life history of an anticyclonic eddy 1 we use the trajectory of three buoys dragged below the surface mixed layer together with sea surface temperature imagery to examine the evolution of an anticyclonic warm core eddy since its generation by the canary islands two buoys remain within the eddy during some 100 days and the third one remains almost 200 days while drifting southwestward up to 500 km with the mean canary current the eddy merges with several younger anticyclonic and cyclonic eddies in each occasion suffering substantial changes the eddy core defined as a region with near solid body type rotation and radial convergence initially occupies the whole eddy after interacting with another vortex the inner core markedly slows down although it continues displaying radial convergence and relatively small radial oscillations and an uncoupled outer ring is formed or enhanced which revolves even more slowly and displays large radial fluctuations the vortex extensive life is consistent with its inertially stable character and observations of radial convergence a very simple model of vortex merging where cylinders fuse conserving mass and angular momentum gives fair results the observations suggest that the eddy changes as the result of its own slow evolution and sporadic mixing events from a young stage where the core retains its vorticity and occupies most of the eddy through a mature stage where the eddy has a reduced inner core and a slowly revolving outer ring to a decay stage where the vorticity maximum is substantially reduced

mesoscale eddies in the south china sea observed with altimeter data 1 a composite time series 1993 2000 of sea surface height anomaly from several satellites is used to identify eddies in the south china sea scs the eddy lifetime radius strength and straight line travel distance are estimated altogether 58 anticyclonic eddies and 28 cyclonic eddies are identified for this period they are grouped into four geographical zones according to known eddy generation mechanisms and their statistics are discussed accordingly our geographical classification is a useful first step in gaining an overview of their generation

revisiting the circulation of the east australian current its path separation and eddy field abstract the traditional view of the east australian current eac as depicted in many schematics is of a continuous boundary current that flows along the shelf off eastern australia between approximately 18 s and about 32 5 s where it separates from the coast and continues either towards new zealand along the tasman front or towards tasmania as the eac extension additionally it is widely recognised that eddies are prevalent in the eac region particularly south of the eac separation we revisit this long standing paradigm and suggest that the eac is perhaps better viewed as a continuous meandering stream flowing adjacent to the coast that feeds a field of mesoscale eddies observations show that eac eddies are prevalent over a broad region of the western tasman sea as far north as 25 s typically with maximum intensity between 30 and 35 s at any instant in time the eac jet is usually evident as a poleward stream adjacent to the continental shelf edge other commonly accepted components of the eac system including the tasman front and eac extension are rarely seen as distinct identifiable features rather these features are evident only in time mean fields when the eddy variability is filtered out it is also common for the eac to be spatially discontinuous due to the presence of eddies often with multiple short streams that sometimes separate and re attach to the coast recognition of the eac as an eddy dominated current system has seen many recent studies focus on various aspects of eddies in the eac system providing new insights into mesoscale ocean dynamics recent studies of individual eddies have shown that the circulation within eddies including tilting and vertical motion is more complex than previously understood a summary of these studies along with a review of the eac system particularly its path separation and eddy field is presented here

cases study of nonlinear interaction between near inertial waves induced by typhoon and diurnal tides near the xisha islands nonlinear interaction between near inertial waves niws and diurnal tides dts after nine typhoons near the xisha islands of the northwestern south china sea scs were investigated using three year in situ mooring observation data it was found that a harmonic wave f d 1 hereafter referred to as fd 1 wave with a frequency equal to the sum of frequencies of niws and dts hereafter referred to as f and d 1 respectively was generated via nonlinear interaction between typhoon induced niws and dts after each typhoon the fd 1 wave mainly concentrates in the subsurface layer and is mainly induced by the first component of the vertical nonlinear momentum term the product of the vertical velocity of dt and vertical shear of near inertial current hereafter referred to as component 1 in which the vertical shear of the near inertial current greatly affects the strength of the fd 1 current the larger the component 1 the stronger the fd 1 currents the background preexisting mesoscale anticyclonic eddy near the mooring site may also enhance the vertical velocity of dt and thus component 1 which subsequently facilitates the nonlinear interaction induced energy transfer to the fd 1 wave and enhances the fd 1 currents after the passage of a typhoon

relationships between hornblende k ar ages chemical composition and hydrogen isotopes connemara western ireland evidence for a massive extinct hydrothermal system major element compositional analyses k ar ages d and 18 o values for 30 zoned and unzoned hornblendes from dalradian amphibolites and metagabbros mostly in north connemara are reported although the cooling ages are expected from previous u pb zircon studies to be c 475 450 ma the results obtained are from 556 6 to 410 9 ma with an average of 470 ma fluid movements probably at 275 15 c i e much below ar closure temperature for hornblende erratically reset the ages as is shown by a negative correlation of hornblende d and age and a wide scatter of ages even within 2 m the changes were implemented by h d exchange between fluid and hornblendes in which ionic porosity z influenced the loss of ar and possibly its gain from the fluid to give the excess ar found in some samples z is controlled by hornblende chemical composition high mg si and mg fe and low fe al ti na and particularly low k amphiboles giving low z values retained ar more firmly and gained ar more readily than compositions which had higher z values which gave younger ages these range down to c 400 ma being the age of the intrusion of the galway granite suite that initiated the fluid circulation the scatter of ages is a consequence of incomplete equilibration mainly because of the slow h d exchange rate below 350 c and partly because the fluid permeated erratically in different areas and down cracks of all kinds promoting irregular ar movement the meteoric fluid circulated through connemara the galway granite and at least some of the contiguous silurian sediments of the south mayo trough these overlying sediments may have contributed to the water circulated in north connemara which was slightly less negative d than in central connemara for hornblende k ar ages to be a reliable measure of times of uplift and cooling they need to be demonstrated to be free from the influence of hot fluids by showing no correlation of age with d

anisotropy in seismic velocities and amplitudes from multiple parallel fractures many rock structures include multiple near parallel planar discontinuities such as bedding planes or joints the effects of these nonwelded interfaces on seismic wave propagation are often analyzed using effective moduli in terms of which seismic wave propagation is independent of frequency and without loss unless the moduli include imaginary terms an alternative approach is to treat these interfaces as a boundary condition in the seismic wave equation across which seismic stress is continuous but seismic particle displacements are discontinuous the ratio of the stress to displacement is called the specific stiffness of the interface and characterizes the elastic properties of a fracture for a completely elastic system this results in frequency dependent reflection and transmission coefficients for each interface as well as a frequency dependent group time delay using multiple parallel displacement discontinuities and ignoring converted and reflected waves expressions derived for transmitted wave amplitudes and group velocities show that these depend on frequency angle of incidence and polarization in the case of shear waves measurements on a laminated steel block show that shear pulses propagating parallel to the laminations and polarized parallel and perpendicular to the plane of the laminations both travel at the velocity for solid steel although the spectra of these pulses differ considerably however the energy of the pulse polarized perpendicular to the laminations may propagate as an interface wave between each pair of laminations predictions of the displacement discontinuity model have features quite distinct from many crustal observations to date we suggest that we are able to model dense populations of coplanar cracks that cannot be treated by effective moduli methods which require a dilute concentration of cracks

regional variations in the influence of mesoscale eddies on near surface chlorophyll eddies can influence biogeochemical cycles through a variety of mechanisms including the excitation of vertical velocities and the horizontal advection of nutrients and ecosystems both around the eddy periphery by rotational currents and by the trapping of fluid and subsequent transport by the eddy in this study we present an analysis of the influence of mesoscale ocean eddies on near surface chlorophyll chl estimated from satellite measurements of ocean color the influences of horizontal advection trapping and upwelling downwelling on chl are analyzed in an eddy centric frame of reference by collocating satellite observations to eddy interiors as defined by their sea surface height signatures the influence of mesoscale eddies on chl varies regionally in most boundary current regions cyclonic eddies exhibit positive chl anomalies and anticyclonic eddies contain negative chl anomalies in the interior of the south indian ocean however the opposite occurs the various mechanisms by which eddies can influence phytoplankton communities are summarized and regions where the observed chl response to eddies is consistent with one or more of the mechanisms are discussed this study does not attempt to link the observed regional variability definitively to any particular mechanism but provides a global overview of how eddies influence chl anomalies

variability in the abundance and species composition of diatoms in sinking particles in the northern south china sea results from time series moored sediment traps abstract seasonal variability of diatom abundance and species composition in sinking particles in the northern south china sea was studied using continuous time series sediment trap moorings during a one year period 2009 2010 a clear seasonal pattern of diatom abundance was observed with higher fluxes in winter than in summer this could be related to positive response of diatom growth to increased nutrient supply from the subsurface waters as a result of enhanced vertical mixing in winter mesoscale eddy activities and strong asian dust input could also stimulate the diatom growth and increase the diatom export flux to the deep south china sea the strong asian dust input during spring 2010 probably accelerated the aggregation and downward flux of diatoms in the northern south china sea no distinctive seasonal pattern in diatom species composition was recorded but there was a close correlation of diatom abundances with the cell size and the degree of silification the sinking velocity of the diatom related particles from the sea surface to the deep south china sea has been estimated to be 30 50 m d 1 by comparing the surface chlorophyll a with the diatom abundance and species in sediment traps at 1003 m and 3226 m depths strong dissolution of small sized and low silicified diatom species and lateral advection of particles were also indicated for the deep northern south china sea the present results are crucial as a basis for future understanding of fossil assemblage changes in connection with palaeoclimatic and palaeooceanographic research

tectonometamorphic evolution of the southern quebec appalachians 40ar 39ar evidence for middle ordovician crustal thickening and silurian early devonian exhumation of the internal humber zone published age data from the humber zone of the southern quebec appalachians indicate that deformation and metamorphism occurred during middle to late ordovician time this paper presents the results of a regional scale geochronological study of 70 amphibole and mica single grains by the 40 ar 39 ar laser step heating method which brings forward a more complete middle ordovician early devonian tectonometamorphic evolution of the quebec appalachian humber zone biotites have plateau ages varying between 420 and 411 ma amphiboles are often compositionally rimmed and or contain biotite inclusions their age spectra are generally disturbed but may suggest the occurrence of two distinct events silurian 429 424 ma and middle ordovician 462 460 ma two main groups of muscovite ages have been obtained middle ordovician 469 461 ma and silurian early devonian 431 411 ma but middle to late devonian 387 376 ma ages are also locally present middle ordovician ages are interpreted to record crustal thickening by nappe emplacement during regional taconian metamorphism silurian early devonian ages are attributed to consequences of backthrusting and normal faulting a statistical analysis of silurian early devonian muscovite age spectra reveals an irregular decrease in weighted apparent age maxima across the internal humber zone this age decreasing trend is interpreted to result from the temporal ca 431 411 ma and possibly spatial northwest to southeast progression of deformation recrystallization and fluid circulation during tectonic exhumation of the internal humber zone in southern quebec tectonic models for the northern appalachian internal humber zone should take into account the strong body of evidence for silurian early devonian hinterland directed and extensional deformation as documented in southern quebec

islands as eddy transformation and generation hotspots cabo verde case study abstract deep ocean islands have long been associated with the generation of oceanic eddies in their wakes however their interaction with incoming eddies has seldom been considered this study focuses on the characterization of background and locally generated mesoscale eddies in the cabo verde archipelago between 2003 and 2014 special attention is given to the interaction of incoming eddies with the bathymetry of the islands along with their impacts on the local generation of eddies island induced wind shear effects are also considered in addition some examples of the biological response to background and locally generated eddies are discussed this is achieved by combining remote sensing satellite observations for wind sea surface height and chlorophyll a chla surface concentrations the results show that the interaction between incoming background eddies and the archipelago is a recurrent phenomenon which results in eddy deflection splitting merging intensification and termination sorted by highest to lowest number of occurrences local island induced disturbances are also significant mainly due to atmospheric effects such processes result in the generation of island induced eddies and in wind mediated eddy intensification and confinement more often observed in the leeward group nonetheless it is strongly suggested that many of the locally generated eddies are a direct product or by product of the interaction of background eddies with the islands with respect to the biological realm a locally generated cyclonic eddy is observed to originate a pronounced phytoplankton bloom in the vicinity of the tallest island nonetheless background eddies generated off the african coast are often associated with enhanced chla concentrations when they intersect the archipelago such observations challenge the idea that local biological productivity in deep oceanic islands is exclusively driven by island induced mechanisms

swirling in the ocean immature loggerhead turtles seasonally target old anticyclonic eddies at the fringe of the north atlantic gyre abstract in a highly heterogeneous open ocean swirling oceanographic structures such as eddies drive ocean productivity and aggregate many predators including oceanic sea turtles during early life juvenile loggerhead turtles can spend more than a decade feeding on gelatinous zooplankton in the open ocean but the way they use mesoscale eddies is still poorly understood here we investigated the relationships between 1 the distribution and 2 the diving behaviour of immature loggerhead turtles of the north east atlantic and mesoscale eddies for this purpose 28 turtles were satellite tracked from the azores archipelago using the residence time rt analysis as a proxy to identify high use areas the tracks and dive data of the turtles as well as drifter trajectories were analysed in relation to eddy characteristics which include eddy radius amplitude type cyclonic vs anticyclonic lifetime and region inner core outer core periphery the turtles dispersed widely using many distinct high use areas although there were always more cyclones than anticyclones over the study region the individuals seasonally associated more with the inner cores of old anticyclonic eddies likely due to the higher productivity of decaying anticyclones the comparison between passive drifters and turtles movements showed an active swimming behaviour from the turtles rather than a passive advection through currents three dive types were identified and the one associated with the highest rt was characterized by dives of medium duration and depths in the inner cores of eddies this study is the first to highlight strong affinities of oceanic loggerhead turtles for old anticyclonic eddies around the azores suggesting a greater complexity of these warm core eddies that appear to be much more productive than cyclones

time dependent cracking and brittle creep in crustal rocks a review abstract rock fracture under upper crustal conditions is driven not only by applied stresses but also by time dependent chemically activated subcritical cracking processes these subcritical processes are of great importance for the understanding of the mechanical behaviour of rocks over geological timescales a macroscopic manifestation of time dependency in the brittle field is the observation that rocks can deform and fail at constant applied stresses a phenomenon known as brittle creep here we review the available experimental evidence for brittle creep in crustal rocks and the various models developed to explain the observations laboratory experiments have shown that brittle creep occurs in all major rock types and that creep strain rates are extremely sensitive to the environmental conditions differential stress confining pressure temperature and pore fluid composition even small changes in any of these parameters produce order of magnitude changes in creep strain rates and times to failure three main classes of brittle creep model have been proposed to explain these observations phenomenological statistical and micromechanical statistical and micromechanical models explain qualitatively how the increasing influence of microcrack interactions and or the increasing accumulated damage produces the observed evolution of macroscopic deformation during brittle creep however no current model can predict quantitatively all of the observed features of brittle creep experimental data are limited by the timescale over which experiments are realistically feasible clearly an extension of the range of available laboratory data to lower strain rates and the development of new modelling approaches are needed to further improve our current understanding of time dependent brittle deformation in rocks

time dependent brittle creep in darley dale sandstone 1 the characterization of time dependent brittle rock deformation is fundamental to understanding the long term evolution and dynamics of the earth s crust the chemical influence of pore water promotes time dependent deformation through stress corrosion cracking that allows rocks to deform at stresses far below their short term failure strength here we report results from a study of time dependent brittle creep in water saturated samples of darley dale sandstone initial porosity 13 under triaxial stress conditions results from conventional creep experiments show that axial strain rate is heavily dependent on the applied differential stress a reduction of only 10 in differential stress results in a decrease in strain rate of more than two orders of magnitude however natural sample variability means that multiple experiments must be performed to yield consistent results hence we also demonstrate that the use of stress stepping creep experiments can successfully overcome this issue we have used the stress stepping technique to investigate the influence of confining pressure at effective confining pressures of 10 30 and 50 mpa while maintaining a constant 20 mpa pore fluid pressure our results demonstrate that the stress corrosion process appears to be significantly inhibited at higher effective pressures with the creep strain rate reduced by multiple orders of magnitude the influence of doubling the pore fluid pressure however while maintaining a constant effective confining pressure is shown to influence the rate of stress corrosion within the range expected from sample variability we discuss these results in the context of microstructural analysis acoustic emission hypocenter locations and fits to proposed macroscopic creep laws

u pb and 40ar 39ar geochronology of the baiyunshan gneiss central guangdong south china constraints on the timing of early palaeozoic and mesozoic tectonothermal events in the wuyun wuyi yunkai orogen composite sensitive high resolution ion microprobe shrimp u pb zircon and 40 ar 39 ar step heating biotite hornblende ages are used to provide constraints on the timing and origin of the felsic gneissic rocks in the baiyunshan mountains region and to elucidate their tectonothermal history shrimp dating and cl imaging of zircons give magmatic zircon crystallization ages between late ordovician and early silurian c 453 5 ma 446 ma and 439 ma for three representative felsic gneisses suggesting that most of the baiyunshan gneiss cannot represent basement rocks of the cathaysia block as previously thought including the present age information a synthesis of available age data for regional wuyun wuyi yunkai events reflects the emergence of orogen wide magmatism that could be syn orogenic and have occurred mainly between 460 and 420 ma in the south china block inherited zircons are abundant with ages clustering at late mesoproterozoic 1189 1017 ma and middle mesoproterozoic 772 ma which reveals that the baiyunshan orthogneiss samples a crustal basement containing significant igneous or recycled components related to the rodinia amalgamation and break up a shrimp date of 212 12 ma from a white rim of zircon provides evidence for metamorphic overprinting of an indosinian tectonothermal event on the baiyunshan gneiss incremental heating experiments with six biotite samples and one hornblende sample from a variety of metamorphic rocks yielded two distinct 40 ar 39 ar age groups 150 155 and 94 98 ma the older ages are similar to zircon u pb dates for widespread granitic intrusions in central guangdong we attribute them to late jurassic magmatism induced thermal resetting of the biotite k ar system on the other hand the younger age group is interpreted to record either cooling through the biotite closure temperature of 300 350 c or a second resetting of biotite ar isotopes at c 94 98 ma due to contemporaneous magmatic activity our present age data suggest that the maofengshan orthogneiss was exhumed to 8 to 10 km crustal levels at c 150 ma whereas the eastward components of gneissic rock masses appear to have passed upward through the same crustal depth synchronously or later by c 94 ma exhumation of middle crustal level rocks in the study area since c 155 ma is roughly coeval with exhumation of gneissic rocks from elsewhere in the wuyun orogen suggesting a large scale mechanism for the exhumation pulse related to the yanshanian extensional tectonic regime

diachronous palaeoproterozoic deformation and metamorphism in the committee bay belt rae province nunavut insights from 40ar 39ar cooling ages and thermal modelling regional scale 40ar 39ar data presented in this paper reveal significant across strike and along strike age differences in the committee bay belt cbb rae province nunavut canada that complement variations in observed monazite ages 40ar 39ar hornblende ages are c 1795 1775 and 1750 ma in the western eastern and central parts of the prince albert group pag domain respectively the migmatite domain and walker lake intrusive complex are characterized by c 1750 1730 40ar 39ar hornblende ages without significant along strike variation the 40ar 39ar data provide important constraints on the cooling history and on thermal modelling that elucidates the controls on diachroneity and metamorphic patterns within the belt in the western cbb prograde monazite growth occurred 26 10 myr earlier in the migmatite domain 1864 9 ma peak p t 5 kbar 700 c than in the pag domain 1838 5 ma peak p t 5 kbar 580 c calculations indicate that this earlier monazite growth results from tectonic thickening of higher heat productivity archean lithologies in the migmatite domain which undergoes more rapid prograde heating than the less radiogenetic and lower grade rocks of the pag domain granite generation via biotite dehydration melting at 800 c and 20 km depth is predicted to occur c 1835 ma in agreement with geochronological constraints the tectonic burial of crustal domains with contrasting radiogenic properties also explains the general congruence of lower to upper amphibolite facies metamorphic zones generated during the two main orogenic cycles i e m2 d1 and m3 d2 the modelled timing of prograde monazite growth in the migmatite domain suggests that d2 tectonic thickening began at 1872 9 ma some 8 3 myr before monzazite growth coeval with the inferred time of collision of the meta incognita terrane with the southern rae province along strike diachroneity reflected in 25 myr younger monazite and 40ar 39ar hornblende ages in the eastern relative to the western pag domain cannot be accounted for by heat productivity contrasts along the belt instead the younger deformation and metamorphism in the eastern cbb was driven by its proximity to the eastern promontory of the superior province which collided with the rae province at c 1820 ma the 40ar 39ar data presented here support the interpretation that the youngest monazite in the cbb crystallized at c 1790 ma in the central cbb when this part of the belt was downfolded into a gentle synformal structure while the western part of the belt cooled through 40ar 39ar hornblende closure the results of this study illustrate the important influence of contrasting rock properties on the thermal evolution of orogenic belts and on the temporal record of this evolution

shallow depth caco3 dissolution evidence from excess calcium in the south china sea and its export to the pacific ocean national basic research program of china 973 program 2009cb421201 2009cb421206 national science foundation of china nsfc 40821063 90711005 south china sea institute of oceanology the chinese academy of sciences

the influence of nonlinear mesoscale eddies on near surface oceanic chlorophyll oceanic rossby waves have been widely invoked as a mechanism for large scale variability of chlorophyll chl observed from satellites high resolution satellite altimeter measurements have recently revealed that sea surface height ssh features previously interpreted as linear rossby waves are nonlinear mesoscale coherent structures referred to here as eddies we analyze 10 years of measurements of these ssh fields and concurrent satellite measurements of upper ocean chl to show that these eddies exert a strong influence on the chl field thus requiring reassessment of the mechanism for the observed covariability of ssh and chl on time scales longer than 2 to 3 weeks the dominant mechanism is shown to be eddy induced horizontal advection of chl by the rotational velocities of the eddies

α β phase transition in quartz monitored using acoustic emissions summary it is usually suggested that thermal cracking in a quartz bearing rock results from the anomalously high volumetric expansion coefficients of quartz e g simmons cooper 1978 it has also been recognized that thermal expansion mismatch and mineral anisotropy contribute to thermal cracking in materials that consist of a polycrystalline aggregate composed of several anisotropic minerals even in the absence of a temperature gradient friedrich wong 1986 experiments investigating thermal cracking in rocks commonly involve imaging and quantitative stereology of crack populations induced in rocks treated to various peak temperatures e g friedrich johnson 1978 homand etienne troalan 1984 atkinson mcdonald meredith 1984 meredith atkinson 1985 here we report on acoustic emission experiments that monitor the process of thermal cracking as it occurs during heating supported by measurements of crack surface area pore fluid permeability porosity and surface conductivity carried out on rock samples treated to various peak temperatures the acoustic emission measurements show a strong peak of microcracking at the phase transition temperature for quartz 573 c superimposed upon a background of microcracking due to thermal expansion there is also a clear peak of microcracking at higher temperatures 800 c that can be attributed to oxidation dehydroxylation reactions of hornblende and chlorite measurements of fluid permeability pore surface area porosity and electrical conductivity made on samples that have been heat treated to various maximum temperatures show increases associated with a major episode of cracking in the 500 600 c temperature range indicating that the new cracks form a well interconnected network this has been confirmed by sem and optical microscopy these results have implications for the electrical conductivity of the continental crust providing a mechanism enabling the high pore fluid connectivity needed to explain zones of high electrical conductivity at depth providing that cracks opened in this way remain open at the high pressures existing at depth it should be recognized however that th se measurements are limited in their direct application since they were obtained under initially dry conditions at laboratory pressures

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

observations from a yakutat eddy in the northern gulf of alaska 1 the impingement of deep basin eddies on the shelf in the gulf of alaska has been implicated as an important mechanism for cross shelf exchange the influence of eddies on biological processes has been confirmed with data from the sea viewing wide field of view sensor showing elevated chlorophyll associated with eddies altimetry data suggest that an eddy formed in the winter of 2003 near yakutat alaska and propagated along the shelf break reaching the head of the gulf by spring this eddy was sampled during may and september of 2003 the eddy core water was warm salty and high in nitrate relative to basin water of the same density but was similar to historical water properties from the shelf near yakutat this suggests a shelf origin for the eddy core water

decomposition of vertical velocity for nutrient transport in the upper ocean abstractwithin the pycnocline where diapycnal mixing is suppressed both the vertical movement uplift of isopycnal surfaces and upward motion along sloping isopycnals supply nutrients to the eup

bio optical footprints created by mesoscale eddies in the sargasso sea 1 we investigate the bio optical footprints made by mesoscale eddies in the sargasso sea and the processes that create them through an eddy centric approach many 10 000 eddies are identified and followed in time using satellite altimetry observations and the spatial ocean color patterns surrounding each eddy are assessed we find through a sequence of statistical hypothesis tests that not one but several mechanisms i e eddy pumping eddy advection and eddy ekman pumping are responsible for the spatial temporal ocean color patterns following individual eddies both eddy pumping and the eddy ekman pumping mechanisms alter subsurface nutrient distributions thereby driving biogeochemical cycles while the eddy advection mechanism to first order stirs existing horizontal gradients in bio optical properties this work illustrates both the promise and some of the limitations of satellite observations for assessing the biogeochemical impacts of mesoscale eddies

dynamical characterization of a low oxygen submesoscale coherent vortex in the eastern north atlantic ocean a submesoscale coherent vortex scv with a low oxygen core is characterized from underwater glider and mooring observations from the eastern tropical north atlantic north of the cape verde islands the eddy crossed the mooring with its center and a 1 month time series of the scv s hydrographic and upper 100 m currents structure was obtained about 45 days after and 100 km west the scv frontal zone was surveyed in high temporal and spatial resolution using an underwater glider satellite altimetry showed the scv was formed about 7 months before at the mauritanian coast the scv was located at 80 100 m depth its diameter was 100 km and its maximum swirl velocity 0 4 m s 1 a burger number of 0 2 and a vortex rossby number 0 15 indicate a flat lens in geostrophic balance mooring and glider data show in general comparable dynamical and thermohaline structures the glider in high spatial resolution the mooring in high temporal resolution surface maps of chlorophyll concentration suggest high productivity inside and around the scv the low potential vorticity pv core of the scv is surrounded by filamentary structures sloping down at different angles from the mixed layer base and with typical width of 10 20 km and a vertical extent of 50 100 m

simultaneous ocean surface current and wind vectors retrieval with squinted sar interferometry geophysical inversion and performance assessment abstract simultaneous measurements of ocean surface current and wind vectors at the ocean submesoscale o 1 10 km are needed to improve our understanding of upper ocean mixing air sea interactions ocean biophysical processes and large scale oceanic transports a new satellite mission concept called seastar aims to do just that the concept is a ku band along track interferometric synthetic aperture radar sar system with two squinted beams pointing 45 from broadside and incidence angles around 30 the paper presents an inversion strategy to retrieve simultaneously ocean surface current and wind vectors and reports on the performance obtained with different wind current conditions and instrument configurations results are based on numerical simulations using a bayesian approach and existing geophysical model functions gmfs of the microwave normalized radar cross section nrcs and doppler shift using the baseline two look instrument configuration and realistic instrument noise figures radiometric resolution kp 5 and 12 df 2 and 5 hz the root mean square errors rmse of the retrieved current and wind vectors are typically better than 0 1 m s 10 for current and 0 5 m s 5 for wind this inversion setup yields four ambiguous solutions within a current range of 1 m s the addition of dual polarization vv hh capability helps to discriminate these ambiguities the retrieval performance depends weakly on geophysical parameters such as wind speed current velocity or current direction but is sensitive to wind direction because of its strong effect on current retrieval through the wind wave induced artifact surface velocity wasv larger retrieval errors are obtained when the wind is aligned with one of the antenna line of sight los directions although errors remain typically below 0 2 m s 25 for current and 0 5 m s 15 for wind improving the retrieval performance regardless of wind direction could be achieved either with lower noise figures on 0 or with higher incidence angles or by including an additional third look direction in azimuth e g to achieve a configuration similar to metop ascat scatterometers as per the seastar mission concept submitted to ee10

potential vorticity and vertical velocity at the iceland faerœs front abstract using data from high resolution surveys of the iceland faer s front the authors have calculated synoptic maps of the geostrophic velocity vorticity and potential vorticity on isopycnal surfaces the data have also been used to diagnose the vertical velocity field using the omega equation these results are used to elucidate the dynamical processes occurring at the front across the front there was a large change in potential vorticity on the density surfaces t 27 4 27 6 instability generates meanders that propagate eastward along the front a cyclonic vortex was observed to break off from a meander within the vortex the magnitude of the relative vorticity was large 0 8 f and the potential vorticity had high values similar to that of the water to the north of the front from which the vortex was derived the eddy propagated northeastward relative to the underlying water resulting in large upward downward vertical velocities of the order of 100 m d 1 ahead of behind the vortex

impact of eddies on surface chlorophyll in the south indian ocean a unique feature of the subtropical south indian ocean is the existence of anticyclonic eddies that have higher chlorophyll concentrations than cyclonic eddies off western australia this anomalous behavior is related to the seeding of anticyclonic eddies with shelf water enriched in phytoplankton biomass and nutrients further off shore two mechanisms have been suggested to explain the eddy chlorophyll relationship i eddies originating from the australian coast maintain their chlorophyll anomaly while propagating westward and ii eddy induced ekman upwelling downwelling enhances dampens nutrient supply in anticyclonic cyclonic eddies here we describe the relationship between eddies and surface chlorophyll within the south indian ocean and discuss possible mechanisms to explain the anomalous behavior in light of new analyses performed using satellite chlorophyll data we show that anticyclonic eddies exhibit higher surface chlorophyll concentration than cyclonic eddies across the entire south indian ocean basin from 20 to 28 s particularly in winter using self organizing maps we analyze the chlorophyll patterns within anticyclonic eddies and cyclonic eddies and highlight their complexity our analysis suggests that multiple mechanisms may underlie the observed eddy chlorophyll relationship based on argo float data we postulate the relationship may be partly related to seasonal adjustment of the mixed layer depth within eddies deeper mixing in anticyclonic eddies is expected to enhance nutrient supply to the mixed layer while shallower mixing in cyclonic eddies is expected to reduce it this could explain why the observed winter surface chlorophyll bloom is stronger in anticyclonic eddies than in cyclonic eddies

intense submesoscale upwelling in anticyclonic eddies observations from around the global ocean show that enhanced biological activity can be found in anticyclonic eddies this may mean that upwelling of nutrient rich water occurs within the eddy but such upwelling is not captured by models that resolve mesoscale processes high resolution simulations presented here show intense submesoscale upwelling from the thermocline to the mixed layer in anticyclonic eddies the properties of the upwelling are consistent with a process known as symmetric instability a simple limiting nutrient experiment shows that this upwelling can drive much higher biological activity in anticyclonic eddies when there is a high nutrient concentration in the thermocline an estimate for the magnitude of upwelling associated with symmetric instability in anticyclonic eddies in the sargasso sea shows that it may be of comparable magnitude to other processes though further work is required to understand the full implications for basin scale nutrient budgets

net primary production in the gulf stream sustained by quasi geostrophic vertical exchanges we analyze 12 years of mesoscale vertical motion derived from an observation based product in the top 1000 m of the north west atlantic ocean vertical velocities o 10 m d 1 associated with gulf stream instabilities consist of alternating cells of upwelling and downwelling here we show that the magnitude of the vertical motions decays exponentially southward with an e folding length scale that is informative on the dynamics of the system we further investigate the impact of the vertical supply of nutrients about phytoplankton growth with a conceptual model incorporating the mean effect of nutrient distribution quasi geostrophic dynamics and ekman suction pumping results confirm that the mean effect of mesoscale vertical velocity variability alone can sustain observed levels of net primary production in the immediate vicinity of the gulf stream while other mechanisms including horizontal advection and submesoscale dynamics need to be considered when moving toward the subtropical gyre

satellite observations of mesoscale eddy induced ekman pumping abstractthree mechanisms for self induced ekman pumping in the interiors of mesoscale ocean eddies are investigated the first arises from the surface stress that occurs because of differences between surface wind and ocean velocities resulting in ekman upwelling and downwelling in the cores of anticyclones and cyclones respectively the second mechanism arises from the interaction of the surface stress with the surface current vorticity gradient resulting in dipoles of ekman upwelling and downwelling the third mechanism arises from eddy induced spatial variability of sea surface temperature sst which generates a curl of the stress and therefore ekman pumping in regions of crosswind sst gradients the spatial structures and relative magnitudes of the three contributions to eddy induced ekman pumping are investigated by collocating satellite based measurements of sst geostrophic velocity and surface winds to the interiors of eddies identified from their sea surface height signatures on average e

three long lived anticyclonic eddies in the northern south china sea 1 in august 2007 three long lived anticyclonic eddies ace1 ace2 and ace3 were detected by both satellite sea level anomaly sla map and in situ measurements in the northern south china sea scs ace3 had a two core ace3 1 and ace3 2 structure in situ stations along 18 degrees n almost cut through the centers of ace2 and ace3 2 near the centers of ace2 and ace3 2 mean temperature and sound velocity are similar to 0 65 degrees c and similar to 2 m s 1 larger than those in their surrounding areas respectively while mean salinity and density are similar to 0 02 psu and similar to 0 15 m 3 s 1 smaller than those in their surrounding areas due to downwelling near the eddy cores the depths of maximum and minimum salinity near the eddy cores are similar to 65 m and similar to 35 m larger than those in their surrounding areas the vertical depth with current speed larger than 0 05 m s 1 can reach similar to 900 m their detailed evolutionary processes were depicted based on the variation of geostrophic currents and the trajectories of five drifting buoys ace1 lasted 147 days while ace2 and ace3 lasted 168 days and 210 days respectively ace1 had a smaller mean sla 18 8 cm in its lifetime than ace2 21 8 cm and ace3 25 3 cm but had a larger negative mean vorticity 7 7 x 10 6 s 1 than ace2 7 0 x 10 6 s 1 and ace3 7 0 x 10 6 s 1 one short lived anticyclonic eddy that split from ace2 and another one that merged with ace3 both had a smaller sla negative vorticity and diameter than ace2 and ace3 respectively

high temperature memory in calcic amphiboles and constraints on compositional control of their 40ar 39ar ages well characterized calcic amphiboles from an incompletely mixed magmatic rock association of mainly intermediate dioritic composition were studied by incremental heating experiments of 40 ar 39 ar the rocks in question were thermally overprinted by late hercynian granites microprobe and scanning electron microscopy analyses show that the amphibole grains consist of two different calcic hornblende varieties 1 a si and mg rich variety and 2 a variety enriched in al ti fe k and na the mg si rich hornblende can be further characterized by its higher cao k 2 o ratios 30 50 compared to the al ti fe k na rich hornblende 12 15 three hornblende separates that previously had yielded conventional k ar ages of 320 317 and 302 ma have been dated by the 40 ar 39 ar step heating technique the low and medium temperature parts of the 40 ar 39 ar age spectrum show discordant ar systematics with single step ages generally younger than 325 ma the gas released at the highest temperature steps preserves an exceptional record of old and remarkably similar integrated ages 342 346 and 344 ma the high temperature ages correspond to phases with higher apparent cao k 2 o ratios 30 45 and are interpreted to result from ar release from mg si hornblende domains that are assumed to have been very resistent to ar loss during the late hercynian thermal events the results of this study suggest that ar retentivity differs among calcic amphiboles and mg si rich hornblendes are more ar retentive than their al ti fe k na rich counterparts

late variscan magmatism revisited new implications from pb evaporation zircon ages on the emplacement of redwitzites and granites in ne bavaria pb evaporation zircon analyses coupled with a detailed cathodoluminescence cl study on the complete series of granitoids from the northern oberpfalz ne bavaria provide new evidence for the commencement and timing of late variscan magmatism all granitoids analysed in this study were dated before by rb sr and or k ar methods investigated samples comprise medium grained i type dioritic rocks redwitzites i s type granites leuchtenberg marktredwitz g1 zainhammer and s type granites falkenberg liebenstein mitterteich friedenfels steinwald flossenburg barnau the zircon evaporation technique reveals three groups of 207pb 206pb ages which are interpreted to represent magmatic crystallisation 1 ages of 324 321 ma are found in all analysed redwitzites and in almost all i s type granites 2 the granites of falkenberg and liebenstein yield ages of 315 ma 3 ages between 312 and 310 ma are recorded in the mitterteich friedenfels steinwald and flossenburg granites titanite crystals from different redwitzite bodies yield conventional u pb ages of 325 322 ma identical to the pb evaporation zircon data of these rocks the s type granites of groups 2 and 3 contain zircons with relict cores but only a small number of them yield older ages indicating that some of the cores must have lost their radiogenic pb from the geochronological data we infer that metamorphic conditions of the variscan crust produced different granite types at different times the data support a model involving an early period of mantle related magmatism which postdates the final convergence stage of the variscan orogen this magmatic activity was at the same time as the thermal peak of regional metamorphism and is followed by a late period of crustal anatexis which is probably related to post collisional extension of the thickened variscan crust

the influence of a mature cyclonic eddy on particle export in the lee of hawaii abstract mesoscale eddies may enhance primary production pp in the open ocean by bringing nutrient rich deep waters into the euphotic zone potentially leading to increased transport of particles to depth this hypothesis remains controversial however due to a paucity of direct particle export measurements in this study we investigated particle dynamics using 234 th 238 u disequilibria within a mesoscale cold core eddy cyclone opal which formed in the lee of the hawaiian islands 234 th samples were collected along two transects across cyclone opal as well as during a time series within the eddy core during a decaying diatom bloom particulate carbon pc particulate nitrogen pn and biogenic silica bsio 2 fluxes at 150 m varied spatially and temporally within the eddy and strongly depended on the 234 th model formulation used e g steady state versus non steady state inclusion of upwelling etc particle fluxes estimated from a steady state model assuming an upwelling rate of 2 m day 1 yielded the best fit to sediment trap data these 234 th derived particle fluxes ranged from 332 14 to 1719 53 mol c m 2 day 1 27 3 to 114 12 mol n m 2 day 1 and 33 20 to 309 73 mol si m 2 day 1 although pp rates within cyclone opal were elevated by a factor of 2 3 pc and pn fluxes were the same within error inside and outside of cyclone opal the ratio of pc export to pp remained surprisingly low at 2 fluxes within the eddy core were three times higher detailed analyses of 234 th depth profiles consistently showed excess 234 th at 100 175 m associated with the remineralization and possible accumulation of suspended and dissolved organic matter from the surface we suggest that strong microzooplankton grazing facilitated particulate organic matter recycling and resulted in the export of empty diatom frustules thus while eddies may increase pp they do not necessarily increase pc and pn export to deep waters this may be a general characteristic of wind driven cyclonic eddies of the north pacific subtropical gyre and suggests that eddies may preferentially act as a silica pump thereby playing an important role in promoting silicic acid limitation in the region

large scale alignment of oceanic nitrate and density 1 by analyzing global data we find that over large scales surfaces of constant nitrate are often better aligned with isopycnals than with isobars particularly below the euphotic zone this is unexplained by the movement of isopycnal surfaces in response to eddies and internal waves and is perhaps surprising given that the biological processes that alter nitrate distributions are largely depth dependent we provide a theoretical framework for understanding the orientation of isonitrate surfaces in relation to isopycnals in our model the nitrate distribution results from the balance between depth dependent biological processes nitrate uptake and remineralization and the along isopycnal homogenization of properties by eddy fluxes parameterized by eddy diffusivity where the along isopycnal eddy diffusivity is relatively large nitrate surfaces are better aligned with isopycnals than isobars we test our theory by estimating the strength of the eddy diffusivity and biological export production from global satellite data sets and comparing their contributions indeed we find that below the euphotic zone the mean isonitrate surfaces are oriented along isopycnals where the isopycnal eddy diffusivity is large and deviate where the biological export of organic matter is relatively strong comparison of nitrate data from profiling floats in different regions corroborates the hypothesis by showing variations in the nitrate density relationship from one part of the ocean to another

submesoscale impacts on horizontal and vertical transport in the gulf of mexico 1 impacts of submesoscale processes on transport are investigated numerically in an energetic mesoscale flow with an ocean model run at two horizontal resolutions 1 and 5 km the focus is the northwestern gulf of mexico where the loop current eddies are surrounded by smaller vortices by increasing the horizontal resolution the number and strength of submesoscale eddies and vorticity filaments within the mixed layer increase dramatically and with them the vertical velocities inside the coherent eddies and at their peripheries increased vertical velocities for increasing resolution are associated to near inertial motions and they are not limited to the mixed layer but are found at all depths horizontal velocities on the contrary are similar lagrangian isobaric tracers are deployed close to the surface and at 100 m and three dimensional neutrally buoyant particles are released close to the surface at the base of the mixed layer and at 100 m the modeled horizontal dispersion curves for each deployment depth are independent of the kind of particles and of horizontal resolution close to the ocean surface however convergence zones generated by submesoscale ageostrophic motions and resolved at 1 km resolution influence the details of the tracer distributions vertical dispersion increases by several folds for increasing resolution at all depths explored with the largest differences found close to the surface therefore submesoscales processes play a fundamental role in driving vertical transport in eddy dominated flows both within and below the mixed layer for times comparable to the eulerian time scale

synchrotron tomographic quantification of strain and fracture during simulated thermal maturation of an organic rich shale uk kimmeridge clay analyzing the development of fracture networks in shale is important to understand both hydrocarbon migration pathways within and from source rocks and the effectiveness of hydraulic stimulation upon shale reservoirs here we use time resolved synchrotron x ray tomography to quantify in four dimensions 3 d plus time the development of fractures during the accelerated maturation of an organic rich mudstone the uk kimmeridge clay with the aim of determining the nature and timing of crack initiation electron microscopy em both scanning backscattered and energy dispersive was used to correlatively characterize the microstructure of the sample preheating and postheating the tomographic data were analyzed by using digital volume correlation dvc to measure the three dimensional displacements between subsequent time heating steps allowing the strain fields surrounding each crack to be calculated enabling crack opening modes to be determined quantification of the strain eigenvectors just before crack propagation suggests that the main mode driving crack initiation is the opening displacement perpendicular to the bedding mode i further detailed investigation of the dvc measured strain evolution revealed the complex interaction of the laminar clay matrix and the maximum principal strain on incipient crack nucleation full field dvc also allowed accurate calculation of the coefficients of thermal expansion 8 10 5 c perpendicular and 6 2 10 5 c parallel to the bedding plane these results demonstrate how correlative imaging using synchrotron tomography dvc and em can be used to elucidate the influence of shale microstructure on its anisotropic mechanical behavior

ageostrophic secondary circulation in a subtropical intrathermocline eddy abstractvertical motions play a key role in the enhancement of primary production within mesoscale eddies through the introduction of nutrients into the euphotic layer however the details of the vertical velocity field w driving these enhancements remain under discussion for the first time the mesoscale w associated with an intrathermocline eddy is computed and analyzed using in situ high resolution three dimensional 3d fields of density and horizontal velocity by resolving a generalized omega equation valid for high rossby numbers in the seasonal pycnocline the diagnosed w reveals a multipolar structure with upwelling and downwelling cells located at the eddy periphery in the main pycnocline w is characterized by a dipolar structure with downwelling velocities upstream of the propagation path and upwelling velocities downstream maximum values of w reach 6 4 m day 1 an observed enhancement of chlorophyll a at the eddy periphery coincides with the location of the upwelling and downwelling cells a

fracture toughness and subcritical crack growth during high temperature tensile deformation of westerly granite and black gabbro abstract the double torsion testing method has been used to determine catastrophic and subcritical crack propagation parameters for pre cracked specimens of westerly granite and black gabbro under a number of environmental conditions the critical stress intensity factor for catastrophic crack propagation fracture toughness of granite and gabbro has been measured at temperatures from 20 to 400 c in a vacuum at 20 c the fracture toughness of westerly granite was 1 79 0 02 mpa m 1 2 and for two blocks of black gabbro it was 3 03 0 08 mpa m 1 2 and 2 71 0 15 mpa m 1 2 respectively these values are very close to those reported by other investigators for tests conducted in air of ambient humidity at room temperature for both rocks fracture toughness at first increased slightly and then decreased steadily on raising the temperature above ambient conditions this behaviour is explained in terms of the density and distribution of thermally induced microcracks as determined by quantitative optical microscopy subcritical crack growth behaviour has been studied at temperatures up to 300 c and under water vapour at pressures of 0 6 to 15 kpa both the load relaxation and incremental constant displacement rate forms of the double torsion testing method were utilised to generate stress intensity factor crack velocity diagrams crack growth was measured over the velocity range 5 10 3 to 10 7 m s 1 increasing both temperature and water vapour pressure resulted in substantially higher crack growth rates the overall effect of raising the temperature over the range studied here 20 300 c was to increase the crack growth rate in granite and gabbro by 5 and 7 orders of magnitude respectively at constant stress intensity factor and vapour pressure of water for both rocks the slopes of stress intensity factor crack velocity curves were sensitive to changes in both temperature and water vapour pressure at low values of the latter parameter slopes fell substantially on raising the water vapour pressure but were relatively insensitive to changes in temperature at these higher pressures no subcritical crack growth limit was encountered estimates of the uncertainty in our experimental data are given from the results of multiple load relaxation experiments on westerly granite specimens we estimate the uncertainty in position of stress intensity factor crack velocity curves along the stress intensity axis to be c 10 of the fracture toughness and the uncertainty in slope of such curves to be c 12 problems associated with the extrapolation of our experimental data to regions of higher effective confining pressure in the earth s crust are discussed

enhanced primary production in the oligotrophic south china sea by eddy injection in spring concentration typically at 0 05 0 08 mgm 3 it is intriguing to explore this unusual happening based on six different remote sensing data and numerical modelling the results suggest that the injection of an ocean eddy is the most likely cause of the bloom due to long range transport of a large 700 500 km anti cyclonic ocean eddy coastal nutrients and plankton could be brought across hundreds of kilometres to the centre of northern scs and impact the biogeochemistry the open ocean part of the northern scs basin has long been considered generally free from coastal influences this work provides new evidence that proves otherwise moreover from the perspective of physical oceanography it is interesting to observe that outside the monsoon seasons there can be well defined anti cyclonic ocean circulation existing in the scs without the prevailing monsoonal wind citation lin i i c c lien c r wu g t f wong c w huang and t l chiang 2010 enhanced primary production in the oligotrophic south china sea by eddy injection in spring geophys res lett 37 l16602 doi 10 1029 2010gl043872

dynamics and production of dissolved organic carbon in a large continental shelf system under the influence of both river plume and coastal upwelling we examined the dynamics and production of dissolved organic carbon doc on a large continental shelf in the northern south china sea which is largely shaped by a river plume and coastal upwelling based on a cruise in summer 2008 the plume water extended from the mouth of the pearl river estuary to the middle shelf and was characterized by high doc concentrations while the upwelled water occupying the nearshore area featured low doc concentrations biological production of doc was observed in both the river plume and the coastal upwelling zones with different behavior between regions the system appeared to be autotrophic in terms of doc throughout the plume while in the upwelling circulation the metabolism of doc was mixed trophic nevertheless the integrated net doc production rate of 11 5 6 9 mmol c m 2 d 1 in the upwelling zone was comparable to that in the plume 7 1 7 0 mmol c m 2 d 1 the net doc production correlated strongly with net consumption of dissolved inorganic carbon dic and inorganic nutrients suggesting that the net doc production was highly coupled to net community production ncp in both the plume and upwelling zones both regimes had similar doc ncp partitioning with 19 27 of ncp in the plume and 24 26 of ncp in the upwelling zones converted to doc a positive correlation was also found between particulate organic carbon poc and net dic consumption with higher poc production in the upwelling zones where large phytoplankton prevailed most ncp removal occurred through poc sinking and or the diffusion and horizontal transport of doc

the metamorphic complex of beloretzk sw urals russia â a terrane with a polyphase meso to neoproterozoic thermo dynamic evolution abstract an integrated geological study of the tectono metamorphic evolution of the metamorphic complex of beloretzk mcb which is part of the eastern bashkirian mega anticlinorium bma sw urals russia shows that the main lithological units are neoproterozoic riphean and vendian age siliciclastic to carbonate successions granitic syenitic and mafic intrusions together with subaerial equivalents comprise the neo and mesoproterozoic magmatic rocks the metamorphic grade ranges from diagenetic and very low grade in the western bma to high grade in the mcb the n s trending zuratkul fault marks the change in metamorphic grade and structural evolution between the central and eastern bma structural data pb pb single zircon ages 40 ar 39 ar cooling ages and the provenance signature of riphean and vendian siliciclastic rocks in the western bma give evidence of mesoproterozoic grenvillian rifting deformation and eclogite facies metamorphism in the mcb and a neoproterozoic cadomian orogenic event in the sw urals three pre ordovician deformation phases can be identified in the mcb the first sse vergent isoclinal folding phase d 1 is younger than the intrusion of mafic dykes pb pb single zircon 1350 ma and older than the eclogite facies metamorphism high p low t eclogite facies metamorphism is bracketed by d 1 and the intrusion of the achmerovo granite pb pb single zircon 970 ma an extensional sinistral top down to nw directed shearing d 2 is correlated with the first exhumation of the mcb e vergent folding and thrusting d 3 occurred at retrograde greenschist facies metamorphic conditions the tremolite 40 ar 39 ar cooling age 718 5 ma of amphibolitic eclogite and muscovite 40 ar 39 ar cooling ages about 550 ma of mica schists indicate that a maximum temperature of 500 50 c was not reached during the neoproterozoic orogeny the style and timing of the neoproterozoic orogeny show similarities to the cadomian aged timan range nw of the polar urals geochronological and thermochronological data together with the abrupt change in structural style and metamorphism east of the zuratkul fault suggest that the mcb is exotic with respect to the se margin of the east european platform thus the mcb is named the beloretzk terrane recognition of the beloretzk terrane and the neoproterozoic orogeny at the eastern margin of baltica has important implications for neoproterozoic plate reconstruction and suggests that the eastern margin of baltica might have lain close to the avalonian cadomian belt

patterns of vertical velocity induced by eddy distortion in an ocean model vertical motions within eddies play an important role in the exchange of properties and energy between the upper ocean and the ocean interior here we analyze alternating upward and downward cells in anticyclonic eddies in the east australian current region using a global eddy resolving model the cells explain over 50 of the variance of vertical velocity within these eddies we show that the upward and downward cells relate to eddy distortion defined as the change in eddy shape over time in anticyclonic eddies in the southern hemisphere an inward distortion is associated with upward motion and an outward distortion is associated with downward motion we discuss two mechanisms that link eddy distortion to vertical velocity one mechanism relates to changes in stratification and relative vorticity in the eddy interior the other mechanism relates to divergence of the horizontal flow in different quadrants of the eddy we show that mesoscale changes in sea level anomaly can be used to infer the vertical motion within eddies

nutrients and plankton spatial distributions induced by a coastal eddy in the gulf of lion insights from a numerical model a plankton functional types model forced by a hydrodynamic model is used in the present work to study the impacts of a coastal eddy on the distribution of nutrients and plankton in the western part of gulf of lion nw mediterranean sea this study based on a realistic simulation of the year 2001 focuses on a long life anticyclonic eddy detected during summer the studied anticyclonic eddy has some biogeochemical characteristics of those observed in the open ocean as for example the low productivity at their core and rising up of nutricline on their edges however the functioning and consequences of such coastal eddy on nutrients and plankton distributions are complicated by potential interactions with topography wind induced upwelling along the languedoc coast and nearby northern current nc especially the proximity of the southern edge of the eddy with the nc makes possible the exchanges of organic matter plankton at times during the eddy s life the coastal eddy thus transports organic matter from the coastal zone to the offshore domain the coupled model also suggests the importance of offshore to coastal transport by nc through a seeding process of the eddy in plankton at the beginning of its life a detailed biogeochemical functioning of the studied eddy all along its lifetime is proposed from the model results at the beginning the eddy mainly acts as a transporter of the plankton wind induced bloom occurring along the languedoc coast several days before the eddy set up at the same time the eddy shows upwards vertical velocities on its edges creating upwelling of nutrient enriched waters the process of eddy induced upwelling is notably enhanced on the eddy western side along the roussillon coast due to the shelf topography the around eddy advection and relative lower temperatures prevent the large development of phytoplankton along the roussillon coast and the eddy induced bloom is predicted to occur near the northwestern side of the eddy the eddy induced and wind induced blooms of phytoplankton then merge on the eastern side by advection and this process of aggregation may explain the persistent occurrence of a filament of high chlorophyll observed on the offshore edge of the eddy throughout the study period the changes in plankton composition due to a combination of top down and bottom up processes during the coast to offshore transport may explain the disappearance of the filament south of 43 n at the surface

eddy kinetic energy of the north atlantic subpolar gyre from satellite altimetry the surface eddy kinetic energy field of the north atlantic subpolar gyre 40 65 n 5 60 w is studied using the altimetric satellites geosat 1987 1988 and ers 1 1992 1993 this is on the whole an area of low eddy activity previous studies of the north atlantic have usually concentrated on the highly variable gulf stream system we review what is known of the surface circulation of the region we confirm that there is a close relationship between the eddy kinetic energy and the mean currents and that it is strongly constrained by the topography the eddy field occurs in deep water and follows the contours particularly around the flemish cap high eddy kinetic energy is seen on the flanks of topography and is higher where the slope is steeper this is particularly clear on both east and west flanks of the rockall plateau interannual changes in the currents are revealed by the differences between the geosat and ers 1 eddy kinetic energy maps in some years 1988 and 1992 1993 the northern core of the north atlantic current nac usually assumed to be tied to the charlie gibbs fracture zone 52 n is considerably weaker and may not exist at all while in 1987 there is a distinct core here in 1988 and 1992 1993 the main eddy region shifts farther to the south to about 49 n in 1988 and 50 n in 1992 1993 in 1987 there is also a current core even farther south centered at about 47 n implying that in that year the nac is arranged into two distinct branches

horizontal dispersion within an anticyclonic mesoscale eddy abstract ship mounted adcp and buoy data are used to fit an azimuthal velocity profile to a n e atlantic mesoscale eddy chosen as a site for a lagrangian biogeochemical survey the cruise forming part of the uk plankton reactivity in the marine environment prime initiative together with the buoy derived locus of the eddy centre the adcp derived velocity field allows observations of a sulphur hexafluoride sf6 tracer release within the eddy to be put into a non translating non rotating frame analysis of the transformed data suggests that the patch of tracer though spreading remained coherent throughout the nine day survey a linear regression on the square of the radial patch width versus time gives an estimate for the effective horizontal diffusion coefficient of 22 10 m 2 s 1 this is consistent with previous estimates of diffusion rates at the o 10 km lengthscale of the patch theory predicts a corresponding along streamline spreading time of 14 days this implies that the tracer patch mixed little with the surrounding waters during the first five days of the survey suggesting that biogeochemical processes were little affected by lateral mixing during this period the theory is inapplicable at later times because the area was struck by a storm at the start of the sixth day which resulted in the halving of sf6 concentrations using a model of a circular eddy with the calculated velocity profile the dispersion of the initial patch of tracer is simulated for different diffusivities the results confirming the estimate of along streamline mixing time and demonstrating the enhancement of azimuthal diffusion by the radial shear of the flow

thermohaline staircases in a caribbean eddy and mechanisms for staircase formation the structure of a cyclonic eddy in the eastern caribbean was observed by caribbean vorticity experiment cruise cavortex i in august 2003 prominent thermohaline staircases are evident in profiles of temperature and salinity at locations that appear to correlate with the presence of lateral property gradients and shear within the eddy although such a connection is less than definitive due to the coarseness of horizontal sampling these observations are examined in light of predictions from two theories for staircase formation aspects of the data are found to be consistent with each raising the possibility that both mechanisms are operating

formation of intrathermocline lenses by eddy wind interaction abstractmesoscale intrathermocline lenses are observed throughout the world ocean and are commonly attributed to water mass anomalies advected from a distant origin an alternative mechanism of local generation is offered herein in which eddy wind interaction can create lens shaped disturbances in the thermocline numerical simulations illustrate how eddy wind driven upwelling in anticyclones can yield a convex lens reminiscent of a mode water eddy whereas eddy wind driven downwelling in cyclones produces a concave lens that thins the mode water layer a cyclonic thinny such transformations should be observable with long term time series in the interiors of mesoscale eddies

vorticity and vertical circulation at an ocean front abstract density and velocity data with 4 km horizontal resolution from a survey of a front during fasinex frontal air sea interaction experiment are combined to describe the structure of the top 300 m of the ocean the geostrophic velocity field is derived and is used to examine the relative importance of stratification relative vorticity and twisting terms in ertel s potential vorticity q tenfold isopycnic changes in q are found across a horizontal scale of only 10 km these changes are confined to isopycnals that outcrop from the seasonal thermocline into the mixed layer the ageostrophic velocity field is quantified by solution of the omega equation and vertical velocities of up to 40 m day 1 are found small 40 km surface trapped top 200 m eddies are found to play a crucial role in the transport and effective diffusion of properties across the thermocline out of the mixed layer

holocene landslides and a 3500 year record of pacific northwest earthquakes from sediments in lake washington lake washington which forms the eastern boundary of seattle is located in a tectonically active area containing several strands of the seattle fault high resolution seismic reflection profiling sidescan swath imagery and sediment coring were used to define deformation of holocene lake sediments and the distribution geometry age and causes of submarine landslides numerous large block slides sediment slumps and debris flows are present throughout the lake and large landslides obscure the surficial structure of seattle fault strands as they pass through the lake in addition most bays along the lake margin are the headwalls of large submarine slides submerged forests show evidence of deep seated block failures that have exposed glacial sediments and tertiary rocks the massive submarine block slides and retrogressive submarine slope failures were triggered most likely by large m b 7 earthquakes on the seattle fault and or large to great m b 8 temblors occurring elsewhere in cascadia buried landslides suggest that submarine slope failures and mass wasting occurred more than once in the last 11 000 yr sediments in lake washington preserve a record of episodic deposition of turbidites possibly caused by seismically induced submarine landslides magnetic susceptibility profiles on 36 gravity cores show a characteristic series of magnetic peaks that can be traced throughout the lake x radiography and grain size analyses suggest that the magnetic peaks represent anomalous detrital layers that in some cases are turbidites the areal extent and magnetic signatures of many of the deposits suggest multiple sources which is consistent with numerous local landslides caused by large earthquakes radiocarbon dating and correlation of the downcore magnetic profiles establish a sediment record in which episodic sedimentary disturbances occurred seven times in the last 3500 yr if these deposits are seismically induced turbidites seismites then large earthquakes have occurred about every 300 500 yr in the puget sound region

an index to distinguish surface and subsurface intensified vortices from surface observations in this study the authors first show that it is difficult to reconstruct the vertical structure of vortices using only surface observations in particular they show that the recent surface quasigeostrophy sqg and interior and surface quasigeostrophy isqg methods systematically lead to surface intensified vortices and those subsurface intensified vortices are thus not correctly modeled the authors then investigate the possibility of distinguishing between surface and subsurface intensified eddies from surface data only using the sea surface height and the sea surface temperature available from satellite observations a simple index based on the ratio of the sea surface temperature anomaly and the sea level anomaly is proposed while the index is expected to give perfect results for isolated vortices the authors show that in a complex environment errors can be expected in particular when strong currents exist in the vicinity of the vortex the validity of the index is then analyzed using results from a realistic regional circulation model of the peru chile upwelling system where both surface and subsurface eddies coexist the authors find that errors are mostly associated with double core eddies aligned surface and subsurface cores and that the index can be useful to determine the nature of mesoscale eddies surface or subsurface intensified from surface satellite observations however the errors reach 24 and some possible improvements of the index calculations are discussed

long range transport of a quasi isolated chlorophyll patch by an agulhas ring 1 using satellite retrievals of sea surface chlorophyll and geostrophic currents we study the evolution of a distinct chlorophyll patch transported by an agulhas ring along a 1 500 km track throughout an 11 months period of the total 2 years eddy lifetime the shape of the chlorophyll patch is consistently delimited by the horizontal transport barriers associated with the eddy analysis of lagrangian time series of sea surface variables in and around the eddy suggests that the evolution of the chlorophyll patch is driven by two processes i slow lateral mixing with ambient waters mediated by horizontal stirring in filaments and ii rapid events of wind induced vertical mixing these results support the idea that mesoscale eddies shape biological production through the combination of horizontal and vertical dynamical processes and emphasize the important role of horizontal eddy transport in sustaining biological production over the otherwise nutrient depleted subtropical gyres

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

oceanic stratified euphotic zone as elucidated by 234th 238u disequilibria1 profiles of dissolved and particulate 234th were determined at the vertex 2 and 3 stations off manzanillo mexico and at the vertex 4 station about 900 km north of hawaii by modeling the disequilibria between 234th and 238u in the dissolved and particulate form estimates of scavenging rates for th from the dissolved to particulate phases particle residence times and the flux of th via particle removal can be obtained 234th 238u activity ratio profiles indicate that the euphotic zone can be separated into two layers an upper oligotrophic layer characterized by low new production values low net scavenging and long dissolved 234th residence times and a subsurface eutrophic layer with higher new production values more intense scavenging and shorter dissolved 234th residence times new production rather than total primary production may determine net scavenging rates of reactive elements from oceanic surface waters these results contribute to the emerging descriptions of the layered structure of oligotrophic euphotic zones and support the notion that this may be a general and ubiquitous feature of global stratified oligotrophic regimes these layered systems can be structured not only in biological and nutrient parameters but also in terms of the rates of chemical scavenging and elemental transport the layered structure of biological processes within stratified oceanic euphotic zones has been recognized for quite some time since steele and yentsch s 1960 paper on the vertical distribution of chlorophyll the subsurface chlorophyll maximum has received a great deal of attention and is now a well known oceanographic feature dugdale 1967 proposed a two layer model for oceanic euphotic zones in which nutrient limited phytoplankton populations overlie light limited populations venrick 1982 reported two distinct floral assemblages associated with each of these layers which also seem to be differentiated ecologically in terms of competition and predation herbland et al 1985 showed a strong stratification in size classes of photosynthetic organisms especially 1 pm of the equatorial atlantic with the major shift in size spectra occurring at or near the base of the mixed layer recently the presence of stratified systems in meso and oligotrophic regimes has been further interpreted in terms of the concepts of dugdale and goering 1967 and eppley and peterson 1979 regarding new and regenerated pro

fracture toughness anisotropy in shale the use of hydraulic fracturing to recover shale gas has focused attention on the fundamental fracture properties of gas bearing shales but there remains a paucity of available experimental data on their mechanical and physical properties such shales are strongly anisotropic so that their fracture propagation trajectories depend on the interaction between their anisotropic mechanical properties and the anisotropic in situ stress field in the shallow crust here we report fracture toughness measurements on mancos shale determined in all three principal fracture orientations divider short transverse and arrester using a modified short rod methodology experimental results for a range of other sedimentary and carbonate rocks are also reported for comparison purposes significant anisotropy is observed in shale fracture toughness measurements at ambient conditions with values as high as 0 72mpam1 2 where the crack plane is normal to the bedding and values as low as 0 21mpam1 2 where the crack plane is parallel to the bedding for cracks propagating non parallel to bedding we observe a tendency for deviation towards the bedding parallel orientation applying a maximum energy release rate criterion we determined the conditions under which such deviations are more or less likely to occur under more generalized mixed mode loading conditions we find for mancos shale that the fracture should deviate towards the plane with lowest toughness regardless of the loading conditions

ocean nutrient pathways associated with the passage of a storm storms that affect ocean surface layer dynamics and primary production are a frequent occurrence in the open north atlantic ocean in this study we use an interdisciplinary dataset collected in the region to quantify nutrient supply by two pathways associated with a storm event entrainment of nutrients during a period of high wind forcing and subsequent shear spiking at the pycnocline due to interactions of storm generated inertial currents with wind the post storm increase in surface layer nitrate by 20 mmol m 2 was predominantly driven by the first pathway nutrient intrusion during the storm alignment of post storm inertial currents and surface wind stress caused shear instabilities at the ocean pycnocline forming the second pathway for nutrient transport into the euphotic zone during the alignment period pulses of high turbulent nitrate flux through the pycnocline up to 1 mmol m 2 day 1 approximately 25 times higher than the background flux were detected however the impact of the post storm supply was an order of magnitude lower than during the storm due to the short duration of the pulses cumulatively the storm passage was equivalent to 2 5 5 of the nitrate supplied by winter convection and had a significant effect compared to previously reported sub mesoscale dynamics in the region as storms occur frequently they can form an important component in local nutrient budgets

the wineglass effect shapes particle export to the deep ocean in mesoscale eddies mesoscale eddies in the ocean strongly impact the distribution of planktonic particles mediating carbon fluxes over 1 3 of the world ocean however mechanisms controlling particle transport through eddies are complex and challenging to measure in situ here we show the subsurface distribution of eddy particles funneled into a wineglass shape down to 1000 m leading to a sevenfold increase of vertical carbon flux in the eddy center versus the eddy flanks the wineglass effect we show that the slope of the wineglass r is the ratio of particle sinking velocity to the radially inward velocity such that r represents a tool to predict radial particle movement here 0 05ms 1 a simple model of eddy spindown predicts such an ageostrophic flow concentrating particles in the eddy center we explore how size specific particle flux toward the eddy center impacts eddies biogeochemistry and export fluxes

mechanisms for vertical nutrient transport within a north atlantic mesoscale eddy abstract prompted by observational evidence for an enhanced source of surface nutrients within an anticyclonic eddy in the ne atlantic we investigate vertical transport processes that may produce such a phenomenon for the eddy investigated the dominant mechanism is found to be ageostrophic circulation resulting from a perturbation of the circular flow of the eddy this can produce upwelling velocities of order 10 m d 1 ekman pumping due to wind stress on the eddy also produces upwelling within but on a smaller scale of 0 5 m d 1 there is no evidence that self propagation of the eddy leads to an enhanced nutrient flux by displacement upwards of nutrient laden deeper isopycnals over the core of the eddy deeper winter mixing within the eddy relative to the surroundings however may contribute to the elevated nutrient levels

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

penetration of nonlinear rossby eddies into south china sea evidenced by cruise data national basic research program of china 2009cb421208 2007cb411803 natural science foundation of china 40976013 41121091 united states of america national oceanic atmospheric administration national environmental satellite data and information service ocean remote sensing 3000 11 03241

transient upwelling hot spots in the oligotrophic north pacific 1 vertical exchange between deep nutrient rich and nutrient depleted surface waters controls the physical supply of nutrients into the euphotic zone in the oligotrophic waters of the subtropical north pacific ocean sea surface temperature and ocean color satellite images are used in this study to show that submesoscale chlorophyll patches are locally intensified these patches are associated with surface temperature fronts and regions of strong stretching of the eddying flow the latter are identified by calculating the finite size lyapunov exponents of the geostrophic flow derived from the sea surface height field from altimetry surface frontogenesis and nonlinear ekman pumping nlep arise as natural candidates for the sporadic generation of large vertical velocities that could favor the formation of these features a high resolution regional numerical model simulation confirms that large vertical velocities are indeed associated with strong density fronts and gradients of relative vorticity using the q vector divergence as a proxy for frontogenetically generated vertical velocities yields good agreement with the model vertical velocities particularly in regions where they are large the pattern and magnitude of nlep suggests that it is also contributing to the strong vertical motions although nlep and model vertical velocities are not necessarily in phase surface frontogenesis and nlep provide a possible explanation for the episodic injection of nutrients at the submesoscale which are then horizontally stirred and modulated by the unstable manifolds of the flow field given that these surface intensified processes would be biogeochemically more effective when the pycnocline is shallow they could also serve as one possible explanation for the late summer chlorophyll blooms that are known to occur in the region

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

shear and richardson number in a mode water eddy abstract measurements of stratification and shear were carried out as part of the eddies tracer release experiment in mode water eddy a4 during the summer of 2005 these measurements were accomplished using both shipboard instrumentation and a drifting mooring a strong relationship between shear intensity and distance from the center of the eddy a4 was observed with the shipboard adcp diapycnal diffusivity at the sf6 tracer isopycnal prior to and during the release was estimated from the drifting mooring to be 2 9 10 6 m2 s 1 diffusivity increased by an order of magnitude to 3 2 10 5 m2 s 1 during the period of the final tracer survey in early september which was similar to the value estimated from the tracer analysis for the whole experiment 3 5 10 5 m2 s 1 ledwell j r mcgillicuddy jr d j anderson l a 2008 nutrient flux into an intense deep chlorophyll layer in a mode water eddy deep sea research ii this issue doi 10 1016 j dsr2 2008 02 005

apparent enhancement of 234th based particle export associated with anticyclonic eddies national basic research program of china 973 program 2009cb421200 national natural science foundation of china nsfc 41121091 41130857

mesoscale eddies and trichodesmium spp distributions in the southwestern north atlantic correlations of trichodesmium colony abundance with the eddy field emerged in two segments of video plankton recorder observations made in the southwestern north atlantic during fall 2010 and spring 2011 in fall 2010 local maxima in abundance were observed in cyclones we hypothesized surface ekman transport convergence as a mechanism for trapping buoyant colonies in cyclones idealized models supported the potential of this process to influence the distribution of buoyant colonies over time scales of several months in spring 2011 the highest vertically integrated colony abundances were observed in anticyclones these peaks in abundance correlated with anomalously fresh water suggesting riverine input as a driver of the relationship these contrasting results in cyclones and anticyclones highlight distinct mechanisms by which mesoscale eddies can influence the abundance and distribution of trichodesmium populations of the southwestern north atlantic