morphology of fore reef slopes and terraces takapoto atoll tuamotu archipelago french polynesia central pacific the tectonic sea level and coral growth control abstract a dataset of 41 bathymetric profiles detected by satelline imagery and echo sounding to a maximum depth of 38 m along the fore reef slopes of takapoto atoll tuamotu plateau french polynesia central pacific were qualitatively and quantitatively analyzed in order to identify the main geomorphological features in addition scuba diving investigations from a selected site resulted in defining coral composition and cover rate six distinct fore reef sectors were morphologically differentiated on the basis of seaward extension and slope gradient only the north end and a restricted area of the mid south east side extend seawards over an average distance of 150 m with a relatively low gradient 23 38 most of the outer slope areas are narrow 10 m high outer reef crest like reliefs 0 5 m 1 5 m high pinnacles 2 m 17 m high coral heads

multispectral bathymetry using a simple physically based algorithm a simple method for estimating water depths from multispectral imagery is described and is applied to several ikonos data sets for which independent measurements of the water depth are available the methodology is based on a physical model for the shallow water reflectance and is capable of correcting for at least some range of water quality and bottom reflectance variations corrections for sun glint effects are applied prior to the application of the bathymetry algorithm the accuracy of the depth algorithm is determined by comparison with ground truth measurements and comparisons between the observed and calculated radiances are presented for one case to illustrate how the algorithm corrects for water attenuation and or bottom reflectance variations

spatial distribution and the interdecadal change of leading modes of heat budget of the mixed layer in the tropical pacific and the association with enso using heat budget diagnosis of ocean mixed layer from the global ocean data assimilation system the spatial distribution of the leading modes of the heat budget was examined the analysis was for the tropical pacific in 1979 2013 and was based on combined empirical orthogonal function ceof analysis the interdecadal changes of the leading modes and their associations with el nino southern oscillation enso were also analyzed the first leading ceof mode ceof1 corresponds to the enso mature phase the contribution from the zonal advection was relatively small along the equator except the region near the pacific coast of central america the vertical entrainment and diffusion surface heat flux had pronounced maxima with positive negative values along the equatorial central and eastern pacific the meridional advection displayed a different spatial pattern with large positive values on both sides of the equator and smaller values along the equator the total meridional advection anomaly was mainly determined by advection of anomalous temperature by climatological current responsible for broadening of the enso ssta pattern meridionally the zonal advection varied almost simultaneously with the tendency of ocean temperature anomaly in the mixed layer the second leading ceof mode ceof2 included contribution to ssta tendency during the enso developing phase the distribution pattern and amplitude of the zonal advection in the eastern pacific in ceof2 was similar to but with opposite sign to that in ceof1 the amplitudes of the other dynamical and thermodynamical terms were smaller than that in ceof1 and spatial distributions displayed an opposite variation between the pacific coast of central america and central and eastern tropical pacific in ceof2 a comparison of two periods 1979 1999 and 2000 2013 suggested that coupling in the tropical pacific weakened at enso time scales and shifted to a relatively higher frequency regime from 2 to 4 years averaged in 1979 1999 to 1 5 3 years after 2000

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

hydrothermal metallogenesis at the wilkes fracture zone east pacific rise intersection abstract two hundred and eight sediment samples from 25 gravity cores obtained in and around the wilkes fracture zone on the east pacific rise have been analysed in bulk for mn fe ni co pb zn cu ba al si and caco3 downcore metal variations suggest that apart from the present hydrothermal event which is more intense on the crest of the rise and in the western part of the fracture zone in the past two hydrothermal events occurred the end of the first event occurred about 121 000 yrs b p and that of the second event at about 85 000 yrs b p both events are recognized throughout the study area a third hydrothermal event is traced only on the crest of the rise and occurred at about 16 000 yrs b p generally in the last 90 000 years the eastern part of the wilkes fracture zone appears to have become less active in contrast to the western flank which has become more active geochemical partition analysis carried out on selected cores shows that the hydroxylamine hcl soluble fe mn ni cu and zn decrease while the proportion of these metals associated with the hcl soluble fraction increases with depth in the sediments in addition there is an increase in the proportion of the hydroxylamine hcl insoluble residue with depth from these data it is inferred that diagenetic transformation of phases occurs within the buried sediments leading to the formation of stable iron oxides and iron smectite the element partition variations are most pronounced in the upper 40 cm of the sediments and are probably associated with oxidation reduction reactions in which mn fe mn fe oxides and organic material are involved reduction of fe mn oxides may lead to the release of mn cu and zn which are subsequently incorporated in the newly formed goethite and smectite the transformation of the metalliferous sediment constituents to more stable phases increases away from the crest of the rise because the environmental conditions for the formation of smectite become more favorable i e lower temperature older sediments greater availability of al si and mg and greater physical contact between fe oxy hydroxides and sio2 in the narrow basins

coastal engineering applications of high resolution lidar bathymetry abstract in 1994 the us army corps of engineers completed development of the scanning hydrographic operational airborne lidar survey shoals system a state of the art hydrographic survey instrument using lidar light detection and ranging technology and operating from a bell 212 helicopter shoals remotely collects accurate high resolution bathymetry at a rate of 8 km2 h a nominal depth and position measurement spacing of 4 m yields high density bottom coverage of coastal projects producing soundings from the above water beach or coastal structure to depths of 40 m since becoming fully operational shoals surveyed over 2000 km2 along the atlantic ocean pacific ocean gulf of mexico great lakes and caribbean sea survey projects varied from tidal inlets and navigation channels to beach nourishment and monitoring these projects quantify current coastal structure condition navigation channel alignments and morphologic changes over time in addition to monitoring coastal projects sediment transport can be estimated with accurate high resolution bathymetry bathymetry can be translated into sediment transport through a combination of the sediment continuity equation a surf zone energetics based longshore transport formula and bathymetric data this paper presents the shoals system describing both lidar technology and the survey system several shoals data sets are presented to show today s benefits of high resolution lidar bathymetry to the coastal engineering community finally ongoing research using these unique data sets is presented to show the future benefits of lidar bathymetry to the coastal field

determination of water depth with high resolution satellite imagery over variable bottom types a standard algorithm for determining depth in clear water from passive sensors exists but it requires tuning of five parameters and does not retrieve depths where the bottom has an extremely low albedo to address these issues we developed an empirical solution using a ratio of reflectances that has only two tunable parameters and can be applied to low albedo features the two algorithms the standard linear transform and the new ratio transform were compared through analysis of ikonos satellite imagery against lidar bathymetry the coefficients for the ratio algorithm were tuned manually to a few depths from a nautical chart yet performed as well as the linear algorithm tuned using multiple linear regression against the lidar both algorithms compensate for variable bottom type and albedo sand pavement algae coral and retrieve bathymetry in water depths of less than 10 15 m however the linear transform does not distinguish depths 15 m and is more subject to variability across the studied atolls the ratio transform can in clear water retrieve depths in 25 m of water and shows greater stability between different areas it also performs slightly better in scattering turbidity than the linear transform the ratio algorithm is somewhat noisier and cannot always adequately resolve fine morphology structures smaller than 4 5 pixels in water depths 15 20 m in general the ratio transform is more robust than the linear transform

mixed siliciclastic carbonate evaporite sedimentation in an arid eolian landscape the khor al adaid tide dominated coastal embayment qatar abstract the khor al adaid embayment of southern qatar represents a unique shallow water mixed siliciclastic carbonate coastal depositional system that developed in a hyper arid climatic setting over the past 6000 years the embayment which was formed during the flandrian transgression as a result of flooding across a partially fault controlled incised fluvial drainage is supplied by quartz rich sands delivered by wind blown dunes migrating southward across the surface of qatar these offshore migrating eolian derived sediments are being redistributed by tidal currents in an otherwise low energy coastal zone where in situ formation of carbonate mud and a low diversity skeletal assemblage is ongoing within salinity restricted environments three depositional sectors are delineated 1 an energetic linear fault controlled entrance channel into which the eolian dunes spill directly 2 a relatively deep up to 20 m outer lagoon interpreted to represent a flooded karst collapse structure and 3 a sprawling low energy shallow physical oceanographic modeling integrating multi seasonal current meter and tidal gage measurements demonstrates tidal current flow velocities are relatively high in both the entrance channel and at the constricted entrance to the inner lagoon associated flow expansion into less confined areas results in deposition of the eolian derived sands as flood tidal deltas one in the outer and two in the inner lagoon a weakly developed ebb tidal delta occurs where the entrance channel debouches into the arabian gulf flood tide dominance is also apparent in entrance channel deposits where sand accumulates in seaward terminating ebb barbs along the margins of the flood dominant thalweg such flood tide dominance of the thalweg is unusual and likely reflects the absence of river discharge evidence of significant inverse estuarine circulation seaward flow of a brine along the embayment floor is mostly absent in spite of the landward increase of salinity where concentrations reach more than double normal seawater salinity in the inner lagoon modeling results show that seaward flowing brines formed in the inner lagoon are trapped in the relatively deep outer lagoon and that mixing by tidal currents in the energetic entrance channel precludes the formation of vertical density gradients there because siliciclastic mud is essentially absent and most of the sediment forming the deltas consists of sand upper intertidal deltaic deposits that would normally consist of mud are absent resulting in the flood tide deltas having a pronounced lobate geometry similar to that of fluvial deltas formed predominantly of sand away from tidal deltas low energy lagoons are floored by carbonate mud of local production with minor gypsum precipitating in the inner lagoon wind generated waves only locally influence sedimentation forming complex nearshore bars along some lagoonal shorelines the overall landward increase in salinity is accompanied by a decrease in the diversity of benthic fauna and their skeletal remains a fairly diverse faunal assemblage is observed in the entrance channel near the arabian gulf including colonial corals whereas the inner lagoon assemblage is dominated gastropods belonging to pirenella cingulata the remnants of large eolian dunes are preserved in the low energy setting of the inner lagoon segmenting the waterbody and locally increasing restriction the sedimentology of the arid zone coastal khor al adaid embayment may serve as an analogue for environmental settings that were perhaps more commonplace in arid zones of flooded continents during greenhouse times

enso dynamics and diversity resulting from the recharge oscillator interacting with the slab ocean el nino southern oscillation enso is the leading mode of interannual global climate variability which in its essence is often described by the equatorial dynamics of the recharge oscillator with a fixed pattern here we explore the idea that enso can be simulated in a model with a fixed pattern of sea surface temperature variability following the recharge oscillator mechanism which interacts with the thermodynamic red noise of a slab ocean this model is capable of simulating the leading modes of sea surface temperature variability in the tropical pacific in good agreement with the observations and most coupled general circulation models enso dynamics amplitude seasonality the structure of the leading patterns its meridional extension its variations in an eastern and central pacific pattern and associated positive feedbacks are all influenced and simulated well by including the interaction of recharge oscillator and the thermodynamic coupling to the slab ocean model we further point out that much of the enso diversity in the spatial structure is a reflection of this interaction however it also has to be noted that some equatorial dynamics are missing in this model and in coupled general circulation models that are important for the enso diversity

satellite derived bathymetry in optically complex waters using a model inversion approach and sentinel 2 data abstract this study presents an assessment of a model inversion approach to derive shallow water bathymetry in optically complex waters with the aim of both understanding localised capability and contributing to the global evaluation of sentinel 2 for coastal monitoring a dataset of 12 sentinel 2 msi images in three different study areas along the irish coast has been analysed before the application of the bathymetric model two atmospheric correction procedures were tested deep water correction dwc and case 2 regional coastal color c2rcc processor dwc outperformed c2rcc in the majority of the satellite images showing more consistent results using dwc for atmospheric correction before the application of the bathymetric model the lowest average rmse was found in dublin bay rmse 1 60 bias 0 51 followed by mulroy bay rmse 1 66 bias 1 30 while brandon bay showed the highest average error rmse 2 43 bias 1 86 however when the optimal imagery selection was considered depth estimations with a bias less than 0 1 m and a spread of 1 40 m were achieved up to 10 m these results were comparable to those achieved by empirical tuning methods despite not relying on any in situ depth data this conclusion is of particular relevance as model inversion approaches might allow future modifications in crucial parts of the processing chain leading to improved results atmospheric correction the selection of optimal images e g low turbidity the definition of suitably limited ranges for the per pixel occurrence of optical constituents phytoplankton cdom backscatter and seabed reflectances in combination with the understanding of the specifics characteristics at each particular site were critical steps in the derivation of satellite bathymetry

modeling wave effects on storm surge and coastal inundation abstract we present a parametric study of surface wave effects on storm surge and coastal inundation hurricane wind forcing terms atmosphere pressure gradient terms and radiation open boundary conditions are implemented into an existing quasi 3d nearshore model nearcom tvd which uses a shock capturing tvd scheme and can better simulate the wetting drying process during inundation than a conventional finite difference model systematic numerical experiments are carried out in an idealized continental shelf beach land system to identify the role of waves in modeling storm surge and inundation under different storm characteristics four storm parameters including storm intensity storm size translation speed and incident angle are investigated modeling results reveal that the presence of waves can increase the maximum storm surge heights significantly through wave setup and the contribution of waves varies considerably depending on the storm characteristics in addition to direct wave forcing the wave enhanced bottom stress in the surfzone also promotes higher wave setup and hence higher surge heights waves also have a major influence on the maximum inland inundation distance however we find that waves do not always favor more inundation as expected for storms traveling at very slow translation speeds or nearly parallel to the coast waves surprisingly exert a negative effect on the maximum inundation distance we argue that wave enhanced bottom stress combined with longer forcing duration in such storms counteract the positive effect of wave setup and thus less inundation is predicted in wave current coupled simulations our results highlight the necessity of fully incorporating wave effects in storm surge and inundation modeling

oceanic ridge crest processes oceanic ridge crest processes constitute a vigorous frontier of multidisciplinary research with global ramifications in the earth atmospheric and biologic sciences this deep ocean frontier is gradually opening in response to investigations which are elucidating the role of these processes in the lithosphere hydrosphere atmosphere and biosphere and the application of advanced instrumental and interpretive techniques which are increasing the quality and quantity of data these techniques include crustal drilling with borehole logging deep sea drilling project reports high resolution bathymetry sea beam etc side scan sonar seamarc i and ii gloria etc imagery with video and photography multichannel seismics determination of water column properties ctd with rosette sampler etc and submersible applications

chemistry and origin of zeolites in sandstones at dsdp sites 445 and 446 daito ridge and basin province northwest pacific abstract andesitic volcaniclastic sandstones of middle eocene age recovered from dsdp sites 445 and 446 a back arc basin contain clinoptilolite heulandite and analcite as a pore filling cement clinoptilolite and heulandite at sites 445 and 446 contain different chemical composition from other deep sea clinoptilolites and heulandites the dominant cation of both clinoptilolite and heulandite is na ion activity in pore water was greater at the time of their formation volcanic glass has acted as a precursor for both clinoptilolite and heulandite at sites 445 and 446 biogenic silica is also suggested as a precursor high na ion activity in pore water also helped to transform clinoptilolite and heulandite to analcite downhole the necessary na ions for this clinoptilolite heulandite and analcite at sites 445 and 446 might have been provided by hydrothermal circulation of seawater through more permeable sandstones deposited during early stages of back arc basin rifting

reef development on a remote coral atoll before and after coral bleaching a geospatial assessment abstract coral reefs are consolidated calcium carbonate caco3 platforms built over hundreds of thousands of years by calcifying organisms including corals encrusting algae and invertebrates the geomorphic integrity of coral reefs depends on the carbonate budget which quantifies the net gain or loss of calcium carbonate given additive and removal processes here we construct three carbonate budgets for cocos keeling atoll in the east indian ocean from seafloor records of carbonate producers before during and after a coral bleaching event 2015 2017 a satellite image is used to upscale 367 in situ observations across the complete atoll are 225 km2 growth of calcifying encrusters is monitored on settlement plates from 2015 to 2016 while bioerosion is quantified from parrotfish surveys and macroborer analysis of rubble the highest rates of production were on the outer atoll forereef and in the northern lagoon 1 5 and 1 61 kg m 2 yr 1 respectively the forereef produced an order of magnitude more calcium carbonate approximately 13 114 t per year in 2015 than the other zones due to a high coverage of live branching coral ca 50 combined with a large forereef area 123 km2 the greatest rates of removal occurred on the shallow forereef 1 67 kg m 2 yr 1 driven largely by bolbometopon muricatum parrotfish bioerosion resulting in a net loss of carbonate in 2017 0 15 kg m 2 yr 1 accounting for parrotfish bioerosion the net atoll budget was estimated to be 5976 t of calcium carbonate in 2015 which reduced by 46 over the coral bleaching period to 3200 t in 2017 compared to other indian ocean reefs this is a relatively minor impact of coral bleaching on the carbonate budget at cocos keeling atoll

adaptive bathymetry estimation for shallow coastal waters using planet dove satellites abstract accurate bathymetric mapping of shallow waters above 15 m is essential for a wide range of scientific research government transport and industry globally satellite based bathymetry estimation approaches offer an alternative to traditional shipborne measurements especially given advancements in their spatial and temporal resolution of satellite imagery including the new planet dove constellation of 150 satellites providing daily coastal coverage dove satellites provide abundant cloud free images even over cloudy tropical coastal environment offering an opportunity to generate frequent bathymetry maps at high spatial resolution 4 m we developed a new adaptive bathymetry estimation algorithm for planet dove and similar satellites the algorithm adaptively tunes a depth estimator according to water column attenuation conditions the algorithm was tested at five diverse reef sites globally lighthouse reef belize saona island dominican republic st croix u s virgin islands heron island australia hawaii island u s using 31 satellite images from six dove satellites derived water depth was validated rmse 1 22 to 1 86 m with field measured sampling points 61 025 ranging in depth from 1 to 15 m algorithm performance was best at depths of 4 10 m this new adaptive algorithm can be effectively applied to derive high spatial resolution bathymetric maps from planet dove satellite imagery across a wide range of conditions

multi model representation of the north atlantic oscillation in the 20th and 21st centuries 1 ten coupled ocean atmosphere general circulation models cgcm are used to reproduce nao mean sea level pressure and 2 meter air temperature fields highly correlated to the north atlantic oscillation index naoi during a control period from 1961 1990 three enhanced co2 perturbation scenarios are compared to the control for 2070 2099 using pattern correlations and normalized root mean square errors between perturbation and control periods it is found that models can successfully reproduce observed nao sea level pressure and temperature anomaly fields model control slp anomaly fields however more closely resemble the arctic oscillation than the expected nao slp distribution due to an expansion of the north atlantic low pressure area analysis for the period 2070 2099 under the 3 enhanced co2 scenarios shows intensification of the naoi due to co2 forcing but with a weaker temporal trend relative to the control period

detecting trend and seasonal changes in bathymetry derived from hico imagery a case study of shark bay western australia abstract the hyperspectral imager for the coastal ocean hico aboard the international space station has offered for the first time a dedicated space borne hyperspectral sensor specifically designed for remote sensing of the coastal environment however several processing steps are required to convert calibrated top of atmosphere radiances to the desired geophysical parameter s these steps add various amounts of uncertainty that can cumulatively render the geophysical parameter imprecise and potentially unusable if the objective is to analyze trends and or seasonal variability this research presented here has focused on 1 atmospheric correction of hico imagery 2 retrieval of bathymetry using an improved implementation of a shallow water inversion algorithm 3 propagation of uncertainty due to environmental noise through the bathymetry retrieval process 4 issues relating to consistent geo location of hico imagery necessary for time series analysis and 5 tide height corrections of the retrieved bathymetric dataset the underlying question of whether a temporal change in depth is detectable above uncertainty is also addressed to this end nine hico images spanning november 2011 to august 2012 over the shark bay world heritage area western australia were examined the results presented indicate that precision of the bathymetric retrievals is dependent on the shallow water inversion algorithm used within this study an average of 70 of pixels for the entire hico derived bathymetry dataset achieved a relative uncertainty of less than 20 a per pixel t test analysis between derived bathymetry images at successive timestamps revealed observable changes in depth to as low as 0 4 m however the present geolocation accuracy of hico is relatively poor and needs further improvements before extensive time series analysis can be performed

an evaluation of the cmip3 and cmip5 simulations in their skill of simulating the spatial structure of sst variability the natural sea surface temperature sst variability in the global oceans is evaluated in simulations of the climate model intercomparison project phase 3 cmip3 and cmip5 models in this evaluation we examine how well the spatial structure of the sst variability matches between the observations and simulations on the basis of their leading empirical orthogonal functions modes here we focus on the high pass filter monthly mean time scales and the longer 5 years running mean time scales we will compare the models and observations against simple null hypotheses such as isotropic diffusion red noise or a slab ocean model to illustrate the models skill in simulating realistic patterns of variability some models show good skill in simulating the observed spatial structure of the sst variability in the tropical domains and less so in the extra tropical domains however most models show substantial deviations from the observations and from each other in most domains and particularly in the north atlantic and southern ocean on the longer 5 years running mean time scale in many cases the simple spatial red noise null hypothesis is closer to the observed structure than most models despite the fact that the observed sst variability shows significant deviations from this simple spatial red noise null hypothesis the cmip models tend to largely overestimate the effective spatial number degrees of freedom and simulate too strongly localized patterns of sst variability at the wrong locations with structures that are different from the observed however the cmip5 ensemble shows some improvement over the cmip3 ensemble mostly in the tropical domains further the spatial structure of the sst modes of the cmip3 and cmip5 super ensemble is more realistic than any single model if the relative explained variances of these modes are scaled by the observed eigenvalues

combining optical and acoustic data to enhance the detection of caribbean forereef habitats maps of coral reef habitats are fundamental tools for reef management and high map accuracy is desirable to support appropriate decisions such as the stratification of marine reserves by habitat class while satelite sensors have been used to map different reef communities the accuracy of these maps tends to be low overall accuracy 50 and optical airborne methods with high spectral resolution have to date been the most effective if expensive means of achieving higher accuracy a potential means of compensating for the low spectral and radiometric resolution of optical satellite data which is a major cause of its poor performance is to combine satellite data with acoustic remote sensing this study quantified the benefit of the synergy between optical satellite data ikonos and acoustic roxann sensors the addition of acoustic data provided three new data axes for discriminating habitats seabed roughness e1 reef depth z and the depth correction of satellite spectral data to uniform depth seabed hardness e2 was not an informative channel in our study the use of z to conduct the water column correction of the optical bands to uniform depth is a potential improvement over applying the depth invariant index approach to optical data in the absence of ancillary information on depth habitat maps of the forereef of glovers atoll belize central america were created using k means unsupervised classification on eleven different treatment images constructed from various combinations of optical and acoustic data layers the maximum benefit of data synergy was achieved by depth correcting the optical bands the accuracy of maps based on the depth invariant optical index was not enhanced when e1 e2 or z were added as separate layers but was enhanced when these three acoustic measures were added in concert data synergy can improve the accuracy of habitat maps and the availability of both data sets allows practitioners to take advantage of each techniques additional strengths such as providing synoptic continuous imagery for education and general management planning in the case of optical imagery and maps of reef rugosity in the case of acoustic data c 2010 elsevier inc all rights reserved

topographic relief and sediment thickness their effects on the thermal evolution of the oceanic crust we compiled a suite of 490 heat flow measurements from the pacific ocean in areas with less than 85 m of sediment heat flow patterns at different basement ages vary with topographic relief areas with reliefs 300 meters are conductively blanketed at 70 90 m y and convect out to 90 110 m y

2500 year paleotempestological record of intense storms for the northern gulf of mexico united states abstract the northern gulf of mexico has been devastated by recent intense storms camille 1969 and katrina 2005 are two notable hurricanes that made landfall in nearly the same location in mississippi fully understanding the risks and processes associated with hurricane impacts are impeded by a short and fragmented instrumental record however paleotempestology has the potential to employ modern analogues from intense storms in this region to extend the hurricane record beyond pre observational time existing empirically based models can back calculate surge heights over coastal systems as a function of transport distance particle settling velocity and gravitational acceleration we collected sediment cores in a pond 3 and adjacent beach 1 in hancock county mississippi grain size loss on ignition and microfossil analyses were conducted on cores in the context of a bayesian statistical age model using 137cs and 14c dating using hurricane camille to calibrate the archive similar coarse grained deposits were identified and inverse sediment transport models calculated paleosurge intensities similar in magnitude to camille over the 2500 yr record our multi millennial annual average landfall probability 0 48 closely matches previously published studies from the gulf of mexico indicating that intense hurricanes have not varied over these timescales over centennial timescales active intervals occurred between 900 to 600 and 2200 to 1900 yr bp with relative quiescence between 1900 to 900 yr bp comparisons with other published sites support the notion that southerly shifts in the loop current may be responsible for the decline in activity around 600 yr bp

evaluation of various satellite sensors for waterline extraction in a coral reef environment majuro atoll marshall islands abstract the ability of five satellite sensor bands ikonos band 4 terra aster bands 3 and 4 and landsat etm bands 4 and 5 was examined to extract the waterline at coral reef coasts majuro atoll marshall islands using different wavelength regions near infrared nir and shortwave infrared swir and different spatial resolutions 4 15 and 30 m after performing georeferencing and normalization of the images density slicing was used to extract the waterline comparisons of extracted waterline positions with ground level data for eight transects and global positioning system gps tracks of the island shorelines showed that nir bands were superior to swir bands because of the characteristics of the coral reef coasts including a lack of foam and suspended sediments which can affect the nir wavelength region if present and the presence of remnant water on reef flats during low tide which can affect the swir wavelength region a linear relationship was found between the estimation errors of waterline positions and the spatial resolutions of the nir sensors analysis on estimation errors and image costs showed that terra aster band 3 was the most cost effective sensor for extracting waterlines with reasonable accuracy the results serve as general guidelines for using satellite derived data to estimate intertidal topography and detect and monitor shorelines in coral reef environments

a bathymetry mapping approach combining log ratio and semianalytical models using four band multispectral imagery without ground data four band multispectral remote sensing imagery is widely used for a variety of purposes and has a long historical data record however most of the existing bathymetry inversion methods are either unable to determine the optimal solution through theoretical or semianalytical models due to the limited number of bands or their application is limited by the difficulty in obtaining in situ data in this article a log ratio model and a semianalytical model are combined to develop a new shallow water depth inversion method l s model using four band multispectral remote sensing images without the need for supporting truth data a case study was conducted for ganquan island in the south china sea using four band multispectral imagery from the geoeye 1 worldview 2 four bands selected sentinel 2 four bands selected and gaofen 1 satellites a sound range of 30 m was achieved when compared to lidar measured water depth data geoeye 1 worldview 2 sentinel 2 and gaofen 1 data have root mean square errors rmses of 1 33 1 97 m in addition compared with the results of the log ratio model trained using 200 lidar based depth readings the l s model results obtained for the four satellite types are similar in the rmse these results show that the l s model can achieve results that are close to those of the log ratio model without the need for external inputs this provides a feasible new method for bathymetry inversion in areas without truth data using only four band imagery

mass transfer and problems of secondary porosity creation in deeply buried hydrocarbon reservoirs abstract secondary porosity created by the post depositional leaching of detrital grains and cements can be of great economic importance the term secondary porosity is only descriptive and does not give any information on whether the porosity of the rock has been enhanced in reality there are two end member volumetric outcomes to the leaching process firstly the mineral can be completely dissolved and its components transported out of the system in such an instance the porosity of the rock will be enhanced secondly it is possible that a mineral will decompose and by product minerals will be precipitated which will occupy approximately the same volume as the original mineral the latter case is more likely where the pore waters are close to equilibrium with the majority of the minerals of the rock this will occur at elevated temperatures and or where the pore waters have been in contact with the rock for a long time these conditions are commonly met during intermediate to deep burial many metastable minerals such as high temperature feldspars probably decompose in this way a consequence of the decomposition of such metastable minerals is that primary porosity will be swapped for secondary and that older and more deeply buried rocks will contain a higher proportion of secondary porosity the mass transport equation may be used to examine the physico chemical environment where enhanced porosities most likely occur during leaching by using a simple non equilibrium mass transport model based on the silica system it is possible to demonstrate the relative importance of flow rate reaction rates specific surfaces and temperature in controlling the areal extent of leaching wide leaching zones are related to high flow rates which in turn promote a high throughput of undersaturated fluid and dispersion leaching over a wide area is also favoured by low reaction rates which will occur at low temperatures although it is true to say that less of a given silicate mineral can be dissolved by an undersaturated pore water at low temperature than at high temperature it is probable that pore fluids from deeply buried sediments are more likely to be close to equilibrium with a given mineral than for instance meteoric water thus the most likely environment for the production of widespread enhanced porosity is in the shallow subsurface the lower flow rates and higher temperatures that are encountered during deep burial diagenesis will result in far narrower more intense leaching zones as a result providing sufficient reactive mineral is present any undersaturated pore water will approach equilibrium in a short distance in order to transport undersaturated pore waters appreciable distances in the deep subsurface it is necessary to minimize their interaction with the host rock this could occur if the pore fluid were to move through a fracture system where it would interact with a far smaller surface area of reactive mineral than if it moved through the pore network

geographically adaptive inversion model for improving bathymetric retrieval from satellite multispectral imagery optical remote sensing imagery offers a cost effective alternative to echo sounding and bathymetric light detection and ranging surveys for deriving high density bottom depth estimates for coastal and inland water bodies the common practice of previous studies has been to calibrate a single global bathymetric inversion model for an entire image scene the performance of conventional global models is limited when the bottom type and water quality vary spatially within the scene to address the inadequacy of the conventional global models this paper presents a geographically adaptive inversion model to better estimate bottom depth although the general mathematical form of the geographically adaptive model is the same model parameters are optimally determined within a geographical region or a local area in contrast to the entire scene in the global inversion model by using high resolution ikonos and moderate resolution landsat satellite images we demonstrated that regionally and locally calibrated inversion models can effectively address the problems introduced by spatial heterogeneity in water quality and bottom type and provide significantly improved bathymetric estimates for more complex coastal waters

high resolution depth and coastline over major atolls of south china sea from satellite altimetry and imagery abstract current bathymetric models for the south china sea scs are largely based on predicted depths from gravity and sparse single beam echo sounder measurements such models lack high resolution coastlines and shallow water bottom features around atolls and islands this study refines the gravity field of the scs using sea surface heights from measurements of satellite altimeter geosat gm ers 1 gm jason 1 gm and the original cryosat 2 a new one minute gravity anomaly grid is determined the modeled gravity anomalies show a 6 mgal rms discrepancy with shipborne measurements in shallow waters an altimeter only bathymetric model is derived from the new gravity grid by the gravity geological method that uses the latest global and regional models of the ocean depth and marine gravity as a priori knowledge the new model outperforms current scs bathymetric models and is accurate to 100 m based on comparison with multi beam depth measurements optical images from ikonos 2 quickbird 2 geoeye 1 worldview 1 2 and 3 are rectified and digitized to derive the zero coastline and 20 m depth contours reef lines around 44 atolls which are integrated with the altimeter only depths giving significantly improved accuracies and spatial resolutions in modeled depths the improvement percentages of coastlines by the satellite imagery range from 50 to 97 at 41 of the 44 atolls we establish a webpage for free access to the optical and depth images and the depth and gravity grids we will continue to update satellite images altimeter derived gravity grids and bathymetric models over major atolls of the scs

topographic forcing of supercritical convection in a porous medium such as the oceanic crust abstract we have performed laboratory experiments using a hele shaw cell to model a saturated porous layer with various sinusoidal upper boundaries our intent was to determine the range of conditions over which boundary topography can control the pattern of thermal convection within a porous layer and thereby take the first step toward understanding why heat flow seems correlated with hypsography in many areas of the ocean floor these experiments indicate that above the critical rayleigh number topography does not control the convection pattern except when the topographic wavelength is comparable to the depth of water penetration scaled to the depth of the layer the convective wavenumbers are restricted to values between 2 5 and 4 8 a range which brackets the natural wavenumber for convection in a porous slab with planar isothermal impermeable boundaries topographies within this range control the circulation pattern perfectly with downwelling under valleys and upwelling aligned with topographic highs other topographies do not force the pattern although in some cases the convection wavenumber may be a harmonic of the topographic wavenumber unforced circulation cells wander and vary in size because they are not locked to the topography for these experiments we employed eight different topographies with non dimensional wavenumbers between 1 43 and 8 17 and we studied the flow at rayleigh numbers between zero and five times the critical rayleigh number the amplitude of each topography tapered linearly over a factor of three to six from one end of the apparatus to the other and the mean topographic amplitude was 0 05 times the depth of the layer under these conditions amplitude has only a minor effect on the structural form and vigor of supercritical convection our results may apply to submarine geothermal systems sealed by a thin layer of impermeable sediment draped over the basement topography in this case the convection wavelength as measured perhaps by the spatial periodicity of conductive heat flow may be a good measure of the depth to which water penetrates the crust where the circulation correlates with the bottom topography it may be because the topographic wavelength is comparable to the depth to which water penetrates the porous crust

a link between reduced barents kara sea ice and cold winter extremes over northern continents the recent overall northern hemisphere warming was accompanied by several severe northern continental winters as for example extremely cold winter 2005 2006 in europe and northern asia here we show that anomalous decrease of wintertime sea ice concentration in the barents kara b k seas could bring about extreme cold events like winter 2005 2006 our simulations with the echam5 general circulation model demonstrate that lower troposphere heating over the b k seas in the eastern arctic caused by the sea ice reduction may result in strong anti cyclonic anomaly over the polar ocean and anomalous easterly advection over northern continents this causes a continental scale winter cooling reaching 1 5 c with more than three times increased probability of cold winter extremes over large areas including europe our results imply that several recent severe winters do not conflict the global warming picture but rather supplement it being in qualitative agreement with the simulated large scale atmospheric circulation realignment furthermore our results suggest that high latitude atmospheric circulation response to the b k sea ice decrease is highly nonlinear and characterized by transition from anomalous cyclonic circulation to anticyclonic one and then again back to cyclonic type of circulation as the b k sea ice concentration gradually reduces from 100 to ice free conditions we present a conceptual model which may explain the nonlinear local atmospheric response in the b k seas region by counter play between convection over the surface heat source and baroclinic effect due to modified temperature gradients in the vicinity of the heating area

field measurements of intertidal bar evolution on a high energy beach system nearshore bars play a pivotal role in coastal behaviour helping to protect and restore beach systems particularly in post storm conditions examination of bar behaviour under various forcing conditions is important to help understand the short to medium term evolution of sandy beach systems this study carried out over a nine week period examines the behaviour of three intertidal bars along a high energy sandy beach system in northwest ireland using high frequency topographic surveys and detailed nearshore hydrodynamic modelling results show that in general there was onshore migration for all the bars during the study period despite the variability observed between bars which was driven mostly by wave dominated processes under the prevailing conditions migration rates of up to 1 83 m day 1 and as low as 0 07 m day 1 were observed during higher wave energy events the migration rates of the bars decelerated in their onshore route however under lower wave energy conditions they quickly accelerated maintaining their shoreward migration direction tidal influence appears to be subordinate in these conditions being restricted to moderating the localized wave energy at low tides and in maintaining runnel configurations providing accommodation space for advancing slip faces the study highlights the intricate behavioural patterns of intertidal bar behaviour along a high energy sandy coastline and provides new insights into the relative importance of wave and tidal forcing on bar behaviour over a relatively short time period copyright 2016 john wiley sons ltd

misr based passive optical bathymetry from orbit with few cm level of accuracy on the salar de uyuni bolivia abstract we demonstrate that under ideal circumstances passive optical measurements can yield surface water depth estimates with an accuracy of a few centimeters our target area is the salar de uyuni in bolivia it is a large active salt flat or playa which is maintained as an almost perfectly level and highly reflective surface by annual flooding to a mean depth of 30 50 cm we use misr data to estimate spatial and temporal variations in water depth during the waning portion of the 2001 flooding cycle we use a single icesat laser altimetry profile to calibrate our water depth model though the salt surface is probably the smoothest surface of its size on earth with less that 30 cm rms height variations over an area of nearly 104 km2 it is not completely featureless topography there includes a peripheral depression or moat around the edge of the salt and several sets of prominent parallel ridges with 5 km wavelength and 30 cm amplitude the process by which these features form is still not well characterized

simulation based investigation of the generality of lyzenga s multispectral bathymetry formula in case 1 coral reef water abstract lyzenga s multispectral bathymetry formula has attracted considerable interest due to its simplicity however there has been little discussion of the effect that variation in optical conditions and bottom types which commonly appears in coral reef environments has on this formula s results the present paper evaluates lyzenga s multispectral bathymetry formula for a variety of optical conditions and bottom types a noiseless dataset of above water remote sensing reflectance from worldview 2 images over case 1 shallow coral reef water is simulated using a radiative transfer model the simulation based assessment shows that lyzenga s formula performs robustly with adequate generality and good accuracy under a range of conditions as expected the influence of bottom type on depth estimation accuracy is far greater than the influence of other optical parameters i e chlorophyll a concentration and solar zenith angle further based on the simulation dataset lyzenga s formula estimates depth when the bottom type is unknown almost as accurately as when the bottom type is known this study provides a better understanding of lyzenga s multispectral bathymetry formula under various optical conditions and bottom types

diffuse reflectance of oceanic shallow waters influence of water depth and bottom albedo we used simplifying assumptions to derive analytical formulae expressing the reflectance of shallow waters as a function of observation depth and of bottom depth and albedo these formulae also involve two apparent optical properties of the water body a mean diffise attenuation coefficient and a hypothetical reflectance which would be observed if the bottom was infinitely deep the validity of these approximate formulae was tested by comparing their outputs with accurate solutions of the radiative transfer obtained under the same boundary conditions by monte carlo simulations these approximations were also checked by comparing the reflectance spectra for varying bottom depths and compositions determined in coastal lagoons with those predicted by the formulae these predictions were based on separate determinations of the spectral albedos of typical materials covering the floor such as coral sand and various green or brown algae the simple analytical expressions are accurate enough for most practical applications and also allow quantitative discussion of the limitations of remote sensing techniques for bottom recognition and bathymetry as early as 1944 duntley used a spectrograph mounted in a glass bottomed boat or flown in an airplane to analyze radiances emerging from the ocean and shallow waters he evidenced the influence of the water depth on the spectral composition of the upward flux duntley 1963 using a monte carlo technique plass and kattawar 1972 calculated the radiative field in the atmosphere cean system and in particular examined the dependence of the upward flux on the albedo of the ocean floor gordon and brown 1974 studied the diffuse reflectance of a shallow ocean using monte carlo simulations and a probabilistic approach gordon and brown provided an analysis based on photon history of the light field as modified by the presence of a reflecting bottom in addition ackleson and klemas 1986 developed a two flow model that simulated the light field within a canopy of bottom adhering plants a single scattering approximation for irradiance reflectance was also

retrieving shallow stream bathymetry from uav assisted rgb imagery using a geospatial regression method abstract bathymetric mapping is a prerequisite procedure to conduct assessments of water quality habitat and environmental flow for riverine ecosystems using hydraulic modelling this study evaluates the capability of a geographically weighted regression gwr model which can capture a spatially heterogeneous relationship between inputs and an output to retrieve bathymetry of a shallow stream of which water depth is less than about 1 m from simple rgb imagery a field experiment was performed for measuring water depth and simultaneously for acquiring remotely sensed data with rgb digital numbers dn using a digital camera mounted on an unmanned aerial vehicle uav a 2d shallow water model which was validated by comparison with the field surveyed data was used to simulate the water depth of unmeasured regions band ratios of ln dng dnr was selected as an optimal spectral input of bathymetric inversion models through the principal component analysis pca results showed that global inversion models based on multiple linear regression mlr and artificial neural network ann resulted in large discrepancy between estimation and observation due to the spatially varying response of the pca selected band ratio to water depth over the experimental channel in contrast the gwr model successfully alleviated the biases of the conventional models as r2 increased to 0 85 from 0 60 by accurately modelling the effect of spatial heterogeneity which arose from variable bottom types attributed to submerged vegetation on the remote sensing radiance water depth relationship

semi diurnal tidal ellipse variability in a region of freshwater influence 1 new insight into a key process instrumental in the onset of stratification in tidally driven systems is presented for the first time using long term field observations from the liverpool bay region of freshwater influence rofi tidal ellipses respond to changes in stratification becoming more circular with greater vertical structure and reveal variability in response to tidal straining an inflection point that occurs before the maximum vertical density difference at the time of maximum positive bed surface cross shore shear is identified as the crucial point where the water column abruptly decouples the surface and bed layers then rotate in clockwise and anti clockwise directions respectively the maximum vertical stratification is observed when the maximum negative bed surface along shore shear is reached decoupling to a two layer system is therefore not the smooth progression predicted using turbulence closure models but rather a very sudden switch highlighting the importance of the role of reynolds stresses

high resolution topobathymetry using a pleiades 1 triplet moorea island in 3d abstract worldwide the coastal land sea interface is increasingly subject to natural and anthropogenic hazards monitoring this crucial interface may be addressed with satellite imagery as a cost efficient mapping solution topography and bathymetry defining the structural complexity of the coast are commonly studied separately given specific thematic and methodological contexts yet many science questions and societal challenges require an integrated approach e g coastal inundation in such cases triplet multispectral imagery represents an affordable solution based on a single satellite product here we examine how pleiades 1 triplet imagery may be used to retrieve a seamless and accurate topobathymetry digital surface model dsm from 20 to 1207 m over an entire socio ecologically complex island moorea french polynesia creation of the topography dsms was based on stereo and tri stereo photogrammetry and the bathymetry dsms relied on quasi nadiral multispectral data subject to light water interaction modelling results were compared with over 3 9 million airborne lidar topobathymetry measurements to quantify how the spatio spectral mode the third imagery and the level of radiometric correction act on two and three dimensional accuracy horizontal accuracy of the tri stereo panchromatic dataset ermse 4 22 and nrmse 7 59 m was better than the multispectral ermse 5 06 and nrmse 7 51 m dataset topography point cloud density increased by a factor of three in the tri stereo panchromatic 9 11 points m2 or multispectral 0 23 points m2 datasets topography vertical accuracy enhanced with tri stereo level 1 radiometric correction rmse 7 40 m for panchromatic and with stereo level 1 2 radiometric correction rmse 7 77 7 77 m as well as tri stereo without radiometric correction rmse 7 85 m for multispectral datasets bathymetry vertical accuracy improved with level 2 atmospheric correction rmse 0 83 m topobathymetry dsm derived from this optimized method has a wide spectrum of applications along coastal margins

constraints on water transport and alteration in the oceanic crust from the isotopic composition of pore water the oxygen isotopic compositions of pore fluids from sediments of older oceanic crust commonly decrease with depth increases in calcium ion concentrations always accompany the 18o 16o decreases these changes are attributed principally to the alteration of basalts or alteration of volcanic ash in the sediments oxygen isotope material balance calculations suggest that 5 20 of the upper kilometer of basalt is altered at the time of subduction of the oceanic crust this corresponds to a flux of 18o into the oceanic crust of 2 3 1015 moles per million years evaluation of the oxygen and hydrogen isotope data from the pore fluids also suggests that the principal process of mass transfer in the sediments of older oceanic crust is diffusion convection of water in the basalts of the oceanic crust appears to continue until subduction

stromatolite provinces of hamelin pool physiographic controls on stromatolites and associated lithofacies recent studies recognized distinct stromatolite provinces in hamelin pool western australia each with morphologically distinct stromatolite structures paired with characteristic shelf physiography in the present paper we couple detailed lithofacies mapping with hamelin pool bathymetry and consider physiography as a control of sedimentation processes including stromatolite development bathymetric transects derived from a high resolution bathymetry map with depths from 0 to 11 meters allow calculation of slope gradients in the provinces as in other settings bathymetry is linked to energy regimes which in turn appear to be coupled with variations in stromatolite morphologies and associated lithofacies as follows 1 low gradient ramps with low energy settings are associated with sheet mats and elongate clustered stromatolites that exhibit regular spatial patterns possibly indicative of self organization 2 low gradients coupled with high energy settings resulting from strong winds result in seif stromatolites with pronounced directional bands 3 medium to steep gradients coupled with medium to high energy are associated with individual and merged stromatolites often with thin basal necks 4 headlands and promontories where the topography deflects currents are associated with elongate nested stromatolites and 5 medium to high energy slopes typically found at promontory edges and shelf margins are dominated by blocky pavement observations linking stromatolite morphology to physiography in a modern microbial system provide insight into the long lived debate about biology versus environment in controlling stromatolite morphology when physiography leads to a high energy regime environmental controls are the main factor determining stromatolite morphology in contrast when physiography promotes a low energy environment the response of biological communities becomes the main driver of macroscale stromatolite morphology

bathymetry retrieval from hyperspectral remote sensing data in optical shallow water in this paper an algorithm for estimating shallow water depth from hyperspectral data is proposed this methodology is based on the different responses of shallow water reflectance on depth and substrate type two parameters similarity coefficient and pearson correlation coefficient are introduced to describe the different types of responses and a linear logarithm ratio model is established using hyperion data over the coastal regions of o ahu island and saint thomas island the retrieved bathymetry is compared with the airborne lidar data the validation results show that the proposed method has good performance and the root mean square error is less than 1 5 m over shallow water shallower than 20 m

effects of channel morphology and sensor spatial resolution on image derived depth estimates the utility of remote sensing in the study of fluvial systems depends upon the extent to which image data can be used to derive quantitative information of sufficient accuracy and precision for specific applications in this study we evaluate the effects of channel morphology on depth retrieval by coupling a radiative transfer model to various morphologic scenarios upwelling radiance l u spectra generated for a range of depths 2 150 cm and benthic cover types limestone periphyton and gravel were linearly mixed to simulate subpixel bed topography and substrate heterogeneity for sloping bottoms solar streambed geometry modified l u relative to a level bottom especially for beds sloping steeply away from the sun aggregate pixel scale l u spectra were compared to a database of simulated spectra to determine the radiance equivalent depth of a uniform bottom redub redub spectra for hypothetical stepped streambeds indicated underestimation of the actual area weighted mean depth but the ln l u l 560 l u l 690 redub ratio consistently reproduced the pixel scale mean for beta distributions of depths similarly when both dark periphyton and bright limestone substrates occurred within a pixel redub spectra produced large errors while the ratio proved robust along channel banks pixels will inevitably be mixed and our simulations indicated that although bank fractions estimated by spectral mixture analysis were highly accurate for vegetated cutbanks gravel bars were sensitive to the selection of both aquatic and terrestrial end members and subject to relatively large fraction errors these theoretical results were tested using a ratio based relative depth map and two end member mixture models derived from a hyperspectral image of the lamar river in yellowstone national park which also served to illustrate the importance and applicability of our simulations the primary conclusions of this study are that 1 the ratio based algorithm is well suited to complex river channels 2 channel morphology and sensor spatial resolution must be considered jointly during data collection and analysis and 3 the accuracy and precision of depth estimates are influenced by channel morphology and thus vary spatially

chemistry of seafloor hydrothermal systems the past four years saw advances in a number of aspects of hydrothermal chemistry high temperature venting was documented at a number of sites in association with the spectrum of seafloor volcanic activity slow to fast spreading normal ridges seamounts back arc settings sediment hosted and sediment starved sites significant progress was made in the description both theoretical and observational of the geometry of circulation and the nature of water rock reaction hydrothermal plumes received extensive study expanding the range of documented anomalies and demonstrating more clearly the links to hydrothermal sedimentation biological chemical interactions began to be explored in a quantitative way pore fluid advection on sedimented ridge flanks was characterized at a number of sites though the general question of the importance of off axis basalt seawater interaction remains unresolved

hydrothermal circulation through mid ocean ridge flanks fluxes of heat and magnesium thermally driven convection of seawater occurs through oceanic crust of all ages at the seafloor spreading axis on mid ocean ridge flanks and in the ocean basins at the ridge axis and on the flanks circulating seawater produces a major chemical exchange between the oceans and the crust based on heat budget constraints and the composition of hot springs between 10 and 40 of the river flux of mg can be taken up during high temperature alteration of the basaltic crust along the ridge axis most of the hydrothermal heat loss however occurs on the mid ocean ridge flanks where the temperatures are lower and the seawater flux correspondingly larger the estimated heat loss on the flanks is so large that upwelling must occur over a large fraction 5 30 of the seafloor less than 65 ma in age if temperatures are 20 c and seepage velocities are on the order of 10 to 100 cm y the circulating seawater needs to lose on average less than 1 2 of its mg content in order to solve the mg mass balance for the oceans chemical fluxes through mid ocean ridge flanks are poorly known because of the wide range of crustal conditions that prevail there and the paucity of study to date the most critical parameter for characterizing crustal conditions is temperature in basement which is a function of crustal age basement topography and sediment thickness and permeability basement temperature which can usually be inferred from heat flow and seismic reflection surveys largely determines the change in the composition of seawater circulating through basement this change can be inferred in turn from profiles of sediment porewater chemistry all sites studied to date with temperatures at the sediment basement interface 25 c have a large component of advective heat loss and show only a small 80 mg loss both types of sites may be important for chemical fluxes whether the cooler sites are important depends on how much the seawater changes in composition as it circulates through the crust only small changes are needed whether the warmer sites are important depends on how much heat is lost by advection in this type of setting the warmer sites could produce significant chemical fluxes even if they are scarce they could account for the entire river input of mg to the oceans even if they represent only 8 20 of the total advective heat loss on ridge flanks

the use of remote sensing and linear wave theory to model local wave energy around alphonse atoll seychelles abstract this paper demonstrates a practical step wise method for modelling wave energy at the landscape scale using gis and remote sensing techniques at alphonse atoll seychelles inputs are a map of the benthic surface seabed cover a detailed bathymetric model derived from remotely sensed compact airborne spectrographic imager casi data and information on regional wave heights incident energy at the reef crest around the atoll perimeter is calculated as a function of its deepwater value with wave parameters significant wave height and period hindcast in the offshore zone using the wavewatch iii application developed by the national oceanographic and atmospheric administration energy modifications are calculated at constant intervals as waves transform over the forereef platform along a series of reef profile transects running into the atoll centre factors for shoaling refraction and frictional attenuation are calculated at each interval for given changes in bathymetry and benthic coverage type and a nominal reduction in absolute energy is incorporated at the reef crest to account for wave breaking overall energy estimates are derived for a period of 5 years and related to spatial patterning of reef flat surface cover sand and seagrass patches

microscale chemical effects of low temperature alteration of dsdp basaltic glasses a novel application of x ray fluorescence using selected area analysis has been used to study the effect of low temperature alteration on trace elements in dsdp basaltic glasses major and minor element distributions were detailed through the use of electron microprobe analyses on the same sample areas samples include pillow basalt rinds and hyaloclastite sections from deep sea drilling project site 396b the glasses were found to release approximately 50 of the original si and al 65 of the mg and na and over 90 of the ca originally present during alteration to palagonite fe and ti were found to be immobile and k was increased 40 fold by concentration from seawater for the trace metals over 25 of the zn cu and ni were released 40 of the mn and over 10 of the cr these changes apply only to the conversion of fresh glass sideromelane to palagonite smectite and do not include the effects of authigenic phillipsite and calcite reprecipitated locally differences between the effects of low temperature weathering on the crystalline basalts and the glasses appear to be primarily a function of the susceptibility of the primary mineral phases to attack with the glass as the least stable phase most altered

bottom characterization by using airborne lidar bathymetry alb waveform features obtained from bottom return residual analysis abstract airborne lidar bathymetry alb surveys are traditionally used for measuring depths in shallow nearshore and back bay areas in this paper we present a novel alb waveform processing procedure namely bottom return residual analysis for bottom characterization waveform features obtained from the bottom return residual analysis are used in a supervised classification approach i e support vector machine to differentiate between 1 sand and rock bottoms and subsequently 2 fine and coarse sand bottoms the classification procedure was tested on alb survey data collected with an optech shoals 1000t alb system that covers a 7 km2 area within 1 km from shore in the western gulf of maine usa the bottom classification results when compared to ground truth measurements indicate a 96 overall accuracy for sand and rock classification and 86 overall accuracy for fine and coarse sand classification results of alb based bottom classification are compared with interpretations of a multibeam echosounder acoustic backscatter mosaic collected from the survey area

current aspects of basin analysis abstract current research in basin analysis focuses on interdisciplinary integration of geodynamics mathematical and physical modelling and sedimentary geology these efforts are organized into a research framework emphasizing basin formation nature of the basin fill maturation diagenesis of the basin fill and timing of events research in geodynamics permits development of a proposed classification of sedimentary basins in which basin types are discriminated according to nature of the plate margin basin position on or within a tectonic plate nature of the crust and geodynamic models or known process of formation a summary of current research developments on sedimentary basin fills focuses on the interdisciplinary solutions developed to understanding carbonate distribution through time origin of black shales sea level history and global sedimentary cycles maturation of basin fills requires an understanding of both thermodynamic aspects of mineral phase changes and changing character of the chemistry of flow of water through porous sediments during basin evolution summary case histories from the illinois basin and the appalachian basin illustrate these approaches

retrieval of nearshore bathymetry from landsat 8 images a tool for coastal monitoring in shallow waters abstract nearshore bathymetry is likely to be the coastal variable that most limits the investigation of coastal processes and the accuracy of numerical models in coastal areas as acquiring medium spatial resolution data in the nearshore is highly demanding and costly as such the ability to derive bathymetry using remote sensing techniques is a topic of increasing interest in coastal monitoring and research this contribution focuses on the application of the linear transform algorithm to obtain satellite derived bathymetry sdb maps of the nearshore at medium resolution 30 m from freely available and easily accessible landsat 8 imagery the algorithm was tuned with available bathymetric light detection and ranging lidar data for a 60 km long nearshore stretch of a highly complex coastal system that includes barrier islands exposed sandy beaches and tidal inlets ria formosa portugal a comparison of the retrieved depths is presented enabling the configuration of nearshore profiles and extracted isobaths to be explored and compared with traditional topographic bathymetric techniques e g high and medium resolution lidar data and survey grade echo sounding combined with high precision positioning systems the results demonstrate that the linear algorithm is efficient for retrieving bathymetry from multi spectral satellite data for shallow water depths 0 to 12 m showing a mean bias of 0 2 m a median difference of 0 1 m and a root mean square error of 0 89 m accuracy is shown to be depth dependent an inherent limitation of passive optical detection systems accuracy further decreases in areas where turbidity is likely to be higher such as locations adjacent to tidal inlets the sdb maps provide reliable estimations of the shoreline position and of nearshore isobaths for different cases along the complex coastline analysed the use of freely available satellite imagery proved to be a quick and reliable method for acquiring updated medium resolution high frequency days and weeks low cost bathymetric information for large areas and depths of up to 12 m in clear waters without wave breaking allowing almost constant monitoring of the submerged beach and the shoreface

comparing the spatial structure of variability in two datasets against each other on the basis of eof modes in analysis of climate variability or change it is often of interest how the spatial structure in modes of variability in two datasets differ from each other e g between past and future climate or between models and observations often such analysis is based on empirical orthogonal function eof analysis or other simple indices of large scale spatial structures the present analysis lays out a concept on how two datasets of multivariate climate variability can be compared against each other on basis of eof analysis and how the differences in the multivariate spatial structure between the two datasets can be quantified in terms of explained variance in the leading spatial patterns it is also illustrated how the patterns of largest differences between the two datasets can be defined and interpreted we illustrate this method on the basis of several well defined artificial examples and by comparing our approach with examples of climate change studies from the literature these literature examples include analysis of changes in the modes of variability under climate change for the sea level pressure slp of the north atlantic and europe the slp of the southern hemisphere the surface temperature of the northern hemisphere the sea surface temperature of the north pacific and for precipitation in the tropical indo pacific

constraints upon water advection in sediments of the mariana trough thermal gradient measurements consolidation tests and pore water compositions from the mariana trough imply that water is moving through the sediments in areas with less than about 100 m of sediment cover the maximum advection rates implied by the thermal measurements and consolidation tests may be as high as 10 5 cm s 1 but are most commonly in the range of 1 to 5 10 6 cm s 1 theoretical calculations of the effect of the highest advection rates upon carbonate dissolution indicate that dissolution may be impeded or enhanced depending upon the direction of flow by a factor of 2 to 5 times the rate for diffusion alone the average percentage of carbonate is consistently higher in two cores from the area with no advection or upward advection than the average percentage of carbonate in three cores from the area with downward advection this increase in average amount of carbonate in cores with upward moving water or no movement cannot be attributed solely to differences in water depth or in amount of terrigenous dilution if the sediment column acts as a passive boundary layer then the water velocities necessary to affect chemical gradients of silica are in the range 10 9 to 10 10 cm s l however if dissolution of silica occurs within the sediment column then the advection velocities needed to affect chemical gradients are at least 3 10 8 cm s l and may be as high as 3 10 6 cm s l this order of magnitude increase in advection velocities when chemical reactions occur within the sediments is probably applicable to other cations in addition to silica if so then the advection velocities needed to affect heat flow 10 8 cm s 1 and pore water chemical gradients are much nearer in magnitude than previously assumed

enhanced detection of the coral acropora cervicornis from satellite imagery using a textural operator the strength of a texture based classification lies in the fact that it detects spatial patterning as a function of spectral variation within a particular facies class as opposed to spectral consistency which drives standard probability driven image classifiers following this premise the moran s i spatial autocorrelation metric was proven to return values which differed significantly for areas characterised by dense interlocking thickets of the coral acropora cervicornis versus areas populated by a sparse mixed coral assemblage dominated by montastrea annularis the different behaviour of the metric was sufficient to facilitate spatial discrimination of the two assemblages using a supervised classifier with accuracies that surpass the level of prediction offered by standard spectral based methods discrimination was optimum when autocorrelation was evaluated within a moving window with side lengths ranging between circa 30 70 m the discrimination ability is postulated to be linked to intrinsic differences in the spatial patterning of the two assemblages at scales of tens of metres the observed patterning can be further related to the growth form and architecture of the differing coral assemblages the study demonstrates the potential of using kernel based autocorrelation metrics in unison with satellite data and offers a pertinent tool for monitoring ecologically important coral assemblages that are statistically indistinct using traditional spectral methods d 2005 elsevier b v all rights reserved

satellite based remote sensing of running water habitats at large riverscape scales tools to analyze habitat heterogeneity for river ecosystem management abstract we illustrate an approach to quantify patterns in hydraulic habitat composition and local heterogeneity applicable at low cost over very large river extents with selectable reach window scales ongoing developments in remote sensing and geographical information science massively improve efficiencies in analyzing earth surface features with the development of new satellite sensors and drone platforms and with the lowered cost of high resolution multispectral imagery fluvial geomorphology is experiencing a revolution in mapping streams at high resolution exploiting the power of aerial or satellite imagery is particularly useful in a riverscape research framework fausch et al 2002 where high resolution sampling of fluvial features and very large coverage extents are needed this study presents a satellite remote sensing method that requires very limited field calibration data to estimate over various scales ranging from 1 m to many tens or river kilometers i spatial composition metrics for key hydraulic mesohabitat types and ii reach scale wetted habitat heterogeneity indices such as the hydromorphological index of diversity hmid when the purpose is hydraulic habitat characterization applied over long river networks the proposed method although less accurate is much less computationally expensive and less data demanding than two dimensional computational fluid dynamics cfd here we illustrate the tools based on a worldview 2 satellite image of the kiamika river near mont laurier quebec canada specifically over a 17 km river reach below the kiamika dam in the first step a high resolution water depth d map is produced from a spectral band ratio calculated from the multispectral image calibrated with limited field measurements next based only on known river discharge and estimated cross section depths at time of image capture empirical based pseudo 2d hydraulic rules are used to rapidly generate a two dimensional map of flow velocity v over the 17 km kiamika reach the joint distribution of d and v variables over wetted zones then is used to reveal structural patterns in hydraulic habitat availability at patch reach and segment scales here we analyze 156 bivariate d v density function plots estimated over moving reach windows along the satellite scene extent to extract 14 physical habitat metrics such as river width mean and modal depths and velocity variances and covariance in d and v over 1 m pixels hmid entropy a principal component analysis on the set of metrics is then used to cluster river reaches in regard to similarity in their hydraulic habitat composition and heterogeneity applications of this approach can include i specific fish habitat detection at riverscape scales e g large areas of riffle spawning beds deeper pools for regional management ii studying how river habitat heterogeneity is correlated to fish distribution and iii guidance for site location for restoration of key habitats or for post regulation monitoring of representative reaches of various types

ocean sand ridge signatures in the bohai sea observed by satellite ocean color and synthetic aperture radar measurements abstract satellite measurements from synthetic aperture radar sar and the moderate resolution imaging spectroradiometer modis onboard the aqua platform are used to study the ocean sand ridges in the eastern bohai sea in china even though the imaging mechanisms for sar and modis aqua remote sensing are different the sand ridges are shown to have exactly the same patterns in images from both sensors therefore the location extension and coverage of the ocean sand ridges can be detected and cross examined by both sar and modis aqua observations satellite images show quite different sand ridge distribution pattern from the published bathymetry map based on in situ data that shows six sand ridges in the area 10 finger shaped sand ridges are identified from satellite observations the tidal current sand ridge interaction driven physical and optical changes are assessed and evaluated the existence of sand ridges causes enhanced water diffuse attenuation coefficient k d 490 and elevated normalized water leaving radiance at the red and near infrared nir wavelengths the sea surface over the sand ridges experiences significant seasonal variability of water turbidity and shows remarkable differences from nearby ocean regions during winter k d 490 values are about 2 3 m 1 over the ridges while the maximum k d 490 in the neighboring oceans is approximately 1 5 m 1 in summer the enhancement of the sea surface turbidity is less significant than that which occurs in winter

permeability underpressures and convection in the oceanic crust near the costa rica rift eastern equatorial pacific in situ permeability and pore pressures were measured 200 m deep beneath the top of the oceanic crust at dsdp site 504b these measurements have relevance for the transition from convective to conductive heat flow on the south flank of the costa rica rift conventional slug and constant rate injection tests were made below a hydraulic packer set at various depths in the hole the packer was first set in a massive flow unit 37 m below the sediment basement interface the bulk permeability of the 172 5 m of pillow basalts and basaltic flows below the packer was found to be about 40 millidarcys 4 10 10 cm2 measurements over 3 and 15 m intervals at the bottom of the hole in an altered pillow zone indicated a bulk permeability of 2 4 millidarcys these values are thought to be accurate to 30 formation pore pressures were found to be approximately 8 bars 2 below hydrostatic interpretation of the data with respect to simple numerical convection models suggests that the transition from convective to conductive heat flow is controlled by the cessation of convective heat transport through the sedimentary layer rather than the cessation of convection in the sediment furthermore the agreement between observed and modeled underpressures implies that hole 504b penetrated an active ocean crustal convection system the thick sedimentary layer layers of basal chert and massive flow basalts above the layer 2a pillow flows apparently form an impermeable lid effectively isolating the convection system from the ocean

hydrothermal circulation juan de fuca ridge eastern flank factors controlling basement water composition pore water has been analyzed from sediment cores taken from three areas on the eastern flank of the juan de fuca ridge as part of flankflux 90 a study of hydrothermal circulation through mid ocean ridge flanks seismic reflection and heat flow surveys davis et al 1992a indicate that the three areas differ in sediment thickness basement topography abundance of outcrops basement temperature and fraction of heat lost by advection versus conduction area 1 is on 0 6 ma crust with nearly continuous basement outcrop area 2 is on 1 3 ma crust over the first buried ridge parallel to the present ridge axis and area 3 is on 3 5 3 8 ma crust over two axis parallel buried ridges that penetrate the sediment cover in three locations each area includes a hydrothermal system in which seawater flows into basement reacts with crustal basalt and then exits basement either through the sediment or directly into the overlying water column as constrained by concentrations of sulfate and lithium in the pore waters at least some seawater enters basement in all three areas without reacting fully with the overlying sediment even where no outcrops are known nearby speeds of up welling of pore water through the sediment have been estimated by fitting profiles of dissolved magnesium and chlorinity which behave conservatively in these areas to numerical time dependent transport models the estimated velocities range from 0 1 to 7 4 cm yr faster flows probably occur but were not sampled upwelling speed correlates positively with heat flow and basement highs and negatively with sediment thickness the correlation with heat flow differs from area 2 to area 3 along with differences in physical properties of the turbidite sediment we have documented pore water upwelling through sediment up to 100 m thick we estimate that upwelling continues at decreasing speeds through sediment up to 160 m thick corresponding to a heat flow of 0 44 w m2 in area 2 and 0 3 w m2 in area 3 concentrations of magnesium and chlorinity in the altered seawater upwelling from basement are uniform within each area but differ from one area to the next both species remain at the bottom seawater concentration in area 1 where basement is cooled to 10 c at the base of the sediments mainly by advection the concentration of magnesium decreases with increasing basement temperature in areas 2 and 3 to a minimum of 2 5 mmol kg at about 90 c in area 3 the transition from largely advective to largely conductive heat loss occurs over only 20 km between areas 1 and 2 and corresponds to a dramatic change in the composition of fluid circulating through basement as the uppermost basement is heated from 10 to 40 50 c chlorinity of the basement fluid increases above the present day bottom seawater concentration in areas 2 and 3 and in nearly all other mid ocean ridge flanks studied to date as a result of rock hydration and the higher chlorinity of bottom seawater during the last glacial period while chlorinity generally correlates positively with uppermost basement temperature in various ridge flank hydrothermal systems it reaches a maximum in area 2 at only 40 c probably because alteration there occurs at a lower water rock ratio than elsewhere for all mid ocean ridge flanks studied to date the temperature at the basement interface correlates better with the fraction of heat lost by advection versus conduction and with the average thickness of the sediment cover than with crustal age

unravelling the influence of water depth and wave energy on the facies diversity of shelf carbonates carbonate sequence stratigraphy is founded on the principle that changes in relative sea level are recorded in the rock record by the accumulation of sediment with relative water depth dependent attributes while at the scale of a shelf to basin transect facies clearly arrange by water depth the relation blurs for depths 40 m the most vigorous zone of carbonate production the reason for this change in behaviour is two fold firstly in shallow water the intrinsic processes of storm and wave reworking influence the seabed through submarine erosion and sediment redistribution secondly facies diversity tends to be greater in shallow water than deep water because of a greater diversity in grain producers remote sensing imagery field observations and hydrodynamic models for two reef rimmed shore attached carbonate platforms in the red sea show neither water depth nor energy regime to be reliable indicators of facies type when considered in isolation considered together however the predictive power of the two variables rises significantly the results demonstrate it to be an oversimplification to assume a direct link between palaeo water depth and depositional diversity of subtidal lithofacies while highlighting the importance of hydrodynamics in directing the accumulation of carbonate sediments in the shallow photic zone while the size distributions of facies extents in the two focus areas follow power laws no direct relation between the lateral continuity of the facies belts and water depth or wave height is reported the work is relevant for the interpretation of metre scale subtidal carbonate cycles throughout the geological record by demonstrating how caution must be applied when inferring palaeowater depths from depositional facies

multiple optimal depth predictors analysis modpa for river bathymetry findings from spectroradiometry simulations and satellite imagery abstract remote mapping of bathymetry can play a key role in gaining spatial and temporal insight into fluvial processes ranging from hydraulics and morphodynamics to habitat conditions this research introduces multiple optimal depth predictors analysis modpa which combines previously developed depth predictors along with additional predictors derived from the intensity component of the hsi color space transformation modpa empirically selects a set of optimal predictors among all candidates utilizing partial least squares pls stepwise or principal component pc regression models the primary focus of this study was on shallow

analysis of the slab ocean el nino atmospheric feedbacks in observed and simulated enso dynamics in a recent study it was illustrated that the el nino southern oscillation enso mode can exist in the absence of any ocean dynamics this oscillating mode exists just due to the interaction between atmospheric heat fluxes and ocean heat capacity the primary purpose of this study is to further explore these atmospheric slab ocean enso dynamics and therefore the role of positive atmospheric feedbacks in model simulations and observations the positive solar radiation feedback to sea surface temperature sst due to reduced cloud cover for anomalous warm ssts is the main positive feedback in the slab ocean el nino dynamics the strength of this positive cloud feedback is strongly related to the strength of the equatorial cold tongue the combination of positive latent and sensible heat fluxes to the west and negative ones to the east of positive anomalies leads to the westward propagation of the sst anomalies which allows for oscillating behavior with a preferred period of 6 7 years several indications are found that parts of these dynamics are indeed observed and simulated in other atmospheric or coupled general circulation models agcms or cgcms the cmip3 agcm slab ensemble of 13 different agcm simulations shows unstable ocean atmosphere interactions along the equatorial pacific related to stronger cold tongues in observations and in the cmip3 and cmip5 cgcm model ensemble the strength and sign of the cloud feedback is a function of the strength of the cold tongue in summary this indicates that the slab ocean el nino dynamics are indeed a characteristic of the equatorial pacific climate that is only dominant or significantly contributing to the enso dynamics if the sst cold tongue is sufficiently strong in the observations this is only the case during strong la nina conditions the presence of the slab ocean enso atmospheric feedbacks in observations and cgcm model simulations implies that the family of physical enso modes does have another member which is entirely driven by atmospheric processes and does not need to have the same spatial pattern nor the same time scales as the main enso dynamics

linking pattern to process in reef sediment dynamics at lady musgrave island southern great barrier reef linking surficial sediment patterns in reef environments to the processes that underlie their depositional dynamics enables predictions to be made of how environmental changes will influence reef associated sedimentary landforms such as islands and beaches geomorphic linkages between sediment deposition patterns and the biophysical processes that drive them are often poorly resolved particularly at broad landscape scales where tangible statements can be made about structural changes to landforms the present study applies geospatial techniques to link patterns in reef sediment dynamics at lady musgrave island to the underlying processes driving them in situ calcification is characterized by developing a high resolution map of the surficial calcium carbonate producing communities inhabiting the reef platform and associated sediments across the reef flat are analysed for grain size kurtosis sorting and threshold bed shear stress to explore transport pathways across the reef flat and lagoon wave energy is modelled across the entire reef platform as a potential driver of sediment dynamics and morphometric linkages are empirically defined between wave energy and grain size findings indicate that carbonate sediments are primarily sourced from calcifying communities colonizing the outer periphery of the reef platform and that sediment grain size can be reliably linked to wave energy by virtue of a linear model

influence of bathymetric fluctuations on coastal storm surge abstract natural events constantly alter nearshore bathymetric properties hurricanes particularly affect bathymetry as they pass over a body of water to compute an accurate forecast or recreate a hurricane s effects through hindcasting techniques an operational bathymetry data set must be known in advance however obtaining and maintaining current and accurate bathymetric data can be costly and difficult to manage in this paper we examine the extent to which variations in nearshore bathymetry affect the storm surge at the coast a common question for wave and surge modeling is how good is the bathymetric data if we can allow for a range of fluctuations in the bathymetry without significantly adjusting the results of the surge predictions we can potentially save months of field work and millions of dollars a one dimensional 1d analytical solution for waves and water level is developed for initial testing in the 1d case we find that as long as the amplitudes of the bathymetric fluctuations are less than 60 of the original depth the surge at the coast is within 10 of the surge generated on the initial bottom slope if the fluctuation produces a hole a deepening of the local bathymetry within 80 of the local water depth the coastal storm surge calculated is still within 10 of the unperturbed value computed for bottom slopes shallower than 1 20 in addition we find there is an optimum distance offshore for each sloped profile that corresponds to a depth between 25 and 40 m beyond which the effects of bathymetric fluctuations begin to decrease a coupled 2d modeling system is implemented to test our hypothesis along a realistic coastline after selecting three study sites we vary the bathymetry at the selected locations by 20 consistent with the 1d tests the storm surge at the shoreline varies by less than 5

influence of elevation modelling on hydrodynamic simulations of a tidally dominated estuary summary hydrodynamic simulation of estuaries requires a single digital elevation model dem resulting from merging of both topographic and bathymetric data these two datasets are usually produced using different technologies co ordinate systems and datums intertidal data in particular are often lacking due to the difficulty of data acquisition using conventional survey techniques this paper presents a fast accurate and low cost methodology to fill this gap and highlights the effect of the digital elevation model characteristics such as the interpolation method and spatial resolution on modelled water levels and flooded areas the lima river estuary located in north western portugal is used as a case study validation tests for commonly available spatial interpolators showed ordinary kriging to be the most adequate interpolator digital elevation models with regular grids of 5 m and 50 m resolution were used together with the original not interpolated elevation dataset as input to a finite element hydrodynamic model for astronomic tide simulation results indicate that the larger differences between using different elevation models occur at low tide during spring tide marginally impacting the flood modelling the effect of a vertical offset of the chart datum with respect to a part of the digital elevation model was finally investigated showing a limited influence in the determination of the water levels

modis observations of the bottom topography and its inter annual variability of poyang lake abstract using modis 250 m resolution data we developed a novel approach to derive the bottom topography of poyang lake the largest freshwater lake of china 3000 km2 at maximum inundation for every year between 2000 and 2009 the approach differs from other traditional methods sonar lidar optical inversion and radar but takes advantage of the fast changing nature of the lake s inundation area on every image the water land boundary is effectively a topographic isobath after correction for the water level gradient thus the 10 year carefully selected modis images provided incremental topographic isobaths from which bottom topography was derived every year such derived topographic maps were validated using limited historical data and other consistency checks most of the lake bottom showed an elevation of 12 m to 17 m referenced against the elevation reference of the woosung horizontal zero significant inter annual variability of the bottom topography from 2000 to 2009 was found for some of the lake s bottom with more areas associated with bottom elevation increases than decreases the changes and inter annual variability in the bottom topography were attributed to the combined effect of human activities e g sand dredging and levee construction and weather events one example was the increased bottom elevation from 2002 to 2003 which was apparently due to the excessive precipitation in 2002 and the impoundment of the three gorges dam in 2003 the 10 year record of the bottom topography of this highly dynamic lake provides baseline information to monitor the impact of future engineering and management activities to estimate the lake s water and sediment budgets and to aid ship navigation

evidence for excess pore pressures in southwest indian ocean sediments brown clay cores from the madagascar and crozet basins show the following evidence of excess pore pressures large amounts of flow in increasing average sedimentation rate with age and nonlinear temperature gradients additionally many hilltops in these basins have no visible sediment cover the bare hilltops may result from periodic slumping caused by excess pore pressures calculated excess pore pressures which equal or exceed the overburden pressure were inferred from water fluxes predicted by nonlinear temperature gradients and laboratory permeability measurements by using darcy s law since pore pressures which exceed the overburden pressure are unreasonable we attribute this discrepancy to laboratory measures which underestimate the in situ permeability the widespread presence of overpressured sediments in areas of irregular topography provides a process for resuspension of clay sized particles this mechanism does not require high current velocities for the erosion of clay and therefore can be applied to many areas where no strong currents are evident carbonate rich sediments from the madagascar ridge the mozambique ridge and the agulhas plateau had almost no flow in and occurred in areas where all topography was thickly draped with sediment since the age and tectonic location of the ridges and plateaus preclude water circulation in the basement wemore attribute these differences between the brown clay and the carbonate rich material to an absence of significant excess pore pressures in the plateau and ridge sediments less

magma in forearcs implication for ophiolite generation abstract forearc areas non volcanic arcs of contemporary island arcs at convergent plate boundaries contain magmatic rocks geological evidence seismic profiles heat flow data density considerations and petrological and geochemical arguments suggest that a forearc tholeiitic association fat containing high mg calc alkaline andesites is present in non volcanic arcs at some stage of island arc development the fractionated as well as primitive magma is unable to penetrate low density sediments and underplates thick piles of unconsolidated accreting rocks the underplating causes upwelling the occurrence of magma in forearcs provides an alternative interpretation for the tectonic setting of some ophiolitic masses rather than ocean ridge formation and later obduction it offers an autochthonous island arc bound and geologically substantiated interpretation for the ophiolite suite

spectrally based remote sensing of river bathymetry this paper evaluates the potential for remote mapping of river bathymetry by 1 examining the theoretical basis of a simple ratio based technique for retrieving depth information from passive optical image data 2 performing radiative transfer simulations to quantify the effects of suspended sediment concentration bottom reflectance and water surface state 3 assessing the accuracy of spectrally based depth retrieval under field conditions via ground based reflectance measurements and 4 producing bathymetric maps for a pair of gravel bed rivers from hyperspectral image data consideration of the relative magnitudes of various radiance components allowed us to define the range of conditions under which spectrally based depth retrieval is appropriate the remotely sensed signal must be dominated by bottom reflected radiance we developed a simple algorithm called optimal band ratio analysis obra for identifying pairs of wavelengths for which this critical assumption is valid and which yield strong linear relationships between an image derived quantity x and flow depth d obra of simulated spectra indicated that water column optical properties were accounted for by a shorter wavelength numerator band sensitive to scattering by suspended sediment while depth information was provided by a longer wavelength denominator band subject to strong absorption by pure water field spectra suggested that bottom reflectance was fairly homogeneous isolating the effect of depth and that radiance measured above the water surface was primarily reflected from the bottom not the water column obra of these data 28 of which were collected during a period of high turbidity yielded strong x versus d relations r2 from 0 792 to 0 976 demonstrating that accurate depth retrieval is feasible under field conditions moreover application of obra to hyperspectral image data resulted in spatially coherent hydraulically reasonable bathymetric maps though negative depth estimates occurred along channel margins where pixels were mixed this study indicates that passive optical remote sensing could become a viable tool for measuring river bathymetry copyright 2009 john wiley sons ltd

diagenesis of sandstones in the back arc basins of the western pacific ocean sandstones occur in back arc basins of the western pacific at dsdp sites 299 sea of japan 297 northern shikoku basin 445 and 446 daito ridge and basin province 453 mariana trough 286 new hebrides basin and 285 south fiji basin these sandstones are dominantly volcaniclastic arenites derived from andesitic island arcs the degree of sandstone diagenesis is dependent on original composition burial rate heat flow history of the basin and timing of sandstone deposition with respect to rifting processes and associated high heat flow sandstones containing a larger proportion of volcaniclastic components showed more diagenetic effects than sandstones containing a significant volume of other rock fragments and mineral components sandstones deposited during early stages of rifting sites 445 446 with a slow burial rate and high crustal heat flow showed the greatest degree of downhole diagenetic change these diagenetic changes include early pore space reduction and rim cementation by clay minerals followed later by calcite and subsequent pore fill cementation by clinoptilolite heulandite analcite and later calcite replacement of recognizable volcanic rock fragments by chert calcite and zeolites was observed in the deepest part of the hole sandstones deposited after rifting under conditions of associated lower heat flow showed considerably less diagenetic changes particularly if burial was rapid the high heat flow associated with earliest rifting associated fluid circulation driven by thermal convection and slow burial rate controlled the diagenetic history of these sandstones thus timing of sandstone deposition with rifting stage and associated burial rates were key factors in controlling sandstone diagenesis in back arc basins

patterns of sedimentation in the contemporary red sea as an analog for ancient carbonates in rift settings abstract patterns of sedimentation in the red sea offer a contemporary analog for carbonate deposition in marine rift settings covering 20 of latitude the sea is sufficiently long to display pronounced climate differences and the clear tropical waters support vigorous coral reef growth and associated production of carbonate sediment six focus areas within the red sea each covering exactly 1 600 sq km illustrate the variability of spatial patterns in reefal and other carbonates in this rift setting five of the focus areas are located on a north south transect along the western margin of the sea 1 gubal straits egypt 2 shalatayn egypt 3 trinkitat sudan 4 dahlak eritrea and 5 halib eritrea and one is from the eastern margin 6 farasan banks saudi arabia using landsat imagery water depth and two marine facies classes reefal frameworks and sediments were mapped lumping these two classes define carbonate bodies that were analyzed for trends in orientation relation to local fault networks and size frequency distribution fault lineaments digitized from the literature are closely related to the orientation of carbonate bodies with areas exceeding 5 sq km smaller bodies do not preferentially align with fault trends water depth and the occurrence of reefal frameworks and sediments for the six focus areas are not systematically related used as an analog these data from the contemporary red sea may provide insight into the orientation and scale of accumulation of carbonates in subsurface marine rift settings

the composition and diagenesis of interstitial solutions ii fluxes and diagenesis at the water sediment interface in the high latitude north and south atlantic studies of the major element composition of in situ sampled pore waters are reported for the north atlantic and southern ocean between africa and antarctica the pattern of diagenetic modification of pore water composition is similar throughout the entire atlantic enrichment of na ca2 and alkalinity and depletion of mg2 and k are nearly universal only siliceous oozes consistently provide very limited evidence of cation diagenesis the changes observed and the calculated fluxes across the seawater sediment interface are much the same as those reported previously for other areas of the atlantic and caribbean fluxes of the major cations across the interface continue to be indicated as a major factor in the geochemical cycling of these elements particularly na mg2 and k diagenetic modelling indicates that aerobic oxidation of organic matter and consequent dissolution of caco3 is a dominant reaction throughout the north atlantic the data indicate that o2 oxidation to at least 30 cm is prevalent at nearly all stations dissolution of caco3 in response to the introduction of metabolic co2 can lead to significant post depositional modification of the sediments the modelling also indicates a 1 1 stoichiometric relationship between na release and mg2 uptake by sedimentary components although dissolved silica concentrations in biogenic siliceous sediments are among the highest yet reported 700 m calculations demonstrate that solubility control cannot be through equilibria with the mineral sepiolite further the influence of cation silicate surface phases generally upon solubility is contraindicated by si oh 4 mg2 h relationships evaluation of the influence of fluid advection on pore water profiles indicates that at the stations studied in the north atlantic it is small a more general consideration of the potential contribution of fluid advection to shaping interstitial water profiles demonstrates that advection can be a dominant factor in such circumstances serious misinterpretation of the nature of diagenetic reactions may result from a lack of knowledge and consideration of fluid advection

a semianalytical ocean color inversion algorithm with explicit water column depth and substrate reflectance parameterization a semianalytical ocean color inversion algorithm was developed for improving retrievals of inherent optical properties iops in optically shallow waters in clear geometrically shallow waters light reflected off the seafloor can contribute to the water leaving radiance signal this can have a confounding effect on ocean color algorithms developed for optically deep waters leading to an overestimation of iops the algorithm described here the shallow water inversion model swim uses pre existing knowledge of bathymetry and benthic substrate brightness to account for optically shallow effects swim was incorporated into the nasa ocean biology processing group s l2gen code and tested in waters of the great barrier reef australia using the moderate resolution imaging spectroradiometer modis aqua time series 2002 2013 swim derived values of the total non water absorption coefficient at 443 nm at 443 the particulate backscattering coefficient at 443 nm bbp 443 and the diffuse attenuation coefficient at 488 nm kd 488 were compared with values derived using the generalized inherent optical properties algorithm giop and the quasi analytical algorithm qaa the results indicated that in clear optically shallow waters swim derived values of at 443 bbp 443 and kd 443 were realistically lower than values derived using giop and qaa in agreement with radiative transfer modeling this signified that the benthic reflectance correction was performing as expected however in more optically complex waters swim had difficulty converging to a solution a likely consequence of internal iop parameterizations whilst a comprehensive study of the swim algorithm s behavior was conducted further work is needed to validate the algorithm using in situ data

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

the leading modes of decadal sst variability in the southern ocean in cmip5 simulations the leading modes of sea surface temperature variability in the southern ocean on decadal and even larger time scales are analysed using coupled model intercomparison project 5 cmip5 model simulations and observations the analysis is based on empirical orthogonal function modes of the cmip5 model super ensemble we compare the modes from the cmip5 super ensemble against several simple null hypotheses such as isotropic diffusion red noise and a slab ocean model to investigate the sources of decadal variability and the physical processes affecting the characteristics of the modes the results show three main modes in the southern ocean the first and most dominant mode on interannual to decadal time scales is an annular mode with largest amplitudes in the pacific which is strongly related to atmospheric forcing by the southern annular mode and el nino southern oscillation the second mode is an almost basin wide monopole pattern which has pronounced multi decadal and longer time scales variability it is firstly inducted by the wave 3 patterns in the atmosphere and further developed via ocean dynamics the third mode is a dipole pattern in the southern pacific that has a pronounced peak in the power spectrum at multi decadal time scales all three leading modes found in the cmip5 super model have distinct patterns and time scale behaviour that can not be explained by simple stochastic null hypothesis thus all three leading modes are ocean atmosphere coupled modes and are likely to be substantially influenced or driven by ocean dynamical processes

a reef up approach to classifying coral habitats from ikonos imagery monitoring coral reef benthos with satellites has typically followed a sensor down approach with the classification algorithm driven by statistics derived from the imagery i adopt a reef up method drawing on statistics derived from hyperspectral optical field measurements of substrate reflectance to train image classification in order to calibrate the satellite data with direct physical measurements of reflectivity it is necessary to process both the imagery and in situ data to common units of albedo building upon a proof of concept study conducted by the author in the red sea the link is made by correcting the remote sensing data for the effect of varying bathymetry using in situ measurement of water column optical properties and a digital elevation model constructed from a vessel based acoustic survey thereby yielding units of substrate reflectance extensive ground verification of the predictive benthic habitat map resulting from image classification showed that eight substrate classes were resolved with an overall accuracy of 69 down to a depth of 6 m including live and dead coral framework as compared to conventional from image classification techniques the reef up method offers the potential for higher thematic accuracy while maintaining a greater degree of flexibility for repeat survey using platforms of higher spectral and spatial resolution expected to come online in the near future the fact that image acquisition and optical ground truthing did not occur concurrently is of particular relevance in confirming that in situ measurements can be made independent of image acquisition and retrospectively linked to appropriate substrate classes considering the wealth of hyperspectral data already acquired for shallow reef facies the work highlights the potential of the reef up approach for quantifying substrate distribution in coral environments using both air and spaceborne platforms

coral reef habitat mapping a combination of object based image analysis and ecological modelling despite being one of the most important and well studied coral reefs in the world the full extent of coral habitat of the great barrier reef gbr is not well mapped and there is no current and comprehensive map of the gbr s geomorphic zonation or benthic composition this paper demonstrates an approach that integrates ecological coral habitat mapping with empirical modelling to map the geomorphic zonation and benthic composition of the shallow offshore reefs of the gbr using the capricorn bunker group cbg as a case study the approach combined environmental data sets and geo ecological rule sets to identify geomorphic zones the benthic composition of individual geomorphic zones was mapped for shallow reef flat zones using object based image analysis with context driven rules based on coral reef ecology and reef slope zones using levels of wave exposure to predict the distribution of coral types the environmental data sets used were field based benthic composition data landsat 8 oli satellite image derived bottom reflectance water depth and slope 15 m 15 m pixel size data reef impact data and modelled wave exposure the study showed that the combination of geomorphic ecological rules and models with remote sensing imagery provided robust mapping results over a large 2500 km2 reef system of which 245 km2 was mapped as shallow coral reefs and 88 km2 of that was mapped as areas containing coral most importantly the method produced defined the geomorphic zones and benthic composition of a study area that is significantly larger than the majority of coral reef remote sensing mapping projects previously published with some modifications the methods presented have the potential to be applied to the full extent of the shallow offshore reefs of the gbr or any large reef globally monitoring and management of coral reefs for conservation and other purposes at regional to global scales will benefit from the ability to produce and use this type of essential information on a regular basis

a preliminary assessment of geodynamic controls on depositional systems and sandstone diagenesis in back arc basins western pacific ocean abstract nine depositional systems are recognized in cores recovered by the deep sea drilling project from the back arc basins of the western pacific these systems include submarine fan debris flow silty basinal turbidite biogenic pelagic carbonate resedimented carbonate biogenic pelagic silica pyroclastic hemipelagic and turbid layer clay and pelagic clay depositional systems the occurrence of these depositional systems in time and space is correlated with regional uplift and volcanism climatic change biological productivity and critical relations of sediment yield from potential sources which experience sufficient uplift and development of an extensive drainage and erosional regimen debris flows and submarine fan systems tend to accumulate after uplift of andesitic volcanic arc sources following development of a regional drainage network biogenic pelagic systems tend to be controlled by biological productivity and are indicators of back arc basin movement through such productivity zones by regional crustal shift hemipelagic and turbid layer clay systems are derived from terrigenous sources and their volume is dependent on climatically controlled sediment yield from such sources resedimented carbonate systems tend to occur during times of active basinal faulting volcaniclastic sandstones recovered in back arc basin dsdp cores show evidence of diagenetic alteration in response to burial depth temperature and thermally driven fluid circulation younger sandstones tend to show pore space reduction rim cementation by chlorite and mixed layer illite smectite and pore filling cementation by clinoptilolite downhole pores are filled with heulandite and analcite older sandstones show pore filling with sparry calcite and replacement of component minerals and rock fragments by calcite chert and zeolites the distinct age depth zonation of diagenetic changes suggests that thermally driven interstitial fluids combined with advection of ocean waters and basement waters accounts best for the mineralogical reactions observed

spectral signatures of coral reefs features from space the spectral signatures of coral reefs and related scenes as they would be measured above the earth s atmosphere are calculated using a coupled atmosphere ocean discrete ordinates radiative transfer model actual measured reflectance spectra from field work are used as input data four coral species are considered to survey the natural range of coral reflectance montastrea cavernosa acropora palmata dichocoenia stokesii and siderastrea siderea four noncoral objects associated with reefs are also considered sand coralline algae green macroalgae and algal turf the reflectance spectra as would be measured at the top of the atmosphere are substantially different from the in situ spectra due to differential attenuation by the water column and most importantly by atmospheric rayleigh scattering the result is that many of the spectral features that can be used to distinguish coral species from their surroundings or from one another which have been used successfully with surface or aircraft data would be obscured in spectral measurements from a spacecraft however above the atmosphere the radiance contrasts between most coral species and most brighter noncoral objects remain noticeable for water column depths up to 20 m over many spectral intervals the reflectance from dark coral under shallow water is smaller than that of deep water the maximum top of atmosphere radiances and maximum contrasts between scene types occur between 400 nm and 600 nm this study supports the conclusions of recent satellite reef mapping exercises suggesting that coral reef identification should be feasible using satellite remote sensing but that detailed reef mapping e g species identification may be more difficult

multi band spectral matching inversion algorithm to derive water column properties in optically shallow waters an optimization of parameterization abstract deriving inherent optical properties iops and other water quality parameters from satellite remote sensing data covering optically shallow environments has historically been problematic due to difficulties in separating the benthic signal from that of the water column while recent advances have improved such retrievals most methods have high uncertainties for very shallow

submarine hydrothermal metallogenesis associated with the collision of two plates the southern aegean sea region abstract the geochemistry of sediments from the southern aegean sea demonstrates that the active tectonics in the hellenic arc trench system favor hydrothermal mineralization processes involving leaching of oceanic crust the distribution and geochemical behavior of mn fe cu zn p and ba indicate a hydrothermal influence i at plate boundaries such as the pliny and strabon trenches ii in fore arc basins such as maleas iraklion and karpathos iii on the island arc all fore arc basins having greater mn enrichments than the trenches are also characterized by higher heat flow values the greatest mn enrichments occur at maleas basin where a mn dispersion halo is recognized this basin is very tectonically active with the largest group of normal faults along the planes of which magmatic material was injected and the highest heat flow values in the sea of crete it also falls in the eastern mediterranean zone of high seismic activity because the fe mn sediments identified in the above geotectonic units are the end members of the hydrothermal fractionation sequence known from areas where leaching of oceanic crust occurs it is suggested that other members of the sequence such as metal sulfides may be found significant geochemical anomalies of pb and zn found in areas of high heat flow and on lines of normal faulting are considered to be traces of the presence of metal sulfides

correlated sediment thickness temperature gradient and excess pore pressure in a marine fault block basin measurements of temperature gradient and excess pore pressure in the surficial sediment of a fault block basin in the guatemala basin correlate with sediment thickness the temperature gradient is smaller and the excess pore pressure gradient is more negative in areas of thinner sediment this correlation is explained by postulating downward pore water advection within the sediments with flow velocities on the order of 10 9 to 10 8 m s in the thinnest sediments and much less flow in the thickest sediments sediment physical properties and pore water chemistry also support this interpretation since the conductive heat flow of the basin as a whole is less than one third that predicted by sea floor spreading models the oceanic basement may be the site of a vigorous hydrothermal circulation system the pore water advection in the sediments may be driven by this larger scale circulation

nearshore sandbars crest position dynamics analysed based on earth observation data abstract understanding long term underwater sandbars dynamics is a key element for optimal coastal zone management but this endeavour is often held back by data availability in order to increase the spatial and temporal resolution availability and quality of sandbars observations this study proposes and evaluates a new approach for automatic extraction of sandbars positions from freely available satellite imagery using a case study of complex waters located on the danube delta coast black sea validation of the satellite extracted sandbars locations against 4 in situ measurements between 2016 and 2018 shows a very good correlation between the two datasets demonstrating the high accuracy of satellite derived data in revealing the underwater morphology of the upper shoreface along large areas and with high temporal resolution the obtained sandbars positions were then integrated into an automatic workflow able to accurately represent the seasonal and multi annual sandbars dynamics and also to give an insight about the sandbars alongshore behavioural changes the results are similar to the ones previously suggested by other studies which empowered different methods these prove the high potential of the newly proposed algorithm to be used for the automatic extraction of the positions of underwater features in the surf zone on other sites worldwide after proper tuning of parameters in accordance with local conditions the main constraints of the proposed approach are represented by the omission of sandbars position that imprint a low signal on the satellite image due to increased water depth especially for the outer bar high turbidity mostly for the inner bar or any other noise generation situation sun glint small wind waves the main advantages of the described algorithm are related to the simplicity of implementation and adaptability to other areas of interest and other types of satellite data

the eastward shift of the walker circulation in response to global warming and its relationship to enso variability this study investigates the global warming response of the walker circulation and the other zonal circulation cells represented by the zonal stream function in cmip3 and cmip5 climate models the changes in the mean state are presented as well as the changes in the modes of variability the mean zonal circulation weakens in the multi model ensembles nearly everywhere along the equator under both the rcp4 5 and sres a1b scenarios over the pacific the walker circulation also shows a significant eastward shift these changes in the mean circulation are very similar to the leading mode of interannual variability in the tropical zonal circulation cells which is dominated by el nino southern oscillation variability during an el nino event the circulation weakens and the rising branch over the maritime continent shifts to the east in comparison to neutral conditions vice versa for a la nina event two thirds of the global warming forced trend of the walker circulation can be explained by a long term trend in this interannual variability pattern i e a shift towards more el nino like conditions in the multi model mean under global warming further interannual variability in the zonal circulation exhibits an asymmetry between el nino and la nina events el nino anomalies are located more to the east compared with la nina anomalies consistent with this asymmetry we find a shift to the east of the dominant mode of variability of zonal stream function under global warming all these results vary among the individual models but the multi model ensembles of cmip3 and cmip5 show in nearly all aspects very similar results which underline the robustness of these results the observed data era interim reanalysis from 1979 to 2012 shows a westward shift and strengthening of the walker circulation this is opposite to what the results in the cmip models reveal however 75 of the trend of the walker circulation can again be explained by a shift of the dominant mode of variability but here towards more la nina like conditions thus in both climate change projections and observations the long term trends of the walker circulation seem to follow to a large part the pre existing dominant mode of internal variability

influence of offshore shoals on spatial variability of storm surge abstract idealized bathymetries were subjected to idealized cyclones in order to measure the storm surge response to a range of shoals under various storm conditions for the purpose of informing the development of bathymetry thinning algorithms nine bathymetries were considered including eight large offshore shoals and a featureless reference domain six storm realizations two different sizes intensities and three different landfall directions were used as meteorological forcing shoal influence on surge was examined over the entire continental shelf throughout the surge event quantification of shoal impact on surge was performed prior to landfall near the time of peak surge and during surge recession three elevation difference contours 1 0 0 5 and 0 5 m were used to quantify the spatial variation in surge caused by the shoals at the three times examined positive contours 1 0 and 0 5 m were used to show that a shoal increased surge locally and the negative contour 0 5 m to show that a shoal decreased surge locally the influences of three shoal parameters depth below mean sea level msl cross shore width and distance from shore were isolated and examined to see which characteristics caused the shoals to alter surge in many cases the shoals did not have much effect on the surge response only 13 of the samples used to quantify shoal impact on surge indicated any shoal influence whatsoever and the shoals did not alter maximum elevation within the threshold considered 0 5 m anywhere in the domain however analysis of the elevation difference contours revealed multiple types of shoal influence the shoals increased surge when they reduced setdown in storms with offshore winds prior to landfall and when they delayed surge recession after all storms the shoals decreased surge when they impeded shoreward flow delaying the arrival of surge in cases when the shoals altered surge 95 of the impact was caused by shallow features 0 5 m below msl also there appears to be a maximum area over which a shoal can influence surge all changes in surge greater than the threshold of 0 5 m occurred over the shoal or approximately between the shoal and the shore the implications of our results for bathymetry thinning follow in general offshore shoals do not need to be resolved in bathymetry data sets used in surge modeling especially if their impact on maximum elevation is the primary concern since a shoal s depth below msl was an excellent indicator of whether it would impact storm surge we recommend that feature depth below msl be used as a bathymetry thinning criterion finally a feature s maximum area of influence could be a useful property for determining whether it should be retained in a bathymetry dataset if one s area of interest is outside of a feature s area of influence the feature could be omitted regardless of its impact on surge