early diagenetic silica deposition in algal cysts and spores a source of sand in black shales abstract devonian black shales deposited on the north american craton contain abundant tasmanites cysts although these are typically flattened because of compaction a small proportion are filled with diagenetic silica the latter are spherical to ellipsoidal 0 1 0 5 mm and filled with chalcedony microquartz and megaquartz and single quartz crystals chalcedonic cyst fillings are preserved best in cheat and phosphate nodules whereas megaquartz and single quartz crystals are most common in shale matrix together with colloform textures this suggests that the various silica types originated from recrystallization of early diagenetic silica deposits thin sandstone beds in the chattanooga shale e g bransford sandstone contain abundant quartz sand that is much coarser than the detrital quartz component of the underlying black shales because of this their quartz component is thought to have been transported over considerable distances from the basin margin however because certain shale horizons contain as much as 10 silicified cysts that upon reworking could have yielded quartz grains of fine to coarse sand size the quartz component of these sandstone beds may actually have formed in situ indeed petrographic examination of the sandstone beds shows them to contain quartz grains with morphological and textural features of cyst quartz e g rounding sphericity chalcedony pyrite inclusions lobate grain margins thus silica deposition in algal cysts may provide a significant component of intrabasinal quartz sand in shale sequences distinction of this type of quartz from extrabasinal detrital quartz is important to the reconstruction of the depositional history of shale sequences

diagenesis of the lower eocene thebes formation gebel rewagen area eastern desert egypt abstract the diagenesis of lower eocene shallow water carbonates with flint was studied in the gebel rewagen area eastern desert egypt the carbonates are mainly wackestones to packstones with benthic bioclasts embedded in a dark red luminescent micrite matrix the studied succession displays a complex diagenetic history that involves syngenetic and late diagenetic processes silica which exists either as persistent bands nodules and or silicified benthic bioclasts shows a distinctive pattern regarding its distribution source depositional environments and timing three lines of evidence support a syngenetic origin of the chert bands 1 they alternate in a cyclic manner within the host carbonates and 2 they exhibit noticeable lateral persistence throughout the investigated area following the strata boundaries and 3 there is a lack of any carbonate dissolution in limestone adjacent to chert bands the deposition of silica bands in association with shallow water carbonates is possibly related to eustatic sea level changes which were accompanied by episodic variations in silica and carbonate productivities with a relative sea level fall and the establishment of a lowstand period at the end of the early eocene a basinward shift of the groundwater zones is expected within the carbonate platform during this period some late diagenetic processes took place which involve 1 the formation of siliceous and carbonate concretionary growths 2 partial silicification of bioclasts 3 neomorphic stabilization of the caco3 bioclasts and 4 the formation of equant calcite cement siliceous and carbonate concretions are believed to have taken place within microenvironments created and controlled by sulphate reducing bacteria and physico chemical and kinetic factors near a marine meteoric water mixing zone this is inferred from the distribution of iron sulphides the non ferroan nature of all concretions and the depleted 13c 5 4 to 6 0 pdb and 18o 5 8 to 6 8 pdb values of the carbonate concretions the silica fabrics of all the partly silicified benthic bioclasts with abundant pyrite cubes argue for a delayed silicification process within the sulphate reduction zone the close and relatively depleted 18o values of the low mg calcite micrite matrix 3 0 to 4 4 pdb and benthic bioclasts 3 4 to 4 8 pdb indicate that both matrix and bioclasts have probably suffered neomorphic stabilization from freshwater dominated solutions the initial marine 13c values of both low mg calcite matrix 0 2 to 2 2 pdb and altered benthic bioclasts 0 2 to 0 9 pdb are retained and not affected by diagenesis the luminescence character and the extremely depleted oxygen values 8 3 to 10 1 pdb of the equant void filling calcite mosaics are consistent with their formation within a meteoric phreatic realm

distribution of pleuroncodes monodon larvae over the continental shelf of south central chile field and modeling evidence for partial local retention and transport abstract in situ and modeled spatial distribution of squat lobster pleuroncodes monodon larvae over the continental shelf off south central chile 35 37 s was analyzed along with currents and hydrography we aimed to identify the main larval transport retention characteristics in the study area which constitutes the southernmost p monodon fishing grounds embedded in the humboldt current system we hypothesized that the main contribution to population renewal originates in the two persistent adult aggregations close to the nursery ground that occurs over a continental shelf terrace limited by two submarine canyons two extensive bio physical field campaigns were carried out during the main 2001 2002 upwelling season field data indicated that larvae were released from late austral winter to spring from spots to the north and south of the nursery zoea i were found mainly below 50 m depth in southward flowing waters whereas older zoea dominated in northward flowing layers above 50 m larvae were circumscribed between the coast and the shelf break front and pelagic retention areas were identified over the widest shelf area megalopa and juveniles during march were only found over the nursery area individual based simulations coupled to the output of a hydrodynamic model climatological configuration for the studied area showed that the release sites close to the nursery made the largest contribution to recruitment sites further north could also contribute to recruitment if hatching occurred later in the upwelling season the contribution of vertical behavior to larval success was also important as was the former s interaction with the site and time of larval release our results support the relevance of coastal circulation affected by topography on the persistence of p monodon populations off southern chile and the modulation of temporal variability these results might apply to other abundant species in the area

preservation of larval bivalve shells in a radiolarian chert in the late triassic early norian interval of the malampaya sound group calamian island western philippines abstract silicified thin larval bivalve shells occur in upper triassic radiolarian chert early norian in the liminangcong formation of the malampaya sound group part of a late jurassic to early cretaceous subduction related accretionary complex in the north palawan block western philippines the bivalve bearing radiolarian chert which we term bivalve chert is considered to be a deep sea sediment that accumulated in an open ocean realm of the panthalassa ocean radiolarian and conodont biostratigraphies indicate an early norian deposition of the thin shelled bivalves the bivalve morphology thin shells less than 30 m thick smooth ornamentation and small size less than 1 3 mm long suggests they represent larval shells although their taxonomic identity cannot be established with certainty halobiid bivalves that lived in norian times apparently had such a planktonic larval mode of life

dynamical analysis of the upwelling circulation off central chile 1 in this article we analyze the momentum and vorticity balances of a numerical simulation of the upwelling circulation off central chile 34 40 s and its response to interannual local wind changes our analysis indicates that the path of the upwelling jet is strongly controlled by the bottom topography this topographic steering causes the jet to separate from the coast at the punta lavapie cape 37 s although the zeroth order momentum balance is dominated by the geostrophic terms the circulation is also affected by nonlinear processes which lead to the formation of large meanders and the shedding of cyclonic eddies north of punta lavapie during periods of wind relaxation the relative contributions of the zeroth order vorticity balance and the advective terms are also strongly controlled by changes in the coastline geometry and the bottom topography vorticity is created along the current axes and transported toward the coast and the peru chile trench where it dissipates south of punta lavapie the across shelf transports are weaker with equatorward flows that are more stable than in the north additional numerical simulations

dynamics of seasonal and interannual variability of the peru chile undercurrent 1 coastal sea level current satellite altimeter data and an equatorial kelvin wave model are used to study the dynamics of seasonal and interannual fluctuations of the peru chile undercurrent satellite altimetry shows that low frequency sea level anomalies near 30 s propagate offshore as expected from rossby wave theory those anomalies are related to disturbances of equatorial origin observed near the coast of south america with a wind forced equatorial kelvin wave model and simple rossby wave dynamics we show that much of the sea level anomalies and more than 50 of the observed undercurrent variability near 30 s at seasonal and interannual periods can be explained by long rossby waves forced by the equatorial kelvin waves the amplitude of the equatorial kelvin wave can be used to estimate the amplitude of the rossby wave near the south american coast and thus to monitor low frequency changes in the peru chile undercurrent

altimeter observations of the peru chile countercurrent data from geosat and topex altimeters are used to infer the structure of the peru chile countercurrent a jet that flows from at least as far north as 10 s historical data suggests 7 s to 35 40 s maintaining its position between approximately 100 300 km offshore although the annual mean current cannot be determined from altimeter observations the nearly antisymmetric patterns in spring and fall combined with historical observations suggest that the countercurrent is poleward at most times and is maximum in spring and minimum in fall previous studies have linked the offshore countercurrent at 7 s to the equatorial undercurrent west of the galapagos islands suggesting that the countercurrent is part of a continuous flow that extends from the western equatorial pacific to the region off chile between 35 40 s

zooplankton distribution and dynamics in a north pacific eddy of coastal origin ii mechanisms of eddy colonization by and retention of offshore species abstract mesoscale anticyclonic eddies form annually in late winter along the eastern margin of the subarctic north pacific eddies that originate off the southern tip of the queen charlotte islands near 52 n 132 w are called haida eddies during the subsequent 1 3 years they propagate westward into the alaska gyre enroute the eddies are colonized by zooplankton originating from the central british columbia continental shelf the continental slope and along slope boundary current and the oceanic alaska gyre eddies also gradually lose kinetic energy water properties and biota to the surrounding ocean in this paper we analyze zooplankton samples from haida eddies obtained in late winter early summer and autumn of 2000 and in early summer and autumn of 2001 and compare the within eddy zooplankton distributions abundances and community composition of the oceanic origin species to observations from the continental margin and alaska gyre source regions most between region comparisons were consistent with a hypothesis that the eddy zooplankton are a mixture intermediate in abundance and community composition between the bc continental margin and offshore alaska gyre source regions although usually closer to the alaska gyre however about 30 of the comparisons showed within eddy abundances higher than in either source region this outcome cannot arise from mixing alone aggregation and retention appear to be linked to vertical distribution behavior most of the successful taxa spend much of their time below the surface mixed layer this minimizes their exposure to wash out by three physical processes slow upwelling and surface divergence that accompanies weakening of the anticyclonic geostrophic currents rapid but intermittent flushing of the surface layer by ekman transport during strong wind events exchange across the eddy margin geostrophic streamlines caused by temporary displacement by wind driven inertial currents

friction frontogenesis and the stratification of the surface mixed layer the generation and destruction of stratification in the surface mixed layer of the ocean is understood to result from vertical turbulent transport of buoyancy and momentum driven by air sea fluxes and stresses in this paper it is shown that the magnitude and penetration of vertical fluxes are strongly modified by horizontal gradients in buoyancy and momentum a classic example is the strong restratification resulting from frontogenesis in regions of confluent flow frictional forces acting on a baroclinic current either imposed externally by a wind stress or caused by the spindown of the current itself also modify the stratification by driving ekman flows that differentially advect density ekman flow induced during spindown always tends to restratify the fluid while wind driven ekman currents will restratify or destratify the mixed layer if the wind stress has a component up or down front i e directed against or with the geostrophic shear respectively scalings are constructed for the relative importance of friction versus frontogenesis in the restratification of the mixed layer and are tested using numerical experiments of mixed layer fronts forced by both winds and a strain field the scalings suggest and the numerical experiments confirm that for wind stress magnitudes mixed layer depths and cross front density gradients typical of the ocean wind induced friction often dominates frontogenesis in the modification of the stratification of the upper ocean the experiments reveal that wind induced destratification is weaker in magnitude than restratification because the stratification generated by up front winds confines the turbulent stress to a depth shallower than the ekman layer which enhances the frictional force ekman flow and differential advection of density frictional destratification is further reduced over restratification because the stress associated with the geostrophic shear at the surface tends to compensate a down front wind stress

demographics of mesoscale eddies in the california current 1 demographics and variability of persistent mesoscale eddies in the california current have been investigated in a systematic manner using a decade 1995 2004 of merged satellite altimeter data the number of persistent eddies formed each year varied almost 3 fold 4 fold for cyclones anticyclones and was strongly modulated by the 1997 1998 el nino event over the 10 year period cyclone formation was maximum in both winter and summer while maximum anticyclone formation occurred only in winter the majority of long lived eddies 70 day lifespan originated seaward of the 1000 m isobath and with the exception of 2 anticyclones did not form between 45 and 50 n maximum westward propagation of long lived eddies was almost 800 km with similar mean propagation speeds for cyclones and anticyclones

pattern formation at the ocean surface sargassum distribution and the role of the eddy field positively buoyant organisms such as the macroalga sargassum and the cyanobacterium trichodesmium often form surface accumulations visible in satellite imagery that have lateral scale separation of tens of kilometers and cannot be explained by langmuir circulation here we discuss the accumulation of floating materials in the ocean in presence of meso and submesoscale activity using high resolution simulations of the ocean mesoscale in both idealized a 3 dimensional box where coherent eddies are forced by small scale winds and realistic domains western gulf of mexico where extensive concentrations of floating sargassum have been recorded in satellite images we show that the distribution of tracers at the ocean surface departs rapidly from that observed a few tens of meters below it such distribution does not resemble that observed for passive tracers in quasi geostrophic turbulence the strong divergence and convergence zones generated at the surface by ageostrophic processes in the submesoscale range are responsible for the creation of areas where the floating material accumulates floating particles are expelled from the core of mesoscale eddies and concentrate in convergence regions in patterns comparable to the ones observed through the satellite images in light of those results sargassum and or trichodesmium may provide a useful proxy to track convergence divergence processes resulting from ageostrophic processes at the ocean surface

a mechanism for enhanced upwelling off central chile eddy advection 1 a regional numerical model is developed for the mid chile shelf and ocean circulation 30 s to 43 s the model is forced with mean summertime wind stress and transports from a global model over the first 10 days deep 250 300 m peru undercurrent puc water is upwelled to depths of 170 270 m after this time upwelling by the steady winds is largely shut down and a 55 km diameter cyclonic eddy is found to grow in deep water off punta lavapie the mechanism for eddy growth is identified to be baroclinic instability of an initial offshore meander of the equatorward chile coastal current ccc over a period of more than 100 days the onshore arm of the deep water eddy upwells puc water to depths of 150 m toward the shelf a shallow headland eddy then sweeps this puc water to depths of less than 50 m and into the gulf of arauco the net upwelling of 200 m is the largest found for the region observational evidence is cited for the existence of the deep water cyclonic eddy over a period of 4 months a spatially intermittent puc is also found to lie below the ccc in agreement with observational studies the model also predicts the existence of an offshore branch of the ccc that is directed to the northwest

seasonal dynamics of the near surface alongshore flow off central chile 1 the seasonal cycle of the near surface circulation off central chile was analyzed using satellite altimetry and an oceanic model to evaluate the role of the wind stress curl on the circulation we performed two identical simulations except for the wind forcing the control run used long term monthly mean wind stress and the no curl run used a similar wind stress field but without curl the observed and modeled control run surface currents showed a strong seasonal cycle and a well defined equatorward flow with a jet like structure this jet develops during spring and summer consistent with the presence of a low level wind jet south of punta lavapie cape 37 s the equatorward surface current remains close to the coast after the flow passes this cape however it separates to become an offshore jet in contrast in the no curl simulation the separation at punta lavapie is not observed and the offshore jet farther north is not present demonstrating the importance of the wind stress curl on the dynamics of this flow although the offshore integrated sverdrup transport was similar to the model transport the offshore jet was not located where the wind stress curl was maximum instead the position of the jet followed approximately the zero wind stress curl which corresponds to the climatological location of the low level wind jet axis these results illustrate the importance of the offshore upwelling downwelling associated with curl driven ekman pumping which tilts isopycnals upward downward toward the east west of the wind jet forcing a northward flow through thermal wind balance

interannual variability of the subsurface eddy field in the southeast pacific the southeast pacific which encompasses the coasts of peru and chile is one of the world s most productive regions resulting principally from the upwelling of subsurface nutrient rich waters over the satellite altimetry era there have been numerous evidence that surface mesoscale eddies play an important role in the offshore transport of rich coastal waters but it has been only recently that few observational numerical studies have highlighted the importance of the subsurface eddies the eddy field variability is explored using the results of a high resolution model experiment from 1979 to 2012 the model results indicate an asymmetry of the surface and subsurface eddy fields while surface intensified cyclones are slightly more frequent than anticyclones the subsurface field is dominated by anticyclones intrathermoclineeddies ites triggered by the instability of the subsurface peru chile undercurrent pcuc composite maps are consistent with in situ observations ites are associated with maximum vorticity around 150 200 m depth warmer and more saline core characteristic of the equatorial subsurface water from the pcuc we find that the variability of the ites is significantly correlated with the enso equatorial signal during strong el nino events e g 1982 1998 we find that while the pcuc transport increases the volume of coastal waters transported by ites however decreases during those periods we find that the relaxation of the isopycnals along the coast during el nino events leads to weakened baroclinic instability and to a decrease of the ites transport

how biophysical interactions associated with sub and mesoscale structures and migration behavior affect planktonic larvae of the spiny lobster in the juan fernandez ridge a modeling approach abstract the juan fernandez ridge jfr is a chain of topographical elevations in the eastern south pacific 33 35 s 76 81 5 w rich in endemic marine species this ridge is frequently affected by the arrival of mesoscale eddies originating in the coastal upwelling zone off central southern chile the impacts of these interactions on the structure and dynamics of the jfr pelagic system have however not been addressed yet the present model based study is focused on the coupled influence of mesoscale submesoscale processes and biological behavior i e diel vertical migration on the horizontal distribution of planktonic larvae of the spiny lobster jasus frontalis around the jfr waters two case studies were selected from a hydrodynamic regional ocean modeling system to characterize mesoscale and submesoscale structures and an individual based model ibm to simulate diel vertical migration dvm and its impact on the horizontal distribution and the patchiness level dvm behavior of these larvae has not been clearly characterized therefore three types of vertical mechanisms were assessed on the ibm 1 no migration lg 2 a short migration 0 50 m depth dvm1 and 3 a long migration 10 200 m depth dvm2 the influence of physical properties eddy kinetic energy stretching deformation and divergence on larval aggregation within meso and submesoscale features was quantified the patchiness index assessed for mesoscale and submesoscale structures showed higher values in the mesoscale than in the submesoscale however submesoscale structures revealed a higher accumulation of particles by unit of area both vertical migration mechanisms produced larger patchiness indices compared to the no migration experiment dvm2 was the one that showed by far the largest aggregation of almost all the aggregation zones larval concentrations were highest in the submesoscale structures these zones were characterized by low eddy kinetic energy negative stretching deformation and slight convergence stretching deformation flow appeared to be triggered by the eddy eddy interactions and the robinson island barrier effect and it likely promotes the aggregation of the spiny lobster larvae in the juan fernandez system these results highlighted the importance of the coupled effect of physical mesoscale and submesoscale oceanographic features and biological processes dvm in the generation of larval patchiness and concentration of spiny lobster larvae around the jfr which could be key for their survival and retention in those waters

origin and dynamics of mesoscale eddies in the catalan sea nw mediterranean insight from a numerical model study past observations and satellite sea surface temperature imagery indicate the presence of mesoscale anticyclonic eddies drifting along the catalan coast in september 2001 one of these anticyclonic eddies was surveyed over the shelf break during an oceanographic cruise which permitted the 3 d description of its structure in this work we investigate the origin and dynamics of such catalan eddies using a numerical circulation model of the northwest mediterranean at 3 km resolution driven by high resolution atmospheric analyses and compare model eddies with the observations in the catalan sea we identify two zones of eddy formation in the gulf of lions in front of the city of marseille and at the southeast of coast of roussillon from which anticyclonic eddies are observed to drift toward the catalan sea the hydrology and dynamics of the structures observed in the simulations are characterized sensitivity experiments and energy analysis are performed which allow us to identify the mechanisms associated with their generation properties of the eddy observed during the 2001 cruise at the catalan shelf break are found to compare well with model eddies generated at the southeast of the roussillon coast the model relates the origin of these eddies to the separation of the coastal current downstream from creus cape flow separation is linked to intense downwelling taking place in front of the roussillon coast when strong northwesterly winds events occur

a census of meddies tracked by floats recent subsurface float measurements in 27 mediterranean water eddies meddies in the atlantic are grouped together to reveal new information about the pathways of these energetic eddies and how they are often modified and possibly destroyed by collisions with seamounts twenty meddies were tracked in the iberian basin west of portugal seven in the canary basin during february 1994 14 meddies were simultaneously observed 11 of them in the iberian basin most 69 of the newly formed meddies in the iberian basin translated southwestward into the vicinity of the horseshoe seamounts and probably collided with them some meddies 31 passed around the northern side of the seamounts and translated southwestward at a typical velocity of 2 0 cm s into the canary basin some meddies observed there were estimated to be up to 5 yr old four meddies in the canary basin collided with the great meteor seamounts and three meddies were inferred to have been destroyed by the collision overall an estimated 90 of meddies collided with major seamounts the mean time from meddy formation to a collision with a major seamount was estimated to be around 1 7 yr combined with the estimated meddy formation rate of 17 meddies yr from previous work this suggests that around 29 meddies co exist in the north atlantic therefore during february 1994 we observed about half of the population of meddies

water masses in the humboldt current system properties distribution and the nitrate deficit as a chemical water mass tracer for equatorial subsurface water off chile abstract three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern south pacific and their distributions oceanographic data were taken from the scorpio may june 1967 piquero may june 1969 and krill june 1974 cruises vertical sections of temperature salinity dissolved oxygen nitrate nitrite phosphate and silicate were used to analyze the water column structure five water masses were identified in the zone through t s diagrams subantarctic water subtropical water equatorial subsurface water antarctic intermediate water and pacific deep water their proportions in the sea water mixture are calculated using the mixing triangle method vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m several characteristic oceanographic features in the study area were analyzed the shallow salinity minimum displacement towards the equator the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south and the equatorward intermediate antarctic salinity minimum associated with a dissolved oxygen maximum the nitrate deficit generated in the denitrification area off peru and northern chile is proposed as a conservative chemical tracer for the equatorial subsurface waters off the coast of chile south of 25 s

diagenesis of bivalves from jurassic and lower cretaceous lacustrine deposits of northeastern china in contrast to the numerous excellently preserved arthropods vertebrates and plants from the mesozoic lacustrine fossil lagerstatten of northeastern china which have calcium phosphate or organic skeletons the preservation of taxa with a calcareous skeleton is fairly poor here we investigate using a scanning electron microscope and energy dispersive x ray spectrometer the preservational modes of bivalves from the jurassic daohugou fossil beds of inner mongolia and the lower cretaceous yixian formation of eastern liaoning the jurassic bivalve ferganoconcha sibirica is preserved as strongly compressed composite moulds which contain remains of the organic periostracum in the yixian formation the bivalves sphaerium anderssoni and arguniella ventricosa occur as compacted internal external or composite moulds or are preserved with a silicified shell and rarely with a shell consisting of iron hydroxides which had replaced pyrite during late diagenesis weathering silicification produced partly fabric replacive microcrystalline quartz and partly void filling megaquartz crystals after the carbonate shell had been dissolved films of authigenic aluminosilicate minerals partly secondarily silicified cover the exterior and interior shell surfaces occasionally early diagenetic pyrite crystals now oxidized to iron hydroxides filled shell cavities forming internal moulds and rarely replaced the bivalve shell the poor preservation of the bivalves reflects the environment and water chemistry of these lakes which were heavily influenced by volcanic processes frequent ash deposition and decomposition of volcanic glass particles created acidic and alkaline lake and interstitial waters which led to early diagenetic formation of authigenic aluminosilicate minerals ferruginous internal moulds dissolution of shell carbonate and silicification of shells

interactions between dissolved silica and carbonate minerals an experimental study at 25 50 c abstract replacement of carbonate minerals by silica polymorphs in marine and meteoric environments is a common early diagenetic feature of sedimentary rocks although relatively few experimental investigations have been made of interactions between carbonate minerals and dissolved sio 2 at moderate temperatures available data suggest that silica uptake onto carbonate surfaces can be significant we present results of experiments conducted between 25 and 50 c of the uptake of aqueous sio 2 from artificial seawater mg na cl ca hco 3 i 0 7 and meteoric type cacl 2 na 2 co 3 i m a reasonable upper limit for natural diagenetic waters dissolved silica carbonate mineral interactions were investigated under three experimental conditions 1 in solutions near equilibrium with respect to calcite 2 in calcite seeded precipitation experiments at fixed degrees of calcite supersaturation and 3 during closed system dissolution precipitation of metastable carbonate minerals aragonite and 18 mole mg calcite to low mg calcite lmc in artificial seawater asw maintained near equilibrium with respect to calcite at various p co2 values silica uptake from solution onto calcite surfaces 1 15 mol si gram seed was irreversible and strongly time and ph dependent the rate of uptake was greatest in the first 5 hr and in solutions of lower ph higher p co2 silica uptake was only nominally dependent on solution mg and temperature over the range studied silica uptake was greater in asw than in otherwise comparable experiments conducted in low ionic strength solutions controlled calcite precipitation rates were unaffected by the adsorption of silica during recrystallization of aragonite and mg calcite in low ionic strength solutions silica uptake 1 6 mol g was similar to values frorn near equilibrium experiments for synthetic calcite in asw experimental si adsorption values were comparable to si adsorption values determined for modem metastable sediments 3 4 mol g 1 despite considerable variation in the experimental carbonate equilibrium disequilibrium mineralogy and solution chemistry si uptake at near surface and moderate burial conditions 25 50 c was limited to 15 mol g 1 si even in solutions maintained near opal ct saturation over a period of days to weeks

sub mesoscale coastal eddies observed by high frequency radar a new mechanism for delivering nutrients to kelp forests in the southern california bight 1 sub mesoscale eddies are described along the mainland coast of the santa barbara channel based on observations from a network of high frequency hf current measuring radars and near shore moorings the eddies are 4 15 km in diameter and typically last about 2 days although some last up to 6 days most eddies within the radar coverage area are anti cyclonic with relative vorticities of 0 4 f to 0 8 f where f is the coriolis parameter but cyclonic eddies are also observed moored observations over the inner shelf 12 m water depth of a sequence of two eddies in december 2001 show an increase in nitrate plus nitrite from the background levels of 1 2 m to a maximum of 10 12 m when the eddies are present we speculate that these eddies are an important transport mechanism for nutrients and biogenic particles to inner shelf ecosystems of the southern california bight

divergent pathways of cyclonic and anti cyclonic ocean eddies satellite altimetry is used to study the propagation pathways of warm and cold ocean eddies in different ocean basins we consider eddies that have a life span longer than 3 months and we present three regional studies in the southeast indian the southeast atlantic and the northeast pacific oceans the case studies show that simple theories for vortex propagation on a plane work in regions where energetic eddies propagate though a weak background flow under these conditions anticyclonic cyclonic eddies propagate westward and equatorward poleward this divergence in the eddy pathways implies a net equatorward eddy heat flux and has implications for the meridional transport of freshwater carbon nutrients etc

the distribution of chlorophyll a and dominant planktonic components in the coastal transition zone off concepcion central chile during different oceanographic conditions abstract the oceanographic setting and the planktonic distribution in the coastal transition zone off concepcion 35 38 s 73 77 w an area characterized by its high biological production were assessed during two different seasons austral spring with equatorward upwelling favorable winds and austral winter with predominately northerly winds oceanographic and biological data total chlorophyll a particulate organic carbon microplankton large mesozooplankton 500 m as potential consumers of microplankton were obtained during two cruises october 1998 july 1999 together with satellite imagery for wind stress geostrophic flow surface temperature and chlorophyll a data the physical environment during the spring sampling was typical of the upwelling period in this region with a well defined density front in the shelf break area and high concentrations of surface chlorophyll a 5 mg m 3 on the shelf over the itata terrace during the winter sampling highly variable though weakly upwelling favorable winds were observed along with lower surface chlorophyll a values 100 km from the coast cyclonic and anti cyclonic eddies were evident in the flow field during both periods the former coinciding with higher chlorophyll a contents 1 mg m 3 than in the surrounding waters also a cold chlorophyll a rich filament was well defined during the spring sampling extending from the shelf out to 350 400 km offshore along a cross shelf transect the micro and meso planktonic assemblages displayed higher coastal abundances during the spring cruise but secondary peaks appeared in the oceanic area during the winter cruise coinciding with the distribution of the eddies these results suggest that the mesoscale features in this region in combination with upwelling play a role in potentially increasing the biological productivity of the coastal transition zone off concepcion

mechanism and controls of silicification of fossils in limestones silicification of calcitic fossils occurs along thin solution films at which calcite dissolves and silica precipitates the mechanism is replacement controlled by force of crystallization whereby the growth of the silica phase exerts pressure across the silica carbonate contact increasing the gibbs free energy and hence solubility of shell calcite physical evidence for force of crystallization controlled replacement includes restriction of carbonate dissolution to the silica carbonate contact and euhedral quartz terminations at some quartz calcite contacts correlations among some replacement quartz types and fossil taxa indicate that shell microstructure and bulk pore water silica concentration control replacement quartz type

too low δ18o of paleo meteoric low latitude water do paleo tropical cyclones explain it abstract isotopic analysis of rock samples showed anomalously 18 o depleted reconstructed isotopic composition of paleo meteoric water over southern israel between the late cretaceous and the early miocene with 18 o w as low as 14 smow this range is significantly lighter than the expected values for rain at the relevant paleo latitudes 8 n to 25 n it is similar or lighter than areas with meteoric water at the present climate in which rainfall contribution from tropical cyclone tc is significant rainfall from tcs is 18 o depleted because of the recirculation of the vapor into repeated precipitation or distillation cycles a paleo geographic reconstruction of the region shows that throughout the period there was a warm ocean to the east and southeast of the relevant area thus tcs formed over the ocean and made landfall on the coastline at a distance of 300 to 400 km to the east the reconstructed composition of the rainwater implies dominance of tcs at these times furthermore the combination of warmer seas and lighter rainwater than at present suggests that the tcs were more dominant than in the most tc prone coastal areas at the present climate the results of the present study suggest that climate during the relevant time periods was very different from the present with tc activity similar or exceeding the most tc prone locations in the world at the present climate this might also hint that warmer sea waters in the geological past were conducive to greater tc activity than in the present climate answering this question requires additional research

mean surface circulation and mesoscale turbulent flow characteristics in the eastern south pacific from satellite tracked drifters 1 circulation of the eastern south pacific region 10 34 s 70 100 w was studied using drifting buoy trajectories from 1979 to 2003 three different current regimes were highlighted the south equatorial current flowing westward north of 26 s with surface velocities of 7 8 cm s 1 the south pacific current an eastward current of 2 cm s 1 south of 25 30 s and the chile peru current a northwestward flow of 6 cm s 1 found to the east of 82 w and south of 22 s the velocity variance distribution showed the regional flow to be anisotropic in nature maps of eddy kinetic energy obtained from drifter measurements and satellite altimetry data showed similar patterns with higher energy levels near the south american coast the lagrangian time and length scales of the turbulent flow revealed typical values of 5 9 0 6 days and 40 7 5 4 km in the zonal direction and of 3 5 0 4 days and 29 3 4 km in the meridional direction the estimated diffusivities were 4 9 0 5 107 cm2 s 1 and 2 6 0 3 107 cm2 s 1 in the eastward and northward directions respectively finally we estimated the respective role of horizontal advection and lateral diffusion on the mixed layer heat and salt budgets near the coast the lateral turbulent fluxes in the surface layer were two times larger than the horizontal transports associated with the large scale circulation mean horizontal heat and salt diffusive fluxes were around 25 w m 2 and 50 g m 2 d 1

eddy activity in the four major upwelling systems from satellite altimetry 1992 2007 eddy activity in the four major eastern boundary upwelling systems ebus is investigated using 15 years of satellite altimetry data based on the analysis of more than 4000 long lived eddy trajectories in every ebus we show that mesoscale structures are mainly generated along the continental coasts and south of the main archipelagos and propagate westward with velocities increasing toward the equator these mesoscale eddies having radii of 70 160 km are then frequently observed along the coastal transition zones and frontal regions and some large oceanic areas are preferentially populated by cyclonic or anticyclonic eddies temporal variations of the number of newly formed eddies and the associated eddy activity index defined as the mean eddy energy density are finally examined at seasonal and interannual scales the strongest seasonal interannual respectively variations are observed in the california benguela upwelling systems the proposed indices also exhibit contrasted long term trends in each ebus which suggests that eddy activity might be sensitive to a warming climate

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

equilibrium structure and dynamics of the california current system this paper addresses the structure and dynamical mechanisms of regional and mesoscale physical variability in the subtropical northeast pacific ocean using the regional oceanic modeling system roms the model is configured with a u s west coast domain that spans the california current system ccs with a mesoscale horizontal resolution up to as fine as 3 5 km its mean seasonal forcing is by momentum heat and water fluxes at the surface and adaptive nudging to gyre scale fields at the open water boundaries its equilibrium solutions show realistic mean and seasonal states and vigorous mesoscale eddies fronts and filaments the level of eddy kinetic energy eke in the model is comparable to drifter and altimeter estimates in the solutions with sufficiently fine resolution because the model lacks nonseasonal transient forcing the authors conclude that the dominant mesoscale variability in the ccs is intrinsic rather than transiently forced the primary eddy generation mechanism is the baroclinic instability of upwelling alongshore currents there is progressive movement of meanseasonal currents and eddy energy offshore and downward into the oceanic interior in an annually recurrent cycle the associated offshore eddy heat fluxes provide the principal balance against nearshore cooling by mean ekman transport and upwelling the currents are highly nonuniform along the coast with important influences by capes and ridges in both maintaining mean standing eddies and launching transient filaments and fronts

late cretaceous quartz geodes after anhydrite from burgos spain quartz geodes cauliflower like appear in a specific level of the late cretaceous north of burgos due to their anhydrite relicts and spherulitic quartz length slow chalcedony they are considered as pseudomorphs of anhydrite nodules formed during early diagenesis at the same level compact chert nodules sporadically appear presenting a considerable amount of sponge spicules with fibrous texture length fast chalcedony the silicification of the anhydrite nodules took place before total compaction and cementation of the sediment the source of silica is principally biogenic sponge spicules there is no link between the depositional environment and the existence in itself of anhydrite nodules indirectly it is possible to see the effects of an arid climate which have not been recorded in the lithologic column here described modified journal abstract

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

coastal transition zone off chile 1 seven years of subsurface current observations at deep sea and continental slope moorings off chile 30 s satellite sea surface anomaly and satellite wind stress are used to examine space time and propagation characteristics of the mesoscale eddy activity in the coastal transition zone off chile this zone off chile extends from the coast to 600 800 km offshore and can be separated into two latitudinal regions the first region between 29 and 39 s off central chile is characterized by high eddy kinetic energy and strong but variable equatorward wind stress the second region between 19 and 29 s off northern chile is characterized by low eddy kinetic energy and weak but persistent equatorward wind stress low frequency mesoscale variability off central chile is mainly associated with baroclinic instability of coastal currents and westward propagation of rossby waves from the eastern boundary and is strongly modulated over el nino la nina cycles application of a new rotary wavelet spectrum method to the recording current meter data and the use of current estimates from satellite altimeter data show that mesoscale eddies and meanders in the coastal transition zone fluctuate with periods centered on 120 days and with length scales centered on 200 km cross rotary wavelet analyses of currents and wind stress indicate that fluctuations of coastal currents with periods longer than 220 days propagated westward as free rossby waves during 1995 1996 and as forced rossby waves during 1999 2001

seasonal variability of coastal upwelling and the upwelling front off central chile 1 we analyze sea surface temperature sst and chlorophyll a chl a satellite data to study the seasonal variability of the upwelling off central chile data from an oceanographic cruise are used to illustrate the vertical characteristics of the upwelling front and the geostrophic flow the mean offshore extension of the sst front in summer is 110 km there sst changes from 13 5 c near the coast to 14 5 15 c offshore hydrographic data show that the thermocline becomes progressively shallower toward the coast but that at a certain distance it abruptly bends to form a horizontal front that extends until 50 m depth satellite data show that the chl a decays exponentially offshore and a concentration of 1 mg m 3 indicates the offshore limit of the frontal region the sst front observed most of the year is absent in winter when the coastal water is only slightly colder than the oceanic one however relatively higher chl a values remain present near the coast during winter northwest of punta lavapie 37 15 s the frontal region is located progressively farther offshore suggesting that a branch of an equatorward surface jet separates from the coast to form a meander which is associated with a filament of cold water and an anticyclonic eddy observed frequently in this zone during summer hydrographic data show that isotherm and current disturbances related to mesoscale eddies can extend several hundreds of meters below the surface in contrast the coastal jet is quite shallow extending until 150 m depth

seasonal and interannual variability of currents and temperature off central chile results are reported for continuous 6 year records of current and temperature from a continental slope station at 308s off chile these observations for november 1991 to november 1997 span the moderate weak and strong el nino events of 1991 1992 1994 and 1997 and the la nina event of 1995 1996 results for current and temperature are analyzed together with observations of wind along the south american coast from the ers 1 and 2 satellite scatterometers wind from a local coastal site sea level from northern and central chile sea surface temperature anomalies from the south pacific region and traditional el nino indices mean poleward flow of 12 8 cm s 21 was observed for the 6 year period in the core of the peru chile undercurrent 220 m mean flow in the depth range of antarctic intermediate water 750 m was equatorward at 1 1 cm s 21 intraseasonal scale variability associated with coastal trapped waves was weaker during the austral winter greatest during el nino events and weakest during the la nina event winds adjacent to the coast showed a strong annual cycle with a southward progression of maximum equatorward upwelling favorable winds alongshore flow over the slope exhibited strong semiannual and weaker annual variations poleward flow in the undercurrent was strongest in the austral spring and fall and weakest in the winter near the bottom 750 m seasonal scale variability was less intense but led that higher up in the water column 220 m by 1 month strong interannual variability of alongshore current and temperature was found at all depths over the slope whereby changes at depth led changes higher up a rapid warming event was observed at the end of 1996 beginning of 1997 over the slope this event also seen in sea level and sea surface temperature off chile led el nino indices by several months and may be best explained by local wind anomalies coupled to atmospheric teleconnections from the western tropical pacific at the onset of el nino some aspects of our current and temperature observations are consistent with results from eastern boundary current models our results indicate that both ocean and atmosphere pathways from the equatorial pacific contribute significantly to interannual scale variability of alongshore flow and thermocline depth off chile

petrology and diagenetic evolution of neoproterozoic ooids libby formation western montana u s a abstract radial concentric and twinned sparry ooids from the upper belt supergroup originally formed as mixed mg calcite and aragonite and aragonite textural evidence suggests that mg calcite ooids may have formed along with the ooids having an original aragonite mineralogy strontium concentrations of 2400 to 2900 ppm support an aragonitic precursor to the twinned sparry ooids and sr values of 2500 ppm strongly suggest that the radial concentric ooids had an aragonitic component in addition to the mg calcite suggested by the preserved fabric trace element mn mg fe and sr values of ooids and early carbonate cements suggest that diagenetic trends for these proterozoic carbonates are similar to those established for their phanerozoic and archean counterparts mg fe and mn increase and sr decreases with successively later carbonate phases

a numerical study of the seasonal variability in the circulation off central chile the princeton ocean model is used to study the coastal ocean circulation off central chile between 30 and 45 s and its seasonal transitions in response to monthly mean climatological wind stress and surface heat flux the model reproduces many of the dominant circulation features including an equatorward coastal current coastal upwelling and a poleward undercurrent to get the correct seasonal variability in the undercurrent it was necessary to prescribe the inflow of the undercurrent on the northern model boundary meanders and eddies form throughout the simulation period seaward of the coastal current in response to baroclinic instability of the flow the flow associated with the meanders shows upwelling in the shoreward flow and downwelling in the seaward flow this upwelling downwelling pattern is explained by conservation of relative vorticity in the flow the upwelling velocity associated with the meanders corresponds to a vertical migration of 15 30 m over a typical timescale of the meanders of 1 2 months it is argued that this upwelling may be important for maintaining observed high phytoplankton biomass and primary production seaward of the coastal zone directly affected by wind driven upwelling

eddy characteristics in the eastern south pacific 1 the main eddy characteristics length scales rotation period swirl and translation velocities are determined in the eastern south pacific region 10 35 s and 70 100 w based on surface drifter measurements satellite altimetry and hydrographic data from the woce p19 section the chile peru current eddies have a typical diameter of order of 30 km smaller than the typical rossby radii observed in the region they are principally formed near the south american coast and propagate seaward with a translation velocity varying from 3 cm s 1 in the southern part of the study domain to 6 cm s 1 north of 15 s long lived anticyclonic eddies propagate northwestward with a mean angle of around 333 t whereas cyclonic vortices propagate westward consistent with the vortices propagation theory on a plane the radial distribution of the swirl velocity shows that the chile peru current eddies have a maximum diameter of order 200 km with a swirl velocity of around 14 cm s 1 and a rotation period of 50 days hydrographic data reveal a vertical extent down to around 2000 m for energetic eddies no significant difference is observed between the tangential velocities of cyclonic and anticyclonic eddies geostrophic balance can be considered for large radii whereas ageostrophic dynamics may play an important role near the eddy centers

el nino variability in simple ocean data assimilation soda 1871 2008 1 a new ocean reanalysis that covers the period from 1871 to 2008 is used to explore the time evolving characteristics of el nino the new reanalysis assimilates all available hydrographic and sea surface temperature data into a model of the global ocean forced with surface boundary conditions from an atmospheric reanalysis that also covers the period from 1871 through 2008 using traditional measures of el nino our reanalysis shows that the timing of el nino events is in agreement with sea surface temperature reconstructions but el nino in the reanalysis is stronger particularly from 1871 to 1920 a new index based on the first moment of the temperature anomaly is introduced the new index is used to characterize the strength and location of el nino events and has the advantage that it is independent of the location of el nino using the new index el nino in the reanalysis shows prominent decadal variability of strength but relatively little long term trend el nino events were strong in the last part of the 19th century and first part of the 20th century and again in the latter part of the 20th century with weak el nino events in the middle of the 20th century the location of el nino also varies considerably ranging from the western to the eastern pacific near the coast of south america however the null hypothesis that the location of el nino can be represented as a random distribution about a central longitude of about 140 w cannot be rejected

silicification of carbonate clasts in a marine environment upper miocene vera basin se spain abstract upper miocene marine sediments in the vera basin se spain contain abundant silicified marble pebbles and bivalves the silicification of these marble pebbles and bivalves represents one of the stages of their sedimentary history associated with small fluctuations in relative sea level during the late tortonian alluvial fan deposits containing the marble pebbles were invaded by the sea which caused reworking of the pebbles and the establishment of a marine biota in the environment after shallow burial numerous marble pebbles and bivalve remains were silicified both types of clasts were partially replaced by opal ct or quartz from opaline silica derived from dissolution of skeletal debris the silicified zones rinds now consist of quartzine or quartz silicification of the clasts must have taken place under shallow burial conditions during early diagenesis while pyrite formed in favourable anoxic sites iron oxides also precipitated during early diagenesis but after silicification finally part of the deposits containing the silicified clasts were transported by gravitational mass flows and redeposited in deeper areas of the basin if the hypothesis proposed for the diagenetic process is correct it indicates that the uncommon silicification of carbonate clasts does not only occur in continental environments in which it has previously been described

magnetostratigraphy of the late cretaceous to eocene sverdrup basin implications for heterochroneity deformation and rotations in the canadian arctic archipelago the temporal and spatial patterns of sedimentation in the sverdrup basin provide clues to how deformation in the canadian arctic accommodated late cretaceous eocene relative motion between greenland and north america although the sediments contain a rich assemblage of mammal and megafloral fossils dating of the sequence has been controversial some work suggests a dramatic faunal and floral heterochroneity with species appearing in the arctic 2 18 m y prior to their appearance at lower latitudes to obtain a chronostratigraphic framework for these sediments a 2 6 km section of the eureka sound group and kanguk formation on western axel heiberg island was sampled for magnetostratigraphy after removal of a pervasive modern field overprint with thermal and alternating field demagnetization a characteristic remanent magnetization chrm is isolated despite high directional dispersion the chrms form 11 distinct polarity intervals which can be correlated to chrons 34 to 24r this correlation indicates that some of these sediments are 10 m y younger than thought previously reducing the need for large scale heterochroneity sedimentation rates derived from the magnetostratigraphy suggest that an increase in basin subsidence is recorded near the middle of the section sampled a similar pattern has been reported from the eureka sound group exposed on ellesmere island we interpret this increased sedimentation as a response to crustal flexure caused by lithospheric loading during the middle paleocene c26r the loading may be related to a blind thrust system to the west of axel heiberg island that marks compression between north america and greenland driven by rapid seafloor spreading in the labrador sea the new data together with prior results indicate that most of the cretaceous canadian arctic archipelago has undergone a counterclockwise vertical axis rotation the new data are more consistent with this rotation being related to events during chron 26r rather than marking block rotations associated with the terminal eocene phases of eurekan deformation

patterns of silicification in permian pelecypods and brachiopods from wyoming abstract silicified pelecypods and brachiopods are common in the ervay franson and grandeur members of the permian park city formation of central and western wyoming study of hundreds of these fossils has resulted in recognition of five patterns of silicification pattern i is characterized by megaquartz crystals projecting inward from and perpendicular to the skeletal boundary whereas fossils exemplifying pattern ii consist of concentric laminae of chalcedonic quartz in pattern iii an outer lamina of microcrystalline quartz grades abruptly inward to laminated chalcedonic quartz which in turn grades abruptly inward to megaquartz shells demonstrating pattern iv involve megaquartz crystals aligned parallel to the skeletal boundary and lying adjacent to beekite discs pattern v consists of megaquartz crystals aligned parallel to the skeletal boundary in brachiopods these crystals typically exhibit relict skeletal microstruture pelecypod wall layers constructed originally of aragonite are characterized by patterns i ii iii and iv pattern v characterizes all brachiopods and originally calcitic layers of pelecypods patterns i ii iii and iv are interpreted to result from filling of voids created by dissolution of skeletal carbonate pattern v results from concurrent carbonate dissolution and silica precipitation

average circulation seasonal cycle and mesoscale dynamics of the peru current system a modeling approach h isolines the pccc appears to be directly forced by the cyclonic wind stress curl the model is able to produce the upwelling front the cold water tongue which extends toward the equator and the equatorial front as described in the literature model seasonal changes in sst and ssh are compared to measurements for the central pcs model eke is 10 to 30 lower than the observations the model eddy diameters follow a strong equatorward increase the injection length scales derived from the energy spectra strongly correlate to the rossby radius of deformation confirming the predominant role of baroclinic instability at 3 s the model solution appears to switch from a turbulent oceanic regime to an equatorial regime dominated by zonal currents

top marine predators track lagrangian coherent structures meso and submesoscales fronts eddies filaments in surface ocean flow have a crucial influence on marine ecosystems their dynamics partly control the foraging behavior and the displacement of marine top predators tuna birds turtles and cetaceans in this work we focus on the role of submesoscale structures in the mozambique channel in the distribution of a marine predator the great frigatebird using a newly developed dynamic concept the finite size lyapunov exponent fsle we identified lagrangian coherent structures lcss present in the surface flow in the channel over a 2 month observation period august and september 2003 by comparing seabird satellite positions with lcs locations we demonstrate that frigatebirds track precisely these structures in the mozambique channel providing the first evidence that a top predator is able to track these fsle ridges to locate food patches after comparing bird positions during long and short trips and different parts of these trips we propose several hypotheses to understand how frigatebirds can follow these lcss the birds might use visual and or olfactory cues and or atmospheric current changes over the structures to move along these biologic corridors the birds being often associated with tuna schools around foraging areas a thorough comprehension of their foraging behavior and movement during the breeding season is crucial not only to seabird ecology but also to an appropriate ecosystemic approach to fisheries in the channel