a unified spectral parameterization for wave breaking from the deep ocean to the surf zone 1 a new wave breaking dissipation parameterization designed for phase averaged spectral wave models is presented it combines wave breaking basic physical quantities namely the breaking probability and the dissipation rate per unit area the energy lost by waves is first explicitly calculated in physical space before being distributed over the relevant spectral components the transition from deep to shallow water is made possible by using a dissipation rate per unit area of breaking waves that varies with the wave height wavelength and water depth this parameterization is implemented in the wavewatch iii modeling framework which is applied to a wide range of conditions and scales from the global ocean to the beach scale wave height peak and mean periods and spectral data are validated using in situ and remote sensing data model errors are comparable to those of other specialized deep or shallow water parameterizations this work shows that it is possible to have a seamless parameterization from the deep ocean to the surf zone

computation of wind wave spectra in coastal waters with swan on unstructured grids abstract an unstructured grid procedure for swan is presented it is a vertex based fully implicit finite difference method which can accommodate unstructured meshes with a high variability in geographic resolution suitable for representing complicated bottom topography in shallow areas and irregular shoreline the numerical solution is found by means of a point to point multi directional gauss seidel iteration method requiring a number of sweeps through the grid the approach is stable for any time step while permitting local mesh refinements in areas of interest a number of applications are shown to verify the correctness and numerical accuracy of the unstructured version of swan

globorotalia truncatulinoides growth and chemistry as probes of the past thermocline 1 shell size this work identifies features of the life history of the deep living planktonic foraminifer globorotalia truncatulinoides that offer possibilities for reconstructing characteristics of the past ocean s main thermocline part 1 considers two aspects of variation in shell size the predictability of growth related size changes which we need to calculate changes in shell chemistry and a model for environmentally forced changes in shell size frequency which suggests how shell size may be a direct source of paleoceanographic information even though size variation among shells of g truncatulinoides at the same stage of growth same number of chambers exceeds the size difference between successive growth stages growth related size changes are predictable because shells tend to grow at the same rate variation in initial shell size is sufficient to account for the large size variation found among shells at the same stage of growth several lines of evidence suggest that g truncatulinoides reproduces at 600 m in the water column and it appears that vertical mixing to that depth is required to return juvenile shells to the surface anything that prevents this such as shallowing of the thermocline can interfere with g truncatulinoides life history in such a way that its shell size frequency distributions are altered among shells falling to the seafloor from a reproducing population are large numbers of both juvenile and adult sizes and if reproduction is inhibited the frequencies of those sizes are reduced and the relative frequency of intermediate sized shells increases a paleoceanographically useful result of this is that the topography of the main thermocline tends to be reflected in the size frequency distribution of g truncatulinoides shells from the underlying sediments in areas where the top of the main thermocline is shallower than 600 m production of juveniles 125 177 m and reproductive adults 425 m is reduced leaving predominantly intermediate sized 212 355 m shells

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

middle eocene lower oligocene calcareous nannofossil biostratigraphy and paleoceanographic implications from site 711 equatorial indian ocean abstract nannofossil data from odp site 711 equatorial indian ocean yield a set of consistent reliable biohorizons that form the basis of a revised calcareous nannofossil biostratigraphy for the low latitude eocene oligocene we discuss 31 biohorizons occurring over an 11 myr time interval which we correlate to previous magnetostratigraphic data calcareous nannofossils from the middle eocene through the lower oligocene of the studied section are characterized by moderately well preserved assemblages consisting largely of low latitude and cosmopolitan species a significant nannofossil dissolution interval is evidenced at the middle eocene climatic optimum meco we document a significant increase in late eocene nannoplankton exhibiting a eutrophic preference analysis of the assemblage suggests important changes in the equatorial oceanic regime just before the onset of the eocene oligocene transition eot that foreshadow the more dramatic climatic shift of the early oligocene

living planktic foraminifera in the central tropical pacific ocean articulating the equatorial cold tongue during la nina 1992 abstract in cold tongue conditions of august september 1992 living planktic foraminifera in the equatorial pacific tracked circulation featuresand phytoplankton abundance an equatorial assemblage associated with the cool and productive equatorial region contained g bulloides a species often associated with tropical coastal upwelling as well as the nonspinose herbivores g menardii g glutinata p obliquiloculata and n dutertrei previously associated with equatorial environments within surface subtropical waters poleward of 5 n and 5 s g sacculifer g ruber and g conglobatus dominated foraminiferal populations these species have successfully adapted to oligotrophic conditions by exploiting dinoflagellate endosymbionts high standing stocks of these species in equatorial regions suggest that they can also thrive within equatorial light levels and temperatures a deep southern assemblage dominated by nonspinose g conglomerata and g tumida and spinose g aequilateralis had a subsurface maximum at 80 200 m outside of active upwelling and outcropped to the surface at 1 s from el nino to cold tongue conditions equatorial fauna reflected higher primary productivity and an increase in the role of advection by the south equatorial current

calcitic foraminiferal data confirmed by cadmium in aragonitic hoeglundina application to the last glacial maximum in the northern indian ocean a core top study of cadmium uptake into the shells of the aragonitic benthic foraminifera hoeglundina elegans demonstrates that the hoeglundina cd ca partition coefficient is close to 1 0 throughout the ocean cd uptake by hoeglundina is far less depth dependent than that of calcitic benthic foraminifera furthermore manganese carbonate does not precipitate on these aragonitic shells allowing for the recovery of cd estimates in some samples where calcitic species are spoiled by contaminating overgrowths because cd incorporation into hoeglundina shows little depth dependence a comparison of calcitic and hoeglundina cd data can be used to verify the assumption that the depth dependence observed for calcitic benthic foraminifera is time invariant this comparison has been undertaken in downcore and last glacial maximum lgm samples from the northern indian ocean aragonitic and calcitic foraminiferal estimates for cd in the lgm ocean are in excellent agreement this result indicates upper ocean estimates of lgm cd are reliable despite a factor of two variation in cd uptake by calcitic species over this depth range cd and 13c data indicate that the uppermost waters of the lgm arabian sea were strongly nutrient depleted relative to today but that the deepest waters of the northern bay of bengal had nutrient concentrations at least as high as or higher than modern levels a strong vertical gradient of increasing nutrients with increasing depth existed in both basins during the lgm a west to east gradient of increasing nutrient concentrations also is evident at all depths in the bay of bengal there is evidence for an enhanced gradient of nutrients increasing from south to north the lgm deep arabian sea and intermediate depth bay of bengal were nutrient depleted compared to the modern ocean however cd and 13c data indicate that nutrient depletion in the northern indian ocean did not exceed that of the deep eastern tropical pacific except during the latest part of oxygen isotope stage 2 and according to cd data only the early stages of deglaciation during oxygen isotope stage 3 and early stage 2 cd in the northern indian ocean and cd in the eastern tropical pacific were indistinguishable although both regions have lower cd at these times compared to the holocene

deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation the degree of similarity of the 13c records of the planktonic foraminiferal species n pachyderma and of the benthic foraminiferal genus cibicides in the high latitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle whereas continuous formation of deep water is recognized in the southern ocean the norwegian sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation however deep water formed in the north atlantic south of the norwegian sea during the last climatic cycle as early as isotope substage 5d and this area was also the only active northern source during stages 4 2 a detailed reconstruction of the geographic distribution of 13c in benthic foraminifera in the atlantic ocean during the last glacial maximum shows that the most important deepwater mass originated from the southern ocean whereas the glacial north atlantic deep water cannot be traced south of 40 n at shallower depth an oxygenated 13c rich intermediate water mass extended from 45 n to 15 s in the pacific ocean a ventilation higher than the modern one was also found in open ocean in the depth range 700 2600 m and is best explained by stronger formation of intermediate water in high northern latitudes

paleoenvironmental evolution in a high stressed cold seep system vicchio marls miocene northern apennines italy abstract excellent exposures of miocene seep carbonates enclosed in marine marly sediments vicchio outcrops in the northern apennines italy offer the opportunity to highlight the evolution of a fossil seep ecosystem and the response of benthic communities to high stressed environmental conditions for this purpose seep related facies and molluscs within carbonate bodies have been studied coupled with benthic foraminiferal assemblages and carbon and oxygen isotopes in the enclosing marls the integrated planktonic foraminiferal and calcareous nannofossil biostratigraphy has allowed us to constrain the seepage within well calibrated bioevents and to stress the relationships with paleoclimatic and paleoceanographic variations during the middle miocene in the mediterranean area our biostratigraphic data indicate that the onset of the seepage approximates the mi3b cooling event 13 82 ma and the seepage system lasts for 400 kyr the evolution of the vicchio cold seep system passes through four phases 1 the onset of the seepage characterized by a pervasive flow of methane rich fluids is inferred by 13c depletion of marly sediments and by prevailing benthic foraminifera indicative of suboxic conditions at the sea floor 2 the methane flow becomes focused causing the precipitation of wide pinnacle like carbonate bodies which contain giants lucinids enclosing marls indicate well oxygenated conditions possibly enhanced by paleoceanographic variations connected to the mi3b cooling event 3 the appearance of the vesicomyid christineconcha cf c regab and the absence of lucinids in seep carbonates suggest stable methane rich fluid emissions higher flow rates locally favoured the flourishment of bacterial mats benthic foraminifera show abundance peaks of organic matter depending taxa 4 the reduced intensity of methane rich fluid flows favours the precipitation of stratiform carbonate bodies along strike the macrofauna is characterized by the presence of both vesicomyidae and giant lucinids foraminiferal assemblages in the enclosing marls indicate the restoration of well oxygenated conditions

cadmium chemical tracer of deepwater paleoceanography the oceanic distribution of cadmium resembles that of phosphorus because the cadmium content of foraminiferal shells is governed by the cadmium content of seawater planktonic and benthic fossil shells can be used to infer nutrient distributions within ancient oceans empirical studies demonstrate that cadmium in benthic foraminiferal shells is related to the bottom water composition through a proportionality constant d 2 9 this constant is the same for each of the species studied cibicidoides wuellerstorfi cibicidoides kullenbergi nuttallides umbonifera and uvigerina spp downcore cadmium data from high quality pacific and atlantic sediment cores suggest that the cadmium inventory of the ocean did not change significantly between the most recent glacial maximum and the present hence changes in the cadmium content of fossils at a site directly reflect changes in nutrient distributions due to altered oceanic circulation patterns studies of cadmium in pleistocene sediments show that deep ocean circulation patterns were significantly different during the most recent glacial maximum in the western north atlantic ocean the nutrient content of waters from 2500 to 3500 m was twice as high during glacials as during interglacial periods signifying an increase in the proportion of waters of antarctic origin in this depth interval and a decrease but not a cessation in the flux of north atlantic deep waters through this depth range below 3500 m the nutrient increase was greater indicating a higher proportion of antarctic bottom water above 2500 m the nutrient content was lower during glacial periods than it has been during interglacial times the cd content of high latitude north atlantic and southern ocean surface waters does not show a significant glacial interglacial change which argues against theories for changes atmospheric carbon dioxide that require changes in high latitude nutrient concentrations

paleoceanographic implications of the difference in deep sea sediment mixing between large and fine particles more and more paleoceanographic studies are performed on different size fractions of deep sea sediments although it has been a controversial issue for some time the bioturbation process depends on the particle size and can in principle decouple paleoceanographic records obtained in the same core this problem is studied by using a simple mixing model which allows the derivation of analytical equations for both the expected phase shift and relative attenuation of signals carried by different size fractions depending on several parameters the time shift and relative attenuation can be on the order of a few millenia and 50 respectively however high sedimentation rates 10 20 cm kyr minimize these potential complications allowing us to study millenium scale events in well chosen sedimentary environments

distribution of recent nannofossils beneath the benguela system southwest african continental margin abstract one hundred and forty eight surface samples recovered from the southwest african continental margin 35 17 s have been examined for their nannofossil content coccolith abundance is high in sediments from the deep water areas but declines toward the coast under the main areas of upwelling five distinct bathymetric oceanographic assemblages can be characterized by their nannofossil content coastal upwelling orange bank intermediate southern deep water and northern deep water angola current these distinctions are based on the distribution of eight ecologically significant taxa in order of decreasing abundance they are gephyrocapsa oceanica helicopontosphaera kamptneri cyclococcolithina leptopora coccolithus pelagicus syracosphaera div sp thoracosphaera div sp rhabdosphaera div sp and umbilicosphaera sibogae sea surface temperature and salinity variations which correlate with the extent and intensity of the main upwelling cells are thought to be the most important controls on coccolith distribution although nutrient availability and reduction of surface water transparency may be of local importance the exclusion of three stratigraphical index species for the quaternary emiliania huxleyi gephyrocapsa caribbeanica and g ericsonii from the quantitative analysis will permit the future application of these results to paleoceanographic reconstructions of the benguela system in pleistocene core sections

planktonic foraminifera calcareous nannoplankton and ascidian variations during the last 25 kyr in the southwestern atlantic a paleoproductivity signature micropaleontological and geochemical analyses from western south atlantic core san 76 off southeast brazil revealed changes in stable isotope values and in the assemblages of calcareous nannoplankton and planktonic foraminifera during the past 25 kyr that point to significant paleoceanographic and climatic changes leading to an increase in productivity during the last deglaciation the enhanced surface productivity was clearly indicated by increased relative abundances of the planktonic foraminifera globigerina bulloides and neogloboquadrina dutertrei and the decreased values of 13 c in planktonic foraminiferal tests a coeval shoaling of the nutricline and thermocline was indicated by decreased relative abundances of the calcareous nannoplankton florisphaera profunda and an increased relative abundance of the planktonic foraminifera globorotalia truncatulinoides right coiling we speculate that these changes are related to n s shifts of the atlantic intertropical convergence zone itcz a significant increase in the cd ca ratio and decrease in 13 c values in the benthic foraminifer hoeglundina elegans along with a significant increase in the relative abundance of ascidian spicules during the deglaciation suggest that benthic communities in this area strongly benefited from increased surface water productivity 2007 elsevier b v all rights reserved

the vitoria eddy and its relation to the brazil current in late austral summer 1991 a cyclonic thermocline eddy was detected in the subtropical western south atlantic off the brazilian shelf near the city of vitoria this vitoria eddy was tracked for 55 days by surface drifters drogued at 100 m depth the drifters had been deployed in the western boundary current regime by fs meteor as part of a basinwide surface current study the analysis of a combined ctd xbt section across the vitoria eddy together with drifter data and satellite images of the thermal surface structure revealed the unexpected complexity of the region the eddy interacted not only with the local topography and the brazil current located farther offshore but also with an extended upwelling regime north of cabo frio the hydrographic and kinematic properties and anomalies of the vitoia eddy are analyzed and compared with similar vortices described elsewhere in literature

deep sea corals off brazil verify a poorly ventilated southern pacific ocean during h2 h1 and the younger dryas abstract simultaneous 14 c and th u dating of deep sea corals are useful for reconstructing the intensity of deep ocean circulation in the past as they deliver the time between the gas exchange of the water with the atmosphere and the incorporation of the 14 c in the carbonates adkins and boyle 1997 adkins et al 1998 mangini et al 1998 th u ages of deep sea corals sampled in sediment cores from locations off the coast of brazil bathed by antarctic intermediate water at depths between 600 and 800 m group close to heinrich events h2 h1 and the younger dryas the 14 c of the water bathing the corals starts to decrease approximately 2 kyr before the heinrich events and decreases to values 400 lower than the corresponding back tracked atmospheric values the timing and the magnitude of the decrease is similar to that observed in intermediate water in the n pacific off baja california marchitto et al 2007 and in the eastern pacific stott et al 2009 high ventilation ages partly exceeding 4000 years are an unambiguous indication for a reduction of north atlantic deep water formation during h2 h1 and the yd as deduced from higher 231 pa 230 th activity ratios and from end in n atlantic ocean sediments mcmanus et al 2004 pahnke et al 2008 yu et al 1996 they also could indicate a poorly oxygenated southern pacific ocean at the end of the heinrich events

simmax a modern analog technique to deduce atlantic sea surface temperatures from planktonic foraminifera in deep sea sediments we present a data set of 738 planktonic foraminiferal species counts from sediment surface samples of the eastern north atlantic and the south atlantic between 87 n and 40 s 35 e and 60 w including published climate long range investigation mapping and prediction climap data these species counts are linked to levitus s 1982 modern water temperature data for the four caloric seasons four depth ranges 0 30 50 and 75 m and the combined means of those depth ranges the relation between planktonic foraminiferal assemblages and sea surface temperature sst data is estimated using the newly developed simmax technique which is an acronym for a modern analog technique mat with a similarity index based on 1 the scalar product of the normalized faunal percentages and 2 a weighting procedure of the modern analog s ssts according to the inverse geographical distances of the most similar samples compared to the classical climap transfer technique and conventional mat techniques simmax provides a more confident reconstruction of paleo ssts correlation coefficient is 0 994 for the caloric winter and 0 993 for caloric summer the standard deviation of the residuals is 0 90 c for caloric winter and 0 96 c for caloric summer at 0 m water depth the sst estimates reach optimum stability standard deviation of the residuals is 0 88 c at the average 0 to 75 m water depth our extensive database provides sst estimates over a range of 1 4 to 27 2 c for caloric winter and 0 4 to 28 6 c for caloric summer allowing sst estimates which are especially valuable for the high latitude atlantic during glacial times an electronic supplement of this material may be obtained on adiskette or anonymous ftp from kosmos agu org login toagu s ftp account using anonymous as the username and guestas the password go to the right directory by typing cd append typels to see what files are available type get and the name of the file toget it finally type exit to leave the system paper 95pa01743 simmax a modern analog technique to deduce atlantic sea surfacetemperatures from planktonic foraminifera in deep sea sediments uwepflaumann josette duprat claude pujol and laurent d labeyrie diskette may be ordered from american geophysical union 2000florida avenue n w washington dc 20009 payment mustaccompany order

atlantic ocean circulation during the younger dryas insights from a new cd ca record from the western subtropical south atlantic author posting american geophysical union 2003 this article is posted here by permission of american geophysical union for personal use not for redistribution the definitive version was published in paleoceanography 18 2003 1086 doi 10 1029 2003pa000888

spectral wave modeling in fringing reef environments abstract this study examines the implementation and validity of phase averaged spectral models in describing wave transformation over fringing reefs the wave breaking mechanism over the abrupt reef crest dissipation due to bottom friction and nonlinear energy transfer over the reef flat set the problem apart from general applications in non tropical settings the simulating wave nearshore swan model which is widely used in coastal engineering applications has embedded parameterizations of these surf zone processes for examination in addition we extend the model to include a recently implemented bottom friction source term for tropical reefs comparisons of model predictions with laboratory and field observations over fringing reefs identify promising wave breaking and bottom friction parameterizations for calibration the calibrated parameterizations enable swan to reproduce the observed wave height and setup and extend the applicability of spectral models to fringing reef environments swan however lacks the parameterization to describe the nonlinear energy transfer toward the infra gravity band that was observed in the laboratory and field studies

holocene oscillations of southwest atlantic shelf circulation based on planktonic foraminifera from an upwelling system off cabo frio southeastern brazil the brazil current bc is a relevant feature in the atlantic meridional overturning circulation amoc its behavior during slowdown or intense amoc remains poorly known because of the lack of pal

spectral wave dissipation over a barrier reef 1 a 2 week field experiment was conducted to measure surface wave dissipation on a barrier reef at kaneohe bay oahu hawaii wave heights and velocities were measured at several locations on the fore reef and the reef flat which were used to estimate rates of dissipation by wave breaking and bottom friction dissipation on the reef flat was found to be dominated by friction at rates that are significantly larger than those typically observed at sandy beach sites this is attributed to the rough surface generated by the reef organisms which makes the reef highly efficient at dissipating energy by bottom friction results were compared to a spectral wave friction model which showed that the variation in frictional dissipation among the different frequency components could be described using a single hydraulic roughness length scale surveys of the bottom roughness conducted on the reef flat showed that this hydraulic roughness length was comparable to the physical roughness measured at this site on the fore reef dissipation was due to the combined effect of frictional dissipation and wave breaking however in this region the magnitude of dissipation by bottom friction was comparable to wave breaking despite the existence of a well defined surf zone there under typical wave conditions the bulk of the total wave energy incident on kaneohe bay is dissipated by bottom friction not wave breaking as is often assumed for sandy beach sites and other coral reefs

modeling of nonlinear wave propagation over fringing reefs abstract the applicability of existing nonlinear triad spectral models for steep slopes 0 1 0 2 characteristic of reef environments was investigated using both deterministic phase resolving and stochastic phased averaged formulations model performance was tested using laboratory observations of unidirectional wave transformation over steep and smooth bathymetry profiles the models developed for mild slopes were implemented with minimal modifications the inclusion of breaking parametrizations and linear steep slope corrections required by laboratory data the deterministic model produced typically more accurate predictions than the stochastic one but the phase averaged formulation proved fast enough to allow for an inverse modeling search for the optimal breaking parametrization the effects of the additional assumptions of the stochastic approach resulted in a slower than observed evolution of the infragravity band despite the challenge posed by the fast wave evolution and energetic breaking characteristic to the steep reef slopes both formulations performed overall well and should be considered as good provisional candidates for use in numerical investigation of wave current interaction processes on steep reefs

mechanisms behind the temporary shutdown of deep convection in the labrador sea lessons from the great salinity anomaly years 1968 71 abstractfrom 1969 to 1971 convection in the labrador sea shut down thus interrupting the formation of the intermediate dense water masses the shutdown has been attributed to the surface freshening induced by the great salinity anomaly gsa a freshwater anomaly in the subpolar north atlantic the abrupt resumption of convection in 1972 in contrast is attributed to the extreme atmospheric forcing of that winter here oceanic and atmospheric data collected in the labrador sea at ocean weather station bravo and a one dimensional mixed layer model are used to examine the causes of the shutdown and resumption of convection in detail these results highlight the tight coupling of the ocean and atmosphere in convection regions and the need to resolve both components to correctly represent convective processes in the ocean they are also relevant to present day conditions given the increased ice melt in the arctic ocean and from the greenland ice sheet the analysis herein shows that the shutdown was initiat

wind waves and moveable bed bottom friction abstract effects of moveable bed bottom friction for wave observations and wave modeling are investigated using a state of the art bottom friction model this model combines the hydrodynamic friction model of madsen et al with a moveable bed roughness model based on grant and madsen analyzing the present model for idealized swell cases it is shown that swell might result in wave generated sand ripples the large change of roughness corresponding to initial ripple formation results in a preferred wave height for swell related to bathymetric scales as generally occur in shelf seas away from the coast the corresponding wave generated bottom roughness is not defined by the local wave conditions but is related to the overall energy balance of the wave field sediment data thus is imperative for the interpretation of observed decay rates and friction factors for swell for idealized depth limited wind seas near bottom wave motion is expected to generate partially washed out ripples and moderate sheet flo

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

oscillatory flow across an irregular boundary 1 laboratory experiments examining oscillatory flow along a coastline or isobath with a series of headlands or ridges reveal a mechanism for transfer of momentum and mass from the boundary into the interior flow through the establishment of organized residual flow patterns particle imaging velocimetry is used to visualize the vorticity field and to quantify large scale residual circulations generated near the region of roughness two flow regimes are observed for differing ratios of along coast tidal excursion l to the length of the roughness region d for l d 1 a weak inflow is produced in the vicinity of the roughness region with a corresponding alongshore flow away from the region for l d 1 a strong outflow jet is established near the center of the roughness region the two flow regimes result from different residual vorticity patterns and rely on eddies being long lived relative to the tidal period thus these results are relevant to flows in which dissipation is weak relative to the mean flow kinetic energy such as for tidal flow in deep water flow past a single roughness element is used as an analog to tidal flow past a headland and is represented by the high l d limit

depth limited design wave heights in very flat regions abstract engineers working on the flat tops of offshore coral reefs or offshore banks require design criteria for depth limited wave heights over horizontal beds particularly in regions leeward of the bank or reef edge surf zone this paper presents convincing evidence of the fact that in engineering practice both in the laboratory and in the field the value of 0 55 is the largest wave height to water depth ratio realizable for stable shallow water oscillatory waves propagating in water of constant depth horizontal bed this value is much lower than that often used in engineering practice namely a value of about 0 8 which is historically based on the theoretical considerations and laboratory experiments associated with solitary waves this result based on a review of laboratory data and the original results of a major field experiment undertaken on the great barrier reef of australia leads to a significant reduction in design wave forces design crest levels and wave induced scour velocities at the bed

the last 100 000 years in the western mediterranean sea surface water and frontal dynamics as revealed by coccolithophores a quantitative analysis was carried out on coccolith assemblages from two pleistocene cores k1 and k10 from the western mediterranean the distribution of selected coccolithophore species provides new paleoclimatic and paleoceano graphic data a continuous sequence from the top of isotope stage 5 to the holocene was recorded the reversal in dominance between gephyrocapsa muellerae and emiliania huxleyi was dated in both cores at ca 73 ka at about 47 ka e huxleyi shows a regular increase whereas g muellerae progressively decreases in abundance during interglacial periods high concentrations of coccoliths are observed whereas in glacial times coccoliths are more diluted and the percentage of reworked forms increases as a consequence of the higher terrigenous input after taking careful account of the dilution factor we conclude that the production of coccolithophores was higher during warm periods maxima in coccolith concentrations coincide with highstand episodes probably as a result of the intensification of the atlantic flux into the mediterranean across the gibraltar strait this intensification could have produced an increase in nutrient content in the surface mediterranean waters during cold periods the western mediterranean front underwent a reduction in activity probably due to an increase in the saline and or thermal gradients between the superficial waters and intermediate waters in the liguro provencal basin

planktonic foraminiferal assemblages preserved in surface sediments correspond to multiple environment variables abstract here we investigate the relationships between modern planktonic foraminiferal species assemblages from atlantic and pacific core top sediment samples and 35 water column and preservation properties using canonical correspondence analysis cca cca finds two faunal dimensions axes that are most highly correlated to the environmental variables and describes each axis in terms of the best linear combination of environmental variables cca axis 1 30 4 of the faunal variance is related primarily to mean annual sea surface temperature sst r 0 96 cca axis 2 7 9 of the faunal variance is related to environmental variability associated with an inverse relationship between sst and surface salinity as well as pycnocline phosphate concentrations the seasonal range in nitrate concentrations water depth and chlorophyll concentrations at the sea surface based on this clustering of nutrient and chlorophyll on axis 2 we infer an ecological response to oceanic fertility no evidence is found for a unique dissolution influence suggesting that sea floor carbonate ion concentration cannot be estimated reliably from planktonic foraminiferal assemblages our results support the use of foraminiferal assemblages to estimate mean annual sst

paleoceanographic interpretations of coccoliths and oxygen isotopes from the sediment surface of the southwest indian ocean abstract the distribution of forty four coccolithophore species in one hundred deep sea core tops from the southwest indian ocean is described three coccolith assemblages have been recognised maputo agulhas current and deep water by the relative abundances of four ecologically significant coccolithophore species gephyrocapsa oceanica emiliania huxleyi calcidiscus leptoporus and umbilicosphaera sibogae their biogeographical distribution appears to be related to water temperature nutrient concentration and dissolution the degree of preservation of coccoliths and foraminifera indicates that the carbonate lysocline lies somewhere between 3500 and 4000 m resulting in the concentration of dissolution resistant microfossils below this depth stable oxygen isotope ratios of the planktonic foraminiferal species globigerinoides sacculifer range between 1 5 to 1 0 pdb equal to 22 8 25 1 c and occur in a narrow band on the sea floor beneath the a route of the agulhas current these values are about 0 5 per mil pdb lighter than samples analyzed on either side of this band and can be explained by the agulhas current s elevated temperature at the ocean surface of 2 3 c thus an oxygen isotope imprint of the agulhas current exists beneath it on the sea floor the agulhas current is probably the major factor influencing sedimentation sediment distribution patterns and geological features in the study area at present it is voluminous and fast flowing possibly eroding sediments up to 2500 m below the surface the oxygen isotope ratios and nannoplankton counts obtained in this study indicate however that the majority of samples are most probably recent or at least not older than 85 000 years this implies that sediments are accumulating on the ocean floor and that the agulhas current does not have a pronounced erosional influence at least in areas from which cores were retrieved for this study

globorotalia truncatulinoides as indicator of upper ocean thermal structure during the quaternary evidence from the south china sea and okinawa trough abstract globorotalia truncatulinoides is shown to be indicative of upper ocean thermal structure and sensitive to the thermocline fluctuations and the thickness of the north pacific subtropical mode water npstmw thermostads for the quaternary in the south china sea scs and okinawa trough during the last 1 5 ma the relative abundance percentage of g truncatulinoides displayed long term oscillations on a time scale longer than the glacial interglacial cycle but with two major changes around 550 400 ka and 115 55 ka bp it decreased to near zero during 550 400 ka bp and then disappeared from the equatorial indian and pacific oceans this suggests that the thermocline depth and the scale of winter deep mixing decreased at that time interval and since then the linkage between the scs and the equatorial oceans at intermediate depths remarkably weakened and the npstmw strongly influenced the scs the predominance of left coiling g truncatulinoides together with the occurrence of globoquadrina conglomerata in the western north pacific between 115 and 55 ka bp indicates a deep thermocline and very thick npstmw thermostads a decreasing trend in the relative abundance of g truncatulinoides from marine isotopic stages 7 to 1 is evident in the scs indicating a progressive reduction of the npstmw thermostads after the last glacial maximum g truncatulinoides increased in abundance but abruptly disappeared between 8 and 4 ka bp from the scs and okinawa trough implying a mid holocene reduction in the npstmw thermostad thickness

glacial water mass geometry and the distribution of δ13c of σco2 in the western atlantic ocean 1 oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa cibicidoides and planulina from 25 new piston cores gravity cores and multicores from the brazil margin the cores span water depths from about 400 to 3000 m and intersect the major water masses in this region these new data fill a critical gap in the south atlantic ocean and provide the motivation for updating the classic glacial western atlantic 13c transect of duplessy et al 1988 the distribution of 13c of co2 requires the presence of three distinct water masses in the glacial atlantic ocean a shallow 1000 m southern source water mass with an end member 13c value of about 0 3 0 5 vpdb a middepth 1500 m northern source water mass with an end member value of about 1 5 and a deep 2000 m southern source water with an end member value of less than 0 2 and perhaps as low as the 0 9 values observed in the south atlantic sector of the southern ocean ninnemann and charles 2002 the origins of the water masses are supported by the meridional gradients in benthic foraminiferal 18o a revised glacial section of deep water 13c documents the positions and gradients among these end member intermediate and deep water masses the large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation

late pleistocene palaeocenography of the tasman sea implications for the dynamics of the warm pool in the western pacific quantitative analyses of planktonic foraminifera from 47 core top samples spatially distributed through the tasman sea and cores rc12 113 e36 23 dsdp sites 588 592 593 and odp site 828a from a n s transect supplemented with stable isotope analyses indicate that three planktonic foraminiferal assemblages defined by factor analysis on core top material correlated with three hydrographic modes defined on the basis of sea surface temperatures temperature profiles seasonal changes in temperature and mixed layer depth similar assemblages were found in down core material along the tasman sea transect that combined with semi quantitative analyses of foraminiferal assemblages provinces and the coiling ratio of globorotalia truncatulinoides allows reconstruction of the position of the tasman front or the subtropical divergence during the late brunhes chron the results indicate that the tasman front migrated from its present position at 30 s to 26 s during the last glacial maximum the northward migration of the tasman front may indicate a reduction in volume of the equatorial warm pool and or an increase in the strength of cool subtropical water masses the late pleistocene distribution of g truncatulinoides left coiling from appears to be related to the formation of subantarctic mode water thermostads this relationship may explain the evolutionary origin of this species in the southwest pacific at 2 4 ma simultaneously with the onset of late pliocene glaciations the past position of the subtropical convergence is reconstructed by means of coilingv directions in neogloboquadrina pachyderma the convergence apparently migrated slightly north of 43 s core e36 23 during glacial stages 6 10 and 12

height limits in top down and bottom up wave environments this paper isolates two environments or processes in which maximum stable wave heights can be attained in water of constant depth in top down environments the maximum stable wave height compatible with the depth is approached from above while in bottom up environments it is approached from below the analyses of field data from these two environments are compared in water of constant depth the individual waves in naturally occurring bottom up wave trains are shown to conform to the same upper height limit criteria as naturally occurring top down wave trains that limit being the same function developed from monochromatic laboratory waves however important differences are found in the shallow and transitional wave content of the wave populations generated by the two different processes

wave setup over a pacific island fringing reef 1 measurements obtained across a shore attached fringing reef on the southeast coast of the island of guam are examined to determine the relationship between incident waves and wave driven setup during storm and nonstorm conditions wave setup on the reef flat correlates well r 0 95 and scales near the shore as approximately 35 of the incident root mean square wave height in 8 m water depth waves generated by tropical storm man yi result in a 1 3 m setup during the peak of the storm predictions based on traditional setup theory steady state inviscid cross shore momentum and depth limited wave breaking and an idealized model of localized wave breaking at the fore reef are in agreement with the observations the reef flat setup is used to estimate a similarity parameter at breaking that is in agreement with observations from a steeply sloping sandy beach a weak 10 increase in setup is observed across the reef flat during wave events the inclusion of bottom stress in the cross shore momentum balance may account for a portion of this signal but this assessment is inconclusive as the reef flat currents in some cases are in the wrong direction to account for the increase an independent check of fringing reef setup dynamics is carried out for measurements at the neighboring island of saipan with good agreement

astronomical forcing of contrasting rainfall changes in tropical south america between 12 400 and 8800 cal yr b p abstract today precipitation over tropical south america is largely controlled by the seasonal movements of the inter tropical convergence zone itcz during the summer the itcz is shifted southward due to the warming of the continent paleoclimate data from southeastern amazonia and the central andes indicate that these two areas evolved similarly during the last 30 000 yr however between 12 400 and 8800 cal yr b p eastern amazonia received substantial moisture whereas the bolivian altiplano was arid this suggests that the itcz during summer was then farther north than it is today

shock capturing boussinesq type model for nearshore wave processes this paper describes the formulation and validation of a nearshore wave model for tropical coastal environment the governing boussinesq type equations include the conservative form of the nonlinear shallow water equations for shock capturing a riemann solver supplies the inter cell flux and bathymetry source term while a godunov type scheme integrates the evolution variables in time the model handles wave breaking through momentum conservation with energy dissipation based on an eddy viscosity concept the computed results show very good agreement with laboratory data for wave propagation over a submerged bar wave breaking and runup on plane beaches as well as wave transformation over fringing reefs the model accurately describes transition between supercritical and subcritical flows as well as development of dispersive waves in the processes

wave transformation across the inner surf zone sea and swell wave heights observed on transects crossing the mid and inner surf zone on three beaches a steep concave up beach a gently sloped approximately planar beach and a beach with an approximately flat terrace adjacent to a steep foreshore were depth limited i e approximately independent of the offshore wave height consistent with previous observations the wave evolution is well predicted by a numerical model based on the one dimensional nonlinear shallow water equations with bore dissipation the model is initialized with the time series of sea surface elevation and cross shore current observed at the most offshore sensors located about 50 to 120 m from the mean shoreline in mean water depths 0 80 to 2 10 m the model accurately predicts the cross shore variation of energy at both infragravity nominally 0 004 f 0 05 hz and sea swell here 0 05 f 0 18 hz frequencies in models of surf zone hydrodynamics wave energy dissipation is frequently parameterized in terms of s the ratio of the sea swell significant wave height to the local mean water depth the observed and predicted values of s increase with increasing beach slope and decreasing normalized by a characteristic wavenumber k water depth kh and are well correlated with kh a measure of the fractional change in water depth over a wavelength errors in the predicted individual values of s are typically less than 20 it has been suggested that infragravity motions affect waves in the sea swell band and hence s but this speculation is difficult to test with field observations numerical simulations suggest that for the range of conditions considered here s is insensitive to infragravity energy levels

a multiproxy approach to the climate and marine productivity variations along mis 5 in se brazil a comparison between major components of calcareous nannofossil assemblages and geochemical records abstract in this study changes in terrigenous input based on geochemical elementary ratios e g fe ca ti ca ba ca fe k and on marine primary productivity based on calcareous nannofossil assemblages from the southeastern brazilian continental margin are analyzed for the time interval 140 to 55 ka mis 6 to mis 4 variation in the terrigenous input follows the continental paleoclimate records based on speleothems from se brazil and the summer insolation curve from low latitudes for the southern hemisphere in turn marine productivity shows a high correlation with terrigenous input terrigenous input maxima correlate to increased marine productivity during sub stages 5d and 5b both terrigenous input and marine productivity would be strongly controlled by changes in the intertropical convergence zone and winds associated with the south atlantic convergence zone thus ne winds would have prevailed promoting humidity and precipitation rates over se brazil as well as an intensified wind driven upwelling and eddies associated with the brazil current which favored the presence of a shallow nutricline our results are consistent with that of different proxies presented in other studies providing estimates of changes on the precipitation rate of se brazil and changes on marine productivity in the south atlantic ocean during mis 5

the deglacial history of the western tropical atlantic as inferred from high resolution stable isotope records off northeastern brazil abstract the western south atlantic boundary currents represent a sensitive system within the global thermohaline circulation thc we investigated the impact of deglacial thc changes on the western tropical atlantic studied in six high resolution sediment cores from the upper continental slope of brazil the stratigraphy of the cores is mainly based on 14c ams dating of monospecific foraminiferal samples changes in the upper layer tropical ocean during the deglaciation are inferred from stable oxygen isotope measurements on planktic and benthic foraminifera variations in the 18o residuals are assumed to be mainly temperature related during the oldest and younger dryas cooling periods two major deglacial thc disturbances are reported from north atlantic sediment cores concomitant to the repeated thc slowdown we observe an upper layer warming in the tropical ocean a reduced northward heat export from the tropical areas during these periods weak north brazil current is additionally reflected by low meridional gradients in the stable oxygen records this generally agrees with results from coupled ocean atmosphere models

distribution of coccoliths in surface sediments of the south eastern south atlantic ocean ecology preservation and carbonate contribution abstract recent coccoliths from 52 surface sediment samples recovered from the south eastern south atlantic were examined qualitatively and quantitatively in order to assess the controlling mechanisms for their distribution patterns such as ecological and preservational factors and their role as carbonate producers total coccolith abundances range from 0 2 to 39 9 coccoliths 109 g 1 sediment four assemblages can be delineated by their coccolith content characterising the northern benguela the middle to southern benguela the walvis ridge and the deeper water distinctions are based on multivariate ordination techniques applied on the relative abundances of the most abundant taxa emiliania huxleyi calcidiscus leptoporus gephyrocapsa spp coccolithus pelagicus and subtropical to tropical species the coccolith distribution seems to be temperature and nutrient controlled co varying with the seaward extension of the upwelling filament zone in the benguela a preservation index cex based on the differential dissolution behaviour of the delicate e huxleyi and gephyrocapsa ericsonii versus the robust c leptoporus is applied in order to detect the position of the coccolith lysocline although some samples were recognised as dissolution affected the distribution of the coccoliths in the surface sediments reflects the different oceanographic surface water conditions mass estimations of the coccolith carbonate reveal coccoliths to be only minor contributors to the carbonate preserved in the surface sediments the mean computed coccolith carbonate content is 17 wt equivalent to a mean contribution of 23 to the bulk carbonate

sea surface temperatures in the equatorial and south atlantic ocean during the last glacial maximum 23 19 ka 1 we used planktic foraminiferal assemblages in 70 sediment cores from the tropical and subtropical south atlantic ocean 10 n 37 s to estimate annual mean sea surface temperatures ssts and seasonality for the last glacial maximum with a modified version of the imbrie kipp transfer function method iktf that takes into account the abundance of rare but temperature sensitive species in contrast to climap project members 1981 the reconstructed ssts indicate cooler glacial ssts in the entire tropical subtropical south atlantic with strongest cooling in the upwelling region off namibia 7 10 c and smallest cooling 1 2 c in the western subtropical gyre in the western atlantic our data support recent temperature estimates from other proxies in the upwelling regions in the eastern atlantic our data conflict with sst reconstructions from alkenones which may be due to an environmental preference of the alkenone producing algae or to an underestimation of foraminiferal ssts due to anomalous high abundances of n pachyderma sinistral

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

on the small scale fractal geometrical structure of a living coral reef barrier topographical complexity of coral reefs is of primary importance for a number of hydrodynamical and ecological processes the present study is based on a series of high resolution seabottom elevation measurements along the maupiti barrier reef french polynesia several statistical metrics and spectral analysis are used to characterize the spatial evolution of the coral geometrical structure from the reef crest to the backreef a consistent fractal like power law exists in the spectral density of bottom elevation for length scales between 0 1 and 7m while at larger scale the reef structure shows a different pattern such a fine characterization of the reef geometrical structure provides key elements to reconstruct the reef history to improve the representation of reef roughness in hydrodynamical models and to monitor the evolution of coral reef systems in the global change context

spatial and temporal offsets between proxy records in a sediment drift chronologies for late quaternary marine sediment records are usually based on radiocarbon ages of planktonic foraminifera signals carried by other sedimentary components measured in parallel can provide complementary paleoclimate information a key premise is that microfossils and other indicators within a given sediment horizon are of equal age we show here that haptophyte derived alkenones isolated from bermuda rise drift sediments are up to 7000 years older than coexisting planktonic foraminifera this temporal offset which is apparently due to lateral transport of alkenones on fine grained particles from the nova scotian margin markedly influences molecular estimates of sea surface temperatures more broadly the observation raises questions about both the temporal and the geographic fidelity of paleoenvironmental records encoded by readily transported components of sediments

modeling of depth induced wave breaking under finite depth wave growth conditions 1 recent studies have shown that the spectral wind wave model swan simulating waves nearshore underestimates wave heights and periods in situations of finite depth wave growth in this study this inaccuracy is addressed through a rescaling of the battjes and janssen 1978 bore based model for depth induced breaking considering both sloping bed surf zone situations and finite depth wave growth conditions it is found that the variation of the model error with the breaker index bj in this formulation differs significantly between the two types of conditions for surf zones clear optimal values are found for the breaker index by contrast under finite depth wave growth conditions model errors asymptotically decrease with increasing values of the breaker index weaker dissipation under both the surf zone and finite depth wave growth conditions optimal calibration settings of bj were found to correlate with the dimensionless depth kpd where kp is the spectral peak wave number and d is the water depth and the local mean wave steepness subsequently a new breaker index based on the local shallow water nonlinearity expressed in terms of the biphase of the self interactions of the spectral peak is proposed implemented in the bore based breaker model of thornton and guza 1983 this breaker index accurately predicts the large difference in dissipation magnitudes found between surf zone conditions and finite depth growth situations hence the proposed expression yields a significant improvement in model accuracy over the default battjes and janssen 1978 model for finite depth growth situations while retaining good performance for sloping bed surf zones

late pleistocene to holocene palaeoclimates and palaeoenvironments inferred from palynofacies and dinoflagellates cysts in santos basin offshore brazil abstract we analyse late pleistocene to holocene palynofacies and dinoflagellates in a sedimentary core pc prima 4 collected on the northern offshore shelf of the santos basin of brazil which covers the last 29 429 cal yrs bp the aim of this study is to better understand changes in climate and oceanographic circulation that affected this region since the last glacial maximum lgm and the 120 m rise in sea level that followed the organic matter in the core shows characteristics consistent with an oxygenized proximal shelf with incursions of continental elements which evolved into a more distal dysaerobic anoxic environment over the studied time interval an increase in phytoclast opaque and non opaque abundance during the last glacial maximum interval suggests enhanced river supply driven by the increase in the hydrological cycle resulting from cold and humid climatic conditions the increase of amorphous organic matter from 16 437 cal yrs bp suggests the onset of anoxic bottomwater conditions that resulted of an increase in water depth together with the percentage increase of operculodinium centrocarpum and the fall in tuberculodinium vancampoae abundance this implies the postglacial development of warmer currents in summary our results better document the climatic and oceanographic changes that occurred in this area during and following the lgm

numerical modeling and field evidence of coastal overwash in southern new england from hurricane bob and implications for paleotempestology 1 in this paper we examine the use of coastal overwash modeling in conjunction with geological proxy techniques to provide a more comprehensive tool for paleotempestology southern new england which lies in the path of north tracking hurricanes has been a prime location for paleotempestological studies hurricane bob of 1991 is the most recent landfall in this region and has the most comprehensive data for model assessment and validation using the hurricane track central pressure and radius of maximum wind as input a collection of four interoperable model components simulates the meteorological conditions astronomical tides and storm surge ocean and coastal waves and the surf zone processes and runup onto dry land the computed surface pressure winds waves and water levels give very good agreement with data from weather stations moored buoys and tide gauges near the track and in the zone of maximum wind the validated wave conditions and storm water levels define the boundary conditions for coastal overwash modeling and the results show strong correlation with aerial photographs and sedimentary records at five sites near the landfall the results provide modern analogs for the interpretation of early hurricane landfalls in southern new england that lack an instrumental record reconstruction of paleohurricanes will require geological proxy data at multiple locations for the multivariate inverse analysis with uncertain paleotopography and storm characteristics

ascidian spicules of quaternary sediments from the lower slope of the campos basin brazil abstract piston core gl 77 was collected in the lower slope of the northern campos basin brazil and consists essentially of muds that have been deposited in turbiditic currents over the last 130 ka at least which corresponds to the upper pleistocene holocene interval the identified ascidian spicules belong to the didemnidae family and are represented by species micrascidites vulgaris bonetia brevis rigaudia multiradiata and monniotia fasciculata these species have irregular abundance and distribution with micrascidites vulgaris being the most common their occurrence is interpreted as resulting from transport to the depositional site in response to climate fluctuations glacial and interglacial periods the transport of ascidian spicules from a shallow water sea is supported by the presence of terrestrial organic matter mainly phytoclasts sporomorphs and microphytoplankton which were transported to the slope by the river systems the results found in this study show that the relative frequency distribution pattern of didemnid spicules is a useful tool for monitoring sediment transport in the slope

a hybrid eulerian lagrangian model for spectral wave evolution with application to bottom friction on the continental shelf abstract a hybrid eulerian lagrangian wave model is presented that solves the spectral energy balance equation for surface gravity waves in varying depth the energy of each spectral component is advected along lagrangian ray trajectories the source terms in the energy balance equation e g interactions between wave components and nonconservative processes are computed on a fixed eulerian grid and interpolated onto the ray trajectories the source terms are integrated in time along the rays this integration is performed in parallel over the entire model domain the main advantage of this new model named crest coupled rays with eulerian source terms is that refraction of waves by subgrid scale depth variations is evaluated accurately using precomputed rays and thus the model can be applied with relatively coarse source term grids to large coastal areas hindcasts of swell evolution across the north carolina continental shelf are presented for a source term restricted to energy dissipation in th

resonance and impact of the 2009 samoa tsunami around tutuila american samoa 1 the 2009 samoa tsunami resulted in severe damage and inundation at tutuila american samoa the disparity of the impact and the varying accounts of the tsunami along the coast remain one of the most intriguing aspects of the event we utilize a dispersive wave model to reconstruct the tsunami from the earthquake source for understanding of the wave dynamics around tutuila after validation with water level measurements a fast fourier transform of the computed surface elevation reveals coupled resonance oscillations between 3 and 18 min period over the insular slope and shelf as well as the fringing reefs the resonance which focuses energy according to shelf and embayment configurations provides an explanation of the runup data and eyewitness accounts and identifies the coastal communities prone to tsunami hazards

an evaluation of 14c age relationships between co occurring foraminifera alkenones and total organic carbon in continental margin sediments 1 radiocarbon age relationships between co occurring planktic foraminifera alkenones and total organic carbon in sediments from the continental margins of southern chile northwest africa and the south china sea were compared with published results from the namibian margin age relationships between the sediment components are site specific and relatively constant over time similar to the namibian slope where alkenones have been reported to be 1000 4500 years older than co occurring foraminifera alkenones were significantly similar to 1000 years older than co occurring foraminifera in the chilean margin sediments in contrast alkenones and foraminifera were of similar age within 2 sigma error or better in the nw african and south china sea sediments total organic matter and alkenone ages were similar off namibia age difference toc alkenones 200 700 years chile 100 450 years and nw africa 360 770 years suggesting minor contributions of preaged terrigenous material in the south china sea total organic carbon is significantly 2000 3000 years older owing to greater inputs of preaged terrigenous material age offsets between alkenones and planktic foraminifera are attributed to lateral advection of organic matter physical characteristics of the depositional setting such as seafloor morphology shelf width and sediment composition may control the age of co occurring sediment components in particular offsets between alkenones and foraminifera appear to be greatest in deposition centers in morphologic depressions aging of organic matter is promoted by transport age offsets are correlated with organic richness suggesting that formation of organic aggregates is a key process

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr