cooperative inversion of magnetotelluric and seismic data on shurab diapirs in central iran using diapirs as liquid or gas storage structures has increased because salt formations are considered to be extremely impermeable and non reactive the process of delineating the diapirs structures ends in lots of challenges due to their geological complexity therefore the integration of different geophysical methods seems to be necessary to cover different physical characteristics of the diapirs shurab diapirs located at the nw of kashan in qom basin of central iran have been considered as candidates for the first natural gas storages in iran a previous 2d seismic survey across the diapir no 4 of shurab could not resolve the diapir structure properly and some ambiguities left unresolved the main goal of this paper is to resolve the structure of diapir no 4 by employing a cooperative inversion of the seismic and magnetotelluric mt data and a comparison with the joint inversion of transverse electric te and transverse magnetic tm modes of the mt data both inversion schemes show the salt and sedimentary sequences of the stratigraphy of the qom basin the sequences of formations from the surface to depth are classified as upper red formation urf qom formation qf and lower red formation lrf the results also show that the salt body has originated from the lrf it is worthwhile to mention that the results from the cooperative inversion provide more details especially on the flanks and overhangs of the diapir no 4 in addition we have come to the conclusion that the right lateral strike slip fault system is the most responsible phenomenon for the development of the diapirs in the survey area and the sen sen fault plays a basic role as an elevator to pushing the salt up the results are in good agreements with the resistivity and density logs of the boreholes moreover the information from the geology the cooperative inversion results on diapir no 4 and the coincidence of the path of the sen sen fault with the outcrops of the diapirs no 1 3 and 4 obviously provide that the tectonic scenario of the existence for diapir no 4 could be appointed to the diapirs no 1 and 3 equally another probable consequence would be the under surface continuation of the salt bodies all along the sen sen fault the verification of which requires regional mt surveys in a regular grid

a linear decomposition of the southern ocean thermohaline structure the thermohaline structure of the southern ocean is deeply influenced by the presence of the antarctic circumpolar current acc where water masses of the world ocean are advected transformed and redistributed to the other basins it remains a challenge to describe and visualize the complex 3d pattern of this circulation and its associated tracer distribution here a simple framework is presented to analyze the southern ocean thermohaline structure a functional principal component analysis pca is applied to temperature and salinity s profiles to determine the main spatial patterns of their variations using the southern ocean state estimate sose this study determines the vertical modes describing the southern ocean thermohaline structure between 5 and 2000 m the first two modes explain 92 of the combined s variance thus providing a surprisingly good approximation of the thermohaline properties in the southern ocean the first mode 72 of total variance accurately describes the north south property gradients the second mode 20 mostly describes salinity at 500 m in the region of antarctic intermediate water formation these two modes present circumpolar patterns that can be closely related with standard frontal definitions by projecting any given hydrographic profile onto the sose based modes it is possible to determine its position relative to the fronts the projection is successfully applied on the hydrographic profiles of the woce sr3 section the southern ocean thermohaline decomposition provides an objective way to define water mass boundaries and their spatial variability and has useful application for comparing model output with observations

physical controls on biogeochemical zonation in the southern ocean the primary control on the n s zonation of the southern ocean is the wind induced transport of the antarctic circumpolar current acc the acc divides the southern ocean into three major zones the subantarctic zone saz north of the acc the acc transport zone and the zone south of the acc saccz the zone of acc transport is most often subdivided into two zones the polar frontal zone pfz and the antarctic zone aaz but it may be appropriate to define more subzones or indeed only one at some longitudes to maintain geostrophic balance isopycnals must slope upwards to the south across the acc thus raising nutrient rich deep water closer to the surface as one goes polewards in addition silicate concentrations increase polewards along isopycnals because of diapycnic mixing with silicate rich bottom water surface silicate concentrations therefore decrease northwards from high levels in the saccz to low levels in the saz within the saz and pfz and even in the northern part of the aaz silicate levels may drop to limiting levels for siliceous phytoplankton production during summer nitrate concentrations also decrease northwards but only become limiting in the subtropical zone north of the saz the second circumpolar control is the changing balance of stratification with temperature dominating near surface stratification in the saz and salinity dominating further south because of fresh water input to the surface from melting ice this results in circumpolar features such as the subsurface 2 c temperature minimum and the subduction of the salinity minimum of antarctic intermediate water which are often but not always associated with frontal jets and large transports the transport of the acc is dynamically constrained into narrow bands the number and latitudinal location of which are controlled by the bathymetry and so vary with longitude thus it is not the fronts that are circumpolar but the total acc transport and scalar properties of the salinity and temperature fields evidence of summer silicate and nitrate uptake in all zones saz pfz and aaz shows that there is productivity despite their high nutrient low chlorophyll status blooms covering large areas say 400 km across in the pfz and aaz are found in the vicinity of submarine plateaux which suggest benthic iron fertilizatio

unraveling middle crust conductive layers in paleozoic orogens through 3d modeling of magnetotelluric data the ossa morena zone case study sw iberian variscides 1 in recent years a number of magnetotelluric mt surveys have been carried out in the southern branch of the iberian variscan massif namely in the ossa morena zone omz and its neighboring areas the south portuguese zone spz and the central iberian zone ciz in order to determine the geoelectrical structure of this transpressive orogen and gain insight into its internal architecture new mt data collected across the omz complete a dense database that covers the whole belt and its boundaries this paper presents an integrative three dimensional model of the available mt data from the apparent resistivities four components impedance phases and geomagnetic transfer functions from 61 stations given the location of the study area near the atlantic ocean coast effect on the data was analyzed as well as the stability of the mesh due to the strong resistivity contrasts a mesh of 80 77 76 cells was finally used with an average cell size of 4 4 km in the horizontal direction and increasing thickness in the vertical direction from 25 m in the shallower layers to 5 km in the deepest ones the most striking feature is in addition to the conductive anomalies associated with the sutures between the spz omz and the omz ciz a conductive layer which spans the whole ossa morena middle to lower crust the top of this conductive layer is interpreted as a major decollement between the granulitic basement and the overlying meta sedimentary pile

a consistent statistical model selection for abrupt glacial climate changes the most pronounced mode of climate variability during the last glacial period are the so called dansgaard oeschger events there is no consensus of the underlying dynamical mechanism of these abrupt climate changes and they are elusive in most simulations of state of the art coupled climate models there has been significant debate over whether the climate system is exhibiting self sustained oscillations with vastly varying periods across these events or rather noise induced jumps in between two quasi stable regimes in previous studies statistical model comparison has been employed to the ngrip ice core record from greenland in order to compare different classes of stochastic dynamical systems representing different dynamical paradigms such model comparison studies typically rely on accurately reproducing the observed records we aim to avoid this due to the large amount of stochasticity and uncertainty both on long and short time scales in the record instead we focus on the most important qualitative features of the data as captured by summary statistics these are computed from the distributions of waiting times in between events and residence times in warm and cold regimes as well as the stationary density and the autocorrelation function we perform bayesian inference and model comparison experiments based solely on these summary statistics via approximate bayesian computation this yields an alternative approach to existing studies that helps to reconcile and synthesize insights from bayesian model comparison and qualitative statistical analysis

mapping 3d salt using the 2d marine magnetotelluric method case study from gemini prospect gulf of mexico the dominant salt body at gemini prospect gulf of mexico has been analyzed by seismic methods revealing a complex 3d salt volume at depths 1 to 5 km beneath the mud line because of the high contrast in electrical conductivity between the salt and surrounding sediments gemini is an attractive target for electromagnetic interrogation using a broadband magnetotelluric mt sensor package developed at the scripps institution of oceanography data in the period band of 1 to 3000 s were collected at 42 sites in a series of profiles over gemini one of which was directly over a linear ridgelike salt feature striking roughly northwest southeast and another orthogonal to it these two profiles reveal that the strongest mt response arises when the electric field is oriented northeast southwest we test the suitability of 2d inversion of these data for recovering the true salt structure by examining inversions of both actual data and synthetic 3d mt responses derived from the seismically inferred salt volume occam inversions of the northeast southwest component result in resistivity images that generally agree with the seismic data whereas inversions of the complementary component yield significantly poorer fidelity disagreement is greatest 1 2 km along the salt sides and base depth errors for top of salt are less than 500 m although thin deep salt 1k m thick at 5 km depth is not well resolved the inversions reveal a resistive basement and a shallow subseabed environment rich in electrical heterogeneity that is weakly if at all suggested by the seismic data a notable exception is a correlation between a previously uninterpreted seismic reflector and the base of a shallow resistivity anomaly whose presence is consistent with gas accumulation near the hydrate stability zone

spreading of red sea overflow waters in the indian ocean as a result of its remarkably high salinity and despite its small volume input remnants of red sea water rsw have been identified in the agulhas current over 6000 km distant of their source this provided the motivation to investigate the long term mean spreading of rsw throughout the indian ocean using a comprehensive set of observations taken from the national oceanographic data center archives and from the world ocean circulation experiment hydrographic program for the indian ocean after emerging from the gulf of aden into the arabian sea rsw spreads predominantly southwestward along the african continental slope as indicated by strongly inclined isohalines across the arabian sea there is some monsoon variability so that during the winter monsoon there is more rsw present in the gulf of aden and an intensification of southward spreading along the western boundary between 12 and 5 n elsewhere the intermediate depth salinity field of the indian ocean appears relatively stationary between 5 and 10 s in the region of the south equatorial current isohalines of the rsw layer become quasi zonal across the width of the indian ocean only dipping southward toward the western boundary west of 50 e south of here there is a strong tongue of rsw spreading southward through the mozambique channel and into the agulhas current these conclusions concur with previous localized investigations of intermediate water properties using a simple mixing model the percentage of rsw throughout the indian ocean was quantified it was found that the flux of salt into the gulf of aden from the red sea is similar to that estimated to cross 32 s in the agulhas current this result implies that all the rsw which is mixed into the interior of the indian ocean may eventually be exported at the western boundary furthermore it implies that rsw is the dominant component of the salt budget for the intermediate layer and that input from the indonesian seas and via diapycnic processes are small

seasonal meandering of the polar front upstream of the kerguelen plateau the location of the antarctic polar front pf is mapped in the southern indian ocean by decomposing the shape of temperature and salinity profiles into vertical modes using a functional principal component analysis we define the pf as the northernmost minimum of temperature at the subsurface andrepresent it as a linear combination of the first three modes this method is applied on an ocean reanalysis data set and on in situ observations revealing a seasonal variability of the pf latitudinal position that is most pronounced between the conrad rise and the kerguelen plateau this shift coincides with variations in the transport across the northern kerguelen plateau we suggest that seasonal changes of the upper stratification may drive the observed variability of the pf with potentially large implications for thepathways and residence time of water masses over the plateau and the phytoplankton bloom extending southeast of the kerguelen islands

descending ion layer property in the gadanki radar observations of 150 km echoes and its implication to the echoing phenomenon 1 gadanki radar observations of the daytime 150 km echoes displaying descending features resembling the descending ion layer behavior are presented the descending pattern is intriguing since it indicates the possible role of density gradient associated with the ion layer in generating the irregularities responsible for 150 km radar echoes not envisioned before unusually strong snr and narrow spectral features of these echoes clearly indicate the role of sharp density gradients in the echoing process given the fact that gadanki is located at magnetically low latitude it is argued that these descending echoing layers are produced by interchange instability on the gradient of daytime descending ion layer formed by meridional wind shear associated with tidal gravity waves quite similar to that observed during nighttime the observations reported here are first of its kind illustrating the role of density gradient layers and are important in furthering our understanding on the puzzling 150 km echoing phenomenon

polyphase deformation of diapiric areas in models and in the eastern prebetics spain fingerlike bodies of evaporite rocks have been observed in many regions affected by multiple tectonic phases such as the atlas the pyrenees or the zagros mountains where they have been interpreted as fault plane diapiric injections or collapse related salt welds in this article we suggest a new interpretation of these structures as squeezed diapirs based on detailed structural and sedimentological field data of the bicorb quesa diapir eastern prebetics and offer five analog models which simulate the polyphase deformation of the eastern prebetics in this area diapirs formed from the oligocene to langhian during an extensional phase related to the opening of the valencia trough these diapirs were later affected by a serravallian contractional phase which inverted the preexisting grabens and created new folds and thrusts the preexisting diapirs were necked and or squeezed forming secondary welds with a fingerlike geometry that isolated the diapir bulbs from their source layer extrusion of diapiric material was also accelerated during this phase but no new diapirs formed finally the area was again affected by an extensional phase during the tortonian which reactivated the normal faults and created a new set of diapirs the new diapirs formed where the overburden was thinner that is at the toe of the major reactivated faults commonly these faults coincide with the bounding faults of the major grabens formed during the first extensional phase and therefore the new diapirs grow close to the location of the squeezed diapirs the models also show that the faults created during the initial extension prevailed as the main focus for deformation during the polyphase history deformation in the overburden and the viscous layer was mainly accommodated along the major grabens formed during the first extensional stage during shortening the initial major grabens deformed as complex anticlines and during the subsequent extensional phase most deformation occurred by the collapse of these anticlines along preexisting faults fault welds and the flank of the squeezed diapirs the source layer is compartmentalized accumulating and withdrawing material in the same locations the initial grabens and horst as a result the source layer is easily depleted beneath the initial horst forming primary welds

the thinness of the ocean in s θ p space and the implications for mean diapycnal advection abstract it is shown that the ocean s hydrography occupies little volume in the three dimensional space defined by salinity temperature pressure s p and the implications of this observation for the mean vertical transport across density surfaces are discussed although ocean data have frequently been analyzed in the two dimensional temperature salinity s diagram where casts of hydrographic data are often locally tight in s space the relatively empty nature of the world ocean in the three dimensional s p space seems not to have received attention the world ocean s data lie close to a single surface in this three dimensional space and it is shown that this explains the known smallness of the ambiguity in defining neutral surfaces the ill defined nature of neutral surfaces means that lateral motion along neutral trajectories leads to mean vertical advection through density surfaces even in the absence of small scale mixing processes the situation in which the ocean s hydrography occupies a

high resolution observations of 150 km echoes at jicamarca high resolution soundings of equatorial upper e region echoes at jicamarca exhibit gravity wave modulated signal intensity distributions and doppler velocities corresponding to vertical plasma drifts a gravity wave wind driven interchange instability is suggested as a possible generation mechanism of the field aligned plasma irregularities responsible for the echoes the echoes may be utilized in gravity wave studies and in zonal electric field measurements by radars with modest sensitivities

coherent heat patterns revealed by unsupervised classification of argo temperature profiles in the north atlantic ocean abstract a quantitative understanding of the integrated ocean heat content depends on our ability to determine how heat is distributed in the ocean and identify the associated coherent patterns this study demonstrates how this can be achieved using unsupervised classification of argo temperature profiles the classification method used is a gaussian mixture model gmm that decomposes the probability density function of a dataset into a weighted sum of gaussian modes it is determined that the north atlantic argo dataset of temperature profiles contains 8 groups of vertically coherent heat patterns or classes each of the temperature profile classes reveals unique and physically coherent heat distributions along the vertical axis a key result of this study is that when mapped in space each of the 8 classes is found to define an oceanic region even if no spatial information was used in the model determination the classification result is independent of the location and time of the argo profiles two classes show cold anomalies throughout the water column with amplitude decreasing with depth they are found to be localized in the subpolar gyre and along the poleward flank of the gulf stream and north atlantic current nac one class has nearly zero anomalies and a large spread throughout the water column it is found mostly along the nac one class has warm anomalies near the surface 50 m and cold ones below 200 m it is found in the tropical equatorial region the remaining four classes have warm anomalies throughout the water column one without depth dependance in the southeastern part of the subtropical gyre the other three with clear maximums at different depths 100 m 400 m and 1000 m these are found along the southern flank of the north equatorial current the western part of the subtropical gyre and over the west european basin these results are robust to both the seasonal variability and to method parameters such as the size of the analyzed domain

rise closure and reactivation of the bicorb quesa evaporite diapir eastern prebetics spain the bicorb quesa diapir belongs to a complex system of evaporite diapirs located in the se iberian peninsula it was emplaced along the axis of a graben system flanked by two syn diapir growth basins filled by miocene sediments the miocene evolution of the diapir may be divided into three major phases an initial extensional phase during which the graben system formed and the diapir rose a second phase during which regional shortening closed the diapir and a third phase characterized by normal faulting during which diapirism was reactivated cutting the previously formed thrusts and folds this evolutionary trend demonstrates that diapirism was initiated and promoted by regional extension during the two extensional phases the diapir grew by reactive active and passive rise sedimentation during the reactive stage was characterized by strong basin subsidence sharp changes in sediment thicknesses and major coarse grained sediment input during the active stage the coeval basin fill sequence displays progressive angular unconformities gravitational deposits and subtle changes in thickness with the sediments unconformably overlying most of the earlier formed faults finally during the passive stage the sediments synchronous with diapir formation include abundant components from the extruding rocks and show gentler changes in thicknesses a progressive decrease in the input of coarse sediments and the deposition of mudstones and or lacustrine carbonates that clearly extend onto the faulted basin margins

atlantic pacific asymmetry in deep water formation while the atlantic ocean is ventilated by high latitude deep water formation and exhibits a pole to pole overturning circulation the pacific ocean does not this asymmetric global overturning pattern has persisted for the past 2 3 million years with evidence for different ventilation modes in the deeper past in the current climate the atlantic pacific asymmetry occurs because the atlantic is more saline enabling deep convection to what extent the salinity contrast between the two basins is dominated by atmospheric processes larger net evaporation over the atlantic or oceanic processes salinity transport into the atlantic remains an outstanding question numerical simulations have provided support for both mechanisms observations of the present climate support a strong role for atmospheric processes as well as some modulation by oceanic processes a major avenue for future work is the quantification of the various processes at play to identify which mechanisms are primary in different climate states

stochastic models of the meridional overturning circulation time scales and patterns of variability the global meridional overturning circulation moc varies over a wide range of space and time scales in response to fluctuating weather perturbations that may be modelled as stochastic forcing th

on the cause of abrupt vegetation collapse in north africa during the holocene climate variability vs vegetation feedback the abrupt desertification over the northern africa in the mid holocene is studied in both a complex and a simple coupled climate vegetation model in contrast to the previous mechanism that relies on strong positive vegetation climate feedback and the resulted multiple equilibria we propose a new mechanism in which the abrupt desertification is caused by low frequency climate variability rather than a positive vegetation climate feedback the implication of this new mechanism to modelling and observation is also discussed

mesozoic diapirism in the pyrenean orogen salt tectonics on a transform plate boundary the mesozoic history of the pyrenean region was dominated by the opening of the north atlantic ocean and the left lateral movement of iberia relative to europe most deformation was tensional or transtensional but this style was interrupted by several short compressional events perhaps related to bends in the transform plate boundary or minor changes in plate movement directions these compressional events were recorded by deformation adjacent to and above salt structures which were the weakest parts of the system and so served as especially sensitive strain barometers the alternation of extension and shortening controlled the location and style of salt structures evaporites were initially deformed during the latest jurassic early cretaceous neocimmerian transpression which formed salt cored anticlines above west northwest east southeast trending basement faults transtension in the aptian albian caused salt domes to pierce to the surface at the intersections of these anticlines with reactivated northwest southeast and northeast southwest trending basement structures transtension was at least locally interrupted by brief periods of transpression at the aptian albian and albian cenomanian boundaries transpression shortened the diapirs causing rotation uplift and erosion of beds near the salt most diapirs were buried during the late cretaceous in some cases postburial hydrothermal circulation dissolved much of the halite causing the diapirs to sag and the basins to form in roof strata finally the entire region was shortened during the late cretaceous tertiary pyrenean orogeny which greatly distorted many of the preexisting geometries

vertical mixing and cabbeling in layered models abstract a consistent scheme for vertical mixing in layered numerical models is derived in this paper the fact that the vertical coordinate density depends on the properties being transported namely salinity and potential temperature renders the inclusion of vertical mixing in layered models a subtle problem the approach the authors have taken is based upon the entrainment into a layer being proportional to the turbulent activity in that layer across each interface there are then two entrainment velocities one upward velocity that is the entrainment of fluid into the layer above the interface and one downward velocity being the entrainment velocity into the layer below the interface this double entrainment accounts for both the diffusive and the advective consequences of turbulent mixing the proposed scheme works without approximation for a nonlinear equation of state and can readily handle the production of density caused by cabbeling several examples are given

marine magnetotellurics for base of salt mapping gulf of mexico field test at the gemini structure a sea floor magnetotelluric mt survey was conducted over the gemini subsalt petroleum prospect in the gulf of mexico gom to demonstrate that the base of salt can be mapped using marine magnetotelluric mmt methods the high contrast in electrical resistivity between the salt and the surrounding sediments provides an excellent target for mmt the gemini salt body located at 28 46 n 88 36 w is a relatively complex shape buried 2 5 km below the sea floor in 1 km deep water its geometry has been previously determined using 3 d seismic prestack depth migration with well log control in order not to confuse limitations in interpretation technique with limitations in data acquisition numerical forward and inverse modeling guided the survey design to locate a profile that would be amenable to 2 d inversion even though the body was clearly 3 d the seismic imaging of the base of salt along the chosen profile is considered good thus providing a good control for testing the mt method in many other ar

lacustrine sedimentation in the diapir controlled miocene bicorb basin eastern spain abstract the miocene bicorb basin is a small elongated basin developed by normal faulting of a thick jurassic cretaceous carbonate succession and subsequent diapirism of upper triassic mudstones and evaporites the basin fill comprises a sequence over 650 m thick formed by two units the lower alluvial unit consists of a complex alternation of conglomerates sandstones mudstones and minor lacustrine limestones the upper unit comprises marginal alluvial and lacustrine deposits in which seven lacustrine facies associations have been distinguished the inner lacustrine deposits comprise mudstones and carbonates with minor evaporitic deposits at the northeast and southwest basin edges alluvial inputs led to the development of delta and fan delta environments where sandstone and conglomerate deposits dominate the latter stages of the lake evolution are represented by an expansive thick limestone sequence which close to the nw fault bounded margin pass laterally to breccias the hierarchical arrangement of the upper unit shows five different orders of sequences the first order sequence defines a major vertical trend of lake expansion whereas three second order sequences are linked to major flooding expansion episodes all these sequences are related to the tectonic evolution of the diapir metre scale third and fourth order sequences and fifth order sequences which consist of finely laminated rhythmite deposits probably record climatically forced processes the diapir graben system evolution and the climatic variations have exerted major controls on the sequential arrangement and evolution of the lacustrine system both factors have also strongly influenced the changes in the gastropod assemblages

the enigmatic ascent of ca sulphate rocks from a deep dense source layer evidences of hydration diapirism in the lesina marina area apulia southern italy in the lesina marina village area the cropping out gypsum rocks that rose up from the deep and thick upper trias burano fm anhydrite layer have been analyzed to investigate the trigger mechanism for their ascent in this regard we focus on the anhydrite to gypsum transformation starting from the deep source layer indeed petrographic observations of the widespread corroded anhydrite crystals embedded in these gypsum rocks revealed unequivocal evidences of the anhydrite to gypsum transformation in addition and referring to gypsum microstructural features indicate that ductile deformation mechanisms initially operated under higher temperature conditions this temperature should be close to 107 c namely the value of the upper temperature limit of stability of gypsum from lesina marina above which it starts to transform and dehydrate as revealed by microthermometry heating dehydration experiments combined with micro raman analyses all these evidences are in favor of the dramatic density decrease and volume increase due to anhydrite to gypsum transformation by hydration in the deep source layer these variations of physical conditions triggered by hydration promoted diapirism of the gypsum mass in other words hydration diapirism as revealed by seismic lines interpretation the diapirism which gave rise to the lesina diapir occurred during plio pleistocene and was genetically related to the lesina graben type structure hydration at depth was favored by the downward circulation of water rich fluids channeled in faults and the gypsum mass used the weakened zone of the southern fault to pierce the overlying mesozoic and tertiary sediments

salt diapirs in the dead sea basin and their relationship to quaternary extensional tectonics abstract regional extension of a brittle overburden and underlying salt causes differential loading that is thought to initiate the rise of reactive diapirs below and through regions of thin overburden we present a modern example of a large salt diapir in the dead sea pull apart basin the lisan diapir which we believe was formed during the quaternary due to basin transtension and subsidence using newly released seismic data that are correlated to several deep wells we determine the size of the diapir to be 13 10 km its maximum depth 7 2 km and its roof 125 m below the surface from seismic stratigraphy we infer that the diapir started rising during the early to middle pleistocene as this section of the basin underwent rapid subsidence and significant extension of the overburden during the middle to late pleistocene the diapir pierced through the extensionally thinned overburden as indicated by rim synclines which attest to rapid salt withdrawal from the surrounding regions slight positive topography above the diapir and shallow folded horizons indicate that it is still rising intermittently the smaller sedom diapir exposed along the western bounding fault of the basin is presently rising and forms a 200 m high ridge its initiation is explained by localized e w extension due monoclinal draping over the edge of a rapidly subsiding basin during the early to middle pleistocene and its continued rise by lateral squeezing due to continued rotation of the amazyahu diagonal fault

thermohaline variability in the upper ocean the main goal of this exploratory study is to determine how the temperature salinity relationship changes with horizontal length scale and depth in the ocean temperature and salinity were measured on a range of scales from 4 m to 1000 km towing a seasoar along isobars and isopycnals in the subtropical gyre of the north pacific during the winter of 1997 the wavelet transform technique is used to compute the horizontal density ratio and thermohaline variability as a function of scale and location measurements along an isobar in the mixed layer show that the horizontal density ratio is 1 at all scales observed that is horizontal temperature and salinity gradients tend to cancel each other in their effect on density thermohaline variability at small scales is intermittent and clusters around large scale thermohaline anomalies below the base of the mixed layer horizontal gradients of temperature are only partially opposed by salinity and the density ratio is close to 2 in the thermocline the distribution of thermohaline variability is uniform along isobars but intermittent and colocated at different scales along isopycnals density compensated variability ubiquitous in the mixed layer is reduced along deeper isopycnals compensation of horizontal temperature and salinity gradients supports recent theoretical ideas that mixing in the winter mixed layer depends on horizontal density gradients

mimoc a global monthly isopycnal upper ocean climatology with mixed layers a monthly isopycnal mixed layer ocean climatology mimoc global from 0 to 1950 dbar is compared with other monthly ocean climatologies all available quality controlled profiles of temperature t and salinity s versus pressure p collected by conductivity temperature depth ctd instruments from the argo program ice tethered profilers and archived in the world ocean database are used mimoc provides maps of mixed layer properties conservative temperature absolute salinity sa and maximum p as well as maps of interior ocean properties sa and p to 1950 dbar on isopycnal surfaces a third product merges the two onto a pressure grid spanning the upper 1950 dbar adding more familiar potential temperature and practical salinity s maps all maps are at monthly 0 5 0 5 resolution spanning from 80 s to 90 n objective mapping routines used and described here incorporate an isobath following component using a fast marching algorithm as well as front sharpening components in both the mixed layer and on interior isopycnals recent data are emphasized in the mapping the goal is to compute a climatology that looks as much as possible like synoptic surveys sampled circa 2007 2011 during all phases of the seasonal cycle minimizing transient eddy and wave signatures mimoc preserves a surface mixed layer minimizes both diapycnal and isopycnal smoothing of s as well as preserves density structure in the vertical pycnoclines and pycnostads and the horizontal fronts and their associated currents it is statically stable and resolves water mass features fronts and currents with a high level of detail and fidelity

equilibrium structure and dynamics of the california current system this paper addresses the structure and dynamical mechanisms of regional and mesoscale physical variability in the subtropical northeast pacific ocean using the regional oceanic modeling system roms the model is configured with a u s west coast domain that spans the california current system ccs with a mesoscale horizontal resolution up to as fine as 3 5 km its mean seasonal forcing is by momentum heat and water fluxes at the surface and adaptive nudging to gyre scale fields at the open water boundaries its equilibrium solutions show realistic mean and seasonal states and vigorous mesoscale eddies fronts and filaments the level of eddy kinetic energy eke in the model is comparable to drifter and altimeter estimates in the solutions with sufficiently fine resolution because the model lacks nonseasonal transient forcing the authors conclude that the dominant mesoscale variability in the ccs is intrinsic rather than transiently forced the primary eddy generation mechanism is the baroclinic instability of upwelling alongshore currents there is progressive movement of meanseasonal currents and eddy energy offshore and downward into the oceanic interior in an annually recurrent cycle the associated offshore eddy heat fluxes provide the principal balance against nearshore cooling by mean ekman transport and upwelling the currents are highly nonuniform along the coast with important influences by capes and ridges in both maintaining mean standing eddies and launching transient filaments and fronts

a reduced gravity isopycnal ocean model hindcasts of el nino abstract a global isopycnal ocean model is presented for the study of interannual to interdecadal variability in the global ocean the model treats the primitive equations on a sphere with a generalized vertical coordinate this coordinate is designed to represent a turbulent well mixed surface layer and nearly isopycnal deeper layers disappearing isopycnics are treated through the quasi isopycnal technique in which the coordinate separates from the isopycnic in order to maintain a minimum layer thickness a reduced gravity treatment is made with the deepest interface at a mean depth of 2300 m coastal topography is represented but the reduced gravity treatment precludes the use of variable bottom depth the model is used for hindcast studies of el nino during the decade from 1982 through 1991 using a combination of climatological wind forcing and wind anomalies derived from various sources in order to carry out the hindcast experiments a technique is developed for constructing a mean climatological

lithosphere dynamics and tectono stratigraphic evolution of the mesozoic betic rifted margin southeastern spain abstract quantitative subsidence analysis demonstrates that mesozoic sediments in the eastern betic cordilleras have been deposited on a thermally subsiding rifted margin the dynamics of rifting are related to regional trans tension in the atlantic realm modelling of this phase of rifting at the southern iberian margin shows that the associated stretching of the lithosphere significantly altered its geometrical and mechanical structure and exerted a major control on subsequent convergence tectonics the mesozoic stretching led to the formation of a ramp at the margin due to strong lateral variations in the effective elastic thickness eet of the lithosphere and the thickness of the crust in a direction perpendicular to the margin the existence of a ramp structure in the late mesozoic at the iberian margin which is also supported by stratigraphic and structural data is important for the style of subsequent deformation of the lithosphere in late cretaceous tertiary times the lateral variations in eet inferred from forward modelling of rifted margin stratigraphy could explain the observed multiple collapse of the betic margin and the partitioning of deformation between the converging units involved in the betic orogeny modelling of depth dependent palaeo rheological profiles of the margin shows that the mechanical properties of the lithosphere after stretching differed distinctly from those before stretching lithospheric deformation in the betic cordilleras during the tertiary orogeny seems therefore to be largely controlled by the previous rifting phase a comparison of the palaeo and present day rheologies in terms of estimates for eet during late cretaceous and present times indicates that the mechanical properties of the lithosphere underlying the betic orogen were also affected by rifting during late oligocene aquitanian times this phase of rifting is coeval with extension in the valencia trough the gulf of lions and the west european rift system which supports a causal relation with regional lithospheric processes the lateral and spatial variations in thermo mechanical properties of the lithosphere underlying the betics therefore reflect the dynamics of lithospheric extension on a larger scale

petrofabric derived seismic properties of a mylonitic quartz simple shear zone implications for seismic reflection profiling the link between petrofabric lpo and seismic properties of an amphibolite facies quartzofeldspathic shear zone is explored using sem ebsd the shear zone lpo develops by a combination of slip systems and dauphine twinning with a maximum parallel to lineation x and c maximum normal to mylonitic foliation xy the lpo are used to predict elastic parameters from which the three dimensional seismic properties of different shear zone regions are derived results suggest that lpo evolution is reflected in the seismic properties but the precise impact is not simple in general the p wave velocity vp minimum is parallel to the a axis maximum the direction of maximum shear wave splitting avs is parallel to mylonitic foliation and the vp maximum and avs minimum are parallel to the c axis maximum the seismic anisotropy predicted is significant and increases from shear zone wall rock to mature mylonite p wave anisotropy ranges from 11 13 fast and slow shear waves anisotropy range from 6 15 and the magnitude of shear wave splitting ranges from 9 16 nevertheless such anisotropy requires a considerable thickness of rock with this lpo before it becomes seismically visible i e 100 s m for local earthquakes 10 s m for controlled source experiments however reflections and mode conversions provide much better resolution particularly across tectonic boundaries the low symmetry and strong anisotropy due to the lpo suggest that multi azimuth wide angle reflection data may be useful in the determination of the deformation characteristics of deep shear zones a number of factors may produce elastic anisotropy in rocks including variations in the spatial distribution of mineral phases layering grain size and shape fabrics grain boundary properties and the presence of oriented pores or fractures e g kern wenk 1985 mainprice et al 2003 in addition because elastic properties vary with respect to direction in single crystals the majority of rock forming minerals are elastically anisotropic e g christensen 1966 thus deformation processes such as dislocation creep which produce strong crystal lattice preferred orientations lpo in anisotropic minerals may also induce bulk elastic anisotropy it is no surprise therefore that petrophysical properties such as seismic velocities are often highly anisotropic in bulk rock aggregates e g babuska cara 1991 understanding of the impact of microstructural variables on elastic anisotropy has been obtained typically from experimental measurements of elastic properties of minerals or theoretical models that incorporate microstructural variables e g burlini kern 1994 wendt et al 2003 experimental studies have focused primarily on the influence of fractures or lpo on the elastic properties of minerals and rocks in particular the seismic properties can be measured via direct laboratory methods at ambient or elevated temperatures and pressures e g kern 1982 although it is often difficult or impossible to obtain the complete three dimensional property orientation distribution from a single experiment however see pros et al 2003 furthermore experimental investigation of seismic properties usually involves rocks in which all microstructural fabric elements contribute effectively masking any lpo component an alternative approach is to calculate the seismic properties of a rock aggregate from individual crystal orientation measurements incorporating the single crystal elastic constants and the lpo for each mineral weighted according to its modal content e g mainprice humbert 1994 the seismic phase velocities and anisotropies then can be calculated in every direction e g mainprice silver 1993 recently the advent of electron backscattered diffraction ebsd in the scanning electron microscope sem has made it possible to measure lpo in statistically viable numbers from different minerals within a rock aggregate whilst maintaining a oneto one relationship with other microstructural elements e g mainprice et al 1993 lloyd 2000 mauler et al 2000 bascou et al 2001 in this contribution the seismic properties of an amphibolite facies mylonitic quartz shear zone are predicted by averaging the single crystal elastic properties according to the sem ebsd derived lpo in order to study the relationship between microstructure petrofabric and seismic properties this approach illustrates the usefulness of integrating geological studies of rock microstructures and particularly petrofabrics with geophysical studies of seismic properties to obtain a fuller understanding of geodynamic processes

unsupervised clustering of southern ocean argo float temperature profiles the southern ocean has complex spatial variability characterized by sharp fronts steeply tilted isopycnals and deep seasonal mixed layers methods of defining southern ocean spatial structures traditionally rely on somewhat ad hoc combinations of physical chemical and dynamic properties as a step towards an alternative approach for describing spatial variability in temperature here we apply an unsupervised classification technique that is gaussian mixture modelling or gmm to southern ocean argo float temperature profiles gmm without using any latitude or longitude information automatically identifies several spatially coherent circumpolar classes influenced by the antarctic circumpolar current in addition gmm identifies classes that bear the imprint of mode intermediate water formation and export large scale gyre circulation and the agulhas current among others because gmm is robust standardized and automated it can potentially be used to identify structures such as fronts in both observational and model datasets possibly making it a useful complement to existing classification techniques

radar observations of daytime 150 km echoes from outside the equatorial electrojet belt over gadanki 1 we present systematic observations of daytime 150 km echoes from gadanki 13 5 n 79 2 e 6 3 dip latitude the echoing region is confined to 142 162 km altitude and show forenoon descent and afternoon ascent displaying a necklace shape quite similar to that of the equatorial 150 km echoes signal to noise ratio velocity and spectral width are as high as 13 db above noise 5 to 35 m s 1 and 2 to15 m s 1 respectively the observed necklace shape is first of its kind from gadanki and the present observations have almost all characteristics of equatorial daytime 150 km echoes the gadanki radar observations hence provide first experimental evidence on the occurrence of daytime 150 km echoes outside the equatorial electrojet belt

dc geoelectric sounding to determine water content in the salt mine asse frg in the course of investigations concerning disposal of radioactive waste dc geoelectric soundings were performed in the salt mine asse in 1982 the survey resulted in the determination of resistivities of various salt formations a comparison of various resistivities obtained in salt formations in the mine shows that it is possible to estimate the content of free water in salt using archie s equation the significant result of this survey is that salt formations in the mine can be divided into two categories according to their resistivities 1 salt with resistivity between 107 and 108 m particularly na2sp and na3 the particularly pure halitic formations are to be found within this resistivity range 2 salt with resistivity between 103 and 105 m na2tl k2 transition salt the salt formations with thin layers of anhydrite and a high content of hygroscopic salts are classified in the paper

applicability of magnetic fabrics in rocks associated with the emplacement of salt structures the bicorb quesa and navarres salt walls prebetics se spain abstract this work assesses the applicability of the analysis of the anisotropy of magnetic susceptibility ams to rocks associated with salt structures magnetic fabrics from 16 sites sampled on upper triassic clays keuper facies interbedded within the salt layers of the bicorb quesa and navarres salt walls prebetic zone se spain are mostly characterized by oblate magnetic ellipsoids with their magnetic foliation parallel to the bedding and magnetic lineation contained in the bedding plane but without a constant relationship with dip direction to evaluate the quality and significance of the low field ams several experiments were carried out to characterize the magnetic mineralogy of representative samples and enable separation of the contributions from paramagnetic and ferromagnetic s l minerals the comparison between the orientation of the observed magnetic lineation and that of the structural elements characterizing the internal geometry of the studied salt structures antiforms minor folds faults and shear zones and flanks indicates that the magnetic fabric is controlled by deformation processes affecting the salt walls during their growth and or evolution samples were also analyzed from sixteen sites from miocene rocks outcropping in several syn diapiric miocene half grabens related to the salt walls studied their magnetic fabric is interpreted to reflect the dominant stretching direction at the syn diapiric half grabens during and or shortly after deposition our results indicate that caution is required in interpreting magnetic lineations related to salt flow mechanics from rocks associated with salt structures

enhanced velocities and a shear in daytime esq over kwajalein and their relationship to 150 km echoes over the dip equator we present the first evidence of enhanced irregularity drift velocities and a velocity shear in the daytime e region at 4 3 n dip latitude these features found in radar measurements from kwajalein during q type sporadic e esq events are interpreted in terms of a polarization electric field that develops in response to the presence of latitudinal gradients in field line integrated conductivity caused by sporadic e layers because the e region over kwajalein connects directly to 150 km altitude over the magnetic dip equator we suggest that a similar polarization process is responsible for the so called 150 km echoes that have been observed routinely by the jicamarca radar

equatorial 150 km irregularities observed at pohnpei first observations of meter scale equatorial 150 km plasma irregularities outside the american longitude sector are reported the observations conducted at pohnpei western pacific with a wind profiling st radar demonstrate the feasibility of making ionospheric electric field measurements with low cost instruments and also reveal a potentially important anisotropy in the angular distribution of 150 km vhf radar echoes

implications of passive salt diapir kinematics for reservoir segmentation by radial and concentric faults abstract reservoirs associated with salt diapirs that are circular or elliptical in plan view can be segmented by radial faults concentric faults both or neither explanations for this variation are offered based on integration of fault kinematics published studies and seismic examples strata around diapirs can be divided into three structural domains with characteristic fault styles 1 roof zone between the present day depositional surface and crest of a buried inactive diapir this zone is characterised by doming radial faults and occasionally conic graben doming is usually caused by differential compaction and increases with depth 2 a steeply dipping sheath of strata surrounds the diapir out to a distance of less than one diapir radius recording near surface diapir growth in poorly lithified sediments these contain early gravity slumps and late concentric extensional faults regional layer bound polygonal fault systems form radial faults within approximately one diapir radius the only significant radial faulting mechanism below the roof zone 3 diapir root zone of strata whose structural architecture records the diapirs initiating mechanism typically rim synclines or graben that detach on the salt source layer concentric faults at radial distances of a kilometre or more have been found only in root zone rim synclines and sheared sheath strata these models and observations can assist seismic interpretation and structural model building in areas of poor geophysical imaging for instance below overhanging salt

characteristics of 150 km echoes linked with solar eclipse and their implications to the echoing phenomenon 1 this paper presents a study based on gadanki radar observations of 150 km echoes made during the solar eclipse of 15 january 2010 that occurred during 1122 1515 ist radar echoes were observed only during 1150 1215 ist and 1344 1356 ist linked with the entry and recovery phases of the eclipse respectively the most striking observation found is the unusual ascending and descending features of the echoing regions observed during these two time periods although these echoes occurred at higher altitudes than those of control days snr and spectral width of these echoes are similar to those of the lower echoing region observed on the control days further doppler velocities suggest the presence of westward electric field unlike those of the control days concurrent ionosonde observations showed ascent and descent of the f1 layer very similar to those observed in the 150 km echoes these observations and related analysis suggest that the observed echoes were due to the combined action of the electron density gradients and the reduced recombination rate linked with the solar eclipse effect these observations are first of its kind and elucidate the role of density gradient and recombination rate in the 150 km echoing process

magnetotelluric characterization of a salt diapir a case study on bicorb quesa diapir prebetic zone se spain abstract the availability of geophysical data to determine the geometry at depth of a salt diapir and its surrounding structure is essential because of the complexity and changing geometry of these structures for this purpose potential field methods are commonly the first steps in subsurface exploration whereas seismic techniques are applied in later stages however the magnetotelluric method mt may fill the gap between the precision and the time that these two methods entail to prove the usefulness of the mt method it has been applied to the bicorb quesa diapir this diapir is composed of evaporitic rocks piercing an overburden of carbonate rocks providing a wide and contrasting range of electrical resistivity values in this situation the mt method may provide a coherent and realistic image of the subsurface the application of the mt method has allowed us to 1 recognize a basement fault with a vertical throw of 1000 m 2 elucidate the shape of the diapir which is asymmetrical with a north wall vertical and south wall dipping southwards and 3 determine that all of the late triassic salt is concentrated in the diapir core supplementary material original curves and the model adjustments are available at http www geolsoc org uk sup18386

the relative roles of diapycnal and isopycnal mixing on subsurface water mass conversion abstract fluid motion in the sea is known to occur predominantly along quasi horizontal neutral surfaces but the very small diapycnal i e across isopycnal velocities often make a significant contribution to the conversation equations of heat salt and tracer by eliminating the diapycnal advection term between the conservation equations for i heat and ii salt an equation is derived for the rate of change lagrangian derivative of potential temperature on a neutral surface which has terms caused by a turbulent mixing along isopycnal surfaces i e isopycnal mixing b diapycnal turbulent mixing and c double diffusive convection bemuse of the nature of the isopycnal reference frame the diapycnal mixing terms do not take their expected forms for example the diapycnal turbulent mixing term is proportional to the diapycnal eddy diffusivity d multiplied by the curvature of the s curve d2s d 2 rather than the usual form d x x if the s curve is locally straight small scale turbulen

the dynamical subtropical front 1 the southern ocean subtropical front stf is thought to play a key role in the global climate system theory suggests that the latitude of the stf regulates the volume of saline agulhas leakage into the atlantic ocean from the indian here we use satellite sea surface temperature sst and sea surface height ssh data to study the physical characteristics of the stf water mass boundary we find that the strong currents in this region do not align with the surface water mass boundary therefore we provide a new climatology for these currents which we define as the dynamical stf dstf the dstf is the eastward extension of the western boundary current in each basin and is characterized by strong sst and ssh gradients and no seasonal cycle at the center of each basin it merges with the sub antarctic front on the eastern side of basins the stf surface water mass boundary coincides with a separate region of multiple sst fronts we call this the subtropical frontal zone stfz the fronts in the stfz have a large seasonal cycle and no ssh signature despite lying close to the same water mass boundary the dstf and stfz are completely unrelated we therefore suggest the term stf only be used when referring to the surface water mass boundary when studying the strong currents on the western side of basins the term dstf is more relevant and similarly the term stfz better describes the region of enhanced sst gradients towards the east

the thermohaline modes of the global ocean abstractthe first 2000 m of the global thermohaline structure of the ocean are statistically decomposed into vertical thermohaline modes using a multivariate functional principal component analysi

geodynamic implications for the formation of the betic rif orogen from magnetotelluric studies 1 magnetotelluric data from the central betics mountains spain have been used to determine the electrical resistivity of the crust after a three dimensional 3d interpretive approach at shallow levels 3 km the most striking and well resolved feature of the model is an upper middle crust conductive body located at the core of the internal betics antiform this approximately 14 km thick body is interpreted as basic or ultrabasic rocks containing a conducting mineral phase its structural location above the sole thrust of the betic orogen and beneath the nevado filabride complex confirms the presence of a major suture zone between this complex and the autochthonous iberian plate this suture may correspond to an ancient oceanic or transitional domain developed between iberia and the alboran domain during the opening of the tethys ocean partially subducted and closed during the development of the betic orogen the possible geodynamic scenarios for the betics have been reconsidered taking into account this new constraint

on the sheet like nature of 150 km f1 radar echoes 1 the so called 150 km or f1 echoes are shown to arise from field aligned irregularities fai that are embedded in a sheet like region using a 49 92 mhz radar on christmas island which has an antenna beam directed toward geographic east at a zenith angle of 29 5 high resolution doppler velocity variations within the radar scattering volume are used to infer that the sheet like region could have both tilt and curvature this finding is used to infer that plasma density n must be enhanced within the sheet like region and that fai could be generated by an interchange instability driven by a vertical electric field or a zonal neutral wind that acts on the horizontal component of the gradient in n how tilted sheet like structures could form in the f1 region is discussed

the influence of basement structure on the evolution of the bicorb quesa diapir eastern betics iberian peninsula contractive thin skinned deformation above a pre existing extensional basement fault on the basis of an analysis of structural surface data in addition to previously available and new magnetotelluric data it was possible to reconstruct the evolution of bicorb quesa diapir this was initiated as a reactive diapir in relation to a basement fault the reactive diapir was rejuvenated by a thin skinned compression during the paleogene and rose during an extensional early middle miocene phase later in the middle miocene the diapir was squeezed and then in the late miocene was extensionally reactivated the current reconstruction allows us to analyse a diapir affected by a thin skinned contractional deformation located on top of a pre existing basement fault our study highlights the role played by the geometric relationship between the propagation direction of the cover deformation and the basement fault

an assessment of orthobaric density in the global ocean abstract orthobaric density has recently been advanced as a new density variable for displaying ocean data and as a coordinate for ocean modeling here the extent to which orthobaric density surfaces are neutral is quantified and it is found that orthobaric density surfaces are less neutral in the world ocean than are potential density surfaces referenced to 2000 dbar another property that is important for a vertical coordinate of a layered model is the quasi material nature of the coordinate and it is shown that orthobaric density surfaces are significantly non quasi material these limitations of orthobaric density arise because of its inability to accurately accommodate differences between water masses at fixed values of pressure and in situ density such as occur between the northern and southern hemisphere portions of the world ocean it is shown that special forms of orthobaric density can be quite accurate if they are formed for an individual ocean basin and used only in that basin while orthobari

an exchange window for the injection of antarctic intermediate water into the south pacific antarctic intermediate water aaiw occupies the intermediate horizon of most of the world oceans formed in the southern ocean it is characterized by a relative salinity minimum with a new denser in situ national oceanographic data center dataset the authors have reanalyzed the export characteristics of aaiw from the southern ocean into the south pacific ocean these new data show that part of the aaiw is exported from the subpolar frontal region by the large scale circulation through an exchange window of 10 width situated east of 90 w in the southeast corner of the pacific basin this suggests the origin of this water to be in the antarctic circumpolar current a set of numerical modeling experiments has been used to reproduce these observed features and to demonstrate that the dynamics of the exchange window is controlled by the basin scale meridional pressure gradient the exchange of aaiw between the southern and pacific oceans must therefore be understood in the context of the large basin scale dynamical balance rather than simply local effects

three dimensional gravity inversion using simulated annealing constraints on the diapiric roots of allochthonous salt structures in the northern continental slope of the gulf of mexico large oil and gas reservoirs are often found beneath sheetlike allochthonous salt structures that are laterally extensive some of these salt structures retain their diapiric feeders or roots beneath them these hidden roots are difficult to image seismically in this study we develop a method to locate and constrain the geometry of such roots through 3 d inverse modeling of the gravity anomalies observed over the salt structures this inversion method utilizes a priori information such as the upper surface topography of the salt which can be delineated by a limited coverage of 2 d seismic data the sediment compaction curve in the region and the continuity of the salt body the inversion computation is based on the simulated annealing sa global optimization algorithm the sa based gravity inversion has some advantages over the approach based on damped least squares inversion it is computationally efficient can solve underdetermined inverse problems can more easily implement complex a priori information and does not introduce smoothing effects in the final density structure model we test this inversion method using synthetic gravity data for a type of salt geometry that is common among the allochthonous salt structures in the gulf of mexico and show that it is highly effective in constraining the diapiric root we also show that carrying out multiple inversion runs helps reduce the uncertainty in the final density model

effective sub zechstein salt imaging using low frequency seismics results of the grundy 2003 experiment across the variscan front in the polish basin abstract the extent of the variscan deformation front is one of the key problems of the regional geology of the central european permian basin system particularly in its polish part conventional reflection seismics usually fails to produce a satisfactory image of the pre permian strata due to the shielding effect of zechstein upper permian evaporites thus we used a novel seismic acquisition technique to study the base of the permian complex and its variscan basement in the grundy 2003 experiment we combined wide angle reflection refraction measurements with the near vertical reflection seismics by the use of the constant geophone array with dense 100 m receiver spacing occupying 50 km long profile 3d design of the experiment covering 50 10 km area helped in eliminating the effect of out of plane propagations and local inhomogeneities an effective integration of traveltime tomography cdp reflection processing and prestack depth migration of wide angle reflections applied to our data allowed us to present the model in which we deduced the contact zone of the variscan overthrust structure variscan front with its molasse filled foredeep the latter might be a gas generation zone which is of a great importance for hydrocarbons prospecting in this area

influence of external forcings on abrupt millennial scale climate changes a statistical modelling study the last glacial period was punctuated by a series of abrupt climate shifts the so called dansgaard oeschger do events the frequency of do events varied in time supposedly because of changes in background climate conditions here the influence of external forcings on do events is investigated with statistical modelling we assume two types of simple stochastic dynamical systems models double well potential type and oscillator type forced by the northern hemisphere summer insolation change and or the global ice volume change the model parameters are estimated by using the maximum likelihood method with the ngrip hbox ca 2 record the stochastic oscillator model with at least the ice volume forcing reproduces well the sample autocorrelation function of the record and the frequency changes of warming transitions in the last glacial period across miss 2 3 and 4 the model performance is improved with the additional insolation forcing the bic scores also suggest that the ice volume forcing is relatively more important than the insolation forcing though the strength of evidence depends on the model assumption finally we simulate the average number of warming transitions in the past four glacial periods assuming the model can be extended beyond the last glacial and compare the result with an iberian margin sea surface temperature sst record martrat et al in science 317 5837 502 507 2007 the simulation result supports the previous observation that abrupt millennial scale climate changes in the penultimate glacial mis 6 are less frequent than in the last glacial miss 2 4 on the other hand it suggests that the number of abrupt millennial scale climate changes in older glacial periods miss 6 8 and 10 might be larger than inferred from the sst record

vertical and lateral mixing processes deduced from the mediterranean water signature in the north atlantic the conservation equations of heat salt and mass are combined in such a way that a simple relation is found between the known volume flux of mediterranean water entering the north atlantic ocean and the effects of lateral and vertical mixing processes the method is a form of inverse method in which the only unknowns are the vertical and lateral diffusivities for each isohaline contour on each neutral density surface the authors develop one equation in two unknowns arguing that other terms that cannot be evaluated are small by considering several such isohaline contours the method becomes overdetermined for each density layer and results are found for both the vertical and lateral diffusivity that vary smoothly in the vertical direction giving some confidence in the method

paleomagnetic and inner diapiric structural constraints on the kinematic evolution of a salt wall the bicorb quesa and northern navarres salt wall segments case prebetic zone se iberia abstract paleomagnetism together with an analysis of the internal structure of the bicorb quesa and northern navarres salt wall segments prebetic zone in se iberia were used to constrain their kinematics and driving mechanisms paleomagnetic data from upper triassic red beds of the selected salt related structures and from the miocene rocks belonging to adjacent syn diapiric half grabens reveal 15 30 counter clockwise vertical axis rotations of the salt wall rocks and a 20 clockwise rotation of the jurassic miocene cover block located south of the salt wall this together with the salt wall structure indicates that the origin of the salt wall was linked to the motion of a late miocene thin skinned extensional fault system which detached on the upper triassic evaporites specifically the salt wall formed by the south southwest displacement with a 20 clockwise rotation component of a cover block bounded northwards by the detachment disruptions generated by the motion of pre existent basement faults the upper triassic detachment level was first affected by a counter clockwise vertical axis rotation and during the paleogene earliest miocene building of the iberian chain by tight wnw trending folds and sse directed minor thrusts this study also shows that paleomagnetism together with the analysis of the internal structure can successfully depict the geometry and kinematic evolution of complex salt wall structures

water mass analysis with three conservative variables with one conservative tracer in addition to salinity and potential temperature it is possible to determine the relative strengths of lateral and vertical mixing processes this is achieved by first eliminating vertical advection through neutral surfaces and then forming a linear combination of the three conservative tracers so that the epineutral gradient i e the lateral gradient along the neutral surface of the new variable is zero thereby eliminating lateral advection the resulting expression for the ratio of the vertical and lateral diffusivities involves the curvatures of property property diagrams formed both from vertical casts and from data measured on a neutral surface the method requires that the epineutral gradients of potential temperature salinity and the third conservative tracer are parallel this condition is often met in the common situation where water parcels are the result of mixing between just two parent water masses

heaving modes in the world oceans part of climate changes on decadal time scales can be interpreted as the result of adiabatic motions associated with the adjustment of wind driven circulation i e the heaving of the isopycnal surfaces heat content changes in the ocean including hiatus of global surface temperature and other phenomena can be interpreted in terms of heaving associated with adjustment of wind driven circulation induced by decadal variability of wind a simple reduced gravity model is used to examine the consequence of adiabatic adjustment of the wind driven circulation decadal changes in wind stress forcing can induce three dimensional redistribution of warm water in the upper ocean in particular wind stress change can generate baroclinic modes of heat content anomaly in the vertical direction in fact changes in stratification observed in the ocean may be induced by wind stress change at local or in the remote parts of the world oceans intensification of the equatorial easterly can induce cooling in the upper layer and warming in the subsurface layer the combination of this kind of heat content anomaly with the general trend of warming of the whole water column under the increasing greenhouse effect may offer an explanation for the hiatus of global surface temperature and the accelerating subsurface warming over the past 10 15 years furthermore the meridional transport of warm water in the upper ocean can lead to sizeable transient meridional overturning circulation poleward heat flux and vertical heat flux thus heaving plays a key role in the oceanic circulation and climate

solar flare effects on 150 km echoes observed over jicamarca waccm x simulations submitted manuscript accepted for publication in geophysical research letters https doi org 10 1029 2019gl084790 copyright 2019 american geophysical union further reproduction or electronic distribution is not permitted

an eddy permitting southern ocean state estimate abstract an eddy permitting general circulation model of the southern ocean is fit by constrained least squares to a large observational dataset during 2005 06 data used include argo float profiles ctd synoptic sections southern elephant seals as oceanographic samplers seaos instrument mounted seal profiles xbts altimetric observations envisat geosat jason 1 and ocean topography experiment topex poseidon and infrared and microwave radiometer observed sea surface temperature an adjoint model is used to determine descent directions in minimizing a misfit function each of whose elements has been weighted by an estimate of the observational plus model error the model is brought into near agreement with the data by adjusting its control vector here consisting of initial and meteorological boundary conditions although total consistency has not yet been achieved the existing solution is in good agreement with the great majority of the 2005 and 2006 southern ocean observations and better repr