synchronous uplift of the lower crust of the ivrea zone and of southern calabria and its possible consequences for the hercynian orogeny in southern europe abstract along the border of the adriatic microplate pre alpine granulite facies rocks from the deepest crust are outcropping at only two places in the ivrea zone of the southern alps and in southern calabria in these two areas the main features of the present crustal structures i e overlapping of large continental crustal and upper mantle segments are interpreted as resulting from their hercynian geodynamic evolutions the tilted nearly complete crustal sections in both areas display very similar lithological sequences and experienced a common geological evolution as deduced from petrological and radiometric dates at the end of hercynian time 295 m y the ivrea body and the lower crustal rocks of southern calabria were contemporaneously sheared off from the upper mantle and uplifted into intermediate crustal levels where they slowly cooled during mesozoic time the tectonic uplift was accompanied by granitoid plutonism and andesitic to rhyolitic volcanism which continued after the hercynian uplift considering the presently similar crustal structures and the upper carboniferous and permian geological evolutions along the whole adriatic plate boundary the ivrea zone and southern calabria are used to resolve the pre alpine history of the boundary zone between the adriatic and the central european block the uplift of the lower crustal upper mantle flakes of the adriatic block was due to flat overthrusting of these flakes on the continental crust of central europe the material of the central european crust underthrust subducted thereby melted during the re equilibration of the geotherms which had been disturbed by the subduction process this led to an extensive calc alkaline plutonism and volcanism of crustal origin along the adria boundary in this boundary region the overlying uppermost crustal levels schiefergebirgsstockwerk were synchronously folded asturian phase in response to the overlapping of the deeper crustal levels subsequently to the orogeny the mountain chain was eroded and molasse basins developed on the overthrust adriatic crustal segment during the lower permian in this model the granulite facies flakes of the ivrea zone and of southern calabria are interpreted as pre hercynian lower crustal segments which were thrust into the middle crust during the hercynian orogeny thus giving rise to wave velocity inversions in the crust further it is proposed that similar geodynamic processes have played a role in the genesis of the conrad discontinuity which is present in many parts of the hercynian fold belt but only in the ivrea zone and in southern calabria the crustal discontinuities formed in hercynian time were uplifted to the surface as a result of alpine reactivation of the adriatic boundary zone and due to their special positions in the bends of the alpine apennine maghrebide mountain system according to the present knowledge of the carboniferous paleogeography and of the orogenic evolution on both sides of the adria sufure zone this fault zone was located within the european continent its role during the hercynian orogeny is discussed envisaging two possibilities an a subduction zone or a subfluence zone in the sense of behr and weber

anisotropy of vp and vs in an amphibolite of the deeper crust and its relationship to the mineralogical microstructural and textural characteristics of the rock abstract laboratory seismic measurements of compressional v p and shear wave v s velocities have been carried out on a deformed amphibolite from the ivrea zone at pressures and temperatures up to 600 mpa and 600 c respectively amphibolite is considered to be an important rock of the deeper crust from crystallographic orientations of the component minerals hornblende plagioclase and diopside and the respective elastic constants we calculated the average elastic constants voigt average for the rock specimen compressional and shear wave velocities in three orthogonal directions normal and parallel to foliation measured at high confining pressure 600 mpa are in good agreement with the calculated velocity surface this suggests that seismic wave velocity anisotropy is controlled by preferred orientations of minerals in rocks texture at high confining pressure where the effect of microcracks on seismic wave velocities is eliminated in the amphibolite sample the velocity anisotropy is dominated by the texture of hornblende because of the strong preferred orientation and large volume fraction of this mineral species a large s wave splitting is documented in the directions parallel to the foliation particularly in the lineation which strongly argues against the microcrack origin of s wave splitting at least at conditions of high effective pressure

antarctic ozone depletion causes an intensification of the southern ocean super gyre circulation 1 recent climate trends over the southern hemisphere sh summer feature a strengthening of the circumpolar westerly and a weakening of the midlatitude westerly extending from the stratosphere to earth s surface much of the change is attributable to antarctic ozone depletion however the consequential ocean circulation changes are unknown here i demonstrate that the observed surface wind changes have forced a southward shift and spin up of the super gyre which links the subtropical south pacific indian and atlantic ocean circulation advecting more warm water southward the circulation change includes a strengthening of the east australian current eac flow passing through the tasman sea the southward shift may be responsible for the observed unusually large warming in the sh midlatitude ocean and may contribute to the reported range extension to the south of many marine species in the south west pacific

variability and forcing of the east australian current 1 the spatial and temporal variability of the east australian current eac is investigated using 6 years 1993 1998 of surface geostrophic stream function from an optimal interpolation of altimeter sea surface heights and velocities derived from tracking thermal features in satellite imagery variability appears as a series of cyclones and anticyclones propagating southwestward and westward with periods between 90 and 180 days the behavior of the variability changes over the 6 years energy in the mesoscale frequencies moves slowly south and diminishes with more westward propagation in the region where the current separates from the coast we find no evidence for a consistent forcing of the eac by mesoscale signals propagating westward from the south pacific basin we suggest that the observations are consistent with variability originating between 32 s and 35 s through intrinsic instabilities of the current

characterizing frontal eddies along the east australian current from hf radar observations the east australian current eac dominates the ocean circulation along south eastern australia however little is known about the submesoscale frontal instabilities associated with this western boundary current one year of surface current measurements from hf radars in conjunction with mooring and satellite observations highlight the occurrence and propagation of meanders and frontal eddies along the inshore edge of the eac eddies were systematically identified using the geometry of the high spatial resolution 1 5 km surface currents and tracked every hour cyclonic eddies were observed irregularly on average every 7 days with inshore radius 10 km among various forms of structures frontal eddies associated with eac meanders were characterized by poleward advection speeds of 0 3 0 4 m s migrating as far as 500 km south based on satellite imagery flow field kinematics show that cyclonic eddies have high rossby numbers 0 6 1 9 and enhance particle dispersion patches of intensified surface divergence at the leading edge of the structures are expected to generate vertical uplift this is confirmed by subsurface measurements showing temperature uplift of up to 55 m over 24 h and rough estimates of vertical velocities of 10s of meters per day while frontal eddies propagate through the radar domain independently of local wind stress upfront wind can influence their stalling and growth and can also generate large cold core eddies through intense shear such coherent structures are a major mechanism for the transport and entrainment of nutrient rich coastal or deep waters influencing physical and biological dynamics and connectivity over large distances

velocity anisotropy and shear wave splitting in rocks from the mylonite belt along the insubric line ivrea zone italy velocity anisotropy and shear wave splitting has been measured up to 600 mpa on seventeen mylonitic samples from the mylonite belt along the insubric line the rocks which range from felsic to mafic in composition have experienced large ductile strain seismic anisotropy a and shear wave splitting delta vs is significantly pressure dependent velocity anisotropies of p and s waves range from 9 to 27 vp and 10 to 25 vs at 10 mpa and from 4 to 15 and 6 to 17 at 600 mpa respectively oriented microcracks in addition to preferred orientation of anisotropic rock forming minerals contribute largely to velocity anisotropy and shear wave splitting in the low pressure range at high pressure 600 mpa where most of the cracks are closed velocity anisotropy and shear wave splitting is dominated by preferred mineral orientation texture the experimental data at 600 mpa are in fairly good agreement with velocity calculations voigt averages based on volume percentages of major minerals the stiffness tensor of respective rock forming minerals and the measured crystallographic orientation texture related reflection coefficients rc at the protolith mylonite interfaces normal incidence no density change are 0 04 vp and 0 03 vs for extremely anisotropic mylonites a approximate 12 calculations of the variation of reflection coefficients due to velocity anisotropy of p waves in mylonites of different lithologies literature data included give 90 less than 0 1 66 less than 0 05 and 44 less than 0 03 these results suggest that the directional variation of wave velocities in anisotropic mylonites alone does not provide the impedance contrast necessary to give rise for strong seismic reflections

pressure and temperature dependence of p and s wave velocities seismic anisotropy and density of sheared rocks from the sierra alpujata massif ronda peridotites southern spain seismic wave velocities and densities and their pressure and temperature dependence of rock samples recovered from surface exposures at the sierra alpujata were determined in order to better understand the petrological controls on velocity and density the rock samples studied are representative of the major lithologies of the ronda ultramafic body and its metamorphic aureole the suite of ultramafic rocks includes dunite harzburgite and lherzolite exhibiting different degrees of deformation and serpentinization the rocks representing the metamorphic aureole comprise coarse grained migmatites to ultramylonitic migmatites gneisses and eclogites the experimental data include measurements of elastic wave velocities vp vs and densities at confining pressures up to 600 mpa and temperatures up 600 c at 600 mpa the determination of the pressure and temperature derivatives of velocities and densities and the determination of velocity anisotropy average p and s wave velocities at 600 mpa for rocks of the ultramafic body vary from 6 47 to 8 22 km s 1 and 3 27 to 4 75 km s 1 respectively mainly due to different degrees of serpentinization maximum vp and vs anisotropy is about 8 0 and 9 5 respectively and is primarily related to the preferred orientation of olivine in rocks of the metamorphic aureole average p velocities are in the range 5 61 7 23 km s 1 and s velocities vary from 3 48 to 4 04 km s 1 p and s velocity anisotropy is highest about 6 4 and 4 6 in sheared rocks mylonites and is mainly due to the preferred orientation of biotite and sillimanite the geophysical significance of the experimental data is briefly discussed

geological and industrial implications of extensive dilatancy anisotropy extensive dilatancy anisotropy is the hypothesized distribution of stress aligned fluid filled microcracks pervading most rocks in the earth s crust the geometry of the cracks and the aligning stress field can be monitored by analysing the waveforms of shear waves propagating through the rockmass the ability to estimate some of the parameters of the crack and stress geometry by analysing shear wave particle displacements has widespread implications

decadal variability of east australian current transport inferred from repeated high density xbt transects a ctd survey and satellite altimetry a time series of the net geostrophic transport through the tasman sea representing the flow of the east australian current eac extension is determined from a full depth ctd section 15 years of high density xbt transects and satellite altimetry data a section between sydney and wellington px34 has been occupied four times per year since 1991 with high resolution xbt sampling two methods to infer baroclinic transport from proxy data along the section are presented the first uses shallow xbt transects to derive geostrophic transport relative to a deep 2000 m reference level in the second approach synts the subsurface temperature and salinity structure are inferred from satellite surface height and temperature fields using a model developed from historical in situ observations the baroclinic transport is then computed in the usual manner the methods are validated using both a full depth ctd occupation of the px34 section and further transects crossing the eac in the northern tasman sea there is close agreement between the 49 xbt and synts px34 transport estimates obtained between 1992 and 2006 the time series of transport through the sydney wellington section shows a range of temporal signals from eddyscale seasonal interannnual to decadal in particular we note that the net eac flow ranges from 5 sv in 1995 to a maximum of 16 sv in 2000 2001 this decadal variation confirms the eac response to a spin up of the south pacific circulation forced by changes in the basin wide winds and matches the changes in oceanic properties observed in the tasman sea

modes of mesoscale sea surface height and temperature variability in the east australian current 1 mesoscale variability where the east australian current eac separates from the coast is studied using sea surface temperature and surface velocity streamfunction observed by satellite and a regional numerical model the mean circulation simulated by the model the regional ocean modeling system roms is compared to a high resolution regional climatology and the realism of the simulated mesoscale variability is tested by comparison to statistical analyses of the satellite data both roms and data show spectral peaks in the mesoscale energy band at periods between 90 and 180 days complex empirical orthogonal function eof analysis identifies two significant modes of mesoscale variability in the data an eddy mode for which the variability propagates southwestward along the coast and a wave mode for which phase propagation is predominantly onshore the regional model open boundary conditions include only annual and semiannual harmonics of variability so remote mesoscale forcing is absent the eddy mode is represented well in the model indicating this aspect of the circulation results from local instabilities of the flow and that its underlying dynamical process is simulated well while the observed and modeled wave modes have some similarities their differences suggest the model is deficient in representing westward propagation of mesoscale period variability in the region whatever the source of this energy the orthogonality property of the eof analysis indicates the wave mode does not interact significantly with eddy processes in the eac separation

p wave anisotropic tomography of the crust and upper mantle under hokkaido japan abstract we determined a 3 d anisotropic velocity structure beneath hokkaido in northern japan using a large number of first p wave arrival times the travel time inversion is parameterized with an isotropic component and two anisotropic parameters for each grid node by assuming p wave azimuthal anisotropy with hexagonal symmetry axis distributed horizontally the geometries of the conrad and moho discontinuities and the upper boundary of the subducting pacific plate are taken into account in the model our results show that low velocity zones exist beneath active arc volcanoes in the crust and in the central portion of mantle wedge above the high velocity pacific slab which are similar to the previous tomographic images p wave anisotropy is revealed in the crust mantle wedge and the subducting pacific slab in the upper crust the anisotropy is possibly caused by microcracks and cracks in the lower crust the anisotropic structure is different from that in the upper crust and it may be affected considerably by the plastic flow deformation in the mantle wedge the fast velocity direction fvd is generally trench normal in most of the study area while it becomes trench parallel in the pacific coast areas close to the trench which agrees with the shear wave splitting results beneath the volcanic front the fvd is also trench parallel which may suggest the existence of complex 3 d mantle flow in the mantle wedge the fvd in the subducting pacific slab is nearly north south which likely keeps the original fossil anisotropy of the pacific plate formed at the mid ocean ridge or is affected by the olivine fabric transition from a type to b type fabric due to the changes in water content stress and temperature

cyclonic and anticyclonic motion in the upper ocean 1 upper ocean variability is highly energetic and contributes to key processes such as heat transport and water mass formation here the distribution of ocean surface cyclonic and anticyclonic motion is computed from global drifter observations for scales from large eddies to submesoscale two zonal bands of small scale motion are recovered a known anticyclonic band at 30 40 latitude mostly wind induced and an unexpected cyclonic band at 10 20 latitude it is suggested that this is due to submesoscale processes related to salinity front instabilities these results provide a first global view of the upper ocean including these motions

east australian current volume transports at 30 s estimates from the world ocean circulation experiment hydrographic sections pr11 p6 and the pcm3 current meter array between september 1991 and march 1994 the oceanic region off the east coast of australia at 30 s was the subject of an intense observational program part of the world ocean circulation experiment the objective was to improve our understanding of the dynamics of the east australian current eac and to measure its volume and energy flux the two main components were the pacific current meter array 3 pcm3 with six moorings spanning a total distance of 120 km and repeat high resolution hydrographic surveys the long term average frompcm3 shows the eac as a narrow swift and highly variable current centered at 40 km from the coast with strong shear in the upper 1000 m and mean southward velocities of 0 6 m s 1 in the core the measurements also revealed a thick countercurrent underneath the poleward flow the mean volume transport for the entire section covered by the array between the coast and 154 4 e was 22 1 4 6 sv toward the south with an rms variability of 30 sv combining the data from the pcm3 array with the hydrographic sections generated nine detailed snapshots of the absolute geostrophic current field the snapshots were used to evaluate the reliability of the pcm3 data for determining volume transports the rms difference between transports derived from direct current observations and from hydrographie data was 3 8 sv indicating that the pcm3 array can be used to describe the current variability despite the sparse spatial distribution of velocity measurements transport variability was dominated by periods between 90 and 140 days which are attributed to eddy shedding in the region occasional intense northward flow events were observed where total transports reached up to 50 sv northward on those occasions the southward boundary current changed from being surface intensified and mainly baroclinic to northward and more barotropic related to the northward migration past the array of the eac coastal separation point

a numerical modeling study of the east australian current encircling and overwashing a warm core eddy 1 warm core eddies wces often form in the meanders of western boundary currents wbcs wces are frequently overwashed with less dense waters sourced from the wbc we use the regional ocean modelling system to investigate the ocean state during the overwashing of one such wce in october 2008 in the east australian current eac comparisons of model outputs with satellite sea surface temperature and vertical profiles show that the model provides a realistic simulation of the eddy during the period when the eac encircled and then overwashed the eddy during the encircling stage an eddy with closed circulation persisted at depth in the surface eac water entered from the north encircled the eddy and exited to the east the overwashing stage was initiated by the expulsion of cyclonic vorticity for the following 8 days after the expulsion waters from the eac washed over the top of the eddy transferring heat and anticyclonic vorticity radially inward after approximately one rotation period of overwashing the eddy separated the overwashing creates a two layer system that forms a subsurface maximum velocity at the interface of the two layers analysis of water mass properties eulerian tracer dynamics and lagrangian particle tracks show that the original eddy sinks 10 50 m during the overwashing period overwashing has been observed in many wbcs and occurs in most wces in the western tasman sea

the east australian current and property transport at 27 s from 2012 to 2013 abstractthe east australian current eac is the complex and highly energetic poleward western boundary current of the south pacific ocean a full depth current meter and property temperature and salinity mooring array was deployed from the continental shelf to the abyssal waters off brisbane australia 27 s for 18 months from april 2012 to august 2013 the eac mooring array is an essential component of the australian integrated marine observing system imos during this period the eac was coherent with an eddy kinetic to mean kinetic energy ratio of less than 1 the 18 month mean poleward only mass transport above 2000 m is 22 1 7 5 sverdrups sv 1 sv 106 m3 s 1 the mean poleward only heat transport and flow weighted temperature above 2000 m are 1 35 0 42 pw and 15 33 c respectively a difference in the poleward only and net poleward mass and heat transports above 2000 m of 6 3 sv and 0 24 pw reflects the presence of an equatorward eac retroflection at the eastern offshore end of the

boron in chondrules isotopic compositions and abundances of boron were measured in sixteen chondrules from seven chondrites by ion microprobe mass spectrometry the chondrules are of the porphyritic barred and radial type and host meteorites include carbonaceous ordinary and enstatite chondrites boron abundances are generally low with average boron concentrations of between 80 and 500 ppb these abundances are lower than those of bulk chondrites 0 35 to 1 2 ppm zhai et al 1996 confirming earlier suggestions that boron is mostly contained in the matrix no significant variation in the 11b 10b ratio is observed among these chondrules outside our experimental error limits of several permil and b isotopic compositions agree with those reported for bulk chondrites the lack of a significant isotope fractionation between chondrules and matrix implies that the low boron abundances are not the result of a rayleigh fractionation during chondrule formation isotopic heterogeneities within individual chondrules are constrained to be 20 0 at 95 confidence level at a spatial scale of 20 30 m significantly lower than the value of about 40 0 previously reported for chondrules from carbonaceous and ordinary chondrites chaussidon and robert 1995 1998 the observed b isotopic homogeneity does not conflict with the presence of decay products from extinct 10be with 10be 9be 0 10 3 as was inferred for calcium aluminum rich inclusions extinct 10be in chondrules would shift the abundance ratio 11b 10b at best by several permil because of their commonly observed low be b ratios 2 the results show that potential b isotopic heterogeneities in the solar nebula due to the presence of components with different b isotopic signatures such as boron produced by high energy galactic cosmic rays 11b 10b 2 5 or by the hypothetical low energy particle irradiation 11b 10b 3 5 11 or boron from type ii supernovae 11b 10b 1 did not survive the chondrule formation processes to a measurable extent

mechanisms of the 40 70 day variability in the yucatan channel volume transport the yucatan channel connects the caribbean sea with the gulf of mexico and is the main outflow region of the caribbean sea moorings in the yucatan channel show high frequent variability in kinetic energy 50 100 days and transport 20 40 days but the physical mechanisms controlling this variability are poorly understood in this study we show that the short term variability in the yucatan channel transport has an upstream origin and arises from processes in the north brazil current to establish this connection we use data from altimetry and model output from several high resolution global models a significant 40 70 day variability is found in the sea surface height in the north brazil current retroflection region with a propagation toward the lesser antilles the frequency of variability is generated by intrinsic processes associated with the shedding of eddies rather than by atmospheric forcing this sea surface height variability is able to pass the lesser antilles it propagates westward with the background ocean flow in the caribbean sea and finally affects the variability in the yucatan channel volume transport

oceanic turbulence and stochastic models from subsurface lagrangian data for the northwest atlantic ocean the historical dataset provided by 700 m acoustically tracked floats is analyzed in different regions of the northwestern atlantic ocean the goal is to characterize the main properties of the mesoscale turbulence and to explore lagrangian stochastic models capable of describing them the data analysis is carried out mostly in terms of lagrangian velocity autocovariance and cross covariance functions in the gulf stream recirculation and extension regions the autocovariances and cross covariances exhibit significant oscillatory patterns on time scales comparable to the lagrangian decorrelation time scale they are indicative of sub and superdiffusive behaviors in the mean spreading of water particles the main result of the paper is that the properties of lagrangian data can be considered as a superposition of two different regimes associated with looping and nonlooping trajectories and that both regimes can be parameterized using a simple first order lagrangian stochastic model with spin parameter v the spin couples the zonal and meridional velocity components reproducing the effects of rotating coherent structures such as vortices and mesoscale eddies it is considered as a random parameter whose probability distribution is approximately bimodal reflecting the distribution of loopers finite v and nonloopers zero v this simple model is found to be very effective in reproducing the statistical properties of the data

quantitative mapping of the east australian current encroachment using time series himawari 8 sea surface temperature data the east australian current eac is a highly dynamic western boundary current that exerts significant influences on the marine ecosystem off south east margin of australia for the first time a quantitative mapping of the eac system was conducted using himawari 8 sea surface temperature data and a topographic position index tpi based image processing technique the validation using bluelink reanalysis data suggested good reliability of our mapping results subsequent quantitative examination provides new insights into the eac s cross shelf movement which is a driving force of adjacent slope shelf circulations along the coast of new south wales nsw large scale and high frequency eac encroachment was observed being every 60 80 days upstream 30 32 s and every 90 100 days downstream 33 35 s which is associated with the eac s intrinsic oscillation and eddy shedding downstream the eac encroachment exhibits a 20 day longer period and a double amplitude such dephasing is most likely due to the abrupt change of regime at the eac separation point 32 33 s upstream the eac encroachment also exhibits seasonality being 10 15 km closer to the coast in austral summer which is due to the seasonal eac broadening higher frequency 16 32 days and smaller magnitude eac intrusion was observed along the entire nsw coast 28 37 s which is possibly associated with eac s meanders and frontal eddies in the extension zone 37 30 44 s we observed maximum eac encroachment in summer which is an expression of the seasonal boundary flow off eastern tasmania a dataset of eac encroachment 2015 2017 is available see data availability

the fraser gyre a cyclonic eddy off the coast of eastern australia this paper examines the on shelf circulation of the eastern australian continental shelf for a region off southeast queensland we identify a characteristic seasonally reoccurring wind driven cyclonic flow it influences the cross shelf exchange with the east australian current eac which is the western boundary current of the south pacific ocean we refer to this cyclonic circulation as the fraser gyre it is located south of fraser island between about 25 s and 27 s the region is adjacent to the intensification zone of the eac where the current accelerates and establishes a swift albeit seasonally variable southward boundary flow through the analysis of several data sets including remotely sensed sea surface temperature and sea surface height anomaly satellite tracked surface drifters ocean and atmospheric reanalysis data as well as geostrophic currents from altimetry we find that the on shelf fraser gyre develops during the southern hemisphere autumn and winter months the gyre is associated with a longshore near coast northward flow maximum northward on shelf depth averaged velocities are estimated with about 0 15 0 26 ms 1 the flow turns eastward just to the south of fraser island and joins the persistent southward eac flow along the shelf break the annual mean net cross shelf outward and inward flow associated with the gyre is about 1 17 0 23 sv in the north and 0 23 0 13 sv 1 sv 106 m3s 1 in the south mean seasonal water renewal time scales of the continental shelf are longest during austral winter with an average of about 3 3 days due to the fraser gyre retaining water over the shelf however monthly estimates range from 2 to 8 days with the longer timescale during the austral autumn and winter the southerly wind during austral autumn and winter is identified as controlling the on shelf circulation and is the principal driver of the seasonally appearing fraser gyre the conceptual model of the fraser gyre is consistent with general physical principals of the coastal shelf circulation a southerly wind is associated with surface layer flow toward the coast a near coast positive ssha with a current in the direction of the wind down welling and export of shelf water the fraser gyre influenced cross shelf exchanges are possibly facilitating the offshore transport of fish larvae sediments nutrients river discharges and other properties across the shelf break and into the southward flowing eac during the austral autumn and winter

elastic wave velocities in rocks from a lower crustal section in southern calabria italy compressional and shear wave velocities vp and vs have been measured on 14 rock samples recovered from a high grade metamorphic terrane in the southern part of the calabrian massif which is considered to represent a continuous section of a former deep continental crust the experiments have been carried out in a cubic anvil apparatus at constant confining pressures up to 600 mpa and temperatures ranging from 20 to 700 c using the ultrasonic transmission technique at 600 mpa the compressional and shear wave velocities range from 6 33 km s 1 to 7 74 km s 1 and from 3 54 km s 1 to 4 30 km s 1 respectively variations in velocity are strongly related to variations in mineralogy both vp and vs increase with increasing amphibole pyroxene garnet and sillimanite content the range of velocities measured in the granulite facies rocks under conditions of lower crustal depth is similar to the range of seismic velocities for the crust beneath calabria importantly the metapelite rocks with intermediate silica and high alumina contents have in situ compressional and shear wave velocities which are equivalent to the mafic rocks or even significantly higher the detected high velocity layer at a depth between 15 and 20 km can be explained by a sequence of garnet cordierite sillimanite gneisses for which actual velocities between 6 6 and 7 6 km s 1 have been determined experimentally

an avenue of eddies quantifying the biophysical properties of mesoscale eddies in the tasman sea 1 the tasman sea is unique characterised by a strong seasonal western boundary current that breaks down into a complicated field of mesoscale eddies almost immediately after separating from the coast through a 16 year analysis of tasman sea eddies we identify a region along the southeast australian coast which we name eddy avenue where eddies have higher sea level anomalies faster rotation and greater sea surface temperature and chlorophyll a anomalies the density of cyclonic and anticyclonic eddies within eddy avenue is 23 and 16 higher respectively than the broader tasman sea we find that eddy avenue cyclonic and anticyclonic eddies have more strongly differentiated biological properties than those of the broader tasmansea as a result of larger anticyclonic eddies formed from coral sea water depressing chl a concentrations and for coastal cyclonic eddies due to the entrainment of nutrient rich shelf waters cyclonic eddies within eddy avenue have almost double the chlorophyll a 0 35 mg m 3 of anticyclonic eddies 0 18 mg m 3 the average chlorophyll a concentration for cyclonic eddies is 16 higher in eddy avenue and 28 lower for anticyclonic eddies when compared to the tasman sea with a strengthening east australian current the propagation of these eddies will have significant implications for heat transport and the entrainment and connectivity of plankton and larval fish populations citation everett j d m e baird p r oke and i m suthers 2012 an avenue of eddies quantifying the biophysical properties of mesoscale eddies in the tasman sea geophys res lett 39 l16608 doi 10 1029 2012gl053091

physical properties of crustal and upper mantle rocks with regards to lithosphere dynamics and high pressure mineralogy this paper focusses on the physical properties of rocks and property changes occurring during geodynamic processes it addresses a number of outstanding petrophysical problems in the framework of crustal and mantle deformation the major themes to be discussed will be the seismic signature of crustal and mantle shear zones the nature of crustal and mantle anisotropy and the contribution of anisotropic rocks to seismic reflectivity in particular seismic shear waves traversing anisotropic strata can reveal important information on the spatial orientation of deformed structures because the measured seismic anisotropy has a structural origin emphasis will be placed on the relations between shear wave splitting and fabric anisotropy fabric anisotropy and strain and strain and geologic tectonic processes the second part of this paper discusses the effect that metamorphic phase transitions in crustal and mantle rocks may have on rock physical properties velocity density specifically the possible role that the gabbro eclogite transition could have in crustal delamination and recycling of material into the mantle will be considered

the nature of seismic reflections from deep crustal fault zones deep seismic reflection profiles have recorded reflections from ductile shear zones within the crystalline basement perhaps the best example is the consortium for continental reflection profiling cocorp wind river line in wyoming which shows the wind river thrust fault to be a strong reflector from the surface to depths of about 30 km to identify the physical properties responsible for the seismic reflections from fault zones we report measurements of compressional wave velocity and velocity anisotropy in mylonites recovered from exhumed ductile shear zones these rocks are characterized by extensive ductile deformation of plastic minerals brittle deformation of the more rigid minerals grain size reduction and development of a strong fabric average velocity and density were not found to change significantly and systematically between the mylonites and the adjacent undeformed rock seismic anisotropy of 7 or greater is present in several mylonites dependent upon their composition and fabric using our data on mylonite properties and models for the crustal structure near the wind river line we compute true amplitude synthetic reflection seismograms and compare them to true amplitude plots of the cocorp wind river reflection data when anisotropy and the finely laminated structure of the fault zone are considered our modeling indicates fairly strong reflections from mylonite zones in most cases we also show that elevated pore pressure in shear zones may produce strong reflections however a permeability of the order of 10 16 darcy is required to maintain sufficient pore pressure to produce a velocity anomaly in a fault zone which has long been inactive

elastic properties of anisotropic synthetic calcite muscovite aggregates 1 a set of synthetic aggregates containing mixtures of calcite and muscovite were compacted with varying uniaxial loads ranging from 20 mpa up to 400 mpa their elastic properties have been measured using compressional and shear waves in confining hydrostatic pressures up to 475 mpa measured seismic velocities are shown to depend on 1 the ratio of calcite to muscovite 2 the uniaxial load used during sample manufacturing and 3 the porosity amount prior to velocity measurements the matrix framework may also affect the seismic velocities but this effect is not easily quantifiable in general measured seismic velocities decrease with increasing muscovite content and porosity elastic properties have been calculated based on texture measurements which were obtained by neutron diffraction the calculated velocities are based on the calcite and muscovite single crystal elastic tensors their orientation distribution functions and their modal fractions a large discrepancy is apparent between calculated and measured velocities where the former always overestimate the actual velocities shear waves display less of a difference between calculated and measured values than do compressional waves indicating that waves propagating by shearing are less affected by sample porosity and matrix framework a better agreement between measured and calculated seismic velocities arises when the initial porosity is taken into account using a differential effective medium model seismic anisotropy is evident from both measured and calculated velocities and is low for samples containing pure calcite but becomes prominent as the muscovite concentration increases the intensity of anisotropy further depends on the uniaxial load used during sample compaction and the initial porosity

eddy shedding and energy conversions in the east australian current 1 mesoscale variability and eddy shedding in the tasman sea particularly of the east australian current eac is studied through the analysis of remotely sensed observations and outputs from a global ocean model previous observations of the western boundary current separation from the coast showed strong variability at periods ranging between 90 and 140 days we show from satellite altimetric observations that rapid northward migration of the separation point of the eac follows the formation of large eddies at periods of 100 days after an eddy separation event the normally southward flowing current swiftly assumes a more zonal configuration near the separation latitude with a cyclonic circulation developing inshore the formation of large separation eddies is preceded by the southward propagation of sea level anomalies along the east australian continental slope from 25 s sea level anomalies grow as they travel south eventually being pinched off in the form of large anticyclones at 32 s in the current retroflection area energy conversion terms in a global ocean model and in altimetric data suggest both barotropic and baroclinic instability may account for the growth of these anomalies as they propagate south east of the main eac jet there is evidence that eddies may be feeding potential energy back to the mean flow

the seismic reflection character of the continental mohorovicic discontinuity the continental mohorovicic discontinuity is most often interpreted as a step function velocity boundary however on deep crustal seismic reflection profiles reflections at depths where refraction data places the moho have laminated character and are laterally discontinuous these observations on continental reflection data point to a model of the moho that has thin layered rather than block structure previous workers who have synthetically generated seismic responses from various crust mantle boundary models have shown that thin layered models of alternating high and low velocity generate responses that best emulate observed moho arrivals geologic interpretations of the thin layering include relatively undeformed metasediments cumulate layering tectonic banding and lenses of partial melt to obtain more direct geologic evidence a synthetic seismogram is generated from geologic cross sections of the ivrea verbano zone an exposed section through the lower crust and upper mantle the synthetic shows laminations similar to those observed on reflection data without more direct evidence no single geologic interpretation of the moho is reasonable indeed the moho may be a laterally variable boundary its composition and structure dependent upon the geologic history of the overlying crust

seismic reflectivity of mylonite zones in the crust deep fault zones are characterized by mylonitic rocks with strong preferred orientation of constituent minerals and retrograde mineral assemblages sonic velocities are consequently lower for propagation directions normal to mylonite foliation than in surrounding unmylonitized rocks synthetic seismograms computed for low velocity near horizontal thick mylonite zones of complex laminated geometry show multicyclic reflections with amplitudes up to twice those generated by a single interface seismic characteristics of mylonite zones are sufficient to produce reflections in crystalline rocks provided noise levels are relatively low

simultaneous core sample measurements of elastic properties and resistivity at reservoir conditions employing a modified triaxial cell a feasibility study adaptations of existing triaxial cells for ultrasonic p and s wave measurements are well documented this paper proposes further modification of such a cell so that also resistivity measurements can be carried out simultaneously at reservoir conditions by employing the top cap and the pedestal of the cell as electrodes axial resistivity measurements are now feasible in order to minimize the polarization effect of this two electrode arrangement careful analyses have been carried out to optimize the choice of electrode coating and measurement frequency band radial resistivity measurements are also included in the system by introducing a strap electrode system in a reservoir under production changes in both saturations temperature if steam injection and stresses can take place therefore the modified triaxial system should be able to measure the integrated effects on the acoustic parameters and electric responses caused by variations in each of these parameters the feasibility of the system to obtain such reliable information is demonstrated employing a small selection of core samples in the future such combined measurements on reservoir core samples can be used to link both seismic and electromagnetic observations to the actual earth model and constrain both modelling and inversion

on the cross shelf exchange driven by frontal eddies along a western boundary current during austral winter 2007 western boundary currents are characterized by high mesoscale eddy activity including that of cyclonic frontal eddies cfes these form frequently adjacent to the shelf break export coastal water and affect biological productivity here we study the physical properties of eddies identified within the intensification zone of the east australian current eac through the analysis of remotely sensed data the application of an ocean circulation model and the evaluation of lagrangian simulations during austral winter 2007 we examine the spatial and temporal evolution of identified eddies investigate their formation mechanism and quantify the contribution made to cross shelf exchanges the mesoscale eddies are tracked from generation to decay using an eddy detection and tracking method in this case study we identify two cfes referred to as c1 and c2 with lifetimes of 11 and 38 days and radii of 45 and 70 km respectively and one anticyclonic eddy ace with a lifetime of 62 days and a radius of 60 km both cfes interact with the ace leading to quasi stationary dipole eddies located in the vicinity of the shelf this is the first time dipole eddies are reported for the intensification zone of the eac the location of cfes characterised by negative sea surface height anomaly ssha and clockwise rotation coincides with remotely sensed sea surface temperature sst and chlorophyll a chl a anomalies cfes c1 and c2 appear to contribute in different ways to the cross shelf transport along the shelf break cfe c1 drives a stronger onshore transport while cfe c2 appears to enhance the offshore transport the estimated daily cross shelf export of shelf water associated with cfe c2 is estimated with about 1 23 sv 106 km3 day 1 it renews the regional shelf water in about 7 days the lifetime of cfe c2 is about 38 days thus the eddy had the potential to flush the shelf at least five times the transient cfes were found for the first time to intensify the cross shelf exchange that is due to the wind driven cyclonic circulation of the fraser gyre this seasonally occurring gyre dominates the local shelf during austral autumn and winter the results from this study demonstrate the importance of cfes in exporting cooler and chl a enriched shelf water into the warmer and oligotrophic waters of the southward flowing eac

influence of a western boundary current on shelf dynamics and upwelling from repeat glider deployments the separation zone of a dynamically important western boundary current wbc is resolved through a series of sustained glider deployments along the coastal edge of the jet the comprehensive data set from 23 missions 2008 2014 provides a new high resolution hydrographic climatology which is exploited to understand the spatial extent of dense water uplift and the depth averaged momentum balances across the east australian current eac separation zone the predominantly geostrophic shelf circulation and temperature fields are least most variable upstream downstream where encroachment separation dominates for the first time we resolve the nonlinear advection terms which are considerable in the along shelf momentum balance near bottom water masses indicate dense water uplift as a result of the eac encroachment and separation the data provide both new insight into and a climatology of separation induced uplift and demonstrate a successful model for repeat glider missions in a dynamic wbc environment

a model of velocity structure beneath calabria southern italy based on laboratory data abstract laboratory velocity measurements of representative rock samples from across a nearly complete crustal section from the serre mountains of southern calabria have been carried out as an aid to interpreting in situ seismic velocity data the section is composed of interlayered acidic mafic and pelitic rocks metamorphosed to granulite and amphibolite facies conditions in addition a suite of post tectonic granitoids intrudes the section the experimental data include the measurement of compressional wave vp and shear wave vs velocities at confining pressure in conjunction with structural and stratigraphic field data the experimentally determined data are used to construct a seismic velocity model for the crust beneath calabria in the upper crustal levels vp and vs vary in different manners below the uppermost amphibolite facies gneisses a weak velocity inversion of vp is associated with the post tectonic granites at the granite granodiorite and the tonalite dioritic gneiss boundary vp increases in steps of about 200 and 300 m s respectively in contrast vs remains constant or even decreases slightly through this same sequence of rocks this contrasting behaviour is primarily related to the quartz feldspar ratio in the rocks the most pronounced velocity jump occurs at the top of the granulite facies metapelite unit here both vp and vs increase markedly due to mineralogic changes that accompany increasing metamorphic grade and the greater abundance of mafic and garnet bearing restites of partially melted pelite the mafic rocks of the lowermost crustal layer have p and s wave velocities that are significantly lower than those in the overlying metapelites the variation of poisson s ratio with depth suggests that this parameter which is a combination of vp and vs is more sensitive to lithology than the p and s wave velocities alone in rock units of upper and mid crustal levels with average p wave velocities

the response of the southern annular mode the east australian current and the southern mid latitude ocean circulation to global warming 1 climate models predict an upward trend of the southern annular mode sam in response to increasing atmospheric co2 concentration however the consequential impact of this change on oceanic circulation has not been explored here we analyse the outputs of a series of global warming experiments from the csiro mark 3 climate model we show that although for the zonal wind stress change the maximum is located at approximately 60 s in terms of the change in surface wind stress curl the maximum is situated at approximately 48 s this change in the wind stress curl causes a spin up of the entire southern midlatitude ocean circulation including a southward strengthening of the subtropical gyres particularly the east australia current eac the intensified eac generates a warming rate in the tasman sea that is the greatest in the southern hemisphere sh with significant implications for sea level rise the pan southern ocean scale suggests a broad impact on the marine ecosystem of the entire southern midlatitude ocean

drivers of decadal variability in the tasman sea in this study we compare optimally interpolated monthly time series tasman sea xbt data and a comprehensive set of ocean data assimilation models forced by atmospheric reanalysis to investigate the stability of the tasman sea thermocline and the transport variability of the east australian current eac the tasman front and eac extension we find that anomalously weaker eac transport at 25 s corresponds to an anomalously weaker tasman front and anomalously stronger eac extension we further show that post about 1980 and relative to the previous 30 years the anomalously weaker eac transport at 25 s is associated with large scale changes in the tasman sea specifically stronger stratification above the thermocline larger thermocline temperature gradients and enhanced energy conversion significant correlations are found between the maria island station sea surface temperature sst variability and stratification thermocline temperature gradient and baroclinic energy conversion suggesting that nonlinear dynamical responses to variability in the basin scale wind stress curl are important drivers of decadal variability in the tasman sea we further show that the stability of the eac is linked via the south caledonian jet to the stability of the pan basin subtropical south pacific ocean storm track

petrology of felsic granulites metapelites metabasics ultramafics and metacarbonates from southern calabria italy prograde metamorphism uplift and cooling of a former lower crust

experimental determination of elastic properties of talc to 800 c 0 5 gpa calculations of the effect on hydrated peridotite and implications for cold subduction zones abstract we have measured compressional wave velocity v p in talc as a function of temperature at 0 5 gpa v p falls from 5 27 0 23 km s 1 at 25 c to 4 35 0 15 km s 1 at 800 c combining these results with a previously published bulk modulus k and k p gives a poisson s ratio of 0 268 and a shear modulus g of 22 6 gpa under atmospheric conditions assuming that is independent of temperature gives a k t value of 19 3 0 64 mpa k 1 at 0 5 gpa we used the experimental data in combination with published data to calculate bounds on the elastic moduli of a peridotite hydrated with talc just above cold subducting lithosphere we find that an assemblage hydrated by only 0 9 wt h 2 o has elastic wave velocities calculated from the voigt reuss hill average lower than the anhydrous rock by an average of 7 6 for v p and 9 7 for shear waves v s at 700 c these results are consistent with observations of converted phase behavior in the vicinity of the surface of a cold subducting slab and may place the low velocity layer observed in the lowermost mantle wedge not the uppermost slab as has previously been suggested

fabric related velocity anisotropy and shear wave splitting in rocks from the santa rosa mylonite zone california the directional dependence of p and s wave velocities have been measured at pressures up to 600 mpa and temperatures up to 700 c in rocks from the santa rosa mylonite zone southern california during tectonism these were progressively deformed from granodiorite protolith to mylonite and ultimately phyllonite the mineralogical and chemical composition of protolith and mylonite is nearly identical thus these rocks provide excellent material for documenting the effect of microstructural and textural changes on rock anisotropy velocity anisotropy increases significantly with the degree of deformation whereas average velocities and densities do not change at low pressure 50 mpa the velocity anisotropy ranges from 1 7 in granodiorite up to 19 in phyllonite and is due to both oriented microfractures and crystallographic preferred orientation at high pressure 600 mpa the residual anisotropy up to 12 is mainly due to preferred mineral orientation in particular of biotite significant shear wave splitting is measured parallel to the foliation plane and shows a good correlation with the biotite texture these observations confirm that oriented microcracks and preferred orientation of minerals should be taken into account in the interpretation of seismic reflection and refraction data in terranes with deformed rocks

seismic velocity and anisotropy in mylonites and the reflectivity of deep crystal fault zones compressional wave velocity anisotropy has been measured to 1 kb confining pressure in several mylonites in one cataclasite and in their protoliths no significant difference in the velocity or density was found between the protolith and the tectonically altered rock at 1 kb strong seismic anisotropy greater than 10 was present in only two of nine mylonites measured the anisotropy was due to their aphanitic texture high content of layered silicates and pervasive foliation most mylonitic rocks studied were not strongly anisotropic despite a well developed macroscopic foliation where anisotropy was present velocities usually were slowest perpendicular to the foliation and fastest parallel to both foliation and lineation these preliminary results suggest that ductile fault zones in the crust are not strong seismic reflectors unless mylonites in the fault zone are aphanitic and contain large amounts of foliated phyllosilicates it is also possible that anomalous environmental conditions such as high pore pressure in the fault zone in situ may explain observed seismic reflectivity

recent freshening of the east australian current and its eddies the east australian current eac has a relatively weak mean flow and an energetic eddy field that dominates the circulation the properties of the mean flow have been studied in detail but the changes in the eddy field have received little attention we analyze argo temperature and salinity profiles for 2005 2012 to construct a picture of the time mean and time varying properties of eac eddies we find that eddies and the surrounding waters of the western tasman sea are freshening at a rate of 0 017 0 025 practical salinity unit yr over the top 100 m with no significant temperature change consistent with the observations fields from an eddy resolving ocean model show freshening with no temperature trend moreover the model results indicate that observed changes are significant in the context of the variability over the last 20 years and may be part of a multiyear perhaps decadal cycle we attribute the freshening of the region to increased precipitation off eastern australia

southern ocean origin of multidecadal variability in the north brazil current analysis of model data from a long 200 years simulation of a high resolution version of the parallel ocean program indicates a connection between a mode of multidecadal variability in the southern ocean the so called southern ocean mode and multidecadal variability in the north brazil current the multidecadal sea surface height variability in the southern ocean propagates northward and submerges at about 40 s northward propagating anomalies in ocean heat content are found between 5 and 40 s at depths down to 1 km and affect the north brazil current similar variability and connections between southern ocean and north brazil current are also found in a 200 years simulation of a high resolution global version of the community earth system model the results provide a new mechanism for the low frequency variability of the north brazil current

on the variability of the east australian current jet structure meandering and influence on shelf circulation given the importance of western boundary currents over a wide range of scales in the ocean it is crucial that we understand their dynamics to accurately predict future changes for this we need detailed knowledge of their structure and variability here we investigate the jet structure of the east australian current eac using observations from hf radars and moorings deployed at 30 s 31 s meandering core velocity width and eddy kinetic energy eke are quantified from 4 years of hourly 1 5 km resolution surface current maps 2012 2016 to obtain the most detailed representation of the surface eac jet to date the eac flows predominantly over the 1 500 m isobath 50 km offshore but makes large amplitude displacements eastward every 65 100 days the time scale associated with mesoscale eddy shedding at the eac separation smaller amplitude higher frequency meanders occur every 20 45 days using a coordinate frame that follows the jet we show core velocity and eke exhibit seasonality in both magnitude and variance being maximum in summer 1 55 m s 1 mean core velocity minimum in winter 0 8 m s 1 however it is the eddy shedding time scale that dominates jet variability as the eac moves shoreward shelf temperature and along stream velocity vary linearly with jet movement within 35 km of the core the eac is within this range 75 of the time demonstrating its importance to the shelf circulation temperature and velocity fluctuations at the 70 m 100 m isobath are more influenced by wind eac encroachment with the strongest response occurring when wind and eac act constructively

an illustration of the advantages of a complete texture analysis described by the orientation distribution function odf using quartz pole figure data abstract the preferred orientation of eight crystal directions of quartz was measured with an x ray texture goniometer for selected quartz bearing tectonites with a clear pattern of c axis preferred orientation the advantages of data analysis by means of calculations of the orientation distribution function and other forms of data presentation derived from the odf are demonstrated

the separation of the east australian current a lagrangian approach to potential vorticity and upstream control the east australian current eac is the western boundary current flowing along the east coast of australia separating from the coast at approximately 34 s after the separation two main pathways can be distinguished the eastward flowing tasman front and the extension of the eac flowing southward the area south of the separation latitude is eddy rich and the separation latitude of the eac is variable little is known of the properties of the water masses that separate at the bifurcation of the eac this paper presents new insights from the lagrangian perspective where the water masses that veer east and those that continue south are tracked in an eddy permitting numerical model the transport along the two pathways is computed and a 1 3 ratio between transport in the eac extension and transport in the tasman front is found the results show that the fate of the particles is to first order already determined by the particle distribution within the eac current upstream of the separation latitude where 85 of the particles following the eac extension originate from below 460 m and 90 of the particles following the tasman front originate from the top 460 m depth at 28 s the separation and pathways are controlled by the structure of the isopycnals in this region analysis of anomalies in potential vorticity show that in the region where the two water masses overlap the fate of the water depends on the presence of anticyclonic eddies that push isopycnals down and therefore enable particles to travel further south

wind forced variability in eddy formation eddy shedding and the separation of the east australian current the east australian current eac like many other subtropical western boundary currents is believed to be penetrating further poleward in recent decades previous observational and model studies have used steady state dynamics to relate changes in the westerly winds to changes in the separation behavior of the eac as yet little work has been undertaken on the impact of forcing variability on the eac and tasman sea circulation here using an eddy permitting regional ocean model we present a suite of simulations forced by the same time mean fields but with different atmospheric and remote ocean variability these eddy permitting results demonstrate the nonlinear response of the eac to variable nonstationary inhomogeneous forcing these simulations show an eac with high intrinsic variability and stochastic eddy shedding we show that wind stress variability on time scales shorter than 56 days leads to increases in eddy shedding rates and southward eddy propagation producing an increased transport and southward reach of the mean eac extension we adopt an energetics framework that shows the eac extension changes to be coincident with an increase in offshore upstream eddy variance via increased barotropic instability and increase in subsurface mean kinetic energy along the length of the eac the response of eac separation to regional variable wind stress has important implications for both past and future climate change studies

observed and simulated lagrangian and eddy characteristics of the east australian current and the tasman sea new insights into the lagrangian and eddy dynamical processes within the east australian current eac and the tasman sea are presented we briefly discuss the past campaigns undertaken to observe the eac and the tasman sea eddies as well as the motivation to renew the deployment of drifting buoys into the eac and the tasman sea the specific features discussed are motivated by the recent observing campaigns using drifting buoys and the availability of high spatial and temporal resolution estimates of the ocean state and circulation from eddy resolving models the interpretation of these features is also aided by other components of the ocean observing system the dynamics presented includes a transient eac separation through a vortex dipole b stratified vortex mergers and secondary circulation of eac eddies c eddy networks in the tasman sea and d formation and propagation of the eac separation point the importance of these dynamical features to the eac and the tasman sea and their implications for the observing system and modelling are discussed

observations of submesoscale variability and frontal subduction within the mesoscale eddy field of the tasman sea abstractsubmesoscale lenses of water with anomalous hydrographic properties have previously been observed in the east australian current eac system embedded within the thermocline of mesoscale a

decadal spinup of the south pacific subtropical gyre abstract an increase in the circulation of the south pacific ocean subtropical gyre extending from the sea surface to middepth is observed over 12 years datasets used to quantify the decadal gyre spinup include satellite altimetric height the world ocean circulation experiment woce hydrographic and float survey of the south pacific a repeated hydrographic transect along 170 w and profiling float data from the global argo array the signal in sea surface height is a 12 cm increase between 1993 and 2004 on large spatial scale centered at about 40 s 170 w the subsurface datasets show that this signal is predominantly due to density variations in the water column that is to deepening of isopycnal surfaces extending to depths of at least 1800 m the maximum increase in dynamic height is collocated with the deep center of the subtropical gyre and the signal represents an increase in the total counterclockwise geostrophic circulation of the gyre by at least 20 at 1000 m a comparison of woce and

mesoscale structure of the mean east australian current system and its relationship with topography abstract we document the mean circulation of the east australian current eac system which is the major western boundary current in the southwest pacific ocean a new high resolution climatology of the region csiro atlas of regional seas cars is used to produce regional fields of steric height and sections of geostrophic velocity the realism of these fields has been enhanced by the high spatial resolution allowance for bathymetric control and the influence of land barriers the increased detail in the maps and sections reveal the major influence that the complex regional topography has on the circulation the results also provide the appropriate resolution for comparison with recent model studies of the region we have been able to both resolve well known features with greater detail and identify previously unrecognized aspects of the circulation important results include 1 the zonal inflow north of 30 s breaks into a series of individual jets after flowing through the island chains as suggested by recent model results 2 the interaction of the zonal inflow with the local topography as it undergoes bifurcation is documented 3 a detailed picture of the evolution of the eac at the western boundary is presented including surface currents and transports 4 separation and recirculation of the eac within the tasman abyssal basin are shown to occur as a double cell structure constrained by bathymetry 5 the eac outflow is resolved as a series of eastward and northeastward currents 6 the path of the tasman front is defined as it interacts with the tasman ridge systems 7 a quasi permanent eddy is identified for the first time adjacent to the norfolk ridge northwest of new zealand

long term trends in the east australian current separation latitude and eddy driven transport an observed warming of the tasman sea in recent decades has been linked to a poleward shift of the maximum wind stress curl and a strengthening of the poleward flow along the coast of southeastern australia however changes in the east australian current eac separation latitude as well as in the contribution of the eac the eac extension and its eddy field to the total southward transport due to such a strengthening remain unknown this study uses 30 years 1980 2010 of the ocean forecast for the earth simulator ofes sea surface height and velocity outputs to obtain a three decade long time series of i the eac separation latitude ii the southward transport along the coast of southeastern australia 28 s 39 s and iii the southward transport across the eac separation latitude a lagrangian approach is implemented and the spin parameter is used to provide a quantitative distinction between the transports occurring outside and inside cyclonic and anticyclonic eddies significant positive trends of the low pass southward transports indicate that the intensification of the poleward flow has occurred both within the eac and in the eac extension in addition a significant increase in southward transport inside and outside eddies is found importantly the contribution of eddy driven transport has a large temporal variability and shows a sharp increase from 2005 onward finally our results show that the eac has not penetrated further south but it has separated more frequently at the southernmost latitudes within the region where it typically turns eastward

the cold core eddy and strong upwelling off the coast of new south wales in early 2007 abstract during the austral summer of 2006 07 a series of extreme oceanic events occurred in the tasman sea following a series of strong wind driven upwelling events an intense cold core eddy developed off sydney australia a data assimilating eddy resolving ocean model is used to create a three dimensional time varying reanalysis of these events the reanalysis indicates that the cold anomalies associated with the upwellings were in excess of 5 c near the coast where sea level decreased by as much as 0 2 m the reanalysed three dimensional structure of the cold core eddy shows the eddy leaning to the west north west in towards the continental shelf the diameter of the eddy is about 100 km and the sea level anomaly at the eddy centre peaks at around 1 m with an associated sub surface temperature anomaly in excess of 8 c at 200 m depth corresponding to an upward isotherm excursion of 600 m the circulation around the cyclonic eddy is ageostrophic with upwelling in the southern sector of the eddy where flow is onshore and climbing the continental slope and downwelling in the northern sector where flow is descending off the slope three dimensional trajectories of water parcels around the eddy involve 50 100 m vertical excursions based on the reanalysed circulation and composite satellite images of chlorophyll a we hypothesise that the circulation around the eddy led to significant nutrient enrichment in the euphotic zone around the perimeter of the eddy

a tale of two eddies the biophysical characteristics of two contrasting cyclonic eddies in the east australian current system mesoscale cyclonic eddies are known to be highly productive less well known are the dynamics and productivity of smaller cyclonic eddies known as frontal eddies that form on the landward side of western boundary currents in this study we investigate the physical and biogeochemical properties of two contrasting cyclonic eddies in the east australian current eac the first murphy a mesoscale cyclonic eddy that formed at 28 s with a diameter of 160 km and high surface chlorophyll a concentrations which lived 47 days the second freddy a smaller frontal eddy 35 km diameter that formed from a shelf water billow 7 days prior to sampling at 31 5 s and was advected off the shelf along the eac front from 200m to 4000m of water both eddies were at least 1000m deep with a similar steric height anomaly we introduce and employ the method of closest approach using shipboard adcp velocities to estimate the eddy centers which reveals significant tilting through the water column we estimate rotation rates of 4 10 days and 1 9 days and rossby numbers 0 25 0 1 and 0 6 0 1 from the surface to 600m for murphy and freddy respectively high resolution altimetry measurements from the saral altika satellite provide estimates of the ageostrophic component of rotation our results show that the frontal eddy is significantly more ageostrophic energetic and productive than the mesoscale cyclone despite its small size and short life 4 weeks we suggest that frontal eddies have potential to contribute significantly to the net productivity of the tasman sea region this article is protected by copyright all rights reserved

tasman leakage in a fine resolution ocean model tasman leakage the westward flow of thermocline waters south of australia from the pacific to the indian ocean is one of the lesser studied of the inter ocean exchanges here some of the properties of the tasman leakage are inferred from lagrangian particles integrated using the three dimensional velocity fields of the 1 10 degree resolution ofes model the mean tasman leakage in this model is 4 2 sv with a standard deviation of 4 3 sv the heat flux associated with this leakage lies in the range 0 08 0 18 pw there is large variability in the tasman leakage on both sub weekly and inter annual scales but no trend over the 1983 1997 period despite the large weekly variability with peaks of more than 20 sv it appears that less than half of the tasman leakage is carried within eddies

topographically induced upwelling off eastern australia abstract a high resolution numerical study of an idealized western boundary current flow over variable topography is presented with application to the east australian current eac the results indicate that alongshelf topographic variations off australia s east coast cause the eac to accelerate over the narrowing continental shelf near cape byron this acceleration is sufficient to hinder the geostrophic adjustment in the bottom boundary layer bbl which would usually cause the eac driven bbl to shut down consequently a region of persistent high bottom stress was established off cape byron which was responsible for driving an upwelling bbl it is shown that the enhanced vertical mixing associated with a low richardson number flow beneath the eac reduced the local stratification consequently the burger number is decreased resulting in a long shutdown timescale of the bbl which enables a nearshore thermal to be established and maintained such fronts are commonly observed in the region as a p

laboratory seismic measurements an aid in the interpretation of seismic field data this contribution reports data and evidence from laboratory measurements of compressional and shear wave velocities and mineralogical microstructural and chemical analyses in crustal rocks that may provide an aid to understanding and interpreting geophysical data it is shown that the correlation of laboratory seismic data with stratigraphic field data can provide the necessary data base for constructing a seismic model of the earth s crust in a particular geological area

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

the effect of the south pacific convergence zone on the termination of el nino events and the meridional asymmetry of enso abstractduring large el nino events the westerly wind response to the eastern equatorial pacific sea surface temperature anomalies sstas shifts southward during boreal winter and early spring reaching latitudes of 5 7 s the resulting meridional asymmetry along with a related seasonal weakening of wind anomalies on the equator are key elements in the termination of strong el nino events using an intermediate complexity atmosphere model it is demonstrated that these features result from a weakening of the climatological wind speeds south of the equator toward the end of the calendar year the reduced climatological wind speeds which are associated with the seasonal intensification of the south pacific convergence zone spcz lead to anomalous boundary layer ekman pumping and a reduced surface momentum damping of the combined boundary layer lower troposphere surface wind response to el nino this allows the associated zonal wind anomalies to shift south of the equator furthermore using a linear sh