productivity regime and phytoplankton size structure in the arabian sea abstract the productivity regime and size structure of phytoplankton are described for three different epipelagic systems in the arabian sea during the inter monsoon period in spring 1987 1 the coast of oman 2 the central arabian sea and 3 the shelf off pakistan these results are related to the functioning of the specific ecosystem off the coast of oman the transition from a surface maximum of autotrophic biomass and production to a more oligotrophic system with a chlorophyll subsurface maximum was observed concomitantly the size spectrum changed towards a higher significance of picoplankton in the central arabian sea a typical oligotrophic system with a pronounced subsurface maximum of autotrophic biomass and primary production was encountered here the epipelagic system could be divided into two distinct sub systems the surface layer regenerated production the predominance of picophytoplankton and minor losses due to sedimentation thus a closed system and the subsurface maximum layer at the nutricline characterized by higher sedimentation losses and more diatoms both sub systems showed about the same productivity the turnover in the surface layer having been much greater than in the subsurface maximum the system on the shelf off pakistan is seen as a decay stage of the open ocean system when water from offshore is transported onto the shelf during the onset of monsoon winds

inertia gravity waves observed in the lower stratosphere over macquarie island abstract this study examines the properties of inertia gravity waves observed in the lower stratosphere over macquarie island how these properties vary with season and the likely source of the waves the waves are observed in high resolution upper air ozonesonde soundings of wind and temperature released from macquarie island during the 1994 ashoe maesa program the properties of the inertia gravity waves observed in the soundings are quantified using hodograph and rotary spectral analyses the analyzed waves have horizontal wavelengths between 100 and 1000 km vertical wavelengths between about 1 and 7 km intrinsic frequencies between f and 2f and horizontal trace speeds between 50 and 30 m s 1 there appears to be a seasonal cycle in the inertia gravity wave activity in the lower stratosphere the minimum being in the austral winter when the background zonal flow is strong and westerly and its vertical shear is positive in contrast the variance of the horizontal perturbation winds does not show a

the seasonal cycle of lower tropospheric gravity wave activity at davis antarctica 69 s 78 e abstracta vhf wind profiling radar located at davis in coastal east antarctica 69 s 78 e collected data from september 2009 to august 2011 in the lower troposphere gravity wave activity is quantified using the radar s wind velocity variances era interim and antarctic mesoscale prediction system amps forecast output are used to understand the gravity wave activity in the context of the synoptic scale meteorology and to identify the likely source of the observed gravity waves the seasonal cycle of lower tropospheric gravity wave activity 2 0 3 2 km altitude obtained from the radar data for waves with ground based periods of 16 min 12 8 h reveals a maximum in winter and a minimum in summer the largest gravity wave activity corresponds in time to the presence of a surface depression centered north of davis that directs strong northeasterly winds along the antarctic coastline case studies indicate that these winds interact with an ice ridgeline located around 60 km northeast and upwind of davis th

on the relation between gravity waves and wind speed in the lower stratosphere over the southern ocean abstractthe relationship between gravity wave momentum fluxes and local wind speed is investigated for oceanic regions at high southern latitudes during austral spring the motivation is to better describe the gravity wave field by identifying a simple relationship between gravity waves and the large scale flow the tools used to describe the gravity waves are probability density functions of the gravity wave momentum fluxes three independent datasets covering high latitudes in the southern hemisphere springtime are analyzed simulations with a mesoscale model analyses from the european centre for medium range weather forecasts and observations from superpressure balloons of the concordiasi campaign in 2010 a remarkably robust relation is found with stronger momentum fluxes much more likely in regions of strong winds the tails of the probability density functions are well described as lognormal the median momentum flux increases linearly with background wind speed for winds stronger than 50 m s 1

size fractionated primary production and nitrogen assimilation in the northwestern indian ocean abstract rates of phytoplankton production and nitrogen assimilation were measured at various stations along a transect in the northwestern indian ocean from near the equator northwards into the upwelling system off the arabian peninsula during september october 1986 the measurements were made using in situ incubation techniques with the simultaneous use of 14c and 15n isotopes samples were fractionated after the incubations into three size classes 0 2 0 8 m 0 8 5 0 m and 5 0 m for the 14c incubations and 5 m for the 15n incubations the assimilation of nitrate and ammonium was measured these measurements were supported by a detailed description of the horizontal and vertical distributions of chlorophyll temperature and underwater light field by the deployment of a towed undulating oceanographic recorder rates of primary production ranged from approximately 0 5 g c m 2 day 1 at the equator reducing to 2 5 in the upwelling region off the coast of oman total nitrogen assimilation followed a similar pattern very significant variations in the size distribution of the activity of the plankton were observed over 75 of the carbon and nitrogen assimilation was in the

gravity waves generated by a tropical cyclone during the step tropical field program a case study overflights of a tropical cyclone during the australian winter monsoon field experiment of the stratosphere troposphere exchange project step show the presence of two mesoscale phenomena a vertically propagating gravity wave with a horizontal wavelength of about 110 km and a feature with a horizontal scale comparable to that of the cyclone s entire cloud shield wavelength of 250 km or greater the larger feature is fairly steady though its physical interpretation is ambiguous the 110 km gravity wave is transient having maximum amplitude early in the flight and decreasing in amplitude thereafter its scale is comparable to that of 100 to 150 km diameter cells of low satellite brightness temperatures within the overall cyclone cloud shield these cells have lifetimes of 4 5 to 6 hours aircraft flights through the anvil show that these cells correspond to regions of enhanced convection higher cloud altitude and upwardly displaced potential temperature surfaces a three dimensional transient linear gravity wave simulation shows that the temporal and spatial distribution of meteorological variables associated with the 110 km gravity wave can be simulated by a slowly moving transient forcing at the anvil top having an amplitude of 400 600 m a lifetime of 4 5 6 hours and a size comparable to the cells of low brightness temperature the forcing amplitudes indicate that the zonal drag due to breaking mesoscale transient convective gravity waves is definitely important to the westerly phase of the stratopause semiannual oscillation and possibly important to the easterly phase of the quasi biennial oscillation there is strong evidence that some of the mesoscale gravity waves break below 20 km as well the effect of this wave breaking on the diabatic circulation below 20 km may be comparable to that of above cloud diabatic cooling

simulation of inertia gravity waves in a poleward breaking rossby wave abstract poleward breaking rossby waves often induce an upper level jet streak over northern europe dominant inertia gravity wave packets are observed downstream of this jet the physical processes of their generation and propagation in such a configuration are investigated with a mesoscale model the study is focused on an observational campaign from 17 to 19 december 1999 over northern germany different simulations with the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 have been performed for a high resolution process study three domains were set up that encompass the evolution of rossby waves and that of inertia gravity waves to minimize the impact of model damping the horizontal and vertical resolution has been adjusted appropriately with a novel statistical approach the properties of inertia gravity wave packets have been estimated this method uses the horizontal divergence field and takes into account the spatial e

airglow imager observations of atmospheric gravity waves at alice springs and adelaide australia during the darwin area wave experiment dawex 1 the darwin area wave experiment occurred in australia from october to december 2001 an objective was to characterize the atmospheric gravity wave field produced from intense convective activity that is routinely observed around darwin during november and december two airglow imagers were sited at adelaide and at alice springs each located over 1000 km south of darwin waves were observed at the mesopause region propagating predominantly toward the southeast with some going to the northwest but with none observed going from east to west the lack of waves propagating toward the west suggests some wind filtering mechanism below 80 km altitude waves observed over alice springs were analyzed in detail on three nights on 16 november they were seen propagating toward the northwest it is proposed that they were generated by dynamical events associated with a cutoff low pressure system present over southwest australia on 17 and 19 november the observations are consistent with wave generation by convective activity present in the darwin area thus as proposed by walterscheid et al 1999 and hecht et al 2001a the ducting of waves from distant sources is shown to be a viable explanation for the quasi monochromatic waves frequently observed in airglow observations walterscheid et al 1999 suggested that ducting of waves from the extensive region of deep cumulus convection over northern australia explained the strong poleward directionality seen in the summer months the present study suggests that propagation from northern australia is selective and ducted waves from this region may not be the primary source of waves over adelaide when convection is occurring over central australia

gravity waves around the subtropical jet of the southern winter in an atmospheric general circulation model 1 gravity wave gw activities around the subtropical jet of the southern winter june are analyzed using atmospheric general circulation model outputs of t106l60 in order to clarify roles of gws in maintaining the zonal mean zonal wind dominant gws are characterized with periods of 10 24 hours relative to the ground and with horizontal and vertical wavelengths of about 600 700 km and 2 2 4 4 km respectively these gws propagate both upward and downward from the jet and westward relative to the mean zonal wind most of the upward propagating waves do not reach the upper stratosphere due to negative vertical wind shear of the zonal wind in the lower stratosphere dominant upward fluxes of easterly momentum due to the non stationary gws extend zonally along 30 s above the jet remarkable ep flux convergence due mostly to these gws is seen around 100 hpa at 30 s and explains up to 30 of the total ep flux convergence

millennial scale oscillation of denitrification intensity in the arabian sea during the late quaternary and its potential influence on atmospheric n2o and global climate the intensity of denitrification in the arabian sea during the last 65 kyr is reconstructed using high resolution 15 n records of three sediment cores in conjunction with other geochemical tracers for water column oxygenation and productivity the results reveal a close link to the greenland ice core record with low or absent water column denitrification during the last glacial maximum the stadials and at the time of the heinrich events including the younger dryas in contrast denitrification was high during the holocene and the interstadials the intensification of denitrification is related to stronger sw monsoonal upwelling which enhances organic matter flux and degradation resulting in a strengthening of the midwater oxygen deficiency such a combination of enhanced upwelling and denitrification has also been implied for the eastern tropical north pacific etnp where these events occur during the holocene and to some extent during the interstadials too today the arabian sea and the etnp together contribute substantially to the global marine water column denitrification and a significant fraction of the ocean atmosphere n 2 o flux originates from these areas changes in n 2 o emissions from these areas could thus have effected the recently described stadial interstadial variations in the atmospheric concentration of this greenhouse gas as deduced from ice cores moreover denitrification is the major sink for oceanic nitrate and provides a primary control for the oceanic nutrient inventory which in turn influences global primary productivity and co 2 sequestration by the biological pump short term switches between a nondenitrification mode and a denitrification mode in these marine regions therefore have an impact on global climate

radiosonde observations of gravity waves in the lower stratosphere over davis antarctica radiosonde observations made from davis station antarctica 68 6 s 78 0 e between 2001 and 2012 are used to compile a climatology of lower stratosphere inertial gravity wave characteristics wavelet analysis extracts single wave packets from the wind and temperature perturbations wavelet parameters combined with linear gravity wave theory allow for the derivation of a wide range of wave characteristics observational filtering associated with this analysis preferentially selects inertial gravity waves with vertical wavelengths less than 2 3 km the vertical propagation statistics show strong temporal and height variations the waves propagate close to the horizontal and are strongly advected by the background wind in the wintertime notably around half of the waves observed in the stratosphere above davis between early may and mid october propagate downward this feature is distributed over the observed stratospheric height range based on the similarity between the upward and downward propagating waves and on the vertical structure of the nonlinear balance residual in the polar winter stratosphere it is concluded that a source due to imbalanced flow that is distributed across the winter lower stratosphere best explains the observations calculations of kinetic and potential energies and momentum fluxes highlight the potential for variations in results due to different analysis techniques

palaeozoic palaeomagnetic results from scotland and their bearing on the british apparent polar wander path abstract palaeomagnetic studies of the lower and upper old red sandstone ors western midland valley indicate the presence of two principal remanence components ib and hb both components can be demonstrated to be of secondary post upper ors origin component ib compares with palaeomagnetic results from upper carboniferous permian dykes and sills in the midland valley whereas hb conforms to palaeomagnetic results from the overlying lower carboniferous lavas a combination of hb components from the lower upper ors and lower carboniferous lavas western midland valley yields a relative pole position near s14 and e322 which compares well with lower carboniferous data from the kinghorn and burntisland lavas eastern midland valley s14 and e332 from kinghorn the palaeomagnetic data can be demonstrated to be of primary lower carboniferous origin seen in conjunction with the british polar wander path the lower carboniferous poles reported here seemingly dissociate middle upper devonian and upper silurian lower devonian poles owing to the lack of magnetic age control in the middle upper devonian data base it is argued that the majority of middle upper devonian data from the british isles should be reconsidered as carboniferous magnetic overprints this carries the implication that any tectonic models based on middle upper devonian palaeomagnetic results should be considered highly suspicious

gravity waves above the andes detected from gps radio occultation temperature profiles jet mechanism 1 a significant wave activity wa in the upper troposphere and lower stratosphere mainly during winter was detected at midlatitudes in the southern hemisphere 30 40s above the andes range from an analysis of global positioning system radio occultation gps ro temperature profiles retrieved by champ challenging minisatellite payload and sac c satelite de aplicaciones cientificas c low earth orbit leo satellites between may 2001 and february 2006 the possible main gravity wave sources in this region are i orographic forcing ii geostrophic adjustment and iii deep convection the available vertical resolution of gps ro soundings does not rule out any of these alternatives based on satellite imaginary the wa enhancements cannot be attributed to deep convection events inertia gravity waves igws could be generated after a geostrophic adjustment process following a perturbation of the zonal jet situated above the andes mountains by mountain waves mws the monthly wa intensity follows the zonal wind velocity strength according to its seasonal variability at jet altitudes as the gps leo lines of sight are roughly meridionally aligned and the morphology of the andes at middle latitudes is predominantly north south it was possible to detect mws as well as igws from gps ro temperature profiles this characteristic does not apply for other mountain range alignments from the analysis of a numerical simulation at the time and location of a single ro event with very strong wa two main modes of oscillation with horizontal wavelength around 40 and 200 km were identified the first one is attributed to a mw and the second one to an igw

dinoflagellate cyst distribution in surface sediments from the arabian sea northwestern indian ocean in relation to temperature and salinity gradients in the upper water column abstract surface sediment samples from the arabian sea indian ocean have been investigated for their dinoftagellate cyst content to obtain information about the environmental affinity and potential palaeo environmental significance of the cyst species their distribution is compared with the environmental characteristics of the overlying water column using detrended correspondence analysis and canonical correspondence analysis the distribution patterns of individual species are compared with temperature and salinity gradients over four seasons the main variation in cyst association appears to be related to variation in those gradients affected by the sw and ne monsoons on the basis of this relationship four groups of species can be recognised 1 central arabian sea species 2 sw monsoon upwelling species 3 ne monsoon eutrophic species 4 species with no distinct relationship with monsoon related gradients the downcore occurrences of species from groups 1 2 and 3 have potential as indicators for palaeo sw and ne monsoon strength

nitrous oxide in the deep waters of the world s oceans we present a compilation and analysis of n2o data from the deep water zone of the oceans below 2000 m the n2o values show an increasing trend from low concentrations in the north atlantic ocean to high concentrations in the north pacific ocean indicating an accumulation of n2o in deep waters with time we conclude that the observed n2o accumulation is mainly caused by nitrification in the global deep water circulation system i e the conveyor belt hydrothermal and sedimentary n2o fluxes are negligible we estimate the annual n2o deep water production to be 0 3 0 1 tg despite the fact that the deep sea below 2000 m represents about 95 of the total ocean volume it contributes only about 3 16 to the global open ocean n2o production a rough estimate of the oceanic n2o budget suggests that the loss to the atmosphere is not balanced by the deep sea nitrification and pelagic denitrification therefore an additional source of 3 8 tg n2o yr 1 attributed to nitrification in the upper water column 0 2000 m might exist with a simple model we estimated the effect of changes in the north atlantic deep water nadw formation for deep water n2o the upper water n2o budget is not significantly influenced by variations in the n2o deep water formation however the predicted decrease in the nadw formation rate in the near future might lead to an additional source of atmospheric n2o in the range of about 0 02 0 4 tg yr 1 this anthropogenically induced source is small and it will be difficult to detect its signal against the natural variations in the annual growth rates of tropospheric n2o

geophysical investigation of the honningsvag igneous complex scandinavian caledonides the honningsvag igneous complex within the mageroy nappe northern norway has marked magnetic and gravimetric signatures palaeomagnetic studies reveal a siluro devonian scandian dual polarity remanence ne and up sw and down mean declination 045 inclination 38 and a 95 8 4 rock magnetic and petrological studies indicate a pure magnetite host for the remanent magnetization component magnetic fabric ellipsoids delineate dl and d2 scandian structures affecting the area and demonstrate an internal reclined fold structure of the honningsvag igneous complex forward modelling demonstrates that a short wavelength pouitive aeromagnetic anomaly c 700 nt over the northwestern part of the complex is associated with an area of reverse remanent polarity sw and down conversely areas of normal remanence polarity ne and up most common are associated with magnetic lows or quiet zones the gravity field in the vicinity of the complex displays a symmetrical positive anomaly of approximately 200 g u wavelength 15 km this can be attributed to a density contrast of approximately 0 20 mg m 3 between the gabbros of the honningsvag complex 2 93 and surrounding metasediments 2 73 an optimal geophysical and geological model demonstrates that the complex has been tilted through 90 and now has the form of a steeply dipping reclined fold structure extending to a depth of at least 6 km palaeomagnetic remanence acquisition post dates emplacement of the mageroy nappe late dl and probably originated during post dl uplift brittle upper crust d2 deformation which continued into devonian times folded the honningsvag igneous complex and introduced a small but systematic dispersion in the palaeomagnetic remanence directions the magnetization is therefore post dl but pre d2 in age and can be termed syn scandian palaeomagnetic and isotopic evidence suggests a syn tectonic magnetization age of c 410 ma the palaeomagnetic pole n7 and e344 resembles that from the underlying kalak nappe complex it is therefore inferred that the scandian emplacement of the mageroy nappe was synchronous with a thermal event which affected the older and underlying finnmarkian defor med kalak nappe complex

seasonality in the hydrography and biogeochemistry across the pakistan margin of the ne arabian sea abstract a series of cruises were conducted across the pakistan continental shelf edge and upper slope in the ne arabian sea between march and october 2003 coinciding with spring inter monsoon and late to post sw monsoon conditions water column hydrographic profiling together with nutrient chemistry show the upper boundary of the oxygen minimum zone omz rose during the sw monsoon by approximately 80 m leading to an inundation of a substantial area of the continental shelf with low oxygen water while the lower boundary showed only slight movement the core of the omz identified by the presence of a secondary nitrite maximum and high nitrate deficits rose by approximately 200 m nitrite concentrations within the secondary nitrite maximum approximately doubled over the period of study but this was not matched with an increase in the nitrate deficit dissolved oxygen concentrations in the core of the omz showed little or no substantial change during the course of the study hydrographic profiling showed greatest change in water masses around the 200 600 m depth range probably resulting from the northward movement of the west india undercurrent

stratospheric gravity wave simulation over greenland during 24 january 2005 1 the advanced regional prediction system forecast model is extended up to the stratopause and over the entire hemisphere to simulate gravity waves during 24 january 2005 with a 15 km horizontal resolution the simulation produces dominant gravity wave features near eastern greenland that are associated mainly with orographic forcing by the greenland terrain the simulated wave temperature perturbations compare favorably with radiance perturbations from nasa atmospheric infrared sounder observations in the upper stratosphere 40 50 km vertical overturning of the isentropes suggests the occurrence of wave breaking just east of greenland that leads to a tremendous reduction of wave amplitudes the associated flux divergence produces horizontal flow deceleration of 12 120 m s 1 day 1 and coincides with areas of depleted stratospheric wind speed suggesting strong interactions between orographic gravity waves and the polar vortex a simulation using the coarser 50 km horizontal resolution produces gravity waves of significantly weaker amplitudes

shallow stratigraphic drilling applied in hydrocarbon exploration of the nordkapp basin barents sea abstract the nordkapp basin is a late palaeozoic rift basin characterised by numerous salt diapirs the salt was deposited in the late carboniferous early permian and has been remobilised several times upper palaeozoic and mesozoic sediments filled in the basin and were uplifted by salt diapirism in the early middle triassic late jurassic late cretaceous and tertiary regional uplift and erosion in the early tertiary and extensive glacial erosion in the late pliocene pleistocene removed up to 1200 m of the mesozoic and cenozoic strata and left them heavily tilted and truncated around the salt diapirs only covered by a thin sheet of glacial sediments during much of the triassic and jurassic the nordkapp basin was a large marine embayment open to the ocean in the southwest this allowed deposition of potential hydrocarbon source rocks in anoxic basins during transgressive periods in the triassic and late jurassic coastal processes improved the reservoir quality of upper triassic to middle jurassic sands during regressive periods one exploration well within the basin and three wells surrounding the basin have produced oil shows but no commercial discoveries have been made so far during the review period of the present paper an exploration well encountered oil and gas in triassic sandstones in the southwestern segment of the basin this is the first direct indication of a mature oil producing source rock in the nordkapp basin and will be important for future exploration of the basin

vhf radar observations of gravity wave production by cold fronts over southern australia abstract four extended observational campaigns were conducted during august and november 1988 with an st stratosphere troposphere radar in southern australia during the passage of cold fronts over the system giving around 30 days of three dimensional wind measurements with 15 min time and 0 5 km height resolution over the 2 11 5 km height range order of magnitude increases in the variance of time fluctuating wind velocities were measured during frontal passages which are definitively ascribed to gravity waves the time height morphology of the horizontal and vertical velocity fluctuations differed bursts of horizontal velocity variance u 2 2 10 100 m2 s 2 arose at upper levels about a day before the frontal boundary arrived and this activity gradually extended to lower heights as the front neared the arrival of the frontal boundary marked a sudden reduction in this activity after the frontal boundary passed reduced activity persisted for 12 hours after which bursts in u 2 2 returne

a study of the low frequency inertio gravity waves observed during the pyrenees experiment the purpose of this paper is to analyze and interpret the onset of some well characterized transient inertio gravity waves observed during the pyrex pyrenees experiment campaign the data used are the high resolution soundings launched every 6 hours on both sides of the ridge in agreement with other observations made during the field campaign certain among those soundings often show steady mountain waves it appears that those waves are often transients and are followed by well characterized inertio gravity waves propagating upward and downward from the level where the initial mountain waves are large to interpret those observations it is suggested that the observed inertio gravity waves result from the geostrophic adjustment of the large scale flow that follows the transit and eventually the breaking of the main mountain wave this hypothesis is supported by an analytical calculation of inertio gravity waves emission from a momentum deposit that lasts a finite time the spatial extent of this forcing are also finite and its maximum amplitude is a fraction of the measured mountain drag

the early carboniferous mageroy dykes northern norway palaeomagnetism and palaeogeography palaeomagnetic data from the 337 ma mageroy dykes northern norway are of exceptionally high quality and a positive contact test along with an existing regional result from the silurian honningsvag igneous suite attests to a primary early carboniferous magnetic signature the palaeomagnetic pole s 14 8degrees e320 1degrees dp dm 4 4 8 6degrees is the first early carboniferous pole from baltica and implies that northernmost norway greenland the barents sea and svalbard were located at tropical to low northerly latitudes at this time northward drift during carboniferous times 5 6 cm yr as demonstrated from palaeomagnetic data is also reflected in the sedimentary facies in the barents sea realm that is a change from tropical early carboniferous to subtropical 20 30degrees n carbonates and evaporites in the late carboniferous the mageroy dykes are continental tholeiites which intruded into a set of nw se trending normal faults parallel to the trollfjorden komagelva fault zone and the mageroysundet fault immediately to the north and south of mageroya respectively these and many other nw se trending faults onshore and offshore were active during late palaeozoic extension and the dykes were probably contemporaneous with the earliest syn rift sedimentation in the barents sea for example the nordkapp basin less

inertia gravity waves spontaneously generated by jets and fronts part i different baroclinic life cycles abstract the spontaneous generation of inertia gravity waves in idealized life cycles of baroclinic instability is investigated using the weather research and forecasting model two substantially different life cycles of baroclinic instability are obtained by varying the initial zonal jet the wave generation depends strongly on the details of the baroclinic wave s development in the life cycle dominated by cyclonic behavior the most conspicuous gravity waves are excited by the upper level jet and are broadly consistent with previous simulations of o sullivan and dunkerton in the life cycle that is dominated by anticyclonic behavior the most conspicuous gravity waves even in the stratosphere are excited by the surface fronts although the fronts are no stronger than in the cyclonic life cycle the anticyclonic life cycle also reveals waves in the lower stratosphere above the upper level trough of the baroclinic wave these waves have not been previously identified in idealized simulations the sensiti

a statistical study of inertia gravity waves in the troposphere based on the measurements of wuhan atmosphere radio exploration ware radar wuhan atmosphere radio exploration ware radar is the first mesosphere stratosphere troposphere radar to have become operative in the mainland of china and is dedicated to real time atmospheric observations based on the ware radar data collected for the period from september 2011 to february 2013 2666 downward and 1735 upward inertia gravity waves igws are identified from three dimensional 3 d wind fields observed in the troposphere and subsequently analyzed in a statistical manner wave characteristics including intrinsic frequencies vertical wavelengths horizontal wavelengths vertical wave number spectra energy density spectra and wave sources are investigated using a combination of the lomb scargle spectral analysis the quasi monochromatic gravity waves model and the hodograph method our results demonstrate that the characteristic parameters of upward and downward tropospheric igws are not significantly different these results indicate that the tropospheric igws parameters are not directly correlated with propagation directions combining with the information of statistical 3 d wind field and some climatic characteristics of hubei province atmospheric moist convection will contribute most in summer whereas jet front systems will contribute most in winter one may expect seasonal variations to be tied to the varying importance of these sources

a mesoscale gravity wave event observed during ccope iii wave environment and probable source mechanisms abstract synoptic and special mesoscale observations taken during the cooperative convective precipitation experiment ccope are used to describe the multiscale environment of a gravity wave event understand the wave environment interactions that led to the development of severe thunderstorms and asses possible wave generation mechanisms the storms formed sequentially as a packet of gravity waves propagated across a stationary thunderstorm outflow boundary convection developed most rapidly in that part of the mesonetwork in which existed the combination of relatively high parcel buoyant energy weak restraining inversion strong storm downdraft potential and substantial vertical wind shear associated with a mesoscale jet streak synoptic scale analysis reveals that the waves were excited north of a stationary front and within the right exit region of the jet streak as it approached a stationary ridge in the 300 mb height field strong indications of unbalanced flow were diagnosed within the gravit

palaeomagnetic study of the derbyshire lavas and intrusions central england definition of carboniferous apparent polar wander abstract the remanence in extrusive volcanic rocks of lower carboniferous visean age in the pennines of central england has been reinvestigated employing detailed thermal demagnetisation and incorporating new geological knowledge of field relationships indications of primary remanence identified by early studies are supported and four successive reversals in the asbian brigantian succession about 335 ma recognised a mean reversed direction of d i 203 36 10 sites r 9 75 yields a pole position at 336 e 14 s dp dm 6 10 grouping improves slightly when correction is made for mild intra carboniferous folding and widespread uniformity of polarity is recognised within individual units sporadic variscan overprinting increases in importance to the southeast intrusive dolerite bodies yield two contrasting directions of magnetisation in the central part of the derbyshire pericline mixed polarity directions mean d i 211 37 4 sites r 3 92 comparable to the lavas imply a lower carboniferous age of emplacement in the se upper permian directions of reversed polarity mean d i 221 23 define a later intrusive event or comprehensive overprinting the primary lower carboniferous pole positions accord with contemporaneous poles from the midland valley of scotland and demonstrate that carboniferous and younger tectonic movements are palaeomagnetically undetectable at least between these two areas apparent polar wander apw movement is confirmed between lower and upper carboniferous times at about 335 320 ma the lower carboniferous limestones have a remanence entirely younger than depositional ages and are therefore unreliable indicators of carboniferous magnetostratigraphy and tectonics silicified limestones prove to have remanences closer to the primary lower carboniferous field and appear to have been shielded from the effects of later overprinting the apw swathe identified from north american carboniferous rocks coincides in polarity and position with the latter part of the british carboniferous path on the pangaean reconstruction

influences of gravity waves on convectively induced turbulence cit a review thunderstorms are known to produce turbulence such turbulence is commonly referred to as convectively induced turbulence or cit and can be hazardous to aviation although this turbulence can occur both within and outside the convection out of cloud cit is particularly hazardous since it occurs in clear air and cannot be seen by eye or onboard radar furthermore due to its small scale and its ties to the underlying convection it is very difficult to forecast guidelines for out of cloud cit avoidance are available but they are oversimplified and can be misleading in the search for more appropriate and physically based avoidance guidelines considerable research has been conducted in recent years on the nature of the phenomenon and in particular its connection to gravity waves generated by the convection this paper reviews the advances in our understanding of out of cloud cit and its relation to convective gravity waves and provides several detailed examples of observed cases to elucidate some of the underlying dynamics

sources of gravity waves in the lower stratosphere above south pole 1 five year 2001 2005 high resolution radiosonde data were processed to obtain the gravity wave gw variabilities in the lower stratosphere over south pole sp our results show that gw activities in the lowermost section 10 15 km are strongest in may and september and weakest in the austral summer whereas in the altitude range of 15 25 km strongest weakest gw kinetic energy is observed around september january we also explored the relationships of gws to the synoptic scale variations in the troposphere and the ageostrophic motions in the upper troposphere over the antarctic which are expected to be significant mechanisms for gw generation a ray tracing model grograt was used to explore the relationship between gw propagation and the background field in the altitude of 15 25 km the annual cycle of gw activity resembles that of adjustment process below 15 km the annual cycle of gw activity has two peaks in may and september our analysis suggests that these two peaks are due to the variation of topographic gw generation and filtering of background atmosphere due to critical level filtering in the lowermost section topographic gws cannot propagate upward which makes the shape of gw annual cycle at higher altitudes closer to the annual cycle of adjustment processes the analysis suggests that the minimum of gw activity at sp during the austral summer may be due to the combination of weaker wave generation from adjustment processes associated with synoptic scale systems flow over topography and unfavorable background field for gw propagation

water masses in the humboldt current system properties distribution and the nitrate deficit as a chemical water mass tracer for equatorial subsurface water off chile abstract three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern south pacific and their distributions oceanographic data were taken from the scorpio may june 1967 piquero may june 1969 and krill june 1974 cruises vertical sections of temperature salinity dissolved oxygen nitrate nitrite phosphate and silicate were used to analyze the water column structure five water masses were identified in the zone through t s diagrams subantarctic water subtropical water equatorial subsurface water antarctic intermediate water and pacific deep water their proportions in the sea water mixture are calculated using the mixing triangle method vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m several characteristic oceanographic features in the study area were analyzed the shallow salinity minimum displacement towards the equator the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south and the equatorward intermediate antarctic salinity minimum associated with a dissolved oxygen maximum the nitrate deficit generated in the denitrification area off peru and northern chile is proposed as a conservative chemical tracer for the equatorial subsurface waters off the coast of chile south of 25 s

case studies of nonorographic gravity waves over the southern ocean emphasize the role of moisture two case studies of nonorographic gravity waves are carried out for wave events that occurred over the southern ocean in november 2005 mesoscale simulations were carried out with the weather and research forecast model the simulated waves were compared to observations from superpressure balloons of the vorcore campaign and from the high resolution dynamic limb sounder satellite satisfactory agreement is found giving confidence in the estimations of wave parameters and amplitudes for the amplitudes both the model and observations provide a lower bound for different reasons waves are found in the lower stratosphere with horizontal wavelengths of the order of 150 200 km in the horizontal 5 8 km in the vertical corresponding to intrinsic frequencies between 5 and 10 f where f is the coriolis parameter although the tropospheric flow is very different between the two cases there are features which are common and appear significant for the gravity waves these include intense localized updrafts associated with convection in the troposphere and a displaced polar vortex inducing strong winds in the stratosphere above the frontal region relative to theoretical expectations the simulations emphasize the role of moisture intrinsic frequencies are significantly higher than those expected for waves produced by dry spontaneous generation from jets to quantify the contribution of moisture dry simulations were carried out yielding momentum fluxes over oceanic regions that were 2 5 times weaker identification of the generation mechanisms in these complex flows calls for further study and these should include moisture and a realistic stratospheric jet

observation of gravity wave generation and breaking in the lowermost stratosphere measurements with the aberystwyth vhf radar have revealed a striking illustration of gravity wave generation and breaking in the lowermost stratosphere horizontal wind measurements show an inertia gravity wave that was essentially monochromatic and persisted for longer than 5 days with a maximum perturbation amplitude of approximately 10 ms 1 radiosonde measurements show that this wave induced shear instability that led to intense turbulence close to the tropopause the event was associated with a highly curved jet stream over europe suggesting that geostrophic adjustment was a likely source mechanism

stratospheric variability of wave activity and parameters in equatorial coastal and tropical sites during the west african monsoon recent numerical studies in stratospheric dynamics and its variability as well as climate have highlighted the need of more observational analyses to improve simulation of the west african monsoon wam in this paper activity and spectral characteristics of short scale vertical waves wavelengths 4 km are analysed in equatorial coastal and tropical lower stratosphere during the wam a first detailed description of such waves over west africa is derived from high resolution vertical profiles of temperature and horizontal wind obtained during intensive observation period of the african monsoon multidisciplinary analyses amma campaign 2006 monthly variation of wave energy density is revealed to trace the progression of the inter tropical convergence zone itcz over west africa mesoscale inertia gravity waves structures with vertical and horizontal wavelengths of 1 5 2 5 and 400 1100 km respectively and intrinsic frequencies of 1 1 2 2 f or periods 2 days are observed in the tropical ls with intense activity during july and august when the wam is installed over the tropical west africa over equatorial region gravity waves with intrinsic frequencies of 1 4 4 f or periods 5 2 days vertical wavelength of 2 1 km and long horizontal wavelengths of 1300 km are intense during the wam coastal phase from july to october gravity waves with intrinsic frequencies of 1 2 3 8 f or periods 6 days vertical wavelength of 2 1 km and horizontal wavelengths of 1650 km are less intense during the wam sahelian phase of the wam march june unlike potential energy density kinetic energy density is observed to be a good proxy for the activity of short scale vertical waves during the wam because quasi inertial waves are dominant long term wave activity variation from january 2001 to december 2009 highlights strong year to year variation superimposed on convective activity and quasi biennial oscillation like variations especially above tropical stations

nitrogen biogeochemical cycling in the northwestern indian ocean abstract the vertical distribution and fine scale structure of nitrate no 3 nitrite no 2 nitrous oxide n 2 o phosphate po 4 oxygen o 2 and chlorophyll chl were determined in the north western indian ocean nwio along a meridional section 67 e from the equator to the gulf of oman using an autoanalyser for micromolar levels of nutrients and chemiluminescence and gas chromatographic methods for nanomolar levels of no 3 and no 2 and n 2 o respectively three biogeochimically contrasting regimes were investigated 1 the highly oligotrophic nutrient depleted subtropical gyre 2 the nonsoonal upwelling of nutrient rich intermediate waters of the southeastern arabian coast and 3 the denitrifying o 2 depleted zone odz ca 150 1200 m depth in the arabian sea concentrations of no 3 and no 2 were severely depleted in surface oligotrophic waters from the equator average 43 and 3 6 nm respectively to the subtropical gyre 12 15 n average 13 3 and 2 0 nm respectively with similar levels in the more stratified gulf of oman upwelling waters off southern arabia had three orders of magnitude higher no 3 levels and throughout the nwio the calculated no 3 fuelled primary production appeared to be regulated by no 3 concentration existing redfield o 2 no 3 regeneration ratios 9 1 previously derived for the deep indian ocean were confirmed 9 35 within the oxic upper layers of the nwio the no potential temperature relationship broecker 1974 earth and planetary science letters 23 100 107 needed for the derivation of expected no 3 and no 3 deficits within the denitrifying odz were refined using an isopycnal binary mixing model along the 26 6 density layer to take into account the inflowing contribution of no 3 depleted persian gulf water vertically integrated no 3 deficits increased northwards from 0 8 mol no 3 n m 2 at sta 2 04 n up to 6 49 mol no 3 n m 2 at sta 9 at the mouth of the gulf of oman then decreased to 4 10 moles no 3 n m 2 toward sta 11 near the straits of hormuz when averaged for the denitrification area of the arabian sea this corresponds to a deficit of 118 tg no 3 n adopting a recent freon 11 based estimate of water residence time of 10 years olson et al 1993 deep sea research ii 40 673 685 for the o 2 depleted layer we calculate an annual net denitrification flux of 11 9 tg n to the atmosphere or approximately 10 of the global water column denitrification rates supersaturated n 2 o concentrations were found in both surface oxic and upwelling waters up to 246 and peaked at the base of the odz up to 1264 in the northern arabian sea both nitrification in oxic waters and denitrification in hypoxic layers can be invoked as sources of n 2 o the inventory of excess n 2 o amounted to 2 55 1 3 tg n 2 o n corresponding to annual production of 0 26 0 13 tg from denitrification this is comparable to earlier law and owens 1990 nature 346 826 828 estimates of the ventilation flux of n 2 o 0 22 0 39 tg yr 1 from the upwelling region of the arabian sea the decadal response times for circulation deoxygenation denitrification and ventilation of the odz derived n 2 o and co 2 greenhouse gases and their monsoonal coupling implies the arabian sea is a sensitive oceanic recorder of global climate change

improved salt imaging in a basin context by high resolution potential field data nordkapp basin barents sea abstract the seismic imaging of salt diapirs in the nordkapp basin gave rise to considerable problems in defining their shape and volume independent information was added by integrating the interpretation with high resolution gravity and magnetic data we developed a novel iterative workflow separated into sub categories sediments salt structures basement and moho distinctions between the sources of the anomalies from different depths was achieved by utilizing the different decay characteristics of gravity gravity gradiometry and high resolution magnetic anomalies the workflow was applied to the southern part of the nordkapp basin it started with the sedimentary model derived from seismics populated with measured densities and magnetic susceptibilities and a starting model for the base salt the residual after the removal of this model was interpreted in terms of a crustal model including flexural isostatic calculations for the moho with the sedimentary load the residual after the removal of crustal and early sedimentary model was used to tune the salt model as these major and minor modelling steps depend on each other an iterative process was applied to stepwise improve the density and magnetic susceptibility model the first vertical gradient of gravity and the magnetic field were found to give most information about the cap rock of the diapirs the improvement in salt imaging integrated with results from controlled source electromagnetic and magneto telluric modelling is shown for the salt diapir uranus where a well terminated in the salt constrains the minimum of the depth to base salt

late palaeozoic evolution of the north atlantic margin of pangea abstract eleven palaeogeographic maps spanning the earliest carboniferous tournaisian to late permian kazanian have been constructed for the northern north atlantic based on available onshore and offshore data each palaeogeographic map corresponds to an epoch i e 4 17 ma there are no reconstructions of the serpukhovian and tatarian and the kungurian ufimian are treated as one the palaeogeographic reconstructions outline a change in the overall depositional environment of the barents sea north greenland area from huge humid flood plains in the early carboniferous over shallow warm seas in the mid carboniferous to mid permian to cooler and possibly deeper marine environments in the late permian in east greenland non marine conditions occurred during the entire carboniferous and following a prolonged early permian hiatus warm water carbonates were deposited during the late permian the changes reflect large scale shifts in palaeoclimatic and subsidence patterns related to the northward drift of the area and ongoing rifting in the region

the deep crustal structure of the mafic ultramafic seiland igneous province of norway from 3 d gravity modelling and geological implications

observational evidence for asymmetric inertial instability abstract we present a detailed analysis of a mesoscale circulation phenomenon that appeared on satellite images as a group of propagating cloud wavelets these wavelets developed on the anticyclonic side of a strong upper level subtropical jet in a region of negative potential vorticity p during their lifetime the wavelets were located over the north american synoptic sounding network the meteorological conditions surrounding their occurrence are examined we investigate the various physical mechanisms that may have been responsible for generating the observed cloud wavelets in consideration of the time scale of the wavelets and their proximity to the region where p 0 inertial instability appears to be the most likely dynamical mechanism for explaining their existence using hourly satellite images we determined that the wavelets propagated downstream at a phase speed 25 m s 1 slower than the maximum wind speed of the jet with life cycles of 4 5 h horizontal wavelengths of 400 km and periods

numerical modeling of gravity wave generation by deep tropical convection although convective clouds are known to generate internal gravity waves the mechanisms responsible are not well understood the present study seeks to clarify the dynamics of wave generation using a high resolution numerical model of deep convection over the tiwi islands australia the numerical calculations presented explicitly resolve both the mesoscale convective cloud cluster and the gravity waves generated as the convective clouds evolve they excite gravity waves which are prominent features of the model solutions in both the troposphere and stratosphere the source location is variable in time and space but is related to the development of individual convective cells the largest amplitude gravity waves are generated when the cloud tops reach the upper troposphere a new analysis technique is introduced in which the nonlinear terms in the governing equations are taken as the forcing for linear gravity waves the analysis shows that in the present calculation neither the shear nor the diabatic heating are the dominant forcing terms instead the wave source is most easily understood when viewed in a frame of reference moving with the wind at the level of neutral buoyancy whereupon the source may be described as a vertically oriented oscillating convective updraft this description is consistent with the properties of the modeled stratospheric waves

parameterization of strong stratospheric inertia gravity waves forced by poleward breaking rossby waves abstract the link between poleward breaking rossby waves and stratospheric inertia gravity waves is examined with a visual inspection of ertel s potential vorticity maps based on ecmwf analyses it was found that rossby wave breaking events occurred over northern europe in about 40 of the winter days in 1999 2003 the majority of them were breaking poleward downstream a total of 10 field campaigns were performed in the winters of 1999 2002 at kuhlungsborn germany 54 n 12 e they are related to such events and can be considered as representative for poleward breaking rossby waves inertia gravity wave properties are diagnosed from radiosonde observations they appeared to be shallower slower and stronger than the climatological mean for the north german lowlands hence rossby wave breaking events are linked with strong stratospheric inertia gravity wave activity a novel parameterization of inertia gravity wave generation and propagation is proposed the stratospheric inertia gravity wave action i

inertia gravity waves observed by the uk mst radar we present an analysis of eight years data from the uk mst radar at aberystwyth wales to determine the occurrence and properties of long period quasi monochromatic oscillations in the wind vector identified with inertia gravity waves wave perturbations were first isolated by filtering out background wind variation in the vertical then the continuity of the radar measurements was exploited to apply band pass filters in time to select quasi monochromatic oscillations with periods 4 8 hours or 12 24 hours by searching for altitude regions where the wind vector rotates systematically with height and fitting ellipses to such sections the properties of inertia gravity waves can be derived to guard against contamination by short intrinsic period mountain waves cases were discarded when the vertical velocity measured by the radar exceeded 15 cm s 1 results show that waves in the stratosphere are dominated by upward energy propagation clockwise rotation and those in the troposphere by downward propagation consistent with the dominant source for inertia gravity waves being at tropopause level long period waves 12 hours are observed 70 of the time in the lower stratosphere roughly twice as often as the shorter period waves and 10 20 of the time in the troposphere there is a winter maximum in occurrence in the troposphere and for the short period stratospheric waves however the dominant long period waves show little seasonal dependence likewise they show only a weak correlation with jet stream velocity or direction unlike the other categories which are preferentially associated with strong jet streams and propagate along the jet inertia gravity waves observed by the radar have typical amplitudes 1 2 m s 1 and vertical wavelength 2 km the intrinsic wave period estimated for non jet stream conditions is similar for the two band passed series pointing to the importance of doppler shifting in generating the observed oscillations copyright 2007 royal meteorological society

mechanisms forcing abrupt fluctuations of the indian ocean summer monsoon during the last deglaciation abstract a piston core from the somali upwelling area has been studied at high resolution for its dinoflagellate cyst content variations in cyst association are inferred to reflect changes in indian ocean summer monsoon intensity several abrupt fluctuations in monsoon intensity are detected for the interval between 20 and 10 ka bp comparison of these fluctuations with changes in contrast between 30 n and 30 s july insolation and the 18 o grip ice core values suggests that different mechanisms influenced monsoon intensity at different time intervals a general trend in monsoon intensity follows variations in insolation contrast lagging minimum contrast by 7 5 ka and maximum contrast by 4 ka this phase lag difference can be explained by assuming the existence of an ice snow cover over central asia tibet during glacial times between 18 7 and 12 5 ka bp fluctuations in sw monsoon intensity may be forced by variations in the thermohaline ocean circulation a rapid transition towards strong sw monsoons at 12 5 ka bp is possibly the result of variations in atmospheric circulation and melting of the snow ice fields in central asia tibet variations in glacial interglacial boundary conditions related to temperature change at northern latitudes are likely to have influenced sw monsoon intensity between 12 5 and 10 ka bp whereas after 10 ka bp variations in tropical land surface boundary conditions may be the dominant forcing factor 0 1997 elsevier science ltd all rights reserved

an intermediate nepheloid layer associated with high microbial metabolic rates and denitrification in the northwest indian ocean extensive optical physical chemical and biochemical measurements made simultaneously in the northwest indian ocean reveal the occurrence of an intermediate nepheloid layer inl invariably associated with the secondary nitrite maximum maxima in particulate protein and the activity of the respiratory electron transport system ets are also found within the inl since the inl persists long distances from the continental margin with an offshore intensification it may not be related to the transport of material resuspended along the continental margin an apparent correlation of the inl with the previously reported subsurface maximum in bacterial abundance suggests that a local increase in the abundance of bacteria may be responsible for the increased turbidity positive correlations of the beam attenuation anomaly with nitrite and nitrate deficit suggest that most of these bacteria may be denitrifiers the organic carbon demand within the denitrifying layer computed from the observed ets activity appears to be severalfold higher than the sinking carbon fluxes to the denitrifying layer requiring additional modes of supply of the biodegradable organic matter it is proposed that a bacterial maximum could be maintained with efficient utilization of the dissolved organic matter within the denitrifying waters

palaeo ecological significance transport and preservation of organic walled dinoflagellate cysts in the somali basin nw arabian sea to date relatively little information is available about factors influencing organic walled cyst production of tropical dinoflagellates and processes influencing the final burial of cysts in bottom sediments such as transport and preservation to extend this information cyst fluxes were documented for three sediment traps from june 1992 to february 1993 at two sites in the somali basin northwestern arabian sea as well as the cyst association of underlying sediments by comparing cyst associations of contemporaneously collected trap samples at different depths at one site information about transport and processes of decay in the water column was obtained neither transport nor decay appears to have any detectable influence on cyst association during cyst settlement through the water column comparing the trap associations with the underlying sediments indicates that downslope transport appears to have influenced the cyst association on a local scale only species selective decay probably related to the presence of oxygen in bottom sediments has influenced the cyst association most pronouncedly at the most offshore site relating variations in the trap associations with environmental conditions of the overlying surface waters indicates that highest production of both filled and empty cysts occurs during the sw monsoon upwelling based on this correlation three groups of species can be distinguished species with highest fluxes during 1 the first half of the sw monsoon june august bitectatodinium spongium echinidinium granulatum echindinium transparantum echinidnium spp cysts of protoperidinium compressum and cysts of protoperidinium subinerme 2 the transition between the sw monsoon and inter monsoon spiniferites mirabilis and spiniferites spp 3 no particular season all other species cyst associations of all trap samples are dominated by cyst of protoperidinium species cysts with highest fluxes during the sw monsoon form about a third of the associations

the mode of emplacement of the honningsvag intrusive suite mageroya northern norway the honningsvag intrusive suite consists of several layered mafic ultramafic intrusions and a transgressive body of igneous breccia that appears to represent a magma conduit it is emplaced into a silurian flysch type sedimentary sequence that is thermally metamorphosed to spotted slate cordierite andalusite or pyroxene hornfels and agmatitic migmatite folds and flattened reduction spots in the hornfelses suggest that emplacement took place after caledonian deformation and development of a slaty cleavage tectonic rotation subsequent to emplacement has led to exposure of the honningsvag intrusive suite in a natural cross section corresponding to 10 km of crustal depth basaltic magma was initially emplaced as a several kilometre tall pipe that crystallized to form intrusion 1 a second magma chamber was initiated alongside this pipe and subsequently expanded laterally into a sill like magma body as batches of olivine saturated basalt were added a later magma chamber represented by intrusion 4 developed largely within the cumulates forming the upper part of intrusion 2 and appears to have been accompanied by opening of a broad inclined feeder into which blocks and slabs of older cumulates collapsed the resulting igneous breccias of intrusion 3 are chaotic and largely clast dominated in the lower part of the conduit but enclosed slabs are matrix supported and orientated parallel to an originally subhorizontal banding in the feldspathic peridotite matrix in the upper part the core of the breccia body has a troctolite matrix and contains blocks of older breccia suggesting re opening of the conduit either during the crystallization of intrusion 4 or possibly during the development of chambers represented by the younger layered intrusions the cumulates in intrusion 4 subsided sufficiently to invert marginal parts of the layered series before a further magma chamber was initiated in its roof rocks the last major magma chamber opened alongside intrusion 5 and extended upwards as a pipe or broad dyke to the highest structural levels exposed cross cutting relationships show that the honningsvag magma chambers were not active simultaneously but were emplaced sequentially generally at successively higher structural levels olivine tholeiite magma initially pooled in a crustal zone where it had neutral buoyancy subsequent chambers are suggested to have been initiated by emplacement of magma along the density discontinuities that existed above and around crystallized intrusions and their associated hornfelses chambers evolved by fractional crystallization assimilation of country rocks and periodic replenishment the abandonment of magma chambers may have resulted from the expulsion of low density residual melts

late palaeozoic palaeomagnetic and tectonic constraints for amalgamation of pangea supercontinent in the european variscan belt abstract this paper provides a review of the evolution of palaeomagnetic directions and sequence of tectonic events in the european variscan belt during late palaeozoic times these data are correlated with palaeomagnetic records from gondwana and baltica in order to provide a large scale geodynamic framework during the carboniferous to permian the early carboniferous palaeomagnetic records reported mainly from the rhenohercynian and saxothuringian magmatic arcs indicate a 70 anticlockwise rotation while late carboniferous to permian magnetic directions from various rocks of western and central europe are consistent with 120 clockwise rotation of the eastern and central parts of the variscan belt our review of the chronology of tectonic events is based on a robust database of geochronologically constrained deformation metamorphic and magmatic events which allow discretizing the 80 ma long orogenic evolution into five principal events in this scenario the variscan belt can be regarded as a linear sub plate isolated from gondwana and laurussia by the rhenohercynian and palaeotethysian oceans during devonian times this linear composite belt was segmented by transform faults and boundaries in the late devonian to early carboniferous times 360 335 ma during progressive e w closure of rhenohercynian ocean synchronously with collision between saxothuringian and moldanubian blocks subsequent relocation of subduction to the northern boundary palaeotethysian ocean was responsible for n s shortening almost orthogonal to the ancient sub plate n s elongation at around 335 325 ma this deformation resulted in dextral reactivation of transform boundaries associated with anticlockwise rotation of intermittent blocks at the end of this rotation the faults were parallelized to the teysseire tornquist zone the southern margin of baltica while the lozenge shaped blocks of the former variscan sub plate were further shortened during continuous contraction this evolution can fully explain the 70 anticlockwise rotation from cn3 to cn2 palaeomagnetic directions which are regarded as successive carboniferous magnetizations subsequently the variscan belt suffered a giant transtensional event from 325 to 310 ma that was related to the development of extensional syn magmatic core complexes over the whole belt and significant dextral reactivation of earlier nw se trending transform faults this extensional event was associated with important tilts recorded by cp magnetic overprint resulting from a major thermally induced remagnetization during this event new sets of sinistral transfer nne ssw trending faults originated that partly reactivated boundaries of the principal tectonic zones blocks delimited by second order sinistral and first order dextral faults then rotated in a clockwise manner by 80 the whole system subsequently suffered a period of nne ssw shortening that affected the variscan belt namely along the former laurussian and former variscan sub plate contact in the north and in the south where the giant cantabrian orocline developed at around 310 300 ma due to hard collision with gondwana this deformation is associated with the clockwise rotation of laurussia together with the accreted northern sector of the variscan belt and the anticlockwise of gondwana this clockwise 30 rotation is achieved by a1 remagnetizations while the southern part of iberia suffered anticlockwise rotation the final stage of rapid clockwise rotation affecting the northern limb of the iberian arc including corsica and sardinia is attributed to giant n s extension affecting the whole variscan belt at the onset of permo triassic opening of the tethys ocean this complex evolution is regarded as a result of the readjustment of inhomogeneous and thermally and mechanically instable mobile space in between reorganizing the gondwana and laurussia megaplates and the opening of the palaeotethys ocean during the final stages of formation of the pangea supercontinent finally the palaeomagnetically constrained rotations and tectonic evolution of the variscan belt are explained using a pinned model of internal and external rotations of blocks driven by activation of dextral shear zones by n s compression and e w transtension in particular

wave breaking and critical levels for propagating inertio gravity waves in the lower stratosphere this paper analyses and interprets the formation of mixed layers due to propagating inertio gravity waves observed during the fronts and atlantic storm track experiment the data used are high vertical resolution soundings launched from different sites located in the north atlantic sector in agreement with other studies attributing the origin of the inertio gravity waves to the adjustment of the jet stream near fronts the largest waves observed are often located in the vicinity of and above frontal bands the amplitude of these waves is large enough that they give rise to narrow mixed layers by a detailed analysis of the waves characteristics we can distinguish whether such a mixing is favoured by the presence of an inertia critical level where f or results from wave induced convective instability occurring far from critical levels here is the wave intrinsic frequency and f is the coriolis parameter these observations highlight the importance of inertio gravity waves in the vertical exchanges that occur in the stratosphere copyright 2002 royal meteorological society

short term sedimentation patterns in the northern indian ocean abstract the flux of particles from the photic zone was monitored in one open ocean and two shelf stations in the northern indian ocean by means of drifting sediment traps in the intermonsoon period from march to june 1987 samples were collected over daily intervals and analysed for organic carbon nitrogen total phosphorus and silica flux rates of all elements differed by up to a factor of 10 between the oman shelf and the open ocean area mean rates of carbon sedimentation were 13 6 and 1 7 mmol c m 2 day 1 respectively on the pakistan shelf however sedimentation rates were in the same low range as in the open ocean these differences particularly between the two shelf regions were due to the different types of pelagic systems in the respective photic zones the presence of nitrate in surface water of the oman shelf permitted new production which consequently led to enhanced particle export in the open ocean and the pakistan shelf typical tropical recycling systems retained material by intense regeneration of nutrients in the surface layer these differences also were reflected in the composition of the sedimenting particles changes in production respiration equilibria in the photic zone lead to rapid shifts in the carbon silica and carbon nitrogen ratios of trapped material thus short term sedimentation measurements can provide valuable information on structural and functional variations in pelagic productivity

cosmic gps observations of northern hemisphere winter stratospheric gravity waves and comparisons with an atmospheric general circulation model 1 cosmic satellite temperature data are used to derive the 2006 07 winter mean stratospheric northern hemisphere potential energy ep from gravity waves with vertical wavelengths less than 7 km in grid cells of size 10 5 and to study longitudinal and latitudinal variability in cells of size 20 5 7 days large ep at 17 23 km is mostly associated with the sub tropical jet and shows significant longitudinal variability some contribution to total ep from local orographic sources may occur above the canadian rockies scandinavia and northern japan but not above the himalayas due to the background wind conditions many of the waves are likely to have low ground based phase speeds as observed by filtering around the 0 10 m s 1 background zonal wind cosmic results are compared with a t106l60 agcm confirming sub tropical jet related generation upward propagation and low phase speeds of the observed gravity waves

characteristics of inertia gravity waves over the south pacific as revealed by radiosonde observations 1 using horizontal wind and temperature data with fine vertical resolution obtained by radiosondes we investigate the characteristics of parameters and propagation properties of inertia gravity waves in the upper troposphere and lower stratosphere in the subtropics and extratropics over the south pacific where very few observations have so far been done components extracted by a band pass filter having cutoff vertical wavelengths of 0 5 and 5 km are analyzed as gravity waves gravity wave parameters such as intrinsic frequency vertical and horizontal wavelengths and phase and group velocities are estimated by hodograph analysis the statistics on such parameters are presented for both the stratosphere and troposphere for the three latitudinal ranges 17 24 s 25 33 s and 34 48 s the horizontal wavelengths decrease and increases with increasing latitude south the dominant values for the coriolis parameter f divided by are 0 5 in the lower stratosphere and 0 3 in the troposphere with little dependence on latitude the dominant vertical wavelengths for upward propagating waves are longer in the troposphere than in the lower stratosphere the most dominant direction of horizontal propagation is southward with a little bias toward southeastward a case study using ray tracing suggests that the major source of such southeastward waves is located in the upper troposphere notable northward propagation of gravity waves is also found in the subtropical lower stratosphere the source of the gravity waves is considered to be a cutoff cyclone developing in the upper troposphere

a novel chemical method to quantify fish debris in marine sediments burial of fish bones which consist primarily of hydroxyapatite has been recognized as a mechanism to remove reactive phosphorus from the oceans in this study a new method is presented which differentiates p associated with biogenous apatite pfish from other p fractions the method consisting of a sequential chemical extraction with 2 m nh4cl has been successfully tested on standard materials it enables us for the first time to quantify fish debris in sediment records and to assess their importance for the marine phosphorus cycle the nh4cl extraction has been applied to sediment samples from the arabian sea preservation of fish debris is significantly higher in sediments located above 1 200 m water depth than it is for deeper sediments the distribution of pfish contents in surface sediments is predominantly governed by the extent of fish debris regeneration which is related to differences in water depth and sedimentation rates in addition a good correlation between high sedimentary pfish contents and low oxygen bottom water concentrations suggests that the presence of the intense oxygen minimum zone may account for the enhanced preservation of fish debris in continental slope sediments

statistical analysis of inertial gravity wave parameters in the lower stratosphere over northern china to determine the morphology of inertial gravity wave igw activity in the lower stratosphere 18 25 km over northern china and provide observational data constraints for igw parameterization in atmospheric circulation models the seasonal variation and longitudinal distribution of igw parameters were analyzed statistically using 4 years 2010 2013 of radiosonde data from 20 sites distributed throughout northern china 80 2 e 122 3 e the results are as follows 1 the seasonal variation in the monthly mean igw energy strong in winter and weak in summer is consistent with the results for other regions in the northern hemisphere however the energy shows a significant longitudinal increase from west to east in winter and the opposite pattern in summer which has rarely been reported 2 the monthly mean intrinsic frequency exhibits clear seasonal variation large in winter and small in summer the annual average ratio with the coriolis frequency is 2 47 while the degree of polarization exhibits the opposite seasonal variation with an annual average of 0 71 the monthly mean vertical and horizontal wavelengths are 2 5 and 481 3 km in northern china respectively 3 the annual mean magnitude of the intrinsic horizontal group speed 7 0 m s is much larger than that of the vertical group speed 0 08 m s and both have maxima in winter and minima in summer the frequency of occurrence of the westward propagated igw is larger than that of the eastward propagated igw year round and it is isotropic in the north south direction this phenomenon is related to the filtering effect of the tropospheric westerly jet the annual mean fraction of upward propagation is 75 9 with a minimum in winter 4 the momentum flux exhibits a similar temporal and spatial distribution to energy showing preferred propagation in the northwest direction 5 the correlation of the monthly mean total energy of the igw with the westerly jet and the dynamic instability were studied the results suggest that the westerly jet near the tropopause has a strong influence on the igws activity in the lower stratosphere in northern china and the height region of the westerly jet is a possible source region for igws the maxima regions of the occurrence rates of dynamic instability at the upper and lower edges of the westerly jet in winter are also the possible source region for igws

reconstructions of the continents around the north atlantic at about the 60th parallel abstract late carboniferous early tertiary apparent polar wander apw paths 300 40 ma for north america and europe have been tested in various reconstructions these paths demonstrate that the 500 fathom bullard et al fit is excellent from late carboniferous to late triassic times but the continental configuration in northern pangea changed systematically between the late triassic ca 214 ma and the mid jurassic ca 170 ma due to pre drift extension best fit north atlantic reconstructions minimize differences in the late carboniferous early jurassic and late cretaceous tertiary segments of the apw paths but an enigmatic difference exists in the paths for most of the jurassic whereas for the early cretaceous the data from europe are nearly non existent greenland s position is problematic in a bullard et al fit because of a late triassic early jurassic regime of compression 300 km that would be inherently required for the norwegian shelf and the barents sea but which is geologically not defensible we suggest a radically new fit for greenland in between europe and north america in the early mesozoic this fit keeps greenland locked to europe for the late paleozoic early mesozoic and maintains a reconstruction that better complies with the offshore geological history of the norwegian shelf and the barents sea pre drift a24 extension amounted to approximately 450 km on the mid norwegian shelf but with peak extension in the late cretaceous

a geomagnetic polarity timescale for the carboniferous the geomagnetic polarity pattern for the carboniferous is incompletely known but with the best resolved parts in the serpukhovian and bashkirian hence data from both igneous and sedimentary units are also used in an additional polarity bias evaluation in the tournaisian to mid visean interval polarity is mainly derived from palaeopole type palaeomagnetic studies allowing identification of polarity bias chrons seven polarity bias chrons exist in the mississippian mi1nb to mi4nb with an additional 33 conventional magnetochrons and submagnetochrons mi4r to mi9r the moscovian and gzhelian polarity is best resolved in magnetostratigraphic studies from the donets basin and the southern urals dispute about the reliability of these data is ill founded since an assessment of supporting data from palaeopole type studies suggests that these datasets currently provide the best magnetic polarity data through the pennsylvanian polarity bias assessment indicates a normal polarity bias zone in the kasimovian in the pennsylvanian there are 27 conventional magnetochrons and submagnetochrons pe1n to ci1r and one normal polarity bias chron pe8nb the kiaman superchron begins in the mid bashkirian with clear data indicating brief normal polarity submagnetochrons within the superchron the magnetochron timescale is calibrated using 31 u pb zircon dates and a quantitative bayesian based age scaling procedure

wavelet analysis and the governing dynamics of a large amplitude mesoscale gravity wave event along the east coast of the united states detailed diagnostic analyses are performed upon a mesoscale numerical simulation of a well observed gravity wave event that occurred on 4 january 1994 along the east coast of the united states the value of using wavelet analysis to investigate the evolving gravity wave structure and of using potential vorticity pv inversion to study the nature of the flow imbalance in the wave generation region is demonstrated the cross stream lagrangian rossby number the residual in the nonlinear balance equation and the unbalanced geopotential height field obtained from pv inversion are each evaluated for their usefulness in diagnosing the flow imbalance all of these fields showed clear evidence of strong imbalance associated with a middle to upper tropospheric jet streak and tropopause fold upstream of the large amplitude gravity wave several hours before the wave became apparent at the surface analysis indicates that a train of gravity waves was continuously generated by geostrophic adjustment in the exit region of the unbalanced upper level jet streak as it approached the inflection axis in the height field immediately downstream of the maximum imbalance associated with the tropopause fold a split front in the middle troposphere characterized by the advance of the dry conveyor belt above the warm front was overtaken by one of these propagating waves during this merger process a resonant interaction resulted which promoted the rapid amplification and scale contraction of both the incipient wave nonlinear wave development and the split front frontogenesis the gravity wave and front aloft became inseparable following this merger the situation became even more complex within a few hours as the vertical motion enhanced by this front wave interaction acted upon a saturated potentially unstable layer to produce elevated moist convection an analysis of the temporal changes in the vertical profile of wave energy flux suggests that moist convective downdraughts efficiently transported the wave energy from the midlevels downward beneath the warm front surface where the wave became ducted however pure ducting was not sufficient for maintaining and amplifying the waves rather wave cisk conditional instability of the second kind was crucial this complex sequence of nonlinear interactions produced a long lived large amplitude gravity wave that created hazardous winter weather and disrupted society over a broad and highly populated area although gravity waves with similar appearance to this large amplitude wave of depression occasionally have been seen in other strong cyclogenesis cases involving a jet streak ahead of the upper level trough axis it is unknown whether other such events share this same sequence of interactions

occurrence frequency of convective gravity waves during the north american thunderstorm season 1 convective gravity waves are an important driver of the equator to pole circulation in the stratospheric summer hemisphere but their nature is not well known previous studies showing tight relationships between deep convection and convective waves mainly focus on tropical latitudes for midlatitudes most analyses are based on case studies here we present a new multiyear occurrence frequency analysis of convective waves at midlatitudes the study is based on radiance measurements made by the atmospheric infrared sounder airs satellite experiment during the north american thunderstorm season may to august in the years 2003 2008 for this study we optimized an existing algorithm to detect deep convection in airs data to be applicable at midlatitudes we also present a new detection algorithm for gravity waves in airs data based on a variance filter approach for 4 3 m brightness temperatures the new algorithm can detect plane wave perturbations in the altitude range from 20 to 65 km with vertical wavelengths larger than 15 km and horizontal wavelengths from 50 to 1000 km by analyzing spatial and temporal correlations of the individual airs observations it can be shown that more than 95 of the observed gravity waves in a core region over the north american great plains are related to deep convective clouds i e are likely being classified appropriately as convective waves we conclude that the core region is a good location to observe and characterize the properties of convective waves at midlatitudes the statistical analyses presented here are also valuable to validate parameterization schemes for convective gravity waves for completeness it should be mentioned that our analyses cover not only the u s midwest but the north american continent as well as the surrounding ocean regions in general our analysis also reveals interesting details about tropical convection and related gravity wave activity as well as the capability of the airs instrument to observe these

chaotic advection in the stratosphere implications for the dispersal of chemically perturbed air from the polar vortex the lagrangian evolution of material lines within the northern hemisphere winter stratospheric vortex is determined using isentropic winds and diabatic heating rates obtained from the nasa langley research center larc atmospheric circulation model transient subtropical anticyclones lead to deformation of the material lines near the edge of the polar vortex which then rapidly evolve into elongated filaments as material is drawn around the anticyclones the rate of stretching of the material lines is shown to be exponential with typical e folding times of the order of 4 to 8 days these results provide evidence for chaotic advection near the edge of the stratospheric polar vortex which leads to rapid mixing of vortex air with tropical and midlatitude air the characteristic timescales of these mixing processes and the extent to which the mixing penetrates the polar vortex have important implications for the dispersal of chemically perturbed air from the polar vortex throughout the northern hemisphere and attendant ozone depletion

gravity waves generated during frontogenesis abstract gravity waves forced by nonhydrostatic and nongeostrophic processes within a frontal zone are discussed in particular stationary waves immediately above and below the surface front are considered the waves that appear above the front are horizontally stationary with respect to the front but are vertically propagating the vertical wavelength here is given by 2 n since the waves are nearly hydrostatic the horizontal wavelength of the waves above the front is determined by standing waves that set up below the front these waves corrugate the frontal surface and these corrugations in turn determine the horizontal scale of the waves above the front the waves under the front are standing and are trapped between the earth s surface and the frontal zone which due to its conditions of flow reversal and small ri is assumed to be a reflector of gravity waves the horizontal scale of the standing waves is determined by their vertical wavelength and the slope of the frontal surface these waves

southern hemisphere extratropical gravity wave sources and intermittency revealed by a middle atmosphere general circulation model abstractsouthern hemisphere extratropical gravity wave activity is examined using simulations from a free running middle atmosphere general circulation model called kanto that contains no gravity wave parameterizations the total absolute gravity wave momentum flux mf and its intermittency diagnosed by the gini coefficient are examined during january and july the mf and intermittency results calculated from the kanto model agree well with results from satellite limb and superpressure balloon observations the analysis of the kanto model simulations indicates the following results nonorographic gravity waves are generated in kanto in the frontal regions of extratropical depressions and around tropopause level jets regions with lower higher intermittency in the july midstratosphere become more less intermittent by the mesosphere as a result of lower level wave removal the gravity wave intermittency is low and nearly homogeneous throughout the sh middle atmosphere during january this indicates t

chemical oceanography of the persian gulf abstract measurements of basic hydrographic properties nutrient elements alkalinity and total carbon dioxide were made in the persian gulf in february and march 1977 on r v atlantis ii cruise 93 the results show clearly the penetration into the gulf of surface indian ocean water initially of 36 5 salinity which is carried northwards along the iranian coast gradually increasing in salinity to more than 40 the inflowing surface water is high in phosphate 1 0 0 5 moles kg 1 due to upwelling induced by the north east monsoon however nitrate levels are at or below the detection limit and nitrogenous nutrients appear to be limiting the seawater carbonate system is greatly perturbed by the precipitation of large quantities of calcium carbonate the alkalinity salinity relationship shows that the greatest carbonate loss occurs in the shallow waters of the trucial coast where up to 125 moles kg 1 of caco3 have been lost from the water dense saline low specific alkalinity water formed in the shallows appears to migrate down slope to augment the outflowing waters in the deeper part of the gulf the outflow of the tigris euphrates and karun rivers to the north provides an intense but low capacity signal of low salinity high specific alkalinity waters large amounts of co2 are also fixed by photosynthetic processes the classical mediterranean type of circulation is plainly revealed the residence time of water within the persian gulf is approximately 2 5 yr

seasonal variation of gravity wave activity at midlatitudes from 7 years of cosmic gps and rayleigh lidar temperature observations seven year series of gravity wave gw potential energy at midlatitude stratosphere 10 to 50 km is constructed by combining temperature profiles provided by constellation observing system for meteorology ionosphere and climate cosmic gps satellite constellation and rayleigh lidar operating at haute provence observatory in southern france the combined series are used to evaluate the representation of gw in modern era retrospective analysis for research and applications reanalysis the seasonal and zonal variabilities of gw activity are diagnosed using zonal wind and wind divergence provided by era interim reanalysis the spatiotemporal distribution of gw activity is found strongly dependent on the zonal wind variation wind divergence and topography we show that anomalies in the wind divergence can serve as a proxy for locating synoptic scale enhancements of gw the analysis provides evidence for orographic gw excitation and the results are compatible with geostrophic adjustment being an additional source of stratospheric gw the seasonal gw variability can be largely explained by interaction with the mean flow and wave propagation

inertia gravity wave generation by the tropospheric midlatitude jet as given by the fronts and atlantic storm track experiment radio soundings 1 generation of inertia gravity waves by the midlatitude tropospheric jet is studied on the basis of the data obtained from the radio soundings over the north atlantic during the fronts and atlantic storm track experiment campaign a sample of 224 radio soundings is used to analyze the wave activity as a function of the distance to the jet it is shown that radio soundings displaying the most intense gravity wave activity both in the stratosphere and in the troposphere are the ones closest to the jet axis thus the jet region is the dominant source of gravity waves in this region far from orography further examination allows for identification of two specific regions of the flow that are associated with intense gravity wave activity the vicinity of the maximum of the jet velocity and the regions of strong curvature of the jet the detailed case studies we provide suggest that geostrophic adjustment is the dynamical mechanism responsible for the generation of large amplitude inertia gravity waves in the regions of the strong curvature of the wind the generation of waves in the vicinity of the regions where the wind veers in the deep troughs of the geopotential appears to be systematic

geochemical estimates of denitrification in the arabian sea and the bay of bengal during woce high quality world ocean circulation experiment woce data are used in conjunction with an isopycnal mixing model to calculate nitrate deficits due to denitrification in the oxygen minima of both the arabian sea and the bay of bengal basin scale integral denitrification rates are estimated by combining the nitrate deficits with water mass ages computed for the same regions based on the chlorofluorocarbon cfc 11 distributions nitrate deficits exceeding 12 mol kg 1 are observed for the arabian sea during the 1995 southwest monsoon the estimated basin scale nitrate deficit integrated over the oxygen minimum layer is 63 20 tg n and the annual loss rate is 21 7 tg n y 1 the basin scale nitrate deficit is about half other recent inventory estimates with most of the discrepancy in the bottom half of the oxygen minimum below the secondary nitrite maximum no signature of active water column denitrification was observed in the bay of bengal during the 1995 northeast monsoon

comparison of a large scale inertia gravity wave as seen in the ecmwf analyses and from radiosondes 1 the location characteristics and evolution of a large scale inertia gravity wave that occurred in the lower stratosphere over the north of the british isles on february 6 1997 are studied numerous high resolution radiosondes were available at that time and in that region as part of the fastex database they reveal an intense large scale inertia gravity wave igw propagating upwards above the tropopause maps of the divergence of the horizontal wind on isentropic surfaces were obtained from the ecmwf analyses and showed a clear pattern of alternating bands of convergence and divergence at the lower stratospheric heights in the same geographical region and starting at the same time the comparison of the characteristics of this igw in the analyses and in the observations suggests that the ecmwf analyses can be used for qualitative indications regarding the locations most favorable to large scale igw generation and the corresponding orientation of the waves

quasi monochromatic inertia gravity waves in the lower stratosphere from mst radar observations 1 the frequency of occurrence of quasi monochromatic oscillations with periods near the inertial period is examined using hourly mean wind observations from the mst radars at white sands missile range new mexico and vandenberg air force base california spanning 6 years and 4 years respectively power spectral analyses show that the energy levels near the inertial frequency during summer are nearly constant with altitude from about 12 km up to the highest altitude available about 20 km while energy levels at lower frequencies decrease with altitude this decrease leads to a relative enhancement of energy near the inertial frequency during winter the relative enhancement near the inertial frequency is much smaller results from least squares curve fitting used to find the percent of wind variance explained pev by a single wave over data blocks 72 hours long and 2 km deep indicate that a quasi monochromatic oscillation is present when pev 25 during summer in the stratosphere over 50 of the cases have pev 25 the best fit waveform has mean period near 21 hours and vertical wavelength near 3 km the wind vectors exhibit anticyclonic rotation in time and with height consistent with upward propagating gravity waves the mean ratio of the intrinsic to the inertial frequency is about 1 3 in this data set and the associated mean horizontal wavelength of these waves is slightly over 1000 km

remote sensing of surface pressure on mars with the mars express omega spectrometer 2 meteorological maps 1 surface pressure measurements help to achieve a better understanding of the main dynamical phenomena occurring in the atmosphere of a planet the use of the mars express omega visible and near ir imaging spectrometer allows us to tentatively perform an unprecedented remote sensing measurement of martian surface pressure omega reflectances in the co2 absorption band at 2 m are used to retrieve a hydrostatic estimation of surface pressure see companion paper by forget et al 2007 with a precision sufficient to draw maps of this field and thus analyze meteorological events in the martian atmosphere prior to any meteorological analysis omega observations have to pass quality controls on insolation and albedo conditions atmosphere dust opacity and occurrence of water ice clouds and frosts for the selected observations registration shifts with the mola reference are corrected sea level surface pressure reduction is then carried out in order to remove the topographical component of the surface pressure field three main phenomena are observed in the resulting omega surface pressure maps horizontal pressure gradients atmospheric oscillations and pressure perturbations in the vicinity of topographical obstacles the observed pressure oscillations are identified as possible signatures of phenomena such as inertia gravity waves or convective rolls the pressure perturbations detected around the martian hills and craters may be the signatures of complex interactions between an incoming flow and topographical obstacles highly idealized mesoscale simulations using the wrf model enable a preliminary study of these complex interactions but more realistic mesoscale simulations are necessary the maps provide valuable insights for future synoptic and mesoscale modeling which will in turn help in the interpretation of observations

polar stratospheric ice cloud above spitsbergen 1 within the extremely cold and stable polar vortex of winter 2004 2005 a polar stratospheric ice cloud was observed from ny alesund spitsbergen on 26 january 2005 the observation of a cloud with backscatter ratios up to 23 and volume depolarization larger than 50 is unique in our 15 year ground based lidar data record simultaneous balloon borne water vapor measurements indicate the presence of mesoscale ice clouds nearby normally low horizontal wind speeds inside the inner vortex prevent vertical wave propagation however the rare coincidence of different meteorological processes occurring during a poleward breaking rossby wave event caused favorable conditions for the vertical propagation of mountain waves excited by the flow past spitsbergen detailed meteorological analysis shows that the ice particle formation processes on 26 january 2005 were most likely provoked by mesoscale stratospheric temperature anomalies leading to a local reduction in water vapor

regional variation of total microbial biomass in sediments of the deep arabian sea eight different sites from 2300 to 4420 m water depth in the arabian sea were sampled for a biochemical quantification of phospholipid concentrations in the sediments this method serves as a measure of microbial biomass in marine sediments comprising all small sized organisms including bacteria fungi protozoa and metazoa phospholipid concentrations can be converted to carbon units as an estimate of total microbial biomass in the sediments the average phospholipid concentrations in the surface sediments 0 1 cm of the 4 abyssal sites ranged from 7 nmol cm 3 at the southern site sast 10 n 65 e 4425 m to 29 nmol cm 3 at the western site wast 16 n 60 e 4045 m the high values detected at the abyssal station wast exceeded those in the literature for other abyssal sites and were comparable to values from the upper continental slope of the ne atlantic and the arctic at the four continental slope sites in the arabian sea average phospholipid concentrations ranged from 9 to 53 nmol cm 3 with the maximum values at stations a 2314 m and d 3142 m close to the omani coast records of particulate organic carbon flux to the deep sea are available for four of the investigated locations allowing a test of the hypothesis that the standing stock of benthic microorganisms in the deep sea is controlled by substrate availability i e particle sedimentation total microbial biomass in the surface sediments of the arabian sea was positively correlated with sedimentation rates consistent with previous studies of other oceans the use of the measurement of phospholipid concentrations as a proxy for input of particulate organic matter is discussed

the synoptic setting and possible energy sources for mesoscale wave disturbances abstract thirteen case studies of mesoscale wave disturbances characterized by either a singular wave of depression or wave packets with periods of 1 4 h horizontal wavelengths of 50 500 km and surface pressure perturbation amplitudes of 0 2 7 0 mb are reviewed to isolate common synoptic features for these cases and to shed light on possible energy sources for the waves a strong thermal inversion in the lower troposphere north of a frontal boundary and a jet streak propagating toward a ridge axis in the upper troposphere are commonly observed in all the cases in general the area of wave activity is bounded by the jet axis to the west or northwest a surface front to the southeast an inflection axis between the trough and ridge axes to the southwest and the ridge axis to the northeast the conditions specified by lindzen and tung as being necessary to form a wave duct which include the existence of the lower tropospheric inversion seem to be met in many of these cases this suggests that a du

north atlantic sea floor spreading rates implications for the tertiary development of inversion structures of the norwegian greenland sea the tertiary development of the norwegian continental margin was dominated by the opening of the arctic north atlantic ocean the correct identification of magnetic anomalies and their ages and the analysis of spreading rates during the formation of this ocean are important in understanding the development of the region and specifically the history of its passive margins three ocean domains the aegir reykjanes and mohns regions were investigated in an effort to understand the lateral changes in structural development of the passive margin after continental break up spreading rates generally slowed down from 2 cm a 1 after early eocene initiation of sea floor spreading to values around 0 5 cm a 1 in oligocene time an increase in spreading rates to around 1 cm a 1 coincided with the positioning of the iceland hotspot under the north atlantic mid ocean ridge at the same time the european plate changed its absolute plate motion from a north directed drift to a motion more towards the east the location of inversion structures in the voring and faeroes basin rather than in the more basin is related to differences in spreading rates the mohns and the reykjanes ridges produced more ocean floor than the aegir kolbeinsey ridges asymmetric ocean floor formation in the aegir ridge led to differential stress at the base of the lithosphere which probably explains the absence of inversion features in the more basin less mantle drag furthermore upper plate margins such as the voring basin and possibly the faeroe basin have a lower compressional strength than lower plate margins such as the more basin and therefore preferentially developed inversion structures along the transform boundaries separating the domains additional stress probably built up along extension of the transform zones into the extended continental crust this additional stress probably also assisted initiation of the inversion structures in the voring basin and the faeroes area the amplification of the inversion structures in the voring basin and the faeroes basin was subsequently caused by a variety of processes related to sedimentation and uplift erosion

climatically linked oscillations in arabian sea denitrification over the past 1 m y implications for the marine n cycle water column and core top 15n data show that arabian sea denitrification produces large nitrogen isotopic enrichments that are regionally recorded with fidelity in the sediments these results facilitate interpretation of a 1 m y 15n record for ocean drilling program site 722b on the owen ridge in terms of climatically linked oscillations in denitrification at the major orbital periods as at present denitrification was greatest during interglacial periods and apparently was not active during most glacial intervals cross spectral analysis of 15n with foraminiferal 18o global climate sea level index and lithogenic grain size monsoon strength index suggests forcings by changes in hydrography and productivity acting through the extent and intensity of the oxygen minimum zone the data suggest that denitrification may be an internal forcing mechanism for climate change during major glacial interglacial transitions through influence on marine n inventory and atmospheric co2 however compensation or amplification may occur from other sinks sediment denitrification or sources nitrogen fixation