enhanced turbulence and energy dissipation at ocean fronts the ocean surface boundary layer mediates air sea exchange in the classical paradigm and in current climate models its turbulence is driven by atmospheric forcing observations at a 1 kilometer wide front within the kuroshio current indicate that the rate of energy dissipation within the boundary layer is enhanced by one to two orders of magnitude suggesting that the front rather than the atmospheric forcing supplied the energy for the turbulence the data quantitatively support the hypothesis that winds aligned with the frontal velocity catalyzed a release of energy from the front to the turbulence the resulting boundary layer is stratified in contrast to the classically well mixed layer these effects will be strongest at the intense fronts found in the kuroshio current the gulf stream and the antarctic circumpolar current all of which are key players in the climate system

significant sink of ocean eddy energy near western boundaries ocean eddies generated through instability of the mean flow are a vital component of the energy budget of the global ocean modelling combined with satellite altimetry data suggests that the energy from westward propagating eddies is scattered and eventually dispersed when they reach the western boundary of an ocean basin

abyssal circulation driven by near boundary mixing water mass transformations and interior stratification the emerging view of the abyssal circulation is that it is associated with bottom enhanced mixing which results in downwelling in the stratified ocean interior and upwelling in a bottom boundary layer along the insulating and sloping seafloor in the limit of slowly varying vertical stratification and topography however boundary layer theory predicts that these upslope and downslope flows largely compensate such that net water mass transformations along the slope are vanishingly small using a planetary geostrophic circulation model that resolves both the boundary layer dynamics and the large scale overturning in an idealized basin with bottom enhanced mixing along a midocean ridge we show that vertical variations in stratification become sufficiently large at equilibrium to reduce the degree of compensation along the midocean ridge flanks the resulting large net transformations are similar to estimates for the abyssal ocean and span the vertical extent of the ridge these results suggest that boundary flows generated by mixing play a crucial role in setting the global ocean stratification and overturning circulation requiring a revision of abyssal ocean theories

seasonal mesoscale and submesoscale eddy variability along the north pacific subtropical countercurrent abstractlocated at the center of the western north pacific subtropical gyre the subtropical countercurrent stcc is not only abundant in mesoscale eddies but also exhibits prominent submesoscale eddy features output from a high resolution ogcm simulation and a gridded satellite altimetry product are analyzed to contrast the seasonal stcc variability in the mesoscale versus submesoscale ranges resolving the eddy scales of 150 km the altimetry product reveals that the stcc eddy kinetic energy and rms vorticity have a seasonal maximum in may and april respectively a weak positive vorticity skewness without seasonal dependence and an inverse forward kinetic energy cascade for wavelengths larger shorter than 250 km in contrast the submesoscale resolving ogcm simulation detects that the stcc eddy kinetic energy and rms vorticity both appear in march a large positive vorticity skewness with strong seasonality and an intense inverse kinetic energy cascade whose short wave cutoff migrates seaso

the vertical partition of oceanic horizontal kinetic energy to produce an interpretation of the surface kinetic energy as measured by altimeters a survey is made of the vertical structure of kinetic energy profiles in a large number of globally distributed long current meter records although the data are geographically confined primarily to a latitude band in the north pacific to the north atlantic and to a few moorings in the south atlantic the results show generally speaking that most regions are dominated by the barotropic and first baroclinic modes because of the near surface intensification of baroclinic modes altimeters primarily reflect the first baroclinic mode and thus the motion of the main thermocline there is good quantitative agreement with a few exceptions with estimates of the surface kinetic energy obtained from the topex poseidon altimeter and from vertical extrapolations to the surface of the mooring profiles these results are consistent with previous suggestions that barotropic models have little skill in depicting variability as seen in the altimeter data an eof analysis is shown to produce fictitious mode coupling unless the dynamical modes have very different energy levels

ocean turbulent dynamics at superresolution from optimal multiresolution analysis and multiplicative cascade the synoptic determination of ocean circulation using the data acquired from space with a coherent depiction of its turbulent characteristics remains a fundamental challenge in oceanography this determination has the potential of revealing all aspects of the ocean dynamic variability on a wide range of spatiotemporal scales and will enhance our understanding of ocean atmosphere exchanges at superresolution as required in the present context of climate change here we show a four year time series of spatial superresolution 4 km turbulent ocean dynamics generated from satellite data using emerging ideas in signal processing coming from nonlinear physics low resolution dynamics and superresolution oceanic sea surface temperature data acquired from optical sensors the method at its core consists in propagating across the scales the low resolution dynamics in a multiresolution analysis computed on adimensional critical transition information

wave ravinement surfaces classification and key characteristics abstract the wave ravinement surface wrs is a surface of sequence stratigraphic significance that forms in shallow water settings during transgression it develops progressively landward during shoreface retreat due to wave action which erodes the substrate and leads to sediment bypass in the offshore direction the wrs may rework previously formed surfaces such as the maximum regressive surface also known as the transgressive surface and the subaerial unconformity becoming a systems tract and or sequence boundary due to the associated lithological contrast between underlying and overlying deposits and the presence of lags and or shell pavements the wrs has a very good appearance in both outcrop and cores and is often used as the boundary of shallow marine stratigraphic sequences the wrs therefore represents an important lithological and paleo environmental break and its recognition is significant for reconstructing stratigraphic architectures and the history of relative sea level change as well as for reservoir characterization several controlling factors govern the development of the wrs and of the associated deposits they include the accommodation to sedimentation a s ratio environmental energy topographic gradient roughness and lithology of the substrate relatively low rates of relative sea level rise and sediment supply high wave energy steep topographies and easily erodible substrates favor the development of the wrs these factors interact leading to a high variability in the amount of erosion shape length along depositional dip and deposits associated with these surfaces wrss may be classified based on either underlying or overlying deposits or a combination of both a classification based on the deposits that underlie the wrs helps to determine the location of the studied outcrop along depositional dip whereas a classification based on the deposits that overlie the wrs afford insights into the physical conditions that accompanied its formation however the best description of the wrs in terms of location of a considered outcrop physical conditions under which the wrs developed and their lateral variability type of substrate as well as its practical significance for reservoir modeling is achieved with a combination of the two criteria

global energy dissipation rate of deep ocean low frequency flows by quadratic bottom boundary layer drag computations from current meter data the global energy dissipation rate of deep ocean low frequency flows by quadratic bottom boundary layer drag is estimated in three ways first an average over the dissipations computed from the near bottom velocities recorded by 290 moored current meters is multiplied by the world ocean area second near global maps of surface velocities derived from satellite altimetry data are used to estimate the bias due to the sparse spatial coverage of the moorings third a relationship between bottom and surface flows computed over the mooring locations is used to estimate global maps of bottom flows from the surface data all three methods suggest that at least 0 2 tw of the wind power input into geostrophic flows is dissipated in deep water by quadratic bottom drag implications for the oceanic overturning circulation and for oceanic mesoscale eddy dynamics are briefly discussed

the ocean mesoscale regime of the reduced gravity quasigeostrophic model abstracta statistical equilibrium geostrophic turbulence regime of the stochastically forced one layer reduced gravity quasigeostrophic model is identified in which the numerical solutions are

global energy conversion rate from geostrophic flows into internal lee waves in the deep ocean a global estimate of the energy conversion rate from geostrophic flows into internal lee waves in the ocean is presented the estimate is based on a linear theory applied to bottom topography at o 1 10 km scales obtained from single beam echo soundings to bottom stratification estimated from climatology and to bottom velocity obtained from a global ocean model the total energy flux into internal lee waves is estimated to be 0 2 tw which is 20 of the global wind power input into the ocean the geographical distribution of the energy flux is largest in the southern ocean which accounts for half of the total energy flux the results suggest that the generation of internal lee waves at rough topography is a significant energy sink for the geostrophic flows as well as an important energy source for internal waves and the associated turbulent mixing in the deep ocean

multi angular reflectance properties of a hemiboreal forest an analysis using chris proba data abstract forest types differ in their hyperspectral anisotropy patterns mainly due to species specific geometrical structure spatial arrangement of canopies and subsequent shadow patterns this paper examines the multi angular hyperspectral reflectance properties of typical hemiboreal forests during summer time using three simultaneous chris proba mode 3 scenes and stand inventory data from the jarvselja training and experimental forestry district in southeastern estonia we investigated the magnitude and reasons for the differences in the anisotropy patterns of deciduous and coniferous stands at three backward viewing angles a forest reflectance model frt was used as a tool to provide a theoretical basis to the discussion and to estimate the directional contribution of scattering from crowns and ground to total stand reflectance for the two forest types the frt model simulated successfully the hdrf hemispherical directional reflectance factor curves of the study stands to match those obtained from the chris image yet it produced a smaller and less wavelength dependent angular reflectance effect than was observed in the satellite image the main results of this study provide new information for separating the spectral contribution of the forest floor or understory layer from the tree canopy layer 1 the red edge domain was identified to have the largest contribution from forest understory and 2 the more oblique the viewing angle the smaller the contribution from the understory in addition coniferous stands were observed to have a specific angular effect at the red and red edge domain possibly as a result of the hierarchical structure and arrangement of coniferous canopies

small scale topographic form stress and local dynamics of the southern ocean the contribution of small scale abyssal hill topography to the topographic form stress and local dynamics of the southern ocean is investigated using a high resolution model of the sector of the southern ocean south of tasmania and new zealand the results of two simulations with and without small o 1 100 km scale topography confirm that the effects of small scale topography are exerted through the generation of strong topographic form stress leading to transient eddy dissipation and changes in flow meanders small scale topographic form stress is comparable in magnitude to that generated by large scale topography but with a pairwise distribution of positive and negative stress values upstream and downstream of the macquarie ridge consistent with the meandering of the flow in the experiment without small scale topography the bottom mean flow speed increases while the surface mean speed slightly decreases making the mean flow more barotropic eddy kinetic energy also greatly enhances throughout the water column after removing small scale topography our results suggest that small scale topography has strong impact on transient eddies and plays an important role for setting the vertical structure of the flow and the equilibration and position of flow meanders

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

internal lee wave closures parameter sensitivity and comparison to observations this paper examines two internal lee wave closures that have been used together with ocean models to predict the time averaged global energy conversion rate into lee waves and dissipation rate associated with lee waves and topographic blocking the garner 2005 scheme and the bell 1975 theory the closure predictions in two southern ocean regions where geostrophic flows dominate over tides are examined and compared to microstructure profiler observations of the turbulent kinetic energy dissipation rate where the latter are assumed to reflect the dissipation associated with topographic blocking and generated lee wave energy it is shown that when applied to these southern ocean regions the two closures differ most in their treatment of topographic blocking for several reasons pointwise validation of the closures is not possible using existing observations but horizontally averaged comparisons between closure predictions and observations are made when anisotropy of the underlying topography is accounted for the two horizontally averaged closure predictions near the seafloor are approximately equal the dissipation associated with topographic blocking is predicted by the garner 2005 scheme to account for the majority of the depth integrated dissipation over the bottom 1000 m of the water column where the horizontally averaged predictions lie well within the spatial variability of the horizontally averaged observations simplifications made by the garner 2005 scheme that are inappropriate for the oceanic context together with imperfect observational information can partially account for the prediction observation disagreement particularly in the upper water column

surface quasigeostrophic solutions and baroclinic modes with exponential stratification abstractthe author derives baroclinic modes and surface quasigeostrophic sqg solutions with exponential stratification and compares the results to those obtained with constant stratification the sqg solutions with exponential stratification decay more rapidly in the vertical and have weaker near surface velocities this then compounds the previously noted problem that sqg underpredicts the velocities associated with a given surface density anomaly the author also examines how the sqg solutions project onto the baroclinic modes with constant stratification sqg waves larger than deformation scale project primarily onto the barotropic mode and to a lesser degree onto the first baroclinic mode however with exponential stratification the largest projection is on the first baroclinic mode the effect is even more pronounced over rough bottom topography therefore large scale sqg waves will look like the first baroclinic mode and vice versa with realistic stratification

diagnosing the energy cascade in a model of the north atlantic spectral potential and kinetic energy densities and fluxes in horizontal wavenumber space are estimated in an eddy resolving model of the north atlantic in agreement to recent observational results near surface kinetic energy fluxes are negative over wide regions of the north atlantic indicative of an inverse energy cascade this inverse kinetic energy cascade is found over a wide depth range but both the spectral kinetic energy density and the corresponding flux show no clear dependency on rossby radius or rhines scale potential energy fluxes tend to be positive and show a direct potential energy cascade towards a scale which is related to the rossby radius in the subtropical north atlantic

impact of horizontal resolution 1 12 to 1 50 on gulf stream separation penetration and variability abstractthe impact of horizontal resolution 1 12 to 1 50 6 to 1 5 km at midlatitudes on gulf stream separation penetration and variability is quantified in a series of identical north atlantic experiments the questions the authors seek to address are twofold 1 is the realism of the modeled solution increased as resolution is increased 2 how robust is the modeled mesoscale and submesoscale eddy activity as a function of grid spacing and how representative is it of interior quasigeostrophic qg or surface quasigeostrophic sqg turbulence this study shows that i the representation of gulf stream penetration and associated recirculating gyres shifts from unrealistic to realistic when the resolution is increased to 1 50 and when the nonlinear effects of the submesoscale eddies intensifies the midlatitude jet and increases its penetration eastward ii the penetration into the deep ocean drastically increases with resolution and closely resembles the observations and iii surface power spec

characterization of surface heterogeneity detected at the misr terra subpixel scale vegetation structure can have a significant impact on the degree of anisotropy in the reflected radiation field with the appropriate characterization of these effects the analysis of multiangular data such as provided by the multi angle imaging spectroradiometer misr instrument on board terra can yield statistical information about the type of surface heterogeneity that exists at the subpixel scale

simulations of underwater plumes of dissolved oil in the gulf of mexico 1 a simple model of the temperature dependent biological decay of dissolved oil is embedded in an ocean climate model and used to simulate underwater plumes of dissolved and suspended oil originating from a point source in the northern gulf of mexico with an upper bound supply rate estimated from the contemporary analysis of the deepwater horizon blowout the behavior of plumes at different depths is found to be determined by the combination of sheared current strength and the vertical profile of decay rate for all plume scenarios toxic levels of dissolved oil remain confined to the northern gulf of mexico and abate within weeks after the spill stops an estimate of oxygen consumption due to microbial oxidation of hydrocarbons suggests that a deep plume of hydrocarbons could lead to localized regions of prolonged hypoxia near the source but only when oxidation of methane is included

radiation and dissipation of internal waves generated by geostrophic motions impinging on small scale topography application to the southern ocean abstract recent estimates from observations and inverse models indicate that turbulent mixing associated with internal wave breaking is enhanced above rough topography in the southern ocean in most regions of the ocean abyssal mixing has been primarily associated with radiation and breaking of internal tides in this study it is shown that abyssal mixing in the southern ocean can be sustained by internal waves generated by geostrophic motions that dominate abyssal flows in this region theory and fully nonlinear numerical simulations are used to estimate the internal wave radiation and dissipation from lowered acoustic doppler current profiler ladcp ctd and topography data from two regions in the southern ocean drake passage and the southeast pacific the results show that radiation and dissipation of internal waves generated by geostrophic motions reproduce the magnitude and distribution of dissipation previously inferred from finescale measurements in the region suggesting that it is one of the

global rate and spectral characteristics of internal gravity wave generation by geostrophic flow over topography the rate of generation of internal gravity waves in the lee of small length scale topography by geostrophic flow in the world ocean was estimated using linear theory with corrections for finite amplitude topography several global data sets were combined for the calculation including an ocean circulation model for the near bottom geostrophic flow statistics over 500 abyssal current meter records historical climatological data for the buoyancy frequency and two independent estimates of the small scale topographic statistical properties the first topography estimate was based on an empirically derived relationship between paleo spreading rates and abyssal hill roughness with corrections for sedimentation the second estimate was based on small scale 100 km roughness of satellite altimetry derived gravity field using upward continuation relationships to derive estimates of abyssal hill roughness at the seafloor at scales less than approximately 20 km the lee wave generation rate was found to be between 0 34 to 0 49 tw the southern hemisphere produced 92 of the lee wave energy with the southern ocean dominating strength of the bottom flow was the most important factor in producing the global pattern of generation rate except in the indian ocean where extremely rough topography produced strong lee wave generation despite only moderate bottom flows the results imply about one half of the mechanical power input to the ocean general circulation from the extra equatorial wind stress of the world ocean results from abyssal lee wave generation topographic length scales between 176 m and 2 5 km horizontal wavelengths between 1 and 16 km accounted for 90 of the globally integrated generation

cenozoic sequence stratigraphy of the kachchh basin india abstract the kachchh sedimentary basin in the western continental margin of india is a peri cratonic rift basin which preserves a nearly complete rock record from middle jurassic to recent punctuated by several stratigraphic breaks the cenozoic sediments exposed in the western part of the kachchh mainland extend offshore into the present day continental shelf the unique feature of the outcropping area is a nearly complete richly fossiliferous and easily accessible cenozoic succession detailed field mapping and litho biostratigraphic studies have made it possible to identify the chronostratigraphic units map them in the field and extend the correlation into the offshore aided by the development of continuously recognizable key biostratigraphic horizons and time boundaries detailed field mapping of key sections integrated with the litho biostratigraphic information has helped in working out a sequence stratigraphic framework for the cenozoic succession in the basin the succession comprises a first order passive margin sequence excellent biostratigraphic control has enabled identification of unconformities of various magnitudes which in turn have helped in mapping 5 second order and four third order sequences each sequence is discussed with respect to its extent nature of sequence boundaries sedimentary fill key sequence stratigraphic surfaces and depositional setup to understand the cenozoic sequence stratigraphic architecture of the basin

global abyssal mixing inferred from lowered adcp shear and ctd strain profiles abstract internal wave wave interaction theories and observations support a parameterization for the turbulent dissipation rate e and eddy diffusivity k that depends on internal wave shear vz2 and strain z2 variances its latest incarnation is applied to about 3500 lowered adcp ctd profiles from the indian pacific north atlantic and southern oceans inferred diffusivities k are functions of latitude and depth ranging from 0 03 10 4 m2 s 1 within 2 of the equator to 0 4 0 5 10 4 m2 s 1 at 50 70 diffusivities k also increase with depth in tropical and subtropical waters diffusivities below 4500 m depth exhibit a peak of 0 7 10 4 m2 s 1 between 20 and 30 latitudes where semidiurnal parametric subharmonic instability is expected to be active turbulence is highly heterogeneous though the bulk of the vertically integrated dissipation e is contributed from the main pycnocline hotspots in e show some correlation with small scale bottom roughness and near bottom flow at sites where st

generation of internal waves in the deep ocean by tides 1 a direct computation of the tidal generation of internal waves over the global ocean is presented it is based on linear wave theory and high resolution data for the bottom topography the geographical distribution of the energy flux from tides to internal waves is determined with a spatial resolution of a few kilometers the total flux over the area with a depth greater than 500 m is found to be 1 2 tw the greatest uncertainties of the computation are due to unresolved topography and to nonlinear effects caused by supercritical bottom slope

spectral energy fluxes in geostrophic turbulence implications for ocean energetics abstract the energy pathways in geostrophic turbulence are explored using a two layer flat bottom f plane quasigeostrophic model forced by an imposed horizontally homogenous baroclinically unstable mean flow and damped by bottom ekman friction a systematic presentation of the spectral energy fluxes the mean flow forcing and dissipation terms allows for a comprehensive understanding of the sources and sinks for baroclinic and barotropic energy as a function of length scale the key new result is a robust inverse cascade of kinetic energy for both the baroclinic mode and the upper layer this is consistent with recent observations of satellite altimeter data over the south pacific ocean the well known forward cascade of baroclinic potential and total energy was found to be very robust decomposing the spectral fluxes into contributions from different terms provided further insight the inverse baroclinic kinetic energy cascade is driven mostly by an efficient interaction between the baroclinic velo

suppression of internal wave breaking in the antarctic circumpolar current near topography abstractsimultaneous full depth microstructure measurements of turbulence and finestructure measurements of velocity and density are analyzed to investigate the relationship between turbulence and the internal wave field in the antarctic circumpolar current these data reveal a systematic near bottom overprediction of the turbulent kinetic energy dissipation rate by finescale parameterization methods in select locations sites of near bottom overprediction are typically characterized by large near bottom flow speeds and elevated topographic roughness further lower than average shear to strain ratios indicative of a less near inertial wave field rotary spectra suggesting a predominance of upward internal wave energy propagation and enhanced narrowband variance at vertical wavelengths on the order of 100 m are found at these locations finally finescale overprediction is typically associated with elevated froude numbers based on the near bottom shear of the background flow and a background flow with a

submesoscale vortical wakes in the lee of topography abstractan idealized framework of steady barotropic flow past an isolated seamount in a background of constant stratification with frequency n and rotation with coriolis parameter f is used to

global estimates of seafloor slope from single beam ship soundings 1 rough topography on the ocean floor is a source of ocean mixing which is of interest to both physical oceanography and climate science most mixing has been attributed to high slopes of the large scale structures of the deep ocean floor such as seamounts continental margins and mid ocean ridge axes in this paper we show the small scale but ubiquitous abyssal hills and fracture zones dominate the global map of rough topography much of this rugged seafloor occurs in the southern ocean on the flanks of the pacific antarctic rise and southwest indian ridge we present our results as a global map of the mean slope of the ocean floor and as a global map of the ocean floor above them2 critical slope we compare our results to multibeam and satellite bathymetry data to show that satellite bathymetry is not a valid proxy for multibeam measurements but edited single beam sonar data are adequate to provide a global perspective on features with horizontal wavelengths as small as 2 km

stochastic modeling of seafloor morphology inversion of sea beam data for second order statistics at scale lengths less than 100 km or so statistical descriptions of seafloor morphology can be usefully employed to characterize ridge crest processes off ridge tectonics and vulcanism sedimentation and postdepositional transport we seek to develop methods for the estimation of seafloor statistics that take into account the finite precision resolution and sampling obtained by actual echo sounding systems in this initial paper we restrict our attention to the problem of recovering second order statistics from data sets collected by multibeam devices such as sea beam the seafloor is modeled as a stationary zero mean gaussian random field completely specified by its two point covariance function we introduce an anisotropic two point covariance function that has five free parameters describing the amplitude orientation characteristic wave numbers and hausdorff fractal dimension of seafloor topography we formulate the general forward problem relating this model to the statistics of an ideal multibeam echo sounder in particular the along track autocovariance functions of individual beams and the cross covariance functions between beams of arbitrary separation using these second moments as data functionals we then pose the inverse problem of estimating the seafloor parameters from realistic noisy data sets with finite sampling and beamwidth and we solve this inverse problem by an iterative linearized least squares method the inversion method is applied to sea beam transit data from both the pacific and atlantic oceans sea beam system noise stands out as a sharp spike on the along track autocovariance function and can be modeled as a white noise process whose amplitude generally increases with beam angle the five parameters in our second order model can be estimated from the inversion of data sets comprising 100 200 km of track length in general the cross track wave number is the most poorly determined although uncertainties in the assumed sea beam response may bias the values of the fractal dimension using the assumed beamwidth the measured noise values and the seafloor parameters recovered from the inversion we generate sea beam synthetics whose statistical character can be directly compared with raw sea beam data for most of the track segments we have processed thus far the synthetics are similar to the data in the case of one atlantic profile however the comparison clearly indicates the necessity of incorporating higher order statistics the space domain procedures described in this paper can be extended for this purpose

eddies in the western arctic ocean from spaceborne sar observations over open ocean and marginal ice zones the western arctic ocean is a host to major ocean circulation systems many of which generate eddies that can transport water masses and corresponding tracers over long distances from their formation sites however comprehensive observations of critical eddy characteristics are currently not available and are limited to spatially and temporally sparse in situ observations here we use high resolution spaceborne synthetic aperture radar measurements to detect eddies from their surface imprints in ice free sea surface roughness and in sea ice patterns throughout marginal ice zones we provide the first estimate of eddy characteristics extending over the seasonally ice free and marginal ice zone regions of the western arctic ocean including their locations diameters and monthly distribution using available synthetic aperture radar data we identified over 4 000 open ocean eddies as well as over 3 500 eddies in marginal ice zones from june to october in 2007 2011 and 2016 eddies range in size between 0 5 and 100 km and are frequently found over the shelf and near continental slopes but also present in the deep canada basin and over the chukchi plateau we find that cyclonic eddies are twice more frequent compared to anticyclonic eddies at the surface distinct from the dominating anticyclonic eddies observed at depth by in situ moorings and ice tethered profilers our study supports the notion that eddies are ubiquitous in the western arctic ocean even in the presence of sea ice and emphasizes the need for improved ocean observations and modeling at eddy scales

regional tectonic framework structure and evolution of the western marginal basins of india abstract the kutch saurashtra cambay and narmada basins are pericontinental rift basins in the western margin of the indian craton these basins were formed by rifting along precambrian tectonic trends interplay of three major precambrian tectonic trends of western india dharwar nnw sse aravalli delhi ne sw and satpura ene wsw controlled the tectonic style of the basins the geological history of the basins indicates that these basins were formed by sequential reactivation of primordial faults the kutch basin opened up first in the early jurassic rifting was initiated in late triassic along the delhi trend followed by the cambay basin in the early cretaceous along the dharwar trend and the narmada basin in late cretaceous time along the satpura trend the evolution of the basins took place in four stages these stages are synchronous with the important events in the evolution of the indian sub continent its breakup from gondwanaland in the late triassic early jurassic its northward drifting during the jurassic cretaceous and collision with the asian continent in the early tertiary the most important tectonic events occurred in late cretaceous time the present style of the continental margins of india evolved during early tertiary time the saurashtra arch the extension of the aravalli range across the western continental shelf subsided along the eastern margin fault of the cambay basin during the early cretaceous it formed an extensive depositional platform continuous with the kutch shelf for the accumulation of thick deltaic sediments a part of the saurashtra arch was uplifted as a horst during the main tectonic phase in the late cretaceous the present high thermal regime of the cambay bombay high region is suggestive of a renewed rifting phase

seasonality of surface stirring by geostrophic flows in the bay of bengal abstract stirring of passive tracers in the bay of bengal driven by altimetry derived daily geostrophic surface currents is studied on subseasonal timescales to begin with hovmoller plots wavenumber frequency diagrams and power spectra confirm the multiscale nature of the flow advection of latitudinal and longitudinal bands highlights the chaotic nature of stirring in the bay via repeated straining and filamentation of the tracer field an immediate finding is that stirring is local i e of the scale of the eddies and does not span the entire basin further stirring rates are enhanced along the coast of the bay and are relatively higher in the pre and post monsoonal seasons indeed finite time lyapunov exponent ftle and finite size lyapunov exponent fsle maps in all the seasons are patchy with minima scattered through the interior of the bay further these maps bring out a seasonal cycle wherein rapid stirring progressively moves from the northern to southern bay during pre and post monsoonal periods respectively the non uniform stirring of the bay is reflected in long tailed probability density functions of ftles that become more stretched for longer time intervals quantitatively advection for a week shows the mean ftle lies between 0 13 0 07 day 1 while extremes reach almost 0 6 day 1 averaged over the bay relative dispersion initially grows exponentially followed by a power law at scales between approximately 100 and 250 km which finally transitions to an eddy diffusive regime quantitatively below 250 km a scale dependent diffusion coefficient is extracted that behaves as a power law with cluster size while above 250 km eddy diffusivities range from 6 10 3 1 6 10 4 m2s 1 in different regions of the bay these estimates provide a useful guide for resolution dependent diffusivities in numerical models that hope to properly represent surface stirring in the bay

uniqueness of multiangular measurements i an indicator of subpixel surface heterogeneity from misr the recent availability of quasi simultaneous multispectral and multidirectional measurements from space as provided by the multi angle imaging spectroradiometer misr on board the terra platform offers new and unique opportunities to document the anisotropy of land surfaces at critical solar wavelengths this paper presents simple physical principles supporting the interpretation of the anisotropy of spectral radiances exiting terrestrial surfaces in terms of a signature of surface heterogeneity the shape of the anisotropy function is represented with two model parameter values which may be mapped and interpreted in their own right the value of one of these parameters also permits identifying geophysical conditions where the surface heterogeneity becomes significant and where three dimensional 3d radiation transfer effects have to be explicitly accounted for this paper documents these findings on the basis of results from a number of 3d radiation transfer model simulations the latter are used to perform an extensive sensitivity study which includes issues related to the scale of investigation a preliminary validation of these results conducted with a dataset collected by the airmisr instrument over the konza prairie is also discussed

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

delineation of the 85 e ridge and its structure in the mahanadi offshore basin eastern continental margin of india ecmi from seismic reflection imaging abstract the passive eastern continental margin of india ecmi evolved during the break up of india and east antarctica in the early cretaceous the 85 e ridge is a prominent linear aseismic feature extending from the afanasy nikitin seamounts northward to the mahanadi basin along the ecmi earlier workers have interpreted the ridge to be a prominent hot spot trail in the absence of conclusive data the extension of the ridge towards its northern extremity below the thick bengal fan sediments was a matter of postulation in the present study interpretation of high resolution 2 d reflection data from the mahanadi offshore basin located in the northern part of the ridge unequivocally indicates continuation of the ridge across the continent ocean boundary into the slope and shelf tracts of the ecmi its morphology and internal architecture suggest a volcanic plume related origin that can be correlated with the activity of the kerguelen hot spot in the nascent indian ocean in the continental region the plume related volcanic activity appears to have obliterated all seismic features typical of continental crust the deeper oceanic crust over which the hot spot plume erupted shows the presence of linear ns aligned basement highs corresponding with the ridge underlain by a depressed moho discontinuity in the deep oceanic basin the ridge influences the sediment dispersal pattern from the early cretaceous early part of late cretaceous times till the end of oligocene which is an important aspect for understanding the hydrocarbon potential of the basin

radiation and dissipation of internal waves generated by geostrophic motions impinging on small scale topography theory abstract observations and inverse models suggest that small scale turbulent mixing is enhanced in the southern ocean in regions above rough topography the enhancement extends o 1 km above the topography suggesting that mixing is supported by the breaking of gravity waves radiated from the ocean bottom in this study it is shown that the observed mixing rates can be sustained by internal waves generated by geostrophic motions flowing over bottom topography weakly nonlinear theory is used to describe the internal wave generation and the feedback of the waves on the zonally averaged flow vigorous inertial oscillations are driven at the ocean bottom by waves generated at steep topography the wave radiation and dissipation at equilibrium is therefore the result of both geostrophic flow and inertial oscillations differing substantially from the classical lee wave problem the theoretical predictions are tested versus two dimensional high resolution numerical simulations with parameters representative of

on eddy viscosity energy cascades and the horizontal resolution of gridded satellite altimeter products motivated by the recent interest in ocean energetics the widespread use of horizontal eddy viscosity in models and the promise of high horizontal resolution data from the planned wide swath satellite altimeter this paper explores the impacts of horizontal eddy viscosity and horizontal grid resolution on geostrophic turbulence with a particular focus on spectral kinetic energy fluxes p k computed in the isotropic wavenumber k domain the paper utilizes idealized two layer quasigeostrophic qg models realistic highresolution ocean general circulation models and present generation gridded satellite altimeter data adding horizontal eddy viscosity to the qg model results in a forward cascade at smaller scales in apparent agreement with results from present generation altimetry eddy viscosity is taken to roughly represent coupling of mesoscale eddies to internal waves or to submesoscale eddies filtering the output of either the qg or realistic models before computing p k also greatly increases the forward cascade such filtering mimics the smoothing inherent in the construction of present generation gridded altimeter data it is therefore difficult to say whether the forward cascades seen in present generation altimeter data are due to real physics represented here by eddy viscosity or to insufficient horizontal resolution the inverse cascade at larger scales remains in the models even after filtering suggesting that its existence in the models and in altimeterdata is robust however themagnitudeofthe inverse cascadeis affectedbyfiltering suggestingthat the wide swath altimeter will allow a more accurate determination of the inverse cascade at larger scales as well as providing important constraints on smaller scale dynamics

anomalous chlorofluorocarbon uptake by mesoscale eddies in the drake passage region the role of mesoscale eddies in the uptake of anthropogenic chlorofluorocarbon 11 cfc 11 gas is investigated with a 1 20 eddy resolving numerical ocean model of a region of the southern ocean with a relatively fast air sea equilibrium time scale about a month the air sea cfc 11 flux quickly responds to the changes in the mixed layer cfc 11 partial pressure pcfc 11 at the mesoscale significant correlations are observed between pcfc 11 anomaly anomalies in sea surface temperature sst net heat flux and mixed layer depth an eddy centric analysis of the simulated cfc 11 field suggests that anticyclonic warm core eddies generate negative pcfc 11 anomalies and cyclonic cold core eddies generate positive anomalies of pcfc 11 surface pcfc 11 is modulated by mixed layer dynamics in addition to cfc 11 air sea fluxes a negative cross correlation between mixed layer depth and surface pcfc 11 anomalies is linked to higher cfc 11 uptake in anticyclones and lower cfc 11 uptake in cyclones especially in winter an almost exact asymmetry in the air sea cfc 11 flux between cyclones and anticyclones is found

spatial and seasonal variations of submesoscale eddies in the eastern tropical pacific ocean abstractthe spatial and seasonal variations of submesoscale eddy activities in the eastern tropical pacific ocean 2 12 n 95 165 w are investigated based on a 1 10 ocean general circulation model ogcm in the studied region it is found that motions shorter than 500 km are subject to submesoscale dynamics with an o 1 rossby number and richardson number and a 2 spectral slope for kinetic energy suggesting that submesoscale eddies there can be well resolved by the model enhanced submesoscale eddy kinetic energy smke is found in the surface mixed layer centered at 5 n a complete smke budget analysis suggests that the submesoscale eddies in the surface mixed layer are generated mainly by the barotropic instability and secondarily by the baroclinic instability the nonlinear interactions lead to a significant forward energy cascade in the submesoscale range and play an important role in balancing the energy budget as a response to the change of energy input through barotropic instability the sm

global observations of ocean bottom subinertial current dissipation quadratic bottom boundary layer drag is a potentially significant source of energy dissipation in the deep ocean this study presents a new estimate of the energy dissipated by this process using results from the world s largest archive of ocean current meter time series and focusing strongly upon the potential uncertainties in this calculation two methods are used one based on a simple division of the world ocean into a series of regular grids and the other based on a more sophisticated analysis using a hierarchical clustering mechanism assisted by estimates from the hybrid coordinate ocean model hycom model from these analyses the authors estimate a globally integrated bottom boundary layer dissipation of 0 65 6 0 15 statistical uncertainty 6 0 15 methodological uncertainty tw