mesoscale eddy variability in the southern extension of the east madagascar current seasonal cycle energy conversion terms and eddy mean properties in this study we used more than 17 years of satellite altimetry observations and output from an ocean model to investigate the mesoscale eddy variability and forcing mechanisms to the south of madagascar analysis of energy conversion terms in the model has shown seasonality on eddy formation both by barotropic and baroclinic instabilities maximum in winter jja and minimum in summer djf the eddies were mainly formed in the upper ocean 0 300 m and at intermediate depths 800 2000 m by barotropic and baroclinic instabilities respectively the former dominated in the southeastern margin of madagascar and the latter to the southwest where the south east madagascar current semc separates from the continental shelf seasonality of the eddy formation appeared linked with the seasonal intensification of the semc the energy conversion terms indicated that the eddies have a significant contribution to the large scale circulation but not being persistent throughout the year occurring mainly during the fall season mam eddy demography from altimetry and model provided information on eddy preferential sites for birth annual occurrence 6 13 per year eddy mean diameter 124 178 km mean amplitude 9 28 cm life time 90 183 days and maximum traveling distances 325 1052 km eddies formed to the southwest of madagascar exhibited distinct characteristics from those formed in the southeast nevertheless all eddies were highly nonlinear suggesting that they are potential vectors of connectivity between madagascar and africa this may have a significant impact on the ecology of this region

isotopic evidence for carbonate cementation and recrystallization and for tectonic expulsion of fluids into the western canada sedimentary basin carbon oxygen and strontium isotope data for calcites and dolomites from the devonian obed platform in alberta canada demonstrate that 1 both limestones and dolostones of the obed platform underwent significant deep burial cementation and recrystallization 2 calcites experienced more extensive geochemical alteration than did dolomites under deep burial conditions and 3 the fluids that facilitated deep burial carbonate diagenesis probably were partially derived from the rocky mountain fold and thrust belt the more extensive degree of recrystallization of calcite is shown especially by its higher 87 sr 86 sr ratios a lesser degree of 13 c depletion in dolomites indicates that dolomite recrystallization partially coincided with hydrocarbon oxidation evidence supporting interpretation 3 above includes fractures and vugs bearing late diagenetic calcite cements that have extremely high 87 sr 86 sr ratios including the highest ratios reported thus far for any diagenetic carbonates from western canada 0 7252 in carbonates values this high are found only in tectonic veins in proterozoic clastic rocks in the rocky mountains and in the obed platform about 100 km into the foreland basin the late diagenetic calcite cements also have highly depleted 13 c values minimum 27 1 relative to pdb peedee belemnite indicating incorporation of oxidized carbon from thermochemical sulfate reduction the process of carbonate cementation and recrystallization in strata of the obed platform probably occurred during deep burial maximum 5 7 km and was effected by a hot 100 c mixture of connate brines and hydrothermal or metamorphic fluids that were expelled from the rocky mountain fold and thrust belt during the laramide orogeny the data also suggest that 1 the common practice of using limestones to establish marine or original geochemical baselines for stable and radiogenic isotope interpretations must be conducted with caution and 2 replacement burial dolostones are quite resistant to burial recrystallization finally the geochemical trace of tectonically expelled fluids may be limited to about 100 km into the foreland basin implying that the volumes and or fluxes of fluids produced by tectonic expulsion are rather low

the adjoint method of data assimilation used operationally for shelf circulation a real time shelf circulation model with data assimilation has been successfully used possibly for the first time on the outer nova scotian shelf the adjoint method was used to infer the time histories of flows across the four open boundaries of a 60 km 60 km shallow water equation model of western bank the aim was to hindcast and nowcast currents over the bank so that a patch of water initially 15 km in diameter could be resampled over a 3 week period as part of a study of the early life history of atlantic cod observations available in near real time for assimilation were from 14 drifting buoys 2 telemetering moored current meters the ship s acoustic doppler current profiler and the local wind for the postcruise hindcasts presented here data from two bottom pressure gauges and two more current meters are also available the experiment was successful and the patch was sampled over a 19 day period that included two intense storms in this paper we 1 document the model and how the data are assimilated 2 present and discuss the observations 3 demonstrate that the interpolative skill of the model exceeds that of simpler schemes that use just the current velocity data and 4 provide examples of how particle tracking with the model enables asynoptically acquired data to be displayed as synoptic maps greatly facilitating both underway cruise planning and postcruise data analysis an interesting feature of the circulation on the bank was a nearly stationary eddy atop the bank crest larvae within the eddy were retained on the bank in a favorable environment until the onset of the storms the variable integrity of the eddy may contribute to fluctuations of year class success

observed tidal currents outside block island sound offshore decay and effects of estuarine outflow 1 an array of moored profiling current meters on the inner continental shelf 15 65 m deep is used to investigate tidal currents outside the block island sound and long island sound estuarine system the m2 constituent dominates due to near resonant semi diurnal estuarine response vertical mean m2 currents rotate clockwise in time in ellipses elongated toward the estuary mouth with little sensitivity to complex local bathymetry semi major axes decay sharply offshore 55 to 20 cm s over 10 km in agreement with the nearly inverse square radius dependence of a kinematic theory estimated tidal volume exchange out of block island sound to the south is 2 9 105 m3 s observed vertical structure of m2 ellipses in the deepest 10 20 m amplitude decay ellipse flattening major axis turning clockwise phase advance is generally captured well by optimally fit frictional solutions despite the fact that they omit bathymetry and include stratification only indirectly through its influence on eddy viscosity in the upper water column vertical structure varies seasonally mid depth ellipses enlarge in spring near surface ellipses are larger smaller than optimal fit solutions in fall winter spring observed seasonal average estuarine outflow includes surface intensified coriolis deflected mean flow that strengthens and spreads farther offshore in spring richardson numbers based on moored hydrographic profiler records suggest spring stratification suppresses deep eddy viscosities which in frictional solutions can explain mid depth ellipse enlargement an inviscid theory for mean flow modifications due to ambient vorticity of estuarine outflow currents is shown to be the most plausible explanation for observed seasonal changes in near surface tidal ellipses

controls on the provenance of late eocene to quaternary mozambique channel shales dsdp 25 site 242 abstract provenance determination of late eocene to quaternary sediments deposited at the dsdp 25 site 242 may help to evaluate the mechanisms that have controlled the sediment deposition in the mozambique channel to determine the provenance of the clay fraction we measure major and trace element concentrations as well as strontium 87sr 86sr and neodymium isotopic compositions expressed as nd 0 of thirty six sedimentary samples from dsdp 25 site 242 on the eastern flank of the davie fracture zone light rare earth element lree enrichment and heavy ree hree depletions against post archean australian shales paas associated with ce anomalies higher than or equal to 0 90 for all the analyzed samples suggest very little influence of authigenic smectite incorporation the absence of correlation of al si and cia with ree content eu eu cr th th sc and 87sr 86sr and nd 0 suggests that chemical weathering has not modified these provenance proxies slight increase of eu eu cr th ratios nd 0 values associated with slight decrease in 87sr 86sr and th sc ratios from the late eocene to the quaternary point to input of less differentiated and younger detritus to the dsdp 25 site 242 with age based on variations in nd 0 and nd concentrations we estimate an overall decrease of the southeast african rivers congo zambezi contribution from 65 7 standard deviation s d 13 2 in the late eocene to 28 5 s d 10 0 in the early pliocene the causes for the low nd 0 values and high southeast african contribution between the late eocene and the early oligocene remain to be determined it could record the onset of modern sedimentation in the zambezi delta or the discharge of the paleo congo river in the indian ocean the decrease of zambezi contribution between the late oligocene and early pliocene is attributed to the cumulative effect of increasing tectonic activity of the davie fracture zone and intensification of the mozambique current the late pliocene to quaternary glacial interglacial cycles promoted higher zambezi contribution during glacial sea level lowstands and in turn lower nd 0 detrital values whereas low zambezi contributions are favored during interglacial highstand causing higher nd 0 values hence the modern dispersal pattern of fine grained sediments within the mozambique channel is no younger than late pliocene

modes of the southern extension of the east madagascar current data sets from satellite observations and a nested high resolution model are used to study a source region of the agulhas current altimeter derived geostrophic surface currents are averaged over varying periods providing evidence of the persistence of flow patterns in the extension of the southern branch of the east madagascar current semc south of madagascar the semc separates into one branch toward the agulhas current and into a second branch retroflecting and connecting to the subtropical indian ocean countercurrent sicc good agreement is found between long term mean patterns of observational and model dynamic heights two basic modes are identified in the semc extension with anticyclonic motion favoring retroflection in the northern mozambique basin when the extension is in a southwestward direction and cyclonic motion occurring in the case of the semc flowing westward along the southern madagascar slope a cross correlation sequence between model semc transports and the modal changes in the extension region displays a correlation at about 1 month lag which agrees with eddy propagation time from the semc to the outflow region mean model semc transports are determined using floats released at 21 degrees s and the contribution of the semc to the sicc is obtained using floats injected at 55 degrees e with the model running backward almost half of the semc volume transport contributes to the agulhas system and about 40 of sicc water originates from the semc

contrasting variability in foraminiferal and organic paleotemperature proxies in sedimenting particles of the mozambique channel sw indian ocean accurate sea surface temperature sst proxies are important for understanding past ocean and climate systems here we examine material collected from a deep moored sediment trap in the mozambique channel sw indian ocean to constrain and compare both inorganic delta o 18 mg ca and organic u 37 k tex86 temperature proxies in a highly dynamic oceanographic setting for application in paleoceanography high resolution time series current velocity data from long term moorings 2003 present deployed across the mozambique channel reveal the periodic migration of four to six meso scale eddies through the channel per year these meso scale eddies strongly influence water mass properties including temperature and salinity despite the dynamic oceanographic setting fluxes of the surface dwelling planktonic foraminifera globigerinoides ruber and globigerinoides trilobus follow a seasonal pattern temperatures reconstructed from g ruber and g trilobus delta o 18 and mg ca closely mirror seasonal sst variability and their flux weighted annual mean ssts of 28 1 degrees c and 27 3 degrees c are in close agreement with annual mean satellite sst 27 6 degrees c the sub surface dwelling foraminifera neogloboquadrina dutertrei and globigerinoides scitula recorded high frequency temperature variations that on average reflect conditions at water depths of 50 70 m and 200 250 m respectively concentrations and fluxes of organic compounds alkenones and crenarchaeol display no or only moderate seasonality but flux weighted means of the associated temperature signatures u 37 k and tex86h of 28 3 degrees c and 28 1 degrees c respectively also closely reflect mean annual sst we analyzed all time series data using multiple statistical approaches including cross correlation and spectral analysis eddy variability was clearly expressed in the statistical analysis of physical oceanographic parameters current velocity and sub surface temperature and revealed a frequency of four to six cycles per year in contrast statistical analysis of proxy data from the sediment trap did not reveal a significant coupling between eddy migration and organic compound fluxes or reconstructed temperatures this is likely a result of the relatively low resolution 21 days and short 2 5 years duration of the time series which is close to the detection limit of the eddy frequency

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

long term observations of transport eddies and rossby waves in the mozambique channel data from an array of current meter moorings covering a period of two and a half years are used to estimate the varying transport through the mozambique channel the total transport during this period is small below 1200 m the transport is weak but a prominent deep western boundary undercurrent with cores at 1700 and 2200 m is found that transports 1 5 sv to the north the transport shows a large temporal variability and neither a continuous upper layer western boundary current nor a continuous deep undercurrent is found the variability in the upper layer is dominated by a period of 68 days and results mainly from eddies that migrate southward through the mozambique channel in addition to this southward propagation a westward propagating signal is evident from a space time diagram of the throughflow the signal is interpreted as a mozambique channel rossby normal mode this interpretation is consistent with results from a principal oscillation pattern analysis that estimates normal modes from the data and a quasi geostrophic channel model a detailed inspection of a single eddy event shows that a precursor of an anticyclone is a strong southward current along the madagascar coast that propagates westward to the center of the channel during the westward propagation the current becomes unstable inducing an anticyclone this scenario connects the westward propagating mode with the eddy growth and explains the coincidence of the eddy and rossby mode frequency

wind driven motion near inner shelf fronts the response of inner shelf fronts to wind forcing is numerically studied here by using a three dimensional primitive equation model the front and its associated circulation are maintained by discharging light water near the surface and withdrawing heavier water from below along one vertical wall of a cyclic channel subsequently a spatially uniform alongshore wind is applied responses to an upwelling favorable wind and to a downwelling favorable wind are highly asymmetric upwelling favorable wind forces the light water pool to surface and expand offshore the pool is quickly detached from the source by the newly upwelled water even for a moderate plume and strong wind it is unlikely that a downwind coastal jet can develop and force the plume to turn against its natural direction of propagation recent observations of chesapeake plume support this finding downwelling favorable wind slowly narrows the plume inside which a strong coastal jet is developed for a density anomaly of finite alongshore extent the jet intensifies downstream reaches a maximum near the lead isopycnal and decays thereafter to compensate for the downstream acceleration strong onshore flow develops near the upstream edge of the plume if the wind persists the enhanced onshore flow further narrows the plume and triggers a second intrusion unstable waves develop behind the second intrusion they are however limited to small amplitudes by the prevailing onshore ekman drift

thermomechanical milling of accessory lithics in volcanic conduits accessory lithic clasts recovered from pyroclastic deposits commonly result from the failure of conduit wall rocks and represent an underutilized resource for constraining conduit processes during explosive volcanic eruptions the morphological features of lithic clasts provide distinctive textural fingerprints of processes that have reshaped them during transport in the conduit here we present the first study focused on accessory lithic clast morphology and show how the shapes and surfaces of these accessory pyroclasts can inform on conduit processes we use two main types of accessory lithic clasts from pyroclastic fallout deposits of the 2360 b p subplinian eruption of mount meager british columbia as a case study i rough and subangular dacite clasts and ii variably rounded and smoothed monzogranite clasts the quantitative morphological data collected on these lithics include mass volume density 2 d image analysis of convexity c and 3 d laser scans for sphericity and smoothness s shaping and comminution i e milling of clasts within the conduit are ascribed to three processes 1 disruptive fragmentation due to high energy impacts between clasts or between clasts and conduit walls 2 ash blasting of clasts suspended within the volcanic flux and 3 thermal effects we use a simplified conduit eruption model to predict ash blasting velocities and lithic residence times as a function of clast size and source depth thereby constraining the lithic milling processes the extent of shape and surface modification i e rounding and honing is directly proportional to clast residence times within the conduit prior to evacuation we postulate that the shallow seated dacite clasts remain subangular and rough due to short 2 min residence times whereas monzogranite clasts are much more rounded and smoothed due to deeper source depths and consequently longer residence times up to 1 h larger monzogranite clasts are smoother than smaller clasts due to longer residence times and to greater differential velocities within the ash laden jet lastly our model residence times and mass loss estimates for rounded clasts are used to estimate minimum attrition rates due to volcanic ash blasting within the conduit e g 12 cm3 s 1 for 25 cm clasts sourced at 2500 m depth

contrasting seasonal fluxes of planktonic foraminifera and impacts on paleothermometry in the mozambique channel upstream of the agulhas current 1 we assess d 18 o and mg ca based paleothermometry in relation to seasonal variations in the shell fluxes of the surface dwelling planktonic foraminifera g ruber and g trilobus using deep moored sediment traps in the mozambique channel upstream of the agulhas current we find a distinct antiphase response to the annual cycle in sea surface temperature sst in g ruber and g trilobus maximum fluxes of g ruber occur in late austral summer february march when sst ranges between 28 7 c and 30 3 c by contrast g trilobus maxima appear in early winter june july at a lower sst between 25 3 c and 27 0 c cross correlation of the 2 5 year time series data confirmed that the g ruber g trilobus ratio r t ratio closely followed the annual cycle in sst as did their paired d 18 o and mg ca in all proxies g ruber showed a 3 week phase lag against sst and g trilobus of 6 weeks consistent with semi lunar population turnover rates in combination with a 1 week settling time to the 2500 m deep ocean floor after correcting for these lags we derived five independent equations for improved paleothermometry in the southwestern indian ocean that specify flux weighted annual mean sst the offset between flux weighted sst of g ruber and g trilobus and annual mean instrumental sst is about 0 8 c despite their strong seasonality in shell export this is far less than the mean difference in instrumental sst between summer and winter of 3 2 c both species therefore closely reflect annual mean sst in sediments within a margin of 0 5 c for g ruber and 0 3 c for g trilobus w e also find that multiple linear regression of the five proxies r t ratio and the d 18 o mg ca of g ruber and g trilobus strongly reduces the effects of fast rotating eddies and improves the correlation coefficient from an r 2 of 0 4 to an r 2 of 0 8

synthesis and model of formation water flow alberta basin canada based on a large amount of publicly available data several studies have previously examined the flow of formation waters in different parts of the alberta basin offering various interpretations as to the causes of the observed pressure regime and flow pattern however there has been no synthesis of these diverse studies on a basin wide basis accordingly these studies are critically reviewed in this paper and synthesized in a new basin scale model of the flow of formation waters in the alberta basin the proposed regional scale model has significant implications for understanding hydrocarbon migration pathways ore genesis the geothermal regime and deep waste disposal in the alberta basin several flow systems each one driven by a different mechanism are identified together with the main processes leading to the nonhydrostatic pressures observed in the basin two megahydrostratigraphic successions and associated flow systems are recognized the first succession corresponds to the pre cretaceous passive margin stage of basin development and consists of thick carbonate dominated aquifer systems separated by shaly aquitards and evaporitic aquicludes a northeastward basin scale flow system is driven by basin topography with recharge in montana and discharge in northeastern alberta southwest to northeast regional scale flow adjacent to the fold and thrust belt is probably the result of past tectonic processes the salinity of formation water in pre cretaceous aquifers is high and generally increases both northward and with depth this variability is the result of increased water rock reactions mineral solubility with increased temperatu e and of incomplete flushing by meteoric water as a result of salinity variations flow retarding buoyancy effects can be important the second megahydrostratigraphic succession corresponds to the post jurassic foreland stage of basin evolution and consists of thick shaly aquitard systems and relatively thin sandstone aquifers in the southwestern part of the basin flow in isolated aquifers is driven southwestward by erosional rebound in the thick intervening shales downdip toward the fold and thrust belt the salinity of formation waters in the post jurassic aquifers is low mixing of waters and interference between the major flow systems takes place along the pre cretaceous unconformity where successively older pre cretaceous aquifers subcrop from west to east flow in shallow lo al systems at the top of the sedimentary succession is driven by local topography

in situ measured current structures of the eddy field in the mozambique channel abstract circulation and the related biological production have been studied during five cruises conducted in the mozambique channel mzc between 2005 and 2010 the circulation in the mzc is known to be highly turbulent favouring enhanced primary production as a result of mesoscale eddy dynamics and connectivity throughout the channel due to the variable currents associated with migrating eddies this paper presents the results of in situ measurements that characterize the horizontal and vertical currents in the surface and subsurface layers 0 500 m the in situ data were analysed together with the geostrophic eddy field observed from satellite altimeter measurements different circulation regimes were investigated including the classical anticyclonic eddy generated at the channel narrows 16 s the enhancement of southward migrating eddies by merging with structures both cyclonic and anticyclonic formed in the east of the channel and the presence of a fully developed cyclonic eddy at the channel narrows comparison between in situ measurements s adcp and velocities derived from surface drifters and the geostrophic current derived from sea surface height measurements indicated that the latter can provide a reliable quantitative description of eddy driven circulation in the mzc with the exception that these currents are weaker by as much 30 it is also suggested from in situ observation drifters that the departure from geostrophy of the surface circulation might be linked to strong wind conditions finally our observations highlight that a geostrophic currents need to be considered in future research to facilitate a more comprehensive description of the circulation in this area

the influence of bottom currents on the zambezi valley morphology mozambique channel sw indian ocean in situ current observations and hydrodynamic modelling abstract mixed turbidite contourite systems can be found in oceans where bottom currents and turbidity currents interact the zambezi turbidite system located in the mozambique channel sw indian ocean is one of the largest sedimentary systems in the world in length and area of the related catchments the oceanic circulation in the mozambique channel is intense and complex dominated by eddies flowing southwards and deep currents flowing northwards along the mozambican margin current measurements obtained from moorings at 3400 4050 m water depth in the zambezi and tsiribihina valleys show periods of intense currents at the seafloor with peaks of 40 50 cm s 1 that last up to one month and are not related to turbidity currents these strong bottom current events are correlated with a change in current direction and an increase in temperature the periods of current intensification may be related to eddies since they present similar frequencies around 7 per year moreover modelling results show that during periods of intense deep circulation an anticyclonic eddy is present between the mozambican slope and the centre of the mozambique channel which may block the northward transport of the deep water mass and thus enhance the southward transport along the western slope of madagascar according to our hydrodynamic modelling of the circulation near the seafloor intense currents are often present along the zambezi valley especially along the valley flanks multi channel seismic reflection data show that the zambezi turbidite system does not show the typical characteristics of turbidite systems being dominated by erosional processes which mainly affect the valley flanks levees associated with the valley are absent in the main axis of the system the effect of bottom currents on sedimentation in the basin is evidenced by the low sedimentation rates that witness winnowing in the basin the presence of contouritic sand in the zambezi valley flanks and the abundance of current related bedforms observed in multibeam bathymetry and seismic data the intense oceanic processes observed in the mozambique channel may transport a large part of the fine sediment out of the basin and erode the seafloor even at great depths therefore the zambezi turbidite system could at present be considered as a mixed turbidite contourite system with important implications for source to sink studies

open ocean boundary conditions from interior data local and remote forcing of massachusetts bay massachusetts and cape cod bays form a semienclosed coastal basin that opens onto the much larger gulf of maine subtidal circulation in the bay is driven by local winds and remotely driven flows from the gulf the local wind forced flow is estimated with a regional shallow water model driven by wind measurements the model uses a gravity wave radiation condition along the open ocean boundary results compare reasonably well with observed currents near the coast in some offshore regions however modeled flows are an order of magnitude less energetic than the data strong flows are observed even during periods of weak local wind forcing poor model data comparisons are attributable at least in part to open ocean boundary conditions that neglect the effects of remote forcing velocity measurements from within massachusetts bay are used to estimate the remotely forced component of the flow the data are combined with shallow water dynamics in an inverse model formulation that follows the theory of bennett and mcintosh 1982 who considered tides we extend their analysis to consider the subtidal response to transient forcing the inverse model adjusts the a priori open ocean boundary condition thereby minimizing a combined measure of model data misfit and boundary condition adjustment a consistency criterion determines the optimal trade off between the two the criterion is based on a measure of plausibility for the inverse solution the consistent inverse solution reproduces 56 of the average squared variation in the data the local wind driven flow alone accounts for half of the model skill the other half is attributable to remotely forced flows from the gulf of maine the unexplained 44 comes from measurement errors and model errors that are not accounted for in the analysis

physical influence on biological production along the western shelf of madagascar abstract in september 2009 the r v dr fridtjof nansen surveyed the western coast of madagascar environmental parameters of temperature salinity fluorescence and oxygen were profiled with a ctd probe and continuously underway at 5 m utilising a thermosalinograph equipped with a fluorescence sensor a ship mounted acoustic doppler current profiler adcp provided current profiles down to 250 m while estimates of biomass were obtained from acoustics and trawling was used for species identification in addition visual whale observations were conducted the survey revealed three areas that were identified as upwelling regions namely the southern coast 26 s offshore from cap st andre 16 s and near nosy be island 13 s in these upwelling regions acoustic estimates trawling and whale observations indicated high biological productivity the total acoustic estimate for the whole western coast was as low as 62 000 t typical for tropical waters in addition to the upwelling areas high biological productivity was also found outside river mouths ship born wind measurements as well as re analysed wind fields indicated that the southern coast upwelling cell was wind driven and had a larger extent than reported earlier the wind conditions were not favourable for upwelling in the two northernmost upwelling cells here the adcp showed high bottom velocities 1 m s 1 oriented northeast these currents were probably forced by the migrating eddies in the area as indicated by the remotely sensed sea level anomaly sla such currents induce bottom friction layer transport oriented towards the coast thus driving upwelling although not necessarily penetrating all the way to the surface layer as was the case near cap st andre

the relation between stratigraphic elements pressure regime and hydrocarbons in the alberta deep basin with emphasis on select mesozoic units we have very little to state by way of a response to bachu et al 2002 except to make the following brief observations and comments 1 the reader will note that the title specifically deals with the relation between stratigraphic elements pressures and hydrocarbons with an emphasis on mesozoic units this emphasis is clearly stated in putnam and ward 2001 p 692 the major aim of this article is to document and interpret the significance of overpressured mesozoic sandstones in western alberta bachu et al s 2002 p 525 comments however are focused on pressure and flow systems particularly in the devonian in fact our results have been reviewed with reference to the complete geological column in west central alberta and the units discussed were provided both as examples of the two hydrodynamic regimes present and the

spring summer frontogenesis at the mouth of block island sound 2 combining acoustic doppler current profiler records with a general circulation model to investigate the impact of subtidal forcing 1 the use of a one layer inverse model to improve the fidelity of a three dimensional primitive equation model is explored in the region just south of block island sound in the middle atlantic bight the inverse model based on the theory of bennett and mcintosh produces a solution to the linear shallow water equations that minimizes model data misfit and the resulting open boundary velocity variance the massachusetts institute of technology general circulation model is configured regionally and includes realistic tidal forcing surface warming and wind stress as well as climatological buoyancy gradients between the estuary and the shelf a 15 day record from two acoustic doppler current profiler moorings deployed in spring 2000 south of the entrance of block island sound allows assessment of the forward model and provides data to improve subtidal boundary conditions model data misfit decreases notably for both the depth averaged and vertically sheared flow indicating that improvements to the depth averaged circulation positively impact the three dimensional circulation in this shallow shelf environment the role of wind stress in modulating the position of the buoyant plume that characterizes the regional hydrography is also examined a distinctly three dimensional circulation is observed with a growing offshore plume at the mouth of the sound during northward stress followed by rapid alongshelf advection during periods of southwestward or weak winds although on the timescales considered here wind stress forcing dominates the buoyancy driven motion it is overwhelmed by the tidally driven rectified flow just south of montauk point which provides the inshore boundary of the front even in downwelling favorable conditions

a direct determination of the world ocean barotropic circulation abstractthe time mean argo float displacements and the world ocean atlas 2009 temperature salinity climatology are used to obtain the total top to bottom mass transports outside of an equatorial band the total transports are the sum of the vertical integrals of geostrophic and wind driven ekman currents however these transports are generally divergent and to obtain a mass conserving circulation a poisson equation is solved for the streamfunction with dirichlet boundary conditions at solid boundaries the value of the streamfunction on islands is also part of the unknowns this study presents and discusses an energetic circulation in three basins the north atlantic the north pacific and the southern ocean this global method leads to new estimations of the time mean western eulerian boundary current transports maxima of 97 sverdrups sv 1 sv 106 m3 s 1 at 60 w for the gulf stream 84 sv at 157 e for the kuroshio 80 sv for the agulhas current between 32 and 36 s and finally 175 sv for the

interaction of dipole eddies with the western continental slope of the mozambique channel abstract sea level anomaly sla data were used to track a southward propagating eddy dipole along the western slope of the mozambique channel over some 6 months in april 2005 this dipole with the cyclone to the south was close to the continental slope off southern mozambique the contact zone between the contra rotating vortices and the slope was surveyed by ship using onboard s adcp and ctd lines the data showed strong 1 4 m s 1 southward geostrophic currents over the slope adjacent to the anticyclone with horizontal divergence over the shelf edge significant slope upwelling between the dipole and the shelf was evident concomitant with enhanced nutrient and chlorophyll levels enriching shelf near surface waters satellite observations depicted a 300 km long surface chlorophyll filament extending offshore in the frontal zone between the contra rotating vortices a satellite tracked drifter deployed at the coastal base of this filament confirmed the offshore advection of chlorophyll enriched shelf water which ultimately wrapped around the cyclone and filling its centre the slope upwelling was also clearly evident in hourly temperature data collected by a recorder deployed on a nearby reef zambia reef in a depth of 18 m according to the sla data the dipole took several weeks to pass zambia reef causing prolonged bouts of upwelling that finally ceased when it left the continental slope and moved southwards into the open ocean further analysis showed that lone anticyclones and cyclones against the mozambique continental shelf also induce slope upwelling as a result of horizontal divergence created by the radial circulation of the vortex in the case of cyclones the divergence occurs north of the contact zone overall this case study confirms that eddies moving southwards along the western side of the mozambique channel are the main mechanism for pumping nutrients into the otherwise oligotrophic surface waters and moreover provide a vigorous mechanism for shelf open ocean exchange

the fate of river discharge on the continental shelf 2 transport of coastal low salinity waters under realistic wind and tidal forcing a three dimensional numerical simulation of shelf circulation is presented we employ realistic forcing for the southeast u s continental shelf during the spring season we show that the strongest offshore transport of river induced coastal low salinity waters and associated materials occurs near the surface the preferred mean pathway is in the northeastward direction and it takes about 2 months to cross the entire shelf owing to the mean direction of surface transport and the topography of the south atlantic bight shelf the preferred location for springtime removal is off charleston south carolina and presumably in the vicinity of the charleston bump the transport and fate of the river induced coastal low salinity waters during the spring season are determined by 1 the stratification of nearshore waters which is due to the high river runoff and causes the decoupling between near surface and near bottom layers 2 the prevailing northeastward winds which cause significant offshore transport within the shallow near surface ekman layer and 3 the tidally induced bottom stirring m2 tides comparison of model and data time series of currents shows very good agreement standard deviations of the model and data computed empirical orthogonal functions are almost identical while the respective variance conserving spectra agree both in amplitude and phase

eddies in the southern mozambique channel abstract the agulhas current system contains one of the world s strongest western boundary currents and plays an important part in the warm water path of the global thermohaline circulation however there have been few surveys of the source regions of the agulhas current and thus little in situ measurement of their variability utilizing the more than 5 year record of seawifs data we examine the eddy activity present in the southern portion of the mozambique channel the two sources of agulhas input from the central indian ocean southward flow through the mozambique channel and westward flow around the southern limit of madagascar both show great temporal variability with no clear seasonal signal a number of large 200 km diameter anticyclonic rings intermittently propagate poleward along the western edge of the channel sweeping coastal waters into mid channel their passage past maputo appears to affect the circulation of the lee eddy in the delagoa bight the eastern side of the channel is mainly characterized by cyclonic eddies these are made manifest in the lee of the southern tip of madagascar although it is not clear whether many form there or just develop a visible presence due to entrainment of high chlorophyll coastal waters several of these cyclonic eddies then appear to move in west southwesterly direction the chlorophyll data do reveal the apparent east madagascar retroflection on occasions but do not show clear examples of the pinching off of anticyclonic eddies however surface waters from the east madagascar current may reach the african mainland on occasions when no retroflection is present

detailed characterization of a cold antarctic eddy 1 eddy formation in the southern ocean plays a critical role in meridional exchanges of heat and salt it has also been shown to have a significant impact on primary productivity and on the creation of preferred feeding regions for birds and other predators this eddy formation is not geographically uniform but is concentrated in certain specific regions particularly where the antarctic circumpolar current crosses shallow bathymetry one such region is at the south west indian ridge where eddies are formed that subsequently drift past the prince edward islands we have studied such an eddy in detail it was at least 1000 m deep had a radius of 60 90 km a heat content of 5 40 1019 j and rotated at a rate of 1 revolution every 5 days altimetric observations show that it was formed at 51 s 32 e and that its intensity as expressed as its sea level anomaly declined by 40 of the original value within 144 days this relatively rapid dissipation suggests that these eddies do not have a lifetime of more than 14 months during that period they will have carried their anomalous heat and salt content about 1 5 degrees of latitude

observed characteristics of mozambique channel eddies 1 the flow in the mozambique channel is dominated by large southward propagating anti cyclonic eddies as opposed to a steady western boundary current these mozambique channel eddies feed their waters into the agulhas current system where they are thought to have a significant influence on the formation of the natal pulse and agulhas ring shedding here we use in situ hydrographic and nutrient data together with satellite altimetry and surface velocity profilers to provide a detailed characterization of the mozambique channel eddies two warm eddies in the channel at 20 s and 24 s had diameters of over 200 km they rotated anti cyclonically with a tangential velocity of over 0 5 m s 1 vertical sections show that the eddies reached to the bottom of the water column relative to the surrounding waters the features were warm and saline the total heat and salt anomalies for the southernmost eddy were computed relative to a reference station close by at 24 s the total anomalies were 1 3 1020 j and 6 9 1012 kg respectively being on par with agulhas rings mozambique channel eddies thus have the potential to form a major contribution to the southward eddy heat flux in the agulhas current system the feature also had positive nutrient and negative oxygen anomalies the large magnitude of the water mass anomalies within the eddy suggests that interannual variability in mozambique channel eddy numbers would have a significant impact on downstream water mass characteristics

stability of western boundary currents with an application to pulselike behavior of the agulhas current the northern agulhas current off south africa displays very steady flow characteristics roughly five to six times per year the flow is disrupted by the passage of large solitary meanders propagating downstream observations obtained from moored current meters show that these so called natal pulses extend over the full depth of the current several hypotheses have been proposed for the generation of these pulses here the authors investigate whether they arise as a barotropic instability on the inshore flank of the current itself the stability analysis is performed using a prescribed background state loosely based on agulhas current observations unstable inshore modes are found with propagation speeds close to those of the observed pulses to explain the intermittent temporal behavior of the pulses the interaction of the unstable modes of the western boundary current in the nonlinear regime is investigated the results indicate that the onset of pulselike behavior is found in wave mean flow interaction of unstable inshore modes with the background jet whether the observed timing of pulses is due to internal variability or set by processes external to agulhas current proper remains an open question

sedimentation patterns off the zambezi river over the last 20 000 years marine sediments from continental margins provide high resolution archives of marine and continental climate in particular near large river mouths the zambezi is one of the largest rivers in east africa discharging large amounts of fine grained sediments onto the western margin of the mozambique channel accurate reconstructions of past variations in river discharge can be retrieved from the depositional history of riverine sediments in this study sedimentation patterns along the mozambique margin are inferred from a series of sediment cores spanning the last 20 kyr these cores were retrieved off the zambezi mouth from the shelf and from various depths at the continental slope to provide detailed information on the depositional history of this region high resolution x ray fluorescence and magnetic susceptibility core scanning measurements as well as grain size distributions of the lithogenic sediment fraction and organic matter and carbonate content analyses resolve centennial millennial timescale variations in sediment transport and deposition along the mozambique margin largest changes in lithogenic sediment deposition coincide with the flooding of the mozambique shelf due to deglacial sea level rise and changes in oceanic currents fine grained mainly zambezi sediments were no longer primarily deposited south of the zambezi mouth but increasingly deposited onto the mozambique shelf and transported northwards over the shelf before spilling over to the slope in addition flooding of the shelf initiated remobilization and down slope transport of coarse grained winnowed sediments the heinrich event 1 and younger dryas are clearly indicated as events of increased fine grained sediment deposition along the mozambique margin possibly linked to increased riverine runoff from the zambezi catchment which is in harmony with a southward shift of the intertropical convergence zone itcz and associated african rainfall belts causing wetter conditions this study illustrates that interpreting marine and continental climate proxy records in the vicinity of river deltas in terms of climate change requires proper consideration of sea level and oceanic circulation induced effects on the transport and deposition patterns of fine grained sediments at continental slopes

coal quality coal rank variation and its relation to reconstructed overburden upper cretaceous and tertiary plains coals alberta canada near surface coals in the alberta plains occur in upper cretaceous and tertiary sediments the former represented by the belly river group horseshoe canyon formation and wapiti formation and the latter by the scollard member of the paskapoo formation statistical techniques were used to document both the distribution of and the interrelationships among the components of proximate and ultimate analysis and calorific value determinations the coals discussed range in rank from subbituminous c to high volatile bituminous c these coals are variable in ash content and low in sulfur content the relationships among calorific value dry basis in kj kg and ash dry basis in and calorific value moist mineral matter free basis in kj kg and equilibrium moisture meq in were determined to be cvd 29 677 315 17 ashd and cvmmmf 31 816 442 05 meq respectively the maximum depth of coal seam burial dob in m was reconstructed on the basis of previously published graphs relating the equilibrium moisture loss to depth of coal seam burial using the relationship log10meq 1 865 0 000416 dob a least squares regression analysis of calorific value mmmf basis in k kg on the calculated depth of burial dob in m yielded the equation cvmmmf 14 748 6 25 dob indicating a coalification gradient determined on the reconstructed overburden of 6 25 kj kg m 0 82 btu lb ft of depth or overburden near surface coals in the alberta plains increase in rank toward the west southwest toward the foothills and mountains region because of progressively greater amounts of overburden that existed in that direction during the tertiary erosion has since removed between 900 and 1 900 m 3 000 and 6 200 ft of sediment with the greatest amount of removal occurring in a west southwest direction

agulhas current meanders facilitate shelf slope exchange on the eastern agulhas bank large solitary meanders are arguably the dominant mode of variability in the agulhas current observational studies have shown that these large meanders are associated with strong upwelling velocities and affect the shelf circulation for over 100 days per year here 10 year time series from two ocean general circulation models are used to create a composite picture of the agulhas current and its interactions with the shelf circulation in meandering and nonmeandering modes both models show good agreement with the size propagation speed and frequency of observed meanders these composite meanders are then used to examine the response of shelf waters to the onset of large meanders with the use of model output enabling the dynamics at depth to be explored results show a composite mean warming of up to 3 c of depth averaged temperature along the shelf edge associated with an intrusion of the current jet onto the shelf driven by an intensification of the flow along the leading edge of large meanders however this intensification of flow results in cooling of bottom waters driving cold events at the shelf break of 10 c at 100 m thus the intensification of the current jet associated with large meander events appears to drive strong up and downwelling events across the inshore front of the agulhas current facilitating shelf slope exchange

the influence of thermochemical sulphate reduction on hydrocarbon composition in nisku reservoirs brazeau river area alberta canada abstract the upper devonian nisku formation reservoirs of the brazeau river area of west central alberta canada produce oil and sweet and sour gas condensate generally oil pools are located updip in the study area and sour 6 31 h2s gas condensate downdip h2s in the study area is formed by thermochemical sulphate reduction tsr all liquid hydrocarbons probably have one source with the duvernay formation being the most likely candidate assessing the relative maturity of the oils and condensates is difficult because of the wide variation in thermal maturity and the effects of tsr but the ratio of pristane n heptadecane does appear to decrease with increasing maturity for this sample set with increasing tsr the following changes were noted decrease in the saturate aromatic hydrocarbon ratio increase in the relative abundance of organo sulphur compounds e g benzothiophenes 34s values of liquid hydrocarbon samples approached the values for anhydrite of the nisku formation in the study area and an increase in 13c of the saturate fraction h2s concentrations in hydrodynamically isolated pools provide a good estimate of the extent of tsr in these reservoirs however other pools have anomalously high h2s concentrations for their depth suggesting that the h2s was generated at greater depths and migrated updip into these pools

modern sedimentation and geochemical imprints in sediments from the nw madagascar margin abstract the nw madagascar continental margin receives high loads of terrigenous particulate organic matter during the wet season and especially linked to extreme events originating from two major rivers the betsiboka and the mahavavy rivers this particulate matter contains a high content of iron minerals from the weathering of red ferruginous ferralitic soils of madagascar the presence of pockmarks i e gas or fluid expulsion features on the continental slope testifies to past present methane migration through the sedimentary column associated with early diagenetic processes this study globally aims at deciphering the interactions between episodic sedimentation and geochemical processes influenced by fluids upward migration using a sediment trap mooring and interface sediment cores at two sites on the continental slope the present day sedimentation along this margin undergoes two patterns during the wet season high continental fluxes generally result in an increase in particle fluxes on the slope longshore currents may deflect river plumes alongslope resulting in some periods of low particle flux on the slope during the wet season during the dry season the particles collected in the water column are probably originated from sediment remobilization from the shelf and slope the observed progradation of the mahavavy river delta and prodelta between 1984 and 2016 argues for an increase in temporary connections of the river with the canyon head during extreme events inducing pulsed sedimentation offshore this pulsed sedimentation could be responsible for enhancing pyritization on surface sediments due to higher inputs of terrigenous organic matter and iron oxides finally methane upward migration also influences the pyritization process through anaerobic oxidation of methane using sulfate as an electron acceptor and methanotrophs associated with this reaction significantly impact the 13c of organic carbon towards more negative values

seasonal variation of a coastal jet in the long island sound outflow region based on hf radar and doppler current observations 1 surface current hf radar and velocity profile observations obtained as part of the front resolving observational network with telemetry front project over an approximately 2 year period are used to describe the seasonal variability of a coastal jet in the long island sound outflow region the jet is observed in an area of the continental shelf where surface thermal fronts are frequently detected during both summer and winter the current jet is coincident with a band of high summer frontal probability and apparently arises from the interaction between long island sound outflow and larger scale alongshore currents on the shelf the jet reaches peak strength in summer transport of 0 07 sv and is weak or non existent in winter flow is strongest near the surface and weakens with depth with only moderate seasonal variations in the vertical shear the relatively long data set of currents combined with historical hydrographic measurements and buoy wind observations is analyzed to examine the seasonal variability of the terms in the depth averaged momentum balance the depth averaged pressure gradient is partitioned into a steric component evaluated from the hydrography and a non steric component that is estimated as the residual of the computed terms in the momentum equation the depth averaged momentum balance is found to be approximately geostrophic in the across shore direction the seasonal variability in the jet arises due to the shifting balance between buoyancy driven flow that is always downshelf but intensifies somewhat in summer and wind driven flow which dominates in winter when wind stress becomes strongly upwelling favorable

origin chemistry and flow of formation waters in the mississippian jurassic sedimentary succession in the west central part of the alberta basin canada abstract the flow and chemistry of formation waters was analyzed in the mississippian jurassic succession in the west central part of the alberta basin using publicly available standard chemical analyses of formation waters and drillstem test data collected by the petroleum industry in alberta the interpretation of the thoroughly culled hydrogeological data show that a transition between a southern and a northern basin scale flow system takes place in the study area in the southeastern half of the study area the mississippian jurassic hydrostratigraphic group represents a single continuous carbonate sandstone aquifer system consisting of the lower jurassic nordegg member the triassic montney formation the permian belloy formation and the mississippian stoddart and rundle groups the confining units are the competent fernie and exshaw banff aquitards at the top and base respectively the salinity of formation waters increases northwestwards from 50 to 150 g l while the bicarbonate content decreases in similar fashion from 3 to 0 5 g l the flow pattern based on hydraulic heads and chemical composition of formation waters indicate decreasing mixing of meteoric water carried northward in the southern basin scale long range system with heavier connate water present in the northern part of the study area in the center and in the northeast the permian and mississippian carbonates and the triassic montney and charlie lake halfway sandstones form individual aquifers separated by the intervening doig montney aquitard the flow in the charlie lake halfway and the permo mississippian aquifers is directed east northeastward from the deformation front into the overlying aquitards or discharging into the southern basin scale flow system respectively only in the montney aquifer the flow is directed inward south southwestward drawn into a local hydrocarbon saturated sink which is created by a higher rate of gas escape than of gas generation through a low permeability and capillary seal region the high salinity in the 130 150 g l range and low bicarbonate content 0 5 g l of formation waters in the northern part of the study area indicate a connate origin the relation of na ca cl br concentrations in the formation waters suggest that these waters initially originated as seawater that was altered to some degree by subaerial evaporation and dolomitization but halite dissolution probably is the main source of salinity the driving mechanism for the flow of these waters could be either tectonic expulsion from deep strata in the deformed part of the basin as suggested by the high salinity of these waters or topography driven meteoric recharge in the rocky mountains through a tortuous path unidentified as yet the integrated interpretation of flow and chemistry of formation water shows that mississippian jurassic formation waters in the deep west central parts of the alberta basin have been influenced less by mixing with meteoric water than was identified previously in the central southern and northern parts of the basin the main reasons for the isolation of relict mississippian jurassic formation waters in the deep alberta basin are effective confining aquitards and the fact that this area is influenced only marginally by mixing with meteoric water carried by a gravity driven flow system

upscaling permeability for reservoir scale modeling in bioturbated heterogeneous tight siliciclastic reservoirs lower cretaceous viking formation provost field alberta canada abstract variations in bed and bedset scale permeability in bioturbated siliciclastic rocks result in heterogeneity that is difficult to model at a reservoir scale this paper presents a technique to upscale permeability such that the permeabilities of the bioturbated zones are explicitly included in the upscaled values study of 28 cored wells of the lower cretaceous viking formation in the provost field alberta canada integrated sedimentologic and ichnologic features to define recurring bed bedset scale hydrofacies hfs characterized by a geometric mean permeability derived from plug samples permeability was upscaled by calculating equivalent vertical and horizontal permeabilities for composite hydrofacies chfs using expressions for layered media the equivalency of the vertical and horizontal permeability values assigned to the chfs against those of the hfs was evaluated using a simple numerical flow model reservoir scale flow was then simulated along a hydrogeological cross section that was constructed using the chfs the resulting flow regime was consistent with flows simulated using published permeability estimates from tight reservoir units of the viking formation this approach has the potential therefore for upscaling permeability for reservoir scale modeling in tight oil and gas reservoirs and more broadly in reservoirs where permeability is highly variable at the bed bedset scale

reservoir geology of crystal viking field lower cretaceous estaurine tidal channel bay complex south central alberta the lower cretaceous viking formation in the crystal field of south central alberta contains a linear sandstone body as much as 30 m thick that forms a complicated dual pool hydrocarbon reservoir this contrasts sharply with most other viking reservoirs which are much thinner are commonly oriented northwest and are composed of a single hydrocarbon pool thickness orientation and pool duality are attributed to the complicated depositional history of the viking in the crystal region the sandstone body is interpreted as a multistage tidal channel fill deposit within a larger estuarine channel bay complex which rests unconformably on inner shelf lower shoreface facies a major lowstand of sea level that occurred approximately 97 m y ago is believed to be responsible for incisement of the estuarine valley which was filled during rising sea level a depositional model of progressive estuarine valley fill under transgressive conditions readily accounts for the occurrence of two hydrodynamically separated oil pools and also for differences in reservoir continuity and performance trends within the main oil bearing a pool highly productive wells in the main pool correspond to specific channel fill deposits or are situated in areas where deposits of successive channel stages are highly superimposed conversely marginally productive wells and poor reservoir communication between producing wells occur in areas where the different channel stage deposits diverge

spring summer frontogenesis at the mouth of block island sound 1 a numerical investigation into tidal and buoyancy forced motion 1 the generation and underlying dynamics of late spring temperature and salinity fronts at the mouth of block island sound in the mid atlantic bight are examined using a three dimensional general circulation model the model is forced by tidal velocities at its outer boundaries an estuary shelf salinity gradient and surface warming runs representing the period from 18 april to 23 may 2000 are investigated through direct examination of the model results and diagnostic calculations that isolate individual processes three mechanisms are identified as significantly contributing to the location and structure fronts observed in this region vertical mixing produces the necessary horizontal temperature structure within and near block island sound but the southern frontal boundary is further affected by the subtidal circulation which is divided into two components defined using a momentum budget analysis tidal currents over the complex bathymetry leads to nonlinearly rectified flows including a headland eddy south of montauk point circumscribing this feature is a baroclinically adjusted buoyant outflow from the long island sound estuary while modifications to the buoyancy forcing can modify the frontal position it necessarily remains offshore of the tidally driven circulation analysis of the salinity anomaly fluxes indicates that both tidal and mean advection are responsible for the overall transport of buoyancy

mesoscale activity in the comoros basin from satellite altimetry and a high resolution ocean circulation model recently it has been shown that anticyclonic eddies are generated in the comoros basin contesting the long held notion of a single large anticyclonic cell the comoros gyre limited knowledge exists about the mesoscale activity within the basin a potential key source of variability for the mozambique channel and subsequently the agulhas current in this paper an automated eddy tracking scheme applied to satellite altimetry data and a high resolution model simulation is used to determine the characteristics of the anticyclonic eddies generated in the comoros basin the generation and characteristics of cyclonic eddies are also investigated the eddy tracking scheme revealed that anticyclonic eddies are primarily generated west of the tip of madagascar due to barotropic instabilities whereas cyclonic eddies are mainly generated along the northwest coast of madagascar as a result of baroclinic instabilities anticyclonic eddies with a mean lifespan of about 3 months reside in the basin for half their lifespan before propagating into the mozambique channel on the other hand the majority of cyclonic eddies with a similar mean lifespan dissipate within the basin initially the anticyclones with translation speeds of 6 8 km d 1 and mean radii of 80 100 km follow the trajectory of the north east madagascar current and turn south upon reaching the african coast the cyclonic eddies tend to be smaller 60 km and have slower translation speeds 2 5 3 5 km d 1 than their anticyclonic counterparts

geothermal gradients hydrodynamics and hydrocarbon occurrences alberta canada using coal rank data and the demonstrated genetic link between the present hydrodynamic regime and geothermal gradient pattern it is possible to reconstruct the geothermal history of alberta over the past 60 m y palinspastic adjustment for tectonic compression caused by the major laramide thrusting shows that the predeformation isoreflectance lines increased logarithmically with depth in the late paleocene the geothermal gradient was about 23 c km 1 25 f 100 ft in the eastern alberta plains compared to about 30 c km 1 65 f 100 ft in the western alberta plains a regional trend opposite to the post laramide trends reconstruction of the early eocene surface indicates western uplands with geothermal gradients as low as 21 c km 1 15 f 00 ft and eastern lowlands with geothermal gradients of 27 c km 1 5 f 100 ft compared to the present situation this represents an enhanced topographic surface and a subdued geothermal gradient pattern the genetic relations of topography water table elevation hydrodynamic regime and geothermal gradient pattern in both the early eocene and the present conform to a model developed for any compacted sedimentary basin with subaerial relief in this model on a regional scale high topographic areas have high water table elevations with correspondingly high potentiometric surfaces these areas control the regional recharge of cold meteoric water and hence have low geothermal gradients areas of medium elevation exhibit regional lateral flow and intermediate geothermal gradients regional topographic lows correspond with low potentiometric surfaces and the regional discharge of warm formation waters from deep in the basin results in high geothermal gradients local topographic featur s cause perturbations in this picture study of both the regional pattern and fine detail of the early eocene and present topographic surfaces and geothermal gradient patterns shows the validity of the model the result of the second laramide orogenic pulse was therefore to reverse the geothermal gradient pattern resulting mainly from compaction flow and to impose a topographically controlled hydrodynamic regime with flow in the same direction but with a 9 c km 0 5 f 100 ft decreased geothermal gradient in western alberta and a 4 c km 0 2 f 100 ft increased geothermal gradient in eastern alberta as erosion proceeded during the tertiary the entire alberta basin warmed up until the present temperature regime was attained study of some major hydrocarbon occurrences shows a genetic link between the hydrocarbon occurrence and the present fluid regime which itself is controlled by the present topography for at least the significant upper cretaceous shallow gas reserves in southeastern alberta however their position may already have been determined as early as the beginning of the eocene by the topographic surface at that time therefore the extent to which the present topographic surface is responsible for hydrocarbon accumulation through gravity induced cross formational flow remains unknown because this process was operative as long ago as the early eocene what does not ap ear to be in doubt is the fact that gravity induced cross formational flow does control the hydrodynamic regime which in turn influences the geothermal gradient pattern and the accumulation of hydrocarbons

observed eddy dissipation in the agulhas current analysing eddy characteristics from a global dataset of automatically tracked eddies for the agulhas current in combination with surface drifters as well as geostrophic currents from satellite altimeters it is shown that eddies from the mozambique channel and south of madagascar dissipate as they approach the agulhas current by tracking the offshore position of the current core and its velocity at 30os in relation to eddies it is demonstrated that eddy dissipation occurs through a transfer of momentum where anti cyclones consistently induce positive velocity anomalies and cyclones reduce the velocities and cause offshore meanders composite analyses of the anti cyclonic cyclonic eddy current interaction events demonstrate that the positive negative velocity anomalies propagate downstream in the agulhas current at 44 km day 23 km day many models are unable to represent these eddy dissipation processes affecting our understanding of the agulhas current

characterisation of mesoscale features and phytoplankton variability in the mozambique channel abstract variability of hydrographic characteristics and phytoplankton distribution associated with mesoscale eddies in the mozambique channel was investigated during four cruises in september 2007 december 2008 november 2009 and april may 2010 satellite altimetry was used to map the location of mesoscale features and together with etopo1 bathymetry was used in a discriminant function analysis to classify in situ sampling stations into five categories namely cyclonic c anti cyclonic a frontal f divergence d and shelf s fluorescence profiles were integrated through four depth ranges in the upper 200 m and used to determine the depth of the maximum chlorophyll a concentration and to model the euphotic zone depth at a depth of 100 m distinctly different hydrographic characteristics were observed between mesoscale features with cyclonic eddies consisting of subtropical surface water and anti cyclonic eddies containing tropical surface water from the indian ocean hydrographic properties at divergence and frontal stations reflected a mixture of these water masses while shelf stations showed considerable variability as a result of the interaction of eddies with the continental slope chlorophyll a concentrations in the surface waters were found to be low with subsurface levels being significantly greater phytoplankton biomass in cyclonic and anti cyclonic eddies was relatively low and not significantly different the interaction of mesoscale eddies with the continental slope on the western side of the channel caused upwelling of cooler nutrient rich water which resulted in elevated phytoplankton biomass in the shelf regions strong currents at the perimeters of these eddies produced offshore advection of the high biomass into the frontal regions

a connection between the south equatorial current north of madagascar and mozambique channel eddies 1 combining high resolution model output and geostrophic currents derived from satellite altimeter data it is shown that the formation of mesoscale eddies in the mozambique channel mzc is connected to variability in the transport of the south equatorial current sec lagged cross correlations of the currents north of madagascar and vorticities in the mzc combined with a composite analysis of the model output show that eddies form in the narrows of the channel approximately 20 weeks following a westward transport pulse in the sec a relationship between mzc eddies and the large scale variability of the south indian ocean may have downstream impacts on the agulhas leakage the atlantic meridional overturning circulation and thus climate

variability and coherence of the agulhas undercurrent in a high resolution ocean general circulation model abstract the agulhas current system has been analyzed in a nested high resolution ocean model and compared to observations the model shows good performance in the western boundary current structure and the transports off the south african coast this includes the simulation of the northward flowing agulhas undercurrent it is demonstrated that fluctuations of the agulhas current and undercurrent around 50 70 days are due to natal pulses and mozambique eddies propagating downstream a sensitivity experiment that excludes those upstream perturbations significantly reduces the variability as well as the mean transport of the undercurrent although the model simulates undercurrents in the mozambique channel and east of madagascar there is no direct connection between those and the agulhas undercurrent virtual float releases demonstrate that topography is effectively blocking the flow toward the north

fracture density in the deep subsurface techniques with application to point arguello oil field because monterey formation reservoirs rely on fractures joints for permeability quantitative information on fracture spacing is important to exploration strategies and for understanding reservoir behavior density of joints in cores of four wells from the point arguello reservoir has been determined with a new probability based method and these subsurface joint densities are compared with joint densities measured at nearby outcrops my measure of joint density is the fracture spacing index which is the slope of the trend of layer thickness to joint spacing a single set of extension joints that strike parallel to bedding dip predominates at outcrops likewise the cores contain a single set of extension joints perpendicular to the anticline axis and parallel to present day maximum horizontal compressive stress in core and at outcrop the only lithologic control on joint density is between nonjointed mudstone and harder more brittle jointed rocks within each well the fracture spacing index is the same for all hard rocks though it varies between wells in the reservoir joint density relates to structural position the most densely jointed strata fracture spacing index 0 45 are from the hinge of a minor anticline where its plunge steepens a less steeply plunging anticlinal nose has lower joint density fracture spacing index 0 30 the lowest joint density fracture spacing index 0 095 and 0 12 is in cores from gently dipping areas at outcrops in various structural settings the fracture spacing index is the same approximately 1 29 in chert dolostone and porcelanite and siliceous shale these rocks may be saturated with joints so that differences in brittle strain due to local structural variations have been overwhelmed as joints continued to form during unroofing of these strata chert looks more fractured than other lithologies because of thin bedding fracture spacing index is used to compute such parameters as fracture porosity and volume of fractures that directly contact the well bore these parameters may be important when trying to model the behavior of a petroleum reservoir or when trying to assess the feasibility of strongly deviating wells to improve the performance of a fracture reservoir

dynamics of the block island sound estuarine plume abstractbuoyant discharge of freshwater from long island sound lis forms a seasonal buoyant plume outside block island sound bis between the coast of long island and the denser shelf waters the plume s seasonal variability and its response to tides winds and surface heating are investigated through a series of process oriented experiments using the regional ocean modeling system roms results show the importance of river discharge wind directions and surface heating in the seasonal variation of the bis buoyant plume in winter and spring the plume is intermediate with a large surface offshore extension detached from the bottom from winter to spring the river discharge increases meanwhile upwelling favorable winds keep dominating they compete with the increase of surface heating and generate a broader buoyant plume in spring than in winter in summer the plume is bottom advected with most of its width in contact with the bottom and is featured with the steepest isopycnals and narrowest pl

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

on sverdrup discontinuities and vortices in the southwest indian ocean abstract the southwest indian ocean is distinguished by discontinuities in the wind driven sverdrup circulation these connect the northern and southern tips of madagascar with africa and the southern tip of africa with south america in an analytical barotropic model with a flat bottom the discontinuities produce intense westward jets those off the northern tip of madagascar and the southern tip of africa are always present while the strength of that off southern madagascar depends on the position of the zero curl line in the indian ocean the jet is strong if the line intersects madagascar but weak if the line is north of the island all three jets are barotropically unstable by the rayleigh kuo criterion the authors studied the development of the instability using a primitive equation model with a flat bottom and realistic coastlines the model produced westward jets at the three sites and these became unstable after several weeks generating 200 300 km scale eddies the eddies generated west of

on the origins of deep and bottom waters of the indian ocean the characteristics of the deep and bottom waters of the indian ocean when illustrated on potential density anomaly surfaces indicate that the waters enter from both the atlantic and pacific oceans the paths of spreading are constrained by the complex topography and characteristics are seen to be altered by exchange with the overlying and underlying water and with the sediments especially in the northern indian ocean the weddell sea contributes to the densest waters found in the western basins and the ross sea and adelie coast to the densest waters found in the eastern basins both dense water varieties are altered by and incorporated in the less dense water above initially water carried by the circumpolar current then water from the north atlantic and finally by deep water whose characteristics are derived in the northern indian ocean contact with the sediments increases the silica content of the bottom water in the southern ocean in the northern indian ocean the sediments alter the silica of the water at the bottom and together with enhanced salinity from diffusion of saline overflows from the marginal seas above imprint unique markers to the deep water that flows back to the south at middepths the series of ridges between madagascar and australia confine the flow to a series of gyres that carry characteristics from the circumpolar current equatorward and the northern indian ocean characteristics southward within the circumpolar current low oxygen deep water from the pacific is carried across the atlantic and into the indian ocean south of africa part flows around the cyclonic weddell sea gyre and part extends across the southern ocean water from another pacific source can be seen near 2000 m extending westward from the tasman sea south of aus tralia and across the indian ocean and perhaps to the aghulas current region southeast of africa in this study we show some maps of deep and bottom water characteristics of the indian ocean which may be used in a qualitative sense to infer pathways of spreading of water below a depth of about 2000 m the indian ocean has numerous ridges and basins figure 1 that severely restrict possible pathways of deep and bottom wa ter flow in the following we will begin by looking at char acteristics at the bottom of the ocean to reveal the path ways of spreading of the densest bottom waters from basin to basin then a series of six potential density anomaly surfaces at progressively shallower depths from about 4000 m up to about 2000 m will be shown to see what character istics influence the deep waters and how pathways of flow are constrained by the bathymetry of the indian ocean the choice of the specific density levels table 1 was based primarily on various property extrema shown by the 18os atlantis ii cruise 93 colored sections that accompany warren s 1981 detailed discussion of the major features of the central indian ocean between madagascar and aus tralia the sections approximately midway between antarctica and the northern indian ocean boundaries are well positioned to show features originating from both the north and the south as well as some brought into the indi an ocean by the antarctic circumpolar current the full ocean area isopycnal maps provide essential evidence on the origins and fates of features seen in the sections and

surface drifter trajectories highlight flow pathways in the mozambique channel abstract the pattern of surface circulation in the mozambique channel was elucidated from the trajectories of 82 satellite tracked drifters over the period 2000 2010 and complementary satellite derived altimetry overall the trajectories indicated that anticyclonic activity was mostly observed on the western side of the channel with cyclonic activity being more prevalent in the east a lack of eddy activity was noted in the southeast corner of the channel i e sw of madagascar drifter behaviour illustrated that surface water from the comoros basin entrained into anticyclonic eddies during formation can be retained and isolated for months whilst being transported southwards through the channel during a tropical cyclone weather event a drifter was observed to switch between counter rotating eddies indicating that horizontal mixing of the ekman layer does occur the drifters also illustrated and emphasised the flow field and transport between eddies i e the interstitial flow in the mozambique channel despite the dominance of southward propagating anticyclones drifters were able to move north and south through the channel in the frontal flow field between eddies within periods of 51 207 days cross channel transport in both directions between the madagascan and mozambique shelf regions was similarly observed with time spans of 19 30 days surprisingly drifters from the southern limb of the east madagascar current were transported westward across the channel to the mozambique shelf this transport was similarly facilitated by the frontal flow field between eddies it is hypothesised that the frontal zones between eddies and interstitial waters play an important role in distributing biota in the mozambique channel

multiple oscillatory modes of the argentine basin part i statistical analysis observations of the sea surface height in the argentine basin indicate that strong variability occurs on a time scale of 2030 days the aim of this study is to determine the physical processes responsible for this variability first results are presented from two statistical techniques applied to a decade of altimetric data a complex empirical orthogonal function ceof analysis identifies the recently discovered dipole mode as the dominant mode of variability a principal oscillation pattern pop analysis confirms the existence of this mode which has a period of 25 days the second ceof displays a propagating pattern in the northern argentine basin plus a rotating dipole in the southwest corner the pop analysis identifies both patterns as individual modes with periods of 30 and 20 days respectively second the barotropic normal modes of the argentine basin are studied using a shallow water model capturing the full bathymetry of the basin coherences between the spatial patterns of these modes and altimeter data suggest that several of the basin modes are involved in the observed variability this analysis implies that the 20 day mode detected by recent bottom pressure measurements is a true barotropic mode however the 25 day variability as found in altimeter data cannot be directly attributed to the excitation of a free rossby basin mode this study indicates that the results of several apparently conflicting observations of the flow variability in the argentine basin can be reconciled by assuming that multiple basin modes are involved