surface and borehole seismic methods to delineate kimberlite pipes in australia gravity magnetic and electromagnetic methods are primary exploration techniques used in kimberlite exploration to define a kimberlite pipe s location and shape sometimes these methods produce nonunique results because of weathering of the upper part of a kimberlite pipe and its considerable inhomogeneity complex pipe geometries and associated faulting and fracturing may be very difficult to assess by potential field methods application of seismic methods in kimberlite exploration has been limited in sedimentary basins however kimberlite pipes are likely to be a suitable target for the application of seismic reflection methods because of the difference in elastic properties between the pipe material and the host rock the drawback of surface seismic methods is that they are not designed for direct detection of vertical bodies such as a pipe however a kimberlite pipe may be inferred from seismic data indirectly by observing the termination of reflections against its flanks such an approach can produce good results if the sedimentary sequence is of moderate to high reflectivity unfortunately mcarthur basin sediments of the northern territory in australia are quite poor reflectors figure 1 the only reflecting horizon would probably be the sandstone black shale interface at 140 m near surface conditions are also unfavorable for surface seismic because of a thick layer of bull dust which causes poor geophone coupling hence very poor seismic data quality is typical for this area in this study instead of attempting a conventional surface seismic reflection approach we used modes generated by a kimberlite pipe to precisely determine its location the single borehole imaging sbi method also was used for delineation of the kimberlite pipe shape at depth by a combined analysis of p and s wave data recorded on the surface and in downhole experiments the pipe s location shape

petrogenesis of the late cretaceous northern alberta kimberlite province abstract at present 48 late cretaceous ca 70 88 ma kimberlitic pipes have been discovered in three separate areas of the northern alberta the mountain lake cluster the buffalo head hills field and the birch mountains field the regions can be distinguished from one another by their non archetypal kimberlite signature mountain lake or in the case of kimberlite fields primitive buffalo head hills to evolved birch mountains magmatic signatures the dominant process of magmatic differentiation is crystal fractionation and accumulation of olivine which acts as the main criteria to distinguish between primitive and evolved group i type kimberlite fields in the northern alberta this is important from the viewpoint of diamond exploration because the majority about 80 of the more primitive buffalo head hills kimberlites are diamondiferous whereas the more evolved birch mountains pipes are barren of diamonds for the most part petrographically the buffalo head hills samples are distinct from the birch mountains samples in that they contain less carbonate have a smaller modal abundance of late stage minerals such as phlogopite and ilmenite and have a higher amount of fresh coarse macrocrystal 0 5 mm olivine consequently samples from the buffalo head hills have the highest values of mgo cr and ni and have chemistries similar to those of primitive hypabyssal kimberlite in the northwest territories based on whole rock isotopic data the buffalo head hills k6 kimberlite has 87sr 86sr and end values similar to those of south african group i kimberlites whereas the birch mountains legend and phoenix kimberlites have similar end values between 0 and 1 9 but distinctly higher 87sr 86sr values 0 7051 0 7063 the lack of whole rock geochemical overlap between kimberlite and the freshest least contaminated mountain lake south pipe rocks reflects significant mineralogical differences and mountain lake is similar geochemically to olivine alkali basalt and or basanite intra field geochemical variations are also evident the k4 pipe buffalo head hills and xena and kendu pipes birch mountains are characterized by anomalous concentrations of incompatible elements relative to other northern alberta kimberlite pipes including chondrite normalized rare earth element distribution patterns that are less fractionated than the other kimberlite samples from the buffalo head hills and birch mountains the xena pipe has similar major element chemical signatures and high al clinopyroxene similar to or trending towards the mountain lake pipes in addition k4 and kendu have higher 87sr 86sr and lower end than bulk earth and plot in the bottom right quadrant of the nd sr diagram we suggest therefore that the k4 and kendu pipes contain a contribution from old lree enriched low sm nd lithosphere that is absent from the other kimberlites are affected by crustal contamination or both based on xenocryst populations the northern alberta kimberlite province mantle is dominated by carbonate saturated lherzolitic mantle higher levels of melt depletion characterize the buffalo head hills mantle sample despite high diamondiferous to barren pipe ratios in the buffalo head hills pipes mineral indicators of high diamond potential such as g10 garnet diamond inclusion composition chrome spinels and high sodium eclogitic garnet are rare

chronology of warm core ring 82b a chronology constructed from satellite derived thermal imagery is presented to describe the formation and life history of warm core ring 82b this overview provides insight into a classification of features and discrete events associated with gulf stream warm core rings and allows these events as well as our limited shipboard observations to be placed in a broader spatial and temporal context than would otherwise be possible without the satellite data events influencing the evolution of 82b include environmental factors such as meteorological influences and gulf stream interactions as well as those stimulated by encounters with changes in bottom topography the interactions of the ring with surrounding waters are especially noteworthy and the existence of vortex vortex interactions is shown to be a significant cause of local water advection through streamer activity ring events are documented by following changes in ring size shape translation and surface thermal structure our satellite observations are supported by extensive contemporaneous shipboard observations including xbt ctd bops biooptical profiling system temperature profiles and along track sea surface temperature measurements in addition acoustic velocity profiling and drifter trajectories have been used to corroborate hydrographic features of the ring and environs these ship and satellite data form a coherent space time overview of the ring and its environment and show them to be closely related and continually interacting

observations of gulf stream ring 83 e and their interpretation using feature models analysis techniques were developed to track and estimate the propagation velocity size shape orientation and swirl velocity of gulf stream warm core rings the methods involve fitting idealized warm core ring feature models to observed surface fronts in the satellite imagery to expendable bathythermograph survey data and to satellite tracked drifting buoy data the ring feature models are analytic structure functions with adjustable parameters in this case the ring is modeled as an isolated translating elliptic paraboloid with a swirl velocity that increases linearly with distance from the center use of the feature models is illustrated with data collected from warm core ring 83 e gradient currents based on the bathythermograph survey of ring 83 e and the feature model agree well with currents measured by expendable current profilers a comparison of the time series of ring 83 e feature model parameters indicates that not only is the feature model analysis of the buoy track an effective method for tracking and monitoring the evolution of gulf stream rings it also provides useful forecasts of ring locations based simply on a persisted propagation velocity these techniques were used to provide real time support for exploratory deepwater drilling operations off the u s east coast

seismic delineation of the orion south kimberlite fort a la corne canada abstractthe orion south 140 141 kimberlite is a diamondiferous multiphase volcano sedimentary complex within the cretaceous fort a la corne kimberlite field of saskatchewan canada a network of seven high resolution 2d seismic reflection profiles were acquired to test the utility of using seismic methods in defining the subsurface architecture of the kimberlite complex and to provide auxiliary constraints on interborehole geologic correlations the seismic data were interpreted in conjunction with a set of drillhole geologic logs and associated geologic sections and models and physical rock properties from core measurements and geophysical logs core determined average density values for the kimberlite suite are low 2240 16 kg m3 but with some kimberlite facies having significantly higher values 2330 to 2540 kg m3 sonic velocities for the kimberlites are 2500 3500 m s as compared with 2000 m s and 3800 4500 m s for the enveloping shale and sandstone units respectively the kimberlite is

mapping gulf stream warm core rings from shipboard adcp transects of the oleander project 1 the flow patterns of the gulf stream warm core rings and surrounding shelf break and slope water are constructed from shipboard acoustic doppler current profiler adcp transects of the oleander project for each warm ring consecutive adcp transects are colocated to a common ring center and are mapped into a stream function methods to locate ring centers from the adcp transect and advanced very high resolution radiometer image are developed and tested two warm rings in 1999 which have relatively complete data coverage are examined to study the ring induced warm and cold streamers for cold streamers the estimated volume flux based on more than 10 independent adcp transects is at least 1 106 m3 s 1 this result agrees well with the previous estimate in the warm core ring experiment for warm streamers the result is new on the basis of a large number of adcp transects the estimated volume flux is about 2 5 106 m3 s 1 by pulling large transports associated with the cold warm streamers the warm rings likely play a fundamental role in the water exchange in the slope sea

deep electrical structure of northern alberta canada implications for diamond exploration geophysical studies of upper mantle structure can provide constraints on diamond formation teleseismic and magnetotelluric data can be used in diamond exploration by mapping the depth of the lithosphere asthenosphere boundary studies in the central slave craton and at fort a la corne have detected conductors in the lithospheric mantle close to or beneath diamondiferous kimberlites graphite can potentially explain the enhanced conductivity and may imply the presence of diamonds at greater depth petrologic arguments suggest that the shallow lithospheric mantle may be too oxidized to contain graphite other diamond bearing regions show no upper mantle conductor suggesting that the correlation with diamondiferous kimberlites is not universal the buffalo head hills in alberta host diamondiferous kimberlites in a proterozoic terrane and may have formed in a subduction zone setting long period magnetotelluric data were used to investigate the upper mantle resistivity structure of this region magnetotell

oxygen isotope systematics of the precambrian basement of alberta implications for paleoproterozoic and phanerozoic tectonics in northwestern alberta we have conducted a regional survey of the oxygen isotope compositions of drill core samples from the precambrian basement of the alberta sedimentary basin the majority of samples have whole rock 18o smow values between 7 and 11 as is typical of crustal rocks however there are also a significant number of samples with 18o values less than 5 in these samples high grade minerals such as pyroxene amphibole and biotite commonly show retrograde alteration to chlorite and or epidote the majority of low 18o samples are from a 250 x 50 km zone in northwestern alberta which we refer to as the kimiwan isotope anomaly the anomaly is significant in that the most reasonable explanation for generating such a laterally extensive zone of rocks with 18o values below 5 is through high temperature interaction with surface derived fluids in an extensional tectonic setting we propose therefore that the low 18o samples define a hitherto unrecognized extensional zone in the alberta basement avai

the rhine outflow plume studied by the analysis of synthetic aperture radar data and numerical simulations the dynamics of the rhine outflow plume in the proximity of the river mouth is investigated by using remote sensing data and numerical simulations the remote sensing data consist of 41 synthetic aperture radar sar images acquired by the first and second european remote sensing satellites ers 1 and ers 2 over the outflow region of the river rhine most of them show sea surface signatures of oceanic phenomena for example surface current and wind variations ship wakes and oil slicks in particular in 36 of these images pronounced frontal features are visible as narrow zones of mainly enhanced sometimes enhanced reduced radar backscatter that can be associated with the rhine surface front within the area enclosed by the frontal line large zones characterized by a lower radar backscatter than in the outer area are often visible the analysis of the ers sar images suggests that the form and the location of the frontal features are mainly linked to the semidiurnal tidal phase in the outflow region although their variability suggests also that they weakly depend on river discharge residual currents and neap spring tidal cycle in order to test this observational hypothesis the results obtained from the analysis of the ers sar images are compared with the results obtained from the numerical simulation of the hydrodynamics of the rhine outflow region carried out using a two layer frontal model which is based on the nonlinear hydrostatic shallow water equations on an f plane the model is forced by prescribing tidal and residual currents and river discharge at the open boundaries several simulations are performed by varying the values of these forcing parameters the numerical results corroborate the observational conjecture it is found that the form and the location of the simulated interface outcropping lines in the proximity of the river mouth are mainly determined by the semidiurnal tidal phase in the outflow region and that river discharge residual currents and neap spring tidal cycle contribute only secondarily to their determination inserting the simulated surface velocity field into a simple radar imaging model that relates the modulation of the backscattered radar power to the surface velocity convergence in radar look direction narrow elongated bands of enhanced radar backscatter emerge near the model frontal line while patches of low radar backscatter appear within the simulated rhine plume area the consistency of the model results with the results obtained from the analysis of the sar images enables one to infer a mean spatial and temporal evolution of the rhine outflow plume over a semidiurnal tidal cycle from the analysis of spaceborne sar images acquired during different tidal cycles over the rhine outflow area and suggests the possibility of using numerical modeling in conjunction with the analysis of spaceborne measurements for monitoring the oceanic variability in the rhine outflow area

canadian kimberlites geological characteristics relevant to emplacement in canada more than 770 kimberlites have erupted in diverse tectonic settings over a period of 1000 ma and over an area at least 5000 km across the kimberlites represent at least 30 comagmatic fields one pipe type dominates each of the different kimberlite fields even with the discovery of a significant number of new kimberlite fields this review of recent data substantiates the previous proposal that there are at least three distinct classes of kimberlite pipes which show a correlation with the nature of the country rocks into which they were emplaced new data show that a variation on the prairies pipe type occurs when kimberlites were emplaced into competent paleozoic sediments resulting in steeper sided pipes infilled with similar pyroclastic kimberlite new data for each pipe type are summarised and the contrasting characteristics of the three pipe types are considered to reflect fundamentally different styles of eruption and deposition apparently uniform near surface olivine and volatile rich kimberlite magmas were modified differently during the contrasting emplacement processes resulting in distinct textural rock types pyroclastic kimberlite pk tuffisitic kimberlite tk and associated hypabyssal kimberlite hk or resedimented kimberlite rvk dominating each type of pipe the substantiated correlation of pipe type with country rock geology could indicate variable constraints on volatile exsolution which affected the nature of the magmatic eruptions in different settings

deep rifts as sources for alkaline intraplate magmatism in eastern north america intracontinental magmatism in eastern north america does not exhibit the regular time progression associated with mantle plume activity instead the magmatism is sporadic but locally persistent suggesting that the magmas rise from a mantle source that drifts with the continental plate a spatial association with ancient rifts further suggests that this source is fertile9 melt generating material emplaced in the mantle lithosphere during the early stages of rifting

warm core ring dynamics derived from satellite imagery a reinterpretation of the life history of warm core ring 82 b is constructed from drifter trajectories hydrographie profiles and satellite derived sea surface temperature fields an analysis of the observations strongly suggests this ring is fundamentally a dipole structure for much of its existence the dipole has unequal strength vortices with the cyclone being the weaker component quantification of the dipole indicates the anticyclone is oval shaped and rotates at approximately 7 7 per day while the cyclone revolves around the anticyclone at about 14 5 per day yielding an orbit period of approximately 25 days for the cyclone the elusive part of the dipole explanation is in interpreting its surface signature as a function of time as the cyclone appears to disappear when in proximity to the steep continental slope vortex modeling suggests that when the weaker cyclonic eddy is placed close to a boundary the cyclone is drawn into a filament as it is advected through the gap between the anticyclone and the boundary this means the cyclone is either in a filamentation state or undergoing the straining associated with filamentation approximately three fourths of the time which is in complete agreement with the satellite imagery in addition the 82 b dipole configuration is sufficiently robust to survive continuous interaction with the continental slope and the onset of a gulf stream interaction although only warm core ring 82 b is analyzed in detail and found to be a vortex pair dipole configurations are found in the warm core ring 81 f time series as well

some characteristics of yakutat eddies propagating along the continental slope of the northern gulf of alaska abstract data from array for real time geostrophic oceanography argo profiling floats oil tanker thermosalinographs shipboard adcp and towed ctd surveys and satellite altimetry are used to examine properties of two 200 km diameter anticyclonic yakutat eddies that propagated westward at 1 5 km day 1 along the continental slope of the northern gulf of alaska goa in 2001 and 2003 the eddies had lifetimes of up to 5 years remained close to the shelfbreak and had relatively constant size and strength until they encountered the alaskan stream where they appeared to spawn smaller shorter lived anticyclones the azimuthal velocity field was vigorous 25 40 cm s 1 and in gradient wind balance with rossby numbers of 0 05 conservation of salt and azimuthal mass transports between 20 m and the depth of the 32 2 isohaline from shipboard surveys in may and august 2003 suggest little mass exchange occurred between the surface layers of the eddy and ambient waters chlorophyll concentrations were greater in the eddy than in ambient waters in both may and august in may the chlorophyll was patchily distributed while in august dense chlorophyll concentrations occurred in and beneath the seasonal thermocline within 50 km of the eddy center the high august chlorophyll concentrations might have been fostered by a broad and shallow it appears likely that as yakutat eddies approach the shelfbreak non linear processes will modify the slope flow field and the stability and structure of the shelfbreak front leading to cross slope flows and flow reversals this interaction may induce 30 km wide streamers of shelf water to flow around the trailing edge of the anticyclone the role of streamers in the freshwater and nutrient budgets of the goa shelf and basin is unknown but their contribution to these budgets will depend on the trajectory of a yakutat eddy especially its proximity to the shelfbreak as the eddy propagates along the goa continental slope

influence of a gulf stream warm core ring on water mass and chlorophyll distributions along the southern flank of georges bank during late spring 1997 a gulf stream warm core ring wcr strongly in uenced water mass and chlorophyll distributions along the southern ank of georges bank entrainment of georges bank shelf water by the wcr centered at the central southern ank persisted through may by late may shelf water encircled nearly the entire wcr and horizontal convergence toward the central southern ank was evident scotian shelf water ssw extended across northeast channel onto georges bank near the northeast peak and along the southern ank between the 60 m isobath and the shelfbreak front ssw extended furthest southwest along the southern ank shelfbreak satellite imagery from the ocean color and temperature sensor octs showed that by late may in addition to the high chlorophyll concentrations within the entrained shelf water encircling the wcr pigment rich bands of chlorophyll developed along the 60 and 100 m isobaths where this biological enhancement developed along 100 km of the shelfbreak 100 m isobath shelf waters extended furthest seaward due to entrainment by the wcr the enhanced shelfbreak chlorophyll was sampled in situ along two transects separated by 40 km along shelf along both transects the enhanced chlorophyll coincided with divergent cross shelf ow maximum along shelf ow and minimum surface temperature coincidence of the highest surface chlorophyll and lowest surface temperature with divergent cross shelf ow is consistent with upwelling coincidence with along shelf jets and their associated vertical shear is consistent with turbulent vertical mixing the importance of turbulent vertical mixing was supported maximum velocity at the shelfbreak coincided with the subsurface temperature minimum of ssw near 30 m depth estimated gradient richardson numbers ri above the ssw were below critical 0 25 within the shelfbreak chlorophyll maximum along both transects and surface chlorophyll was signi cantly inversely correlated with ri along the southern ank wcr entrainment of shelf water continued into june as

organics versus clastics conditions necessary for peat coal development abstract the absence or lack of detrital influx into ancient peat forming swamps is critical to the formation of low ash coal modern and ancient coal forming swamps of continental basins show a separation of peat and clastic sediments which is partially fault controlled in the african rift valleys as well as in the stephanian intermontane coal basins of france thick peat free from clastic input may be the result of tectonic activity in the paralic basins of morocco westphalian b and nigeria late cretaceous coal occur landward of the shoreline turnaround and are related to a relative high stand of the sea which curtailed detrital influx into the basins thus peat formation occurred during an early transgressive phase

potential field signatures of buried precambrian basement in the western canada sedimentary basin an internally consistent levelled compilation of magnetic data is derived for alberta and northeastern british columbia with bouguer gravity data this compilation is used to refine the definition of precambrian basement domains within the western canada sedimentary basin magnetic data are draped at a constant distance above the mapped basement surface to reduce the effects of varying magnetic source depths automated interpretation methods that effectively map outlines of magnetic sources are used to characterize the internal structure of the domains and to aid in their delineation the basement domain map thus derived differs from previous interpretations in the extension of domains further to the southwest due mainly to the availability of new public domain magnetic data and the more precise definition of domain boundaries based on the magnetic source location maps the nahanni hottah chinchaga thorsby vulcan and kiskatinaw domains are weakly magnetic and characterized by magnetic sources tha

wintertime convection in warm core rings thermocline ventilation and the formation of mesoscale lenses large heat losses from warm core ring 82b during february march and april 1982 formed a 400 m thick thermostad in the center of the ring two different models were constructed to simulate the formation of the thermostad water mass properties a one dimensional vertical model forced with a meteorological time series and a volumetric mixing model with climatological input both models indicate that a flux of slope water into the ring is necessary to yield the observed thermostad salinities the subsequent slow decay of the ring core in the slope water suggests that such winter convected rings can easily maintain the warm band water identified by wright and parker 1976 the large loss of core water during interactions with the gulf stream suggests that the reabsorption of such winter cooled warm rings is an important source of high salinity high oxygen anomalies in the main thermocline of the sargasso sea the volume of water in a typical ring reabsorption is sufficient to generate many 20 intrathermocline eddies with t s properties close to those of recently reported lenses this suggests that many of these small eddies are much more local in origin and may be more highly dissipative than has previously been suggested an estimate of the flux of high salinity high oxygen water into the main thermocline by this mechanism leads to ventilation at a rate that is a significant fraction of the ekman pumping at these density levels thus the reabsorption of winter cooled warm core rings by the gulf stream is an important eddy ventilation mechanism for the sargasso sea

amplification of a surface intensified eddy drift along a steep shelf in the eastern mediterranean sea abstract the datasets of the eddies and gyre path tracking egypt egitto program in the eastern mediterranean sea reveal a large mesoscale anticyclone traveling along the libyan shelf surface drifter trajectories combined with a ctd transect accurately quantify the horizontal velocity and the vertical structure of this surface intensified anticyclone the observed westward drift speed is significantly higher than expected from the beta effect alone to study the impact of a steep shelf topography on the propagation of compact surface intensified vortices the authors used a two layer beta plane model with steep continental slope and nearly zonal boundary a perturbation theory derived by g sutyrin for a circular vortex in the upper layer with the lower layer at rest as a basic state is generalized for nonuniform slope in the presence of the image effect an integral momentum balance is used to derive the drifting velocity of an upper layer vortex with the main assumption that a stable and steady drifti

the subglacial geomorphology of southeast alberta evidence for subglacial meltwater erosion a coherent pattern of landforms in southeast alberta forms a subglacial landform continuum scoured bedrock tracts flutes transverse bed forms and tunnel channels in this continuum are inferred to be products of erosion by turbulent subglacial meltwater flows beneath the laurentide ice sheet bedrock and glacigenic sediment are truncated by an erosional surface flutes and extensive boulder lags across the truncation surface strongly suggest erosion by high velocity turbulent flows tunnel channels dissect the erosion surface and record channelization of earlier sheet flows convex longitudinal profiles of channels indicate subglacial meltwater flow northeast southwest trending transverse bed forms are superimposed on the preglacial divide and may be either glaciotectonic ridges or fluvial bed forms landforms reflect the dominance of erosion in the subglacial environment likely by catastrophic meltwater flows of the livingstone lake megaflood event the subglacial meltwater hypothesis accounts for e

kimberlite sourced bentonite its paleoenvironment and implications for the late cretaceous k14 kimberlite cluster northern albertathis article is one of a selection of papers published in this special issue on the theme geology of northeastern british columbia and northwestern alberta diamonds shallow gas gravel and glaciers kimberlite sourced bentonite layers have been discovered in late cretaceous sedimentary drill cores located within the buffalo head hills kimberlite field north central alberta two bentonites are unambiguously differentiated from common intermediate to felsic volcanic derived alberta bentonite by having similar whole rock geochemical composition to ultramafic rocks from the buffalo head hills kimberlite field and worldwide crater facies kimberlite the results demonstrate that the geochemical analysis of bentonite can provide a quick cost effective means of testing for low volume kimberlite volcanism the kimberlite sourced bentonite is associated with a cluster of buffalo head hills kimberlites known as the k14 complex the k14a kimberlite occurrence has a previously reported 206pb 238u perovskite emplacement age of 86 8 2 1 ma this age is compatible with early or mid cenomanian 99 96 ma and mid coniacian to santonian 88 84 ma palynological results for mudstone underlying and bracketing the

rapid evolution of a gulf stream warm core ring gulf stream warm core rings form in the slope water between the north american continental shelf and the gulf stream by the separation of a north extending meander1 the initial physical chemical and biological properties of the core of these 100 200 km eddies are often similar to those of its parent water mass the sargasso sea a clockwise rotating remnant of the gulf stream circulates around the core with surface current speeds of 50 200 cm s 1 although warm core rings can slowly change over periods of months through interactions with the surrounding slope water gulf stream meanders continental slope other rings and the atmosphere we have now discovered that major alterations to ring structure can occur during very short periods 2 5 days when an interaction with the gulf stream is particularly intense such short period interactions between a ring and the gulf stream are a major factor governing a ring s evolution

detecting the surface salinity signature of gulf stream cold core rings in aquarius synergistic products new sea surface salinity sss observations derived from satellite remote sensing platforms provide a comprehensive view of salt exchanges across boundary currents such as the gulf stream the high resolution 45 km spatial resolution and 3 day repeat subcycle of the soil moisture and ocean salinity smos observations allows detection and tracking of meander and ring structures of the gulf stream from sss maps these structures are however not resolved by the relatively lower resolution 100 km and 7 day repeat subcycle of aquarius observations a recently developed fusion technique based on singularity analysis is applied in this study to reconstruct these mesoscale from 100 km and 3 days features in aquarius derived products new quarter degree sss maps are obtained by fusing aquarius data with three different geophysical templates sea surface height ssh from aviso sss from smos and sea surface temperature sst from avhrr the proposed method exploits the theoretical correspondence among the singularity exponents of different maps of ocean surface remotely sensed scalar fields the analysis results over the year 2012 show that merging aquarius with ssh data provides a series of negative salinity anomalies that better collocate with the position of the cyclonic eddies identified from sea level anomaly maps this result is consistent with the hypothesis that this sla derived cyclonic eddies in this area are indeed ccrs shed off the gs

detailed topography of the devonian grosmont formation surface from legacy high resolution seismic profiles northeast alberta abstractthe devonian grosmont formation in northeastern alberta canada is the world s largest accumulation of heavy oil in carbonate rock with estimated bitumen in place of 64 5 109 m3 much of the reservoir unconformably subcrops beneath cretaceous sediments this is an eroded surface modified by kartstification known as the sub mannville unconformity smu we studied the reanalysis and integration of legacy seismic data sets obtained in the mid 1980s to investigate the structure of this surface standard data processing was carried out supplemented by some more modern approaches to noise reduction the interpretation of these reprocessed data resulted in some key structural maps above and below the smu these seismic maps revealed substantially more detail than those constructed solely on the basis of well log data in fact the use of only well log information would likely result in erroneous interpretations although features smaller than about 40 m in radius cannot be easily discerned at the smu

satellite and hydrographic observations of low frequency wave motions associated with a cold core gulf stream ring thermal infrared data from the noaa polar orbiting satellite and hydrographic observations from surface ships are used to estimate the eccentricity and the rotation rate of wavelike perturbations around the circumference of a gulf stream cyclonic eddy in april 1977 from the satellite data the rotation rate is estimated at 4 4 0 1 10 6 s 1 for the period april 8 16 estimates of are obtained from the trajectory of satellite tracked drifters and from changes in the sea surface temperature fields determined from expendable bathythermograph trace xbt surveys a simple eady model suggests the perturbations are stable modes of azimuthal wave number 2

modeling of two layer eddies and coastal flows with a particle method an existing particle in cell pic numerical method developed for the study of two layer mesoscale motions with outcropping pycnocline is applied to lens like anticyclonic vortices and buoyant coastal currents from a first series of experiments investigating the evolution of an initially elongated lens like anticyclone it is found that motions induced in the lower layer act only to increase the rotation of the vortex structure and do not appear to affect the process of eccentricity reduction partial axisymmetrization eccentricity reduction if any produces a final vortex of aspect ratio between 1 8 and 1 9 a value that is very close to the stability threshold of large reduced gravity lenses a second series of experiments devoted to vortex mergers determines how the maximal separation distance for which two circular anticyclonic lenses merge spontaneously varies with vortex size ratio of lens radius to deformation radius and stratification ratio of lens central thickness to ocean depth a third series of experiments considers the interaction of a lens vortex in the upper layer with a potential vorticity anomaly in the lower layer second hand relative vorticity generated in the lower layer under the action of vertical stretching induced by the movement of the upper layer vortex interacts with first hand relative vorticity created by the existing potential vorticity to create effects similar to those predicted by studies of two layer point vortices hetons finally the pic method is generalized to simulate the finite amplitude instability of a buoyant geostrophic hydrostatic intrusion flowing along a vertical coastal wall those results however are reported here more as a demonstration on how the pic method can be extended to include coastal boundaries than as a thorough investigation of coastal current instabilities

tropical instability vortices in the atlantic ocean 1 this paper examines the physical characteristics and dynamics of atlantic tropical instability vortices based on observational data from 1997 to 2000 and a high resolution numerical model simulation most prominent during boreal summer the vortices are characterized by 400 km spatial scales westward translation at 0 40 cm s 1 anticyclonic circumferential velocities of 30 110 cm s 1 and sstanomalies that decrease from 2 ci n midbasin to 0 5 c or less near the western boundary in contrast the sea level anomalies grow as the vortices progress westward reaching maximum amplitudes of 14 cm near 40 w the large circumferential velocities leading to relative vorticities of 4 10 6 s 1 and rossby numbers of 0 5 indicate that centrifugal effects may play an important role in the vortices vorticity balance we address the vortices vertical structure and vorticity dynamics by examination of a high resolution numerical model there is a reasonably good agreement between the model and observations simulated vortices are confined mostly to the mixed layer which increases westward in depth from 30 to 100 m near the western boundary in the eastern basin potential vorticity within the vortices is not conserved but decreases because of wind stress forcing in contrast in the western basin decreases in potential vorticity are due mostly to the vortices acquisition of southern hemisphere water we estimate an annualized cross equatorial transport of up to 1 2 sv associated with the vortices which is eventually contributed to the north brazil current system index terms 4231 oceanography general equatorial oceanography 4520 oceanography physical eddies and mesoscale processes 4528 oceanography physical fronts and jets keywords tropics instability atlantic

small scale cyclones on the periphery of a gulf stream warm core ring small scale cyclones found around gulf stream warm core ring 82b are investigated by using infrared satellite images and current information obtained with an acoustic doppler velocimeter currents in these cyclones reveal speeds ranging from 20 to 80 cm s one small cyclone or ringlet found in june 1982 was studied extensively by removing the basic rotational velocities of 82b the azimuthal velocity field for this ringlet was used with the gradient current equation to calculate the absolute dynamic topography at 100 dbar it was found that the ringlet was 13 dyn cm lower than its surroundings in addition neglect of the centrifugal term would have changed the dynamic topography of the ringlet by 30 from a comparison with ctd data the absolute reference level was determined and a vertical profile of horizontal currents was calculated for the ringlet other cyclones were found throughout the slope water region around warm core ring 82b with observable lifetimes of 1 to 2 weeks the northeast quadrant of 82b was a favored generation site for ringlets two cyclones were observed to form in this region and were advected anticyclonically around 82b typically at any one time six cyclones with diameters of approximately 40 to 50 km can be detected north of the gulf stream by using satellite images

rings in the ocean certain robust long lived eddy features in t he world s ocean have come to be k nown as rings the nomenclature stems from fuglister 1 1972 who c oined t he name based on the c ircle or ring of gulf stream waters t hat surrounded a class of eddies formed from t he g ulf stream through the pinch off of meanders here it s uffices to define rings as intense eddies or vortices that represent a wrapped up piece of a major ocean c urrent they t ranslate over space scales of hundreds to thousands of k ilometers and exist for periods lasting from months to years rings move t hrough the ocean carrying anomalies s imilar to the contrasts in physical biological and chemical properties observed across the major ocean c urrents while the term ring is t ied to fuglister t he existence ofthese features was evident at least as early as t he 1930s when iselin 2 1936 1940 encountered strong cold anomalies in the region south of the gulf stream that we would identify as c old corc cyclonic rings today iselin fully rec ognized these features as part of the highly time dependent eddy motion in the ocean later iselin fuglister 1948 were the first to survey what is now k nown as a warm core anticyc lonic ring there are tw o types of rings cold core rings are made up of w aters from the poleward s ide of c urrents like the gulf stream that are introduced to

222rn surpluses in warm core rings measurements of 222rn and 226ra were made in the western atlantic ocean as part of the warm core rings program a significant number of measurements on waters taken from the surface and deeper waters showed 222rn concentrations in excess of those supported by the parent 226ra since the source of these 222rn surpluses is near bottom shelf or slope water and since the half life of 222rn is only 3 8 days such 222rn surpluses are indicative of rapid offshore advective and or mixing processes concentrations of 226ra exhibit a small but measurable increase when moving from the sargasso sea through the slope water and up onto the shelf

a revised crustal stress orientation database for canada abstract the canadian database on contemporary crustal stress has not been revised systematically in the past two decades here we present the results of our new compilation that contains 514 new data records for the orientation data of maximum compressive horizontal stress and 188 data records that were re assessed in total the canadian stress database has now 1667 data records which is an increase of about 45 from these data a new canadian stress map as well as one for the province of alberta is presented to analyse the stress pattern we use the quasi median on the circle as a smoothing algorithm that generates a smoothed stress map of the maximum compressive horizontal stress orientation on a regular grid the newly introduced quasi interquartile range on the circle estimates the spreading of the data and is used as a measure for the wave length of the stress pattern the result of the hybrid wavelength analysis confirms that long spatial wavelength stress patterns 1000 km exist in large areas in canada the observed stress pattern is transmitted through the intra plate regions the results reveal that shorter spatial wave length variation of the maximum compressive horizontal stress orientation of less than 200 km prevails particularly in south eastern and western canada regional stress sources such as density contrasts active fault systems crustal structures etc might have a significant impact in these regions in contrast to these variations the observed stress pattern in the alberta basin is very homogeneous and mainly controlled by plate boundary forces and body forces the influence of curvature of the rocky mountains salient in southern alberta is minimal the present day horizontal stress orientations determined herein have important implications for the production of hydrocarbons and geothermal energy in the alberta basin

approximating edges of source bodies from magnetic or gravity anomalies cordell and grauch 1982 1985 discussed a technique to estimate the location of abrupt lateral changes in magnetization or mass density of upper crustal rocks the final step of their procedure is to identify maxima on a contoured map of horizontal gradient magnitudes we attempt to automate their final step our method begins with gridded magnetic or gravity anomaly data and produces a plan view of inferred boundaries of magnetic or gravity sources the method applies to both local surveys and to continent wide compilations of magnetic and gravity data e g zietz 1982 simpson et al 1983a kane et al 1982

particulate manganese dynamics in gulf stream warm core rings and surrounding waters of the n w atlantic manganese has been measured in size fractionated paniculate matter profiles obtained by large volume in situ filtration of the upper 1000 m of the n w atlantic as part of the warm core rings experiment wcre in 1982 environments sampled included warm core rings wcr 82b and 82h the entrainment zone at the edge of these rings the slope water surrounding rings and the gulf stream gs and sargasso sea ss from which the rings formed manganese concentrations ranged from 10 pmol kg 1 to 10 000 pmol kg 1 with the extreme values observed in the quasi isolated core waters of wcr 82b and in a tongue of shelf water at the periphery of wcr 82b respectively the majority of the mn was in the 1 53 m particle size fraction and most mn was probably close to 1 m in size mn showed no correlation with major biogenic phases indicating that formation by local biological processes was not an important source instead most paniculate mn present in the waters sampled originated in reducing sediments at the continental margin a manganese budget for the quasi isolated core waters of wcr 82b between february and june 1982 showed that most mn removal was by the aggregation of the small mn oxyhydroxide particles into fecal material followed by sedimentation calculations show that wcrs cause offshore particulate mn transports from the continental margin between 66 w and cape hatteras of 8 5 104 to 14 104 mol d 1 with most derived from the continental shelf only 4 of the shelf derived mn becomes entrained into wcrs and the rest is left to disperse in the slope water or enter the circulation of the gulf stream the wcr induced offshore mn transports may account for a large fraction of the mn flux to sediments on the continental slope and upper continental rise

behavior of the ocean radar cross section at low incidence observed in the vicinity of the gulf stream observational results derived from the airborne c band scatterometer ressac looking at small incidence angles spl les 21 spl deg were acquired in the vicinity of the gulf stream during the surface wave dynamics experiment in february and march 1991 although the instrument was primarily designed to study the directional spectra of long waves it is also possible to process the data to examine the behaviour of the radar cross section spl sigma sup 0 versus incidence spl theta and azimuth spl phi although the classical physical or empirical models of spl sigma sup 0 spl theta spl phi predict that the anisotropy of spl sigma sup 0 versus azimuth increases with wind speed for a given incidence angle spl theta it is found that under some conditions this behaviour does not occur by contrast the anisotropy shows strong minima on certain occasions given the high resolution upper ocean current measurements from airborne expendable current profilers deployed on 5 march 1991 the regions of anisotropic minima could be identified from the three sets of observations march 4 5 and 7 downwind of the core of the gulf stream with a maximum current of 2 m s sup 1 and downwind of the current speed maxima of an anticyclonic rotating warm core ring juxtaposed along the north wall on three other days february 27 march 2 and 6 no clear anisotropic minima of was found because the upper ocean current effects were obscured by variability in surface wind field

seismic imaging through the volcanic rocks of the snake river plain insights from project hotspot hotspot the snake river geothermal drilling project was undertaken to better understand geothermal systems across the snake river plain volcanic province a series of surface and borehole seismic profiles were obtained to provide insights into volcanic stratigraphy and test the capabilities of engineering scale seismic imaging in such terranes the kimberly site drilled through 1 9 km of mostly rhyolite with thin sedimentary interbeds in the upper part of the section the kimama site drilled through 1 9 km of mostly basalt with sedimentary interbeds at 200 m depth and 1700 m depth the mountain home site contained numerous sediment and volcanic rock layers downhole and surface vibroseis seismic results suggest sedimentary interbeds at depth correspond with low velocity high temperature zones that relate to reflections on seismic profiles our results suggest that eruption flow volumes can be estimated and flow boundaries can be imaged with surface seismic methods using relatively high fold and wide angle coverage high frequency attenuation is observed at all sites and this deficit may be countered by acquisition design and a focus on signal processing steps separation of surface and body waves was obtained by muting and the potential for large static effects was identified and addressed in processing an accurate velocity model and lithology contacts derived from borehole information improved the confidence of our seismic interpretations

a comparison of a hydrodynamic lens model to observations of a warm core ring analysis of advanced very high resolution radiometer satellite images has shown long period fluctuations in ring eccentricity for 82 b concurrent shipboard measurements as well as satellite data also suggest that this anticyclonic ring was often paired with one or more cyclonic eddies furthermore satellite image analysis and recent numerical simulations suggest strong deformation in the fluid between the anticyclone and the cyclone the purpose here is to investigate a causal relation between the time dependent environmental deformation and the eccentricity fluctuations to this end we attempt to parameterize the effects of the cyclone as environmental forcing on the anticyclone using a nonlinear non quasi geostrophic hydrodynamic lens model our results suggest that the strong deformation in the environmental flow could be responsible for long period fluctuations in eccentricity other model ring features such as spin vorticity 2 and rotation rate of 82 b are discussed and compared to observations another significant feature of the model results is the presence of superinertial frequencies in the solution fields since current mesoscale observation techniques are unable to resolve such high frequencies it is unknown whether or not this result is realistic

modification of surface winds near ocean fronts effects of gulf stream rings on scatterometer quikscat nscat wind observations 1 modifications to surface winds by currents and sea surface temperature sst gradients near frontal boundaries of gulf stream rings are analyzed using satellite sst and scatterometer nasa s quick scatterometer quikscat nasa scatterometer nscat wind observations a component of scatterometer wind approximately equal and opposite to the surface current vector is observed and attributed to the fact that scatterometers detect relative motion of water and air warm core ring wcr ssts act to destabilize the marine atmospheric boundary layer mabl increasing surface wind magnitude by 10 15 and decreasing veering angle by 5 15 relative to large scale mean winds cold core ring ccr ssts cause impacts of similar magnitude and opposite sense magnitudes and directions of modifications are accounted for by mabl dynamics of a nonlinear planetary boundary layer model forced by air sea temperature differences wind modifications occur within tens of kilometers of sst fronts implying a wind response timescale of order 1 hour by contrast uniformity of modified winds across the larger area within rings suggests the response time for the mabl to return to equilibrium downstream from a front exceeds 10 hours over wcrs strong divergence convergence occurs on the upwind downwind side curl is strongly negative positive to the right left side facing downwind opposite patterns are generally seen over ccrs divergence curl peaks where winds blow perpendicular parallel to sst fronts sst image analysis indicates enhanced cloudiness occurs with downwind convergence over wcrs wind stress curl due to ring modifications causes dipolar ekman pumping sufficient to influence ring translation and decay processes

investigation of brazil current rings in the confluence region 1 topex poseidon derived along track sha climatological temperature and salinity fields were used within a two layer scheme to estimate the depth of the 8 c isotherm in the southwestern atlantic these fields were used to monitor the formation and characteristics of the brazil current warm core anticyclonic rings shed by the first meander trough after poleward excursions of the brazil current bc results reveal that 40 warm core rings were shed by the bc between january 1993 and october 1998 the observed lifetime ranges between 1 and 4 months with a mean value of approximately 2 months at any given time two to three anticyclonic rings coexisted in the brazil malvinas confluence region most of the rings drifted southward without coalescing with their parent current only four rings were identified as being reabsorbed by the bc front after they were shed no evidence of propagation or absorption of these anticyclones into the eastern limb of the subtropical gyre was observed these rings have a mean horizontal length scale of 55 km mean upper layer thickness of 260 m and mean translation speed of 10 km d 1 volume anomaly and available potential energy computations showed a mean value of 3 6 1012 m3 and 2 5 1015 j respectively the upper layer transport of the bc was also computed and a relationship between variations in the southward transport and ring shedding activity was examined computation of the heat flux anomaly of the bc rings is estimated to be approximately 0 045 pw per annum compilation of these results indicates that warm core rings created by meandering boundary current extensions in different regions are generally similar

historical and recent evidence of scotian shelf water on southern georges bank abstract historical data from 1912 1987 indicate that low salinity less than 32 0 psu near surface water occurs occasionally on southern georges bank during may while none occurs during april composite monthly plots of historical near surface salinity and estimated advection rates show that the southwestern scotian shelf is the immediate upstream source of this low salinity water optimally interpolated satellite derived sst and hydrographic data reveal that very cold less than 2 0 c low salinity less than 32 0 psu scotian shelf water ssw initially located south of the 200 m isobath off southern georges bank in early march 1992 moved north onto southern georges bank during april 1992 ssw was not as extensive during the same period in 1993 as evidence by significantly higher temperatures and salinities these differences show large interannual variability in the transport and or properties of ssw flowing onto georges bank lower higher salinities measured during spring 1992 1993 on southern georges bank are consistent with higher lower st lawrence river discharge noted during spring 1991 1992 and the nine month lag between annual discharge maxima from rivers located upstream and minimum salinity at cape sable in february however comparisons between historical occurrences of low salinity less than 32 0 psu ssw on southern georges bank noted for may 1966 1971 and 1978 and cumulative st lawrence river discharge from the spring prior to each occurrence show no relationship this suggests that the occurrence of low salinity water on southern georges bank is not directly related to variations in upstream river discharge although an idealized model of wind forcing on a bank trapped density front shows that near surface flow is related to superposition of an ekman layer and the along bank gyral circulation evidence from late winter spring 1992 and 1993 on georges bank shows that except for on bank movement of the shelf slope front during late spring 1992 simple ekman theory does not explain on bank movement of the ssw plume during 1992 nor the immobile nature of the shelf slope front during late winter 1992 and late winter spring 1993 surface heat flux and satellite derived sst from georges bank and the scotian shelf together with a slab mixed layer model allows estimation of the advective heat flux and transport of ssw flowing onto georges bank from the scotian shelf during late winter spring 1992 mean advective heat flux onto georges bank during march may 1992 is 14 5 mw cm 2 with an estimated error of 3 5 mw cm 2 demonstrating that advection of cold ssw onto georges bank is required mean velocity and transport of ssw flowing onto georges bank during march may 1992 are 13 4 cm s 1 and 0 21 sv assuming a ssw depth width of 40 m 40 km demonstrating that flow of ssw onto georges bank was robust during the period at this time the dynamics that control the flow of ssw across northeast channel are unknown