classification of huminite iccp system 1994 abstract in the new classification iccp system 1994 the maceral group huminite has been revised from the previous classification iccp 1971 int handbook coal petr suppl to 2nd ed to accommodate the nomenclature to changes in the other maceral groups especially the changes in the vitrinite classification iccp 1998 the new vitrinite classification iccp system 1994 fuel 77 349 358 the vitrinite and huminite systems have been correlated so that down to the level of sub maceral groups the two systems can be used in parallel at the level of macerals and for finer classifications the analyst now has according to the nature of the coal and the purpose of the analysis a choice of using either of the two classification systems for huminite and vitrinite this is in accordance with the new iso coal classification that covers low rank coals as well and allows for the simultaneous use of the huminite and vitrinite nomenclature for low rank coals

residual mean solutions for the antarctic circumpolar current and its associated overturning circulation abstract residual mean theory is applied to the streamwise averaged antarctic circumpolar current to arrive at a concise description of the processes that set up its stratification and meridional overturning circulation on an f plane simple solutions are found in which transfer by geostrophic eddies colludes with applied winds and buoyancy fluxes to determine the depth and stratification of the thermocline and the pattern of associated residual meridional overturning circulation

in situ measurements of the evolution of young sea ice 1 we present data from in situ measurements of the salinity evolution of young sea ice in the arctic the measurements were carried out with very high vertical and temporal resolution over the course of a few days until the ice had reached a thickness of around 20 cm the measured bulk salinity profiles show that during ice growth sea ice salinity is continuous across the ice ocean interface and that there is no instantaneous loss of salt at the advancing front measured salt fluxes emanating from the ice are as high as 90 g m 2 h 1 during the first few hours of new ice formation and are roughly half as large during later stages of the experiments the bulk salinity within the ice decreases continuously with time from the ocean water salinity to a near steady state value of around 4 parts per thousand ppt these results are interpreted with ideas from mushy layer theory using a rayleigh number to analyze gravity drainage as the driving mechanism for the observed salt loss in our experiments gravity drainage occurs for a critical rayleigh number of around 10 in close agreement with earlier theoretical and experimental studies

cooling of the west spitsbergen current isopycnal diffusion by topographic vorticity waves 1 we investigate the heat budget in the west spitsbergen current on the basis of theoretical considerations and current meter data across the slope at 78 83 n between september 1997 and september 1998 the dispersion relation for topographically trapped waves along the west spitsbergen slope with a barotropic along slope velocity is calculated by use of an idealized numerical model signal processing and coherence calculations of the current meter data show that barotropic vorticity waves with enhanced energy at the diurnal period exist along the slope a wave length of 32 km is given by the dispersion relation for the 24 hour period and a corresponding second mode with a 35 hour period coherence calculations and complex demodulations of the current meter time series confirm the spatial and temporal variations given by the dispersion relation the eddy characteristics of the first two modes are used to estimate the heat loss of the warm core of the west spitsbergen current by isopycnal eddy diffusion we present the first isopycnal heat loss estimates obtained through dynamical considerations of the west spitsbergen current and compare them with earlier diagnostic estimates for the mean heat loss in the subsurface layers within the standard errors we estimate the heat flux to be o 1000 w m2 throughout the year except for the summer months june july if the 9798 heat flux time series are representative for the subsurface layer between 100 and 500 m depth the heat loss is on the same order of magnitude as the mean winter value of 1050 w m2 from earlier diagnostic estimates

organofacies composition of upper jurassic lowermost cretaceous source rocks danish central graben and insight into the correlation to oils in the valdemar field abstract the organic rich marine shales of the upper jurassic lowermost cretaceous farsund formation are the main hydrocarbon source rocks for the cretaceous chalk reservoir of the valdemar field danish north sea geochemical analyses of oil extracts from core samples across the greater valdemar field show substantial heterogeneity of the reservoir oils suggesting contribution from kitchen areas with source rocks of variable organofacies and thermal maturity in order to better understand the source rock facies that charged the field a refined organofacies characterization of the upper jurassic lowermost cretaceous marine shale source rock succession farsund formation in the danish central graben was established this organofacies characterization is based on integration of petrographic and geochemical data and demonstrates large variations in both the regional and local distribution of the organofacies at the sequence level in the shales within the danish central graben in addition the organofacies characterization shows that the respective sequences in the succession may be represented by several organofacies at the same time part of the explanation to the heterogeneity in the oil types accumulated within the valdemar field may lie in the presence of different organofacies within the uppermost sequences vol 3 to ryaz 1 in the three kitchen areas each organofacies presumable generates different types of oils and the variation in the relative proportions of the different organofacies likely determines the composition of the generated oils one dimensional 1 d maturity modelling at three pseudo well locations each representing a potential farsund formation kitchen shows that all kitchens are in the main oil window and that mainly oil was expelled from the volg 3 to ryaz 1 sequences modelling indicates that i average values of toc hi thickness and the kinetic model are the main controls on generation and expulsion of hydrocarbons and ii by increasing these parameters expulsion could also occur from the lower part of the succession

eddy overturning of the antarctic slope front controls glacial melting in the eastern weddell sea 1 the eastern weddell sea is characterized by narrow continental shelves and warm deep water wdw is located in close proximity to the ice shelves in this region the exchange of wdw across the antarctic slope front asf determines the rate of basal ice shelf melting here we present a unique data set consisting of 2351 vertical profiles of temperature and salinity collected by southern elephant seals mirounga leonina and a profile beneath the fimbul ice shelf fis obtained via drilling through 395 m of ice this data set reveals variations in salinity and temperature through winter and using a conceptual model of the coastal salt budget we quantify the main exchange processes our data show that modified wdw with temperatures below 1 5 c is advected onto the shelf and into the ice shelf cavities by an eddy overturning of the asf the onshore ekman flux of surface waters during summer is the main source of freshwater that leads to the formation of low salinity shelf waters in the region the modified wdw that reaches beneath the ice shelves is too cold for basal ice shelf melting to create such low salinity water a high resolution model of an idealized asf continental shelf ice shelf system supports the conclusions from the data analysis the inflow of wdw onto the continental shelf and into the ice shelf cavity occurs within a bottom boundary layer where the eddy advection in the model is particularly strong in close agreement with the observed vertical profile of temperature beneath the fis citation nost o a m biuw v tverberg c lydersen t hattermann q zhou l h smedsrud and k m kovacs 2011 eddy overturning of the antarctic slope front controls glacial melting in the eastern weddell sea j geophys res 116 c11014 doi 10 1029 2011jc006965

eddy overturning across a shelf edge front kongsfjorden west spitsbergen 1 eddy overturning across a shelf edge front has been investigated in a simplified model setup comprising an along slope uniform shelf and slope with a slope current results from three model runs are presented each initiated with and nudged toward a sharp shelf edge front in temperature salinity density and velocity data collected off kongsfjorden at spitsbergen were used for initiating the model runs three distinctly different density fronts were used to initialize the model runs one with a negative cross frontal density gradient toward the shelf one with a positive density gradient and one with a combination of negative density gradient in the upper water column and a positive in the lower water column the model results indicate that the initial cross frontal density gradients determine the eddy overturning direction acting toward flattened or terrain following isopycnals the steady state modeled fronts resemble quite well the observed front structures as well as temperature and salinity fields this indicates that eddy overturning plays an important role in cross frontal exchange of water masses along the shelf edge front off west spitsbergen the eulerian mean cross slope flow is close to zero and the corresponding fluxes do not describe the correct vertical distribution

vitrinite reflectance gradients of deep wells with thick chalk sections and high pressure implications for source rock maturation danish norwegian central graben north sea abstract nine deep wells td from 4793 to 5903 m drilled with jurassic syn rift targets in the danish norwegian central graben show abnormal vitrinite reflectance vr profiles they all penetrated thick up to 950 m post rift upper cretaceous chalk sections and about 3000 m of cenozoic mudstone dominated sediments the penetrated strata in the wells are further characterised by high fluid pressures overpressure in the thick sections of upper jurassic lowermost cretaceous mudstones forming the principal source rocks in the area the overpressure in the jurassic sandstone reservoir target may attain a value of about 50 mpa the wells display overall the same vr profiles characterised by three vr segments i a more or less well defined increase in vr through the cenozoic to the top of the upper cretaceous chalk ii an interpolated lower vr gradient through the chalk section and iii a likewise well defined increase in vr from the base of the chalk and through the upper jurassic lowermost cretaceous mudstones but with a higher gradient than determined for the cenozoic strata the vr values at the top of the source rock section are much lower than expected indicating that maturation is significantly retarded the lower vr values are determined by two factors i the high thermal conductivity of chalk accounts for the interpolated lower vr gradients in the thick chalk sections while the higher vr gradients and the higher geothermal gradients in the upper jurassic lowermost cretaceous source rock mudstones agree with the low thermal conductivity of mudstone and ii the thick sections of overpressured mudstones serve as insulator for the overlying chalk and retard source rock maturation as excessive pressure can prevent liquid and gaseous generation products to escape the source rock and thereby preventing the condensation and reorganisation of the organic matter which is necessary to increase maturity indirect evidence of the effect of excessive pressure comes from maturity modelling of the measured vr values in the danish hejre 1 well using the easy ro and presro models the latter incorporating pressure calibrated with measured present day pressures the presro model is able to predict the measured vr values and thus the maturity gradient and predicts the source rock interval in the well to be in the middle of the oil window even at a depth of 5000 m hence as a consequence of the irregular maturity trends the upper jurassic lowermost cretaceous source rocks are of lower thermal maturity than expected and if the top of the oil window is set at a vr of 0 6 ro the decreased maturation results in a downward displacement of the top of the oil window of up to approximately 200 350 m

turbulent exchange coefficients for the ice ocean interface in case of rapid melting 1 in the marginal ice zones drifting sea ice encounters large ocean heat fluxes and melting rates however as found from modelling studies and observations of ice melting double diffusive effects at the ice ocean interface limit the melting rates in this paper direct measurements of turbulent heat and salt fluxes from the marginal ice zone during rapid melting are presented the strength of double diffusion is found to be significant and close to the range suggested from other studies calculated melting rates when double diffusive effects are present are compared to melting rates calculated from a traditional bulk parameterization of ocean heat flux for a range of temperatures and friction velocities often encountered within the marginal ice zones this comparison shows that by ignoring double diffusive effects melting rates are overestimated by several cm per day which may have a significant impact on a predicted future ice cover

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

winter sea ice melting in the atlantic water subduction area svalbard norway herein we study a small area along the shelf west of spitsbergen near prins karls forland where warm saline atlantic water of the west spitsbergen current currently first encounters sea ice this sea ice is drifting in a coastal current that carries arctic water originating from the barents sea northward over the shelf our aim was to investigate whether melting of sea ice by atlantic water in this area might be a significant factor that could contribute to the formation of a cold halocline layer that isolates the sea ice from further melting from below observations of temperature and salinity profiles were collected during two winters via ctd srdl instruments deployed on harbor seals phoca vitulina and fed into a heat and freshwater budget box model in order to quantify the importance of melting relative to other processes that could transform the shelf water mass during winter cross frontal exchange of atlantic water from the west spitsbergen current driven by buoyancy forcing rather than ekman upwelling was determined to be the source of the heat that melted drift ice on the shelf some local sea ice formation did take place but its importance in the total heat and freshwater budgets appeared to be minor the data suggest that the production of a cold halocline layer was preceded by southerly winds and rapid drift ice melting

early spring oceanic heat fluxes and mixing observed from drift stations north of svalbard abstract from several drifting ice stations north of svalbard norway observations were made in early spring of the ocean turbulent characteristics in the upper 150 m using a microstructure profiler and close to the under ice surface using eddy correlation instrumentation the dataset is used to obtain average heat fluxes at the ice water interface in the mixed layer across the main pycnocline as well over different water masses in the region the results are contrasted with proximity to the branches of the warm and saline atlantic water current the west spitsbergen current wsc which is the main oceanic heat and salinity source both to the region and to the arctic ocean hydrographic properties show that the surface water mass modification is typically due to atmospheric cooling with relatively less influence of ice melting surface heat fluxes of o 100 w m 2 are found within the branches of the wsc and over shelf areas with elevated levels of mixing due to strong tides away from the shelves and

temporal organic facies variations of upper jurassic lowermost cretaceous source rocks in the danish central graben north sea abstract the upper jurassic lowermost cretaceous marine mudstones of the farsund formation constitute the principal source rocks in the danish north sea sector with the uppermost bo member considered most prolific however the areal distribution of the bo member is limited and since it is thermally immature over large areas it is unlikely that this interval has generated sufficient quantities of petroleum to fill the reservoirs in the danish sector in search for additional source rocks potential we have investigated the lower part of the farsund formation using a sequence stratigraphic framework organic geochemical screening and petrographic analyses of core and cuttings samples have been performed to define the source potential and map the regional distribution of organic rich sequences in the upper jurassic succession the study outlines variations of both maturity source rock quality and kerogen quality at sequence level with an upward improvement from poor gas prone type ii kerogen in the kimm 1 and kimm 3 sequences to highly oil prone type ii kerogen in the volg 1 volg 4 and ryaz 1 sequences the kerogen is dominated by fluorescent aom and liptinite and structural alginite in form of leiosphaerida and tasmanites type telalginites throughout the entire succession with vertical and regional variations in the amount of larger tasmanites the study shows that the shales in volg 1 and 3 sequences are organic rich and oil prone with toc 4 wt and hi 340 mg hc g toc particularly the volg 1 sequence being the thickest and laterally most widespread forms a significant supplementary source for oil in the danish sector

wintertime warming of an arctic shelf in response to large scale atmospheric circulation 1 observations on the west spitsbergen shelf have shown that the dynamic response of the shelf to wind forcing has a profound effect on the heat content of the water hydrographic and atmospheric data have been analysed with respect to the relative importance of surface heat fluxes and advective processes on ocean temperature during the arctic winter of 2005 06 periods of sustained along shelf winds generated upwelling and cross shelf exchange causing extensive flooding of the coastal waters with warm atlantic water from the west spitsbergen current the winter temperature of the west spitsbergen shelf reverted to that typical of fall interrupting the normal cycle of sea ice formation in the region

estimates and implications of surface eddy diffusivity in the southern ocean derived from tracer transport abstract near surface effective diffusivities associated with geostrophic eddies in the southern ocean are estimated by numerically monitoring the lengthening of idealized tracer contours as they are strained by surface geostrophic flow observed by satellite altimetry the resulting surface diffusivities show considerable spatial variability and are large 2000 m2 s 1 on the equatorward flank of the antarctic circumpolar current and are small 500 m2 s 1 at the jet axis regions of high and low effective diffusivity are shown to be collocated with regions of respectively weak and strong isentropic potential vorticity gradients the maps of diffusivity are used along with climatological estimates of surface wind stress and air sea buoyancy flux to estimate surface meridional residual flows and the relative importance of eulerian and eddy induced circulation in the streamwise averaged dynamics of the antarctic circumpolar current

stirring and mixing in the mantle by plate scale flow large persistent blobs and long tendrils coexist the stirring of a small passive heterogeneity in an unsteady circulation is investigated by following the boundary of the heterogeneity the circulation mimics features of plate scale flow after initial release the heterogeneity is stirred and subsequently consists of at least one large blob connected to long but thin tendrils tendrils exponentially lengthen and exponentially thin with time as predicted by a turbulent mixing law but the width of blobs decays about 100 times more slowly the blobs mix slowly because they are smaller than the scale of flow and are sheared and occasionally unmixed by the laminar flow within the interiors of convection cells the decay time of 1 to 100 km sized heterogeneities is on the order of billions of years for whole mantle convection and thus is in accord with isotopic observations which indicate the mantle has chemical heterogeneities persisting for billions of years

can eddies set ocean stratification abstract a simple theory is presented for the buoyancy anomaly and depth of penetration of a warm lens created by a surface buoyancy flux and ekman pumping in an initially homogeneous rotating fluid it is assumed that the overturning of isopycnals induced by pumping and differential heating balances the counteroverturning tendency of baroclinic instability baroclinic eddies not only develop on the stratified lens but also play a fundamental role in setting its stratification the theory is successfully tested against numerical and laboratory experiments in which the mechanically induced deepening of a buoyant lens is arrested by its baroclinic instability finally the possibility is discussed that the eddy transfer process studied here might play a role in setting the stratification and depth of the main thermocline in the ocean

connecting antarctic cross slope exchange with southern ocean overturning previous idealized investigations of southern ocean overturning have omitted its connection with the antarctic continental shelves leaving the influence of shelf processes on antarctic bottom water aabw export unconsidered in particular the contribution of mesoscale eddies to setting the stratification and overturning circulation in the antarctic circumpolar current acc is well established yet their role in cross shelf exchange of water masses remains unclear this study proposes a residual mean theory that elucidates the connection between antarctic cross shelf exchange and overturning in the acc and the contribution of mesoscale eddies to the export of aabw the authors motivate and verify this theory using an eddy resolving process model of a sector of the southern ocean the strength and pattern of the simulated overturning circulation strongly resemble those of the real ocean and are closely captured by the residualmean theory over the continental slope baroclinic instability is suppressed and so transport by mesoscale eddies is reduced this suppression of the eddy fluxes also gives rise to the steep v shaped isopycnals that characterize the antarctic slope front in aabw forming regions of the continental shelf furthermore to produce water on the continental shelf that is dense enough to sink to the deep ocean the deep overturning cell must be at least comparable in strength to wind driven mean overturning on the continental slope this results in a strong sensitivity of the deep overturning strength to changes in the polar easterly winds

simple kinetic models of petroleum formation part iii modelling an open system abstract the movement of petroleum from organic rich source beds to potential carrier beds is the net result of two processes expulsion the release of generated petroleum from kerogen within the source bed and primary migration flow of a petroleum phase through the inorganic void networks of the source bed and all other intervening fine grained rocks expulsion is by far the more important process within the source bed orgas a simple zero dimensional model of the source rock as an open system explicitly models expulsion concurrent with oil and gas generation and oi lgas cracking as a storage threshold problem oil and gas are retained adsorbed absorbed within kerogen until their concentrations exceed the respective sorptive capacity of the residual organic carbon 0 1 and 0 02 g g ck 1 the initial hydrogen index hl 0 controls the important balance between potential sorbate petroleum and sorbant residual carbon using simple geochemical measurements the initial organic carbon is divided into initial oil inert kerogen and oil and gas generative reactive kerogen components reactive kerogens are assigned to one of five global kinetic organofacies with pre determined kinetic parameter sets governing separately rates of oil and gas generation kinetic parameters governing the rates of oil cracking within the source rock are predicted from hl 0 the two most important determinants of source rock behaviour are organofacies and hl 0 at a reference constant heating rate of 2 c ma 1 the projected oil expulsion threshold for typical organofacies members increases in the order a de 100 110 120 135 c f typically expels no oil an order of magnitude increase decrease in heating rate increases decreases these thresholds by ca 15 c typical cumulative gas mass fractions in their ultimate expulsion products are a f 0 25 0 3 0 25 0 65 and 1 0 g g 1 a value of 200 mg hc g c 1 is an approximate minimum hl 0 prerequisite for oil expulsion irrespective of absolute petroleum potential p 0 as a family coals vary dramatically in their expulsion behaviour as their hl 0 ranges both above and velow this value primary migration is efficient for expulsive source rocks movement within the source bed is limited only at low p 0 a source rocks total genetic potential p 0 thickness becomes important during migration outside the source bed it potentially restricts the primary migration distance and the excess of petroleum available for secondary migration and entrapment we evaluate primary migration approximately using a small migration loss factor no more than about 10 saturation of porosity or 1 mg g 1 coupled with an understanding of fluid potential gradients which determine migration direction within the stratigraphic architecture ultimately kerogen degradation and oil to gas cracking in the source rock are the rate limiting processes in petroleum accumulation

source rock dispersed organic matter characterization tsop research subcommittee results abstract because sedimentary organic matter consists of a diverse mixture of organic components with different properties a combination of chemcial and petrographic results offers the most complete assessment of source rock properties the primary purpose of this society for organic petrology tsop subcommittee is to contribute to the standardization of kerogen characterization methods specific objectives include 1 evaluation of the applications of different organic matter petrographic classifications and terminology and 2 integration of petrographic and geochemical results these objectives were met by completing questionnaires and petrographic geochemical and photomicrograph round robin exercises samples that were selected for this study represent different petrographic and geochemical properties and geologic settings to help identify issues related to the utilization of different classifications and techniques petrographic analysis of the organic matter was completed using both a prescribed classification and the individual classification normally used by each participant total organic carbon toc rock eval pyrolysis and elemental analysis were also completed for each sample significant differences exist in the petrographic results from both the prescribed and individual classifications although there is general agreement about the oil vs gas prone nature of the samples comparison of results from individual classifications is difficult due to the variety of nomenclature and methods used to describe an organic matter assemblage results from the photomicrograph exercise document that different terminology is being used to describe the same component although variation in toc and rock eval data exists geochemical results define kerogen type and generative potential recommendations from this study include 1 1 a uniform organic matter classification must be employed which eliminates complex terminology and is capable of direct correlation with geochemical parameters 2 2 a standardized definition and nomenclature must be used for the unstructured amorphous organic matter category subdivisions of this generalized amorphous category are needed to define its chemical and environmental properties 3 3 standardized techniques including multimode illumination types of sample preparations and data reporting will help eliminate variability in the type and amount of organic components reported

formation and evolution of the surface mixed layer and halocline of the arctic ocean fresh water from summer ice melt and the total freshwater content of the arctic ocean water column above the thermocline are estimated from vertical profiles of temperature and salinity observed on the i b oden 1991 cruise the seasonal ice melt ranges from 0 5 m to slightly above 1 m and is moderately uniform over the observation area regions of lower melting are seen over the morris jesup plateau the freshwater content is calculated relative to the salinity just above the thermocline north of the barents sea the freshwater content increases toward the interior of the arctic ocean showing that fresh water is advected from other regions into the observation area regions of different freshwater content are separated by fronts over the nansen gakkel ridge over the lomonosov ridge and in the western eurasian basin between waters derived from the eurasian and canadian basins denser water homogenized north of the barents sea is recognized by a temperature minimum layer the absence of the temperature minimum near the nansen gakkel ridge indicates that heat is transferred from the atlantic layer over a longer time than the shortest route would allow this observation can be explained if the layer circulates together with the atlantic layer i e toward the east and returns above the nansen gakkel ridge and along the amundsen basin north of the laptev sea this water formed north of the barents sea becomes covered by low salinity shelf water the increased freshwater content limits the winter convection so it no longer reaches the thermocline and an intermediate halocline is formed the halocline in the eurasian basin consists of water originating from winter convection in the arctic ocean north of the barents sea which then circulates around the basin such a formation mechanism also explains the observed distribution of low no water the strong density increase limits vertical exchange and the vertical diffusion coefficient in the halocline is small 1 10 6 m2 s 1 the increased temperature of the halocline shows that the heat lost upward by the atlantic layer mainly by double diffusive convection is trapped below the mixed layer

organic facies development within middle jurassic coal seams danish central graben and evidence for relative sea level control on peat accumulation in a coastal plain environment abstract during middle jurassic times peat accumulated in coastal plain environments in an overall transgressive setting in the sogne basin danish central graben in the north sea the coal seams occur in nonmarine to marginal marine deposits coal petrographic analyses of the seams in the west lulu 2 well supplemented with a sequence stratigraphic analysis suggest that peat accumulation was controlled by relative sea level changes in west lulu 2 the coal bearing upper part of the middle jurassic is divided into sequences a and b the sediments of sequence a are part of a transgressive systems tract whereas the overlying sequence b contains lowstand and transgressive systems tract deposits the coals are situated in the transgressive systems tracts the coal seams formed during a rapid relative sea level rise are generally characterized by petrographic features related to a permanently high groundwater table coals formed during a slow rise typically are drier in their petrographic composition the highest pyrite contents are observed in the wet coals the coal seams represent terrestrial equivalents to marine flooding surfaces or to transgressive surfaces if they are situated at the base of a transgressive systems tract a thick coal seam zone is associated with the stratigraphic level of the maximum flooding surface which correlates with the time of formation of the highest accommodation space

the arctic circumpolar boundary current abstract the main water transformations in the arctic mediterranean take place in the boundary current of atlantic water which crosses the greenland scotland ridge from the north atlantic into the eastern norwegian sea it enters and flows around the arctic ocean before it exits the arctic mediterranean as the east greenland current primarily through denmark strait on route it experiences numerous branchings and mergings by examining how the properties of this circumpolar boundary current evolve it is possible to identify and describe the processes causing the water mass transformations in the arctic mediterranean it is also possible to follow the arctic ocean deep waters as they spread into the nordic seas and eventually provide 40 of the overflow water supplying the north atlantic deep water