how stationary are the internal tides in a high resolution global ocean circulation model the stationarity of the internal tides generated in a global eddy resolving ocean circulation model forced by realistic atmospheric fluxes and the luni solar gravitational potential is explored the root mean square rms variability in the m2 internal tidal amplitude is approximately 2 mm or less over most of the ocean and exceeds 2 mm in regions with larger internal tidal amplitude the m2 rms variability approaches the mean amplitude in weaker tidal areas such as the tropical pacific and eastern indian ocean but is smaller than the mean amplitude near generation regions approximately 60 of the variance in the complex m2 tidal amplitude is due to amplitude weighted phase variations using the rms tidal amplitude variations normalized by the mean tidal amplitude normalized rms variability nrms as a metric for stationarity low mode m2 internal tides with nrms 0 5 are stationary over 25 of the deep ocean particularly near the generation regions the m2 rms variability tends to increase with increasing mean amplitude however the m2 nrms variability tends to decrease with increasing mean amplitude and regions with strong low mode internal tides are more stationary the internal tide beams radiating away from generation regions become less stationary with distance similar results are obtained for other tidal constituents with the overall stationarity of the constituent decreasing as the energy in the constituent decreases seasonal variations dominate the rms variability in the arabian sea and near equatorial oceans regions of high eddy kinetic energy are regions of higher internal tide nonstationarity

energy levels phase and amplitude modulation of the baroclinic tide off hawaii abstract inverted echo sounder data from station aloha north of oahu hawaii are used to determine the absolute energy levels and time varying nature of the first mode baroclinic tide north of hawaii the semidiurnal tide amplitude and phase are modulated with 60 120 day periodicity which indicates interaction between the baroclinic tide and intra annual mesoscale variability seen off hawaii close to the presumed generation site there is less phase modulation and amplitude modulation is uncorrelated with the far field variability these results are consistent with a model of phase locked generation together with phase and amplitude distortion during propagation the sense of the amplitude modulation is opposite to that previously observed at decadal timescales semidiurnal energy flux at station aloha ranges from 2 2 to 8 0 kw m 1 with a mean value of 4 4 kw m 1

numerical simulation of m2 internal tides in the south brazil bight and their interaction with the brazil current 1 a fully three dimensional nonlinear primitive equation ocean model is applied to study the semidiurnal internal tide in the south brazil bight under summer conditions along the shelf break and upper slope of this region the upper layer 0 600 m is occupied by the southward flowing brazil current several numerical experiments were conducted to investigate the generation and propagation of the m2 internal tide using horizontally homogeneous and vertically stratified density fields internal tides were generated over the whole bight with a clear signal on the continental shelf when a more realistic summer stratification was considered a baroclinic jet representative of the brazil current developed and comparisons between current observations and modeled results were improved this jet acts as a barrier to the coastward propagation of the internal tide generated over the slope reflecting it back towards the open ocean on the negative relative vorticity side of the brazil current located over the shelf internal tides are trapped enhancing vertical current variability and hence tidally induced mixing the results highlight the importance of considering background flows when investigating internal tides in regions of strong along slope baroclinic flows such as western boundary currents

2000 year environmental history of a karstic lake in the mediterranean pre pyrenees the estanya lakes spain abstract the sediment record of the estanya lakes pre pyrenees spain indicates that this region was intensely affected by land use during the middle and modern ages which contrasts with the present day poor socioeconomic development of the region the correlation between sediment and biotic data and well known historical events suggests a reliable history of environmental changes in this area during the last 2000 years changes in lake level were mainly controlled by climatic factors whereas properties such as lithology organic carbon ostracods and pollen content are mainly associated with lake management and land use major sedimentological changes resulted from the use of the lake for hemp retting at the start of the xivth century subsequent depopulation of the area in the xxth century led to the progressive recovery of the lacustrine ecosystem

energetics of m2 barotropic to baroclinic tidal conversion at the hawaiian islands abstract a high resolution primitive equation model simulation is used to form an energy budget for the principal semidiurnal tide m2 over a region of the hawaiian ridge from niihau to maui this region includes the kaena ridge one of the three main internal tide generation sites along the hawaiian ridge and the main study site of the hawaii ocean mixing experiment the 0 01 horizontal resolution simulation has a high level of skill when compared to satellite and in situ sea level observations moored adcp currents and notably reasonable agreement with microstructure data barotropic and baroclinic energy equations are derived from the model s sigma coordinate governing equations and are evaluated from the model simulation to form an energy budget the m2 barotropic tide loses 2 7 gw of energy over the study region of this 163 mw 6 is dissipated by bottom friction and 2 3 gw 85 is converted into internal tides internal tide generation primarily occurs along the flanks of the kaena ridge and

characterisation and engineering properties of tiller clay abstract a detailed characterisation of the quick clay underlying the ntnu research site at tiller trondheim is presented the objective of the work is to provide guidance on quick clay parameters to engineers and researchers working with similar clays in scandinavia and north america especially on landslide hazard assessment the material is lightly overconsolidated and is characterised by its high degree of structure and very high sensitivity quick clay clay and water contents are both about 40 the plasticity index is low 5 this relates to the low active minerals of the clay and silt fractions illite chlorite and quartz feldspars respectively undrained shear strength is of the order of 30 kpa to 50 kpa medium stiff and increases with depth the deposit is consistent across the site and its properties are similar to other norwegian quick clays significant efforts have been made into examining sample disturbance effects on the material it was found that thin walled steel fixed piston samples can yield results similar to those of block samples provided the work is carried out with extreme care and storage time is minimised the piezocone cptu test proved very useful in characterising the material

interactions between a submesoscale anticyclonic vortex and a front abstract the evolution of a submesoscale anticyclonic vortex was observed by high frequency doppler radio current meters and satellite radiometers the vortex formed between two large cyclones to the southwest of oahu hawaii the radius of the core was 15 km the azimuthal velocity reached 35 cm s 1 and the surface vorticity remained below f for 9 days reaching an extremum of 1 7f the flow was ageostrophic near the center and around the periphery of the vortex the initial growth may have been driven by negative wind stress curl in the lee of oahu the vortex was prone to inertial symmetric and anticyclonic ageostrophic instabilities but the temporal evolution of radial profiles of vorticity was inconsistent with angular momentum redistribution by inertial instability a tongue of surface water 0 7 c warmer became entrained northward between the vortex and the colder cyclone to the west as the vortex strengthened a 0 14 c km 1 front formed along the eastern flank of the tongue the sea surface

internal tide spectroscopy and prediction in the timor sea abstractspectral analyses of two 3 5 yr mooring records from the timor sea quantified the coherence of mode 0 surface and mode 1 internal tides with the astronomical tidal potential the noncoherent tides had well defined variance and were most accurately quantified for tidal species as opposed to constituents in long records 6 months on the continental slope 465 m the semidiurnal mode 0 and mode 1 velocity and mode 1 pressure variance were 95 68 and 56 coherent respectively on the continental shelf 145 m the semidiurnal mode 0 and mode 1 velocity and mode 1 pressure variance were 98 34 and 42 coherent respectively the response method produced time series of the semidiurnal coherent and noncoherent tides the spectra and decorrelation time scales of the semidiurnal tidal amplitudes were similar to those of the barotropic mean flow and mode 1 eigenspeed 4 days suggesting local mesoscale variability shapes noncoherent tidal variability over long time scales 30 days mod

diagnosis of vertical velocities in the upper ocean from high resolution sea surface height 1 a surface quasi geostrophy based esqg method to diagnose the vertical velocity field from sea surface height ssh is assessed using high resolution simulations these simulations concern a turbulent eddy field with large rossby numbers and energetic wind driven motions results indicate that low frequency vertical velocities and also horizontal motions can be reconstructed within a range of scales between 20 km and 400 km from the surface down to 500 m the only information needed is a single high resolution ssh snapshot and information on the large scale vertical stratification inertial motions are naturally filtered because they do not contaminate ssh as we demonstrate these results are encouraging and further strengthen previous studies using the esqg method they indicate that access to high resolution ssh may represent a major advance to retrieve horizontal and vertical fluxes of any tracer in the upper ocean

review of long seabed samplers and criteria for new sampler design a cost efficient way of investigating shallow sediments and for collecting soils data for many offshore geotechnical problems e g anchoring of floating structures with suction piles or evaluation of submarine slope stability is to carry out seabed sampling to say 25 m below seabed and in addition perform seabed cptus to say 40 m based on a review of data collated from the literature and from in house project experience at the norwegian geotechnical institute it was found that kullenberg type piston core samples give poor recovery and samples which are increasingly disturbed as penetration increase this means that laboratory tests on these samples will give results that are not representative of in situ conditions and will give incorrect parameters for foundation design many different factors control the quality of the samples recovered but the need for an effectively stationary piston a core retainer and improvements to the physical sampler parameters e g diameter wall thickness ratio cutting edge angle inside and outside friction are perhaps the most critical the importance of each of these factors is discussed in detail in addition to the need for instrumentation and the way to penetrate the sampler recommendations are given in terms of criteria for the design of a new sampler which the authors feel will give better results than most samplers used in practice today

internal tide generation at the continental shelf modeled using a modal decomposition two dimensional results abstract stratified flow over topography is studied with oceanic applications in mind a model is developed for a fluid with arbitrary vertical stratification and a free surface flowing over three dimensional topography of arbitrary size and steepness with background rotation in the linear hydrostatic regime the model uses an expansion of the flow fields in terms of a set of basis functions which efficiently capture the vertical dependence of the flow the horizontal structure may then be found by solving a set of coupled partial differential equations in two horizontal directions and time subject to simple boundary conditions in some cases these equations may be solved analytically but in general simple numerical procedures are required using this formulation the internal tide generated by a time periodic barotropic tidal flow over a continental shelf and slope is calculated in various idealized configurations the topography and fluid motion are taken to be independent of one coordinate di

reconstructing the ocean interior from high resolution sea surface information abstractwhen evaluated against the 1 30 resolution submesoscale resolving ofes model outputs the previously published interior surface quasigeostrophic method from the 2013 study by wang et

subthermocline eddies observed by rapid sampling argo floats in the subtropical northwestern pacific ocean in spring 2014 in spring 2014 two subthermocline eddies stes were observed by rapid sampling argo floats in the subtropical northwestern pacific stnwp the first one is a warm salty and oxygen poor lens with its temperature salinity dissolved oxygen t s do anomalies reaching 1 16 c 0 21 practical salinity unit psu 29 9 mol kg respectively near the 26 62 0 surface the other is a cold fresh and oxygen rich lens with its t s do anomalies reaching 1 95 c 0 34 psu 88 0 mol kg respectively near the 26 54 0 surface the vertical extent of the water mass anomalies in the warm cold ste is about 190 m 150 m and its horizontal length scale is 22 7 km 18 10 km according to their water mass properties we speculate that the warm and cold stes are generated in the north pacific subtropical and subarctic front region respectively the observed stes may play an important role in modifying the intermediate layer water properties in the stnwp and this needs to be confirmed by more focused observations in the future

wind ringing of the ocean in presence of mesoscale eddies 1 recent findings have highlighted the impact of high frequency hf winds on the inertial motions and the consequences on the large scale oceanic circulation wunsch and ferrari 2004 within this context the present study focuses on the role of intermediate scales related to oceanic mesoscale eddies results show that a turbulent eddy field does not affect the impact of hf winds on the inertial motions however the eddies efficiently and permanently concentrate the wind forced inertial motions in small scale anticyclonic structures this leads to a spatially heterogeneous vertical mixing strongly related to the eddy field properties

structure of the baroclinic tide generated at kaena ridge hawaii repeat transects of full depth density and velocity are used to quantify generation and radiation of the semidiurnal internal tide from kaena ridge hawaii a 20 km long transect was sampled every 3 h using expendable current profilers and the absolute velocity profiler phase and amplitude of the baroclinic velocity pressure and vertical displacement were computed as was the energy flux large barotropically induced isopycnal heaving and strong baroclinic energy flux divergence are observed on the steep flanks of the ridge where upward and downward beams radiate off ridge directly above kaena ridge strong kinetic energy density and weak net energy flux are argued to be a horizontally standing wave the phasing of velocity and vertical displacements is consistent with this interpretation results compare favorably with the merrifield and holloway model

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

stress history and sampling disturbance effects on monotonic and cyclic responses of overconsolidated bootlegger cove clays this paper examines the influence of reproducing the stress history of a natural soil deposit during laboratory reconsolidation on the subsequent response and behavior of heavily overconsolidated b

temporal variability of internal tides in the northeast south china sea 1 the northeast south china sea is perhaps the largest internal tide energy source in the world the temporal variability of internal tides was investigated on the basis of 8 month moored acoustic doppler current profiler observations on the continental slope at the dongsha plateau the daily amplitude and phase of diurnal and semidiurnal internal tides were determined from complex demodulation and the dominant spatial and temporal patterns were extracted with empirical orthogonal function eof analysis the eof modal structures showed good agreement with the normal mode solution although vertical phase propagations were apparent the first semidiurnal eof mode corresponded to the first normal mode and the first two diurnal eof modes corresponded to the second and third normal modes respectively the modal structure and energy flux also were consistent with previous observations near the shelf break from the asian seas international acoustic experiment on the other hand the amplitudes of diurnal and semidiurnal eof modes both indicated large irregular fortnightly variations that were not phase locked incoherent with astronomical forcing the study highlighted the importance of incoherent internal tidal motion which accounted for about three fourths of the observed tidal energy

role of mesoscale eddies in modulating the semidiurnal internal tide observation results in the northern south china sea abstractthe role of mesoscale eddies in modulating the semidiurnal internal tide sit in the northern south china sea scs is examined using the data from a cross shaped mooring array from novem

observations of vortex rossby waves associated with a mesoscale cyclone abstract short wavelength l 100 km rossby waves with an eastward zonal phase velocity were observed by high frequency radio doppler current meters and moored adcps west of oahu hawaii during spring 2003 they had rossby numbers ro f o 1 periods of 12 15 days and phase speeds of 8 9 cm s 1 and they were surface trapped with vertical e folding scales of 30 170 m they transferred horizontal kinetic energy to the background flow of a mesoscale cyclone lying 160 190 km west of oahu revealed by altimetry the waves approximately satisfied the dispersion relation of vortex rossby waves propagating through the radial gradient of potential vorticity associated with the cyclone vertical shear of the background currents may also affect wave propagation theoretical studies have shown that vortex rossby waves provide a mechanism by which perturbed vortices axisymmetrize and strengthen and may be important to the dynamics of oceanic vortices

can oceanic submesoscale processes be observed with satellite altimetry high resolution 2 km and hourly observations of surface currents from high frequency radars are analyzed in terms of sea level anomalies sla and compared with data from two satellite altimeter ground tracks purpose is to investigate whether ocean submesoscale processes can be observed with satellite altimetry our results highlight two major problems that must be overcome before being able to resolve submesoscale processes with altimetry i signal contamination from high frequency motions and in particular from incoherent internal tides near inertial oscillations have no effect on sla and ii measurement noise which prevents the computation of accurate cross track currents on scales o 10 km the latter may be overcome by future satellite altimeter missions but the former will require taking into account the effect of mesoscale variability on internal tide propagation in regions where internal tides are significant citation chavanne c p and p klein 2010 can oceanic submesoscale processes be observed with satellite altimetry geophys res lett 37 l22602 doi 10 1029 2010gl045057

surface manifestation of internal tides generated near hawaii analysis of topex poseidon satellite altimetry reveals short wavelength fluctuations in the ocean surface tide that are attributable to internal tides a significant fraction of the semidiurnal internal tide generated at the hawaiian ridge is evidently phase locked to the astronomical potential and can modulate the amplitude of the surface tide by 5 cm the internal tide is thus easily mapped along satellite groundtracks and it is found to be spatially coherent over great distances with waves propagating well over 1000 km from the hawaiian ridge before decaying below noise level both first and second baroclinic modes are observed in both the m 2 lunar and s 2 solar tides the high space time coherence is in sharp contrast to what is often inferred from current meter observations but it confirms recent speculations from an acoustic experiment north of hawaii

evaluation of disturbance induced on soft offshore sediments by two types of gravity piston coring techniques abstract sample disturbance is still a key issue in offshore investigations especially when logistic and financial limitations do not allow the use of drilling equipment this paper focuses on the comparison between the disturbance induced by a conventional free fall piston corer ff and a modified piston corer ad equipped with a velocity control angel descent method twin core samples were retrieved in two successions of pelitic sediments with a prevailing non clayey fraction and a non negligible sandy fraction comparison was based on different acquisition physical and mechanical parameters ranging from accelerometer data to magnetic susceptibility logs and geotechnical parameters from laboratory investigations including oedometer compression tests and cyclic simple shear tests accelerometer data highlighted the sharp reduction in velocity obtained for ad samples magnetic susceptibility logs characterized by a pattern of peaks induced by several volcaniclastic levels present in the succession indicated that the ad method significantly reduces core shortening among geotechnical investigations cyclic shear tests provided small strain shear moduli always higher in ad samples whilst the response of oedometer compression tests was equivocal in fact methods for assessing sample disturbance have demonstrated to bear limited effectiveness when applied to soils with relatively low clay content and significant overconsolidation as it is the case of the studied sediments

characterization of soils beneath a posidonia oceanica meadow the study of a 475 cm core spanning 4316 y bp sampled in a posidonia oceanica meadow portlligat bay nw mediterranean allowed us to make the first detailed description of the soil below this endemic seagrass the sediments under p oceanica often referred to as mat or matte are low density average bulk density of 0 69 g dw cm 3 marine soils mainly composed of siliciclastic 46 and biogenic carbonated 46 fine grained sediments particles 1 mm and finer organic matter 3 of som 1 mm the mat is heterogeneous and has a high total organic matter tom content in the upper layers average of 32 in the top 50 cm after ca 500 years of burial after which the layers become increasingly dominated by inorganic fractions ranging from 20 to 1 of tom in 50 475 cm the tom content in the mat decreases exponentially at an overall rate of 0 0005 y 1 p oceanica sediments have been found to contain the highest areal stocks of tom and organic c 194 kg dw tom m 2 and 79 kg corg m 2 respectively out of all seagrasses the average corg refractory burial rates were estimated to be 21 g corg m 2 y 1 carbon as carbonates accreted at a rate of 54 g ccarb m 2 y 1 for the mat thickness studied the two c fractions yielded a total stock that is among the highest ever recorded in terrestrial and marine soils 282 kg ctot m 2 the mat was also found to trap large amounts of sediment rate 899 g dw m 2 y 1 stock 3342 kg dw m 2 and in particular muddy silt and clay fractions rate 120 g dw m 2 y 1 stock 417 kg dw m 2 the results obtained in this study provide sound additional proof of the valuable role p oceanica plays in stabilizing coastal sediments and sequestering c and also of its potential as a holocene palaeorecord the p oceanica mats located at shallow depths 2 m can be tentatively classified as a limnic subaquatic histosols calcaric eutric world reference base for soil resources 2007

the surface expression of semidiurnal internal tides near a strong source at hawaii part i observations and numerical predictions abstract observations of semidiurnal currents from high frequency radio doppler current meters and moored acoustic doppler current profilers adcps in the kauai channel hawaii are described and compared with two primitive equation numerical models of the tides the kauai channel separating the islands of oahu and kauai is a site of strong internal tide generation by the barotropic tides flowing over kaena ridge the subsurface extension of oahu the nature and impacts of internal tide generation in the kauai channel were intensively studied during the 2002 03 near field component of the hawaii ocean mixing experiment comparisons of observed coherent i e phase locked to the astronomical forcing m2 and s2 surface currents with model predictions show good agreement for the phases indicating propagation of internal tides away from the ridge although the predicted m2 and s2 surface currents are similar except for their magnitudes as expected for internal waves at periods closer to each other 12

tides of the northwestern ross sea and their impact on dense outflows of antarctic bottom water abstract moored and depth profile measurements of hydrography and currents during the 2003 2005 antarctic slope anslope program on the shelf slope region near drygalski trough sill in the northwest ross sea have revealed an energetic benthic outflow of cold dense antarctic bottom water aabw produced near the shelf break this outflow couples dense water production processes on the continental shelf to ventilation of the global deep ocean we use time series of bottom pressure and currents on the anslope moorings and a high resolution three dimensional primitive equation numerical model to explore the hypothesis that the tidal currents near the shelf break have a significant impact on outflow volume transport and hydrographic properties tidal currents exceed 1 m s 1 at spring tide over the outer shelf and upper slope tidal advection at spring tide carries water parcels 20 km across slope during a half tidal cycle sufficient to advect water from northern drygalski trough across the sill to the shelf break or similarly from the shelf break 500 m water depth down to the 1600 m isobath a tidally rectified lagrangian mean flow of order 0 05 0 1 m s 1 over the outer shelf and upper slope accompanies the spring tide thickness and water mass properties of the benthic layer over the sill and upper slope exhibit pronounced tidal cycles due to advection of hydrographic gradients and to energetic mixing that can extend more than halfway up from the seabed to the ocean surface maximum parameterized diapycnal diffusivity in the benthic layer at spring tides approaches 1 m 2 s 1 the addition of tides has a profound effect on time averaged outflows of aabw primarily through an increase in benthic layer thickness during spring tide downslope volume fluxes of aabw over the slope averaged over a tidal cycle are 2 5 times larger at spring tide than at neap indicating a need to include the effect of tides in large scale ocean models attempting to represent shelf water contributions to the global ocean circulation

internal tidal currents and solitons in the southern bay of bengal abstract tidal currents and higher frequency internal solitons are observed from current and hydrographic fields that were recently measured at six deep water moorings in the southern bay of bengal by the naval research laboratory current temperature and salinity were measured in the upper 500 m of the water column between december 2013 and august 2015 harmonically fitted coherent tidal currents in the upper 500 m showed maximum amplitudes for the m2 constituent with velocities of the order of 3 cm s 1 m2 tidal ellipses were generally oriented towards the north northeast incoherent internal tides accounted for at least 60 of the total semidiurnal tide energy solitons were generated at multiple source regions along the andaman islands and contribute significantly to the high frequency energy greater than 1 cph solitons were present throughout the measurement period but their activity was reduced during the 2014 2015 winter monsoon soliton and internal tide amplitudes show a fortnightly modulation consistent with the spring neap cycle of the semidiurnal tide the interaction of tides and the associated high frequency waves 20 40 min periods with mesoscale eddies produced regions of enhanced shear and strain in the thermocline high strain regions were found within cyclonic eddies and high shear regions were found within anticyclonic eddies shear strain based dissipation models indicate that mixing rates can be enhanced by a factor of 3 5 by tidal and higher frequencies during interactions with eddies this study further suggests that tidal harmonics and internal tides have an important impact on the near surface currents away from coastal boundaries in the interior of the bay of bengal while the effects of the depth averaged tides are more important deeper in the water column

submesoscale eddy vertical covariances and dynamical constraints from high resolution numerical simulations abstractwe analyze high resolution 1 km simulations of the western pacific gulf of mexico and arabian sea to understand submesoscale eddy dynamics a mask based on the okubo weiss parameter iso

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

non stationary internal tides observed with satellite altimetry 1 temporal variability of the internal tide is inferred from a 17 year combined record of topex poseidon and jason satellite altimeters a global sampling of along track sea surface height wavenumber spectra finds that non stationary variance is generally 25 or less of the average variance at wavenumbers characteristic of mode 1 tidal internal waves with some exceptions the non stationary variance does not exceed 0 25 cm2 the mode 2 signal where detectable contains a larger fraction of non stationary variance typically 50 or more temporal subsetting of the data reveals interannual variability barely significant compared with tidal estimation error from 3 year records comparison of summer vs winter conditions shows only one region of noteworthy seasonal changes the northern south china sea implications for the anticipated swot altimeter mission are briefly discussed

focusing of internal tides by near inertial waves the refraction of internal waves by lower frequency near inertial waves has been predicted theoretically but never observed before here we report observations of semi diurnal internal tides generated by the rough topography of the central indian ridge in the presence of a strong lower frequency near inertial wave field generated by a tropical storm the semi diurnal internal tide energy is trapped within upward propagating bands with a periodicity close to the inertial period a ray tracing model suggests that this trapping results from the internal tide refraction by the shear associated with near inertial waves this yields a strong increase of the internal tide energy and shear in space time regions where the background flow focuses the rays leading to the formation of caustics this mechanism may increase vertical mixing generated by baroclinic tides in the vicinity of mid ocean ridges in tropical regions

mesoscale to submesoscale transition in the california current system part i flow structure eddy flux and observational tests in computational simulations of an idealized subtropical eastern boundary upwelling current system similar to the california current a submesoscale transition occurs in the eddy variability as the horizontal grid scale is reduced to o 1 km this first paper in a series of three describes the transition in terms of the emergent flow structure and the associated time averaged eddy fluxes in addition to the mesoscale eddies that arise from a primary instability of the alongshore wind driven currents significant energy is transferred into submesoscale fronts and vortices in the upper ocean the submesoscale arises through surface frontogenesis growing off upwelled cold filaments that are pulled offshore and strained in between the mesoscale eddy centers in turn some submesoscale fronts become unstable and develop submesoscale meanders and fragment into roll up vortices associated with this phenomenon are a large vertical vorticity and rossby number a large vertical velocity relatively flat horizontal spectra contrary to the prevailing view of mesoscale dynamics a large vertical buoyancy flux acting to restratify the upper ocean a submesoscale energy conversion from potential to kinetic a significant spatial and temporal intermittency in the upper ocean and material exchanges between the surface boundary layer and pycnocline comparison with available observations indicates that submesoscale fronts and instabilities occur widely in the upper ocean with characteristics similar to the simulations

evaluating the use of high frequency radar coastal currents to correct satellite altimetry 1 coastal altimeter waveforms may differ from the ones in the open ocean either from rapid changes in the sea state or the presence of land within the satellite altimeter footprint the optimal retracking method for an individual track may turn out to be a combination of several retrackers and may depend on the sea state the coastal high frequency radar hfr ocean surface currents hourly interpolated with a resolution up to 2 km and an offshore range up to 150 km are evaluated to validate the altimeter sea surface height ssh measurements a method to derive hfr ssh mapped with a varying spatial scale optimal interpolation from the hfr velocities has been implemented evaluated mainly in the regions farther than 25 km off the u s west coast the hfr ssh shows good agreement with jason 1 2 altimetry products over the years 2008 and 2009 three jason 2 pistach retrackers and one generic open ocean retracker have been analyzed using the traditional 1 hz sampling rate nearshore an experimental reprocessing of the 20 hz range measurements is also tested to check for a gain in along track spatial resolution referencing to the hfr ssh indicate the need to have several retrackers available even over the continental shelf with ice3 fitting better during bloom events and mle 4 or red3 for high sea states these studies demonstrate the value of hfr as a potential tool to correct coastal altimeter ssh refine their spatial resolution and provide some insight into the altimeter behavior as a function of ocean conditions

a 2000 year geomagnetic field record from the gulf of papua abstract a high resolution holocene record of geomagnetic field direction and intensity in the gulf of papua was constructed using paleomagnetic data from eight piston cores collected in the region the chronology of the cores was based largely on radiocarbon dates from benthic foraminifera correlation of seismic reflectors imaged in subbottom data between nearby cores was consistent with the chronostratigraphic framework based on radiocarbon dates and provided additional confidence of the age model in other regions where cores sampled different depositional settings associated with the three dimensional prograding lobes reflectors could not be confidently correlated between cores furthermore radiocarbon ages from the bottoms of trigger cores and tops of co located piston cores revealed varying amounts of overpenetration of the piston core below the seafloor the relative paleointensity and a general eastward trend in the declination and steepening of the inclination in our new record are generally compatible with the closest 4300 km existing records our record does not agree well with global field models cals3k and pfm9k likely reflecting the lack of existing data contributing to field models in the region

palaeoecological potential of the marine organic deposits of posidonia oceanica a case study in the ne iberian peninsula article i nfo a high resolution sedimentary sequence sampled from the portlligat bay ne iberian peninsula has been studied in order to assess its palaeoecological potential this sedimentary sequence is considered a very particular one as it is a peat like deposit derived from the accumulation of the belowground dead parts of the marine phanerogam posidonia oceanica through the last 1600 years this study represents the first attempt to explore the palaeoecological potential of such deposits from a palynological point of view and has allowed the reconstruction of the vegetation dynamics and changes human impact and the palaeoclimatic characteristics demonstrating the value of these sedimentary records in palaeopalynological studies

ssh wavenumber spectra in the north pacific from a high resolution realistic simulation abstractfollowing recent studies based on altimetric data this paper analyses the spectral characteristics of the sea surface height ssh using a new realistic simulation of the north pacific ocean with high resolution in the horizontal and 100 vertical levels this simulation resolves smaller scales down to 10 km than altimetric data limited to 70 km because of the noise level in high eddy kinetic energy eke regions as in the western part ssh spectral slope almost follows a k 4 with k the wavenumber or slightly steeper law in agreement with altimeter studies the new result is that unlike altimeter studies such a k 4 slope is also observed in low eke regions as in the eastern part in these regions this slope mostly concerns scales not well resolved by altimetric data such k 4 ssh spectral slopes are weaker from what is expected from quasigeostrophic turbulence theory but closer to surface quasigeostrophic sqg turbulence theory the consequence is that the small scales concerned

the holocene climatic optimum and pollen records of sapropel 1 in the eastern mediterranean 9000 6000 bp abstract the most recent sapropel in the deep eastern mediterranean sea has been deposited between 9 and 6 ka bp climate conditions as revealed by the pollen records of this sapropel in marine cores were most favorable for temperate deciduous trees which is in agreement with the inferences from records of peripheral land pollen sites the abundance of deciduous oak pollen is much higher than that of artemisia sage brush indicating that annual precipitation in the mid elevation borderlands was at least 550 mm without summer drought but more probably in the range 800 1300 mm the pollen of pistacia which formed a savanna at low elevations is also at its highest abundance and signals the absence of frost in winter while being capable of withstanding summer drought the early holocene therefore appears as the post glacial climatic optimum with the highest moisture and mildest winters in southwest asia this is also the time of the neolithic population explosion with incipient domestication of cereals possibly following natural selection of the tough rachis mutation in wheat and barley by the extreme aridity of the preceding younger dryas

revealing climatic variability of the last three millennia in northwestern iberia using pollen influx data climatic variability of the last 3 millennia in nw iberia has been documented using high resolution pollen analysis of vir 18 core retrieved from the ria de vigo 42degrees14 07 n 8degrees47 37 w the depth age model is based on two accelerator mass spectrometry c 14 dates and three historically dated botanical events in galicia the expansion of juglans and pinus as well as the introduction of eucalyptus during the last 3000 years the relative pollen record demonstrates the occurrence of an open deciduous oak forest indicating a humid and temperate climate in northwestern iberia two step forest reduction since 975 cal bc suggests climate as the main cause rather than major socio economic changes documented in historical archives absolute pollen influx has been compared with instrumental summer and winter temperatures and tentatively used as a proxy of short decadal scale and low amplitude similar to 1degreesc temperature variations this new approach allows us to detect for the first time in nw iberia the millennial scale climatic cyclicity suggested by north atlantic records challenging the apparent climatic stability reflected by the relative pollen record the little ice age is recorded as low pollen influx values between 1400 and 1860 cal ad with a cold maximum at 1700 cal ad maunder minimum the roman and medieval warm periods are detected through high pollen influx values at 250 cal bc 450 cal ad and 950 1400 cal ad respectively c 2003 elsevier science b v all rights reserved

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

subtropical catastrophe significant loss of low mode tidal energy at 28 9 1 an idealized numerical study of a northward propagating internal tide reveals a dramatic loss of energy to small scale subharmonic instabilities near 28 9 n inspired by observations of the internal tide radiating northward from the hawaiian ridge a three dimensional numerical model is initialized with a northward baroclinic tidal flux of approximately 1 7 kw m after an initial spinup period energy is quickly transferred from the baroclinic tide to subharmonic motions with half the horizontal tidal wavenumber and small vertical scales through nonlinear advection of horizontal tidal velocity gradients potential oceanic implications are twofold first once a steady state has been reached the instability acts as a partial filter of northward tidal flux between 27 5 and 29 5 n in rough agreement with some altimetric tidal observations second elevated shear of the subharmonic motions suggests the potential for elevated near surface dissipation rates near the critical latitude that may be important for upper ocean mixing

exploring the synergy between along track altimetry and tracer fronts to reconstruct surface ocean currents abstract high frequency along track altimetric data only provide direct information on the geostrophic currents orthogonal to the track a new approach is proposed that combines these across track current estimates with directional information from remotely sensed tracer fields such as surface chlorophyll concentration and sea surface temperature the analysis focuses on the south madagascar region characterised by the strong east madagascar current and sharp gradients of surface tracers the results are compared with in situ observations from three moorings along the jason 1 track 196 accurate information on the total velocity direction is the key factor for obtaining accurate estimates of along track velocities surface tracer fronts can be successfully used to retrieve such information especially when currents intersect the satellite track at low incidence angles within 60 from the perpendicular direction errors in the reconstructed total velocities tend to grow rapidly for higher angles best performance is obtained by retaining information from the strongest fronts only however this significantly limits the resolution at which total currents can be reconstructed along the altimeter track

analysis and modelling of gravity and piston coring based on soil mechanics the effects of gravity and piston corers on the dimensional accuracy of marine sediment cores is analysed using principles of soil mechanics a model for the coring process is built around the feedback that arises and develops between the core barrel and the sampled sediment this model for sediment response is applied to different hypothetical coring scenarios which are then compared to real examples providing insights into the specific effects of each sampling method and the development of these effects down core four cores from a single location on the iberian margin are found to contain stratigraphically intact successions that differ in length by a factor of up to 2 7 due solely to the different effects of each coring method these dimensional discrepancies are attributed to the combined effects of over sampling in the upper portions of the piston cores due to cable rebound causing upward piston acceleration and under sampling dominant in the basal portions of the open barrel gravity type cores it is suggested that heavier piston corers deployed on longer lighter cables are prone to greater over sampling ratios over longer stratigraphic intervals due to the increased likelihood and extent of cable rebound cable rebound may also give rise to double penetration of gravity corers resulting in repeated stratigraphic intervals knowledge of the dimensional accuracy of marine sediment cores is essential to an evaluation of past sedimentation rates and hence interpretations of past depositional processes it is therefore essential that we recognise the sampling effects of each coring method and their variability down core lest coring artefacts be interpreted as sedimentary signals different core types may be more suited to different palaeoceanographic investigations hence failing the development of a practical cable deployed recoilless piston corer a combination of a variety of core types will permit the best acquisition of the in situ stratigraphic truth our results suggest that a large diameter dc 20 30 cm square barrel gravity corer for the top 10 12 m combined with a cylindrical piston corer below 10 m may provide the least deformed material

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

some expectations for submesoscale sea surface height variance spectra abstractin anticipation of the surface water and ocean topography swot wide swath altimetry mission this study reviews expectations for sea surface height ssh variance spectra at wavelengths o

reconstruction of ocean s interior from observed sea surface information observational surface data are used to reconstruct the ocean s interior through the interior surface quasigeostrophic isqg method the input data include the satellite derived sea surface height satellite derived sea surface temperature satellite derived or argo based sea surface salinity and an estimated stratification of the region the results show that the isqg retrieval of subsurface density anomalies is quite promising compared to argo profile data at 1000 m depth the directions of retrieved velocity anomalies are comparable to those derived from argo float trajectories the reconstruction using surface density input field approximated only by sst with constant sss performs less satisfactorily than that taking into account the contribution of sss perturbations suggesting that the observed sss information is important for the application of the isqg method better reconstruction is obtained in the warm season than in the cold season which is probably due to the stronger stratification in the warm season that confines the influence of the biases in the surface input data especially sss in a shallow layer the comparison between the performance of isqg with argo based sss input and that with satellite derived sss input suggests that the biases in the sss products could be a major factor that influences the isqg performance with reduced biases in satellite derived sss in the future the measurement based isqg method is expected to achieve better reconstruction of ocean interior and thus is promising in practical application

geological geotechnical characterisation of sarapui ii clay abstract the paper presents the geological geotechnical characterisation of the very soft organic plastic slightly overconsolidated sarapui ii clay dissipation tests showed no artesian pressure in the deposit the organic content is in the range 5 18 the higher values to 3 m depth nacl content increases almost linearly with depth from 7 g l at 1 m depth to 24 26 g l at 6 m depth kaolinite is predominant throughout the profile increasing almost linearly with depth however smectite has almost the same percentage until 3 5 m depth the plasticity index varies in the range 60 170 and may be directly related to the clay minerals g o values decrease with depth from 14 28 mpa to 1 mpa at 3 m depth then increase with depth reaching 5 mpa at the bottom of the very soft material vane test results indicated two regions of s u versus depth the first from 1 m to 5 m depth with s u in the range 8 12 kpa the second from 6 m to 8 m depth with s u in the range 16 18 kpa there is a trend of linear increase in sensitivity with depth from 4 5 at 1 m depth to 7 9 at 7 m depth salt content does not seem to play a major role in the sensitivity of sarapui ii clay

internal tides in the southwestern japan east sea abstract this paper investigates the internal tidal energy distribution in the southwestern japan east sea using vertical round trip travel time data from 23 pressure sensor equipped inverted echo sounders pies the records are analyzed by bandpass filtering to separate time dependent variability of the semidiurnal and diurnal bands the semidiurnal internal tides exhibit a horizontal beam pattern of high energy propagating into the open basin they originate from a restricted portion of the shelf break where the korea strait enters the ulleung basin the generation appears to occur at 200 m water depth near 35 5 35 7 n and 130 131 e where the slope of bottom topography matches that of the wave characteristics coinciding with the location where the semidiurnal barotropic cross slope tidal currents are strongest maximum vertical displacement of the thermocline interpreted as a long wave first baroclinic mode from the measured is about 25 m near the generation region annual and monthly var

mesoscale eddy internal wave coupling part i symmetry wave capture and results from the mid ocean dynamics experiment abstract vertical profiles of horizontal velocity obtained during the mid ocean dynamics experiment mode provided the first published estimates of the high vertical wavenumber structure of horizontal velocity the data were interpreted as being representative of the background internal wave field and thus despite some evidence of excess downward energy propagation associated with coherent near inertial features that was interpreted in terms of atmospheric generation these data provided the basis for a revision to the garrett and munk spectral model these data are reinterpreted through the lens of 30 years of research rather than representing the background wave field atmospheric generation or even near inertial wave trapping the coherent high wavenumber features are characteristic of internal wave capture in a mesoscale strain field wave capture represents a generalization of critical layer events for flows lacking the spatial symmetry inherent in a parallel shear flow or isolated vortex

the surface expression of semidiurnal internal tides near a strong source at hawaii part ii interactions with mesoscale currents abstract observations of semidiurnal surface currents in the kauai channel hawaii are interpreted in the light of the interaction of internal tides with energetic surface intensified mesoscale currents the impacts on internal tide propagation of a cyclone of 55 km diameter and 100 m vertical decay scale as well as of vorticity waves of 100 km wavelength and 100 200 m vertical decay scales are investigated using 3d ray tracing the doppler shifted intrinsic frequency is assumed to satisfy the classic hydrostatic internal wave dispersion relation using the local buoyancy frequency associated with the background currents through thermal wind or gradient wind balance the m2 internal tide rays with initial horizontal wavelength of 50 km and vertical wavelength of o 1000 m are propagated from possible generation locations at critical topographic slopes through idealized mesoscale currents approximating the observed currents despite the lack of scale separation between the internal waves and backgroun

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

dynamics of the upper oceanic layers in terms of surface quasigeostrophy theory in this study the relation between the interior and the surface dynamics for nonlinear baroclinically unstable flows is examined using the concepts of potential vorticity first it is demonstrated that baroclinic unstable flows present the property that the potential vorticity mesoscale and submesoscale anomalies in the ocean interior are strongly correlated to the surface density anomalies then using the invertibility of potential vorticity the dynamics are decomposed in terms of a solution forced by the three dimensional 3d potential vorticity and a solution forced by the surface boundary condition in density it is found that in the upper oceanic layers the balanced flow induced only by potential vorticity is strongly anticorrelated with that induced only by the surface density with a dominance of the latter the major consequence is that the 3d balanced motions can be determined from only the surface density and the characteristics of the basin scale stratification by solving an elliptic equation these properties allow for the possibility to reconstruct the 3d balanced velocity field of the upper layers from just the knowledge of the surface density by using a simpler model that is an effective surface quasigeostrophic model all these results are validated through the examination of a primitive equation simulation reproducing the dynamics of the antarctic circumpolar current

spatial and temporal variability of the m2 internal tide generation and propagation on the oregon shelf abstracta 1 km horizontal resolution model based on the regional ocean modeling system is implemented along the oregon coast to study average characteristics and intermittency of the m2 internal tide during summer upwelling wind driven and tidally driven flows are simulated in combination using realistic bathymetry atmospheric forcing and boundary conditions the study period is april through august 2002 when mooring velocities are available for comparison modeled subtidal and tidal variability on the shelf are in good quantitative agreement with moored velocity time series observations depth integrated baroclinic tidal energy flux ef its divergence and topographic energy conversion tec from the barotropic to baroclinic tide are computed from high pass filtered harmonically analyzed model results in a series of 16 day time windows model results reveal several hot spots of intensive tec on the slope at these locations tec is well balanced by ef divergence changes in background stratific

disturbance of the bothkennar clay prior to laboratory testing interpretation of laboratory tests in the characterization study of the bothkennar clay required an assessment to be made of the effects of disturbance prior to testing disturbance is shown to have occurred as a result of tube sampling sample transport and specimen preparation the effects of disturbance in the clay are to reduce the mean effective stress in the sample and shrink the initial bounding surface the consequences of these changes are illustrated for the case of unconsoli dated undrained triaxial tests undrained triaxial compression and extension tests after reconsolidation to in situ stress and oedometer tests reduction in peak strength stiffness yield stress and post yield compressibility are shown to be a consequence of disturbance the evaluation of sample quality on the basis of strains during reconsolidation is examined l interpretation des essais de laboratoire dans l etude de caracterisation de l argile de bothkennar necessita l evaluation des effets du remaniement avant essai

problems with piston core sampling mechanical and geochemical diagnosis abstract a series of sampling experiments using a piston corer equipped with data logging instruments has demonstrated that representative stratigraphic intervals of soft marine sediments may never be obtained with piston corers that use a non reference triggering system incidents of sediment by passing and flow in can occur throughout a single core resulting in both foreshortening and stretching of sedimentary units these problems are difficult to recognize by standard visual core logging techniques most of these problems are initiated by accelerations in the lowering cable that occur after tripping with resultant accelerations in the piston and fluctuations in the cavity pressure inside the core liner the non representative sampling can result in more than 1 0 m of missing stratigraphic units below the sediment interface and as much as 1 3 m of sediment flow in these problems can lead to miscalculations of sediment deposition rates by as much as a factor of two and can result in obtaining samples that are of no value for geotechnical analyses

linking changes in atmospheric dust deposition vegetation change and human activities in northwest spain during the last 5300 years a high resolution 5300 yr record of pollen and lithogenic elements k ca ti rb sr y zr from an ombrotrophic peat bog located in northwest spain reveals that the variations in the fluxes of lithogenic elements supplied to the bog by atmospheric deposition were coupled to the evolution of the vegetation of the area a strong negative correlation exists between the percentage of tree pollen and the concentration of lithogenic elements for example the correlation between total tree pollen and sr concentrations is 0 94 the main phases of decline of the deciduous forest occurred during known cultural periods late neolithic the metal ages the roman period the middle ages and the industrial period suggesting a close link between human activities fires and forest clearances changes in the vegetation and soil erosion the flux of lithogenic elements seems to have increased before a significant variation in pollen is detected which may indicate that changes in soil erosion are reflected earlie