analysis of lake ice dynamics and morphology on lake el gygytgyn ne siberia using synthetic aperture radar sar and landsat 1 a time series of more than 450 combined ers 2 radarsat 1 and landsat 7 scenes acquired between 1998 and 2001 was analyzed to develop a fairly complete picture of lake ice dynamics on lake el gygytgyn ne siberia 67 5 n 172 e this 14 km3 lake partially fills a meteorite impact crater formed 3 6 million years ago and is home to a paleoenvironmental coring project the duration of lake ice cover and the onset of lake ice breakup are important both to interpretations of the archived sediment core record and to future drilling projects that will use the ice as a stable platform ice formation snowmelt and ice breakup likely occur in late october mid may and early july respectively these data were used to validate a one dimensional energy balance lake ice model which can now be used to hindcast paleoclimate based on core proxy information synthetic aperture radar sar backscatter from the lake ice also revealed unusual spatial variations in bubble content which were found to indicate the level of biological productivity in the sediments directly beneath the ice with the highest productivity located in the shallowest 0 10 m as well as the deepest 170 175 m regions of the lake seismic data indicates that the backscatter anomaly above the deepest water is collocated with the central peak of the impact crater 500 m below the surface several hypotheses are presented to explain this anomaly regardless of cause the fact that large spatial variations in biological productivity exist in the lake has important implications for selecting the locations of future sediment cores

fine scale hydrodynamics influence the spatio temporal distribution of harbour porpoises at a coastal hotspot the coastal runnelstone reef off southwest cornwall uk is characterised by complex topography and strong tidal flows and is a known high density site for harbour porpoise phocoena phocoena a european protected species using a multidisciplinary dataset including porpoise sightings from a multi year land based survey acoustic doppler current profiling adcp vertical profiling of water properties and high resolution bathymetry we investigate how interactions between tidal flow and topography drive the fine scale porpoise spatio temporal distribution at the site porpoise sightings were distributed non uniformly within the survey area with highest sighting density recorded in areas with steep slopes and moderate depths greater numbers of sightings were recorded during strong westward ebbing tidal flows compared to strong eastward flooding flows and slack water periods adcp and conductivity temperature depth ctd data identified fine scale hydrodynamic features associated with cross reef tidal flows in the sections of the survey area with the highest recorded densities of porpoises we observed layered vertically sheared flows that were susceptible to the generation of turbulence by shear instability additionally the intense oscillatory near surface currents led to hydraulically controlled flow that transitioned from subcritical to supercritical conditions indicating that highly turbulent and energetic hydraulic jumps were generated along the eastern and western slopes of the reef the depression and release of isopycnals in the lee of the reef during cross reef flows revealed that the flow released lee waves during upslope currents at specific phases of the tidal cycle when the highest sighting rates were recorded the results of this unique fine scale field study provide new insights into specific hydrodynamic features produced through tidal forcing that may be important for creating predictable foraging opportunities for porpoises at a local scale information on the functional mechanisms linking porpoise distribution to static and dynamic physical habitat variables is extremely valuable to the monitoring and management of the species within the context of european conservation policies and marine renewable energy infrastructure development

an empirical determination of the minimum number of measurements needed to estimate the mean random vitrinite reflectance of disseminated organic matter abstract in coal samples published recommendations based on statistical methods suggest 100 measurements are needed to estimate the mean random vitrinite reflectance r v r to within 2 our survey of published thermal maturation studies indicates that those using dispersed organic matter dom mostly have an objective of acquiring 50 reflectance measurements this smaller objective size in dom versus that for coal samples poses a statistical contradiction because the standard deviations of dom reflectance distributions are typically larger indicating a greater sample size is needed to accurately estimate r v r in dom however in studies of thermal maturation using dom even 50 measurements can be an unrealistic requirement given the small amount of vitrinite often found in such samples furthermore there is generally a reduced need for assuring precision like that needed for coal applications therefore a key question in thermal maturation studies using dom is how many measurements of r v r are needed to adequately estimate the mean our empirical approach to this problem is to compute the reflectance distribution statistics mean standard deviation skewness and kurtosis in increments of 10 measurements this study compares these intermediate computations of r v r statistics with a final one computed using all measurements for that sample vitrinite reflectance was measured on mudstone and sandstone samples taken from borehole m 25 in the cerro prieto mexico geothermal system which was selected because the rocks have a wide range of thermal maturation and a comparable humic dom with depth the results of this study suggest that after only 20 30 measurements the mean r v r is generally known to within 5 and always to within 12 of the mean r v r calculated using all of the measured particles thus even in the worst case the precision after measuring only 20 30 particles is in good agreement with the general precision of one decimal place recommended for mean r v r measurements on dom the coefficient of variation v standard deviation mean is proposed as a statistic to indicate the reliability of the mean r v r estimates made at n 20 this preliminary study suggests a v v 0 2 suggests an unreliable mean in such small samples

observations of turbulence in a tidal beam and across a coastal ridge during a microstructure survey off california in monterey bay we found a midwater beam of strong turbulence emanating from the shelf break along the ray path of the semidiurnal m2 internal tide within the 50 m thick beam the turbulence kinetic energy dissipation rate e exceeded 10 6 w kg 1 and the diapycnal eddy diffusivity k was 0 01 m2 s 1 the beam extended 4 km off the shelf break several factors suggest that this beam of strong turbulence resulted from the breaking of semidiurnal internal tides the beam appeared to originate from the shelf break which is a potential generation site for semidiurnal internal tides the beam closely followed the ray path of the semidiurnal internal tide the average e off the shelf break varied by a factor of 100 with a semidiurnal tidal periodicity the isopycnal displacement confirmed the presence of semidiurnal internal tides processes associated with the breaking of internal tides are intermittent and sporadic at the same location we also observed equally intense turbulence in a 100 m thick layer of stratified water across the ridge of a sea fan this layer of strong turbulence was separated from the bottom and was clearly not generated by bottom friction although less well resolved in time the strong turbulence above the bottom seemed to vary with the semidiurnal tide and existed at the lee of the ridge where the isopycnal surface dipped and rebounded in a pattern resembling that of internal hydraulic jumps on the basis of the behavior of the density field we believe that the deep mixing was most likely produced by the across ridge current of internal tides the breaking of internal tides at middepth where the richardson number is close to the critical value is likely due to shear instability the presence of the coastal ridge provides an alternative pathway for converting energy from internal tides to turbulence via internal hydraulics multiplying the average e in the midwater beam by the length of the global coastline gives 31 gw only a small fraction of the estimated 360 gw dissipated globally by m2 internal tides our observations suggest that either most internal tides are generated away from shelf breaks or most internal tides generated at shelf breaks propagate away from their generation sites rather than dissipate locally and eventually contribute to pelagic mixing

structural and stratigraphie features and ers 1 synthetic aperture radar backscatter characteristics of ice growing on shallow lakes in nw alaska winter 1991 1992 changes in ers 1 c band synthetic aperture radar sar backscatter intensity from ice growing on shallow tundra lakes at three locations in nw alaska are described ice core analysis shows that at all lakes on the coast at barrow the ice whether floating or frozen to the bottom includes an inclusion free layer overlying a layer of ice with tubular bubbles oriented parallel to the direction of growth the clear ice may also be overlain by a discontinuous layer of bubbly snow ice backscatter is low 16 to 22 db at the time of initial ice formation probably due to the specular nature of the upper and lower ice surfaces causing the radar pulse to be reflected away from the radar as the ice thickens during the autumn backscatter rises steadily once the ice freezes to the lake bottom regardless of the presence of forward scattering tubular bubbles low backscatter values of 17 to 18 db are caused by absorption of the radar signal in the lake bed for ice that remains afloat all winter the ice water interface and the tubular bubbles combine presumably via an incoherent double bounce mechanism to cause maximum backscatter values of the order of 6 to 7 db the saturates at 6 to 7 db before maximum ice thickness and tubular bubble content are attained a simple ice growth model suggests that the layer of ice with tubular bubbles need be only a few centimeters thick midway through the growth season to cause maximum backscatter from floating ice during the spring thaw a previously unreported backscatter reversal is observed on the floating and grounded portions of the coastal lakes but not on the lakes farther inland this reversal may be related to the ice surface topography and wetness plus the effects of a longer cooler melt period by the coast time series of backscatter variations from shallow tundra lakes are a record of 1 the development of tubular bubbles in the ice and by association changes in the gas content of the underlying water and 2 the freezing of ice to the bottoms of the lakes and therefore lake bathymetry and water availability sar is also able to detect the onset of lake ice growth in autumn and the initiation of the spring thaw and thus has potential for monitoring high latitude lake ice growth and decay processes in relation to climate variability

hydraulic control of flow over the sill in observatory inlet observations of density velocity and acoustic backscatter obtained over the sill in observatory inlet british columbia during the ebb tide illustrate several features of internal hydraulic control in a tidally forced stratified flow following high water slack the flow field was initially determined by critical control of the second internal mode at the sill crest as the flow speed increased a transition occurred and control changed to an approach control of the second internal mode located upstream of the sill crest whereas the critical control represents a minimum energy condition at the crest the approach control corresponds to a maximum energy condition upstream of the sill crest later when the ebb currents were just past their maximum values the control condition changed to critical control of the first internal mode the concept of approach control of flow over topography has not previously been discussed in the literature the data described here are believed to represent the first field observations of this phenomenon the changing hydraulic conditions are analyzed in terms of two and three layer hydraulic models model results are consistent with the evolution of the flow patterns although the model cannot reproduce the apparent hysteresis in the response after maximum ebb the concept of an approach control is demonstrated with a simple two layer laboratory model

pore pressure stress coupling in brunei darussalam implications for shale injection shale dykes diapirs and mud volcanoes are common in the onshore and offshore regions of brunei darussalam outcrop examples show that shale has intruded along both faults and tensile fractures conventional models of over pressure induced brittle failure assume that pore pressure and total stresses are independent of one another however data worldwide and from brunei show that changes in pore pressure are coupled with changes in total minimum horizontal stress the pore pressure stress coupling ratio describes the rate of change of minimum horizontal stress magnitude with changing pore pressure minimum horizontal stress measurements for a major offshore field where undepleted pore pressures range from normal to highly overpressured show a pore pressure stress coupling ratio of 0 59 as a consequence of pore pressure stress coupling rocks can sustain a greater increase in pore pressure prior to failure than predicted by the prevailing values of pore pressure and stress pore pressure stress coupling may favour the formation of tensile fractures with increasing pore pressure rather than reactivation of pre existing faults anthropogenically induced tensile fracturing in offshore brunei supports this hypothesis

mixing at camarinal sill in the strait of gibraltar during the gibraltar experiment in 1985 1986 observations of shear stratification microstructure and acoustic backscatter revealed a complex mixing regime at camarinal sill in the strait of gibraltar the mixing is forced by strong semidiurnal tidal currents and weaker but more steady baroclinic flows flows are characterized as outflow or inflow nearly equivalent to westward or eastward rising water at gibraltar coincides with outflow at all depths we observed two modes of outflow at the sill in may 1986 the transition layer separating atlantic and mediterranean water was between 0 75 mpa and 1 mpa when we sampled east of the sill near neap tide the transition turned down just before reaching the sill crest where the flow became critical increasing shear soon destabilized the transition producing billows which grew to 30 75 m on the west flank of the sill the overturning generated intense turbulence with peak dissipation rates e exceeding 10 2 w kg 1 this turbulence rapidly thickened the transition from z 30 50 m east of the sill to z 130 150 m within 1 2 km west of the sill from the rate of thickening we estimate the rate of formation of new transitional water during neap tide as 0 8 1 2 105 m3 s 1 this outflow mode did not release eastward propagating internal bores when outflow turned to inflow but the inflow did appear to arrest the deep outflow in may the largest average dissipation rate over and just west of the sill had the same magnitude as estimates of the net energy lost by adjustment of velocity and mass across the sill during outflow other averages are smaller than the energy loss presumably because the limited sampling severely underestimates the average dissipation rate during outflow strong shears were observed to rise to 100 times those in the background internal wave field however probably owing to spatial offsets between the ship s acoustic doppler current profiler and our tethered free fall profiler the only statistically significant correlations were found between overturning scales measured directly and those estimated from e in the same profile we observed the other outflow mode in october 1985 when we profiled over the sill near spring tide and the transition was east of the sill centered near 1 5 mpa after encountering the sill the transition rose sharply and remained within 10 20 m of the surface across the sill plunging steeply downward just past the west edge of the sill this was accompanied by intense turbulence and at least one rebound of the transition we did not observe release of eastward propagating bores when inflow turned to outflow but observations by armi and farmer 1988 in april 1986 found bores released at spring tide in regimes similar to the one we observed in october 1985

a stacking ensemble learning framework for annual river ice breakup dates abstract river ice breakup dates bds are not merely a proxy indicator of climate variability and change but a direct concern in the management of local ice caused flooding a framework of stacking ensemble learning for annual river ice bds was developed which included two level components member and combining models the member models described the relations between bd and their affecting indicators the combining models linked the predicted bd by each member models with the observed bd especially bayesian regularization back propagation artificial neural network brann and adaptive neuro fuzzy inference systems anfis were employed as both member and combining models the candidate combining models also included the simple average methods sam the input variables for member models were selected by a hybrid filter and wrapper method the performances of these models were examined using the leave one out cross validation as the largest unregulated river in alberta canada with ice jams frequently occurring in the vicinity of fort mcmurray the athabasca river at fort mcmurray was selected as the study area the breakup dates and candidate affecting indicators in 1980 2015 were collected the results showed that the brann member models generally outperformed the anfis member models in terms of better performances and simpler structures the difference between the r and mi rankings of inputs in the optimal member models may imply that the linear correlation based filter method would be feasible to generate a range of candidate inputs for further screening through other wrapper or embedded ivs methods the sam and brann combining models generally outperformed all member models the optimal sam combining model combined two brann member models and improved upon them in terms of average squared errors by 14 6 and 18 1 respectively in this study for the first time the stacking ensemble learning was applied to forecasting of river ice breakup dates which appeared promising for other river ice forecasting problems

observed volume fluxes and mixing in the dardanelles strait 1 pairs of moorings equipped with current profilers were deployed at each end of the dardanelles strait and remained in place for over 13 months current observations were able to resolve well the exchange flow and volume fluxes volume fluxes showed distinct temporal variability in upper and lower layers especially evident on synoptic time scales the synoptic flux variability in the upper layer was coherent with the local atmospheric forcing and the bottom pressure anomaly gradient while the flux variations in the lower layer were related to the bottom pressure anomaly gradient estimated volume flux values were often two or more times larger than their respective annual means annual upper layer flux means were 25 66 10 3 and 36 68 10 3 sv whereas the lower layer averages were 14 02 10 3 and 31 67 10 3 sv for the marmara and aegean sections respectively the fluxes also showed that there was a net low salinity water outflow to the aegean sea and that they varied weakly on longer time scales monthly to seasonal high salinity water fluxes 39 psu were used to calculate strait averaged vertical eddy diffusivities which ranged between 10 4 and 10 2 m2 s 1 additionally microstructure observations were used to evaluate vertical eddy diffusivities these estimates indicated that mixing in the strait varied spatially and temporarily and it was dependent on complex strait geometry exchange flow status and partially on meteorological conditions large values of eddy diffusivities with a depth averaged mean of 1 3 10 2 m2 s 1 and vigorous mixing were found in the nara pass the narrowest section in the dardanelles strait

peculiarities of ice events in russian arctic rivers the state of the art of the hydrological network for the study of river ice regimes in the russian arctic is reviewed as well as the regularly published documents that characterize specific features of ice events the dates of the beginning of different ice events e g ice drift ice cover formation frazil ice drift etc are analysed as well as the duration of such events for 16 rivers typical of the russian arctic it is demonstrated that ice on arctic rivers of asian russia forms earlier and breaks up later compared to those of european russia this is explained by the more severe climate conditions that affect the northern areas of siberia ice cover duration on the study rivers varies from 140 to 250 days with the maximum duration being observed in the lower reaches of large rivers in east siberia and the far east ice cover duration and the latitude of the observation stations are strongly correlated the dynamics of ice cover growth and melting on rivers ice thickness and snow pack depth on the ice are considered in different parts of the russian arctic it is demonstrated that the nature of ice growth during the autumn winter period and its decrease in spring mainly depend on the thermal conditions during a particular year in years with low air temperatures ice cover thickness in the rivers of the far east can attain 200 cm and greater meanwhile it may be 50 or 60 cm only in the rivers of european russia if the winter is warm particular case studies are given to illustrate these features copyright 2002 john wiley sons ltd

spatial and temporal patterns in arctic river ice breakup observed with modis and avhrr time series abstract the timing of spring river ice breakup a major annual event for physical biological and human systems on arctic rivers has been used to infer regional climate variations over the past century or more most observations of ice breakup are recorded as point data taken from selected ground based stations it is unknown whether these point observations are fully representative of breakup patterns elsewhere along the course of a river here daily time series of moderate resolution imaging spectroradiometer modis and advanced very high resolution radiometer avhrr satellite images are used to remotely sense spatial and temporal patterns in ice breakup along 1600 3300 km lengths of the lena ob yenisey and mackenzie rivers the first day of predominantly ice free water is visually identified and mapped for ten years 1992 1993 1995 1998 and 2000 2003 with a mean precision of 1 75 days the derived breakup dates show high correlation with ground based observations although a slight trend towards earlier satellite derived dates can be traced to differences in the way ice breakup date is defined large ice jams are often observed particularly at confluences although smaller ice jams may not be visible due to the limited spatial resolution of the imagery used at the watershed scale spatial patterns in breakup seem to be primarily governed by latitude timing of the spring flood wave and location of confluences with major tributaries interestingly channel scale factors such as slope width and radius of curvature which are known to influence ice breakup at the reach scale do not appear to be major factors at the scale observed here the degree of similarity between interannual trends in breakup date at distant points along a river is generally high which supports the use of point scale data to infer regional climate variations this similarity does not hold true for the mackenzie river where substantial spatial differences in breakup trends are observed a new variable spatially integrated breakup date d i uses weighted spatial averaging to provide a more encompassing measure of breakup timing the ob and yenisey rivers show similar trends in spatially integrated breakup date from year to year in contrast the mackenzie and lena show a remarkably consistent negative correlation here attributed to sea surface temperature anomalies associated with the pacific decadal oscillation index

potassium distribution and metasomatism in pelites and schists how and when relation to postdepositional events a large global database for over 9000 archean to holocene pelites in numerous basins has been developed to evaluate diagenetically unaltered and altered compositions the mineralogy and geochemistry of quaternary muds and ancient mudstones provide first order controls on diagenetic potassium metasomatism in pelites clay mineralogy of quaternary muds is dominated by smectite and kaolinite with minor detrital mica and illite thus k2o is 4 k al is 0 25 and k rb is 220 in most quaternary muds with diagenetic alteration of clays to illite smectite and illite k2o content increases to 4 8 and k al rises to 0 2 0 5 or more in extreme potassium metasomatism authigenic k feldspar develops sources of potassium are internal to shale sandstone units wherein detrital k feldspar is dissolved during diagenesis providing k for clay illitization in closed system isochemical alteration as in some gulf coast and north sea basin cases potassium in amounts greater than that available from closed system alteration is provided from extraformational circulating brines in open system diagenesis k rb with diagenesis varies according to whether the metasomatizing fluid was relatively poor in rb seawater derived brines or richer in rb as in many hydrothermal waters diagenetic fluids may originate from seawater or meteoric water enriched in cations by water rock interactions along their subsurface migration paths and or by dissolution of evaporites potassium metasomatizing fluids penetrate low permeability pelites through faults fractures and microfractures and by diffusion in the mineral matrix typically k metasomatism possibly with pb zn cu ba and f mineralization occurs long after sediment deposition and burial at temperatures of 50 to 150 c related to tectonic activity and fluid movement different modes of metasomatism are recognized and correlated with geological setting in the passive margin gulf coast tertiary basin open system k metasomatism where present is limited to areas adjacent to steeply dipping growth faults which act as conduits for episodic pulses of altering fluids migrated upward from deeper basin sources in contrast widespread pervasive open system k metasomatism produced by continuous long term gravity advective and diffusive flow of brine from the late paleozoic appalachian ouachita wichita mountains highland to altered earlier paleozoic shales plus sandstones bentonites and carbonates in the illinois and anadarko ardmore foreland basins this mode of k alteration following major mountain building events is characteristic of many precambrian and paleozoic collision orogens and associated foreland basins another mode is in rift basins with no external drainage in which indigenous waters are evaporated to brines these brines cause albitization of k feldspar to yield potassium for illitization of detrital clays

the vertical structure of turbulent dissipation in shelf seas abstract the free fall fly profiler has been used to determine the variation in energy dissipation in the water column over a tidal cycle at mixed and stratified sites in the irish sea it was found that exhibits a strong m4 variation with a pronounced phase lag that increases with height above the bed in mixed conditions this m4 signal which extends throughout the water column is reasonably well reproduced by turbulent closure models of the vertical exchange in the summer stratified situation the m4 signal in is confined to about 40 m above the seabed with phase delays of more than 4 h relative to the seabed the lowest levels of dissipation 10 5 w m 3 measured in the pycnocline are significantly above the system noise level and much higher than predicted by a model using the mellor yamada level 2 closure scheme my2 0 however when allowance is made for the diffusion of tke the model my2 2 simulates the depth time distribution of dissipation in the stratified case satisfactorily if

stress on the mediterranean outflow plume part i velocity and water property measurements abstract in september 1988 six sections were occupied across the mediterranean outflow plume in the gulf of cadiz within 100 km of the strait of gibraltar vertical profiles of temperature and salinity were collected at ctd stations velocity and temperature profiles were collected with expendable current profilers at a subset of these stations at the channel base the plume undergoes geostrophic adjustment and turns northwest to flow along the continental slope there it decelerates and spreads gradually down the slope as friction slows the current and allows it to cross isobaths within the plume downstream velocity and density increase rapidly in the interfacial layer with depth to the velocity maximum or nose 5 150 m above the bottom below the nose in the bottom layer downstream velocity decreases rapidly toward the bottom but the stratification is weak ekman like veering occurs in the interfacial layer local bottom stresses on the plume are estimated by fitting the near bottom velocity prof

potential salinity driven free convection in a shale rich sedimentary basin example from the gulf of mexico basin in south texas we investigate the plausibility of salinity driven free thermohaline convection in sedimentary rocks of the south texas part of the gulf of mexico basin using salinity data rayleigh number calculations and numerical models previous studies speculated that free convection could account for high fluxes evidently required for diagenesis in the basin but low permeability shales are calculated to be a barrier to free convection in the study area salinity inversions occur either above or within the transition zone from hydropressures to overpressures the positioning of brines over less saline fluids provides a significant buoyancy force rayleigh number calculations and numerical simulations suggest that homogeneous shaly systems are unstable near the high end of the expected ranges of shale permeability 10 15 10 16 m2 numerical simulations show that the influx of brine into the permeable layers and permeability heterogeneity in the shales are both conducive to free convection simulations indicate that salinity driven free convection can occur at lower permeabilities 10 16 10 18 m2 that may approximate the permeabilities of shales in the zone of extreme overpressures over geologic time simple rayleigh numbers are inadequate to predict the occurrence of free convection in heterogeneous systems salinity driven free convection at depths in some large sedimentary basins such as the gulf of mexico may be more common than expected

analysis of secondary migration of hydrocarbons in the ordovician carbonate reservoirs in the tazhong uplift tarim basin china the process and mechanisms of secondary hydrocarbon migration in the tazhong uplift tarim basin were investigated based on the analysis of the regional structure and by integrating geologic hydrodynamic and geochemical parameters parameters successfully analyzed included the fluid potential fluid properties production outputs and diamantane index the results indicated that hydrocarbons migrated into the tazhong uplift from the northern part of the manjiaer depression through a series of injection points ips during four orogenies that is the early caledonian 510 ma the late caledonian 439 ma the late hercynian indosinian 290 ma and the yanshanian himalayan 208 ma a total of six ips were identified at the intersections of the northeast trending faults and the northwest trending flower strike faults the hydrocarbons migrated from the ips into traps along regional trends from northwest to southeast and from northeast to southwest the hydrocarbon migration process and patterns determined the distribution of hydrocarbon properties and production rates in the tazhong uplift with increasing distance from the ips daily hydrocarbon production decreases and the hydrocarbons become progressively heavier and display lower gas oil ratios

turbulent dissipation over the continental slope off vancouver island abstract thirteen profiles of the rate of viscous dissipation of turbulent kinetic energy epsi were made over the continental slope off vancouver island between 12 and 14 may 1980 in conjunction with ctd and moored current meter observations systematic variability was observed in the vertical but not in the horizontal direction above 200 m depth numerous salt stabilized temperature inversions were seen and dissipation rates were significantly larger than below 200 m dissipation rates below 200 m are the lowest ever reported and coincide with a low level of energetics revealed by the current meter moorings comparison with the garrett munk internal wave spectrum indicates an e folding decay time of internal wave energy of 50 days at depths below 200 m

monitoring river ice with landsat images abstract in the northern united states ice can delay or stop river navigation in the winter and cause unexpected problems and emergencies as part of a program to develop a river ice forecasting model photointerpretation techniques were used to map the areal distributions of four classes of river ice along the navigable reaches of the allegheny monongahela and ohio rivers and the illinois waterway each winter from 1972 to 1985 from landsat multispectral scanner mss band 2 0 6 0 7 m thematic mapper tm band 3 0 63 0 69 m and return beam vidicon rbv 0 580 0 680 m and 0 505 0 750 m images the four classes 1 ice free 2 partial gray ice 3 complete gray ice and 4 white ice were usually readily apparent on the images due to differences in gray tones produced by the various ice types and conditions that make up the different classes landsat derived ice observations compared favorably with available ground and aerial observations 64 80 of the time during mild winters without extensive and long lasting ice or along rivers which normally do not have such ice landsat images are less useful because of the time gaps between cloud or haze free images yet for many rivers in cold regions landsat images may be the only source of data on river ice

integration of space borne and air borne data in monitoring river ice processes in the slave river canada abstract river ice plays an important role in the physical biological and human systems in northern regions due to the large extent and poor accessibility of many river systems remote sensing techniques are a potential tool for collecting information and analyzing characteristics of river ice covers optical data with high temporal resolution e g modis products are suitable for monitoring river ice phenology and mapping river ice cover extent while radar data e g radarsat 2 imagery offer an optimal approach to characterizing river ice thickness ice types and seasonal changes of ice cover characteristics an integrated automated approach utilizing remotely sensed data from both active and passive sensors was developed and applied to characterize river ice processes along the slave river northwest territories canada the results show that the analysis of modis band 2 841 876 nm time series can detect the date of river ice freeze onset fo and water clear of ice wci with a deviation of up to 12 days and 3 days respectively the rate of river ice breakup is much faster than the rate of river freeze up the profiles of modis band 2 reflectance data along the river however showed insignificant differences between different breakup stages and ice types making it challenging to map breakup ice types in this case radarsat 2 imagery can be used successfully to characterize and map four classes of water and ice covers during the breakup period including intact ice smooth rubble ice rough rubble ice and open water in association with hydrometeorological parameters the thermal deterioration of the ice cover during breakup appears to be the primary breakup event in the slave river the results obtained from the analysis of modis and radarsat 2 data were compared with ground measurements of weather flow and ice conditions 2000 2015 time lapse photos and aerial surveys 2013 2015 along the slave river and show strong agreement

dynamics of remotely forced intraseasonal oscillations off the western coast of south america abstract six years of sea level observations at six locations along the south american coast from peru to chile were analyzed at intraseasonal frequencies periodicity 1 2 months a high resolution low frequency numerical coastal model having realistic shelf and slope topography and bottom friction and forced by an equatorial signal was used to analyze the intraseasonal coastal dynamics at these latitudes the following results were obtained lagged correlations between sea level stations imply a sea level poleward propagation of 250 km day 1 the frictionless vertical wall theory poleward phase speed was considerably less at 216 km day 1 model runs with realistic bottom friction and shelf and slope bottom topography gave poleward phase speeds much closer to that observed for typical parameters the phase speed was 253 km day 1 both bottom friction and topography significantly affect the propagation speed past work has shown that the sea level amplitude should grow alongshore like f f coriolis

the pacific decadal oscillation air sea interaction and central north pacific winter atmospheric regimes prominent and persistent anomalies in the atmospheric flow troughs and ridges occur sporadically over the central north pacific and can have profound consequences for the weather of north america we have examined how these events are associated with large scale central north pacific sea surface temperature sst anomalies using an index for the pacific decadal oscillation pdo the anomalies in turbulent air sea heat fluxes and low level baroclinity associated with the pdo are manifested differently during troughs than during ridges in their effects on the transient eddies storms these effects may help explain why prominent troughs ridges occur about 3 2 5 times more frequently during periods when the pdo is significantly positive negative than of opposite sign our results suggest that the state of the mid latitude pacific ocean more fundamentally affects the atmosphere than has been thought

identification of indigenous vitrinites for improved thermal maturity evaluation abstract the four methods that we use to improve the analysis of vitrinite reflectance of well cuttings samples are discussed the criteria for properly identifying the indigenous vitrinites a five fold classification of dispersed vitrinites in sediments first cycle second cycle low gray high gray and gray vitrinites a recording of the reflectance value vitrinite type data for each vitrinite particle analyzed a computer assisted microscope system that generates reflectance histograms of the identified vitrinite type data for easy interpretation using this approach we have minimized inaccuracies caused by the presence of mud additives cavings reworked vitrinites and solid bitumen

delineation of delta ecozones using interferometric sar phase coherence mackenzie river delta n w t canada abstract interferometric processing of six c band synthetic aperture radar sar image pairs for the mackenzie river delta shows that phase coherence is more effective than radar backscatter for differentiating willow alder spruce ice and open water similar radar backscattering from vegetation and wind roughened water surfaces can make such distinctions difficult in sar backscatter images in contrast coherence is preserved over surfaces with rigid scattering elements such as leafless woody alder but is lost over temporally unstable surfaces such as open water we find that willow alder display highest coherence followed by spruce frozen lakes and channels and open water respectively this general hierarchy is preserved even when overall image coherence is decreased by increasing temporal and spatial baselines evaluation of spatial thermal noise and temporal components of total observed coherence indicates that temporal decorrelation is a primary control short temporal baselines such as those obtained during the european remote sensing satellite ers 1 day tandem missions are therefore optimal for obtaining maximum differentiation of surface classes

advances in river ice hydrology river ice is present in nearly all canadian rivers for periods ranging from days to many months whether moving or stationary it interacts with the river flow in various ways resulting in multiple impacts on the economy and ecosystem and posing a major flood threat to riverside communities in the past 4 years canadian research and development efforts have been directed at a variety of problems a strong focus on ice breakup and ice jam processes resulted in improved understanding of the salient geomorphological and hydroclimatic factors enhanced modelling and prediction capabilities and development of techniques for in situ measurement of ice jam properties key contributions in the area of ecological impacts of river ice and ice jams have led not only to solid advances in knowledge but also to an appreciation of the vast scope of this subject and its numerous links to environmental science a closely related topic the flux of suspended sediment in ice laden rivers was studied for the first time in order to delineate the effects of the ice on sediment and associated contaminant loads in response to growing concern about climate change and variability several studies addressed implications to ice regime and thence to ecology and economy although not fully explored the potential impacts appear to be numerous and significant owing to the high sensitivity of river ice processes to climatic factors in the foreseeable future research is likely to continue along the above noted lines although an increased emphasis on climatic and ecological aspects is probable insights gained on the mechanisms of breakup and jamming may lead to increased modelling applications and testing of theoretical concepts

episodic migration of natural gas a worldwide phenomenon of dynamic filling of oil and gas fields natural gases form through bacterial and thermogenic conversion of organic matter over extended geological time the isotopic properties of methane and c2 hydrocarbons are controlled by temperature dependent kinetic fractionation during maturation and mixing during migration and in reservoirs gas fields which are actively and repeatedly charged over extended periods of gas formation will receive compositionally and isotopically variable charges of natural gases that can mix in different proportions in single reservoirs episodic migration and multiple filling of reservoirs is a ubiquitous phenomenon observed in small and giant gas fields throughout the world the following case histories from own research and from the literature will be discussed to illustrate this phenomenon gulf of mexico pervasive mixing of bacterial and thermogenic gas charges results in large variations in isotopic signatures on a field and reservoir scale major formation and migration episodes are 1 bacterial gases form in rapidly subsiding mini basins and migrate and accumulate around rising sell structures and active growth faults and 2 following multiple charges of thermogenic gases mix in various proportions with bacterial gases angola giant oil fields off shore cabinda contain thermogenic gases with different isotopic signatures in the gas cap and the oil leg indicating a multimore phase migration of thermogenic gases from mature to post mature sources the gas oil columns are in some cases variable and suggest compartmentalization and or unmixed oil hydrocarbon columns yacheng gas field gas composition and isotopic signatures of methane change from west to east in this giant field in the s china sea inert gas contents also vary vertically in the reservoir suggesting a late charge of a co sub 2 rich gas into the structure south ltaly pliocene reservoirs in the apulian basin are mixtures of thermogenic and bacterial gases less

ice floe tracker an algorithm to automatically retrieve lagrangian trajectories via feature matching from moderate resolution visual imagery abstract satellite observations of sea ice along marginal ice zones suggest a strong coupling between sea ice transport and the underlying ocean turbulent eddy field moderate resolution imaging spectroradiometer modis satellite imagery spanning over almost two decades of daily observations at a resolution of up to 250 m provides a good resource for deriving long term ocean kinematics from sea ice dynamics in this paper we present a newly developed automatic algorithm to retrieve dynamic measurements of sea ice from these images we describe the methodology by presenting results acquired along the east greenland current ecg for 6 5 weeks in the spring of 2017 during this period our ice floe tracker was used to identify and track ice floes with length scales ranging from 8 to 65 km by effectively filtering atmospheric conditions from modis images ice floes were tracked for up to ten consecutive days and a total of 1061 trajectories were retrieved a southward mean sea ice flow associated with the ecg was observed along with deviations in both direction and magnitude suggesting the effect of an underlying turbulent eddy field the absolute position and tracking errors associated with our method are 255 m and 0 65 cm s respectively each derived from a comparison between manually and automatically identified ice floes going forward our methodology will be employed to process longer time sequences to analyze nonlinear interactions between drifting ice floes and the upper ocean turbulent eddy field in the ecg as well as to investigate other prominent regions of the arctic ocean

lateral dispersion over the continental shelf analysis of dye release experiments lateral dispersion over the continental shelf was examined using dye studies performed as a part of the coastal mixing and optics experiment four experiments performed at intermediate depths each lasting 2 5 5 days were examined in some cases the dye patches remained fairly homogeneous both vertically and horizontally throughout an experiment in other cases significant patchiness was observed on scales ranging from 2 to 10 m vertically and a few hundred meters to a few kilometers horizontally the observations showed that the dye distributions were significantly influenced by shearing and straining on scales of 5 10 m in the vertical and 1 10 km in the horizontal superimposed on these larger scale distortions were simultaneous increases in the horizontal second moments of the dye patches with corresponding horizontal diffusivities based on a fickian diffusion model of 0 3 4 9 m 2 s 1 analysis of the dye data in concert with shear estimates from shipboard acoustic doppler current profiler observations showed that the existing paradigms of shear dispersion and dispersion by interleaving water masses cannot account for the observed diffusive spreading of the dye patches this result suggests that some other mechanisms provided an additional diffusivity of order 0 2 4 6 m 2 s 1 an alternative mechanism dispersion by vortical motions caused by the relaxation of diapycnal mixing events may explain the observed dispersion in some cases

the influence of oxygen isotope exchange between co2 and h2o in natural co2 rich spring waters implications for geothermometry abstract oxygen isotope ratio 18o value deviations from the meteoric water line with no significant change in the hydrogen isotope 2h composition have been reported in naturally occurring co2 rich waters from around the world here we review the effects of oxygen isotope exchange with co2 high temperature equilibration with bedrock minerals and mineral dissolution and precipitation reactions on the co2 rich water isotopic composition we present two case studies from daylesford australia and pah tempe utah usa mineral springs where we use a numerical geochemical modelling approach to resolve the influence of low temperature water rock interactions and co2 equilibration to the oxygen isotope ranges observed in the mineral waters in both cases we find that mineral dissolution precipitation reactions are unlikely to have a significant effect on the groundwater isotopic compositions and that the observed 18o values in natural co2 springs can be simply explained by equilibrium fractionation between water and free phase co2 traditionally the interaction of co2 and water in a natural co2 rich groundwater setting has only been associated with water 18o depletion and this is the first study to consider 18o enrichment we establish that in a natural setting co2 and water equilibration can result in water 18o depletion or enrichment and that the change in the oxygen isotope composition ultimately depends on the initial co2 and water 18o values our new conceptual model therefore provides a mechanism to explain water 18o enrichment at ambient temperatures this finding is critical for the use of 18o in groundwater geothermometry and for the interpretation of natural water circulation depths we argue that in some cases natural waters previously interpreted as geothermal based on their oxygen isotope composition may actually have acquired their isotopic signature through interaction with co2 at ambient temperatures

topographically induced drag and mixing at a small bank on the continental shelf recent turbulence measurements over a small bank on the continental shelf off oregon reveal a previously undetected site for intense mixing of the coastal ocean the flow is hydraulically controlled and turbulence diffusivities over the bank are more than 100 times greater than estimates made on the shelf away from topography the total drag exerted by the bank on the flow field is a combination of bottom friction plus form drag analogous to mountain drag and is comparable to the coriolis force this drag is sufficient to decelerate the flow over the bank in a matter of hours

the physical oceanography of jones bank a mixing hotspot in the celtic sea abstract new measurements are presented of the currents and hydrography at jones bank in the celtic sea these measurements collected during the summer of 2008 identify a highly energetic internal wavefield generated by the local interaction of seasonally stratified flow with topography observations close to the bank crest reveal internal waves of up to 40 m amplitude approaching 50 of the local water depth these waves occur during spring periods and are predominantly associated with off bank tidal flow we provide evidence that these waves are the result of hydraulic control of the tidal currents which result in supercritical flow in the bottom mixed layer bml on the upper slopes of the bank the waning tide produces a transition from super to subcritical flow identifiable as a regular hydraulic jump on the bank slope microstructure measurements identify a turbulent bore associated with such jumps that increases bml turbulence by several orders of magnitude and produces a regular burst of enhanced mixing at the base of the ever present thermocline additional mixing in the surface mixed layer is provided during gale force conditions during the first of the two spring tides observed occurring at the start of our three week measurement period the average thermocline mixing rate during stormy spring tide conditions is 1 9 1 0 95 10 3 m 2 s 1 driven by both surface mixing and hydraulic jumps during the later calm spring period the average thermocline mixing rate is 3 3 1 7 10 4 m 2 s 1 dominated by jump associated events by comparison the intervening neap tide period produces no hydraulic jumps and is characterised by relatively calm weather a strong shear layer is however maintained during this quiet period sufficient to enhance thermocline turbulence by a factor 1000 above background levels a short lived peak in thermocline turbulence during the neap period produces diapycnal mixing as high as 1 6 10 2 m 2 s 1 however a more representative background thermocline mixing rate is 2 8 0 6 10 5 m 2 s 1

geophysics a moving fluid pulse in a fault zone evidence from the south eugene island block 330 oil and gas field in the gulf of mexico off louisiana suggests that the fault zones there have acted as conduits for fluids rising from deep in the earth s crust and now one of these fault burps has been observed directly seismic reflection imaging revealed the rapid ascent of a pulse of fluid rising vertically up the fault by 1 km between 1985 and 1992 burps like this may be important factors in subsurface hydrocarbon migration in the gulf of mexico fault zones are linked with a complex and dynamic system of plumbing in the earth s subsurface here we use time lapse seismic reflection imaging to reveal a pulse of fluid ascending rapidly inside one of these fault zones such intermittent fault burping is likely to be an important factor in the migration of subsurface hydrocarbons

hockley fault revisited more geophysical data and new evidence on the fault location houston texasgeophysics of the hockley fault texas continuing sediment deposition and related deformation in the gulf of mexico cause faulting in coastal areas these faults are aseismic and underlie much of the gulf coast area including the city of houston in harris county texas considering the average movement of these faults is 8 cm per decade in harris county the potential is high for structural damage to highways industrial buildings residential houses that cross these features using integrated geophysical data we have investigated the hockley fault which is located in the northwest part of harris county across highway 290 our magnetic gravity conductivity and resistivity data displayed a fault anomaly whose location is consistent with the southern portion of the fault mapped by previous researchers at the precisely same location gravity data indicate a significant fault signature coincident with the magnetics and conductivity where high gravity values are observed in the downthrown section farther north across highway 290 the resist

internal hydraulic jumps in a long narrow lake high resolution three dimensional numerical modeling and field observations were used to describe the nonlinear response of cayuga lake to surface wind forcing the degeneration of the basin scale internal wave field was characterized according to the composite froude number g2 wedderburn number wn and lake number ln which are measures of hydraulic control and bulk and integral wind disturbance force to the baroclinic restoring force respectively the typical cayuga lake response was a nonlinear surge when 1 1 in a lake the occurrence of the hydraulic jump was correctly predicted using scaling parameters it was also shown that topographically induced internal hydraulic jumps form when the nonlinear surges interact with a sill contraction topographic feature in contrast to published literature the observed high frequency nonlinear internal waves were preferentially associated with internal jumps as opposed to steepened internal surges computed vertical diffusivities showed mixing was enhanced by two orders of magnitude within both the surges and hydraulic jumps as they propagated through the basin and interacted with topography our results can be generalized to other lakes and fjords with similar long narrow geometry and topographically separate side basins

relation between permeability and effective stress along a plate boundary fault barbados accretionary complex in situ bulk permeability was measured in a borehole that intersected the decollement zone a low angle detachment fault between the north american and caribbean plates permeability measurements were made at a variety of fluid pressure conditions defining a quantitative relation between bulk permeability and effective stress for this plate boundary fault zone the bulk permeability in this zone changed by several orders of magnitude as a consistent function of fluid pressure this relation may help to explain the dynamics of fluid fault interactions and the transient nature of hydrologic processes during deformation at convergent margins

bottom stress estimates from vertical dissipation rate profiles on the continental shelf abstract measurements of the near bottom distribution of the turbulent dissipation rate on the continental shelf west of vancouver island are used to calculate bottom stress a free failing vertical profiler with microstructure shear probes was used to measure the dissipation rate from near the surface to within 0 15 m of the bottom the shear probes measure velocity gradients at scales within the viscous subrange of the turbulence and therefore directly measure the rate at which kinetic energy is dissipated by viscosity friction velocities are computed from the formula uast z where the dissipation rate is measured in the constant stress layer the technique is more reliable than estimates of the dissipation rate obtained by fitting spectral slopes to velocity spectra at scales in the inertial subrange near bottom current measurements indicate that the bottom stress values obtained from the turbulent measurements are well correlated with the current magnitude an estimate of the drag coeff

the generation and trapping of solitary waves over topography observations of tidal flow over a sill show that upstream solitary wave generation occurred in conjunction with the downstream movement of a streamline bifurcation over the obstacle crest solitary waves appeared upstream of the bifurcation riding on the surface stratification shear flow instabilities on the plunging interface were also evident and may contribute to wave generation through subharmonic interaction nonlinear waves generated downstream of an internal control became trapped in the supercritical flow

historical trends in lake and river ice cover in the northern hemisphere freeze and breakup dates of ice on lakes and rivers provide consistent evidence of later freezing and earlier breakup around the northern hemisphere from 1846 to 1995 over these 150 years changes in freeze dates averaged 5 8 days per 100 years later and changes in breakup dates averaged 6 5 days per 100 years earlier these translate to increasing air temperatures of about 1 2 c per 100 years interannual variability in both freeze and breakup dates has increased since 1950 a few longer time series reveal reduced ice cover a warming trend beginning as early as the 16th century with increasing rates of change after about 1850

tidally driven vorticity diurnal shear and turbulence atop fieberling seamount abstract fine and microstructure profiles collected over fieberling seamount at 32 26 n in the eastern north pacific reveal a variety of intensified baroclinic motions driven by astronomical diurnal tides the forced response consists of three phenomena coexisting in a layer 200 m thick above the summit plain i an anticyclonic vortex cap of core relative vorticity 0 5f ii diurnal fluctuations of 15 cm s 1 amplitude and 200 m vertical wavelength and iii turbulence levels corresponding to an eddy diffusivity e 10 10 4 m2 s 1 the vortex cannot be explained by taylor proudman dynamics because of its 0 3fn2 negative potential vorticity anomaly the 0 3f fortnightly cycle in the vortex s strength suggests that it is at least partially maintained against dissipative erosion by tidal rectification the diurnal motions are slightly subinertial turning clockwise in time and counterclockwise with depth over the summit plain they also exhibit a fortnightly cycle in their amplitude pointing to

evaluation of geological factors in characterizing fault connectivity during hydrocarbon migration application to the bohai bay basin faults play an intricate role in hydrocarbon migration and accumulation since they can serve either as a conduit or a seal quantitative evaluation of fault opening sealing properties requires the selection of valid and optimal parameters among numerous geological factors to characterize the hydraulic behaviors of faults the present study focuses on the chengbei step fault area in the qikou depression bohai bay basin ne china because hydrocarbon migration and accumulation in this area occurred in a relatively short period so that accumulated hydrocarbons can be used as an indicator to deduce hydraulic connectivity of a fault zone between two sites various geological parameters pertinent to a fault such as burial depth dip angle throw strike percentage of sandstone of faulted intervals fluid pressure in faulted mudstone stress normal to the fault plane and shale gouge ratio are analyzed to assess their effectiveness in characterizing fault connectivity an index the fault connectivity probability np is proposed to evaluate the possibility that a fault has been once serving as a migration pathway the statistical relationship between np and any a geological parameter may be used to indicate the effectiveness of this parameter in characterizing the connectivity of a fault during hydrocarbon migration the correlation coefficient of a relationship is a good indicator of the effectiveness and the results are generally in agreement with qualitative assessments parameters representing a single geological factor are generally ineffective whereas those representing implicitly or explicitly two or more factors such as shale gouge ratio stress normal to the fault plane and fault opening index are more effective

effect of stair step and piecewise linear topography on internal wave propagation in a geophysical flow model 1 the paper describes the effect of a stair step representation of bottom topography common in most numerical models on the propagation of internal waves in a geophysical flow an analytical solution was used to predict the effect of stair step and piecewise linear representations of topography on the reflection and transmission of internal waves the estuary lake and coastal model elcom was used to simulate the transmission of a train of small amplitude internal gravity waves propagated along a variable depth rectangular channel containing a linearly stratified fluid the effect of the different obstacle approximations was examined in terms of the interference of the resulting wave number content and hence the associated reflection coefficients which could be directly compared to the analytical theory it was shown that for gaussian obstacles of varying lengths and heights the full bottom cells and partial bottom cells solutions from elcom agree with the stair step and piecewise linear solutions from the theory respectively it was shown that when gaussian obstacles with weak slopes are represented by stair steps an aliasing that is similar to that in discrete fourier transform can occur resulting in reflection coefficients that are much higher than the exact solution on the other hand piecewise linear approximations produce significantly attenuated aliasing an immersed boundary technique that enforces a no flux condition at the actual sloping bottom similar to that of the analytical solution is found not to produce better numerical results

fluid flow in the south eugene island area offshore louisiana results of numerical simulations abstract numerical simulations of heat and fluid transport in the south eugene island sei area offshore louisiana suggest fluids migrate from deep abnormally pressured sediments along fault zones and into overlying oil and gas reservoirs in the simulations fluid flow along the fault produces a narrow thermal anomaly around the fault a negative thermal anomaly forms adjacent to the thermal maximum when permeable sediments dip away from the fault zone in the simulations this negative thermal anomaly dissipates 100 200 years after it forms the presence of a similar negative thermal anomaly in the sei area suggests that fluid movement in the area is a recent event the observation that the thermal maximum in the study area is not centered about the fault zone further suggests that the primary vertical conduit for fluid flow in the sei area is not a major fault but minor splay faults in the hanging wall

coastal upwelling in the california current system abstract coastal upwelling in the california current system has been the subject of large scale studies off california and baja california and of small scale studies off oregon recent studies of the winds along the entire coast from 25 n to 50 n indicate that there are significant along shore variations in the strength of coastal upwelling which are reflected in the observed temperature distribution active upwelling appears to be restricted to a narrow coastal band about 10 25 km wide along the entire coast but the region influenced by coastal upwelling may be much wider intensive observations of the upwelling zone during summer off oregon show the presence of a southward coastal jet at the surface a mean vertical shear a poleward undercurrent along the bottom and persistently sloping isopycnals over the continental shelf most of the upwelling there occurs during relatively short periods several days long of upwelling favorable winds during the upwelling season off oregon the offshore ekman transport is carried by the surface ekman layer and the onshore return flow occurs through a quasi geostrophic interior it is not known whether the structure and dynamics observed off oregon are typical of the upwelling zone along the entire coast though some of the same features have been observed off baja california current and future research will eventually show whether the oregon results are also applicable in the region of persistently strong upwelling favorable winds off northern california and in the region of complex bathymetry off central and southern california

internal hydraulic flows on the continental shelf high drag states over a small bank observations of currents hydrography and turbulence provide unambiguous evidence for hydraulic control of flow over an isolated three dimensional topographic feature on oregon s continental shelf the flow becomes critical at the crest of the bank forming a strong supercritical downslope flow in the lower layer farther downstream internal hydraulic jumps form as the bottom flow becomes subcritical as a consequence turbulence is greatly enhanced in the bottom boundary layer in the sheared interface above the swiftly flowing bottom current and in the internal hydraulic jump the dissipation rate of turbulent energy is consistent with the mean energy removal rate for a hydraulic jump in an idealized two layer flow this enhanced turbulence constitutes a high drag state of the flow in which the form drag introduced by the topography exerts significant influence on the flow around it and mixing is increased 102 103 times the background values

evaluation of solitary waves as a mechanism for oil transport in poroelastic media a case study of the south eugene island field gulf of mexico basin abstract hydrocarbons in shallow reservoirs of the eugene island 330 field in the gulf of mexico basin are thought to have migrated rapidly along low permeability sediments of the red fault zone as discrete pressure pulses from source rocks at depths of about 4 5 km the aim of this research was to evaluate the hypothesis that these pressure pulses represent solitary waves by investigating the mechanics of solitary wave formation and motion and wave oil transport capability a two dimensional numerical model of eugene island minibasin formation predicted overpressures at the hydrocarbon source depth to increase at an average rate of 30 pa yr reaching 52 mpa by the present day and oil velocities of 10 12 m yr far too low for kilometer scale oil transport to fill shallow plio pleistocene reservoirs within the 3 6 million year minibasin history calculations from a separate one dimensional model that used the pressure generation rate from the two dimensional model showed that solitary waves could only form and migrate within sediments that have very low permeabilities between 10 25 and 10 24 m 2 and that are highly overpressured to 91 93 of lithostatic pressure solitary waves were found to have a maximum pore volume of 10 5 m 3 to travel a maximum distance of 1 2 km and to have a maximum velocity of 10 3 m yr based on these results solitary waves are unlikely to have transported oil to the shallowest reservoirs in the eugene island field in a poroelastic fault gouge rheology at the pressure generation rates likely to have been caused by disequilibrium compaction and hydrocarbon generation however solitary waves could perhaps be important agents for oil transport in other locations where reservoirs are closer to the source rocks where the pore space is occupied by more than one fluid or where sudden fracturing of overpressured hydrocarbon source sediments would allow the solitary waves to propagate as shock waves

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

topographically induced mixing around a shallow seamount measurements of the rate of dissipation of kinetic energy around a shallow seamount in the eastern north pacific show that mixing there is 100 to 10 000 times as large as that far away from the seamount if such values are typical of other seamounts mixing across density surfaces in the ocean occurs mainly at their boundaries and topographically induced mixing may help to explain the discrepancy between the observed intensity of mixing in the interior of the oceans and that required to satisfy models of ocean circulation

automating conceptual models to easily assess trap integrity and oil preservation risks associated with fault reactivation abstract extensive neogene fault reactivation and leakage in the timor sea australian north west shelf has long been identified as the likely cause for traps in the region being dry or underfilled despite widespread evidence for hydrocarbon charge and larger palaeo hydrocarbon columns than those preserved today a structural model has been previously proposed gartrell et al 2005 to explain the distribution of palaeo and live hydrocarbon columns this basic geometrical model is used to define the volume of closure that is protected from fault reactivation thereby providing the potential for preserving hydrocarbons although the model is retrospectively successful in identifying which traps contain hydrocarbons application to other areas is subjective to assess the application of the gartrell et al 2005 concept a computational model has been generated and applied to a regional 3250 km 2 seismic interpretation allowing sensitivity testing of the critical input parameters the automation has allowed us to demonstrate that the model successfully identifies dry traps and derives reasonable approximations of hydrocarbon water contacts in commercial accumulations therefore the basic geometrical model is deemed valid to apply to other hydrocarbon provinces both frontier and mature that are adversely impacted by fault reactivation after hydrocarbon charge

observations of turbulence caused by a combination of tides and mean baroclinic flow over a fjord sill thisstudyinvestigates thedissipation ratesandflow conditionsatthedrobaksillinthe oslofjord thearea was transected 13 times with a free falling microstructure shear probe during 4 days in june 2011 at the same time an adcp was deployed inside the sill during most tidal cycles internal hydraulic jumps with high dissipation rates were foundon the downstreamside of the sill however the internal responsevariedstrongly betweendifferenttidal cycleswith similar barotropicforcing in the beginning of the observational period ebb tides had no hydraulic jumps and in the end one of the flood tides did not have a hydraulic jump during the same period the mean baroclinic exchange flow changed from inflow to outflow in the bottom layer the authors conclude that the conditions at the sill are on the edge of forming hydraulic jumps and that the mean baroclinic exchange may push the flow above or below the limit of a hydraulic jump depending on the situation this conclusion is supported by two layer hydraulic theory the volume integrated dissipation rates within 500m from the sill crest compare well with estimates of energy loss in the lower layer calculated from the bernoulli drop under the assumption of no energy loss in the upper layer finally the mean dissipation rateatthesillwascomparedwiththeradiationofinternaltidalenergyawayfromthesill anditwasfoundthat about 60 90 of the total energy loss was dissipated locally

stress on the mediterranean outflow plume part ii turbulent dissipation and shear measurements abstract bottom and interfacial stresses on the mediterranean outflow plume are estimated using vertical profiles of turbulent dissipation and velocity collected in the gulf of cadiz turbulent dissipation is high throughout the plume with a local minimum often present near the plume nose depth of maximum downstream velocity bottom stresses are estimated by applying a log layer model to the dissipation measurements the dissipation measurements are also divided by plume scale vertical shear from the horizontal velocity profiles to construct profiles of stress within the plume the mean stress estimates in the bottom layer agree well with those calculated in the log layer from the dissipation measurements alone the bottom layer means are slightly larger than those of the interfacial layer the maximum stresses in each layer are uncertain since they depend on the ill defined shape of the stress profiles within the plume dissipation derived stress estimates in the log layer and those from dissipation

kilometer scale upward migration of hydrocarbons in geopressured sediments by buoyancy driven propagation of methane filled fractures several lines of evidence support kilometer scale upward migration of fluids in the gulf of mexico basin discharge of hypersaline brines at the sea floor long term natural hydrocarbon seeps and microseeps gas chimneys lead zinc mineralization in salt dome cap rocks and allochthonous brines in cenozoic sediments we explore the hypothesis that upward fluid transport in geopressured sediments is caused by buoyancy driven propagation of isolated methane filled fractures in other words instead of fluid migrating along a fixed network of interconnected pores or fractures fluid enclosed within an isolated fracture is transported upward by hydrofracturing the mechanically weak geopressured sediments thus the fluid filled fracture propagates upward through the sediments hydrofracture is driven by the pressure difference buoyancy between the enclosed methane and the surrounding sediments our results show that methane filled fractures with half lengths of a few meters should propagate upward through geopressured sediments with velocities of hundreds of meters per year or higher as methane filled fractures increase in volume and decrease in density with decreasing confining pressure they develop the potential to entrain and transport more than 1000 kg m3 of oil or brine methane filled fractures should propagate to the surface unless they are trapped beneath a layer that has high fracture toughness such as salt or are absorbed when they intersect a permeable 10 md sand layer

a model for shear response in swimming plankton abstract observations of zooplankton populations below their preferred light level have been attributed to a shear response we propose a measure of shear based on the second invariant of the rate of strain tensor this quantification allows the shear response mechanism to be modelled numerically the importance of this mechanism is examined by modifying a light biased stochastic swimming model of the run and tumble type for plankton moving in a velocity field induced by internal waves in a channel it is found that a model which includes the mechanisms of settling biased swimming and a freeze in shear response predicts aggregation of plankton populations below their preferred light level which is consistent with acoustic data observations depending on the geometry of the high shear region the population is either shifted downward or aggregates as a thin layer along the bottom boundary of the high shear region a pair of timescales is defined in order to determine which of these two cases will occur

estimation of river discharge propagation speed and hydraulic geometry from space lena river siberia 1 moderate resolution imaging spectroradiometer modis derived measurements of lena river effective width we display a high predictive capacity r2 0 81 mean absolute error 60 90 km 2 3 time valley width satellite derived we q rating curves and hydraulic geometry b exponents converge upon stable values b 0 48 indicating transferability of the discharge retrieval method between different locations put another way at length scales exceeding 60 90 km all subreaches display similar behavior everywhere at finer reach length scales e g 0 25 1 km longitudinal extraction of b exponents represents the first continuous mapping of a classical hydraulic geometry parameter from space while at least one gauging station is required for calibration results suggest that multitemporal satellite data can powerfully enhance our understanding of water discharge and flow conveyance in remote river systems

vertical and lateral fluid flow related to a large growth fault south eugene island block 330 field offshore louisiana data from sediments in and near a large growth fault adjacent to the giant south eugene island block 330 field offshore louisiana indicate that the fault has acted as a conduit for fluids whose flux has varied in space and time core and cuttings samples from two wells that penetrated the same fault about 300 m apart show markedly different thermal histories and evidence for mass flux sediments within and adjacent to the fault zone in the u s department of energy pennzoil pathfinder well at about 2200 m sstvd subsea true vertical depth showed little paleothermal or geochemical evidence for throughgoing fluid flow the sediments were characterized by low vitrinite reflectances ro averaging 0 3 ro moderate to high d18o and d13c values and little difference in major or trace element composition between deformed and undeformed sediments in contrast faulted sediments from the a6st well which intersects the a fault at 1993 m sstvd show evidence for a paleothermal anomaly 0 55 ro and depleted d18o and d13c values sodium is depleted and calcium is enriched in a mudstone gouge zone at the top of the fault cut in the well this effect diminishes with distance from this gouge zone cuttings from other wells in south eugene island block 330 show slightly elevated vitrinite reflectance in fault intercepts relative to sediments outside the fault zone overall indicators of mass and heat flux indicate the main growth fault zone in south eugene island block 330 has acted as a conduit for ascending fluids although the cumulative fluxes vary along strike this conclusion is corroborated by oil and gas distribution in downthrown sands in blocks 330 and 331 which identify the fault system in northwestern block 330 as a major feeder simple modeling of coupled heat and mass flux indicates the paleothermal anomaly in the fault zone intersected by a6st well was short lived having a duration less than 150 yr the anomaly could have been produced by a 2 106 m3 pulse of fluid ascending the fault at an actual velocity of over 1 km yr darcy flux of 330 m yr from 3 km deeper in the basin simple darcy law computation indicates a transient fault permeability on the order of 110 md during this flow pulsing of fluid up the fault was probably the norm although most flow did not produce such strong thermal anomalies as the one detected in the a6st well analysis of fluid pressures shows that the main fault is a profound lateral permeability barrier having up to 1800 psi of water pressure differential across it the hydrocarbon sealing capacity of the fault depends on the pressure difference across the fault fault permeability is best understood in terms of effective stress under ambient conditions the fault is at high pressure relative to downthrown reservoirs a pulse of high pressure fluid ascending end page 244 the fault lowers effective stress in the fault zone sufficiently to produce a significant transient increase in permeability if the fluid is in an area of the fault adjacent to downthrown relatively low pressure reservoir sands the fluid will discharge into them permeability in and adjacent to the fault then decreases such that fluid cannot reenter the fault zone and escape from the reservoir

stratified tidal flow over a bump the interaction of a stratified flow with an isolated topographic feature can introduce numerous disturbances into the flow including turbulent wakes internal waves and eddies measurements made near a bump east of race rocks vancouver island reveal a wide range of phenomena associated with the variable flow speeds and directions introduced by the local tides upstream and downstream flows were observed by placing two acoustic doppler current profilers adcps on one flank of the bump simultaneous shipboard adcp surveys corroborated some of the more striking features froude number conditions varied from subcritical to supercritical as the tidal velocities varied from 0 2 to 1 5 m s 1 during the strong ebb when the moored adcps were located on the lee side a persistent full water depth lee wave was detected in one of the moored adcps and the shipboard adcp however the placement of the moorings would suggest that by the time it appears in the moored adcp beams the lee wave has been swept downstream or has separated from the bump raw adcp beam velocities suggest enhanced turbulence during various phases of the tide many of the three dimensional flow characteristics are in good agreement with laboratory studies and some characteristics such as shear in the bottom boundary layer are not

reservoir fluids and their migration into the south eugene island block 330 reservoirs offshore louisiana this study in the well documented pliocene pleistocene south eugene island block 330 sei330 field offshore louisiana unravels a complex petroleum system by evaluating both the inorganic and organic geochemical characteristics of reservoir fluids the brines at sei330 dissolved halite prior to entering the reservoirs and equilibrated with reservoir sediments exchanging sodium for calcium magnesium and other cations the systematically varying extent of brine sodium depletion in two reservoirs defines south to north flow in those sands these sands were filled from a fault that bounds the reservoirs on the south oil compositional parameters also show north south variation across these reservoirs the sei330 oils and gases each had different sources in contrast to published jurassic sources for oil carbon isotope data indicate that sei330 hydrocarbon gases probably sourced from early tertiary or cretaceous sediments after oil had migrated through them distribution of biodegraded vs unbiodegraded oils indicates the reservoirs filled much more recently than formation of the salt weld beneath the field oil compositions indicate that some sei330 oils were partially stripped of low molecular weight compounds by their dissolution in a mobile vapor phase gas washed by large volumes of gas several hundred meters below the deepest reservoir modeling of this gas oil interaction aids in identifying deep potential targets in which gas washing occurred hydrocarbon distribution combined with oil chemistry and reservoir pressures indicate reservoirs filled from fault systems on both the north and south sides of the field the fault feeders are wide 100 m structurally complex zones that can direct different types of fluids into different reservoirs

control on sediment and organic carbon delivery to the arctic ocean revealed with space borne synthetic aperture radar ob river siberia an important control on river biogeochemistry and sediment load is the process of water exchange between primary channels and the flood plain particularly in low r elief areas containing lakes ephemeral channels and other aquatic ecosystems flood plain exchange may be a dominant process on the lowland rivers of arctic russia which are among the world s largest in water discharge yet are strikingly deficient in their delivery of sediment to the arctic shelf temporal synthetic aperture radar sar amplitude and interferometric images of the ob river siberia reveal a time varying limnological network controlling water sediment and nutrient exchange between flood plain wetlands and the main channel the amount of hydrologic exchange decreases by one order of magnitude from june to september enhancing sedimentation over as much as 90 of the flood plain and enriching channel waters with colloidal organic carbon this observation combined with russian field measurements of water discharge and sediment load indicates that a major sediment sink on the lower ob flood plain may be responsible for the low amount of sediment delivery by the ob river to its estuary and the kara sea

near boundary mixing above the flanks of a midlatitude seamount fine scale velocity and density profile data with concurrent turbulent velocity and temperature dissipation estimates obtained above the flanks of fieberling guyot a seamount in the eastern north pacific ocean are examined for evidence of near bottom boundary mixing fine scale shear and strain spectral levels were elevated over the flanks of the seamount in a 500 m thick stratified layer above the bottom the velocity shear was horizontally isotropic clockwise and counterclockwise with depth shear spectral levels were comparable and no significant correlation between shear and strain was observed above the steepest bottom slopes near the seamount summit rim excess vertical strain relative to shear was observed as compared to the background internal wave field suggesting the presence of high frequency internal waves these signals may have been the product of wave reflections from the steep flanks of the seamount and or wave generation from tidal currents flowing over the rough bottom associated with the enhanced shears and strains were more frequent occurrences of low 10 m richardson number events increased overturning scales and larger estimated turbulent eddy diffusivity relative to observations 15 km or more from the seamount in particular turbulent diffusivity estimates increased from o 0 1 10 4 m2 s 1 in the ocean interior to 1 5 10 4 m2 s 1 within 500 m vertically 1 3 km horizontally of the seamount flank a simple geometric scaling argument suggests that boundary mixing of this intensity has relevance to the large scale circulation at abyssal depths where a large fraction of the ocean waters is in close proximity to the bottom

spectral element modelling of fault plane reflections arising from fluid pressure distributions the presence of fault plane reflections in seismic images besides indicating the locations of faults offers a possible source of information on the properties of these poorly understood zones to better understand the physical mechanism giving rise to fault plane reflections in compacting sedimentary basins we numerically model the full elastic wavefield via the spectral element method sem for several different fault models using well log data from the south eugene island field offshore louisiana we derive empirical relationships between the elastic parameters e g p wave velocity and density and the effective stress along both normal compaction and unloading paths these empirical relationships guide the numerical modelling and allow the investigation of how differences in fluid pressure modify the elastic wavefield we choose to simulate the elastic wave equation via sem since irregular model geometries can be accommodated and slip boundary conditions at an interface such as a fault or fracture are implemented naturally the method we employ for including a slip interface retains the desirable qualities of sem in that it is explicit in time and therefore does not require the inversion of a large matrix we perform a complete numerical study by forward modelling seismic shot gathers over a faulted earth model using sem followed by seismic processing of the simulated data with this procedure we construct post stack time migrated images of the kind that are routinely interpreted in the seismic exploration industry we dip filter the seismic images to highlight the fault plane reflections prior to making amplitude maps along the fault plane with these amplitude maps we compare the reflectivity from the different fault models to diagnose which physical mechanism contributes most to observed fault reflectivity to lend physical meaning to the properties of a locally weak fault zone characterized as a slip interface we propose an equivalent layer model under the assumption of weak scattering this allows us to use the empirical relationships between density velocity and effective stress from the south eugene island field to relate a slip interface to an amount of excess pore pressure in a fault zone

gulf of mexico overpressure and clay diagenesis without unloading an anomaly abstract compaction disequilibrium is a widely accepted cause of overpressure especially in clay rich rapidly deposited sediments clay diagenesis has been associated with the occurrence of overpressure greater than the compaction disequilibrium overpressure these observations have led to the expectation that overpressure will be greater than the compaction disequilibrium contribution when clay diagenesis occurs within an overpressured mudstone clay diagenesis have been reported in a pliocene section of a well from the gulf of mexico offshore louisiana pressure and log data from that well indicate that despite clay diagenesis the overpressure can be attributed solely to compaction disequilibrium this paper examines the whole mudstone and clay mineralogy composition and petrophysical characteristics of the offshore louisiana well with clay diagenesis but without a diagenesis contribution to overpressure and contrasts that data with results from other clay diagenesis and petrophysical studies the comparison suggests that the offshore louisiana well was relatively smectite poor compared with wells from regions associated with a clay diagenesis contribution to overpressure the lower smectite content resulted in a lower percentage of reacted volume that was insufficient to allow the load transfer often associated with clay diagenesis petrophysical features of the offshore louisiana well and nearby wells differ from the features associated with clay diagenesis in other gulf of mexico wells and a limited number of international wells comparison of location age depositional package clay mineralogy and petrophysical features suggests that provenance may control the occurrence of gulf of mexico mudstones that do not experience increased overpressure as a result of clay diagenesis

temporal variations in river ice break up over the mackenzie river basin canada summary for northern and arctic regions the spring break up period has important socio economic ecological and morphological effects while these impacts are reasonably well understood spatial and temporal assessments of break up timing and duration remain limited due to the lack of readily available hydrometric data for this study the mackenzie river basin mrb of canada is selected as a test watershed in which the spatial and temporal aspects of observed 1913 2002 spring river ice break up are characterized data from 29 water survey of canada gauging sites are used including the commonly assessed last b date last ice effect and two hydrometric variables extracted directly from original water level recording charts the timing of initiation of break up and peak water level during break up it is found that the extracted variables provide a more physically based quantitative description of the break up season in the mrb compared to the last b date method on average the northwards progressing ice break up season within the mrb lasts 8 weeks but historically has varied within a window representative of 3 months of the year the break up period at specific locations varies from 4 days to 4 weeks results also indicate an anomalous zone of earlier spring break up in the upper peace and athabasca region that may be partially related to the effects of flow regulation in addition the mann kendall test reveals significantly earlier trends in the timing of spring break up 1 day decade in upstream portions of the major tributaries of the mrb over the period 1970 2002 while similar trends have been found for other hydroclimatic variables in the basin this study highlights the temporal patterns and variability of the spring break up period in the mackenzie river system

monitoring high altitude river ice distribution at the basin scale in the northeastern tibetan plateau from a landsat time series spanning 1999 2018 abstract river ice monitoring is important for hydrological research and water resource management of the tibetan plateau but limited by the serious shortage of field observations and remote sensing can be used as an effective supplementary means for monitoring river ice however remote sensing high altitude river ice is scarce and a basin scale understanding of river ice is lacking on the tibetan plateau to ascertain the spatial and temporal distribution characteristics of high altitude river ice at the basin scale we selected the babao river basin as the study area which is a typical river basin located in the northeastern tibetan plateau utilizing 447 available landsat images during the river ice period from 1999 to 2018 and the classical normalized difference snow index ndsi algorithm we monitored the river ice in a long time series at the babao river basin the average khat of accuracy validation reached 0 973 the average area of river ice in the river ice period of this basin showed a weak decreasing trend and was negatively correlated with air temperature we also found that gentle slopes and high elevations are beneficial for the development of river ice the melting of river ice supplements river discharge in spring this study is the first to reveal the distribution characteristics and changing trend of river ice at the basin scale on the tibetan plateau and the results provide a reference for river ice research in this region

structure and generation of turbulence at interfaces strained by internal solitary waves propagating shoreward over the continental shelf abstract detailed observations of the structure within internal solitary waves propagating shoreward over oregon s continental shelf reveal the evolving nature of interfaces as they become unstable and break creating turbulent flow a persistent feature is high acoustic backscatter beginning in the vicinity of the wave trough and continuing through its trailing edge and wake this is demonstrated to be due to enhanced density microstructure increased small scale strain ahead of the wave trough compresses select density interfaces thereby locally increasing stratification this is followed by a sequence of overturning high density microstructure and turbulence at the interface which is coincident with the high acoustic backscatter the richardson number estimated from observations is larger than 1 4 indicating that the interface is stable however density profiles reveal these preturbulent interfaces to be o 10 cm thick much thinner than can be resolved with shipboard velocity measurements by as

impact of lithospheric flexure on the evolution of shallow faults in the timor foreland system abstract re evaluation of structural evolution on the laminaria high timor sea australia shows that lithosphere flexure associated with the tertiary collision between the australian north west margin and the banda volcanic arc is an important mechanism for neogene fault development and the reactivation of jurassic structures 2d elastic models of the lithosphere flexure show that increasing flexural extension is likely to affect the laminaria high from the late miocene onwards the evaluation of the neogene fault slip history based on instantaneous throw estimates suggests an initiation of faulting during the late miocene when the laminaria high entered the flexed area forebulge increasing fault growth is recorded during the pliocene and correlates with the laminaria high reaching the hinge of the forebulge structure maximum episodes of fault growth are recorded between the late pliocene and early pleistocene when the laminaria high was located near the forebulge hinge or in the slope where curvature and flexural stress are likely to be maximal nnw extension associated with plate flexure allowed the oblique extensional reactivation of buried reservoir bounding jurassic structures the orientation of the jurassic structures relative to the flexural extensional front appears as a key factor controlling the type of segment linkage between the reactivated jurassic faults and the newly developed neogene faults observations from the laminaria high suggest that with an angle 20 between hmax and strike orientation of the jurassic faults soft linkage is likely to occur between jurassic and neogene segments an angle

organic geochemical indicators of dynamic fluid flow processes in petroleum basins a variety of preliminary geophysical geochemical and geological observations anderson et al geophysics 12 17 april 1991a b anderson oil gas j 85 91 26 april 1993 along with well production data schumacher aapg ann conv abstr april 1993 have led to the hypothesis that fluid injection into eugene island block 330 ei 330 in the u s louisiana gulf coast may be a continuing episodic process with the most recent injections having occurred on short geologic time scales 10 000 yr or less organic geochemical evidence presented here suggests these processes may occur on very short time scales years a process called dynamic fluid injection was proposed to explain these observations and is envisioned as episodic pressure build up followed by rapid escape of gas and oil through geopressure and injection into overlying reservoirs

oil migration through preferential petroleum migration pathway ppmp and polycyclic faults a case study from the shijiutuo uplift bohai bay basin china abstract the shijiutuo uplift is an oil enriched uplift in the offshore bohai bay basin petroleum migration is a key factor for oil enrichment in neogene reservoirs far away from the hydrocarbon kitchen in this article an integration of geological geophysical and geochemical analyses are employed to investigate the petroleum migration and accumulation on the shijiutuo uplift hydrocarbons in the qhd32 6 and qhd33 oilfields are mainly originated from the third e 2 s 3 and first e 2 s 1 member of the shahejie formation the shallow traps have significant contributions of late stage e 2 s 1 derived oil lateral petroleum migration is a major mechanism forming large oilfields on the shijiutuo uplift the large oilfields have multiple hydrocarbon kitchens multiple source rocks and numerous preferential petroleum migration pathways ppmps once petroleum arrives at the structural highs on the shijiutuo uplift through the guantao formation n 1 g carrier beds neotectonic faults cutting through guantao n 1 g and minghuazhen n 1 m l formations could serve as effective conduits for vertical petroleum migration neotectonic faults have experienced polycyclic fault activities fluid inclusions indicate episodic hydrocarbon charging crude oils display duplex properties of biodegradation and non biodegradation which is strong evidence for multiple and episodic oil charging on the shijiutuo uplift finally episodic petroleum charging along polycyclic neotectonic faults causes the late stage e 2 s 1 derived oils to occur in the shallow reservoirs

fault fracture mesh petroleum plays in the jiyang superdepression of the bohai bay basin eastern china abstract based on the results of laboratory simulation experiments and field observations the concept of fault fracture mesh petroleum play is proposed to explain the secondary petroleum accumulations in the neogene reservoirs of the jiyang superdepression bohai bay basin eastern china a well defined fault fracture mesh petroleum play usually contains three basic elements an oil source network at the base a transient storage for migrating hydrocarbons in the middle and a petroleum accumulation network at the top the oil source network provides fairways for hydrocarbons generated in a deep source to migrate vertically upward to shallow strata often consisting of primary faults and fracture zones and or regional unconformities in direct contact with mature petroleum source beds and secondary faults intercepting lenticular fluvial sandstones the transient storages for migrating hydrocarbons include the thick porous mat or sheet like sandstones deposited under the fluvial braided stream setting and occurring over relatively large geographic areas these sandstones serve as temporary storage spaces through which deep sourced petroleum fluids migrate further either laterally or vertically into shallower reservoirs the upper petroleum accumulation network provides suitable habitats for oil and gas accumulation comprising structural lithologic stratigraphic and combination traps the jiyang superdepression of the bohai bay basin hosts several excellent examples of the fault fracture mesh petroleum play where hydrocarbons in the neogene reservoirs were derived either directly from eocene oligocene source rocks or from the redistribution of pre existing oil accumulations in the deeper reservoirs reactivation of basement involved faults and regional unconformities provided conduits for channeling the pre neogene hydrocarbons into the shallow strata the magnitudes and frequencies of the faulting activities and their relative timings to those of peak oil generation and expulsion were critical factors for controlling the quantities of hydrocarbons transmitted to the neogene strata the thick sandstones and conglomerates in the lower guantao formation acted as excellent transient storages for the deep sourced oils which were then trapped to form accumulations in the shallow structural lithologic stratigraphic and combination traps of the guantao ng minhuazhen nm formations with the recent discovery of several giant oilfields in the shallow neogene reservoirs both onshore and offshore bohai bay basin the proposed fault fracture mesh petroleum play concept helps the exploration geologists to modify and clarify long held traditional concepts of petroleum play types in this basin and expand upon the new exploration horizons of the shallow subtle petroleum traps

spatial and temporal patterns in arctic river ice breakup revealed by automated ice detection from modis imagery abstract the annual spring breakup of river ice has important consequences for northern ecosystems and significant economic implications for arctic industry and transportation river ice breakup research is restricted by the sparse distribution of hydrological stations in the arctic where limited available data suggests a trend towards earlier ice breakup the specific climatic mechanisms driving this trend however are complex and can vary both regionally and within river systems consequently understanding the response of river ice processes to a warming arctic requires simultaneous examination of spatial and temporal patterns in breakup timing in this paper we describe an automated algorithm for river ice breakup detection using modis satellite imagery that enables identification of spatial and temporal breakup patterns at large scales we examine breakup timing on the mackenzie lena ob and yenisey rivers for the period 2000 2014 by dividing the rivers into 10 km segments and classifying each river pixel in each segment as snow ice mixed ice water or open water based on modis reflectance we determine breakup dates with a mean uncertainty of 1 3 days all statistically significant temporal trends are negative indicating an overall shift towards earlier breakup considerable variability in the statistical significance and magnitude of trends along each river suggests that different climatic and physiographic drivers are impacting spatial patterns in breakup trends detected on the lower mackenzie corroborate recent studies indicating weakening ice resistance and earlier breakup timing near the mackenzie delta in siberia the increased magnitude of trends upstream and strong correlation between breakup initiation and whole river breakup patterns suggest that earlier onset of upstream discharge may play the dominant role in determining breakup timing exploratory analysis demonstrates that modis imagery may also be used to differentiate thermal and mechanical breakup events

analysis of ers 1 synthetic aperture radar data of frozen lakes in northern montana and implications for climate studies lakes that freeze each winter are good indicators of regional climate change if key parameters such as freeze up and breakup date and maximum ice thickness are measured over a decade scale time frame synthetic aperture radar sar satellite data have proven to be especially useful for measurement of climatologically significant parameters characteristic of frozen lakes in this paper five lakes in glacier national park montana have been studied both in the field and using ers 1 sar data during the 1992 1993 winter the lakes are characterized by clear ice sometimes with tubular or rounded bubbles and often with a layer of snow ice on top of the clear ice they are also often snow covered freeze up is detected quite easily using ers 1 sar data as soon as a thin layer of ice forms the effect of snow ice on the backscatter is thought to be significant but is as yet undetermined on the five lakes studied relative backscatter was found to increase with ice thickness until a maximum was reached in february breakup an often ill defined occurrence is difficult to detect because surface water causes the sar signal to be absorbed thus masking the ice below comparison of the bubble structure of thaw lakes in northern alaska with lakes in northern montana has shown that the ice structure is quite different and this difference may contribute to differential sar signature evolution in the lakes of the two areas

natural fracture cleat and strong adsorption impact on low oil and condensate retention in the carboniferous shales and coals of the western black sea basin of turkey total organic carbon toc values of the carboniferous shales and coals of the western black sea basin of turkey range from 0 72 to 71 52 wt with an average of 32 3 wt and generation potential chance from 0 33 to 184 64 with an average of 82 47 mg hc g rock hydrogen index hi values of the shales and coals range from 24 to 384 mg hc g toc the hi versus pyrolysis temperature at the maximum rate of kerogen conversion plot indicates that the organic matter is type ii iii the calculated vitrinite reflectance equivalent values of the shales and coals range from 0 63 to 1 32 thus the shales and coals of the carboniferous formations are represented by immature effective oil and condensate generation windows the shales and coals of the alacaagzi formation contain high quartz and lower clay oil saturation index osi values of the shales and coals have been calculated as being 0 7 and 12 mg hc g toc indicating possible lack of producible oil and condensate the osi values are lower than those of other coal bearing and marine shales of the world first strong adsorption capacity may be a cause of the lower oil and condensate retention second faults natural fractures and cleats related fluid flows may be important factors in these lower osi ratios the extensional collisional and inverse tectonic stages and diagenetic processes of coalification formed multiple interconnected faults natural opening mode fractures and cleats in the shales and coals thus 15 coalbed methane exploration wells failed to produce any economical coalbed methane

silica activity and the smectite illite reaction early silicate diagenesis is characterized by the precipitation of minerals with high silica activity such as opaline silica smectite and clinoptilolite and by pore water silica activities exceeding quartz saturation with burial this early high silica activity diagenesic facies is succeeded by a low silica activity facies distinguished by quartz precipitation and progressive development of illite as the nonexpandable component of mixed layer clays we suggest that the smectite illite reaction occurs as a consequence of the reduction of silica activity at the onset of quartz precipitation data from oceanic and sedimentary basins confirm that the smectite illite reaction does not control aqueous silica activities where the smectite illite reaction occurs at higher temperatures aqueous silica activities likewise reach quartz saturation at higher temperatures