southern hemisphere circulation and relations with sea ice and sea surface temperature abstract relationships on the seasonal timescale between southern hemisphere 500 hpa height sea surface temperature and antarctic sea ice variability have been investigated using ncep ncar reanalyses ncep sea surface temperatures and met office sea surface temperature and sea ice data the dominant region of interannual variability in the southern hemisphere circulation over the southeast pacific ocean is found to be related to enso variability in tropical pacific sea temperatures as shown in a number of earlier papers it is also related to antarctic sea ice variability where an out of phase relationship is found between sea ice extent in the central pacific and in the southwest atlantic ocean sea ice extent is enhanced in one region when the atmospheric flow anomaly is equatorward presumably through a combination of anomalous heat flux and direct advection at the same time the atmospheric flow anomaly in the other region tends to be poleward resulting in a poleward retreat in the sea ice ed

a possible enso signal in the ross sea an examination of the observational record in the ross sea over the period 1982 1994 indicates that there is a statistically significant relationship between the ross sea sea surface temperature sst and the enso signal in the tropical pacific during this period the ross sea ssts lag the enso signal by 2 4 months with the highest correlation coefficient occurring with a lag of 3 months observations of the sea ice concentration during 1982 1994 also indicate a relation between the sea ice concentration in the ross sea and the enso cycle with reduced sea ice concentrations in el nino years

syn rift evolution of the pripyat trough constraints from structural and stratigraphic modelling the pripyat trough is a late devonian rift basin it forms part of the larger pripyat dniepr donets rift system which has a length in excess of 800 km and separates the ukrainian shield from the voronezh massif the pripyat trough contains a well resolved stratigraphic sub division within the syn rift basin fill sequence which allows the duration and rate of rifting to be determined using 2 d forward and reverse structural and stratigraphic modelling the analysis shows that rifting was extremely rapid sequential decompaction and flattening of 2 d cross sections has been applied to six syn rift time horizons between top upper devonian 364 ma and top middle devonian 377 ma and used to quantify the syn rift development of basin cross sectional area in time the evolution of basin cross sectional area shows that some initial rifting had occurred prior to the middle frasnian 369 ma however most rifting occurred in the famennian 367 364 ma forward syn rift modelling using the flexural cantilever model of rift basin formation has also been applied to quantify the magnitude of extension within the pripyat trough in time forward syn rift models are constrained by the intra syn rift flattened and decompacted cross sections and the observed evolution of the cross sectional area most rapid rift basin formation is shown to have occurred in the famennian with over 66 of basin cross sectional area forming in less than 5 myr and with approximately 80 or more of total extension occurring in less than 3 myr this period of most rapid extension during the famennian coincides with the most active period of volcanicity total devonian extension across the pripyat trough is estimated to be of the order of 11 14 km with a maximum stretching factor of approximately 1 12 extensional strain rates are estimated to be of the order of 0 8 10 15 s 1

stratigraphy and sequence stratigraphy of the moscovian in the donets basin new results are presented on the stratigraphy based on fusulinids and palynomorphs and the sequence stratigraphy of the moscovian in the donets basin they have been developed by comparison of our observations on cross sections near artemovsk and the published coal mine logs of artemovsk geological survey the moscovian of the donets basin is equivalent to the uppermost westphalian b and the westphalian c and d of western europe in the donets basin the moscovian forms a second order sequence as in the moscow basin that can be subdivided into four third order sequences subdivided into fourth order sequences the upper bashkirian shows two fourth order sequences the vereian exhibits two fourth order sequences the kashirian shows four fourth order sequences the podolskian offers eight fourth order sequences the myatchkovian presents four fourth order sequences these sequences begin with an erosive base and show a succession of elementary sequences with fluvial sandstone coal seam limestone and deltaic facies the fluvial sandstone corresponds with an aggradation period the coal and the limestone with a transgressive period and the deltaic facies with a progradation period a decrease of the sandstone thickness and an increase of the marine deposits that are transgressive and regressive upwards are observed from the base to the top of sequences these fourth order sequences present a higher spatial amplitude than the third order sequence and obscure these sequences the second order sequence equivalent to the moscovian shows a lowstand system tract with more fluvial sandstone in the lower part of the vereian a transgressive system tract in the upper part of the vereian tsinskaya and kashirian a maximum flooding period during the podolskian and lower part of the myatchkovian with more marine facies and a highstand system tract in the upper part of the myatchkovian with more lagoonal and swampy palaeoenvironments the sequences are controlled by the regional tectonic subsidence in the graben and the uplift of the horsts and or by eustasy with either a plate tectonic or a glacial origin other investigations particularly radiometric dating will be useful for solving this problem

relationships between the interannual variability of antarctic sea ice and the southern oscillation abstract a climatology of antarctic sea ice extent based on 20 years of data 1973 1992 is presented including measures of interannual variability and extrema in the first half of the year the greatest variability is found in the western hemisphere particularly in the weddell and ross sea regions while in the second semester the variability displays a considerable degree of zonal symmetry we have used this dataset to explore the possible links between antarctic sea ice extent and the southern oscillation index soi to do this we have calculated their correlation for all pairings of calendar months as well as with the soi taken from the year before and subsequent to that of the time of the sea ice data most of the correlations assume their largest magnitude when the soi leads the anomalies in the sea ice but these differ considerably between the three ocean basins the extent of indian ocean sea ice in the months april through july is positively correlated with the soi during most of the previou

tectonic variation in the dniepr donets basin from automated modelling of backstripped subsidence curves abstract the multiphase rift evolution of the dniepr donets dd basin is analysed by 1d backstripping and tectonic modelling of 66 stratigraphic sections mostly from well data distributed throughout the basin the backstripping results illustrate strong temporal and lateral variations in tectonic subsidence it is minor during an inceptive pre rift phase givetian early frasnian 380 8 370 ma and does not show clear spatial correlations within the dd basin framework the main rift phase frasnian famennian 370 362 5 ma corresponds to an acceleration in subsidence rates with tectonic subsidence up to 1500 m along the basin axis displaying a slight increase from the northwest to the southeast strong lateral variations perpendicular to the basin axis reflect the effects of major basin border faults a rift phase in the visean 345 340 ma is characterised by relatively minor subsidence up to about 500 m except for some wells in the southeast following a stage of extremely low rates of deposition in the earliest carboniferous the end of this rift phase can be taken to mark the onset of convex subsidence patterns in the later carboniferous and permian typical in shape of post rift thermal subsidence but significantly increasing in magnitude from northwest to southeast in the basin this trend shows no one to one relationship with late devonian syn rift subsidence the tectonic subsidence curves have been modelled using lithospheric stretching assumptions allowing different stretching factors for the crustal and sub crustal lithosphere and the incorporation of finite and multiple stretching phases a numerical technique was developed that automatically finds best fit stretching parameters for part or all of the tectonic subsidence data given the specification of onset and duration of the various rifting events maps of the 1d modelling results display intrabasinal variations in terms of timing and magnitude of rifting the results indicate that the observed spatial and temporal variations of tectonic subsidence in the dd basin specifically the increasing ratio of carboniferous to late devonian subsidence from northwest to southeast cannot be explained by either a uniform or depth dependent stretching model adopting only a single frasnian famennian rift phase a two phase model in which a significant part of carboniferous tectonic subsidence is related to visean rift activity strongly dominated by sub crustal lithospheric attenuation provides a satisfactory fit to the data although the tectonic implications of such a model are not easily reconcilable by independent constraints a semi quantitative investigation of the possible role of withdrawal of underlying devonian salt during the carboniferous to produce additional post devonian rift phase sediment accommodation space suggests that the effects of such a mechanism could be significant but that they are unlikely to preclude the necessity of the visean rifting event to explain the carboniferous basin evolution

role of crustal stretching on subsidence of the continental crust abstract the principal areas of subsidence of the continental crust are wide intracontinental basins and passive continental margins in many intracontinental basins crustal extension amounts to only a few percent and is unable to explain their subsidence as shown for the timan pechora pre caspian and west texas basins the deep black sea and south caspian basins are underlain by highly attenuated continental crust having velocities in the 7 km s range that shows no evidence for significant extension in passive margins upper crustal extension ranges between 10 and 40 whereas the lower crust is attenuated by 2 3 times e g campos basin north biscay margin large discrepancy between upper crustal stretching and lower crustal attenuation is seen in the crustal configuration of many intracontinental grabens e g baikal and dniepr prypyat basins only in highly extended areas such as the basin and range province and the east china rift system does crustal stretching account for the observed crustal thinning the observed discrepancy between upper extension and crustal thinning across intracontinental rifts and passive margins and particularly in some wide intracontinental basins suggests that crustal stretching alone cannot account for the subsidence of these basins phase transformations in the lower crust probably facilitated by the presence of hydrous fluids can cause rapid 1 ma as well as long term 200 1500 ma upward displacement of the moho discontinuity resulting in high amplitude subsidence of the crust in areas of crustal extension this mechanism can overprint subsidence induced by thermal relaxation of the lithosphere the case of the black sea and south caspian basins shows that density increase of the lithosphere can also occur independently of crustal stretching

shale gas shale oil potential of upper visean black shales in the dniepr donets basin ukraine abstract upper visean rudov beds v 23 are considered as one of the main source rocks within the northwestern dniepr donets basin ddb average toc values within the srebnen bay northwestern ddb exceed 4 thickness up to 100 m average toc contents north and northwest of the srebnen bay up to 60 m are significantly lower 2 4 but still sufficient for unconventional hydrocarbon production whereas wells along the northeastern basin margin do not hold a shale oil gas potential 5 5 km although hydrogen index hi values of the most immature samples are 300 mghc gtoc basinal rudov beds host a potential to generate paraffinic naphthenic aromatic p n a low wax oil according to pyrolysis experiments a basinward maturity trend is visible but the maturity cut offs for shale oil gas production 0 8 rr 1 2 rr are reached at great depths 4 5 km 5 5 km only furthermore results of kinetic experiments do not argue for presence of type iis kerogen potentially triggering earlier hydrocarbon generation the mineralogy of rudov beds varies strongly in lateral and vertical directions limiting the predictability of mechanical behaviour samples from the siliceous basinal facies partly contain more than 60 of brittle minerals quartz feldspar carbonates etc suggesting a good fraccability this value is rarely reached by samples from the transitional and lagoonal calcareous and clayey facies the clay mineral fraction within many investigated rudov samples is dominated by kaolinite which is suggested to diminish the fraccability of shales apart from that expandable clay minerals ecm are present in samples from more than 5 km depth a result of low mesozoic heat flow

evolution of the lower saxony basin abstract the lower saxony basin is a 300 km long and 65 km wide late jurassic and early cretaceous trough which parallels the northern margin of the rhenish massif this basin became inverted during the senonian and paleocene the lower saxony basin is the most important oil province of germany past production amounts to 200 10 6 t of oil 1 5 10 9 bbl the lower saxony basin is superimposed on the late carboniferous variscan foredeep basin and the frontal structures of the variscan fold belt during the permian to middle jurassic the area formed part of the northwest european basin differential subsidence of the lower saxony basin was initiated during the late jurassic and persisted till albian time this involved reactivation of permo carboniferous fracture systems by divergent wrenching a major aptian deep seated laccolith is evident in the western part of the lower saxony basin during the senonian and paleocene sinistral convergent wrenching induced uplift of the basin floor and folding of its sedimentary fill the margins of the inverted lower saxony basin are thrust over the adjacent stable platform areas the differential subsidence of the lower saxony basin can be related to a period of major crustal extension in the north sea rift basin inversion coincides with important orogenic events in the alpine system and is thought to have been induced by intra plate compressional stresses

antarctic circumpolar waves an indication of ocean atmosphere coupling in the extratropics recent observational studies have detected coherent oceanic and atmospheric antarctic circumpolar waves acws which propagate eastward at speeds of 6 8 cm s 1 with a circumpolar wavenumber of 2 analysis of global wind data suggests that the acws are not remotely forced by tropical el nino activity through atmospheric teleconnection rather a coupled instability of the antarctic circumpolar current and its overlying atmospheric motion is proposed to be responsible for the generation of the acws the phase relationship among the observed oceanic and atmospheric variables supports the coupled instability theory this study provides one clear example that extratropical ocean atmosphere dynamical coupling is essential in generating climate variations on time scales of several years and longer

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

geodynamics of rifting and implications for hydrocarbon habitat abstract rifting activity is probably mainly governed by frictional forces exerted on the base of the lithosphere by the convecting sub lithospheric upper mantle combined with deviatoric tensional stresses developing over upwelling branches of the asthenospheric convection system and by far filed stresses controlling the interaction of lithospheric plates moving relative to each other mantle plumes rising from the deep mantle do not appear to be a major driving force of rifting therefore it is questioned whether a distinction between active and passive rifts is still justified lithospheric extension triggers by decompression partial melting of the lower lithosphere and upper asthenosphere magmatic processes contribute materially to thinning of the subcrustal lithosphere and probably also of the lower crust this could explain the frequently observed discrepancy between upper crustal extension by faulting and lower crustal attenuation as defined by refraction and deep reflection seismic data the duration of the rifting stage of palaeorifts and passive margins is highly variable depending on plate interaction crustal separation can be achieved after as little as 7 ma and as much as 280 ma of rifting activity the availability of crustal discontinuities does not appear to play a significant role in the time required for crustal separation to be achieved the structural style of rifts is controlled by the physical state of the lithosphere the mode and amount of its extension and the lithological composition of pre and syn rift sediments subsidence of rift basins is controlled by the balance between isostatic adjustment of the crust to lithospheric stretching and uplift induced by mechanical and thermal attenuation of the subcrustal lithosphere post rift basin subsidence is mainly governed by the decay of rift induced thermal anomalies densification of the lower crust and intra plate stresses provide overprinting effects in view of this it is unlikely that quantitative analyses of post rift basin subsidence give a direct measure of lithospheric extension tectonically active rifts palaeorifts and passive margin basins contain major hydrocarbon provinces their hydrocarbon charge can rely exclusively on pre rift syn rift or post rift sedimentary sequences or a combination thereof maturation of source rocks can be achieved during the syn and or post rift stage of basin evolution during rifting conductive and convective heat transfer accounts for elevated geothermal gradients these play an important role in the maturation of pre and syn rift source rocks thermal gradients decrease asymptotically during the post rift stage

predicting methane accumulations generated from humic carboniferous coals in the donbas fold belt ukraine the numerical modeling of the ukrainian part of the donbas fold belt indicates that the coalification pattern was controlled mainly by the maximum burial depth of coal seams and the heat flow hf 40 75 mw m2 during the permian the coalification pattern was overprinted by magmatic events during the late permian in the south syncline 150 mw m2 and during the permian triassic in the north of the krasnoarmeisk region 120 mw m2 the coalification pattern shows a strong increase in vitrinite reflectance values toward the east and southeastern parts of the study area likely caused by 1 an eastward increase in burial depth 2 a probable eastward increase in hf and 3 probable magmatic activity an increase in total erosion toward the eastern and southeastern parts was also observed with a maximum erosional amount of approximately 8 km 5 mi in the southeastern part of the study area the basin modeling of this area predicts that the main phase of hydrocarbon generation occurred during the carboniferous early permian subsidence the magmatic events that occurred during the permian triassic caused renewed pulses of hydrocarbon generation a large amount of the generated hydrocarbons was lost to the surface because of a lack of seals however the numerical simulation predicts accumulations of about 2 tcf 57 billion m3 of methane generated from carboniferous coals in the south and main synclines where lower permian seal rocks are preserved finally this study provides data on methane resources along the northern flank of the basin which remains a significant frontier for natural gas exploration

oil gas source rock correlations in the dniepr donets basin ukraine new insights into the petroleum system abstract the dniepr donets basin ddb hosts a multi source petroleum system with more than 200 oil and gas fields mainly in carboniferous clastic rocks main aim of the present study was to correlate accumulated hydrocarbons with the most important source rocks and to verify their potential to generate oil and gas therefore molecular and isotopic composition as well as biomarker data obtained from 12 oil and condensate samples and 48 source rock extracts was used together with usgs data for a geological interpretation of hydrocarbon charging history within the central ddb results point to a significant contribution from upper visean black shales highly oil prone as well as mixed oil and gas prone serpukhovian rocks and minor contribution from an additional tournaisian source devonian rocks an important hydrocarbon source within the pripyat trough have not been identified as a major source within the central ddb additional input from bashkirian to moscovian shebelinka field as well as tournaisian to lower visean rocks e g dovgal field with higher contents of terrestrial organic matter is indicated in the se and nw part respectively whereas oil source correlation contradicts major hydrocarbon migration in many cases for tournaisian to middle carboniferous reservoir horizons accumulations within upper carboniferous to permian reservoirs require vertical migration up to 4000 m along faults related to devonian salt domes 1 d thermal models indicate hydrocarbon generation during permo carboniferous time however generation in coal bearing middle carboniferous horizons in the se part of the basin may have occurred during the mesozoic

thermal response of a small ice cap to climatic forcing two dimensional finite element calculations of velocity and temperature fields have been applied to the energy balance of a cross section of barnes ice cap baffin island canada the flow plane currently is cooling near the ice divide and warming near the margin long term simula tions show a net warming trend followed by a cooling trend with a steady state average temperature similar to the present sensitivity studies on an idealized version of the flow plane show that the overall temperature responds less than surface temperature forcing because a negative feed back in temperature advection is substantially larger than a positive feed back in strain heating the response times of the flow plane by itself are somewhat faster but of the same magnitude as response times that would be estimated from one dimensional modeling when bedrock temperature calculations are included response times increase an order of magnitude but these do not substantially affect the short term response

structural features and evolution of the dniepr donets basin ukraine from regional seismic reflection profiles abstract a set of regional multichannel seismic reflection profiles crossing the dniepr donets dd basin in ukraine 100 200 km long and with a spacing of 10 15 km along strike illuminates the structure of the whole sedimentary cover the rift filled with pre and syn rift devonian sequences and overlain with post rift carboniferous permian mesozoic and palaeogene fill is clearly seen on all sections a basement layer previously identified as a riphean rift succession by refraction seismic studies constitutes in the main strata of the devonian and early carboniferous successions the structure of the rift is characterised by large scale rotational fault blocks and half grabens carried by basin parallel to normal marginal faults or by major horst blocks the total thickness of the devonian and younger succession is up to 19 km in the study area post rift carboniferous and mesozoic sediments cover the rift flanks and increase in thickness towards the rift axis and to the southeast the cumulative thickness of the carboniferous succession alone reaches 11 km with the maximum depth of their base at about 15 km major post rift tectonic events took place at the end of early visean in the middle of serpukhovian in permian times and between the mesozoic and cenozoic tectonic reactivations during carboniferous and early permian times were most pronounced in the southeastern part of the dd basin while they were least pronounced in the northwestern part of the basin merging with the pripyat trough where they are barely observed the most active development of salt structures and stocks corresponds with the periods of tectonic reactivation

the devonian and carboniferous of the moscow syneclise russian platform stratigraphy and sea level changes abstract the moscow syneclise is a vast sedimentary basin located in the centre of the east european platform the palaeozoic sequence of this syneclise and especially its devonian carboniferous part is most suitable for sea level fluctuation analysis the devonian and carboniferous sediments consist mainly of shallow marine carbonates containing several minor terrigenous intervals they attain total thicknesses of up to 1 5 km the modern stratigraphic scale includes 33 regional stages for the devonian and 32 for the carboniferous correlation of this scale with global scales is supported by conodont miospore and foraminifera zonations the new calibrated devonian and carboniferous relative sea level curves for the moscow syneclise reflect late eifelian mid frasnian early tournaisian late visean early serpukhovian and moscovian gzhelian transgressions several of these sea level changes which are particularly evident on the margins of the moscow syneclise originated in response to differential tectonic movements of the voronezh anteclise and the tokmovo uplift as well as to vertical oscillations of the entire east european craton

black shales in ukraine a review abstract as a result of a long lasting and complex geological history organic matter rich fine grained rocks black shales with widely varying ages can be found on ukrainian territory several of them are proven hydrocarbon source rocks and may hold a significant shale gas potential thick silurian black shales accumulated along the western margin of the east european craton in a foreland type basin by analogy with coeval organic matter rich rocks in poland high toc contents and gas window maturity can be expected however to date information on organic richness is largely missing and maturity patterns remain to be refined visean black shales with toc contents as high as 8 and a type iii ii kerogen accumulated along the axis of the dniepr donets rift basin ddb they are the likely source for conventional oil and gas oil prone serpukhovian black shales accumulated in the shallow northwestern part of the ddb similar black shales probably may be present in the lviv volyn basin western ukraine middle jurassic black shales up to 500 m thick occur beneath the carpathian foredeep they are the likely source for some heavy oil deposits toc contents up to 12 type ii have been recorded but additional investigations are needed to study the vertical and lateral variability of organic matter richness and maturity lower cretaceous black shales with a type iii ii kerogen toc 2 are widespread at the base of the carpathian flysch nappes but oligocene black shales menilite fm rich in organic matter 4 8 toc and containing a type ii kerogen are the main source rock for oil in the carpathians their thermal maturity increases from the external to the internal nappes oligocene black shales are also present in crimea maykop fm these rocks typically contain high toc contents but data from ukraine are missing

continental rift development in precambrian and phanerozoic europe europrobe and the dnieper donets rift and polish trough basins abstract upper crustal structure and lower crustal and mantle character of the european continental lithosphere differ significantly from west to east the processes of rifting of phanerozoic western europe s hotter thinner crust compared with the more stable thicker 45 vs 30 km proterozoic crust of the east european craton is being investigated by europrobe case studies of western and eastern european sedimentary basins the dnieper donets basin transects the southwestern part of the east european platform in a nw se direction lying between the ukrainian shield and the voronezh massif rifting took place from early frasnian until perhaps the late visean and was accompanied by major volcanic activity the distribution of both was affected by pre existing basement fault systems the syn and post rift sedimentary succession may be as thick as 20 km in the donets trough basin evolution and the present crustal geometry have been much affected by inversion during the permian in association with uralian orogenesis tectonic events of bathonian oxfordian 168 154 ma and turonian santonian 91 84 ma age are also recorded in the basin stratigraphy the polish trough lies along the boundary between the phanerozoic and proterozoic european crustal domains coincident with the trans european suture zone the presence of this rheological boundary may be paramount in structurally controlling the position of the trough tectonic subsidence analysis indicates an initial late rotliegendes early triassic syn rift phase of development subsequently episodes of increased tectonic subsidence rate occurred during the oxfordian tithonian 157 146 ma and beginning in the cenomanian 95 90 ma the oxfordian tithonian episode is likely the signature of a second extensional event correlated with intensification of rifting within the arctic north atlantic rift system while the cenomanian and later is a precursor to mild compressional intraplate orogenic movements present day crustal structure reflects the docking of phanerozoic crust against the proterozoic during palaeozoic orogenies permo carboniferous wrenching and transtensional modifications leading to formation of the polish trough as well as modifications during the late cretaceous early tertiary inversion process

magmatism and the geodynamics of rifting of the pripyat dnieper donets rift east european platform abstract the distribution of volcanism in the late devonian pripyat dnieper donets rift within the east european platform based upon the results of deep drilling indicates that pre existing basement structures and the major rift bounding faults played an important role in channelling the magmas towards the surface major and trace element and sr nd isotopic studies of the most primitive basic and ultrabasic magmas combined with estimates of the amount of extension 1 1 to 1 3 strongly suggest that magmatism was triggered by the upwelling of a thermally and geochemically anomalous mantle plume from the deep mantle during the late frasnian the peak of the magmatism occurred in the famennian coincident with the maximum amount of lithospheric extension magmatism rifting and domal basement uplife were contemporaneous at several localities within the eep suggesting that the thermal and geodynamic evolution of the platform could have been influenced by a cluster of mantle plumes during the late devonian

dynamics of sea surface temperature anomalies in the southern ocean diagnosed from a 2d mixed layer model we analyze the processes responsible for the generation and evolution of sea surface temperature anomalies observed in the southern ocean during a decade based on a 2d diagnostic mixed layer model in which geostrophic advection is prescribed from altimetry anomalous air sea heat flux is the dominant term of the heat budget over most of the domain while anomalous ekman heat fluxes account for 20 40 of the variance in the latitude band 40 60 s in the acc pathway lateral fluxes of heat associated with anomalous geostrophic currents are a major contributor dominating downstream of several topographic features reflecting the influence of eddies and frontal migrations a significant fraction of the variability of large scale sst anomalies is correlated with either enso or the sam each mode contributing roughly equally the relation between the heat budget terms and these climate modes is investigated showing in particular that anomalous ekman and air sea heat fluxes have a co operating effect with regional exceptions hence the large sst response associated with each mode it is further shown that enso or sam locked anomalous geostrophic currents generate substantial heat fluxes in all three basins with magnitude comparable with that of atmospheric forcings for enso and smaller for the sam except for limited areas enso locked forcings generate sst anomalies along the acc pathway and advection by mean flows is found to be a non negligible contribution to the heat budget exhibiting a wavenumber two zonal structure characteristic of the antarctic circumpolar wave by contrast sam related forcings are predominantly zonally uniform along the acc hence smaller zonal sst gradients and a lesser role of mean advection except in the southwest atlantic while modeled sst anomalies are significantly correlated with observations over most of the southern ocean the analysis of the data model discrepancies suggests that vertical ocean physics may play a significant role in the nonseasonal heat budget especially in some key regions for mode water formation

the antarctic circumpolar wave a beta effect in ocean atmosphere coupling over the southern ocean the antarctic circumpolar wave acw is a nominal 4 yr climate signal in the ocean atmosphere system in the southern ocean propagating eastward at an average speed of 6 8 cm s21 composed of two waves taking approximately 8 years to circle the globe the acw is characterized by a persistent phase relationship between warm cool sea surface temperature sst anomalies and poleward equatorward meridional surface wind msw anomalies recently white and chen demonstrated that sst anomalies in the southern ocean operate to induce anomalous vortex stretching in the lower troposphere that is balanced by the anomalous meridional advection of planetary vorticity yielding msw anomalies as observed in the present study the authors seek to understand how this atmospheric response to sst anomalies produces a positive feedback to the ocean i e an anomalous sst tendency displaced eastward of sst anomalies that both maintains the acw against dissipation and accounts for its eastward propagation to achieve this we couple a global equilibrium climate model for the lower troposphere to a global heat budget model for the upper ocean in the absence of coupling the model antarctic circumpolar current acc advects sst anomalies from initial conditions to the east at speeds slower than observed taking 12 14 years to circle the globe with amplitudes that become insignificant after 6 8 years in the presence of coupling eastward speeds of the model acc are matched by those due to coupling together yielding a model acw of a nominal 4 yr period composed of two waves that circle the globe in approximately 8 years as observed feedback from atmosphere to ocean works through the anomalous zonal surface wind response to sst anomalies yielding poleward ekman flow anomalies in phase with warm sst anomalies as such maintenance of the model acw is achieved through a balance between anomalous meridional ekman heat advection and anomalous sensible plus latent heat loss to the atmosphere this balance requires the alignment of covarying sst and msw anomalies to be tilted into the southwest northeast direction which accounts for the spiral structure observed in global sst and sea level pressure anomaly patterns around the southern ocean eastward coupling speeds of the model acw derive from a beta effect in coupling that displaces a portion of the anomalous meridional ekman heat advection and its corresponding anomalous sst tendency to the east of sst anomalies therefore the acw is an example of self organization within the global ocean atmosphere system depending upon the spherical shape of the rotating earth for its propagation and the mean meridional sst gradient for its maintenance and producing a net poleward eddy heat flux in the upper ocean that tends to reduce this mean gradient

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

temperature profile for glacial ice at the south pole implications for life in a nearby subglacial lake airborne radar has detected 100 lakes under the antarctic ice cap the largest of which is lake vostok international planning is underway to search in lake vostok for microbial life that may have evolved in isolation from surface life for millions of years it is thought however that the lakes may be hydraulically interconnected if so unsterile drilling would contaminate not just one but many of them here we report measurements of temperature vs depth down to 2 345 m in ice at the south pole within 10 km from a subglacial lake seen by airborne radar profiling we infer a temperature at the 2 810 m deep base of the south pole ice and at the lake of 9 c which is 7 c below the pressure induced melting temperature of freshwater ice to produce the strong radar signal the frozen lake must consist of a mix of sediment and ice in a flat bed formed before permanent antarctic glaciation it may like siberian and antarctic permafrost be rich in microbial life because of its hydraulic isolation proximity to south pole station infrastructure and analog to a martian polar cap it is an ideal place to test a sterile drill before risking contamination of lake vostok from the semiempirical expression for strain rate vs shear stress we estimate shear vs depth and show that the icecube neutrino observatory will be able to map the three dimensional ice flow field within a larger volume 0 5 km3 and at lower temperatures 20 c to 35 c than has heretofore been possible

quasi stationary enso wave signals versus the antarctic circumpolar wave scenario 1 two conflicting views on the causal mechanism of the antarctic interannual variability often appear in the literature i e whether it is remotely teleconnected to tropical enso events or is a self sustained eastward propagating circumpolar wave generated locally by an ocean atmosphere coupling mechanism using a fourier decomposition into stationary and propagating components of several oceanic and atmospheric variables we show that most of the antarctic interannual variability can be explained by a geographically phase locked standing wave train linked to tropical enso episodes this enso modulated quasi stationary variability is not zonally uniform rather the strongest enso impact is consistently concentrated in the pacific sector of the southern ocean the eastward propagating wave component is found to be not only minor 25 of variability but also intermittent in phase yielding little support for the so called antarctic circumpolar wave scenario

hydrocarbon habitat of the dniepr donets depression abstract basin inversion depending on its intensity can enhance the trapping potential of a basin or causes destruction of major hydrocarbon resources post inversion subsidence depending on its magnitude and the amount of syn inversion erosion can induce a second phase of hydrocarbon generation and the charging of inversion structures however this mechanism which contributed for instance to the hydrocarbon habitat of inverted basins in the southern north sea was not effective in the dniepr donets basin the dniepr donets depression forms part of the pripyat dniepr donets donbass karpinsky aulacogen that evolved as a devonian rift the post rift subsidence of this basin was interrupted during the late early permian when its southeastern parts were partly inverted further inversion pulses straddle the jurassic cretaceous and the cretaceous tertiary boundaries the dniepr donets depression hosts the most important hydrocarbon province of the ukraine at the beginning of 1994 ultimate recoverable reserves in established accumulations past production and remaining reserves amounted to about 170 10 6 t of oil and gas condensate and 980 10 9 m 3 gas the bulk of oil and gas accumulations is contained in carboniferous to early permian postrift series source rocks occur in devonian syn rift and carboniferous post rift series these attained maturity prior to basin inversion hydrocarbon accumulations are characterized by multiple reservoir seal pairs the mature syn rift devonian and the immature post inversion series contain only minor hydrocarbon accumulations oil and gas accumulations are mainly trapped in syn rift salt induced and inversion related structures the latter received their hydrocarbon charge mainly due to inversion induced destruction of pre existing accumulations and ensuing re migration of hydrocarbons

numerical modelling of the thermal evolution of the northwestern dniepr donets basin ukraine abstract the dniepr donets basin ddb is a late devonian rift structure located within the east european craton numerical heat flow models for 13 wells calibrated with new maturity data were used to evaluate temporal and lateral heat flow variations in the northwestern part of the basin the numerical models suggest that heat flow was relatively high during late carboniferous and or permian times the relatively high heat flow is probably related to an early permian re activation of tectonic activity reconstructed early permian heat flow values along the axial zone of the rift are about 60 mw m2 and increase to 90 mw m2 along the northern basin margin these values are higher than those expected from tectonic models considering a single late devonian rifting phase the calibration data are not sensitive to variations in the devonian carboniferous heat flow therefore the models do not allow deciding whether heat flows remained high after the devonian rifting or whether the reconstructed permian heat flows represent a separate heating event analysis of the vitrinite reflectance data suggest that the northeastern dniepr donets basin is characterised by a low mesozoic heat flow 30 35 mw m2 whereas the present day heat flow is about 45 mw m2

a transient temperature solution for bore hole model testing transient temperature variations in a vertical column of ice with horizontally unifo rm conditions constant vertical strain ra te and specified surface tempera ture and basal heat flux can be calculated analytically the solution consists of eigenfu nctions which are forms of the confluent hypergeometric function this solution shows that advection and diffusion have clearly separated areas of dominance with diffusion being a sufficient approximation for small scale perturba tions in the temp erature profile and advection placing an upper limit on the response time of the ice sheet as a whole this solution is useful for analysis and testing of numerical models for evaluation of the response time of an ice sheet and for exploratory analysis of real bore hole data the lowest eigenvalue of the solution determines the time scale for transient decay of temperature anomalies the time scale can be determined for more general strain rates using a finite differenc e approximation to the linearized energy balance equation

long term variation of the antarctic circumpolar wave 1 during the period 1968 1999 the character of circum antarctic anomalies in sea level pressure sea ice edge and sea surface temperature changed substantially an antarctic circumpolar wave acw is only clearly visible in the period 1985 1994 before and perhaps after this the signal particularly in sea level pressure is quite different with no clear sign of precession accompanying the change from precessional to nonprecessional modes is a change in the spatial pattern of variability and a change in the predictability of atmospheric anomalies from oceanic forcing evidence from general circulation model integration suggests that during the precessional mode of the acw there is enhanced predictability as would be required to support a coupled ocean atmosphere interaction

the antarctic circumpolar wave in a coupled ocean atmosphere gcm abstract a phenomenon called the antarctic circumpolar wave acw suggested earlier from fragmentary observational evidence has been simulated realistically in an extended integration of a max planck institute coupled general circulation model the acw both in the observations and in the model constitutes a mode of the coupled ocean atmosphere sea ice system that inhabits the high latitudes of the southern hemisphere it is characterized by anomalies of such climate variables as sea surface temperature sea level pressure meridional wind and sea ice that exhibit intricate and evolving spatial phase relations to each other the simulated acw signal in the ocean propagates eastward over most of the high latitude southern ocean mainly advected along in the antarctic circumpolar current on average it completes a circuit entirely around the southern ocean but is strongly dissipated in the south atlantic and in the southern indian ocean just marginally maintaining statistical significance in these areas

comments on southern mid to high latitude variability a zonal wavenumber 3 pattern and the antarctic circumpolar wave in the csiro coupled model abstract variability in the southern atmospheric circulation at mid to high latitudes with a dominant quasi stationary wavenumber 3 pattern has been reported in many observational studies the variability is barotropic in nature with signals in the middle troposphere as well as at the atmosphere ocean interface moreover there are preferred fixed centers for the strongest anomalies these features are well reproduced by the commonwealth scientific and industrial research organisation coupled model on various timescales on the interannual timescale an index of the modeled wavenumber 3 pattern shows little correlation with the modeled southern oscillation index suggesting that the variability associated with wavenumber 3 anomalies is separate to modeled enso like events however the variation of the pattern index is strikingly similar to and highly correlated with the modeled oceanic variability the associated oceanic anomalies move eastward and are similar to those of the observed antarctic circum

forcing of the antarctic circumpolar wave by el nino southern oscillation teleconnections we address several issues regarding the antarctic circumpolar wave acw these include the extent to which the acw is related to el nino southern oscillation enso cycles and the need to reconcile differences between the observed zonal wavenumber 2 pattern and the wavenumber 3 pattern found in coupled ocean atmosphere models in the present study we revisit the sea surface temperature sst signal of the observed acw we find that the associated sst variations may be decomposed into several empirical orthogonal functions eofs that are linearly independent the first four eofs describe 84 of the total variance on timescales of 3 7 years and superposition of sst signals of the four eofs reproduces sst signals of the observed acw given that eof analysis can only describe standing oscillations we then employ complex eof ceof analysis suitable for studying propagating waves the first two ceofs denoted ceofsst1 and 2 account for 70 of the total variance and the sst variability reconstructed from them again reproduces the observed acw the real part of ceofsst1 44 of the total variance is similar to the first real eof eofsst1 both eofsst1 and ceofsst1 may be identified with enso and have a wavenumber 2 zonal pattern in the southern middle to high latitudes ceofsst1 is the major constituent of the acw in the period of 1981 1997 the associated atmospheric circulation displays a pacific south america psa pattern statistical analyses demonstrate that the psa pattern teleconnected to enso is the major mechanism that forces this principal constituent of the acw ceofsst2 26 of the total variance has a zonal wavenumber 3 pattern in the same latitude band similar to that simulated by several coupled models we suggest that if enso is not adequately resolved in coupled models but structures with zonal wavenumber 3 pattern are then the modeled acw would appear to have a zonal wavenumber 3 pattern

sedimentary cycles and paleogeography of the dnieper donets basin during the late visean serpukhovian based on multiscale analysis of well logs abstract an integrated approach combining the available geological geophysical information was employed to construct a series of paleogeographic maps of the northwestern part of the dnieper donets basin ddb during the late visean serpukhovian early carboniferous the major source of information consists of well log data the basin fill shows a pattern of stacked transgressive regressive units of different order correlations on the scale of the basin are based on biostratigraphy seismics cyclostratigraphic subdivisions and correlations of the successions throughout the basin the cyclicity has a multifold character short shallowing upward transgressive regressive t r cycles characterized by the presence of hydrocarbons productive horizons cover a time span of the order of 500 ka long cycles include 4 to 6 short t r cycles they seem to be correlatable to western europe and probably to north america the long cycles form part of higher order stacking patterns indicative of still longer cycles considering the variable thickness of the cycles throughout the basin tectonics must have influenced the character of the series in addition to glacio eustatic sea level fluctuations the paleogeographical development of the basin shows axial deposition during the late visean likely related to late stage rifting related subsidence of a central graben followed by basin wide subsidence related to thermal subsidence during the serpukhovian

blocking over the south pacific and rossby wave propagation abstract atmospheric blocking events over the south pacific are investigated using a 39 yr record of 500 hpa height fields from the ncep ncar reanalysis dataset the analysis extends earlier work using a 16 yr record and confirms that the occurrence of blocking over the southeast pacific is strongly modulated by the enso cycle during austral spring and summer comparison of results at 500 hpa with the 300 hpa meridional wind component showed that blocking events are associated with large scale wave trains lying across the south pacific from the region of australia to southern south america similar wave trains are evident in both hemispheres in singular value decomposition analyses between 300 hpa meridional wind components and tropical pacific outgoing longwave radiation olr anomalies the hypothesis that the divergence associated with tropical olr anomalies forces an extratropical wave response that results in enhanced blocking over the southeast pacific was tested using a linearized barotropic vorti

thermomechanical coupling of ice flow with the bedrock two aspects of thermal coupling with bedrock are considered the coupled time dependent problem of co evolving temperatures in lithosphere and ice and the influence of basal topography on steady temperature distribution within the ice the nature of the time dependent coupling is found to depend on the horizontal velocity as has been suggested there is a cooling of steady temperatures on bedrock highs but this is phase shifted downstream when horizontal velocities increase this observation may have consequences for geomorphological processes such as plucking and protection the effect of bedrock channelling on steady temperature is considered the positive anomaly of basal temperature due to channelling increases as the transverse wavelength decreases but not monotonically reaching a plateau when both the wavelengths of the basal topography are around 100 km

factors controlling shale microstructure and porosity a case study on upper visean rudov beds from the ukrainian dneiper donets basin the present contribution aims for a characterization of microstructure and pore space distribution of upper visean rudov beds considered the main source rock for conventional oil deposits in the ukrainian dneiper donets basin and a prospect for unconventional hydrocarbon production in recent years broad ion beam scanning electron microscopy sem mapping revealed a remarkably heterogeneous microstructure controlled by diagenetic precipitates fe mg carbonates albite formation of these precipitates is likely triggered by organic matter decomposition and represents an important influencing factor for overall porosity and permeability furthermore shale diagenesis also influences mechanical properties as suggested by nanoindentation tests the sem visible organic matter porosity is restricted to solid bitumen although pores less than 2 3 nm in vitrinites of overmature samples are indicated by focused ion beam sem results they cannot be resolved clearly by this method pore generation in solid bitumen that likely formed in situ in primary amorphous organic matter already starts at the early oil window in samples from the basinal oil prone organofacies whereas most porous solid bitumen at peak oil maturity was interpreted as relicts of primary oil migration representing an earlier oil phase that predominantly accumulated in quartz rich layers and became nanoporous during secondary cracking in the terrestrially dominated transitional to marginal organofacies pore generation in pyrobitumen resulting from gas generation occurs significantly later and is less intense formation of authigenic clay and carbonate minerals within pyrobitumen is likely related to organic acids formed during bitumen decomposition and implies the presence of an aqueous phase even in pores that are apparently filled exclusively with solid bitumen