a gulf stream model and an altimetry assimilation scheme a continuous data assimilation scheme and a multilayer primitive equation numerical model are described the model is an eddy resolving coastal ocean model that has been extended to include the gulf stream region it has complete thermohaline dynamics a bottom following sigma vertical coordinate system and a coastal following curvilinear orthogonal horizontal coordinate system calculated model fields are used to provide a model climatology and correlations between subsurface temperature and salinity anomalies and surface elevation anomalies an optimal interpolation method the surface to subsurface correlations and estimated model and data errors are the basis of the assimilation technique altimetry anomaly data extracted from the model calculations according to the geosat orbital schedule are used to test the assimilation scheme and to provide nowcasts and forecasts sensitivity studies are performed to test the effects of various parameters of the scheme it is found that the scheme is less efficient in the shallow continental shelf area than in the deeper regions of the model the results show significant nowcast skill with area averaged rms error for surface elevation and subsurface properties of about 40 50 of the corresponding error of the unassimilated case good forecast skill better than persistence is demonstrated for 10 20 days there is little skill after 30 40 days increasing the density of the satellite altimetry data especially by decreasing the separation distance between tracks should decrease the nowcast rms error to about 15 and improve the forecast

petrology and geochemistry of lava and ash erupted from volcan colima mexico during 1998 2005 abstract lava n 8 and bulk ash samples n 6 erupted between july 1999 and june 2005 were investigated to extend time series compositional and textural studies of the products erupted from volcan colima since 1869 in particular we seek to evaluate the possibility that the current activity will culminate in major explosive plinian style event similar to that in 1913 lava samples continue to show relatively heterogeneous whole rock compositions with some significant mafic spikes 1999 2001 as have prevailed since 1976 groundmass sio2 contents continue trends to lower levels that have prevailed since 1961 in the direction of the still lower groundmass sio2 contents found in 1913 scoriae importantly ash samples from investigated vulcanian style explosive eruptions in 2005 are devoid of particles with micro vesiculated groundmass textures such textures characterized the 1913 scoriae signifying expansion of in situ magmatic gas as the propellant of the 1913 eruption all magmas erupted since 1913 appear to have arrived in the upper volcanic conduit system in a degassed state the small to moderate vulcanian style explosive eruptions which have been common since 1999 16 000 events have blasted ash clouds as high as 11 km a s l and sent pyroclastic flows out to distances of 5 km these eruptions do not appear to be powered by expansion of in situ magmatic gas new small lava domes have been observed in the crater prior to many explosive eruptions these plugs of degassed lava may temporarily seal the conduit and allow the build up of magmatic gases streaming upward from below ahead of rising and degassing magma in this interpretation when gas pressure exceeds the strength of the plug seal in the upper conduit an explosive vulcanian style eruption occurs alternatively these explosive eruptions may represent interactions of hot rock and groundwater phreato magmatic

gulf stream trajectories measured with free drifting buoys abstract during 1975 78 35 free drifting buoys measured surface currents in the gulf stream region the buoy trajectories trace numerous paths of the stream and show that the stream is strongly influenced by the new england seamounts this influence is manifested as 1 a quasi permanent 100 km southeastward deflection of the stream and the frequent occurrence of a ring meander over the seamounts 2 large amplitude meanders beginning at the seamounts and extending eastward and 3 small 20 km diameter eddies which appear to be generated locally by individual seamounts a chart of the mean temperature field at a depth of 450 m agrees with several of the patterns seen in the buoy trajectories west of the seamounts the mean path of the gulf stream is eastward over the seamounts the path turns sharply northeastward and the isotherms in the stream abruptly diverge

growth of the lava dome and extrusion rates at soufriere hills volcano montserrat west indies 2005 2008 the third episode of lava dome growth at soufriere hills volcano began 1 august 2005 and ended 20 april 2007 volumes of the dome and talus produced were measured using a photo based method with a calibrated camera for increased accuracy the total dense rock equivalent dre volume of extruded andesite magma 306 51 mm3 was similar within error to that produced in the earlier episodes but the average extrusion rate was 5 6 0 9 m3s 1 dre higher than the previous episodes extrusion rates varied in a pulsatory manner from 0 5 m3s 1 to 20 m3s 1 on 18 may 2006 the lava dome had reached a volume of 85 mm3 dre and it was removed in its entirety during a massive dome collapse on 20 may 2006 extrusion began again almost immediately and built a dome of 170 mm3 dre with a summit height 1047 m above sea level by 4 april 2007 there were few moderate sized dome collapses 1 10 mm3 during this extrusive episode in contrast to the first episode of dome growth in 1995 8 when they were numerous the first and third episodes of dome growth showed a similar pattern of low 0 5 m3s 1 but increasing magma flux during the early stages with steady high flux after extrusion of 25 mm3

anticyclonic rings in the gulf of mexico abstract using the historical data set this study describes the anticyclonic rings that separated from the loop current in the eastern gulf of mexico six quasi synoptic data sets are used to describe the evolving circulation of the gulf of mexico from october 1966 to september 1967 showing the separation and movement into the western gulf of three anticyclonic rings the historical data are used to determine that these rings typically translate to the west at a mean speed of 2 1 km day 1 their length scale as defined by their rms radii is 183 km an estimate of ring life span as defined by an e folding time is one year within the context of the gulf s water property distributions these rings appear as warm salty bodies the heat and salt added by one of these rings after separation are estimated to be 7 109 j m 2 and 17 g cm 2 respectively the heat and salt added by one of these features play an important role in the heat and salt budget of the western gulf the latter indicates that about one r

a synthetic geoid validation of geosat mesoscale dynamic topography in the gulf stream region a validation study is carried out for the geosat altimeter in the gulf stream meander and ring region a synthetic geoid containing the medium scales of interest for mesoscale research is constructed by subtracting an independent estimate of the oceanographic mean dynamic topography from the altimetric sea surface the oceanographic mean dynamic topography which is concurrent with the altimetric mean is derived from a year of real time nowcasts and forecasts gulfcast based on assimilating a composite data set into a dynamical model using the synthetic geoid absolute dynamic topography from geosat and gulfcast for a year and 4 months in 1988 and 1989 compare very well in signal shape and feature locations sixteen cases of comparison of dynamic heights derived from axbts along geosat tracks in 1987 are made with geosat absolute topography the rms difference is less than 10 cm thus the comparison of these two independent data sets validates the altimeter and the synthetic geoid within the noise and error levels of the system

observations of gulf stream ring 83 e and their interpretation using feature models analysis techniques were developed to track and estimate the propagation velocity size shape orientation and swirl velocity of gulf stream warm core rings the methods involve fitting idealized warm core ring feature models to observed surface fronts in the satellite imagery to expendable bathythermograph survey data and to satellite tracked drifting buoy data the ring feature models are analytic structure functions with adjustable parameters in this case the ring is modeled as an isolated translating elliptic paraboloid with a swirl velocity that increases linearly with distance from the center use of the feature models is illustrated with data collected from warm core ring 83 e gradient currents based on the bathythermograph survey of ring 83 e and the feature model agree well with currents measured by expendable current profilers a comparison of the time series of ring 83 e feature model parameters indicates that not only is the feature model analysis of the buoy track an effective method for tracking and monitoring the evolution of gulf stream rings it also provides useful forecasts of ring locations based simply on a persisted propagation velocity these techniques were used to provide real time support for exploratory deepwater drilling operations off the u s east coast

estimation of marine shale methane adsorption capacity based on experimental investigations of lower silurian longmaxi formation in the upper yangtze platform south china abstract methane adsorption experiments were performed on eight lower silurian longmaxi moisture equilibrated shale samples from the upper yangtze platform south china at pressures up to 12 mpa at 20 c 40 c 60 c 80 c and 100 c to investigate the effects upon methane adsorption capacity and to estimate the variation of methane adsorption capacity as a function of depth and burial history the methane adsorption capacity of the longmaxi shale shows a significant positive correlation with total organic carbon toc content which is accompanied by an increase in bet brunauer emmett teller surface area and total pore volume a quadratic relationship was observed between clay content and methane adsorption capacity there is a threshold clay content 42 3 44 4 in this trend methane adsorption capacity declines with increasing clay content below the threshold and later increases with increasing clay content the langmuir pressure decreases exponentially with the reciprocal of temperature and the langmuir volume decreases linearly with temperature the isosteric heat of adsorption and standard entropy for the longmaxi shale ranges from 10 34 to 11 67 kj mol and from 57 04 to 61 32 j mol k respectively which are clustered around kerogen type i using these relationships a computational scheme was developed to calculate methane adsorption capacity as a function of toc content temperature and pressure based on the langmuir equation this algorithm was applied to estimate methane adsorption capacity of the longmaxi shale as a function of depth due to the dominating effect of pressure methane adsorption capacity increases initially with depth through a maximum and then decreases as a result of increasing temperature at a greater depth the maximum gas adsorption capacity is typically located at a depth range between 800 and 1350 m with toc content increasing the curves shift continuously towards higher adsorption capacity furthermore the maximum methane adsorption capacity moves higher and shifts to a deeper depth as toc content increases ultimately four principal dynamic evolutionary stages of methane adsorption capacity of the longmaxi shale over geologic time as a function of burial history were reconstructed

adsorption of methane carbon dioxide and their binary mixtures on jurassic shale from the qaidam basin in china abstract co 2 enhanced shale gas recovery which plays a crucial role in energy resource development involves the adsorption of binary mixtures of ch 4 and co 2 on shale while numerous previous studies have provided useful insight into ch 4 co 2 sorption characteristics on shale few studies have been conducted on binary mixtures absorption on shale to get better understanding in this field we carried out an experimental study using shale samples from the qaidam basin in china to investigate the adsorption mechanism of ch 4 and co 2 and their binary mixtures on shales and to evaluate the shale co 2 enhanced gas recovery potential in more details the results indicate that the co 2 sorption capacity exceeds that of the methane sorption by a factor of 4 for these shales the study also shows that in the adsorption system of the mixtures co 2 plays an advantageous role in the competitive adsorption process the shale exhibits various behaviors of preferential adsorption of co 2 which can be related to the shale pore structure maximum values of isosteric heat of adsorption for co 2 and ch 4 are found to be 17 7 kj mol and 12 6 kj mol respectively in addition our work denoted that the isosteric heat of adsorption for co 2 on shale samples increases with increasing adsorption capacity the study suggests that the co 2 enhanced gas recovery pattern can be feasible for shales in the qaidam basin

a double thermostad warm core ring of the gulf stream abstractan unusual double thermostad warm core ring of the gulf stream was discovered in the slope sea south of georges bank during the r v endeavor cruise 578 in may 2016 the ring s stratificat

water circulation and a cyclonic ring in the gulf stream splitting region in may june 1990 results of two hydrographical surveys of the area southeast of newfoundland where the gulf stream branches into the north atlantic current and the azores current are presented the surveys were carried out by the r vs vityaz and professor shtokman in may june 1990 as a part of the atlantex 90 experiment the process of detachment of a cyclonic meander and the appearance of a new extremely strong cyclonic ring are described thermohaline structure and local dynamics of the ring and the origin of its water mass are explored integral parameters describing the heat and salt content of the ring are defined and fluxes of heat and salt transferred across the subarctic front by such rings are estimated volume transport variations of the gulf stream are coupled with the appearance of the ring structure and variability of individual jets of the azores current and the north atlantic current and their interaction with the synoptic scale cyclones and anticyclones are described from the analysis of the thermohaline structure and parameters of these eddies their origin can be determined the hydrological structure of the subarctic labrador current and azores fronts is described

characterization of westward propagating signals in the south atlantic from altimeter and radiometer records abstract radar altimeter data from topex poseidon and jason 1 and microwave radiometer data from trmm tmi are used to investigate the large scale variability between 10 5 s and 35 5 s in the south atlantic ocean the proposed method for the analysis of the longitude time diagrams of the cross correlation between ssh and sst anomalies shows that the variability in mid latitudes is a blend of first mode baroclinic rossby waves and propagating mesoscale eddy like structures the estimated phase speed of the wave cp and propagation speed of the eddies cv are similar in 70 of the cases the absolute difference between cp and cv is less than 11 in 40 of the cases this difference is less than 5 statistical results indicate that in the case of eddies as the thermocline deepens the sea surface temperature rises and vice versa however planetary waves show more complex yet self consistent results in lower latitudes 10 5 s 15 5 s the shallower thermocline and the weak thermal gradients impose a zero phase lag between temperature and height similar to eddies poleward of those latitudes sea surface temperature and height are in quadrature of phase this indicates that geostrophic advection of the relatively stronger thermal gradient is performed by rossby waves

numerical simulation of the gulf stream system the loop current and the deep circulation 1 the loop current and the deep circulation in the gulf of mexico are numerically investigated by a primitive equation sigma coordinate ocean model with realistic surface fluxes obtained from an atmospheric forecast model a deep cyclonic circulation bounded by the deep basin in the eastern gulf of mexico is spun up by the loop current the deep cyclonic circulation is coincident with a southward current of the loop current eastern limb and weakens after loop current ring separation and cessation of the southward current the anticyclonic semienclosed loop current also induces anticyclonic lower layer columnar eddies in the eastern gulf these lower layer eddies decouple from the upper layer loop current the westward translation speed of a loop current ring is about 2 16 5 18 km d 1 the lower layer eddies have a higher speed and lead the rings into the central gulf the time averaged surface circulation of the gulf of mexico basin is anticyclonic mainly because of the transport of anticyclonic vorticity by loop current rings in the surface layer an average lower layer cyclonic circulation occurs along the continental slope of the basin

the thermal signature of volcanic eruptions on io and earth abstract we investigate a spectrum based technique to identify the style of active volcanic eruptions on jupiter s moon io thermal remote sensing of io has had to rely primarily on low spatial resolution data similar to low spatial resolution satellite data applied to detecting and charting the temporal evolution of terrestrial hot spots these terrestrial analyses use data from sensors designed to monitor the weather and sea surface temperature on io such low spatial resolution data are used to classify eruption styles modes of emplacement by means of several criteria related to the temporal evolution of the infrared spectrum associated with the eruptive activity at each hot spot which we term thermal signature we find that the ratio of the emission at 2 and 5 m and how this ratio changes with time is often diagnostic of eruption style even in low spatial resolution data tests using thermal data for terrestrial ground truth cases show that our classification system is valid on earth the results of our analysis can be used to aid in the design of future space based instruments that can be used for volcano monitoring on io as well as earth

an analysis of loop current frontal eddies in a atlantic ocean model simulation abstractthe loop current frontal eddies lcfes refer to cyclonic cold eddies moving downstream along the outside edge of the loop current in the eastern gulf of mexico they have been observed by in situ measurements and satellite imagery mostly downstream of the campeche bank continental shelf their evolution simulated by a primitive equation and 37 level atlantic ocean general circulation numerical model is described in detail in this study some of the simulated lcfes arise with the passage through the yucatan channel of a caribbean anticyclonic eddy as weak cyclones with diameters less than 100 km near the yucatan channel they then grow to fully developed eddies with diameters on the order of 150 200 km while moving along the loop current edge modeled lcfes have a very coherent vertical structure with isotherm doming seen from 50 to 1000 m depth the caribbean anticyclone and lcfe are two predominant features in this numerical model simulation which account for 22 and 10 respectively

a comparison of observed and modeled sea surface topographic time series near the new england seamounts yearlong data records from four arrays of inverted echo sounders ies equipped with pressure sensors from the northwest atlantic and 2 year records from a two layer primitive equation numerical model of this region including a prescribed deep western boundary current are compared standard deviations of barotropic and total sea surface topographic variability and the correlations between them are examined as a function of horizontal position variances contained in three spectral bands secular longer than 150 days mesoscale 20 150 days and high frequency 2 20 days are also examined the eastward penetration scale of modeled gulf stream variability shows a significant improvement over a previous comparison hallock et al 1989 standard deviations of observed sea surface height components compare favorably with those derived from model output with maxima of about 30 cm 10 cm for the barotropic contribution high correlations 0 6 0 8 between surface height and the barotropic component are found for both model and observations spectral shape is dominated by the temporal mesoscale east of the new england seamounts for both observed and modeled variability west of the seamounts the secular low frequency band becomes more important particularly for the surface height variability this result is more pronounced for model output gulf stream geostrophic current direction statistics from ies dynamic heights compare favorably with those derived from model dynamic heights upstream and downstream of the seamounts

variations of the gulf stream s north wall east of cape hatteras abstract twelve years 1977 1988 of noaa infrared imagery data were used to study the variations of the north wall displacements of the gulf stream east of cape hatteras i e between 74 w and 65 w the variations of the north wall displacements were compared with the variations in the straits of florida transport which was estimated using a multifrequency model based on the sea level differences between siboney cuba and key west florida for the period 1977 1988 and with transport measurements based on the submarine cable between jupiter florida and settlement point in the bahamas for the period 1982 1988 the north wall reached a maximum northward position in 1985 when the cable data indicated that the straits of florida transport was a maximum the north wall reached a maximum southward position in 1981 cable data were not available before 1982 but the available data suggested that there may have been a minimum transport in 1981 a weak annual cycle of the north wall was found with a maximum northward position in the fall and a maximum southward position in the spring no relationship was found between the annual cycle of the gulf stream s north wall and the annual cycle of the straits of florida transport

a modified bet equation to investigate supercritical methane adsorption mechanisms in shale abstract although the brunauer emmett teller bet equation is a classic adsorption model for describing the adsorption of gases in adsorbents it cannot be applied in supercritical conditions because the saturation vapor pressure p0 in this equation is not defined when t tc in this study a modified bet equation is proposed and can be applied to investigate supercritical methane adsorption mechanisms in shale by using density instead of pressure in this equation the observed excess high pressure methane adsorption isotherms always can be well fitted by the modified bet model when the adsorbed phase density a is not fixed the fitted results show that the number of adsorption layers n ranges from 1 79 to 2 42 with an average value of 2 12 indicating a double layer adsorption mechanism approximately moreover we compare this novel model with the commonly used langmuir and dr models and find that all the three models can fit the excess adsorption isotherms equally well however a critical advantage of this new model is that it can calculate the number of adsorption layers n while other models cannot it is this advantage that makes it possible to analyze the shale gas adsorption mechanism experimentally moreover the average number of adsorption layers is much smaller than the number of adsorption layers n indicating that there are many empty adsorption sites in the adsorption space and the density of the second layer must be less than the first layer which is consistent with the molecular simulation results

the effect of the new england seamounts on gulf stream meandering as observed from satellite ir imagery abstract it is commonly held belief that meandering of the gulf stream increases dramatically downstream of the new england seamount chain in fact this appears not to be the case the envelope of gulf stream northern edges derived from 30 months of satellite data remains constant from 65 to 58 w only the mean of the integrated path length normalized by the mean path length appears to increase downstream of the seamounts but at very nearly the same rate as upstream of them

meanders of the gulf stream downstream from cape hatteras 1975 1978 abstract weekly gulf stream paths within 1000 km downstream of cape hatteras were obtained for 1975 78 from the navy s weekly eofa charts based on satellite ir imagery they displayed two dominant meander modes first a standing meander energetic over periods between 4 months and at least 4 years and second down stream propagating meanders that were most energetic at periods of several weeks the long period standing meander was confined between nodes located at the separation point near cape hatteras i e where the stream s mean path turns seaward and at a point about 600 km farther downstream the rms amplitude was 36 km at the antinode the amplitude of propagating meanders increased rapidly in the first 200 km downstream of the separation point where the capture of warm core eddies was common farther down stream the predominant meanders had a wavelength averaging 330 km a period averaging 1 5 month a phase speed averaging 8 cm s 1 a downstream group speed averaging 17 cm s 1 and downstrea

lava flow hazard at nyiragongo volcano d r c mt nyiragongo is one of the most dangerous volcanoes in the world for the risk associated with the propagation of lava flows in 2002 several vents opened along a huge system of fractures pouring out lava which reached and destroyed a considerable part of goma a town of about 500 000 inhabitants on the shore of lake kivu in a companion paper favalli et al in bull volcanol this issue 2008 we employed numerical simulations of probable lava flow paths to evaluate the lava flow hazard on the flanks of the volcano including the neighbouring towns of goma drc and gisenyi rwanda in this paper we use numerical simulations to investigate the possibility of significantly reducing the lava flow hazard in the city through the construction of protective barriers these barriers are added to the dem of the area as additional morphological elements and their effect is evaluated by repeating numerical simulations with and without the presence of barriers a parametric study on barrier location size shape and orientation led to the identification of barriers which maximize protection while minimizing their impact this study shows that the highest hazard area corresponding to eastern goma which was largely destroyed by lava flows in 2002 cannot be effectively protected from future lava flows towards lake kivu and should be abandoned on the contrary the rest of the town can be sheltered from lava flows by means of two barriers that deviate or contain the lava within the east goma sector a proposal for the future development of the town is formulated whereby new goma is completely safe from the arrival of lava flows originating from vents outside its boundaries the proposal minimizes the risk of further destruction in town due to future lava flows

sampling of oceanic rings by satellite radar altimeter in the present paper the probability for a mesoscale oceanic rings to be seen by a perfect satellite altimeter is investigated first the motion of a ring center is determined using a stochastic differential equation the problem of radar altimeter sampling is then investigated first in the one dimensional case then for two dimensions the probability of a ring to be seen by a satellite is then computed and is shown to depend on the satellite period and fundamental interval the mean and standard deviation of the ring speed and the distance between the ring center and the nearest track when the ring appears the maximum of this probability and the time at which the maximum arises give an estimate of the satellite ability to sense the rings the observation of gulf stream gs warm and cold core rings wcr ccr by the topex poseidon and geosat altimeters are then presented as examples for both satellites and ring events the probability for the ring center to lie on a satellite track i e the entire ring signal is seen is very low less than 5 however more than 90 of the gs wcrs and 65 of the gs ccrs are seen at least once i e the distance between the ring center and a satellite track is less than the ring radius with a probability over 80 the mean probability for the satellite to see a significant part of the ring signal the distance between the ring center and a satellite track is less than half the ring radius drops to about 50 aliasing between ring motion and satellite sampling should be taken into account during the definition of altimetric data assimilation methods for numerical models on the other hand the probability of view is high enough to indicate that altimetric data could improve climatological and statistical studies of mesoscale eddies

sea surface height fluctuations observed simultaneously with inverted echo sounders and geosat time series of sea surface height anomaly as measured by inverted echo sounders with pressure gauges ies pgs and geosat altimetry are compared at six locations in the northwest atlantic near 40 n 55 w three ies pg sites lay along each of two adjacent geosat exact repeat mission ground tracks better agreement was found along the westernmost ground track pressure sensor noise is the probable source of the larger errors along the easternmost ground track the overall correlation is 0 78 along the westernmost ground track it is 0 91 decorrelation scales are about 100 km along track and about 5 days uncorrelated errors dominate but along the westernmost ground track ies pg derived sea surface height variability is systematically smaller than that derived from geosat data this factor determined by regression analysis is about 0 81 however a consistent adjustment of ies calibration removes the systematic discrepancy

uncertainties in the mean ocean dynamic topography before the launch of the gravity field and steady state ocean circulation explorer goce 1 in anticipation of the future observations of the gravity mission gravity field and steady state ocean circulation explorer goce the present day accuracy of mean dynamic topography mdt is estimated from both observations and models a comparison of five observational estimates illustrates that rms differences in mdt vary from 4 2 to 10 5 cm after low pass filtering the fields with a hamming window with wavenumber n 120 corresponding to an effective resolution of 167 km rms differences in observational mdt reduce to 2 4 8 3 cm for n 15 1334 km differences in data sources geoid model in situ data are mostly visible in the small scale oceanic features while differences in processing filtering inverse modeling techniques are reflected at larger scales a comparison of seven different numerical ocean models demonstrates that model estimates differ mostly in western boundary currents and in the antarctic circumpolar current rms differences between modeled and observed mdt are at best 8 8 cm for n 120 and reduce to 6 4 cm for n 15 for models with data assimilation a minimal rms difference of 6 6 cm n 120 to 3 4 cm n 15 is obtained with respect to the observational mdts the reduction of differences between mdts with increasing filtering scales is smaller than expected while it is expected that goce will improve mdt estimates at small spatial scales improvement of mean sea surface estimates from satellite altimetry may be needed to improve mdt estimates at larger scales

dynamics of the slope water off new england and its influence on the gulf stream as inferred from satellite ir data abstract the movements of warm core rings and the gulf stream front were studied in the new england slope water region by using both satellite ir data and available in situ sea surface temperature data it is found that 1 the rotating speed of the rings exhibits a marked seasonal variation with the maximum speed occurring in the winter and the minimum in the late fall 2 the surface area of the rings increases monotonically with time and 3 the gulf stream front at the north wall migrates seasonally and attains its northernmost position in the late fall based on these findings we calculated the horizontal eddy viscosity for the rings as 4 10 8 cm 2 5 furthermore by comparing the seasonal variations of the rotational velocity of the rings and the total mass transport of the gulf stream we suggest that the seasonal variation of the slope water hydrography through local air sea interactions could play an important role in the dynamics of the gulf stream system

gulf stream meanders observations on propagation and growth we present a new method for continuously tracking the location of the gulf stream using a moored array of inverted echo sounders time series of lateral displacements of the front shown accurate to 8 km have been collected along three sections spaced 100 150 and 200 km downstream ne of cape hatteras north carolina for a period of 12 months these records are highly coherent at all periodicities longer than 4 days from the observed phase lags a dispersion relationship is presented for the meanders as the period and wavelength t h increase from 4 days 180 km to 30 days 600 km the phase speed decreases smoothly from 40 to 20 km d the meanders exhibited rapid growth at periods longer than 4 days doubling in variance in each 50 km step downstream this downstream growth is most appropriately described by a spatial e folding scale k 400 km for t x 14 days 400 km from an array of seven inverted echo sounders ies and three deep current meters deployed 100 to 200 km northeast of cape hatteras in 2000 4000 m water this array continu ously monitored the path of the gulf stream and the deep currents under it on four deployment and recovery cruises to the area expendable bathythermograph traces xbt and hydrographic data were collected to survey the temperature and density structure along the stream path and on sections normal to it after a brief review of earlier studies on meanders this paper presents a discussion of the measurement techniques using ies in the gulf stream we show by direct compari sons with traditional measurement methods that 1 each ies produces a continuous record of the thermocline depth here taken to be the 15oc isotherm for subsequent comparison with standard methods of determining the position of the north wall of the stream with accuracy of 20 m in a range of variation of 800 m and 2 the array of ies s paired across the stream produces continuous estimates of the stream position with 8 km accuracy the results from the three ies sections located 100 150 and 200 km downstream of cape hatteras show very high coherence throughout the array with rapid 20 to 40 km d l translation of the meanders downstream accompanied by rapid growth of the lateral displacements doubling in variance with each 50 km step downstream in a companion paper w e johns and d r watts manuscript in preparation 1982 we discuss the current meter records and the relationship of the deep currents to gulf stream meanders 1981 they have wavelengths of 150 200 km and propagate downstream at rates of approximately 30 40 km d downstream of cape hatteras the envelope of meandering broadens greatly to 200 300 km figure 1 and the stream can shift through more than its own width in the early shipboard surveys fuglister and worthington 1951 fuglis ter 1963 the path of the stream south of nova scotia was dominated by long wavelength 400 km large amplitude meanders those which were studied in detail were found to be quasi stationary and were characterized by a slowly evolving baroclinic field indicating temporal growth far ther upstream near 72ow however significant eastward propagation was observed one meander crest moved at a rate of approximately 17 km d for 3 days fuglister and worthington 1951 hansen 1970 later conducted monthly path surveys between 75 o and 55ow for 1 year with weekly surveys over a 2 month period using a towed thermistor he found meanders on appreciably shorter scales with wave lengths ranging from 200 to 400 km mean downstream propagation rates of 5 10 cm s and spatial growth rates of 2 x 10 3 km were estimated by constructing lines of constant phase between features on successive path se quences the rapid evolution between monthly paths how ever produced considerable ambiguity in identifying and tracking events weekly paths evolved more continuously and were apparently not aliased by higher frequency wave number phenomena

mesoscale eddy detection in satellite imagery of the oceans using the radon transform abstract the present study proposes a new methodology to identify mesoscale eddies that are ubiquitous in the ocean and can be observed in a variety of satellite images our focus is on eddies with mean diameter of 100 500 km the proposed methodology uses an algorithm based on the radon transform the basic premise is that the inverse radon transform of a circularly symmetric feature is angle independent therefore the more constant the radon transform of an image is with respect to the rotation angle the more circularly symmetric the image is although our method is based on circular symmetry it is able to detect non symmetric eddies using a sensitivity parameter that quantifies the deformation our method is effective to determine how circular a feature observed in a satellite image is and suggest whether it is an eddy or not based on geometric criteria a series of tests with synthetic data were performed to assess the sensitivity to spectral content and aspect ratio detectable by the method another sequence of tests was carried out with images of chlorophyll a concentration sea surface temperature and sea surface height in the three cases five areas of 100 50 pixels were selected and filtered with exactly the same algorithm and parameters the two sets of tests indicate that the proposed method was able to identify eddies in a single time series of satellite images and in multiple series of different variables the main advantage of this method in comparison with either automatic ones based on dynamics and geometry or manual methods is its ability to observe eddies in multiple data sets of different variables

a year of lava fountaining at etna volumes from seviri 1 we present a new method that uses cooling curves apparent in high temporal resolution thermal data acquired by geostationary sensors to estimate erupted volumes and mean output rates during short lava fountaining events the 15 minute temporal resolution of the data allows phases of waxing and peak activity to be identified during short 150 to 810 minute long events cooling curves which decay over 8 to 21 hour periods following the fountaining event can also be identified application to 19 fountaining events recorded at etna by msg s seviri sensor between 10 january 2011 and 9 january 2012 yields a total erupted dense rock lava volume of 28 106 m3 with a maximum intensity of 227 m3 s 1being obtained for the 12 august 2011 event the time averaged output over the year was 0 9 m3 s 1 this being the same as the rate that has characterized etna s effusive activity for the last 40 years

on the meridional surface profile of the gulf stream at 55 w nine month records from nine inverted echo sounders iess are analyzed to describe the mean baroclinic gulf stream at 55 w ies acoustic travel times are converted to thermocline depth which is optimally interpolated kinematic and dynamic parameters gulf stream meridional position velocity and vorticity are calculated primary gulf stream variability is attributed to meandering and changes in direction a mean stream coordinate relative to gulf stream instantaneous position and direction meridional profile is derived and compared with results presented by other investigators the mean velocity is estimated at 0 84 m s 1 directed 14 to the right of eastward and the thermocline 12 c drops 657 m north to south corresponding to a baroclinic rise of the surface of 0 87 m the effect of gulf stream curvature on temporal mean profiles is found to be unimportant and of minimal importance overall the derived downstream current profile is well represented by a gaussian function and is about 190 km wide where it crosses zero surface baroclinic transport is estimated to be 8 5 104 m2 s 1 and maximum shear flanking the maximum is 1 2 10 5 s 1 results compare well with other in situ observational results from the same time period on the other hand analyses by others of concurrent satellite altimetry geosat suggest a considerably narrower more intense mean gulf stream

rapid intensification of a sheared fast moving hurricane over the gulf stream abstracthurricane irene 1999 rapidly intensified from 65 to 95 kt 33 4 to 48 9 m s 1 in 18 h during the rapid intensification ri period the northeastward storm motion increased from 10 to 18 m s 1 the ambient southwesterly vertical wind shear increased from 6 7 to 10 13 m s 1 and the downshear tilt of the inner core vortex increased the azimuthal wavenumber 1 asymmetric convection that developed was consistent with a superposition of shear induced and storm motion induced forcing for vertical motion downshear and ahead of the center although the diabatic heating remained strongly asymmetric it was of sufficient intensity to dramatically increase the azimuthally averaged heating this heating occurred almost entirely inside the radius of maximum winds a region known to favor rapid warm core development and spinup of the vortex it is hypothesized that asymmetric forcing from the large vertical wind shear and rapid storm motion were responsible for ri an unanswered question is what determin

mississippian barnett shale fort worth basin north central texas gas shale play with multi trillion cubic foot potential the mississippian barnett shale serves as source seal and reservoir to a world class unconventional natural gas accumulation in the fort worth basin of north central texas the formation is a lithologically complex interval of low permeability that requires artificial stimulation to produce at present production is mainly confined to a limited portion of the northern basin where the barnett shale is relatively thick 300 ft 92 m organic rich presentday total organic carbon 3 0 thermally mature vitrinite reflectance 1 1 and enclosed by dense limestone units able to contain induced fractures the most actively drilled area is newark east field currently the largest gas field in texas newark east is 400 mi 2 1036 km 2 in extent with more than 2340 producing wells and about 2 7 tcf of booked gas reserves cumulative gas production from barnett shale wells through 2003 was about 0 8 tcf wells in newark east field typically produce from depths of 7500 ft 2285 m at rates ranging from 0 5 to more than 4 mmcf day estimated ultimate recoveries per well range from 0 75 to as high as 7 0 bcf efforts to extend the current barnett play beyond the field limits have encountered several challenges including westward and northward increases in oil saturation and the absence of lithologic barriers to induced fracture growth patterns of oil and gas occurrence in the barnett in conjunction with maturation and burial history data indicate a complex multiphased thermal evolution with episodic expulsion of hydrocarbons and secondary cracking of primary oils to gas

spatial and temporal evolution of a gulf stream crest warm core ring interaction an intensive near synoptic hydrographic study of the reabsorption of a warm core ring into the gulf stream at a meander crest was conducted near 70 w in fall 1988 using a mixture of measurement techniques and statistical optimal interpolation to map the velocity and density fields the study documents how the normally robust cross stream structure of the gulf stream breaks down and the process by which a high pressure ridge between the stream and the ring develops examination of the layer potential vorticity lpv structure on two specific volume anomaly surfaces approximately 18 c and 10 c showed different characteristics of cross stream lpv structure on the shallower surface the cross stream lpv structure was dominated by the cross stream gradient of layer thickness on the deeper surface the much weaker cross stream lpv structure reflected the structure of the relative vorticity field during the 10 day period of ringstream contact considerable water was exchanged rupturing the ring and eventually resulting in the ring s reentrainment by the gulf stream time varying transports as large as 30 sv were exchanged to the north and south between the surface and 5 c the gulf stream bifurcates in such a way that the anticyclonic southern side continues through the meander crest uninterrupted while the cyclonic side is diverted to the north to replace the low potential vorticity waters of the ring with waters of high potential vorticity contact between the ring and the stream is established first at the surface and progresses downward with increasing time the decreased time needed to remove the ring s vorticity in the lower layers is consistent with the geometrical picture of the gulf stream colliding with a bowl shaped ring the flushing time for the lens of 18 c water in the ring is on the order of 5 days slightly longer than the 2 3 days for the relative vorticity of the 10 c surface

2d and 3d nanopore characterization of gas shale in longmaxi formation based on fib sem abstract studying complex pore structures is the key to understanding the mechanism of shale gas accumulation fib sem focused ion beam scanning electron microscope is the mainstream and effective instrument for imaging nanopores in gas shales based on this technology 2d and 3d characteristics of shale samples from lower silurian longmaxi formation in southern sichuan basin were investigated 2d experimental results show that the pores in shale are nanometer sized and the structure of those nanopores can be classified into three types organic pores inorganic pores and micro fractures among the three types organic pores are dominantly developed in the om organic matter with three patterns such as continuous distributed om om between clay minerals and om between pyrite particles and the size of organic pores range from 5 nm to 200 nm inveresly inorganic pores and micro fractures are less developed in the longmaxi shales 3d digital rocks were reconstructed and segmented by 600 continuous images by fib cutting and sem imaging simultaneously the pore size distribution and porosity can be calculated by this 3d digital core showing that its average value is 32 nm and porosity is 3 62 the 3d digital porosity is higher than its helium porosity which can be regarded as one important parameter for evaluation of shale gas reserves the 2d and 3d characterized results suggest that the nanometer sized pores in organic matter take up the fundamental storage space for the longmaxi shale these characteristics have contributed to the preservation of shale gas in this complex tectonic area

intrusion of loop current waters onto the west florida continental shelf an intrusion of loop current water up desoto canyon and onto the west florida continental shelf to within 8 km of the shore occurred in february 1977 boat aircraft and satellite data collected in the area for another purpose were used to estimate the space and time scales of the intrusion and the ultimate fate of the intruded waters the duration of the event was 18 days oceanic waters advanced across the shelf at speeds of 20 cm s sup 1 at maximum intrusion 6650 km sup 2 of shelf were affected approximately half the intruded water receded off the shelf and half appears to have been modified in situ

sea surface topographic variability near the new england seamounts an intercomparison among in situ observations numerical simulations and geosat altimetry from the regional energetics experiment intercomparisons are made among three sets of results for two regions of the gulf stream upstream and downstream of the new england seamount chain nesc observational records from 12 inverted echo sounders with pressure gauges ies pgs concurrent geosat altimeter crossover point differences and results from a primitive equation model of the region standard deviations of sea surface topography show generally good agreement for the three data sources no significant difference between the upstream and downstream regions is observed in the actual data ies pg records and geosat topographic variability have values of about 30 cm on both sides of the nesc although model results show a discrepancy in the eastern region barotropic fluctuations account for about 30 of the total surface topographic variability and are only partially correlated with baroclinic fluctuations

initial observations of the subsurface structure and short term variability of the seaward deflection of the gulf stream off charleston south carolina a recurring seaward deflection of the surface layer of the gulf stream has been observed near 32 n latitude off the coast of the southeastern united states it has been suggested that a ridge and trough bottom feature the so called charleston bump on the upper continental slope off the georgia south carolina coast produces the deflection through a bottom steering effect present data indicate that the deflection is great enough to direct the gulf stream s shoreward surface thermal front to the east and even south of east about 70percnt of the time air deployed expendable bathythermograph surveys have been made with sufficient coverage to provide several synoptic three dimensional views of the gulf stream s thermal frontal zone in the region between savannah georgia and cape hatteras north carolina these views show the subsurface structure of the seaward deflection to exhibit large short term variability during wintertime conditions february 1979 the greatest deflection 090 true of the near surface front occurred at a time when the deeper front was more aligned 080 true with local topography within the few days following this observation the deflection angle at all depths decreased to near or below 070 true two large amplitude gulf stream meanders progressed northeastward away from the deflection region during this time period deflection angles at all levels during late summertime conditions november 1979 were observed to be near 070 true a simple kinematical model which incorporates growing propagating gulf stream meanders is proposed to explain the deflection s short term variability a dome shaped volume of cold water was observed to be located over the upper continental slope immediately downstream of the deflection the existence and persistence of this cold dome suggest that upwelling is important in its maintenance a hypothesis consistent with its hydrographic properties

temperature and velocity structure of the gulf stream northeast of cape hatteras modes of variability thirty five expendable bathythermograph sections and 10 pegasus velocity sections taken approximately normal to the gulf stream northeast of cape hatteras were used to examine the variability of the current s structure the regridded profiles were superimposed in a stream coordinate system such that the temperature variance associated with the superposition was minimized the resulting variance field was examined using empirical orthogonal functions the temperature variability is heavily weighted by seasonal warming hence the following results exclude temperatures from the upper 200 m the first mode 48 of the variance is due to a deepening of the thermocline relative to the mean on the offshore side of the gulf stream and a shoaling on the inshore edge associated with a change of geostrophic velocity and baroclinic transport the amplitudes of this transport mode indicate a slight downstream increase in baroclinic transport 2 per 100 km and a seasonal modulation 5 sverdrups rms that peaks in may june the second temperature mode below 200 m 13 21 of the variance is associated with a change in horizontal shear a vorticity mode and is positively correlated with measured path curvature and layer thickness the directly observed pegasus velocity sections were combined with corresponding temperature sections to compute their joint empirical modes the dominant combined mode has a thermocline structure change as in the transport mode that is coupled with an increase in alongstream velocity and for levels above the main thermocline an inflow from both sides toward the center both temperature and velocity data indicate that high transport in the gulf stream is associated with lateral displacement offshore of its mean position

observations on the propagation growth and predictability of gulf stream meanders during a 3 year period gulf stream positions determined by satellite infrared imagery on a grid northeast of cape hatteras have been correlated against inlet path parameters displacement from the mean position angle and curvature monitored by an array of inverted echo sounders ies by cross spectral calculations between these measurements we determined the downstream coherences phase speeds and spatial growth rates the downstream path predictability from these inlet parameters was tested in a multiple input linear response model the most energetic meanders with periods of 33 50 days remained highly coherent for 300 km downstream roughly the dominant wavelength with marginal coherence again at 500 575 km phase speeds are frequency dependent and decrease with distance downstream for the 50 33 day meanders phase speeds decreased from 10 17 km d at the inlet to 6 8 km d at a distance downstream of about 550 km the average growth rate spatial e folding wave number over the entire region is 1 3 10 3 km 1 within 300 km of the inlet the multiple coherence accounts for 55 65 of the total path displacement variance with displacement and angle being the best individual predictors in the first and last halves of this region respectively

gulf stream path analysis near the new england seamounts as part of the naval ocean research and development activity s regional energetics experiment 12 inverted echo sounders iess were deployed from june 1985 to july 1986 in two arrays across the historical mean path of the gulf stream near 67 w and 58 w slightly upstream and downstream of the new england seamount chain gulf stream positions and directions were computed at half day intervals for adjacent ies pairs levels of variability at the two array locations were similar but the characteristics of the meanders in terms of propagation and current direction were quite different evidence was found for a quasi stationary meander near 58 w features deduced from ies measurements are compared with concurrent infrared air dropped expendable bathythermograph and geosat altimetry observations

characterization of methane adsorption on overmature lower silurian upper ordovician shales in sichuan basin southwest china experimental results and geological implications abstract a series of methane adsorption isotherms were measured at 35 4 c 50 6 c and 65 4 c at pressures up to 15 0 mpa for eight dried overmature lower silurian upper ordovician shale samples collected from the sichuan basin with toc values in the range of 1 87 5 74 the measured maxima of excess adsorption capacity of methane range from 1 25 to 2 50 cm 3 g rock at 65 4 c the maxima are slightly enhanced at 35 4 c but all are positively correlated with total organic carbon toc both the supercritical dubinin radushkevich sdr and langmuir based excess adsorption models were found to represent the experimental excess adsorption isotherms equally well within the experimental range the temperature dependent densities of adsorbed methane resulting from the parameter fit of the sdr based excess adsorption model are in the range of 297 415 mg cm 3 for the langmuir based excess adsorption model the adjusted densities range from 386 mg cm 3 to 1027 mg cm 3 and most of them are much larger than the liquid density of methane at its boiling point 424 mg cm 3 nevertheless the maxima of absolute methane adsorption capacity fitted by both models are not significantly different and are linearly correlated one of the contributors to the uncertainty of the gas in place estimation in geological conditions is the inconsistent utilization of experimental excess sorption data as absolute sorption values particularly at high pressures however the choice of adsorption model itself langmuir or sdr based and the fitting procedure assuming either constant or temperature dependent adsorbed phase density and maximum sorption capacity do not significantly affect the estimated gips for the geological system studied here with depths of less than 4000 m

thirty years of satellite derived lava discharge rates at etna implications for steady volumetric output 1 we present a 30 year long data set of satellite derived time averaged lava discharge rates tadr for mount etna volcano sicily italy spanning 1980 2010 and comprising 1792 measurements during 23 eruptions we use this to classify eruptions on the basis of magnitude and intensity as well as the shape of the tadr time series which characterizes each effusive event we find that while 1983 1993 was characterized by less frequent but longer duration effusive eruptions at lower tadrs 2000 2010 was characterized by more frequent eruptions of shorter duration and higher tadrs however roughly the same lava volume was erupted during both of these 11 year long periods so that the volumetric output was linear over the entire 30 year period increasing at a rate of 0 8 m3 s 1 between 1980 and 2010 the cumulative volume record can be extended back in time using data available in the literature this allows us to assess etna s output history over 5 centuries and to place the current trend in historical context we find that output has been stable at this rate since 1971 at this time the output rate changed from a low discharge rate phase which had characterized the period 1759 to 1970 to a high discharge rate phase this new phase had the same output rate as the high discharge rate phase that characterized the period 1610 1669 the 1610 1669 phase ended with the most voluminous eruption of historic times

bioinformatic approaches for objective detection of water masses on continental shelves 1 as part of the 2001 hyper spectral coupled ocean dynamics experiment sea surface temperature and ocean color satellite imagery were collected for the continental shelf of the mid atlantic bight these images were used to develop a water mass analysis and classification scheme that objectively describes the locations of water masses and their boundary locations this technique combines multivariate cluster analysis with a newly developed genetic expression algorithm to objectively determine the number of water types in the region on the basis of ocean color and sea surface temperature measurements then through boundary analysis of the water types identified the boundaries of the major water types were mapped and the differences between them were quantified using predictor space distances results suggest that this approach can track the development and transport of water masses because the analysis combines the information of multiple predictors to describe water masses it is an effective tool in detecting water masses not readily recognizable with temperature or chlorophyll alone

local sensitivities of the gulf stream separation abstractrobust and accurate gulf stream separation remains an unsolved problem in general circulation modeling whose resolution will positively impact the ocean and climate modeling communities oceanographic literature does not face a shortage of plausible hypotheses that attempt to explain the dynamics of the gulf stream separation yet a single theory that the community agrees on is missing in this paper the authors investigate the impact of the deep western boundary current dwbc coastline curvature and continental shelf steepening on the gulf stream separation within regional configurations of the massachusetts institute of technology general circulation model artificial modifications to the regional bathymetry are introduced to investigate the sensitivity of the separation to each of these factors metrics for subsurface separation detection confirm the direct link between flow separation and the surface expression of the gulf stream in the mid atlantic bight it is shown that the gulf stream

sst wind interaction in coastal upwelling oceanic simulation with empirical coupling observations primarilyfromsatellites haveshownastatisticalrelationshipbetweenthesurfacewindstress and underlying sea surface temperature sst on intermediate space and time scales in many regions inclusive of eastern boundary upwelling current systems in this paper this empirical sst wind stress relationship is utilized to provide a simple representation of mesoscale air sea coupling for an oceanic model forced by surface winds namely the regional oceanic modeling system roms this model formulation is applied to an idealized upwelling problem with prevailing equatorward winds to determine the coupling consequencesonflow sst stratification andwindevolutions theinitiallyuniformwindfieldadjuststhrough coupling to a cross shore profile with weaker nearshore winds similar to realistic ones the modified wind stress weakens the nearshore upwelling circulation and increases sst in the coastal zone the sst induced wind stress curl strengthens offshore upwelling through ekman suction the total curl driven upwelling exceeds the coastal upwelling the sst induced changes in the nearshore wind stress field also strengthen and broaden the poleward undercurrent the coupling also shows significant impact on the developing mesoscale eddies by damaging cyclonic eddies more than anticyclonic eddies which leads to dominance by the latter dynamically this is a consequence of cyclones with stronger sst gradients that induce stronger wind perturbations inthis particularupwellingproblemandthatarethereforegenerally moresusceptibletodisruption than anticyclones at finite rossby number the net effect is a weakening of eddy kinetic energy

drifting buoy observations of a loop current anticyclonic eddy the loop current penetrated deep into the gulf of mexico in early 1989 after several eddy formation and reattachment cycles a southwestward propagating anticyclonic eddy was formed during the summer the loop current and subsequent eddy produced strong currents over widespread areas on the louisiana continental slope prompting a series of current measurement programs because of the lack of satellite infrared coverage in the gulf of mexico during the summer the trajectories of 53 argos tracked drifting buoys deployed in the gulf of mexico in 1989 were assembled to determine the synoptic history of the loop current and anticyclonic eddy during this event ten of the most critical summertime buoy trajectories are discussed here in addition the trajectories of three of the buoys simultaneously deployed at different radii in the eddy were chosen for analysis with a kinematic feature model the model assumes the looping buoy motion is generated by an elliptical orbit around a translating eddy center the buoy trajectories were used to determine time series of the feature model parameters including eddy center shape and circulation characteristics the time series results indicate that the eddy actually propagated in a series of short sprints separated by longer stalls during the sprints the eddy propagated as an elliptical but otherwise symmetric solid body during the stalls significant asymmetries developed the asymmetries are consistent with attachment to the loop current during the first stall the effects of topographic rossby wave dispersion during the second and the effects of planetary rossby wave dispersion during the third the results provide both a framework for the interpretation of in situ observations and a detailed evolutionary history for numerical modelers

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

a relation between lava discharge rate thermal insulation and flow area set using lidar data 1 a simple linear relation can be used to link time averaged discharge rate tadr and lava flow area a the relation applies to given insulation conditions as described by the characteristic flow surface temperature te and will vary from case to case depending on rheological and topographic influences on flow spreading most flows have insulation conditions that change through time modifying the relationship between tadr and area as insulation conditions evolve using lidar data we can define tadr the flow area that the discharge feeds and te allowing generation of a case specific relation to convert satellite data derived flow areas to tadr for etna s 2006 lava flow field we obtain a relation whereby tadr 5 6 10 6 a for well insulated conditions te 100 c and tadr 1 5 10 4 a for poorly insulated conditions te 600 c

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty

five year climatological survey of the gulf stream system and its associated rings a 5 year climatological survey of the gulf stream system s landward surface edge defines the mean standard deviation extreme limits annual and interannual variabilities and frequency distributions along 0 5 longitudinal transects from 91 to 44 w the climatology covers the loop current in the gulf of mexico and the gulf stream in the northwest atlantic ocean autocorrelations and power spectra are derived for longitudinal transects between 79 5 and 57 5 w the study also investigates the observed warm core ring and cold core ring movements and their areal extent the observed data are compiled from the oceanographic analysis charts produced by the national oceanic and atmospheric administration which utilize infrared satellite imagery and in situ observations east of cape hatteras the gulf stream system landward surface edge exhibits both interannual and annual signals the interannual variability is equal to the annual variability the mean monthly gulf stream position for the longitudinal band 70 44 w shifts from farthest north in september to farthest south in february the magnitude of the annual shift is largest near the grand banks frequency distributions of the gulf stream system position are quasi normal nearly everywhere autocorrelation plots from the 5 year time series of gulf stream positions at longitudinal transects 79 5 57 5 w exhibit three well defined e folding time regimes with a maximum time of 10 weeks at 72 w power spectrums from 79 5 to 57 5 w are red spectrums having dominant peaks of 1 year period or greater the largest total spectra energies are found at 61 w the loop current sheds rings at two apparent spatial scales which are labeled major 307 km mean and minor 185 km mean warm core rings annually the loop current sheds about one major warm core ring which translates into the western basin of the gulf of mexico and one minor warm core ring which is usually reabsorbed by the loop current the major loop current warm core ring sheddings have no seasonal preference loop current warm core rings have a mean velocity of 2 4 km d west southwest an average of 22 gulf stream warm core rings are formed and absorbed annually between 75 and 44 w the largest frequency of warm core ring formations is seen near the new england seamounts while the largest frequency of warm core ring absorptions is found near cape hatteras gulf stream warm core rings can absorb each other as occurred in 14 of the absorption cases with the highest frequency just upstream of the new england seamounts the gulf stream warm core rings have a surface diameter decay rate of 0 026 per week loop current warm core rings are similar the gulf stream warm core rings have a mean velocity of 2 4 km d west southwest cold core rings have a mean cool core surface diameter of 105 km and a mean velocity of 1 km d southwest more definitive conclusions on cold core rings are not possible as ring identification and tracking by satellite infrared imagery is tentative

lagrangian motion and fluid exchange in a barotropic meandering jet kinematic models predict that a coherent structure such as a jet or an eddy in an unsteady flow can exchange fluid with its surroundings the authors consider the significance of this effect for a fully nonlinear dynamically consistent barotropic model of a meandering jet the calculated volume transport associated with this fluid exchange is comparable to that of fluid crossing the gulf stream through the detachment of rings although the model is barotropic and idealized in other ways the transport calculations suggest that this exchange mechanism may be important in lateral transport or potential vorticity budget analyses for the gulf stream and other oceanic jets the numerically simulated meandering jet is obtained by allowing a small amplitude unstable meander to grow until a saturated state occurs the resulting flow is characterized by finite amplitude meanders propagating with nearly constant speed and the results clearly illustrate the stretching and stirring of fluid particles along the edges of the recirculation regions south of the meander crests and north of the troughs the fluid exchange and resulting transport across boundaries separating regions of predominantly prograde retrograde and recirculating motion is quantified using a dynamical systems analysis the geometrical structures that result from the analysis are shown to be closely correlated with regions of the flow that are susceptible to high potential vorticity dissipation moreover in a related study this analysis has been used to effectively predict the entrainment and detrainment of particles to and from the jet

rheological control on the radiant density of active lava flows and domes abstract during an effusive extrusive eruption the capability of an active lava body flow or dome to radiate thermal energy depends on how the lava discharge rate is accommodated by the expansion of the magma body and by the cooling of its surface this feature can be described by a single empirical parameter defined radiant density c rad in j m 3 that for a given discharge rate expresses the efficiency of the lava body to change its area and or to insulate its inner core thus modulating the heat radiated from the active surface by comparing the volcanic radiative energy vre in j detected by modis during 28 eruptions at 18 active volcanoes with their erupted lava volumes vol in m 3 we show that the radiant density c rad vre vol is inversely proportional to the silica content of the erupted lava basic lavas 45 52 wt sio 2 have the highest observed radiant density 1 to 4 10 8 j m 3 while intermediate 52 63 wt sio 2 and acidic 63 wt sio 2 lavas show a gradually lower radiant densities 1 5 to 9 10 7 j m 3 and 0 2 to 1 10 7 j m 3 for intermediate and acidic composition respectively we regard this correlation as the result of the control that the rheology of lavas exerts on cooling and spreading processes of related bodies in particular we found that for any given compositional group the radiant density is essentially related to a characteristic thickness of active lavas at the time of a satellite acquisition we suggest that the radiant density of effusive extrusive lava bodies can be predicted 50 by means of an empirical relationship based on the sio 2 content of the erupted lava this makes this parameter very useful in observing volcanic activity especially in remote regions where access may not be possible by measuring the energy radiated during an eruption and by assuming a lava composition based on the tectonic setting or magmatic province we suggest that the radiant density can be used to estimate lava discharge rates and erupted volumes for volcanoes characterised by effusive or extrusive activity