atmospheric and oceanic forcing of weddell sea ice motion the data from sea ice buoys which were deployed during the winter weddell sea project 1986 the winter weddell gyre studies 1989 and 1992 the ice station weddell in 1992 the antarctic zone flux experiment in 1994 and several ship cruises in austral summers are uniformly reanalyzed by the same objective methods geostrophic winds are derived after matching of the buoy pressure data with the surface pressure fields of the european centre for medium range weather forecasts the ratio between ice drift and geostrophic wind speeds is reduced when winds and currents oppose each other when the atmospheric surface layer is stably stratified and when the ice is under pressure near coasts over the continental shelves the spatial inhomogeneity of tidal and inertial motion effectively controls the variability of divergence for periods below 36 hours far from coasts speed ratios which presumably reflect internal stress variations in the ice cover are independent of drift divergence on the spatial scale of 100 km to study basin scale ice dynamics all ice drift data are related to the geostrophic winds based on the complex linear model thorndike and colony 1982 for daily averaged data the composite patterns of mean ice motion geostrophic winds and geostrophic surface currents document cyclonic basin wide circulations geostrophic ocean currents are generally small in the weddell sea significant features are the coastal current near the southeastern coasts and the bands of larger velocities of 6 cm s 1 following the northward and eastward orientation of the continental shelf breaks in the western and northwestern weddell sea in the southwestern weddell sea the mean ice drift speed is reduced to less than 0 5 of the geostrophic wind speed and increases rather continuously to 1 5 in the northern central and eastern weddell sea the linear model accounts for less than 50 of the total variance of drift speeds in the southwestern weddell sea and up to 80 in the northern and eastern weddell sea

tidal forcing on sea ice drift and deformation in the western weddell sea in early austral summer 2004 abstract sea ice drift and deformation in the western weddell sea in early austral summer of 2004 are characterised using in situ data from a meso scale array of 24 drifting ice buoys horizontal gps derived position measurements are available from drifting buoys deployed as part of the ice station polarstern ispol experiment for 26 days during late november and december 2004 at various temporal resolutions and spatial accuracies these data form the basis for sea ice velocity and deformation measurements across the meso scale ispol array and at two remote sites analysis of the sea ice velocities reveals coherence for sea ice drift at separations of less than 70 km and a correlation length scale of 60 km within the limits of the ispol array at larger separations zonal ice drift remains correlated while meridional ice drift becomes uncorrelated this together with the east west gradient in ice velocities indicates the influence of bathymetry via tidal forcing on local dynamic processes atmospheric forcing also contributes to the sea ice drift about 40 of variability in the sea ice velocity is explained by changes in wind velocity which is significantly less than other studies have found for the region during winter sea ice deformation has been derived for the overall array and four sub arrays there appeared to be no spatial scale dependency of ice deformation although considerable spatial variability was observed between sub arrays the net divergence of the ispol array was in excess of 30 with the largest contributions to divergence being from the southern section and along the eastern side of the overall ispol array temporal variability for all deformation parameters is dominated by high frequency sub daily processes namely tidal forcing and inertial response low frequency multiple days processes including atmospheric changes played a secondary role in forcing sea ice deformation during ispol

late quaternary changes in antarctic bottom water velocity inferred from sediment grain size in the northern weddell sea abstract newly formed bottom water 0 7 c in the northern weddell sea flows e or ne at speeds up to 10 15 cm s with velocity decreasing towards the centre of the weddell gyre preliminary results from long term current meter moorings upper quaternary sediments from this area contain a fine grained terrigenous component from the nepheloid layer plus biogenic silica mostly diatoms with a small amount of ice rafted debris in cores from between 61 and 66 s and from 3300 m to 4700 m water depth the proportion of biogenic silica increases northwards corresponding to increasing seasonal extent of open water vs sea ice cover and the proportion of silt and well sorted fine sand in surface sediments increases with average current velocity downcore diatom rich and diatom poor sediments alternate on a scale of 1 3 m and intervals with more diatoms contain a higher proportion of silt to clay preliminary stratigraphy suggests the cyclicity in composition and texture is related to glacial interglacial cyclicity during warm periods indirectly correlated with isotope stages 1 3 5 etc biogenic silica production takes place during several months of each year and silt and fine sand are transported by bottom currents during glacial periods with greater sea ice cover than at present biogenic productivity was suppressed and no silica was preserved in the sediments in addition a lower proportion of terrigenous silt implies that bottom currents were weaker at sites with a present day average velocity of 10 cm s a last glacial maximum average velocity of 1 cm s or less is inferred from grain size measurements

pack ice drift off east antarctica and some implications three satellite tracke d data buoys were deployed between 700 and 800e south of 65 os in february march 1985 these buoys were subsequently trapped within the expanding seasonal sea ice and drifted with the ice the buoys measured air temperature and pressure and water temperatures to 100 m depth data from the buoys are used to describe the ice drift and environment within the winter sea ice zone in this region both north and south of the antarctic divergence additional preliminary data from a further six buoys deployed in the same area in march 1987 are also presented besides providing information on the broad scale drift of the ice in the prydz bay region data from the buoys have shown i the important role that ice drift plays in determining the autumn and winter expansion of antarctic sea ice ii the highly mobile nature of the ice even hundreds of kilometres from the ice edge iii the role that ocean bottom topography has in determining ice drift over the continental shelf and iv the modifying influence that an ice cover has on regional climate a qualitative assessment is made of importance of the major forces driving the ice data are insufficient for a detailed study dynamics

sea ice motion in the weddell sea from drifting buoy and avhrr data a study of sea ice in the northern weddell sea was done relating the ice motion determined using an array of satellite tracked drifters deployed into ice floes to parameters describing the nature of the ice cover obtained from an analysis of advanced very high resolution radiometer avhrr imagery it was found that the ice motion was predominantly wind driven responding to the passage of low pressure systems across the area the correlation length of the strain field over the entire measurement period was around 200 km at high concentrations the ice responded as a rigid body with coherent motion but below a concentration of around 93 differential motion occurred the nature of the ice motion was found to depend upon the lead parameters with low values of pure convergence and divergence and larger values of vorticity and deformation of the ice field the vorticity was found to be well correlated with the atmospheric pressure with a time lag of less than 3 h implying an almost instantaneous response of the ice cover to meteorological forcing

role of off shelf to on shelf transitions for east antarctic sea ice dynamics during spring 2003 1 during austral spring 2003 mesoscale sea ice drift and deformation off east antarctica were investigated using in situ data from a nine buoy array upon deployment the array comprised an area of about 4000 km2 with a mean ice concentration of 96 half hourly sea ice velocities were coherent across all buoys at zonal meridional separations of less than 160 km 70 km regional cross spectral correlation was high at synoptic scales and also at semidiurnal periods off the continental shelf atmospheric synoptic scale forcing explained in excess of 85 of the ice drift variability this is significantly more than found in the weddell sea where significant ice drift variability is derived from oceanic forcing peak frequencies of semidiurnal contributions covaried with latitude and are largely associated with the inertial response over the continental shelf coincident diurnal and semidiurnal variances in ice motion arose from tidal forcing net divergence over 37 days resulted in an expansion to 270 of the initial area although regional ice concentration reduced only slightly high frequency processes namely inertial response and to a lesser degree tidal forcing dominated the variability of all deformation parameters in contrast to ice motion low frequency processes played a secondary role in sea ice deformation this high frequency dominance is similar to what has been found in the weddell sea although many observations there were limited to the continental shelf where tidal processes dominate sea ice motion and deformation were not affected by a seasonal transition nor did the regional ice characteristics show any signal of seasonal change instead local ice dynamics were strongly influenced by bathymetrically dependent processes

surface circulation at the tip of the antarctic peninsula from drifters an array of 40 surface drifters drogued at 15 m depth was deployed in february 2007 to the east of the tip of the antarctic peninsula as part of the antarctic drifter experiment links to isobaths and ecosystems adelie project data obtained from these drifters and from a select number of local historical drifters provide the most detailed observations to date of the surface circulation in the northwestern weddell sea the antarctic slope front asf characterized by a 20 cm s 1 current following the 1000 m isobath is the dominant feature east of the peninsula the slope front bifurcates when it encounters the south scotia ridge with the drifters following one of three paths drifters i are carried westward into bransfield strait ii follow the 1000 m isobath to the east along the southern edge of the south scotia ridge or iii become entrained in a large standing eddy over the south scotia ridge drifters are strongly steered by contours of f h coriolis frequency depth as shown by calculations of the first two moments of displacement in both geographic coordinates and coordinates locally aligned with contours of f h an eddy mean decomposition of the drifter velocities indicates that shear in the mean flow makes the dominant contribution to dispersion in the along f h direction but eddy processes are more important in dispersing particles across contours of f h the results of the adelie study suggest that the circulation near the tip of the antarctic peninsula may influence ecosystem dynamics in the southern ocean through antarctic krill transport and the export of nutrients

geostatistical seismic amplitude versus angle inversion seismic inversion plays an important role in reservoir modelling and characterization due to its potential for assessing the spatial distribution of the subsurface petro elastic properties seismic ava inversion methodologies allow to retrieve p wave and s wave velocities and density individually allowing a better characterization of existing litho fluid facies we present an iterative geostatistical seismic ava inversion algorithm that inverts pre stack seismic data sorted by angle gather directly for density p wave and s wave velocity models the proposed iterative geostatistical inverse procedure is based on the use of stochastic sequential simulation and co simulation algorithms as the perturbation technique of the model parameter space and the use of a genetic algorithm as a global optimizer to make the simulated elastic models converge from iteration to iteration all the elastic models simulated during the iterative procedure honour the marginal prior distributions of p wave velocity s wave velocity and density estimated from the available well log data and the corresponding joint distributions between density versus p wave velocity and p wave versus s wave velocity we successfully tested and implemented the proposed inversion procedure on a pre stack synthetic dataset built from a real reservoir and on a real pre stack seismic dataset acquired over a deep water gas reservoir in both cases the results show a good convergence between real and synthetic seismic and reliable high resolution elastic subsurface earth models this article is protected by copyright all rights reserved

computer simulation of transport and deposition of the campanian y 5 ash analyses of grain size and modal composition of the campanian tuff ash layer y 5 from 11 deep sea cores have been carried out this layer represents ash fall that has been correlated with the 38 000 y b p campanian ignimbrite thunell et al 1979 a deposit formed by the largest eruption documented in the mediterranean region during the late pleistocene barberi et al 1978 the bulk deposit is bimodal in grain size and dominated by glass shards the calculated mean grain size of the coarse mode of the individual size distributions decreases with distance from the source and progressively approaches a near constant fine mode of approximately 13 microns distal samples are unimodal in grain size these data combined with a set of vertical profiles of wind 10 year average have been used as input to a computer model that simulates fallout of tephra modelling indicates that the downwind variation of grain size of the coarse mode can be accurately reproduced with transport of ash between 5 and 35 km the observed fine mode of the deposit cannot however be generated by transport of ash as individual particles at these elevations such transport would result in deposition of virtually all of the fine ash beyond the studied area deposition of fine ash within the studied distance of 1600 km from source can only occur by fallout as particle aggregates from a high eruption plume or as individual particles from co ignimbrite ash clouds with a maximum elevation of 3 km the large volume of ash in the fine mode 70 wt and the irregularity in azimuth of low level winds argue against major low level transport of co ignimbrite ash rather the ash may have been derived from both a plinian eruption column and high altitude clouds of co ignimbrite ash with settling of fine ash as particle aggregates

observations of sea ice ridging in the weddell sea sea ice surface topography data were obtained by helicopter borne laser profiling during the first finnish antarctic expedition finnarp 89 the measurements were made near the ice margin at about 73 s 27 w in the eastern weddell sea on december 31 1989 and january 1 1990 five transects ranging in length from 127 to 163 km and covering a total length of 724 km are analyzed with a lower cutoff of 0 91 m the overall ridge frequency was 8 4 ridges km and the average ridge height was 1 32 m the spatial variations in ridging were large for 36 individual 20 km segments the frequencies were 2 16 ridges km and the mean heights were 1 16 1 56 m the frequencies and mean heights were weakly correlated the distributions of the ridge heights followed the exponential distribution the spacings did not pass tests for either the exponential or the lognormal distribution but the latter was much closer in the 20 km segments the areally averaged thickness of ridged ice was 0 51 0 28 m ranging from 0 10 to 1 15 m the observed ridge size and frequency are greater than those known for the ross sea compared with the central arctic the weddell sea ridging frequencies are similar but the ridge heights are smaller possibly as a result of differences in snow accumulation

seismic inversion combining rock physics and multiple point geostatistics a novel inversion technique combines rock physics and multiple point geostatistics the technique is based on the formulation of the inverse problem as an inference problem and incorporates multiple point geostatistics and conditional rock physics to characterize previously known geologic information the proposed implementation combines elements of sampling from conditional probabilities and elements of optimization the technique provides multiple solutions all consistent with the expected geology well log data seismic data and the local rock physics transformations a pattern based algorithm was selected as the multiple point geostatistics component rock physics principles are incorporated at the beginning of the process defining the links between reservoir properties e g lithology saturation and physical quantities e g compressibility density making it possible to predict situations not sampled by log data results for seismic lithofacies inversion on a synthetic test and a real data application demonstrate the validity and applicability of the proposed inversion technique

weddell sea ice drift kinematics and wind forcing ice drift in the weddell sea was studied on the basis of positional and meteorological data from argos buoys drifting in 1990 1992 and surface pressure analyses from the european centre for medium range weather forecasts ecmwf the drift kinematics showed differences between the eastern and western parts of the weddell sea close to the antarctic peninsula the ice drifted as an almost nonrotating uniform field at a low speed having reduced small scale motions with little meandering compared to regions further to the east inertial motion was detected from the ice drift in areas east of 35 w and in the region of the antarctic circumpolar current on timescales of days wind was the primary forcing factor for the drift a linear model between the wind and ice drift explained 40 80 of the drift velocity variance the degree of explanation was higher in the central weddell sea around 40 w and lower closer to the antarctic peninsula the geostrophic wind was found to provide almost as good a basis for the general drift estimation as the surface wind observed by the buoys although strong cyclones were not well detected by the ecmwf analyses the data suggest a dependency upon atmospheric stability such that stable stratification reduces the wind forcing on the drift for 60 80 of the time the direction of the drift deviated less than 45 from the geostrophic wind and for 45 70 of the time less than 45 from the ocean current ice transport through a transect crossing the weddell sea from the antarctic peninsula tip to kapp norwegia was estimated on the basis of the geostrophic winds the drift s observed response to the wind and literature based information on ice concentration and thickness the estimated annual mean net export in 1992 1994 varied from 8000 to 22 000 m3 s most of the net export took place in winter and spring export prevailing west of 35 w and import east of it

plinian pumice fall deposit of the campanian ignimbrite eruption phlegraean fields italy abstract a plinian pumice fall deposit associated with the campanian ignimbrite eruption 36 ka phlegraean fields caldera italy occurs at the base of the distal grey ignimbrite in 15 localities spread over an area exceeding 1500 km2 between benevento and the sorrentina peninsula in the thickest stratigraphic section at voscone 130 cm 45 km east of the phlegraean caldera centre pozzuoli the deposit consists of two units the lower fall unit lfu is well sorted exhibits reverse size grading and is composed of equidimensional light grey pumice clasts with very subordinate accidental lithics the upper fall unit ufu is from well to poorly sorted crudely stratified richer in lithics and composed of both equidimensional and prolate pumice clasts the two fall units show slightly different dispersal axis n90 for the lfu and n95 for the ufu volumes calculated with the method of pyle 1989 are about 8 km3 for the lfu and 7 km3 for the ufu the maximum height of the eruptive columns are estimated using the model of the maximum lithic clasts dispersal at 44 km for the lfu and 40 km for the ufu classifying both fall units as ultraplinian in character reverse size grading within the lfu suggests an increase of the height of the column and magma discharge rate with time moderate sorting and crude stratification of the ufu are consistent with short period oscillation of the column possibly associated with repeated partial column collapses sharp increases in lithic content at the transition to ufu and within the ufu suggest that changes in the eruptive behaviour was produced by a dramatic increase in conduit vent erosion the phase of column instability preceded the emplacement of widely dispersed pyroclastic flow the ultraplinian nature of the fall fits well with the wide dispersal of the campanian ignimbrite with an estimated aspect ratio of 3 4 10 4 lari

observing the advection of sea ice in the weddell sea using buoy and satellite passive microwave data this study examines the progress and behavior of an area of sea ice as it drifts from the southwestern weddell sea by using data from four buoys tracked by nimbus 6 and concurrent ice concentrations retrieved from nimbus 7 scanning multichannel microwave radiometer data it covers the entire growth season of 1980 the overall drift characteristics and their relationship to ice edge displacement are examined within the framework of four zones three phases are identified in the large scale behavior of the weddell sea ice cover namely a rapid equatorward and eastward advance a quasi equilibrium phase and a period of rapid recession a broad division is made between the sectors to the east and west of 35 40 w in terms of the nature of ice edge advance transient departures from the mean northward advection are linked to the passage of cyclones certain such events may be significant in terms of the formation and maintenance of the region of highly consolidated perennial ice observed in the western weddell sea mean daily drift rates up to 0 9 m s 1 from within the central western weddell pack are high in 1980 particularly early in the growth season and when compared with rates to the west of 50 w outbreaks of cold continental air alternate with incursions of relatively warm air from the north warm conditions are recorded as far as 1200 km in from the ice edge in winter closed loops in the buoy trajectories which are clockwise to the south of 63 s reverse to become anticlockwise to the north mid ocean islands impede the eastward progress of the ice a coherence is noted in the response of the buoys to the passage of storms even though the buoys separated by a distance of over 100 km

ecosystem impact of the campanian ignimbrite eruption in late pleistocene europe the dating of the campanian ignimbrite ci eruption to 37 000 cal yr b p draws attention to the coincidence of this volcanic catastrophe and the suite of coeval late pleistocene biocultural changes that occurred within and outside the mediterranean region these included the middle to upper paleolithic cultural transition and the supposed change from neanderthal to modern homo sapiens anatomy a subject of sustained debate no less than 150 km3 of magma were extruded in the ci eruption the signal of which can be detected in greenland ice cores as widespread discontinuities in archaeological sequences are observed at or following the ci event a significant interference with ongoing human processes in mediterranean europe is hypothesized

response of the weddell sea pack ice to wind forcing sea ice drift in the weddell sea was studied on the basis of data from seven buoys deployed on ice floes in january february 1996 six of the buoys formed an array with initial mutual distances of 50 km which by october 1996 were stretched to 400 km in an east west direction the differential kinematical parameters i e divergence shearing rate and vorticity were estimated from the buoy array positions by applying a time dependent method the large scale drift of the array was divergent until august 1996 but after the array came under the influence of the antarctic circumpolar current the deformation was mainly shearing meteorological data from european centre for medium range weather forecasts analyses and special sensor microwave imager derived ice concentrations were interpolated at the buoy sites the drift velocity was highly wind dependent it was also wind dependent in winter when the momentum balance was mainly between the internal ice stress and the air drag the drift divergence and shearing rate were related to the wind forcing while the array vorticity correlated better with the air pressure itself we estimated the air ice drag coefficient to be 1 8 10 3 at a height of 10 m over the ice and the geostrophic drag coefficient to be 6 1 10 4 the stability effects on the coefficients were mostly felt in conditions of light winds the average ice water drag coefficient based on 5 day periods was 2 1 10 3 the ice transport through a transect crossing the weddell sea was computed on the basis of the geostrophic winds observed wind drift dependence ssm i derived ice concentrations and the literature on ice draft statistics the resulting annual mean net export in 1996 was 1600 km3 yr 1

stochastic inversion of prestack seismic data using fractal based initial models in general inversion algorithms rely on good starting models to produce realistic earth models a new method based on a fractional gaussian distribution derived from the statisticalparametersofavailablewelllogstogeneraterealistic initial models uses fractal theory to generate these models whensuchfractal basedinitialmodelsestimatep andsimpedance profiles in a prestack stochastic inversion of seismic angle gathers very fast simulated annealing a global optimization method finds the minimum of an objective function that minimizes data misfit and honors the statistics derivedfromwelllogs thenewstochasticinversionmethod addresses frequencies missing because of band limitation of the wavelet it combines the low and high frequency variation from well logs with seismic data this method has been implemented successfully using real prestack seismic data andresultshavebeencomparedwithdeterministicinversion models derived by a deterministic inversion are devoid of high frequency variations in the well log however models derived by stochastic inversion reveal high frequency variationsthatareconsistentwithseismicandwell logdata

integration of well data into geostatistical seismic amplitude variation with angle inversion for facies estimation abstractwe have developed a new iterative geostatistical seismic amplitude variation with angle ava inversion algorithm that inverts prestack seismic data sorted by angle gathers directly for high resolution density p wave velocity s wave velocity and facies models this novel iterative geostatistical inverse procedure is based on two key main principles the use of stochastic sequential simulation and cosimulation as the perturbation technique of the model parameter space and a global optimizer based on a crossover genetic algorithm to converge the simulated earth models toward an objective function in this case the mismatch between the recorded and synthetic prestack seismic data as a geostatistical approach all the elastic models simulated during the iterative procedure honors the well log data at its own locations the marginal prior distributions of p wave velocity and s wave velocity and density estimated from the available well log data and the corresponding joint distributions between

modeling the high frequency component of arctic sea ice drift and deformation abstract buoy observations of sea ice drift show that sea ice motion and deformation contain substantial high frequency variability at subdaily timescales however numerical simulations of the sea ice dynamics normally do not include processes on such short timescales instead by applying traditional water drag formulations for the ocean sea ice boundary layer the inertial frequencies tend to be omitted in the spectra of modeled sea ice motion and deformation due to fictitious ocean damping here a dynamic thermodynamic sea ice model is presented that includes inertial embedding of the sea ice into the oceanic boundary layer to reproduce sea ice motion and deformation not only at daily and lower frequencies but also at subdaily frequencies up to 2 cycles per day and higher comparison with buoy data shows that the embedded model much more successfully simulates the observed sea ice motion in regard to the high frequency component the results demonstrate that both inertial embedding of the sea ice oc

wind forcing and ice motion in the weddell sea region the wind forcing on the ocean surface and temporal and spatial characteristics of ice motion are analyzed from data of automatic buoy stations drifting for 14 months on ice floes in the weddell sea generally fluctuations with periods from 2 to 5 days which are caused by synoptic scale atmospheric wind fields primarily contribute to the variance of ice drift peaks in the spectra of ice motion are also found at 12 hours due to inertial motion and weak tidal effects which are nearly coincident in this geographical region inertial motion is only missing in winter when the ice concentration is high in the western branch of the weddell gyre semidiurnal peaks are stronger over the continental shelf than over the deep ocean diurnal peaks are weaker than semidiurnal peaks they are found over the continental shelf and are missing over the deep ocean at the same time the tidal motion reflects non wind related coupling between water and ice motion for periods of 1 2 to 1 day the integral length scales of ice motion are between 550 and 680 km longitudinal correlation and between 360 and 540 km lateral correlation respectively when the ice concentration exceeds eight tenths in the marginal ice zone the lateral length scale of ice motion is reduced to 270 km the integral length scales of air pressure fields exceed the length scales of ice motion by a factor of at least 1 5 longitudinal and lateral length scales of ice motion in the weddell sea are slightly smaller than those published for the beaufort sea where the ice moves within a basin of similar diameter of approximately 1500 km the smaller scales in the weddell sea presumably are due to differences of the forcing fields about 70 to 95 of the variance of 12 hourly averaged drift velocities can be linearly related to the wind velocity except when the mean wind speed drops below 3 5 m s the correlation with geostrophic winds is close to that with locally measured winds the twelve hourly averaged ice drift amounts to about 3 5 of the actual surface wind velocity at a height of 3 m or to about 1 6 of the geostrophic wind velocity derived from surface pressure analyses the drift geostrophic wind ratio is 30 smaller in central winter with ice concentrations above nine tenths in the central weddell sea than during summer periods when the buoys are closer to the coast in the periphery of the gyre and in the marginal ice zone the drift local wind ratio scatters more than the drift geostrophic wind ratio the ice drift in winter for ice concentrations above eight tenths on an average is deflected by 20 degrees to the left of the surface wind direction and is parallel to the isobars in summer under reduced ice concentrations it deviates by 40 degrees to the left of the surface wind and by 10 to 15 degrees to the left of the geostrophic wind for periods of 1 month the ice drift is also linearly well correlated to geostrophic wind velocity winds in the weddell sea usually do not average out over longer time scales ocean currents are too weak to dominate mean ice motion

geostatistical inversion of prestack seismic data for the joint estimation of facies and impedances using stochastic sampling from gaussian mixture posterior distributions abstractwe have developed a seismic inversion method for the joint estimation of facies and elastic properties from prestack seismic data based on a geostatistical approach the objectives of our inversion methodology are to sample from the posterior distribution of seismic properties and to simultaneously classify the lithology conditioned by seismic data the inversion algorithm is a sequential gaussian mixture inversion based on bayesian linearized amplitude variation with offset inverse theory and sequential geostatistical simulations the stochastic approach to the inversion allows generating multiple elastic models that match the seismic data to mathematically represent the multimodal behavior of elastic properties due to their variations within different lithologies we adopt a gaussian mixture distribution for the prior model of the elastic properties and we use the prior probability of the facies as weights of the gaussian components of the mixture the solution of the inverse problem is achieve

bayesian wavelet estimation from seismic and well data a bayesian method for wavelet estimation from seismic and well data is developed the method works both on stacked data and on prestack data in form of angle gathers the seismic forward model is based on the convolutional model where the reflectivity is calculated from the well logs possible misties between the seismic traveltimes and the time axis of the well logs errors in the log measurements and seismic noise are included in the model the estimated wavelets are given as probability density functions such that uncertainties of the wavelets are an integral part of the solution the solution is not analytically obtainable and is therefore computed by markov chain monte carlo simulation an example from sleipner field shows that the estimated wavelet has higher amplitude compared to wavelet estimation where well log errors are neglected and the uncertainty of the estimated wavelet is lower

joint avo inversion wavelet estimation and noise level estimation using a spatially coupled hierarchical bayesian model the main objective of the avo inversion is to obtain posterior distributions for p wave velocity s wave velocity and density from specified prior distributions seismic data and well log data the inversion problem also involves estimation of a seismic wavelet and the seismic noise level the noise model is represented by a zero mean gaussian distribution specified by a covariance matrix a method for joint avo inversion wavelet estimation and estimation of the noise level is developed in a bayesian framework the stochastic model includes uncertainty of both the elastic parameters the wavelet and the seismic and well log data the posterior distribution is explored by markov chain monte carlo simulation using the gibbs sampler algorithm the inversion algorithm has been tested on a seismic line from the heidrun field with two wells located on the line the use of a coloured seismic noise model resulted in about 10 lower uncertainties for the p wave velocity s wave velocity and density compared with a white noise model the uncertainty of the estimated wavelet is low in the heidrun example the effect of including uncertainty of the wavelet and the noise level was marginal with respect to the avo inversion results

weddell sea iceberg drift five years of observations since 1999 52 icebergs have been tagged with gps buoys in the weddell seato enable monitoring of their position the chosen icebergs were of small tomedium size with a few icebergs larger than 10 km associatedwith the calving of icebergs a38 and a43 from the ronne ice shelf the majority of icebergs were tagged off neumayer station 8e 70s it was found that smaller bergs with edges shorter than 200 m had the shortestlife cycle 0 5 yr iceberg and thus freshwater export out of theweddell sea was found to be highly variable in one year the majority of buoysdeployed remained in the weddell sea constituting about 40 of the ncep p efreshwater input whereas in other years all of the tagged icebergs were exported the observed drifts of icebergs and sea ice showed a remarkably coherent motion the analysis of an iceberg sea ice buoy array in the western weddell seaand an iceberg array in the eastern weddell sea showed a coherent sea iceiceberg drift in sea ice concentrations above 86 dynamic kinematic parameter dkp during the course of coherent movement were low and deviations from the meancourse associated with the passage of low pressure system the length scale ofcoherent movement was estimated to be less than 250km about half the value found forthe arctic ocean

the breccia museo formation campi flegrei southern italy geochronology chemostratigraphy and relationship with the campanian ignimbrite eruption the breccia museo is one of the most debated volcanic formations of the campi flegrei volcanic district the deposit made up of six distinctive stratigraphic units has been interpreted by some as the proximal facies of the major caldera forming campanian ignimbrite eruption and by others as the product of several more recent independent and localized events new geochemical and chemostratigraphical data and ar ar age determinations for several units of the breccia museo deposits 39 ka correlate well with the campanian ignimbrite forming eruption the chemical zoning of the breccia museo deposits is interpreted here to be a consequence of a three stage event that tapped a vertically zoned trachytic magma chamber

sea ice transports in the weddell sea time series of sea ice draft in the weddell sea are evaluated together with hydrographic observations satellite passive microwave data and ice drift for estimation of the freshwater fluxes into and out of the weddell sea ice draft is measured with moored upward looking sonars since 1990 along two transects across the weddell gyre one transect extending from the tip of the antarctic peninsula to kapp norvegia was sampled between 1990 and 1994 and covers the flow into and out of the southern weddell sea the other transect sampled since 1996 and extending from the antarctic continent northward along the greenwich meridian covers the exchange of water masses between the eastern and the western weddell sea in order to relate results obtained during the different time periods empirical relationships are established between the length of the sea ice season derived from the satellite passive microwave data and defined as the number of days per year with the sea ice concentration exceeding 15 and 1 the annual mean ice draft and 2 the annual mean ice volume transport by using these empirical relationships estimates of annual mean ice drafts and ice volume transports are derived at all mooring sites for the period february 1979 through february 1999 wind and current force a westward ice transport in the coastal areas of the eastern weddell sea and a northward ice transport in the west during the 2 year period 1991 1992 the mean ice volume export from the weddell sea is 50 19 103 m3 s 1 this freshwater export is representative for a longer term 20 year mean and exceeds the average amount of freshwater gained by precipitation and ice shelf melt by about 19 103 m3 s 1 yielding an upper bound for the formation rate of newly ventilated bottom water in the weddell sea of 2 6 sv