analysis of the mesoscale structure in the imecocal region off baja california from hydrographic adcp and altimetry data we present geostrophic velocities obtained using hydrographic altimeter data and direct measurements of currents from 11 cruises offshore of baja california from january 2000 to july 2002 the study area was dominated by meanders and eddies in geostrophic balance two mechanisms of eddy generation were observed the first associated with the geometry of the coastline and the second a product of the cooling of the california current and the california undercurrent from the south there were two persistent eddies observed during the study the first eddy was offshore of bahia vizcaino and had an anticyclonic circulation situated in the southern region the rotation of the second eddy was dependant on which current was first to enter the transition zone along the coast spring was a transition period characterized by the formation of meanders the summer brought a period of eddy generation along the coast autumn and winter were marked by a separation of eddies from the coast and their subsequent drift towards the west the phase velocity of the mesoscale eddies was in accordance with the theory of the linear propagation of a rossby wave

seasonality of the transitional region of the california current system off baja california hydrographic data collected over the period 1997 2013 are analyzed to investigate the seasonality of hydrographic features and associated geostrophic flows off the baja california peninsula the upper ocean in the region was found to be homogeneous in winter and spring but subdivided into two regions in the summer and autumn in the first case the system typically shows relatively low temperature and salinity waters which give it a subarctic character in the second only the region north of punta eugenia 28 n maintains subarctic characteristics while the southern region receives an inflow of tropical and subtropical waters that results from the weakening of northwesterly winds which allows the poleward advection of surface waters also during this period a positive wind stress curl promotes the zonal advection of north pacific s eastern edge waters into the coast and to the north as a surface coastal flow average seasonal patterns of geostrophic flow at 200 dbar revealed that the differentiation into provinces is also evident at that depth with two clearly defined cyclonic structures in summer and autumn both separated at the latitude of punta eugenia the analyses conducted also showed a clear continuity of the california undercurrent along the shelf break with more diffuse currents in the winter poleward flows were observed throughout the water column especially in summer and autumn although the origin of the surface flow does not necessarily involve a surfacing of the california undercurrent

lagrangian exploration of the california undercurrent 1992 95 abstract during the period 1992 95 nineteen isobaric rafos floats placed in the california undercurrent at intermediate depths 150 600 m off monterey and san francisco california reveal a region of varying width of subsurface poleward flow adjacent to the continental margin the float trajectories exhibit three patterns poleward flow in the undercurrent reversing but predominately alongshore flow adjacent to the continental margin and farther offshore anticyclonic motion accompanied by slow westward drift flow continuity of the undercurrent exists between pt reyes and at least cape mendocino with an average speed dependent on the float depth speeds were variable but common features were acceleration occurring to the south of pt arena and deceleration to the north of cape mendocino an important mechanism for floats and water to enter the ocean interior from the undercurrent is through the formation of submesoscale coherent vortices

the importance of small scale faulting in regional extension a recurring observation in many studies of extensional basins has been that the amount of extension visible on normal faults for example on seismic reflection profiles is significantly less than the amount of extension indicated by crustal thickness and thermal subsidence1 5 one mechanism suggested to account for this discrepancy is small scale faulting with offsets too small to be resolved seismically6 7 but earthquake studies8 10 indicate that small faults are responsible for only a small fraction of the total seismic moment in an active area scholz and cowie11 have recently attempted to extend this approach to the total strain at the end of a finite deformation interval by combining scaling laws describing the distributions of fault lengths and displacements here we present fault displacement data that directly conflict with scholz and cowie s conclusions and imply that up to 40 of the extension may be missed by summing fault offsets on basin profiles the fault population at the end of a long deformation interval may differ substantially from that responsible for the earthquake population at any one time

extreme water mass anomaly observed in the hawaii ocean time series extremely anomalous water mass properties with deviations as high as 35 were observed in the thermocline during january 2001 at the hawaii ocean time series site north of oahu the spatial distribution of the anomalous waters is consistent with a submesoscale vortex with radius 15 km possibly a remnant of a mesoscale eddy the most plausible source location of the anomalous waters is offshore of mexico near baja california given the southwestward subtropical gyre circulation it is unlikely that these waters were transported directly westward to hawaii unusual northward transport of equatorial waters along the north american coast during the 1997 98 el nino event and subsequent transport southwestward in the core of a california undercurrent eddy is more plausible el nino modulation of eddy transport and diffusion of water mass properties may substantially impact the mean distribution of properties in the north pacific subtropical gyre

mesozoic seafloor spreading between iberia europe and north america abstract a new earliest cretaceous palaeogeographic reconstruction for the iberian north american and european plates is proposed which attempts to clarify some of the outstanding reconstruction problems in the region from the time of initial opening to the time of magnetic anomaly 34 the instantaneous motion of iberia can be described by a single rotation about a pole off the southwest coast of france in contrast to many previous proposals the new reconstruction places galicia bank east of flemish cap but satisfies all the constraints imposed by palaeomagnetic studies deep sea drilling project results and magnetic anomaly and ocean continent boundary identifications

altimeter derived variability of surface velocities in the california current system 2 seasonal circulation and eddy statistics abstract satellite surface height and temperature fields are used to examine the seasonal surface circulation in the california current system in spring and summer an equatorward jet develops next to the coast with an initial latitudinal structure that responds to the latitudinal distribution of equatorward alongshore winds this jet moves offshore from spring to fall and develops meanders and closed eddies that contribute eddy kinetic energy and water mass properties to the nearby deep ocean higher eke appears first in spring near the coast and moves offshore with the seasonal jet along altimeter tracks parallel to the coastline 200 and 400 km offshore the greatest eke is found in summer and fall respectively with wavelengths of approximately 300 km these are the wavelengths of the largest meanders and the distance between the largest eddies visible in altimeter snapshots of the jet at 600 800 km offshore the wavelengths are generally smaller 100 150 km similar to eddy sizes reported by others for the quiescent northeast pacific some energy with longer wavelengths arrives at the track 600 km offshore in winter and 800 km offshore in spring which we interpret as the most offshore extension of the eke generated by the jet and eddy system closer to the coast in the previous spring and summer a sequence of snapshots from october 1992 to october 1993 shows details of the evolution of the jet and eddy system over one complete annual cycle

the structure of the rockall trough imaged by deep seismic reflection profiling westline is a 450 km long near normal incidence seismic reflection profile crossing the rockall trough from the rockall bank to the irish coast beneath rockall bank and the irish shelf unreflective upper crust overlies reflective lower crust and upper mantle crustal reflectors beneath the irish shelf are interpreted as caledonian the nw slope of the trough is dissected by a series of east dipping faults forming small sediment filled half grabens the steep se slope is formed by the erris ridge the floor of the trough is formed from rotated blocks separated by mainly east dipping faults wedges of sediment fill half grabens formed by this faulting there is no evidence for oceanic crust or a 9reflection moho9 within the trough the floor and slopes of the trough are blanketed by c 4 km of parallel bedded sediments the lower part of the parallel bedded sequence is intruded by sills and dykes that do not extend above a minor unconformity it is suggested that the bulk of the sediment preserved in the rockall trough accumulated during and following a major rifting event in the early or mid cretaceous

mesoscale eddies in the northeastern pacific tropical subtropical transition zone statistical characterization from satellite altimetry 1 mesoscale eddies in the northeastern pacific tropical subtropical transition zone 16 n 30 n 130 w 102 w are analyzed using nearly 18 years of satellite altimetry and an automated eddy identification algorithm eddies that lasted more than 10 weeks are described based on the analysis of 465 anticyclonic and 529 cyclonic eddy trajectories we found three near coastal eddy prolific areas 1 punta eugenia 2 cabo san lucas and 3 cabo corrientes these three areas are located in places where the coastal morphology changes abruptly and strong surface current intensification occurs at some phase of the seasonal cycle although mesoscale eddies in these areas have been previously reported this study provides their first statistically supported characterization punta eugenia showed the highest eddy production with more cyclones generated followed by cabo corrientes also with more cyclones and cabo san lucas with more anticyclones cabo corrientes eddies showed the highest mean values in propagation speed swirling speed and eddy kinetic energy whereas punta eugenia eddies showed the lowest values cyclonic eddies increased their distance traveled and duration from south to north in contrast anticyclonic eddies increased from north to south in average anticyclones tend to travel faster than cyclones in all the subregions these long lived eddies were mainly nonlinear and therefore can redistribute coastal waters relatively far into the open ocean the peaks in the seasonal signal of eddy generation can be associated with the peaks in the strength of the offshore currents and or in the coastal upwelling index no clear relationship could be established between el nino events and eddy generation

new evidence for the origin of the porcupine median volcanic ridge early cretaceous volcanism in the porcupine basin atlantic margin of ireland 1 two dimensional pre stack depth migrated seismic reflection data gravity and velocity models are used to assess the nature and origin of a prominent buried ridge the porcupine median volcanic ridge pmvr within the porcupine basin offshore ireland the debate on the origin of the pmvr during the past 30 years has followed the evolution of the concept of continental margin genesis in this paper the origin of the ridge is evaluated on the basis of the internal geometry and velocity structure revealed by the seismic data implication of the presence of these type of ridges in hyper extensional rifted margins is discussed and compared with other margins the analysis indicates that the ridge is an extrusive volcanic ridge probably tholeiitic in composition constructed by stacked hyaloclastite deltas and topped by carbonate platforms the results invalidate previously proposed models involving highly rotated fault blocks and the serpentinite mud volcanism the extension magnitude analysis suggests a highly stretched setting where limited mantle serpentinization may have occurred but the architecture and velocity of the pmvr demonstrates that it is made of lower velocity materials than serpentinite during the opening of the north atlantic the pmvr represents the northern time equivalent magmatic event expressed along the newfoundland iberia galicia recorded by the j anomaly that originate from cretaceous volcanic deposits

lithospheric extension and magmatism in the porcupine basin west of ireland the porcupine seabight basin is a north south trending extensional sedimentary basin situated on the continental shelf west of ireland it is filled with sedimentary rocks which range in age from devonian to present day a large amount of geological and geophysical data is now available for this basin mainly as a result of oil industry exploration in this paper information from 23 well logs and from regional seismic reflection surveys is used to determine the lithospheric stretching history of the basin subsidence analyses indicate that there was one main phase of stretching which began in late liassic times 180 ma ending in earliest cretaceous 145 ma stretching factors at the northern end of the basin are relatively small 1 1 1 7 but increase rapidly southwards along the axis of the main porcupine basin in the southern part of the region the seabight basin is greater than 6 the simplest way to accommodate this rapid variation in stretching is by clockwise rotation of the porcupine ridge through approximately 20 away from the irish shelf subsidence derived stretching values are in reasonable agreement with those determined previously from crustal thicknesses based on gravity models and deep seismic data normal incidence and wide angle the existence location and inferred age of the porcupine median volcanic ridge are also consistent with the subsidence derived stretching factors after intermittent paleocene igneous activity an anomalous increase in the rate of subsidence occurred in the eocene between 55 and 42 ma there is little evidence that this rapid increase is caused by lithospheric stretching and we conclude that it must be associated in some unknown way with melt generated by development of the iceland hotspot

multiple generations of hibonite in spinel hibonite inclusions from murchison through freeze thaw disaggregation of the murchison meteorite we have recovered in addition to many spinel hibonite spherules several hibonite rich inclusion fragments in which the hibonite has wider ranges in tio2 contents e g 0 07 8 6 wt in one inclusion and 2 10 wt in another than previously observed within single inclusions in these inclusions there are sharp contacts between texturally early ti poor hibonite and relatively late ti rich hibonite and the two types occur in complex intergrowth textures that are not consistent with crystallization from a melt in a single stage cooling event one inclusion has in addition to relatively tio2 rich hibonite some that is virtually tio2 free but contains 1 wt mgo and 1 5 wt sio2 instead of the common substitution of mg ti for 2al mg coupled with si in this case probably reflecting crystallization from an unusual ti free silicate liquid ion microprobe analyses of ti rich and ti poor hibonite from this inclusion yield quite similar trace element patterns and mg isotopic compositions the results are most consistent with formation of ti rich hibonite from ti poor hibonite by addition of mg and ti to the latter by exchange with a hot ti rich liquid that this occurred without a resolvable change in the mg isotopic composition requires that the ti rich second generation of hibonite formed 2 5 times 105 yr later than the ti poor hibonite observations of spinel hibonite spherules and spherule fragments in our sample suite provide additional evidence that despite the claims by greenwood et al 1994 spinel hibonite spherules crystallized from individual molten droplets as earlier suggested by macdougall 1981 and macpherson et al 1983

equatorial pacific 13 c water eddies in the eastern subtropical south pacific ocean abstract argo float profile data are used to analyze warm salty weakly stratified subthermocline eddies of tropical origin in the eastern subtropical south pacific ocean these eddies contain anomalous signatures of the equatorial pacific 13 c water that is carried poleward within the peru chile undercurrent pcu as it flows along the west coast of south america from their source along the chilean coast between 29 and 39 s the eddies spread westward and slightly northward likely at least partly advected by the subtropical gyre the eddy water properties contrast strongly with the colder fresher more strongly stratified waters of subantarctic origin being carried northward then westward by the gyre near the eddy source about 6 of argo profiles sample eddies that are above selected thresholds for both salinity and potential vorticity anomalies relative to maps of the mean distributions of these properties on and around the core isopycnal for the eddies the proportion of such profiles dimini

subthermocline eddies observed by rapid sampling argo floats in the subtropical northwestern pacific ocean in spring 2014 in spring 2014 two subthermocline eddies stes were observed by rapid sampling argo floats in the subtropical northwestern pacific stnwp the first one is a warm salty and oxygen poor lens with its temperature salinity dissolved oxygen t s do anomalies reaching 1 16 c 0 21 practical salinity unit psu 29 9 mol kg respectively near the 26 62 0 surface the other is a cold fresh and oxygen rich lens with its t s do anomalies reaching 1 95 c 0 34 psu 88 0 mol kg respectively near the 26 54 0 surface the vertical extent of the water mass anomalies in the warm cold ste is about 190 m 150 m and its horizontal length scale is 22 7 km 18 10 km according to their water mass properties we speculate that the warm and cold stes are generated in the north pacific subtropical and subarctic front region respectively the observed stes may play an important role in modifying the intermediate layer water properties in the stnwp and this needs to be confirmed by more focused observations in the future

semiannual variability of the california undercurrent along the southern california current system a tropical generated phenomenon we used a high resolution numerical model implementation to analyze the california undercurrent cu dynamics along the southern california current system in agreement with reported observations the modeled cu was stronger during june july and december january when it flowed continuously along baja california and southern california reaching long term averages up to 6 cm s 1 previous research has associated the biannual cu intensification to the local dynamics off southern california our results evidenced however that the passage of remote semiannual coastal trapped waves sctw primarily explained the semiannual cu variability the cu was stronger 2 3 months after the passage of the upwelling sctw phase when the offshore propagation of rossby waves brought about by the sctw transit induced an energetic cross shore pressure gradient that strengthened the subsurface poleward circulation along the continental slope the sctw were independent of the local wind they corresponded to the northward extension of semiannual equatorial kelvin waves that have been observed along the northeastern tropical pacific

tectonic controls on upper jurassic to lower cretaceous reservoir architecture in the jeanne d arc basin with some comparisons from the porcupine and moray firth basins

subsidence of the voring basin and the influence of the atlantic continental margin the post cretaceous subsidence history of the voring basin part of the atlantic passive margin offshore mid norway has been investigated extension and factors related to rifting and continental break up during the palaeocene have been quantified using both forward and reverse basin modelling techniques in the preferred geological model it is assumed that rifting occurred in the voring basin during the palaeocene prior to break up following an earlier rift event during the late jurassic during palaeocene rifting the basin may have been dynamically uplifted by the iceland mantle plume in the east of the basin there was no palaeocene extension subsidence analysis shows that in the centre of the basin forward and reverse models converge to predict a modest palaeocene stretching factor of c 1 15 in the west of the basin closest to the atlantic margin forward models of upper crustal faulting also predict a of c 1 15 but reverse backstripped models of subsidence predict a of up to 1 75 we suggest that lower crustal and mantle lithosphere thinning close to the margin were greater than the extension accommodated by upper crustal faulting and that some lower crustal mantle lithosphere stretching associated with continental separation was partitioned below the voring basin up to 150 km landwards of the margin

a mesoscale eddy dipole in the offshore california current there is a transition zone in the california current system between inshore coastal and offshore oceanic flow this transition zone is associated with the main core of the california current and is populated with offshore mesoscale eddies the structure of isolated eddies and dipole eddy pairs found within the transition zone is examined using water mass analysis spiciness and dissolved oxygen the analyses show that these offshore mesoscale eddies have cores which contain california undercurrent water these observations and independent observations of the sitka eddy near sitka alaska support the conclusion that a bathymetrically induced instability of the california undercurrent is a likely generation mechanism for the offshore eddies this conclusion also is consistent with mathematical models of eddy generation in a subsurface poleward baroclinic current the similarity between long term mean conditions caicofi conditions observed during january 1981 and july 1985 and those of the sitka eddy coupled with the bathymetric effects provides a plausible explanation for the recurrence of offshore mesoscale eddies at preferred locations within the transition zone

correlated morphological chemical and isotopic characteristics of hibonites from the murchison carbonaceous chondrite twenty four hibonite dominated refractory grains from the murchison carbonaceous chondrite have been identified from polished grain mounts of density separates and have been morphologically and chemically divided into three groups 1 14 colourless platy crystal fragments placs with less than 2 7 tio2 2 3 pleochroic blue aggregates bags which are composed of crystal plates and fragments and have tio2 concentrations between 5 1 and 6 5 3 six spinel hibonite spherules and crystal aggregates shibs often with spinel fe silicate and clinopyroxene rims the maximum tio2 concentrations of hibonite in the shibs ranges from 3 5 to 7 6 but the tio2 concentration in one grain was heterogeneous and ranged from 0 5 to 5 0 hibonite in all types is stoichiometric with ti and mg predominantly in a coupled substitution of mg2 and ti4 for 2al3 one grain with a rounded hibonite core does not clearly fit into the three designated groups the hibonites have been analysed by ion microprobe mass spectrometry for their mg and ti isotopic compositions twelve of the placs have 26al27al 0 ratios less than 1 10 5 but the other two placs have 26al27al 0 of 5 5 10 5 and 7 7 10 5 the excess 26mg may reflect initial mg isotopic heterogeneities in the source region of the placs or be the result of in situ26al decay in which case the distribution of 26al was heterogeneous three bags show substantial positive mass fractionation of mg one grain has excess 26mg while the other two have 26mg depletions the 26mg depletions indicate the preservation of mg isotopic anomalies in the bags but the excess 26mg in one grain could be due to in situ26al decay the six shibs have excess 26mg that is correlated with 27al24mg the mg isotopic systematics of the shibs are consistent with the in situ decay of 26al with 26al27al 0 of ca 5 10 5 the unclassified hibonite has a clearly resolved deficit in 26mg titanium isotopic anomalies are common in the hibonites measured here the largest anomalies are in 50ti with variations in 50ti48ti ranging from 50 to 16 relative to terrestrial smaller anomalies are present in 49ti and 47ti the ti isotopic compositions are not directly correlated with morphological type but the placs show the largest variations in isotopic composition whereas the shibs are generally close to terrestrial the presence of hibonite populations with distinct morphological chemical and mg isotopic systematics suggests that there were several hibonite formation episodes within the early solar system the hibonites probably formed by the melting of refractory dust aggregates during local transient thermal events

evolution of oceanographic conditions off baja california 1997 1999 abstract this paper examines the oceanic response off baja california mexico to the 1997 1998 el nino and the transition to la nina conditions the data presented were gathered during seven cruises over a grid based on the calcofi station plan from lines 100 130 out to station 80 t s diagrams with data obtained during the peak phase of el nino demonstrate that warmer and saltier spicier than normal conditions prevailed in the upper 600 m over this region temperature and salinity anomalies calculated for calcofi line 120 revealed waters near the coast at 50 m depth to be up to 8 7 c warmer and s 0 8 saltier than the climatology during october 1997 these large anomalies persisted through january 1998 with some slight diminution in the magnitudes near the surface this study suggests that anomalously warm and salty waters were fed from a source of spicy water to the southwest identified as subtropical surface water stsw and that low salinity tropical surface waters tsw were blocked to the southeast in the vicinity of the tip of the peninsula subsurface waters associated with the california undercurrent cu fed from the eastern tropical pacific etp were also warmer and saltier than normal and indicate a significant expansion in volume of the cu presumably a result of intensification of poleward flow at depth we postulate that the well defined near surface and deep poleward flows in the study area reflect anomalous large scale cyclonic circulation affecting the flow in the southeastern region of the north pacific subtropical gyre east of 125 w following the el nino event warm and salty upper waters retreated to latitudes south of punta eugenia with the return to normal and cooler conditions equatorward flow over the sampling grid predominated with an increased meandering and mesoscale activity transition to la nina conditions would have been associated with re establishment of normal anticyclonic flow in the southeastern quadrant of the pacific subtropical gyre

eddy properties in the california current system 1 eddy detection and tracking algorithms are applied to both satellite altimetry and a high resolution dx 5 km climatological model solution of the u s west coast to study the properties of surface and undercurrent eddies in the california current system eddy properties show remarkable similarity in space and time and even somewhat in polarity summer and fall are the most active seasons for undercurrent eddy generation while there is less seasonal variation at surface most of the eddies have radii in the range of 25 100 km sea level anomaly amplitudes of 1 4 cm and vorticity normalized by f amplitudes of 0 025 0 2 many of the eddies formed near the coast travel considerable distance westward with speeds about 2 km day consistent with the effect anticyclones and cyclones show equatorward and poleward displacements respectively long lived surface eddies show a cyclonic dominance the subsurface california undercurrent generates more long lived anticyclones than cyclones through instabilities and topographic coastline effects in contrast surface eddies and subsurface cyclones have much more widely distributed birth sites the majority of the identified eddies have lifetimes less than a season eddies extend to 800 1500 m depth and have distinctive vertical structures for cyclones and anticyclones eddies show high nonlinearity rotation speed higher than propagation speed and hence can be efficient in transporting materials offshore

the development of irish offshore sedimentary basins a variety of ensialic mesozoic and cenozoic sedimentary basins surround ireland three main periods of basin development occurred the first in the permo triassic produced a series of small rift basins which nucleated along reactivated generally caledonian structures the second in the mid and late jurassic represents a period of crustal extension and rifting the third phase reflects thermal subsidence of cretaceous and tertiary age and coincides with seafloor spreading in the north atlantic the basins developed in response to general east west extension simple extensional structures accompanied by crustal thinning dominated in the north south trending porcupine basin the ne sw oriented basins in the celtic sea slyne erris donegal and rockall areas developed in a transtensional setting until early cretaceous times the goban spur basins at the confluence of regional structural trends and adjacent to the continent ocean boundary are dominated by transtensional structures the effects of early tertiary alpine compression are seen especially in the celtic sea basins the basins whilst having some broad geological similarities which reflect eustatic sea level variations differ in their detailed evolution each basin experienced unique facets of local structural control tectonic history and facies distribution

upper ocean water mass characteristics of the california current summer 1993 abstract two large high resolution upper ocean surveys of the california current region were conducted in the summer of 1993 temperature and salinity were measured from a seasoar vehicle and velocity was measured by a ship borne acoustic doppler current profiler both surveys extended from the continental margin to 128 w and consisted of zonal sections 28 km apart the first survey 7 28 june extended from 39 5 n to 36 25 n and the second 16 august to 1 september extended from 39 0 n to 37 0 n the current field was fairly simple in june showing an equatorward surface jet with only one gentle meander a nearly continuous poleward california undercurrent near the continental margin and two anticyclonic subsurface eddies offshore of the jet by august meanders in the surface jet had strengthened and eddies dominated the flow field large scale trends in the water mass characteristics spiciness along three isopycnal surfaces 26 4 26 0 and 25 6 kg m 3 show that temperature and salinity tend to increase towards the equator and towards shore consistent with poleward advection along the continental margin local minima in spiciness tend to coincide with the equatorward surface jet local maxima in spiciness are associated with subsurface anticyclonic eddies which have a core depth of about 150 m and seem to originate in the california undercurrent over the continental slope at local latitudes we identified several different anticyclonic eddies each with different water mass characteristics all of the eddies we observed had diameters larger than the baroclinic radius of deformation water mass characteristics and migration rates are consistent with formation over the continental margin within the preceding 6 8 months

generation of subsurface cyclonic eddies in the southeast baltic sea observations and numerical experiments 1 closely spaced ctd transects performed in the summertime reveal simultaneous downward upward bendings of temperature salinity contours in the seasonal thermocline permanent halocline of the stolpe channel and the gulf of gdansk which may be interpreted as geostrophically balanced cyclonic eddies in the intermediate layer to examine processes capable of forming the observed cyclonic eddies a numerical simulation based on the princeton ocean model pom has been initiated the subsurface cyclones in the stolpe channel were satisfactory simulated in model runs under easterly northerly wind conditions their formation was shown to result from the adjustment of the high potential vorticity pv outflow from the bornholm basin via the stolpe sill to low potential vorticity environment by vortex stretching so called the pv outflow hypothesis by spall and price 1998 in accordance with the real wind conditions a cyclonic eddy observed in the intermediate layer of the gulf of gdansk was satisfactorily reproduced in a model run with the westerly wind shutdown which implies westward transport throughout the stolpe channel and thereby excludes the pv outflow hypothesis the subsurface cyclone simulated in the gulf of gdansk was traced to form in the course of relaxation of the coastal downwelling baroclinic jet

effects of mesoscale processes on phytoplankton chlorophyll off baja california 1 using satellite sea surface height ssh and chlorophyll chl the year 2000 is analyzed to characterize the effects of mesoscale circulation patterns on phytoplankton spatial variability in the california current cc off baja california satellite data are combined with and compared to in situ field measurements chlorophyll a and hydrographic variables along vertical alongshore sections located 130 km offshore between 24 5 33 n monthly average maps of ssh and surface geostrophic velocities depict the characteristics of mesoscale meanders and eddies which correspond well with the subsurface hydrographic and velocity fields satellite derived pigment chl represent in situ fields in the upper 0 20 m overall r 0 53 p 0 05 but their representation of peak values in deep chlorophyll maxima dcm at 50 m depth are inaccurate dcm are traced in all three seasons january july descending from near the surface north of 31 n to 50 m over a large extent of the transect to the south approximately following the 24 7 25 1 isopycnals as they and the isotherms deepen to the south in january phytoplankton chlorophyll concentrations in the dcm are relatively uniform originating during upwelling events that occur farther north then following the equatorward flow of the cc during april and july the discrete maxima in the dcm occur at the centers of cyclonic meanders and the chlorophyll concentrations inside these maxima are enhanced as a result of local coastal upwelling off baja california phytoplankton blooms created by coastal upwelling spread offshore and subduct along the 24 7 25 1 isopycnals creating the dcm along the inner part of the meandering jet

main eddy vertical structures observed in the four major eastern boundary upwelling systems in the four major eastern boundary upwelling systems ebus mesoscale eddies are known to modulate the biological productivity and transport near coastal seawater properties toward the offshore ocean however little is known about their main characteristics and vertical structure this study combines 10 years of satellite altimetry data and argo float profiles of temperature and salinity and our main goals are i to describe the main surface characteristics of long lived eddies formed in each ebus and their evolution and ii to depict the main vertical structure of the eddy types that coexist in these regions a clustering analysis of the argo profiles surfacing within the long lived eddies of each ebus allows us to determine the proportion of surface and subsurface intensified eddies in each region and to describe their vertical structure in terms of temperature salinity and dynamic height anomalies in the peru chile upwelling system 55 of the sampled anticyclonic eddies aes have subsurface intensified maximum temperature and salinity anomalies below the seasonal pycnocline whereas 88 of the cyclonic eddies ces are surface intensified in the california upwelling system only 30 of the aes are subsurface intensified and all of the ces show maximum anomalies above the pycnocline in the canary upwelling system 40 of the aes and 60 of the ces are subsurface intensified with maximum anomalies extending down to 800 m depth finally the benguela upwelling system tends to generate 40 50 of weak surface intensified eddies and 50 60 of much stronger subsurface intensified eddies with a clear geographical distribution the mechanisms involved in the observed eddy vertical shapes are discussed

a calcium aluminum rich inclusion from the essebi cm2 chondrite evidence for captured spinel hibonite spherules and for an ultra refractory rimming sequence abstract an unusual refractory inclusion was discovered in the essebi cm2 chondrite the inclusion has high concentrations of refractory lithophile and siderophile elements with strong enrichments of the most refractory elements lu sc hf in one part of the inclusion the inclusion consists of a melilite rich core partially surrounded by a very refractory rim which in turn is covered by a mantle enriched in si al fe mn cl and s melilite compositions vary from ak 10 26 in the core to ak 0 12 in the rim the core contains several complex framboids consisting of spinel fassaite or spinel hibonite these framboids are probably spherules of the types reported from murchison and were possibly captured by the molten inclusion before it solidified these findings may indicate a genetic link between framboids in cai s and the spinel rich spherules in murchison the rim sequence consists of the following five layers from inside to outside 1 1 hibonite spinel melilite 2 2 hibonite perovskite spinel melilite melilite in this layer is altered to sodalite nepheline calcite 3 3 a hibonite corundum solid solution 4 4 a spinel corundum solid solution as much as 0 1 mole fraction al 2 67 o 4 5 5 sc rich fassaite as much as 6 2 wt sc 2 o 3 spinel al 2 o 3 solid solution al rich diopside pt rich metal crystals occur only in the rim some of these metal crystals contain minor amounts of zr and hf indicating that they formed under reducing conditions the bulk mineral chemistry and texture of the essebi inclusion indicates a complex history involving capture of solid spinel and spinel hibonite spherules similar to the murchison type by a refractory melt droplet solidification of the droplet without obliteration of the spherule textures transportation of the composite object to hotter regions of the solar nebula where the very refractory rim condensed alteration of melilite to sodalite nepheline minor calcite and finally burial in the essebi parent body the cl s bearing mantle probably formed by reactions between the inclusion and liquid and gaseous phases in the parent body

pre mesozoic geology of the western and north western irish continental shelf exploration wells drilled offshore west and north west of ireland penetrated a c 3 7 m cumulative thickness of permo carboniferous sediments overlying dalradian metasediments intruded by caledonian granitic plutons in the north late tournaisian to early visean clastics were deposited coeval with the rheic transgression upon an emergent craton in a continental to marginal marine environment they record an increasing marine influence upwards with the establishment of a carbonate shelf in the asbian clastic carbonate sedimentation which became cyclical in late visean to early namurian temporally correlates with the yoredale cyclothems younger namurian sediments are not preserved sedimentation in early westphalian progressed from prodelta to coal enriched delta top and abandonment facies and is conformably succeeded by brackish to freshwater sediments that contain evidence for local marine incursions of stephanian age an autuno silesian section that is preserved offshore may also have been deposited onshore prior to erosion seismic data enable partial delineation of n s and ne sw early sub basins marginal to the main porcupine basin these sub basins which contain silesian sediments may have styled successive extensional episodes in the basin and augment support for rift models of carboniferous basin development in the north atlantic nw european domain birps data provide supporting evidence for the offshore prolonga tion of pre mesozoic basement fault zones

subthermocline eddies over the washington continental slope as observed by seagliders 2003 09 abstractin the california current system subthermocline lenslike anticyclonic eddies generated within the california undercurrent cu are one mechanism for lateral transport of the warm saline waters of the cu garfield et al established the name cuddies for eddies of this type and hypothesized that they account for a significant fraction of the offshore transport of cu water this study presents observations of subthermocline eddies collected from a time series of seaglider surveys in the northern california current system gliders made 46 crossings of subthermocline anticyclones and 17 crossings of subthermocline cyclones over 5 5 yr close inspection grouped these into 20 distinct anticyclones and 10 distinct cyclones water properties at the core of anticyclonic eddies were similar to those in the core of the cu over the continental slope these anticyclones are examples of cuddies anticyclonic cyclonic eddies had average radii of 20 4 20 6 km peak azimuthal current speeds of 0 25 0 23

mesoscale variability and nutrient phytoplankton distributions off central southern chile during the upwelling season the influence of mesoscale eddies abstract mesoscale features are recurrently found in the coastal transition zone ctz off central southern chile 35 40 s a region characterized by seasonal wind driven coastal upwelling in this study oceanographic data from two consecutive cruises carried out during the upwelling season january 2009 were combined with satellite time series data in order to characterize the structure and evolution of mesoscale eddies and to explore their influence on phytoplankton structure and nutrient distribution in the context of organic carbon exchanges between the coastal upwelling zone and the ctz two coastally generated contiguous mesoscale eddies 2 months old were characterized a surface cyclonic eddy cc1 and a subsurface anticyclonic eddy aa1 the distributions of salinity and dissolved oxygen together with nutrients suggested that both eddies were sites of vertical injection of high nutrient concentrations from the equatorial subsurface water mass essw into the upper layer in the ctz in addition eddy aa1 in combination with an upwelling plume was involved in the offshore advection of nutrients from the core of the essw located in the coastal zone at shallow depths

intrathermocline eddies in the coastal transition zone off central chile 31 41 s 1 the three dimensional structure and the origin of mesoscale anticyclonic intrathermocline eddies ites in the coastal transition zone ctz off central chile 31 41 s were analyzed through the combination of data from oceanographic cruises and satellite altimetry and the application of an eddy resolving primitive equation ocean model coupled with a numerical experiment using a passive tracer in this region ites are represented by subsurface lenses 100 km diameter 500 m thickness or vertical extension of nearly homogeneous salinity 34 5 and oxygen deficient 1 0 ml l 1 waters properties which are linked to the equatorial subsurface water mass essw transported poleward by the peru chile undercurrent pcuc in the coastal band at least five to seven ites were observed simultaneously in the area between 31 and 38 s during winter cruises in 1997 and 2009 satellite data indicated that the ites identified from in situ data moved westward each at a mean speed of 2 km d 1 and transported a total volume of 1 106 m3 s 1 1 sv the lifespan of each ite ranged from a few months to 1 year model results indicate that ites become detached from the pcuc under summer upwelling conditions in the coastal zone

gravity and magnetic studies of crustal structure across the porcupine basin west of ireland abstract gravity magnetic and seismic data from a profile across the porcupine basin are used to suggest a model for the crustal structure in the region the 280 km long profile bears wsw off the southwest coast of ireland and overlaps partially with the coole 3a and 3b lines of makris et al 13 the gravity data are processed to produce an isostatic residual anomaly which is then modelled by two and a half dimensional methods using the seismic data to provide geometrical constraints similar modelling techniques are used for the magnetic data the final model shows crystalline crust which thins from 28 km at the eastern end of the profile to less than 8 km beneath the central part of the basin the thinned crust is intruded by dense magnetic bodies whilst the eastern margin is underlain by a large low density body which is assumed to be a granite these new findings have parallels in other basins on thinned and rifted crust

saline intrusions in the intermediate waters north of oahu hawaii abstract the hawaii ocean time series hot hydrographic observations at station aloha 22 45 n 158 w reveal that the region is sometimes the site of intrusive interleaving of different water types near the salinity minimum of the north pacific intermediate waters this interleaving is associated with saline laminae or lenses 5 30 km long submesoscale and 5 100 m thick finestructure the temporal variability of these intermediate waters is investigated statistically and a background water type is defined against which to measure the strength of intrusions the salinity minimum shows a relative maximum in variability caused mainly by the episodic appearance of the saline finestructure intrusions which are correlated with low oxygen and silicate concentrations the intermediate salinity minimum has its southern boundary near the latitude of the hawaiian islands where salinity increases towards the south and oxygen gradually decreases thus stirring processes local to the hawaiian ridge may explain the observations possible mechanisms are suggested including fluctuations of the subtropical gyre southern boundary and a hydrodynamically unstable flow at intermediate depths along the ridge either process could transport relatively saline water into the aloha region and would lead to interleaving driven by double diffusion on scales of the order of 10 m in the vertical

from continental hyperextension to seafloor spreading new insights on the porcupine basin from wide angle seismic data key points new analysis of wide angle seismic data from the southern porcupine basin evidence for presence of oceanic crust in the southern porcupine basin jurassic rifting propagated from south to north resulting in non uniform strain when rifting stopped the deep structure and sedimentary record of rift basins provide an important insight into understanding the geological processes involved in lithospheric extension we investigate the crustal structure and large scale sedimentary architecture of the southern porcupine basin offshore ireland along three wide angle seismic profiles supplemented by thirteen selected seismic reflection profiles the seismic velocity and crustal geometry models obtained by joint refraction and reflection travel time inversion clearly image the deep structure of the basin our results suggest the presence of three distinct crustal domains along the rifting axis a continental crust becoming progressively hyperextended from north to south through the basin b a transitional zone of uncertain nature and c a 7 8 km thick zone of oceanic crust the latter is overlain by a 8 km compacted upper paleozoic mesozoic succession and 2 km of cenozoic strata due to the lack of clear magnetic anomalies and in the absence of well control the precise age of interpreted oceanic crust is unknown however we can determine an age range of late jurassic to late cretaceous from the regional context we propose a northward propagating rifting process in the porcupine basin resulting in variations in strain along the rift axis

three compartment structure of subsurface intensified mesoscale eddies in the ocean mesoscale eddies are energetically dominant and pervasive over most of the world s oceans among them many are subsurface intensified with strongest signals in the ocean interior such as mode water eddies which trap water masses with distinctive properties and carry them over long distances with both argo profiling floats and atmospheric reanalysis data we showed that the structure of these eddies obeys a universal rule hence their three dimensional hydrographic fields can be readily reconstructed from very limited information more interestingly the volume of water trapped and moved by a mode water eddy is much greater than previously thought it has a three compartment structure in the vertical with the mode water being sandwiched between two layers of notably different properties and accounting for only a portion of the total trapped volume this article is protected by copyright all rights reserved

a subsurface warm eddy off northern baja california in july 2004 1 upper ocean eddies are commonly observed from remote sensing but submerged eddies are more difficult to detect during july 2004 a 21 day hydrographic survey in the southern region of the california current was carried out to investigate the mesoscale variability we observed for the first time a subsurface anticyclonic eddy off northern baja california with the same water mass characteristics as the california undercurrent the core of the eddy was quasi circular with radii of 35 km and thickness of 250 m the maximum swirl velocity was 3 cms 1 the water mass of the core of the eddy was characterized by potential temperature of 11 c salinity of 34 5 and dissolved oxygen of 1 4 mll 1 the eddy propagated westward the subsurface warm eddy could transport relatively saline water into the north pacific subtropical gyre

interannual variability of tehuantepec eddies 1 topex poseidon satellite altimeter observations and the naval research laboratory layered ocean model simulations show interannual variability in the number and intensity of tehuantepec eddies off the mexican southwest coast analysis of the results illustrates that downwelling coastally trapped waves which are generated in the equatorial pacific play a crucial role in the modulation and generation of tehuantepec eddies and a dominant role in tehuantepec eddy interannual variability this introduces a new paradigm in which the generation and modulation of tehuantepec eddies is not exclusively explained in terms of the strong and intermittent tehuantepec wind events in fact the results show anticyclonic eddy formation during periods of calm tehuantepec winds that is specifically exemplified by the formation of two anticyclonic tehuantepec eddies during a 5 month period of weak gulf of tehuantepec winds during summer of 1997 furthermore the satellite observed and nlom simulated proliferation of tehuantepec eddies during el nino years is explained by the corresponding increase in downwelling coastally trapped waves and a lack of increase in the number and strength of tehuantepec wind events during el nino years

refractory inclusions in the prototypical cm chondrite mighei abstract refractory inclusions in the mighei cm2 meteorite are very abundant 35 being found in three thin sections of the meteorite the most common are pyroxene rimmed spinel rich inclusions that occur in a range of structural and textural types some inclusions are simple aggregates of crystals or rimmed crystals ranging from loose clusters of spinel grains to distended chains of pyroxene rimmed spinel knots others are more compact and may have experienced recrystallization or melting these include nodular spinel inclusions with polygonal granular textured spinel interiors and pyroxene rims ribbons of spinel in some cases with hibonite and or perovskite that are again rimmed by pyroxene and refractory spherules four inclusions are complex aggregates of several texturally distinct objects each collectively mighei inclusions are similar to those in murchison but appear to be somewhat more altered volatility fractionated and unfractionated trace element patterns similar to those found in refractory inclusions in other carbonaceous chondrites are represented in mighei inclusions and in addition some mighei inclusions have volatility fractionated pattern types not previously found in refractory inclusions in three of the complex aggregates fundamentally different trace element patterns are present within different portions of each inclusion meaning that these objects accreted from genetically different components that never equilibrated with one another subsequent to accretion bulk inclusion magnesium isotopic compositions show minor mass fractionation effects fmg values range from 2 3 to 7 5 but the average fmg value is indistinguishable from normal 1 8 1 2 there are no correlations between magnesium isotopic composition and textural type or trace element pattern type the diverse inclusion types in mighei represent a variety of origins and histories textures suggest that the nodular and banded inclusions may have experienced solid state recrystallization whereas the porous and chain like varieties and complex aggregates have not magnesium isotopic compositions and trace element abundances suggest that the mighei inclusions are unlikely to be evaporation residues and are more likely to be the products of condensation or recondensation processes

lagrangian observations of meddy formation during a mediterranean undercurrent seeding experiment mediterranean eddies meddies play an important role in maintaining the temperature and salinity distributions in the north atlantic but relatively little is known about their early life histories including where how often and by what mechanism they form a major field program called a mediterranean undercurrent seeding experiment has been carried out to directly observe meddy formation and the spreading pathways of mediterranean water into the north atlantic between may 1993 and march 1994 49 rafos floats were deployed sequentially in the mediterranean undercurrent south of portugal and tracked acoustically for up to 11 months the float deployments were accompanied by high resolution xbt sections across the undercurrent nine meddy formation events were observed in the float trajectories six near cape st vincent at the southwestern corner of the iberian peninsula and three near the estremadura promontory along the western portuguese continental slope meddy formation thus occurs where the continental slope turns sharply to the right when facing in the downstream direction of the undercurrent after conditionally sampling the float dataset to identify floats that were well seeded in the undercurrent the authors have estimated a meddy formation rate of 15 20 meddies per year the timescale for meddy formation at cape st vincent was found to be 3 7 days shorter than previous estimates based on the volume of larger meddies meddies were observed to form most frequently when the speed of the mediterranean undercurrent was relatively fast the meddy formation process at cape st vincent resembles the conceptual model of e a d asaro whereby anticyclonically rotating eddies are formed by separation of a frictional boundary layer with negative relative vorticity at a sharp corner comparison of the relative vorticity in the anticyclonic shear zone of the undercurrent and that of the newly formed meddies shows that much of the anticyclonic relative vorticity in meddies can be accounted for by the horizontal shear in the undercurrent this confirms earlier work suggesting that the classical mechanism for the generation of submesoscale coherent vortices by collapse and geostrophic adjustment of a weakly stratified fluid injected into a stratified ocean may not be the principle mechanism at work in the formation of meddies at cape st vincent