shape of a double ridge an iterative map is constructed to expedite the search for the closed ray paths that form wave attractors in this geometry the map connects the positions along a ray path of consecutive reflections from the surface which is double valued owing to the presence of both left and right going waves but which can be made into a genuine one dimensional map using a checkerboarding algorithm calculations are then presented for the steady state scattering of internal tides from the barotropic tide above the double ridges the calculations exploit a green function technique that distributes sources along the topography to generate the scattering and discretizes in space to calculate the source density via a standard matrix inversion when attractors are present the numerical procedure appears to fail displaying no convergence with the number of grid points used in the spatial discretizations indicating a failure of the green function solution with the addition of dissipation into the problem these difficulties are avoided leading to convergent numerical solutions the paper concludes with a comparison between theory and a laboratory experiment

a comparison between the generalized digital environmental model and levitus climatologies two ocean climatologies of temperature and salinity the generalized digital environmental model gdem and the climatological atlas of the world ocean are compared dynamic height fields are computed by season from each climatology for the north atlantic north pacific and indian oceans and are compared on a 1 latitude longitude grid large scale oceanographic features are generally found to be similarly represented in both climatologies gdem appears to render better representations of seasonal variability and regions of high current shear such as the gulf stream because of a different smoothing method and a finer grid spacing maps of dynamic heights from both climatologies are presented and their similarities and differences are discussed the methodology for the construction of gdem is also described in detail

east west asymmetry in nonlinear internal waves from luzon strait the nonhydrostatic regional ocean modeling system is applied to study the effects of thermocline shoaling deepening bathymetry and asymmetric modulated tides on the soliton growth to the west and east of luzon strait in the south china sea and western pacific ocean luzon strait comprises a shallow east ridge and a deep west ridge and its interaction with barotropic tidal currents yields strong westward internal tides that disperse into solitons satellite imagery indicates that the westward solitons are more numerous and better defined than the eastward solitons the model results show that the eastward solitons are 45 39 28 and 23 smaller than the westward solitons due to asymmetric modulated barotropic tides at the east ridge a deeper pacific ocean westward thermocline shoaling related to the kuroshio current and internal tide resonance in a double ridge configuration respectively due to the westward location of the kuroshio little thermocline deepening occurs east of the east ridge hence the influence of thermocline deepening on counteracting eastward soliton growth is small the kuroshio mainly enhances westward soliton growth the dispersion of internal tides into solitons is governed by the balance between the nonlinearity parameter on the one hand and the nonhydrostatic and coriolis dispersions on the other it is shown that this balance favors soliton growth for thermocline shoaling while it counters it for a deeper ocean a series of double ridge experiments is performed in which the distance between the ridges and the height of the west ridge are varied for a semidiurnal tidal forcing and two gaussian ridges separated by 100 km barotropic to baroclinic energy conversion is enhanced at both ridges causing larger westward internal tides and solitons the combination of coriolis forcing thermocline shoaling and a double ridge configuration enhances the distinctiveness of the so called type a and b solitons when a modulated tide occurs

recent estuarine sedimentation rates from shallow inter tidal environments in western scotland implications for future sea level trends and coastal wetland development during the mid late holocene large sections of the scottish coastline have been characterized by falling relative sea levels resulting from differential glacio isostatic uplift of this region of northern britain the complex interplay between crustal and sea level movements continues to influence the morphological development of the scottish coast a number of geophysical models predict ongoing uplift of the scottish landmass however a number of recent studies based upon the analysis of satellite altimetry data indicate a late 20th century acceleration in the rate of eustatic sea level rise detailed geochemistry radiometric dating and diatom analysis on selected sediment cores from four mature coastal marsh environments in argyll western scotland provides an opportunity to investigate the linkages between twentieth century crustal movements eustatic sea level rise and recent rates of sedimentation recorded within marsh sediments across the proposed scottish glacio isostatic uplift dome solid phase major and trace element geochemistry has been used to examine the extent to which post depositional physical disturbance and or chemical reactions may have influenced the reliability of the radiometric dating methods geochemical data indicate that the evolution of these marsh environments has not been significantly influenced by physical disturbance and overall the supply of minerogenic material to the marshes has been quite uniform vertical distributions of 210pbexcess and 137cs activity have been measured and used to develop models of recent marsh vertical accretion dating of the cores reveals subtle variations in the rates of sediment accumulation over the last c 70 years between sites for much of the last hundred years or so sedimentation rates have been in good overall agreement with various estimations for sea level rise although at the more easterly sites these estimates are generally exceeded however quasi equilibrium between marsh sedimentation and sea level rise for much of the twentieth century is indicated from the diatom analysis over the most recent period of marsh development 10 years a significant increase in the rate of surface sedimentation is recorded at all sites across the study area diatom analysis of these surface layers reveals an increase in the relative abundance of marine polyhalobous taxa in the near surface sediments this signifies a very recent increase in the rate of regional relative sea level rise indicating that a regional threshold in coastal forcing has now been exceeded these findings provide clear evidence that recent relative sea level rise is now outpacing estimated rates of glacio isostatic adjustment gia across the proposed scottish uplift dome

poleward flows in the southern california current system glider observations and numerical simulation 1 three years of continuous spray glider observations in the southern california current system ccs are combined with a numerical simulation to describe the mean and variability of poleward flows in the southern ccs gliders provide upper ocean observations with good across shore and temporal resolution along two across shore survey lines while the numerical simulation provides a dynamically consistent estimate of the ocean state persistent poleward flows are observed in three areas within 100 km of the coast at point conception within the southern california bight scb and offshore of the scb and the santa rosa ridge srr poleward transport by the flows within the scb and offshore of the srr exceeds the poleward transport off point conception suggesting that the poleward flows are not continuous over the 225 km between observation lines the numerical simulation shows offshore transport between the survey lines that is consistent with some of the poleward flow turning offshore before reaching point conception the poleward current offshore of the srr is unique in that it is strongest at depths greater than 350 m and it is observed to migrate westward away from the coast this westward propagation is tied to westward propagating density anomalies originating in the scb during the spring summer upwelling season when wind stress curl is most strongly positive the across shore wave number frequency and phase speed of the westward propagation and the lack of across shore transport of salinity along isopycnals are consistent with first mode baroclinic rossby dynamics

surface manifestation of internal tides in the deep ocean observations from altimetry and island gauges the sea surface height signatures of internal tides in the deep ocean amounting to a few centimeters or less are studied using two complementary measurement types satellite altimetry and island tide gauges altimetry can detect internal tides that maintain coherence with the astronomical forcing island gauges can monitor temporal variability which in some circumstances is due to internal tides varying in response to changes in the oceanic medium this latter mechanism is at work at hilo and other stations on the northern coasts of the hawaiian islands by detecting spatially coherent low frequency internal tide modulations the tide gauges along with inverted echo sounders at sea suggest that the mean internal tide is also spatially coherent satellite altimetry confirms this at hawaii and in many other places topex poseidon altimetry detects mean surface waves spatially coherent and propagating great distances 1000 km before decaying below background noise when temporal variability is small the altimetry plus information on ocean density sets useful constraints on energy fluxes into internal tides at the hawaiian ridge 15 gw of tidal power is being converted from barotropic to first mode baroclinic motion examples elsewhere warn that a simplistic interpretation of the altimetry without regard to variability noise or in situ information may be highly misleading with such uncertainties extension of the hawaiian results into a usefully realistic estimate of the global internal tide energy balance appears premature at this time

propagation of internal tides generated near luzon strait observations from autonomous gliders 1 the vertical isopycnal displacements associated with internal waves generated by the barotropic tidal currents in the vicinity of luzon strait are estimated using measurements collected by autonomous underwater gliders nearly 23 000 profiles from seagliders and spray gliders collected during 29 different missions since 2007 are used to estimate the amplitude and phase of the linear semidiurnal and diurnal internal waves in this energetic region particularly in the previously poorly sampled area near the eastern ridge and on the pacific side of luzon strait the mean and variability of the internal wave field in the upper 1000 m of the water column are described the phase progression of internal waves as they propagate away from their generation sites is captured directly the glider based observations are used to map the mode 1 semidiurnal and diurnal internal wave fields providing the baroclinic energy flux over a roughly 600 km 800 km region based strictly on in situ observations

three dimensional nonhydrostatic numerical simulation of nonlinear internal wave generation and propagation in the south china sea 1 we present the results of three dimensional nonhydrostatic simulations of internal tides and waves in the south china sea scs using the suntans model model results accurately predict the observed wave arrival times at two mooring locations in the scs internal wave amplitudes are underpredicted which causes underprediction of internal wave speeds due to a lack of amplitude dispersion we show that the well known a and b waves arise from the steepening of semidiurnal internal tides that are generated due to strong barotropic flow over ridges in the luzon strait a wave generation is stronger in the southern portion of the luzon strait because diurnal internal tidal beams augment the amplitude of the semidiurnal a waves b wave generation is stronger in the northern portion where the distance between the eastern and western ridges is approximately equal to one internal tidal wavelength and leads to semidiurnal internal tidal resonance the orientation of the ridges produces large a waves that propagate into the northern portion of the western scs basin and stronger b waves that propagate into the southern portion when traced back in time along linear characteristics a waves consistently line up close to peak ebb eastward barotropic currents while b waves consistently line up with peak flood westward barotropic currents this reinforces the notion that the lee wave mechanism and associated hydraulic or nonlinear effects are weak as demonstrated by a simple linear model relating the amplitude of the simulated waves to the excursion parameter at the ridges

interaction of basin margin faults and tidal currents on nearshore sedimentary architecture and composition a case study from the early miocene of northern hungary abstract the darno conglomerate and the petervasara sandstone with conglomeratic intercalations both cropping out in northern hungary were formed along the eastern margin of the shallow early miocene sea within the carpathian arc ophiolite derived clastic components in both formations indicate a close genetic relationship with each other and with the activity of the basin margin darno fault which seems to correspond with the coeval shoreline the darno conglomerate was part of a small fault controlled fan delta supplying coarse clastics into the sea where the petervasara sandstone deposited the conglomerates occur as small lobes interbedded within a field of tidally driven sand waves the coarse grained clastics which were admixed to the main material of the sandstone have been derived from triassic jurassic ophiolite related series meliata nappes east of the darno fault the composition of the lobes indicates that they were formed as small spit like platforms attached to the fan deltas of the darno conglomerate as base level rose spits became drowned and their sediment was washed into the basin and reworked by the strong northward directed tidal currents into elongated lobes mimicking sand waves a reduction in the amount of the less resistant pebble components of ophiolite related origin and a relative enrichment of the resistant components towards the west indicate that pebbles had partly been transported in the offshore direction the increasing rate of accumulation of ophiolite derived heavy minerals and pebbles along the northern part of the coast indirectly suggests a contemporaneous left lateral displacement along the basin margin darno fault

trapped diurnal internal tides propagating semidiurnal internal tides and mixing estimates in the california current system from sustained glider observations 2006 2012 abstract from 2006 2012 along 3 repeated cross shore transects california cooperative oceanic fisheries investigations lines 66 7 80 and 90 in the california current system 33 609 shear and 39 737 strain profiles from 66 glider missions are used to estimate mixing via finescale parameterizations from a dataset containing over 52 000 profiles elevated diffusivity estimates and energetic diurnal d1 and semidiurnal d2 internal tides are found a within 100 km of the coast on lines 66 7 and 80 and b over the santa rosa cortes ridge srcr in the southern california bight scb on line 90 while finding elevated mixing near topography and associated with internal tides is not novel the combination of resolution and extent in this ongoing data collection is unmatched in the coastal ocean to our knowledge both d1 and d2 internal tides are energy sources for mixing at these latitudes the d1 internal tide is subinertial on line 90 d1 and d2 tides are equally energetic over the srcr the main site of elevated mixing within the scb numerous sources of internal tides at the rough topography in the scb produce standing and or partially standing waves on lines 66 7 and 80 the dominant energy source below about 100 m for mixing is the d1 internal tide which has an energy density of the d2 internal tide on line 80 estimated diffusivity estimated dissipation and d1 energy density peak in summer the d1 energy density shows an increasing trend from 2006 to 2012 its amplitude and phase are mostly consistent with topographically trapped d1 internal tides traveling with the topography on their right the observed offshore decay of the diffusivity estimates is consistent with the exponential decay of a trapped wave with a mode 1 rossby radius of 20 30 km despite the variable mesoscale it is remarkable that coherent internal tidal phase is found

holocene relative sea level changes on the margin of a glacio isostatically uplifted area an example from northern caithness scotland evidence is presented for holocene relative sea level changes on the margin of a glacio isostatically uplifted area the lower wick river valley northern caithness scotland lithostratigraphic b

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

global patterns of low mode internal wave propagation part i energy and energy flux abstract extending an earlier attempt to understand long range propagation of the global internal wave field the energy e and horizontal energy flux f are computed for the two gravest baroclinic modes at 80 historical moorings around the globe with bandpass filtering the calculation is performed for the semidiurnal band emphasizing m2 internal tides generated by flow over sloping topography and for the near inertial band emphasizing wind generated waves near the coriolis frequency the time dependence of semidiurnal e and f is first examined at six locations north of the hawaiian ridge e and f typically rise and fall together and can vary by over an order of magnitude at each site this variability typically has a strong spring neap component in addition to longer time scales the observed spring tides at sites northwest of the hawaiian ridge are coherent with barotropic forcing at the ridge but lagged by times consistent with travel at the theoretical mode 1 group speed from the ridge phase c

patterns of isostatic land uplift during the holocene evidence from mainland scotland preliminary results of a lengthy and detailed investigation into middle and late holocene raised shorelines in mainland scotland indicate that three shorelines are sufficiently widely distributed to permit an examination of their extent and of the patterns of uplift which they indicate the shorelines are the storegga tsunami shoreline reached at c 7100 14c years bp at the culmination of the main postglacial transgression and the blairdrummond shoreline reached after the main postglacial shoreline at c 2000 4200 14c years bp at the time of a tsunami believed to have been caused by the second storegga submarine slide the main postglacial shoreline reached at c 5800 6850 14c years bp the main postglacial shoreline previously believed to be the highest holocene raised shoreline in scotland is now believed to be overlapped around the periphery of the uplifted area by the later blairdrummond shoreline isobase models based upon quadratic trend surface analysis of available comparable height dat

reduced mixing from the breaking of internal waves in equatorial waters in the oceans heat salt and nutrients are redistributed much more easily within water masses of uniform density than across surfaces separating waters of different densities but the magnitude and distribution of mixing across density surfaces are also important for the earth s climate as well as the concentrations of organisms most of this mixing occurs where internal waves break overturning the density stratification of the ocean and creating patches of turbulence predictions of the rate at which internal waves dissipate were confirmed earlier at mid latitudes here we present observations of temperature and velocity fluctuations in the pacific and atlantic oceans between 42 degrees n and 2 degrees s to extend that result to equatorial regions we find a strong latitude dependence of dissipation in accordance with the predictions in our observations dissipation rates and accompanying mixing across density surfaces near the equator are less than 10 of those at mid latitudes for a similar background of internal waves reduced mixing close to the equator will have to be taken into account in numerical simulations of ocean dynamics for example in climate change experiments

basin dimensions and morphology as controls on amplification of tidal motions the early miocene north hungarian bay following the late aquitanian sea level fall tide influenced deposition started in the north hungarian bay an embayment in the paratethys open to the north east the relatively narrow funnel shape of the bay supported amplification of tidal movements resulting in the generation of strong tidal currents the length and the depth of the north hungarian bay and the connecting seaway through east slovakia fell into the tidal amplification window and thus fulfilled the conditions needed for resonant amplification of semidiurnal m2 tides tide influenced deposits were formed at both sides of the north hungarian bay they reflect dominant currents in opposite directions and of different strengths at either side of the basin this difference was the result of bottom tide interactions cyclonic anticlockwise residual currents were induced above the asymmetrical central depression in the bay and were superimposed upon the tidal currents producing an anticlockwise time and velocity asymmetrical current system the north hungarian bay and other examples show that amplification of tidal motions and formation of tide influenced deposits may occur if basin dimensions pass through the tidal amplification window this window represents ideal conditions for resonant or amphidromic amplification of tidal currents it determines an ideal length depth or width depth ratio relative to the wavelength of the astronomical tides thus signs of strong tidal influence in fossil basin fills can be used to reconstruct the dimensions length depth and width of such basins

remote sensing evidence for baroclinic tide origin of internal solitary waves in the northeastern south china sea 1 evidence for baroclinic tide origin of internal solitary waves isws in the northeastern south china sea is presented based on 116 internal wave packets observed in satellite images from 1995 to 2001 these wave packets can be divided into two types a single wave isw packet containing only one isw with without an oscillating tail and a multiple wave isw packet composed of a group of rank ordered isws all of the 22 single wave isw packets occur in the deep water zone it is suggested that the isws instead of being generated by the lee wave mechanism are developed by nonlinear steepening of the baroclinic tides which are produced by the strong tidal currents flowing over a ridge in luzon strait this suggestion is verified by an ers 2 sar image which records such an evolution process from a baroclinic tide to a single isw in its spatial domain

from tides to mixing along the hawaiian ridge the cascade from tides to turbulence has been hypothesized to serve as a major energy pathway for ocean mixing we investigated this cascade along the hawaiian ridge using observations and numerical models a divergence of internal tidal energy flux observed at the ridge agrees with the predictions of internal tide models large internal tidal waves with peak to peak amplitudes of up to 300 meters occur on the ridge internal wave energy is enhanced and turbulent dissipation in the region near the ridge is 10 times larger than open ocean values given these major elements in the tides to turbulence cascade an energy budget approaches closure

river mouth processes in a fjord delta british columbia canada abstract the bella coola delta is a high energy coarse grained fjord delta situated in the coast mountains of british columbia river mouth processes are directly related to the large tidal range 3 9 m mean 5 9 m large which changes the location and nature of distributary mouths producing distinct high tide and low tide outlets frictional forces dominate at high tide as the effluent disperses through five dynamic zones producing a radial bar a friction model applies to this outlet during low tide frictional inertial and buoyant forces and an internal hydraulic jump control the development of six dynamic zones and a lunate middle ground bar a buoyant plane jet model qualitatively best approximates low tide outlet dynamics

three dimensional numerical simulation of m2 internal tides in the east china sea the east china sea and adjacent seas are one of the most significant generation regions of the m 2 internal tide in the world s oceans in the present study we investigate the distribution and energetics of the m 2 internal tide around the continental shelf edge in the east china sea using a three dimensional numerical model the numerical experiment shows that m 2 internal tides are effectively generated over prominent topographic features such as the subsurface ridges in the bashi luzon and tokara straits the ridges along the ryukyu island chain and the continental shelf slope in the east china sea the former particularly so all of these topographic features are characterized by steep slopes at the depth of the thermocline onto which the m 2 barotropic tide is almost normally incident the m 2 internal tides propagating away from these multiple source regions interfere with each other to create a complicated wave pattern it is found that the calculated pattern of the m 2 internal tide agrees well with topex poseidon altimeter observations the conversion rate from m 2 barotropic to baroclinic energy over the whole analyzed model domain is estimated to be 35 gw roughly 10 of the energy in the m 2 surface tide incident on the prominent topographic features is converted to the m 2 internal tide although about half of the m 2 internal tidal energy is subject to local dissipation in close proximity to the generation sites

patterns of holocene relative sea level change in the north of britain and ireland temporal and spatial patterns of relative sea level rsl change in the north of britain and ireland during the holocene are examined four episodes each defined by marked changes in the rsl trend are identified each episode is marked by a rise to a culminating shoreline followed by a fall episode hrsl 1 dates from the younger dryas to early in the holocene hrsl 2 to hrsl 4 occurred later in the holocene there is extensive evidence for each episode and on this basis the spatial distribution of the altitude data for three culminating shorelines and a shoreline formed at the time of the holocene storegga slide tsunami ca 8110 100 cal bp is analysed ordinary kriging is used to determine the general pattern following which gaussian trend surface analysis is employed recognising that empirical measurements of rsl change can be unevenly distributed spatially a new approach is introduced which enables the developing pattern to be identified the patterns for the most widely occurring shorelines were analysed and found to be similar and common centre and axis models were developed for all shorelines the analyses described provide models of the spatial pattern of holocene rsl change in the area between ca 8100 cal bp and ca 1000 cal bp based on 2262 high resolution shoreline altitude measurements these models fit the data closely no shoreline altitude measurement lying more than 1 70 m or 1 82 m from the predicted value the models disclose a similar pattern to a recently published glacial isostatic adjustment model for present rsl change across the area indicating that the overall spatial pattern of rsl change may not have varied greatly during the last ca 8000 years

quaternary sea level changes in western scotland abstract in recent years major advances have been made in our understanding of late quaternary sea level changes in western scotland in particular new hypotheses have been advanced to explain the ages and origins of high level rock platform fragments and high level marine shell beds certain raised shorelines in islay and jura sw argyll and wester ross have been related to former margins of the last ice sheet and are associated with drops in the lateglacial marine limit in some areas the decline in lateglacial sea level took place in association with a stationary ice margin while in others the fall in sea level occurred in conjunction with considerable ice retreat during the lateglacial interstadial relative sea level fell rapidly between ca 13 and ca 12 ka bp and thereafter more slowly until ca 11 ka bp renewed marine erosion during the cold climate of the loch lomond younger dryas stadial ca 11 10 ka bp resulted in the production of the main lateglacial shoreline which declines in altitude to the w sw and s away from the centre of glacio isostatic uplift in the w highlands the shoreline has a maximum altitude of 10 11 m o d in the oban area and passes below sea level in ne islay ardnamurchan colonsay w mull kintyre and arran during the early holocene a pronounced marine transgression took place probably culminating between 6 6 and 7 0 ka bp the culmination of the transgression is represented by the main postglacial shoreline that reaches a maximum altitude of ca 14 m in the oban area and declines gently in altitude away from the centre of glacio isostatic uplift reconstruction of the uplift isobases for this shoreline appears to indicate a slight eastward migration of the uplift centre since the younger dryas in peripheral areas of western scotland the main postglacial shoreline is not present owing to the effect of holocene submergence

inner shelf seismic stratigraphy off the north coast of northern ireland new data on the depth of the holocene lowstand new seismic stratigraphic data are presented from the inner shelf off the north coast of northern ireland the sequence preserved comprises an acoustic basement of till or solid bedrock overlain by a fine grained acoustically transparent unit interpreted as glacio marine sediment this is overlain by an upper reflective sandy unit which contains a discontinuous but widespread internal reflector interpreted as peat that developed during a late glacial holocene relative sea level fall and continued to accumulate until subsequent inundation the depth of the holocene lowstand is estimated at 30 in msl on the basis of the seaward extent of the sandy unit and its intercalated peaty horizons the presence of erosional notches and a widespread break in slope at this depth the lowstand is not definitively dated but on the basis of dated deposits in adjacent locations is inferred to have occurred between 10 000 and 11000 14c yr bp c 2002 elsevier science b v all rights reserved

tertiary evolution of the intra carpathian area a model abstract the outer carpathian flysch nappes encircle an intra carpathian domain which can be divided into two megatectonic units north pannonian and tisza mostly on the basis of contrasting mesozoic and palaeogene facies development we see two major kinematic problems to be solved 1 1 the present distribution of the mesozoic and palaeogene facies is mosaic like and some belts form exotic bodies within realms of austroalpine affinity 2 2 late eocene palinspastic reconstruction of the outer carpathian flysch nappes suggest that the entire intra carpathian area must have been located several hundreds of kilometres to the south and to the west of its present position neogene extension can account for shortening in the external carpathian nappes but is unable to explain mesozoic facies anomalies and offsets of palaeogene formations we suggest that evolution of the intra carpathian area involved first late palaeogene early miocene juxtaposition of the north pannonian and tisza megatectonic units accompanied by the closure of the external carpathian flysch troughs thereafter extension of this amalgamated unit occurred which was compensated by thrusting of flysch nappes onto the european foreland and formation of molasse foredeeps eastward escape of the north pannonian unit from the alpine collisional belt involved left lateral shear along the pieniny klippen belt and right lateral shear along the mid hungarian zone parts of the late palaeogene basin and an early miocene volcanic edifice were dissected offset and elongated by several 100 kms the driving mechanism of the eastward escape of the intra carpathian area can be related to the collision of apulia and europe and the subduction of the external carpathian crust under the pannonian units the escape ceased gradually in the early miocene when oblique collision between the north pannonian unit and european continent occurred neogene extension of the pannonian region was an areal deformation the extension at locally variable rate resulted in the break up of the heterogenous floor of the neogene basin the driving mechanism of basin extension and contemporaneous compressional deformation of the external carpathians is thought to be related to ongoing subduction involving the marginal part of the attenuated european continental crust tectonic activity in the carpathians and basin subsidence and volcanism shifted in time and in unison from the west toward the east southeast

early miocene basin evolution in northern hungary tectonics and eustasy abstract it is presumed that the oligocene early miocene basin evolution in northern hungary was primarily driven by compressional tectonics producing a major second order transgressive regressive facies cycle the early miocene basin evolution is best understood in terms of molasse sedimentation in an overfilled flexural basin during this time the gradual cessation of thrusting in the adjacent west carpathian thrust fold belt resulted in its uplift and subaerial exposure significant amounts of sediment were delivered to the flexural basin filling it up to sea level during the late stage uplift of the flexural basin a shallow marine depositional environment developed as a result of isostatic rebound and signals of third order eustatic sea level changes can be revealed sedimentological studies of outcrops of the lower miocene succession proved marked changes in facies along the gently dipping distal southeastern flank of the basin a sudden inception of shallow marine coarse elastics on top of siltstones deposited in significantly deeper water may have been the result of a third order eustatic sea level fall shortly before the burdigalian at the boundary of the nn1 nn2 nannofossil zones during the resulting lowstand various tide dominated facies aggraded which were subsequently flooded by the burdigalian sea level rise the highstand is represented by upwards shallowing progradational units due to accelerating sedimentation and or tectonic uplift the typically elongated and narrow flexural basin characterized by small water depth had dimensions which were particularly suitable for the amplification of tidal motions this resulted in the deposition of tide influenced sandy sediments in contrast to examples where the evolution of a strong tidal influence is related to transgressions here such conditions developed following a drop of sea level

model estimates of m2 internal tide energetics at the hawaiian ridge 1 a primitive equation model is used to examine the structure and energetics of m 2 internal tides generated at the hawaiian ridge recent estimates based on altimeter data suggest that 20 gw of barotropic tidal dissipation occurs at the ridge with conversion to internal tides believed to be the dominant dissipation mechanism the model simulates an internal tide that accounts for 9 7 gw of radiated energy away from the ridge in the northeast and southwest directions the strongest generation occurs at three sites where enhanced barotropic currents flow across elongated topographic features the depth integrated baroclinic energy flux and energy densities at these sites are on the order of 10 4 w m 1 and 10 4 j m 2 respectively a modal decomposition indicates that 62 of the outgoing energy flux is accounted for by the first internal mode 15 is accounted for by the second mode and less than 5 is accounted for by each subsequent higher mode the tidal dissipation due to bottom friction along the ridge is estimated to be 0 1 gw the level of turbulent dissipation near the ridge owing to tidal energy conversion remains to be determined to assess fully the barotropic baroclinic energy budget

the formation and fate of internal waves in the south china sea internal oceanic waves are subsurface gravity waves that can be enormous and travel thousands of kilometres before breaking but they are difficult to study here observations of such waves in the south china sea reveal their formation mechanism extreme turbulence relationship to the kuroshio current and energy budget internal waves are the underwater version of more familiar surface waves they can be enormous and travel thousands of kilometres before breaking the south china sea is known to be home to the largest internal waves in the world s oceans but their size generation mechanisms and role in the regional energy budget are unknown matthew alford and colleagues now present the results from the iwise observational campaign and reveal that internal waves more than 200 metres high break in the south china sea and create turbulence that is orders of magnitude larger than in the open ocean and that wave formation is influenced by the kuroshio current these results now allow for a complete energy budget of the south china sea and for a more accurate incorporation of internal waves into climate models internal gravity waves the subsurface analogue of the familiar surface gravity waves that break on beaches are ubiquitous in the ocean because of their strong vertical and horizontal currents and the turbulent mixing caused by their breaking they affect a panoply of ocean processes such as the supply of nutrients for photosynthesis1 sediment and pollutant transport2 and acoustic transmission3 they also pose hazards for man made structures in the ocean4 generated primarily by the wind and the tides internal waves can travel thousands of kilometres from their sources before breaking5 making it challenging to observe them and to include them in numerical climate models which are sensitive to their effects6 7 for over a decade studies8 9 10 11 have targeted the south china sea where the oceans most powerful known internal waves are generated in the luzon strait and steepen dramatically as they propagate west confusion has persisted regarding their mechanism of generation variability and energy budget however owing to the lack of in situ data from the luzon strait where extreme flow conditions make measurements difficult here we use new observations and numerical models to 1 show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena 2 reveal the existence of 200 metre high breaking internal waves in the region of generation that give rise to turbulence levels 10 000 times that in the open ocean 3 determine that the kuroshio western boundary current noticeably refracts the internal wave field emanating from the luzon strait and 4 demonstrate a factor of two agreement between modelled and observed energy fluxes which allows us to produce an observationally supported energy budget of the region together these findings give a cradle to grave picture of internal waves on a basin scale which will support further improvements of their representation in numerical climate predictions

turbulent dissipation on the margins of the south china sea 1 measurements of turbulence along the continental slope shelfbreak and shelf of the northern south china sea are presented from a 10 day measurement program during april 2005 the shelfbreak region was characterized by a deep stratification that appears to be typical of the late winter monsoon this appears to shift the wave field at the shelfbreak from the soliton like depression anomalies observed in previous years to a more complex wave field supporting high frequency waves in both upper and lower depth intervals of the water column on average 30 of the depth integrated turbulent dissipation occurs within 10 m of the bottom where baroclinic energy is preferentially dissipated dissipation levels reaching 50 mw m2 are an order of magnitude larger than those attainable through frictional dissipation of the local barotropic tide and an order of magnitude larger than levels typical in the open ocean

high frequency internal waves near the luzon strait observed by underwater gliders 1 tidal flow through the luzon strait produces large internal waves that propagate westward into the south china sea and eastward into the pacific underwater gliders gathered sustained observations of internal waves during seven overlapping missions from april 2007 through july 2008 a particular focus is the high frequency internal waves where the operational definition of high involves periods shorter than a glider profile taking 3 6 h internal wave vertical velocity is estimated from measurements of pressure and glider orientation through two methods 1 use of a model of glider flight balancing buoyancy and drag along the glider path and 2 high pass filtering of the observed glider vertical velocity by combining high frequency vertical velocities from glider flight with low frequency estimates from isopycnal depth variations between dives a spectrum covering five decades of frequency is constructed a map of the standard deviation of vertical velocity over the survey area shows a decay from the luzon strait into the pacific the growth of high frequency vertical velocity with propagation into the south china sea is observed through two 2 week time series stations the largest observed vertical velocities are greater than 0 2 m s 1 and are associated with displacements approaching 200 m the high frequency waves are observed at regular intervals of 1 day as they ride on diurnal tidal internal waves generated in the strait

combination of palaeomagnetic and stress data a case study from north hungary abstract the paper presents the results of a combined palaeomagnetic and microtectonic study in north hungary it analyses the relationship between palaeomagnetically indicated rotations and stress axes at both site and regional level as a result appropriate palaeomagnetic corrections are determined for different sets of microtectonic structures the orientation of the stress axes is restored to its original position by correcting for mass rotation as it is manifested in declination deviation from the present north this process eliminates the apparent rotation of the stress field during the early miocene however our investigations show that real change in orientation of stress axes about 20 did occur during the middle miocene the reconstructed stress field is in good agreement with kinematic models which suggest eastward escape of the area as part of the north pannonian block our results may be best interpreted by attributing the palaeomagnetically indicated rotations partly to rotation of the whole area as a relatively rigid body and partly to local block rotations

observations of tidal internal wave beams at kauai channel hawaii abstract to observe the across ridge structure of internal tides density and velocity were measured using seasoar and a doppler sonar over the upper 400 600 m of the ocean extending 152 km on each side of the hawaiian ridge at kauai channel eighteen sections were completed in about 18 days with sampling intentionally detuned from the lunar semidiurnal m2 tide so that averaging over all sections was equivalent to phase averaging the m2 tide velocity and displacement variance and several covariances involving velocity and displacement showed one m2 internal wave beam on each side of the ridge and reflection of the beams off of the surface theoretical ray slopes aligned with the observed beams and originated from the sides of the ridge energy flux was in agreement with internal wave generation at the ridge inferred turbulent dissipation was elevated relative to open ocean values near tidal beams energy flux was larger than total dissipation almost everywhere across the ridge internal wave energy fl

incoherent nature of m2 internal tides at the hawaiian ridge abstractmoored current temperature and conductivity measurements are used to study the temporal variability of m2 internal tide generation above the kaena ridge between the hawaiian islands of oahu and kauai the energy conversion from the barotropic to baroclinic tide measured near the ridge crest varies by a factor of 2 over the 6 month mooring deployment 0 5 1 1 w m 2 the energy flux measured just off the ridge undergoes a similar modulation as the ridge conversion the energy conversion varies largely because of changes in the phase of the perturbation pressure suggesting variable work done on remotely generated internal tides during the mooring deployment low frequency current and stratification fluctuations occur on and off the ridge model simulations suggest that these variations are due to two mesoscale eddies that passed through the region the impact of these eddies on low mode internal tide propagation over the ridge crest is considered it appears that eddy related changes in stratif

energy flux and dissipation in luzon strait two tales of two ridges abstractinternal tide generation propagation and dissipation are investigated in luzon strait a system of two quasi parallel ridges situated between taiwan and the philippines two profiling moorings deployed for about 20 days and a set of nineteen 36 h lowered adcp ctd time series stations allowed separate measurement of diurnal and semidiurnal internal tide signals measurements were concentrated on a northern line where the ridge spacing was approximately equal to the mode 1 wavelength for semidiurnal motions and a southern line where the spacing was approximately two thirds that the authors contrast the two sites to emphasize the potential importance of resonance between generation sites throughout luzon strait baroclinic energy energy fluxes and turbulent dissipation were some of the strongest ever measured peak to peak baroclinic velocity and vertical displacements often exceeded 2 m s 1 and 300 m respectively energy fluxes exceeding 60 kw m 1 were measured at spring tide at the wester

holocene coastal evolution and uplift mechanisms of the northeastern raukumara peninsula north island new zealand abstract the coastal geomorphology of the northeastern raukumara peninsula new zealand is examined with the aim of determining the mechanisms of holocene coastal uplift elevation and coverbed stratigraphic data from previously interpreted coseismic marine terraces at horoera and waipapa indicate that despite the surface morphology there is no evidence that these terraces are of marine or coseismic origin early holocene transgressive marine deposits at hicks bay indicate significant differences between the thickness of preserved intertidal infill sediments and the amount of space created by eustatic sea level rise therefore uplift did occur during early holocene evolution of the estuary the palaeoecology and stratigraphy of the sequence shows no evidence of sudden land elevation changes beach ridge sequences at te araroa slope gradually toward the present day coast with no evidence of coseismic steps the evolution of the beach ridges was probably controlled by sediment supply in the context of a background continuous uplift rate no individual dataset uniquely resolves the uplift mechanism however from the integration of all evidence we conclude that holocene coastal uplift of this region has been driven by a gradual aseismic mechanism an important implication of this is that tectonic uplift mechanisms do vary along the east coast of the north island this contrasts with conclusions of previous studies which have inferred holocene coastal uplift along the length of the margin was achieved by coseismic events this is the first global example of aseismic processes accommodating uplift at rates of 1 mm yr 1 adjacent to a subduction zone and it provides a valuable comparison to subduction zones dominated by great earthquakes

palaeogeographic significance of tidal deposits an example from an early miocene paratethys embayment northern hungary abstract tide influenced deposits can be used in palaeogeographic reconstructions because they are good indicators of open marine connections an example is presented from the eggenburgian late aquitanian early burdigalian of the north hungarian bay this bay was part of an inland sea the paratethys tide influenced deposits prove that tidal motions in the north hungarian bay were locally amplified this required a free propagation of tidal waves from the open ocean through the paratethys into this embayment since all seaways towards the mediterranean were closed during the early eggenburgian the only connection between the north hungarian bay and open marine waters which allowed the transmission of tidal waves was the outlet towards the east slovakian basin in the northeast the presence of tide influenced deposits in the north hungarian bay implies that tidal waves entered the eastern paratethys from the east through a wide passage other examples of lower miocene tide influenced deposits in the mediterranean and paratethian regions are reported from different periods in these cases amplification of tidal motions in various embayments and straits also occurred because of the local basin morphology it is demonstrated that significant palaeogeographic changes during the early miocene resulted in changes of current pathways and related shifts of loci of tide influenced deposition

energy of nonlinear internal waves in the south china sea 1 four sets of adcp measurements were taken in the south china sea scs these results were combined with previous satellite observations and internal tide numerical model results analysis suggests that strong internal tides are generated in luzon strait propagate as a narrow tidal beam into the scs are amplified by the shoaling continental slope near tungsha island become nonlinear and evolve into high frequency nonlinear internal waves niw internal waves in the scs have geographically distinct characteristics 1 west of luzon strait the total internal wave energy eiw is 10 that predicted by garrett munk spectra egm levine 2002 there is no sign of niw 2 near tungsha island eiw 13 egm strong nonlinear and high harmonic tides are present repetitive trains of large amplitude niw appear primarily at a semidiurnal periodicity with their amplitudes modulated at a fortnightly tidal cycle the rms vertical velocity of niw shows a clear spring neap tidal cycle and is linearly proportional to the barotropic tidal height in luzon strait with a 1 85 day time lag consistent with the travel time of internal tides from luzon strait to tungsha island 3 at the northern scs shelfbreak eiw 4 egm single depression waves are found but no multiple waves packets are evident 4 on the continental shelf eiw 2 egm both depression and elevation niw exist

the incidence of microscopic charcoal in late glacial deposits abstract microscopic charcoal is not routinely counted by those investigating late glacial deposits it is largely the domain of those pursuing anthropogenic questions relating to the holocene interglacial 23 sites dating to the devensian late glacial ca 13 000 10 000 14c yr bp in scotland have charcoal records and seven of these can be shown to have a high charcoal content a phenomenon that has passed largely unremarked we discuss patterns of charcoal representation and explore possible explanations for high charcoal abundances especially in the loch lomond stadial including taphonomy e g secondary erosion of charcoal bearing deposits long distance transport aridity especially during the loch lomond stadial warmth and effective precipitation especially during the late glacial interstadial and humanly caused fires upper palaeolithic available data do not allow the establishment of clear relationships between vegetation types and charcoal abundance it is suggested that patterns of burning may need to be considered in the context of arid wet shifts in climate it is probable that combinations of factors are responsible for the late glacial charcoal records but the difficulty remains that too few data are routinely collected or available for study

the generation of internal tides at the hawaiian ridge previous analyses of altimeter and acoustic data indicate that the hawaiian ridge is a significant generation site for semidiurnal m2 period internal waves owing to tidal flow over topography such waves likely play an important role connecting the dissipation of tidal energy to ocean mixing here a primitive equation numerical model with realistic stratification bathymetry and tidal forcing is used to simulate the generation of these waves in a manner consistent with altimeter sea surface observations the highest amplitude waves originate at three generation sites located at both the island and seamount portions of the chain these sites have in common both enhanced flows across ridge shaped topography and maxima in model calculated body force which couples barotropic and baroclinic motions the model vertical structure suggests the presence of multiple dynamical modes within 100 km of the ridge and not just the lowest modes that have been detected at the sea surface

towards improved empirical isobase models of holocene land uplift for mainland scotland uk a new approach to modelling patterns of glacio isostatic land uplift during the holocene in mainland scotland uk is described the approach is based upon altitude measurements at the inner margin or locally highest point of raised estuarine surfaces dated by radiocarbon assay supported by microfossil analyses 2241 altitudes have been analysed by a technique new to studies of former sea levels gaussian trend surface analysis and isobase models for four holocene shorelines the holocene storegga slide tsunami shoreline abandoned rapidly circa 7900 sidereal years bp the main postglacial shoreline abandoned during circa 6400 7700 sidereal years bp the blairdrummond shoreline abandoned during circa 4500 5800 sidereal years bp and a speculative fourth shoreline the wigtown shoreline abandoned during circa 1520 3700 sidereal years bp are shown in a series of maps the implications of the shoreline patterns for glaicio isostasy in the area are discussed it is maintained that the statistical technique used enables broad estimates to be made of nearshore sea surface change

interference pattern and propagation of the m2 internal tide south of the hawaiian ridge abstract most of the m2 internal tide energy generated at the hawaiian ridge radiates away in modes 1 and 2 but direct observation of these propagating waves is complicated by the complexity of the bathymetry at the generation region and by the presence of interference patterns observations from satellite altimetry a tomographic array and the r p flip taken during the farfield program of the hawaiian ocean mixing experiment home are found to be in good agreement with the output of a high resolution primitive equation model simulating the generation and propagation of internal tides the model shows that different modes are generated with different amplitudes along complex topography multiple sources produce internal tides that sum constructively and destructively as they propagate the major generation sites can be identified using a simplified 2d idealized knife edge ridge model four line sources located on the hawaiian ridge reproduce the interference pattern of sea surface height and energy fl

rapid holocene relative sea level changes in gruinart isle of islay scottish inner hebrides litho and biostratigraphic analyses undertaken in the gruinart estuary central islay reveal a detailed sedimentary record of holocene relative sea level changes and high energy flood events during the last 10 000 years during the lateglacial holocene transition relative sea level had fallen to below c 0 5 m od and remained at this depth until c 8830 14c years bp thus the early holocene minimum sea level is here relatively well constrained altitudinally a sustained and largely uninterrupted rise in relative sea level took place after c 8500 14c years bp reaching a maximum altitude of c 4 5 m od and remained at an elevation of c 4 m od until c 2000 14c years bp both the recorded maximum altitude of the main holocene transgression and the late age of the relative marine regression are incompatible with published shoreline uplift isobase models for this area

propagation of low mode internal waves through the ocean abstract the baroclinic tides play a significant role in the energy budget of the abyssal ocean although the basic principles of generation and propagation are known a clear understanding of these phenomena in the complex ocean environment is only now emerging to advance this effort a ray model is developed that quantifies the effects of spatially variable topography stratification and planetary vorticity on the horizontal propagation of internal gravity modes the objective is to identify baroclinic shoals where wave energy is spatially concentrated and enhanced dissipation might be expected the model is then extended to investigate the propagation of internal waves through a barotropic mesoscale current field the refraction of tidally generated internal waves at the hawaiian ridge is examined using an ensemble of mesoscale background realizations derived from weekly ocean topography experiment topex poseidon altimetric measurements the path of mode 1 is only slightly affected by typical cur

speed and evolution of nonlinear internal waves transiting the south china sea abstract in the south china sea scs 14 nonlinear internal waves are detected as they transit a synchronous array of 10 moorings spanning the waves generation site at luzon strait through the deep basin and onto the upper continental slope 560 km to the west their arrival time speed width energy amplitude and number of trailing waves are monitored waves occur twice daily in a particular pattern where larger narrower a waves alternate with wider smaller b waves waves begin as broad internal tides close to luzon strait s two ridges steepening to o 3 10 km wide in the deep basin and o 200 300 m on the upper slope nearly all waves eventually develop wave trains with larger steeper waves developing them earlier and in greater numbers the b waves in the deep basin begin at a mean speed of 5 greater than the linear mode 1 phase speed for semidiurnal internal waves computed using climatological and in situ stratification the a waves travel 5 10 faster than b waves until they reach

generation and propagation of baroclinic tides modified by the kuroshio in the luzon strait 1 using a three dimensional model with idealized settings this study evaluated the effect of the kuroshio on the generation and propagation of semidiurnal m2 and diurnal k1 baroclinic tides bcts in the luzon strait ls the influences of the varied kuroshio transport the location of the kuroshio and the separation distance of the two meridional ridges were investigated the absence of the kuroshio in the model leads to 30 decreases in the westward baroclinic energy flux fbcx emanating from the west slope of the east ridge compared to the fbcx with the presence of the kuroshio compared to the fbcx without the kuroshio s influence the westward fbcx is increased by 20 40 when the kuroshio is located in either the middle or the west portions of the ls whereas both the westward and eastward fbcx are 25 40 decreased as the kuroshio is moved to the east of the east ridge the wavelength of the mode 1 m2 bct is similar to the separation distance of the two ridges favoring a resonance generation for m2 rather than k1 bcts the increase of the kuroshio transport from 20 to 30 sv 1 sv 106 m3 s 1 enhances the density front but weakens the westward fbcx owing to the effects of energy advection and lateral friction from the kuroshio the influence of the kuroshio on the westward fbcx of k1 is opposite of that on m2 the characteristic slope of k1 is closer to the isopycnal slope across the kuroshio than m2 thereby causing the discrepancy

spatially broad observations of internal waves in the upper ocean at the hawaiian ridge abstract the density and current structure at the hawaiian ridge was observed using seasoar and doppler sonar during a survey extending from oahu to brooks banks across and along ridge changes in internal wave statistics in the upper ocean within 200 km of the ridge are investigated internal waves with trough to crest amplitude as large as 60 m and horizontal wavelength of about 50 km are observed repeatedly in across ridge sections of potential density within 150 km of the ridge kinetic and potential energy density exceed open ocean values with maxima about 10 times garrett munk levels in the kauai channel kc the kinetic energy density is largest along an m2 internal tide ray the ray originates at the northern edge of the ridge peak at a large across ridge change in topographic slope and terminates at the ocean surface about 30 40 km south of the ridge peak kinetic and potential energy density are larger on the south side of the ridge at kc the side with larger topographic slope energy densi

late devensian and holocene relative sea level changes in northwestern scotland new data to test existing models abstract pollen diatom lithostratigraphic and radiocarbon data from five sites in northwestern scotland provide new data from an area previously devoid of reliable and precise information on late devensian and holocene sea level changes the sites cover a range of palaeoenvironments indicative of diversity in coastal evolution since deglaciation for each site and palaeoenvironment the reference water tide level indicative range age and tendency of sea level movement of all sea level index points are quantified to enable correlation of the diverse coastal environments the data record patterns of relative sea level change and tendencies of sea level movement from 12 ka bp to 1 ka bp this is the longest and most comprehensive published record of relative sea level change from the area the information is used to test the accuracy of existing models of relative sea level change the results are only broadly consistent with a quantitative rebound model and there is significant disagreement with empirical models during the late devensian and the early holocene

internal tide radiation from the luzon strait the m2 k1 and o1 internal tides originating in the luzon strait are investigated using the sea surface height measurements by multiple satellites ers 2 envisat topex poseidon jason 1 2 and geosat follow on a plane wave fit method is used to resolve multiple internal tides in arbitrary horizontal directions the luzon strait is an energetic internal tide generation site and radiates internal tides both westward into the south china sea scs and eastward into the western pacific wp in the scs the k1 and o1 internal tides propagate over 1600 km reaching the vietnam coast in the wp they propagate over 2500 km and arrive to the mariana ridge and guam the k1 and o1 internal tides refract toward the equator during propagation the m2 internal tides in the scs bifurcate into two beams the northwestward beam is coincident with the frequent occurrence of internal solitary waves in this region implying their causative relation the phase speeds inferred from the altimetric along beam propagation agree with the theoretical values due to the influence of the earth s rotation the k1 and o1 phase speeds decrease remarkably from high to low latitudes for the diurnal internal tides the eastward radiation is about 50 greater than the westward radiation for m2 the westward radiation is about two times the eastward radiation the altimetric energy fluxes are about 50 of those in numerical model simulations

internal tide generation by seamounts ridges and islands a numerical investigation is made into the generation of semidiurnal internal tides by tidal flow over steep topographic features in the deep ocean a fully three dimensional free surface nonlinear hydrostatic model the princeton ocean model is used with real stratification representative tidal forcing and gaussian shaped seamounts ridges and islands for the topography the efficiencies of the different topographies in extracting energy from the barotropic tide and in generating an internal tide are considered each topography produces an internal tide characterized by signals propagating away from the feature as beams that follow internal wave characteristic paths the strength of the signals however varies markedly for different topographies this is largely attributed to the way in which the barotropic tide interacts with the three dimensional topography internal wave generation requires a significant vertical displacement of stratified water by the barotropic tide as it flows over topography it is found that for symmetric seamounts and islands the barotropic flow tends to go around the feature producing only a weak internal tide when elongated into a ridge barotropic flow is forced across isobaths generating an energetic internal tide changing the horizontal aspect ratio of the topography from 1 1 a seamount to 3 1 a ridge increases the resulting baroclinic energy flux by nearly an order of magnitude the slope of the topography relative to that of the internal wave characteristics is also shown to be important with strongest generation occurring at regions of critical or supercritical topographic slope

a late pleistocene coarse grained spit platform sequence in northern jylland denmark several well preserved late pleistocene spit systems occur uplifted in northern jylland denmark their present day morphological expression allows detailed study of spit growth patterns while the internal sedimentological organisation can be examined in a series of pits distributed along the length of the spits two characteristic vertical sequences are recognized in the systems the first sequence i consists of a giant scale cross bedded foreset unit overlain by topset and beach units while the second sequence ii consists of the foreset unit overlain by bar trough and beach units the two sequence types pass laterally into each other with a short overlap zone they can be interpreted in terms of meistrell s 1966 1972 model for spit platform growth based on scaled wave tank experiments the giant scale cross bedded unit corresponds to prograding of a coarse grained subaqueous spit platform while the topset bar trough and beach units reflect the growth of the subaerial spit the alternation between sequence i and ii reflects the inversely related growth of the spit and platform structures when the rate of subaqueous platform progradation declines the subaerial spit grows uniformly and when the platform progrades uniformly spit growth declines the model is probably only valid for relatively coarse grained systems because only these deposits would have a relatively steep front the water depth in which the spit system progrades and thus bottom topography determines the thickness of the giant scale cross bedded foreset unit because the water depth over the top of the platform is relatively constant if the water is less than a few metres deep the spit platform is not developed as seen where the late pleistocene spit systems prograded over elevations of the sea bottom conversely the correct recognition of spit platform sequences allows precise determination of sea level and water depth at the time of formation finally the model adds one further mode of formation of giant scale cross bedding to those already known from fluvial transverse lateral and point bars subtidal sand waves and gilbert deltas

standing internal tides in the tasman sea observed by gliders abstractlow mode internal tides are generated at tall submarine ridges propagate across the open ocean with little attenuation and reach distant continental slopes a semidiurnal internal tide beam identified in previous altimetric observations and modeling emanates from the macquarie ridge crosses the tasman sea and impinges on the tasmanian slope spatial surveys covering within 150 km of the slope by two autonomous underwater gliders with maximum profile depths of 500 and 1000 m show the steepest slope near 43 s reflects almost all of the incident energy flux to form a standing wave starting from the slope and moving offshore by one wavelength 150 km potential energy density displays an antinode node antinode node structure while kinetic energy density shows the opposite mission mean mode 1 incident and reflected flux magnitudes are distinguished by treating each glider s survey as an internal wave antenna for measuring amplitude wavelength and direction incident fluxes are 1 4 and 2 3 k

holocene land and sea level changes in great britain analysis of more than 1200 radiocarbon dated samples that constrain relative sea levels in great britain over the past 16 000 yr provides estimates of current land level changes negative of relative sea level change maximum relative land uplift occurs in central and western scotland ca 1 6 mm yr 1 and maximum subsidence is in southwest england ca 1 2 mm yr 1 sediment consolidation arising from autocompaction as the sediment accumulates and from land drainage increases the subsidence in areas with thick sequences of holocene sediments with an average effect equivalent to at least an extra ca 0 2 mm yr 1 land subsidence but more in parts of southeast england 0 5 1 1 mm yr 1 modelled changes in tidal range during the mid to late holocene in eastern england suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified the effect is most significant for large coastal lowlands the fenland and humber ca 0 5 and 0 6 mm yr 1 that were tidal embayments during the mid to late holocene

an estimate of tidal energy lost to turbulence at the hawaiian ridge abstract an integrated analysis of turbulence observations from four unique instrument platforms obtained over the hawaiian ridge leads to an assessment of the vertical cross ridge and along ridge structure of turbulence dissipation rate and diffusivity the diffusivity near the seafloor was on average 15 times that in the midwater column at 1000 m depth the diffusivity atop the ridge was 30 times that 10 km off the ridge decreasing to background oceanic values by 60 km a weak factor of 2 spring neap variation in dissipation was observed the observations also suggest a kinematic relationship between the energy in the semidiurnal internal tide e and the depth integrated dissipation d such that d e1 0 5 at sites along the ridge this kinematic relationship is supported by combining a simple knife edge model to estimate internal tide generation with wave wave interaction time scales to estimate dissipation the along ridge kinematic relationship and the observed vertical and cross ridge st

internal tide radiation from mendocino escarpment abstract strong semidiurnal internal tides are observed near mendocino escarpment in full depth profile time series of velocity temperature and salinity velocity and density profiles are combined to estimate the internal tide energy flux divergence of this flux demonstrates that its source is the barotropic tide interacting with the escarpment a baroclinic energy flux of 7 kw m 1 radiates from the escarpment corresponding to 3 of the 220 kw m 1 fluxing poleward in the surface tide energy and energy flux are concentrated in packets that emanate from the flanks of the ridge surmounting the escarpment and one site 90 km north of the escarpment coherent beamlike structure along semidiurnal ray paths remains identifiable until the first surface reflection beyond the first surface reflection north of the escarpment the energy flux drops by 2 kw m 1 and beams are no longer discernible turbulence as inferred from finescale parameterizations is elevated by over two orders of magnitude relative to th