gas hydrates clathrates causing pore water freshening and oxygen isotope fractionation in deep water sedimentary sections of terrigenous continental margins the occurrence of gas hydrates in deep water sections of the continental margins predicted from anomalous acoustic reflectors on seismic profiles has been confirmed by recent deep sea drilling results on the pacific continental slope off guatemala gas hydrates were brought up for the first time from two holes 497 498a drilled during leg 67 of the dsdp in water depths of 2360 and 5500 m respectively the hydrates occur in organic matter rich pleistocene to miocene terrigenous sediments in the hydrate bearing zone a marked decrease in interstitial water chlorinities was observed starting at about 10 20 m subbottom depth pore waters at the bottom of the holes near 400 m subbottom have as little as half the chlorinity of seawater i e 9 similar but less pronounced trends were observed during previous legs of the dsdp in other hydrate prone segments of the continental margins where recharge of fresh water from the continent can be excluded e g leg 11 the crystallization of hydrates like ice excludes salt ions from the crystal structure during burial the dissolved salts are separated from the solids subsidence results in a downward motion of the solids including hydrates relative to the pore fluids thawing of hydrates during recovery releases fresh water which is remixed with the pore fluid not involved in hydrate formation the volume of the latter decreases downhole thus causing downward decreasing salinity chlorinity hydrate formation is responsible for oxygen isotope fractionation with18o enrichment in the hydrate explaining increasingly more positive 18o values in the pore fluids recovered after hydrate dissociation with depth

carbon geochemistry of cold seeps methane fluxes and transformation in sediments from kazan mud volcano eastern mediterranean sea abstract despite growing concerns about potential enhancement of global warming and slope failure by methane produced by gas hydrate dissociation much uncertainty surrounds estimates of gas hydrate reservoir sizes as well as methane fluxes and oxidation rates at the sea floor for cold seep sediments of the eastern mediterranean sea depth dependent methane concentrations and rates of anaerobic oxidation of methane aom are constrained by modeling the measured pore water sulfate profile the calculated dissolved methane distribution and flux are sensitive to the advective flow velocity which is estimated from the depth distributions of conservative pore water constituents na b near complete anaerobic oxidation of the upward methane flux of 6 0 mol m 2 yr 1 is supported by the depth distributions of indicative biomarkers and the carbon isotopic compositions of organic matter and dissolved inorganic carbon pore water and solid phase data are consistent with a narrow depth interval of aom 14 18 cm below the sediment water interface based on an isotopic mass balance the biomass of the microbial population carrying out oxidation of methane coupled to sulfate reduction at the given methane flux represents 20 of the total organic carbon which is a significant pool of in situ formed organic matter model results indicate that the asymptotic methane concentration is reached a few meters below the sediment surface the predicted asymptotic concentration is close to the in situ saturation value with respect to gas hydrate suggesting that the rate of shallow gas hydrate formation is controlled by the ascending methane flux the proposed model approach can be used to predict the formation of gas hydrate and to quantify methane fluxes plus transformation rates in surface sediments where fluid advection is an important transport mechanism

estimates of heat flow derived from gas hydrates a gas hydrate phase boundary in marine sediments is often observed as an anomalous reflector in seismic profiling data from the depth of the reflectors heat flow values can be estimated using the phase relation of the gas hydrate system and inferred density and thermal conductivity of sediments this method is applied to the data in the nankai trough around central america and along the blake outer ridge the estimated values consistent with those measured by conventional means suggest that derivation of heat flow by this method is feasible on the landward slope of the nankai trough we find that heat flow increases downslope toward the floor of the trough

gravity wave and orographic wave activity observed around the antarctic and arctic stratospheric vortices by the cosmic gps ro satellite constellation 1 polar stratospheric gravity wave activity is studied using data from the constellation observing system for meteorology ionosphere and climate cosmic global positioning system radio occultation gps ro waves with vertical wavelengths of 2 to 15 km are considered the temperature variance 2 is used as a measure of wave activity and is studied on isentropic surfaces large intermittent orographic wave activity is identified during austral spring 2007 above the patagonian andes and the antarctic peninsula where 2 in the stratosphere increases by up to a factor of 5 for periods of 5 days to a few weeks the 2 are also investigated in equivalent latitudes to allow a direct comparison with the changing vortex structure the october 2007 2 inside the antarctic vortex boundary region at 400 600 k is one and a half times that outside the vortex this region of enhanced 2 descends in time and is not observed during the decay of the arctic vortex during the boreal winter of 2006 2007 orographic wave activity is observed above scandinavia and greenland an analysis of the 400 k and the 450 k levels in both hemispheres shows a strong relationship between enhanced 2 and the location of the vortex edge suggesting that the waves observed are propagating poleward and are guided to higher altitudes by the vortex the line of sight of the occultations shows a preference for north south alignment indicating that cosmic favors the detection of orographic waves above the north south oriented mountain ranges considered here

observations of global ionospheric responses to the 2009 stratospheric sudden warming event by formosat 3 cosmic 1 the global ionospheric response to a stratospheric sudden warming ssw is studied using three dimensional electron density maps derived from radio occultation observations of formosat 3 cosmic during the 2009 ssw periods results show that the ionospheric electron density at eia crests exhibit a morning early afternoon increase followed by an afternoon decrease and an evening increase indicative of a semidiurnal component during the ssw period which is consistent with recent studies the latitude altitude electron density slice maps show that the ssw related modifications of the equatorial plasma fountain interact with the existing summer to winter neutral winds and resulting in a north south asymmetry the global ionospheric response shows a clear longitudinal dependence in the equatorial plasma fountain enhancement during morning early afternoon inferred from the duration of the equatorial ionization anomaly eia enhancement following the enhancement prominent global eia reductions resulting from the equatorial plasma fountain weakening in the afternoon sector are seen the ionospheric response to the 2009 ssw event is also compared with the usual seasonal variation during january february 2007 instead of showing the electron density increase in the northern hemisphere and decrease in the southern hemisphere as the usual seasonal variation does the ssw period ionosphere shows prominent global electron density reductions in the afternoon period during the 2009 ssw event

generalized maxwell bodies and estimates of mantle viscosity summary three generalized maxwell bodies gmbs are discussed whose transient creep properties make them interesting alternatives to the classical maxwell body cmb in interpretations of post glacial uplift the first gmb is defined by its relaxation spectrum the second by its quality factor and the third by its stress strain relation in each case the gmb is characterized by three parameters only the unrelaxed modulus the steady state viscosity or a time constant and a dimensionless parameter representative of the transient creep properties this is one parameter less than needed for the burgers body which has mainly been used so far to model transient creep the gmb models are described in some detail and numerical results for their viscoelastic moduli relaxation spectra and relaxation and creep functions are given for practical applications it is most important that the viscoelastic moduli can be calculated at arbitrary frequencies in the second part of the paper post glacial uplift data from canada and fenno scandia are interpreted with the gmb rheologies described otherwise the earth model used and the assumptions on the form and history of the ice load are very simple effective viscosities of the successful models i e inverse creep rates at times representative of mantle convection fall in the range 1022 1024p 1021 1023pas and are in part considerably larger than mantle viscosities derived under the assumption of a cmb rheology hence post glacial uplift data constrain mantle viscosity less than has been believed until recently

contribution of small glaciers to global sea level observed long term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers excluding those in greenland and antarctica to the oceans the average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance these data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975 although the error band is large these glaciers appear to account for a third to half of observed rise in sea level approximately that fraction not explained by thermal expansion of the ocean

secondary gravity wave generation over new zealand during the deepwave campaign multiple events during the deep propagating gravity wave experiment measurement program revealed mountain wave mw breaking at multiple altitudes over the southern island of new zealand these events were measured during several research flights from the national science foundation national center for atmospheric research gulfstream v aircraft utilizing a rayleigh lidar an na lidar and an advanced mesospheric temperature mapper simultaneously a flight on 29 june 2014 observed mws with horizontal wavelengths of 80 120 km breaking in the stratosphere from 10 to 50 km altitude a flight on 13 july 2014 observed a horizontal wavelength of 200 240 km mw extending from 20 to 90 km in altitude before breaking data from these flights show evidence for secondary gravity wave sgw generation near the breaking regions the horizontal wavelengths of these sgws are smaller than those of the breaking mws indicating a nonlinear generation mechanism these observations reveal some of the complexities associated with mw breaking and the implications this can have on momentum fluxes accompanying sgws over mw breaking regions

the effect of orographic gravity waves on antarctic polar stratospheric cloud occurrence and composition 1 a seasonal analysis of the relationship between mesoscale orographic gravity wave activity and polar stratospheric cloud psc composition occurrence around the whole of antarctica is presented gravity wave variances are derived from temperature measurements made with the constellation observing system for meteorology ionosphere and climate cosmic global positioning system radio occultation gps ro satellites data from the cloud aerosol lidar with orthogonal polarization caliop instrument onboard the cloud aerosol lidar and infrared pathfinder satellite observations calipso satellite are used to determine the psc composition class distribution and spatial volume the results show intermittent large wave activity above the antarctic peninsula which is coincident with large volumes of h2o ice pscs these ice psc volumes advect downstream where increases in nitric acid trihydrate nat psc volumes occur supporting the mountain wave seeding hypothesis during winter 2007 in the latitude range 60 s 70 s near the edge of the vortex and where temperatures are close to psc formation thresholds 30 of all pscs are attributable to orographic gravity waves in the separate composition classes around 50 of both h2o ice pscs and a high nat number density liquid nat mixture class of pscs are due to these waves while we show that planetary waves are the major determinant of psc presence at temperatures close to the nat formation threshold we also demonstrate the important role of mesoscale intermittent orographic gravity wave activity in accounting for the composition and distribution of pscs around antarctica

pore water anomalies of submarine gas hydrate zones as tool to assess hydrate abundance and distribution in the subsurface what have we learned in the past decade abstract the most significant new contributions to the study of natural gas hydrates in the past decade have come from findings of the ocean drilling program odp notably legs 112 141 146 and 164 and to a lesser extent legs 131 160 170 and 186 leg 164 in particular was dedicated to gas hydrate drilling in the blake ridge gas hydrate field in the west atlantic in an unprecedented multidisciplinary research effort paull et al 1996 proc ocean drill program initial rep 164 623 pp paull c k matsumoto r wallace p j dillon w p eds 2000a proc ocean drill program sci results 164 ocean drilling program college station tx 459 pp most important for the progress of hydrochemical studies related to gas hydrates has been the growing awareness of the significance of diffusion modulated advective processes shaping the chemical and isotopic pore water profiles in hydrate zones this started with qualitative evidence for advective flow from drilling the hydrate bearing peru and hydrate free barbados active margins continued with the nankai trough accretionary prism the japan trench slope and the cascadia and costa rica active margins and culminated in the quantitative advection diffusion model of egeberg and dickens chem geol 153 1999 53 for the passive margin setting of the blake ridge advective flow regimes are different at active and passive margins as there is a tendency for the flow at active margins to be focussed along landward dipping thrust planes and faults in the wedge of imbricated thrust sheets that finds expression in a step pattern of the pore water profiles for passive margins but also for some active margin sites advection is from sources below the drilled section either through subvertical faults passive margins or from the decollement zone active margins we have learned that the well known coupled pore water anomalies that are ascribed to hydrate dissociation downward chlorinity decrease combined with 18 o increase hesse and harrison 1981 earth planet sci lett 55 1981 453 need not occur together in the presence of hydrates because the isotope effect may be overprinted by the effects of other reactions such as volcanic ash alteration or by the advection of low 18 o fluids however if the anomalies show up hydrates are present almost invariably with the exception of advected low cl high 18 o waters coming to terms with the effects of advection and diffusion has allowed successful modeling of the simpler hydrate affected pore water profiles at passive margins instrumental for modeling are chlorine isotopes which provide an effective tool to assess advection rates the egeberg and dickens model allows estimation of hydrate concentration and distribution in the subsurface because it separates the effects of advection diffusion and hydrate dissociation but critically depends on samples taken under in situ pressure and temperature conditions modeling the more complex pore water profiles of active margins is a challenge for the future compared to geophysical methods to estimate hydrate concentration the geochemical method gives minimum amounts

messinian salt fluxes into the present day eastern mediterranean implications for budget calculations and stagnation abstract although messinian evaporites underly almost the entire mediterranean fluxes related to these evaporites have not been included in water and salt budget calculations recently long piston cores recovered in the eastern mediterranean were sampled for pore waters in sufficient detail to allow a semi quantitative study of the sedimentary fluxes six different salt sources can be distinguished namely those coming from 1 normal pore waters 2 mud diapirs 3 sediments of formerly brine filled basins 4 brine filled basins 5 sediments from areas with a cobblestone topography and 6 salt dissolution holes based on the chloride versus depth profiles chloride fluxes from the sediment to the seafloor can be calculated the fluxes were multiplied by the estimated areas for the different salt sources to obtain the total flux these calculations show that mud diapirs and normal pore waters are the most important presently known salt sources in the eastern mediterranean compared with the salt input by evaporation the sedimentary salt input is rather small and has little influence on the models used for the water and salt budgets salt input from the sediment has a similar effect on the circulation of the eastern mediterranean water column as the introduction of huge amounts of fresh water at the surface the latter process may have resulted in the formation of sapropels the known sedimentary salt input is too low to be directly responsible for stagnation of the water column however once stagnation is initiated by other factors e g decrease of excess evaporation the extra salt input into the deep water will enhance the stagnation process therefore the circulation mechanism may be more sensitive to external changes than assumed until now

a gravity wave climatology for antarctica compiled from challenging minisatellite payload global positioning system champ gps radio occultations 1 the seasonal geographical and altitudinal dependence of gravity wave activity in the lower stratosphere over antarctica is presented gravity wave activity is estimated by calculating potential energy ep from radio occultation profiles obtained by the challenging minisatellite payload global positioning system champ gps experiment significant seasonal variation of wave activity is observed smaller wave activity in summer is attributed to waves with small phase velocities experiencing critical level filtering at other times of the year when wave activity is large less filtering occurs and the strong background wind is likely to cause doppler shifting of waves to longer vertical wavelengths which can reach larger amplitudes before saturating relationships between gravity wave activity and geographic location indicate that topography is a strong source for wave activity especially over the antarctic peninsula however wind rotation in this area was found to reduce the wave energy in summer at certain altitudes a strong enhancement of wave energy is observed at the edge of the polar vortex again reduced critical level filtering and doppler shifting in the area of the jet are likely to be major causes for this finding possible limitations to this study due to observational filtering are discussed

a study of stratospheric gw fluctuations and sporadic e at midlatitudes with focus on possible orographic effect of andes 1 longitudinal dependences of stratospheric gravity wave gw fluctuations and lower ionospheric irregularities sporadic e at midlatitudes are studied by means of radio occultation data of the global positioning system meteorology experiment gps met satellite mission the zonal average of temperature variance of gw fluctuations with vertical scales less than 7 km at northern midlatitudes is observed to be similar to that at southern midlatitudes but there is a significant interhemispheric difference in the longitudinal dependence of gw fluctuations the gps met data at northern midlatitudes show a rapid change of the gravity wave distribution from 25 to 35 km height resulting in a broad maximum of temperature variance located over the atlantic and eurasia we only find in the wave distribution at h 25 km some weak traces of possible orographic effects on the other hand the distribution of gw fluctuations at southern midlatitudes has a strong and sharp maximum over andes which is obviously due to orographic wave generation by the interaction of surface wind with the andean mountain ridge this observation of the new gps radio occultation technique is in agreement with previous measurements of spaceborne microwave and infrared limb sounders the amplitude of the average wave field increases with height over andes while the amplitude maximum moves westward against the prevailing wind the temperature fluctuations have an apparent dominant vertical wavelength of around 6 km in situ measurements by a balloon borne rawinsonde at ushuaia argentina 54 7 s 68 1 w are compared to a simultaneous gps met temperature profile the balloon observations of temperature and horizontal wind are interpreted by a large amplitude mountain wave propagating to the upper stratosphere wave characteristics and atmospheric background conditions are investigated in detail for this mountain wave observation finally the gps met experiment indicates enhanced sporadic e in the lower ionosphere over southern andes we assume that these plasma irregularities are generated by enhanced upward wave flux due to the possible orographic effect of andes

gravity wave characteristics in the southern hemisphere revealed by a high resolution middle atmosphere general circulation model abstractgravity wave characteristics in the middle to high latitude southern hemisphere are analyzed using simulation data over 3 yr from a high resolution middle atmosphere general circulation model without using any gravity wave parameterizations gravity waves have large amplitudes in winter and are mainly distributed in the region surrounding the polar vortex in the middle and upper stratosphere while the gravity wave energy is generally weak in summer the wave energy distribution in winter is not zonally uniform but it is large leeward of the southern andes and antarctic peninsula linear theory in the three dimensional framework indicates that orographic gravity waves are advected leeward significantly by the mean wind component perpendicular to the wavenumber vector results of ray tracing and cross correlation analyses are consistent with this theoretical expectation the leeward energy propagation extends to several thousand kilometers which explains part of the gravity wave distribution aro

seasonal variations in lower stratospheric gravity wave energy above the falkland islands 1 the gravity wavefield in the lower stratosphere between 15 km and 22 km altitude above mount pleasant airport 51 49 s 58 26 w on the falkland islands is studied using over 2100 high resolution radiosonde soundings from 2002 to 2010 the seasonal variation in vertical direction of propagation shows a small decrease in numbers of upward propagating waves that is related to critical level filtering however there is a very large increase in numbers of downward propagating waves between july and september this is attributed to the proximity of the edge of the polar vortex there is a seasonal variation in gravity wave energy density with a large peak during the austral autumn equinox this is markedly different to results in the literature both from rothera on the antarctic peninsula and stations on the main antarctic continent this seasonal pattern has been shown to be linked to variations in the sources of upward propagating gravity waves the seasonal variation in gravity wave characteristics above mount pleasant airport seen in our results suggests that the gravity wavefield in this region is determined by a combination of different gravity wave sources located above and below the lower stratosphere

carbon isotopic compositions of prokaryotic lipids as tracers of carbon cycling in diverse settings recent work has highlighted the ubiquity of bacteria and archaea and continues to affirm their significance in diverse biogeochemical processes the 13c values and distributions of diagnostic lipids derived from such microorganisms can provide insights into prokaryotic processes in modern settings and are one of the few means by which past prokaryotic processes in depositional settings can be elucidated here we present a brief review of prokaryotic lipids commonly observed in sediments and the controls on their carbon isotopic compositions we then present two case studies one of mediterranean cold seeps at which anaerobic oxidation of methane occurs and one of a holocene peat deposit in which a variety of aerobic and anaerobic microorganisms govern the degradation of organic matter these two studies illustrate the potential utility of compound specific carbon isotope analyses to deconvolute pathways of carbon flow in microbial communities

mud volcanism on the mediterranean ridge initial results of ocean drilling program leg 160 drilling during ocean drilling program leg 160 april may 1995 revealed important new evidence concerning the internal composition depositional processes and age of two mud volcanoes within the mediterranean ridge accretionary complex holes were drilled at ca 2000 m water depth on the crest areas across the flanks of the mud volcanoes and onto adjacent deep sea sediments the main depositional units forming the flanks of both mud volcanoes are debris flows mud breccias composed of a volumetrically dominant mud matrix containing clasts of mainly clay mudstone siltstone sandstone and limestone more variable muddy silty and sandy sediments were recovered from the crestal areas of both volcanoes the lowest mud volcano units drilled include well sorted medium to coarse grained sediments mainly composed of clay that were deposited partly by turbidity currents the mud volcano sediments are associated with background deep sea sediments that allow dating by using microfossils the milano mud volcano is at least 1 75 ma and is apparently now dormant and the napoli mud volcano started prior to or during 1 5 1 2 ma and is currently active pore fluids at napoli and to a lesser extent at milano indicate the presence of halite of presumed latest miocene age beneath the volcanoes hydrocarbon gas is venting from the crest of the napoli mud volcano and gas was also detected on the crest of the milano mud volcano methane hydrates clathrates are also inferred to exist beneath the crest of the milano mud volcano the mud volcanoes are located above a shallowly dipping subduction zone in an area where the accretionary complex is apparently being thrust northward over a backstop of continental crust related to initial collision of the african and eurasian plates mud volcanism may have begun when backthrusting punctured a seal of latest miocene evaporites allowing the escape of overpressured materials

new aim cips global observations of gravity waves near 50 55 km this paper describes a new data set from the aeronomy of ice in the mesosphere aim cloud imaging and particle size cips instrument from which gravity waves gws at an altitude of 50 55 km can be inferred cips is sensitive to gws with horizontal wavelengths from 15 to 600 km and vertical wavelengths longer than 15 km several examples of gws in cips observations are shown including waves associated with the andes mountains island topography convection the polar night jet and the tropospheric jet stream gw signatures in the cips data are shown to agree well with near coincident but lower altitude measurements from the atmospheric infrared sounder airs in june of 2016 results suggest the power of combining cips measurements with those from other instruments to investigate gw filtering and propagation the cips data set opens new areas of inquiry enabling comprehensive investigations of gws in the middle atmosphere on a near global scale

hydrate occurrence in europe a review of available evidence abstract large national programs in the united states and several asian countries have defined and characterised their marine methane hydrate occurrences in some detail but european hydrate occurrence has received less attention the european union funded project marine gas hydrate an indigenous resource of natural gas for europe migrate aimed to determine the european potential inventory of exploitable gas hydrate to assess current technologies for their production and to evaluate the associated risks we present a synthesis of results from a migrate working group that focused on the definition and assessment of hydrate in europe our review includes the western and eastern margins of greenland the barents sea and onshore and offshore svalbard the atlantic margin of europe extending south to the northwestern margin of morocco the mediterranean sea the sea of marmara and the western and southern margins of the black sea we have not attempted to cover the high arctic the russian ukrainian and georgian sectors of the black sea or overseas territories of european nations following a formalised process we defined a range of indicators of hydrate presence based on geophysical geochemical and geological data our study was framed by the constraint of the hydrate stability field in european seas direct hydrate indicators included sampling of hydrate the presence of bottom simulating reflectors in seismic reflection profiles gas seepage into the ocean and chlorinity anomalies in sediment cores indirect indicators included geophysical survey evidence for seismic velocity and or resistivity anomalies seismic reflectivity anomalies or subsurface gas escape structures various seabed features associated with gas escape and the presence of an underlying conventional petroleum system we used these indicators to develop a database of hydrate occurrence across europe we identified a series of regions where there is substantial evidence for hydrate occurrence some areas offshore greenland offshore west svalbard the barents sea the mid norwegian margin the gulf of cadiz parts of the eastern mediterranean the sea of marmara and the black sea and regions where the evidence is more tenuous other areas offshore greenland and of the eastern mediterranean onshore svalbard offshore ireland and offshore northwest iberia we provide an overview of the evidence for hydrate occurrence in each of these regions we conclude that around europe areas with strong evidence for the presence of hydrate commonly coincide with conventional thermogenic hydrocarbon provinces

observational evidence of ionospheric migrating tide modification during the 2009 stratospheric sudden warming 1 in this paper modifications of the ionospheric tidal signatures during the 2009 stratospheric sudden warming ssw event are studied by applying atmospheric tidal analysis to ionospheric electron densities observed using radio occultation soundings of formosat 3 cosmic the tidal analysis indicates that the zonal mean and major migrating tidal components dw1 sw2 and tw3 decrease around the time of the ssw with 1 5 4 hour time shifts in the daily time of maximum around eia and middle latitudes the typical ionospheric ssw signature a semi diurnal variation of the ionospheric electron density featuring an earlier commencement and subsidence of eia can be reproduced by differencing the migrating tides before and during the ssw period our results also indicate that the migrating tides represent 80 of the ionospheric tidal components at specific longitudes suggesting that modifications of the migrating tides may be the major driver for producing ionospheric changes observed during ssw events accounting for greater variability than the nonmigrating tides that have been the focus of previous studies

mud volcanoes and gas hydrates in the anaximander mountains eastern mediterranean sea abstract detailed multibeam sedimentological and geophysical surveys provide ample new data to confirm that the anaximander mountains eastern mediterranean are an important area for active mud volcanism and gas hydrate formation more than 3000 km of multibeam track length was acquired during two recent missions and 80 gravity and box cores were recovered morphology and backscatter data of the study area have better resolution than previous surveys and very detailed morphology maps have been made of the known targeted mud volcanoes amsterdam kazan and kula especially the amsterdam crater and the related mud breccia flows gas hydrates collected repeatedly from a large area of amsterdam mud volcano at a sub bottom depth of around 0 3 1 5 m resemble compacted snow and have a rather flaky form new gas hydrate sites were found at amsterdam mud volcano including the mud flow sloping off to the south gas hydrates sampled for the first time at kazan mud volcano are dispersed throughout the core samples deeper than 0 3 m and display a rice like appearance relative chronology and ams dating of interbedded pelagic sediments late holocene hemipelagic sapropel layer s1 and ash layers within the mud flows indicate that successive eruptions of kula mud volcano have a periodicity of about 5 10 kyrs new mud volcanoes identified on the basis of multibeam backscatter intensity were sampled documented as active and named athina and thessaloniki gas hydrates were sampled also in thessaloniki mud volcano the shallowest 1264 m among all the active mediterranean sites at the boundary of the gas hydrate stability zone biostratigraphical analyses of mud breccia clasts indicated that the source of the subsurface sedimentary sequences consists of late cretaceous limestones paleocene siliciclastic rocks eocene biogenic limestones and miocene mudstones rough estimations of the total capacity of the anaximander mud volcanoes in methane gas are 2 56 6 40 km3

the effects of transient rheology on the interpretation of lower mantle viscosity we have reexamined the role played by transient rheology in the interpretation of mantle viscosity this investigation has been carried out by comparing the amplitude responses with the data of secular variation of the relative sea level histories at sites well within the ice margins and at the ice margin like the city of boston a linear burgers body rheology has been assumed in the lower mantle the data near the edge of the ice load proves most sensitive to the transient viscosity structure the non monotonic behavior of sea level data near boston can be explained both by a steady state lower mantle viscosity of 1022p with a thick lithosphere and also by a transient lower mantle rheology but with a thin lithosphere the long term viscosity of the lower mantle in this second model has a steady state value of around 5 1023p

active post depositional oxidation of the most recent sapropel s1 in sediments of the eastern mediterranean sea abstract over a wide area of the eastern mediterranean basin two mn rich layers have been observed above the most recent sapropel s1 one immediately above the sapropel top and one a few centimetres closer to the sediment surface different mechanisms have been proposed to explain the occurrence of these two mn peaks either both peaks have a diagenetic origin in which case the upper mn peak is actively forming or the lower peak is actively forming and the upper peak has a different formation mechanism high resolution porewater including a gel sampler used for the first time in marine sediments and solid phase data are now used to demonstrate that the oxidation front is located at the level of the lower mn peak which therefore is presently being formed a barium organic carbon relationship is used to calculate the initial organic carbon profile of the s1 sapropel the palaeoproductivity profiles generated by this method demonstrate that the original sapropel unit was bounded by the upper mn peak this implies that the interval between the two mn peaks where a low organic carbon content is now observed was originally part of the sapropel the initially deposited organic carbon has been oxidised by a progressive downwards moving oxidation front the penetration depth of this oxidation front i e the distance between the two mn peaks is mainly determined by the organic carbon content the sediment accumulation rate and the bioturbation depth the upper mn peak appears to have formed as a result of either mn precipitation upon oxygenation of previously anoxic eastern mediterranean deep water or preservation of a surficial mn peak at the end of the high productivity episode in either case the upper mn peak marks the end of sapropel formation as indicated by the ba profiles this means that formation of the s1 sapropel ceased more recently than is indicated by radiocarbon dating of the visible top of s1

wave activity at ionospheric heights above the andes mountains detected from formosat 3 cosmic gps radio occultation data an estimation of the ionospheric wave activity derived from 4 years of formosat 3 cosmic gps taiwan s formosa satellite mission 3 constellation observing system for meteorology global positioning system radio occultation electron density data is presented a systematic enhancement at the eastern side of the andes range with respect to the western side is observed a fitting method to remove the wavelike component from each measured profile and estimate the wave activity is described the differential effect introduced by the action of orography on the generation to the eastern side of the andes of mountain waves deep convection waves or even secondary waves aloft after momentum deposition in the middle atmosphere is suggested

role of gravity waves in the spatial and temporal variability of stratospheric temperature measured by cosmic formosat 3 and rayleigh lidar observations 1 this study utilizes cosmic satellite and lidar observations to examine the spatial and temporal variability of stratospheric temperature at a number of scales the geographic variation of the rms temperature difference between pairs of cosmic profiles shows a strong correspondence to previous climatologies of gravity wave activity in addition the second order structure functions we form can be directly related to the horizontal wave number power spectrum these structure functions for different seasons and altitudes display a close correspondence to previous studies which examined the form of the horizontal wave number power spectra our analysis suggests that the wavefield may be particularly affected by changes in the zonal wind between 15 and 25 km and that the wind reversal between tropospheric westerlies and stratospheric easterlies in summer strongly contributes to critical level filtering inspection also shows that longer horizontal wavelength waves are preferentially removed in this region at low altitudes the variability related to gravity waves shows a remarkably similar pattern as a function of horizontal separation in both hemispheres but is quite different at higher altitudes such contrast implies that seasonal variability at higher altitudes may be dominated by changes in propagation conditions in the lower stratosphere examination of temperature variability as a function of spatial and temporal separation indicates that gravity wave activity dominates stratospheric temperature variability and this has impacts on validation study site selection for example validation exercises in the summer hemisphere stratosphere are likely to be less affected by geophysical variability than those in the winter hemisphere

new evidence of extensive active mud volcanism in the anaximander mountains eastern mediterranean the athina mud volcano a 3000 km2 multibeam survey was carried out on the eastern anaximander mountains mts eastern mediterranean the objective was to obtain detailed bathymetry of known mud volcanoes and identify new sites of active mud volcanism in the area n nw of the amsterdam mud volcano mv several mounds and cone like morphological irregularities with a height of few tens of meters to about one hundred meters were detected and considered as potential mvs on the basis of their distinctive backscattered character a group of two mounds was selected the northern mound was sampled documented as active and named accordingly athina mv these new findings strongly support the presence of extensive active mud volcanism in the anaximander mountains especially in the area north of the amsterdam mv

geochemical evidence of a massive slide in the southern norwegian sea during the 1981 cruise of the ms tyro to the southern norwegian basin several piston cores were collected for sedimentological research some of these were available for geochemical study fig 1 in laboratory analyses the pore water composition of one of these cores showed evidence of input of non saline water whereas pore water in other cores from the same basin did not give any indication of dilution with fresh water careful examination of the chemical constituents of the pore water and some parameters of the sediment gives convincing evidence for the origin of the fresh water the presence of non saline water can be attributed to a massive slide of a coastal fresh to brackish sediment slab with preservation of structural and pore water composition this sliding is thought to have taken place about 12 000 to 15 000 years bp

global gravity wave activity in the tropopause region from champ radio occultation data 1 we discuss the global gravity wave gw activity expressed by the specific potential energy in the altitude range from 5 km below to 10 km above the tropopause derived from gps radio occultation data from champ 2001 2008 the gw analysis is based on vertical detrending of the individual measured temperature profiles by applying a gaussian filter in two different ways i filtering of the complete temperature profiles and ii separate filtering of the profiles for the tropospheric and lower stratospheric parts the separate filtering method significantly reduces the usually observed wave activity enhancement in the tropopause region which highly depends on the performance of the complete filtering method to reproduce the change in the temperature gradient at the tropopause we only consider vertical wavelengths less than 10 km the global mean potential energy in the tropopause region deduced with these different background temperatures will be analyzed differences will be emphasized and possible error sources of the new method will be considered

gravity waves above andes detected from gps radio occultation temperature profiles mountain forcing 1 a significant wave activity in the upper troposphere and lower stratosphere at midlatitudes 30 40s above the andes range was recently detected from global positioning system radio occultation gps ro temperature profiles retrieved from sac c satelite de aplicaciones cientficas c and champ challenging minisatellite payload satellites previously large amplitude long vertical wavelength structures have been reported in this region as detected from other limb sounding devices and have been identified as mountain waves mws the capability of gps ro observations to detect typical mws with horizontal wavelengths shorter than 150 km as well as the proper association of the observed wave activity to mountain forcing is put in doubt other three possible sources are discussed in particular the generation of inertio gravity waves by geostrophic adjustment near to a permanent jet situated above the mountains may constitute another important mechanism in this region these waves may possess longer horizontal and perhaps shorter vertical wavelengths than those typically expected in mws and could be more easily detected from limb sounding profiles the jet mechanism will be discussed in a second paper

evidence of mesospheric gravity waves generated by orographic forcing in the troposphere 1 we report on the first imaging observations of stationary mesospheric gravity waves in the three nightglow emissions of oh 695 1050 nm na 589 3 nm and o 1s 557 7 nm the waves were observed in all sky images at the el leoncito observatory elo argentina 31 8 s 69 3 w during the period of 1 8 july 2008 over the course of each night the band like wave features exhibited a zero or near zero observed horizontal phase speed and had lifetimes of several hours these factors coupled with the winds measured locally and the orientation of the waves to the andes mountain range located nearby suggested that the waves were mountain waves generated by 70 ms 1 eastward winds flowing over the andes

saturated gravity wave spectra measured with balloons in mendoza argentina spectral results from a sounding of temperature and wind velocity between 11 9 and 23 1 km performed with an open type stratospheric balloon near the andes mountains are reported the use of this kind of balloons and high performance instruments allowed to attain better spatial resolution around 2 5 meters during the descent than previous results and other sounding techniques this high resolution permitted to study the complete interval of altitude data in three consecutive subintervals below around and above the tropopause each of these subintervals shows different saturation characteristics some differences have been found with the general pattern of power spectral densities reported by different theories a large amplitude wave of around 1 8 km and possibly originated in the mountain relief is clearly observed in the temperature vertical and shear wind velocity components

subducted slabs and the geoid constraints on mantle rheology and flow geoid anomalies are primarily the result of the density contrasts driving mantle convection and plate motion the total geoid anomaly resulting from a given density contrast in a convecting earth is affected by the mass anomalies associated with the flow induced deformation of the upper surface and internal compositional boundaries as well as by the density contrast itself these boundary deformations and hence the total gravity field depend on the radial distribution of effective viscosity if the internal density contrasts can be estimated as is the case for subducted slabs useful constraints can be placed on the depth and on the variation of viscosity with depth of the convecting system the degree 4 9 components of the observed long wavelength geoid are highly correlated with those predicted by a density model for seismically active subducted slabs the positive sign of the correlation requires that the effective viscosity increases with depth by a factor of 30 or more the amplitude of the correlation cannot be explained by the density contrasts associated with just the seismically active parts of subducted slabs however the amplitude can be explained if the density contrasts associated with subduction extend into the lower mantle or if old lithosphere is piled up at the base of the upper mantle beneath subduction zones to a thickness in excess of 350 km over horizontal distances of thousands of kilometers mantlewide convection in a mantle that has a viscosity increasing with depth provides a simple explanation of the long wavelength geoid anomalies over subduction zones

life at cold seeps a synthesis of biogeochemical and ecological data from kazan mud volcano eastern mediterranean sea recent field observations have identified the widespread occurrence of fluid seepage through the eastern mediterranean sea floor in association with mud volcanism or along deep faults gas hydrates and methane seeps are frequently found in cold seep areas and were anticipated targets of the medinaut medineth initiatives the study presented herein has utilized a multi disciplinary approach incorporating observations and sampling of visually selected sites by the manned submersible nautile and by ship based sediment coring and geophysical surveys the study focuses on the biogeochemical and ecological processes and conditions related to methane seepage especially the anaerobic oxidation of methane aom associated with ascending fluids on kazan mud volcano in the eastern mediterranean sampling of adjacent box cores for studies on the microbiology biomarkers pore water and solid phase geochemistry allowed us to integrate different biogeochemical data within a spatially highly heterogeneous system geophysical results clearly indicate the spatial heterogeneity of mud volcano environments results from pore water geochemistry and modeling efforts indicate that the rate of aom is similar to 6 mol m 2 year 1 which is lower than at active seep sites associated with conditions of focused flow but greater than diffusion dominated sites furthermore under the non focused flow conditions at kazan mud volcano advective flow velocities are of the order of a few centimeters per year and gas hydrate formation is predicted to occur at a sediment depth of about 2 m and below the methane flux through these sediments supports a large and diverse community of micro and macrobiota as demonstrated by carbon isotopic measurements on bulk organic matter authigenic carbonates specific biomarker compounds and macrofaunal tissues because the aom community appears to be able to completely oxidize methane at the rate it is seeping through the sediments ultimate sinks for methane in this environment are authigenic carbonates and biomass significant differences in organic geochemical data between this site and those of other cold seep environments even within the eastern mediterranean mud volcanoes indicate that the microbiological communities carrying out aom varies depending on specific conditions such as methane flux and salinity c 2004 elsevier b v all rights reserved

gravity waves and ionospheric irregularities over tropical convection zones observed by gps met radio occultation gps met observations of the tropical atmo sphere of the southern hemisphere 5 st o 25 s during february 1997 are analysed when a high amount of con vective tropospheric water vapor is at these latitudes en hanced gravity wave activity of the lower stratosphere at h 22 28 km is associated to areas of increased tropospheric water vapor pressure at h 4 6 km regarded as a measure of tropical convection sporadic e and other ionospheric irregularities vertical scales less than 7 km of the meso sphere lower thermosphere are observed to be highly cor related to gravity wave activity in the lower stratosphere and to tropical convection zones we find 4 areas of en hanced ionospheric irregularities and stratospheric wave ac tivity over pacific around 140 w brazil 50 w africa 40 e and indonesia australia 110 e

shipboard routine and pressure filtration system for pore water extraction from suboxic sediments abstract a shipboard working procedure for the handling and porewater extraction of suboxic sediments is outlined in addition a detailed description is given of the shipboard pressure filtration system that has been used to extract porewater this procedure in combination with the pressure filtration system has been demonstrated to produce reliable porewater from suboxic sediments

mantle rheology and satellite signatures from present day glacial forcings we study the changes of the long wavelength portion of the earth s gravity field as a result of present day gladal discharges and the possible growth of the antarctic ice sheet we employ both maxwell and burgers body rheologies and find that there are significant differences in the responses between the two rheologies for time spans less than a century both present day gladal forcing and the ice buildup on antarctica can cause non negligible perturbations in j 2 of about one third the observed amount the contributions from the two mechanisms have opposite signs in j 2 only for i 3 and 6 do these cryospheric contributors act in concert with one another in disturbing the gravity field ali other degree harmonics up to 1 9 have opposite signs from these two excitations for a steady state lower mantle viscosity of 1022 pa s j 3 can attain a maximum value of around 1 5 x lo i1 yr 1 and j a value of 1 3 x io il yr i for current forcings these have signs opposite to those predicted for pleistocene deglaciation ali harmonics up to i 9 are sensitive to variations of the steady state vis cosity in the lower mantle even for time scales shorter than 100 years it is proposed that detailed satellite monitoring of present day ice movements in conjunction with geodetic satellite missions will eventually pro vide a viable alternative for estimating deep mantle viscosity useful in mantle convection models

timed saber observations of global gravity wave climatology and their interannual variability from stratosphere to mesosphere lower thermosphere the present study for the first time reports the global gravity wave activity in terms of their potential energy derived from timed saber observations right from the stratosphere to the mesosphere lower thermosphere mlt region the potential energy profiles obtained from saber temperature are validated by comparing them with ground based lidar observations over a low latitude site gadanki 13 5 n 79 2 e the stratospheric and mesospheric global maps of gravity wave energy showed pronounced maxima over high and polar latitudes of the winter hemisphere the interannual variability of the stratospheric gravity wave activity exhibited prominent annual oscillation over mid latitudes the equatorial gravity wave activity exhibited quasi biennial oscillation in the lower stratosphere and semi annual oscillation in the upper stratosphere the mlt region maps revealed summer hemispheric maxima over polar latitudes and secondary maxima over the equatorial region the results are discussed in the light of present understanding of global gravity wave observations the significance of the present study lies in emphasizing the importance of satellite measurements in elucidating gravity waves which is envisaged to have profound impact on parameterizing these waves

deep sea bottom simulating reflectors calibration of the base of the hydrate stability field as used for heat flow estimates ocean drilling program and deep sea drilling project downhole data from three areas the southwestern japan nankai margin the continental slope off peru and the blake bahama outer ridge provide temperature calibrations for bottom simulating reflectors bsr that mark the base of a clathrate hydrate stability field the inferred temperatures at bsrs provide an important reference for the mapping of geothermal gradient and heat flow from subduction zone accretionary sedimentary wedges the borehole results provide information on which stability field is applicable for the bsrs and thus calibrate the heat flow estimates while an ideal calibration has not been possible the bsr temperatures at the three sites in the temperature range 25 27 c have been estimated with uncertainties of 0 7 to 2 0 c the temperatures correspond closely to the laboratory dissociation temperatures for pure water pure methane hydrate at equivalent pressures no laboratory data are available for seawater salinity and methane at equivalent pressures but extrapolation from lower pressures gives temperatures 1 2 c lower which is just significantly different the data also could be explained by the stability curve for seawater salinity and methane with about 7 co2 or with a small amount of higher hydrocarbons but most hydrate samples that have been recovered by deep sea drilling have contained almost pure methane the uncertainties in the temperature at the bsr should contribute no more than 5 error in heat flow estimates from bsr depths if the pure water methane stability field is used

limb sounders tracking topographic gravity wave activity from the stratosphere to the ionosphere around midlatitude andes several studies have shown that the surroundings of the highest andes mountains at mid latitudes in the southern hemisphere exhibit gravity waves gw generated by diverse sources which may traverse the troposphere and then penetrate the upper layers if conditions are favorable there is a specific latitude band where that mountain range is nearly perfectly aligned with the north south direction which favors the generation of wavefronts parallel to this orientation this fact may allow an optimization of procedures to identify topographic gw in some of the observations we analyze data per season to the east and west of these andes latitudes to find possible significant differences in gw activity between both sectors gw effects generated by topography and convection are expected essentially on the eastern side we use satellite data from two different limb sounding methods the global positioning system gps radio occultation ro technique and the sounding of the atmosphere using broadband emission radiometry saber instrument which are complementary with respect to the height intervals in order to study the effects of gw from the stratosphere to the ionosphere activity becomes quantified by the gw average potential energy in the stratosphere and mesosphere and by the electron density variance content in the ionosphere consistent larger gw activity on the eastern sector is observed from the stratosphere to the ionosphere night values however this fact remains statistically significant at the 90 significance level only during winter when gw generated by topography dominate the eastern sector on the contrary it is usually assumed that orographic gw have nearly zero horizontal phase speed and will therefore probably be filtered at some height in the neutral atmosphere however this scheme relies on the assumption that the wind is uniform and constant our results also suggest that it is advisable to separate night and day cases to study gw in the ionosphere as it is more difficult to find significant statistical differences during daytime this may happen because perturbations induced by gw during daytime are more likely to occur in a disturbed environment that may hinder the identification of the waves