decadal changes in the south pacific western boundary current system revealed in observations and ocean state estimates observations and ocean state estimates are used to investigate the nature and mechanism of decadal variability in the east australian current eac system and south pacific subtropical gyre a 62 year record on the tasmanian continental shelf shows decadal variations of temperature and salinity as well as a long term trend which has been related to wind driven variations in the poleward extension of the eac repeat expendable bathythermograph lines spanning the last 15 years suggest that low frequency variations in the transport of the eac extension and tasman front are anticorrelated but the time series are too short to draw firm conclusions here we use two ocean state estimates spanning the past 50 years to diagnose the physical mechanisms and spatial structure of the decadal variability of the south pacific subtropical gyre the observations and state estimates paint a consistent picture of the decadal variability of the gyre and eac system strengthening of the basin wide wind stress curl drives a southward expansion of the subtropical gyre as the gyre shifts south the eac extension pathway is favored at the expense of the tasman front resulting in the observed anticorrelation of the these two major currents the results suggest that the subtropical gyre and western boundary current respond to decadal variability in basin scale wind stress curl consistent with island rule dynamics that strong decadal variability of the south pacific gyre complicates efforts to infer trends from short term records and that wind stress curl changes over the south pacific basin drive changes in the eac system that are likely to have implications for marine ecosystems and regional climate

a modeling study of the climatological current field and the trajectories of upwelled particles in the east australian current the climatological current field off the coast of new south wales australia is investigated using results from a field experiment and a diagnostic numerical modeling study in particular the flow dynamics are examined near smoky cape 308559s in the vicinity of the east australian current separation point modeled velocity fields compare favorably with observed velocity measurements that were obtained in this region during november 1998 an investigation of the role of advection in the alongshore momentum equation reveals that uvx and vvy change sign about the separation point representing a shift in the flow regime from onshore advection and southward acceleration north of the separation to seaward advection and weaker southward currents south of the separation bottom stress increases on the continental shelf downstream of the separation point coincident with high horizontal divergence throughout the region south of smoky cape the near bottom flow is characterized by a low burger number coincident with a subcritical richardson number these characteristics imply that the timescale in which bottom boundary layer shutdown occurs will be lengthened enabling a persistent flow of potentially nutrient rich water into the coastal region a series of lagrangian particle tracking experiments designed to investigate the fate of the upwelled water are presented motivated by an observed chlorophyll a maximum along the 25 25 su isopycnal water of this density is used as a proxy for nutrient enriched water it is found that upwelled water originates at depth to the north of smoky cape and at times well offshore south of smoky cape coastal recirculations are evident suggesting that upwelled water could be trapped in eddy fields adjacent to the coast and thus explaining why phytoplankton blooms are prevalent in the region south of smoky cape

newly found tunglo active fault system in the fold and thrust belt in northwestern taiwan deduced from deformed terraces and its tectonic significance we found active faults in the fold and thrust belt between tunglo town and the tachia river in northwestern taiwan the surface rupture occurred in 1999 and 1935 nearby the study area but no historical surface rupture is recorded in this area suggesting that the seismic energyhas been accumulated during the recent time deformed fluvial terraces aid in understanding late quaternary tectonics inthistectonicallyactivearea thisareacontainsnewlyidentifiedfaultsthatwegroupasthetunglofaultsystem whichformedafter the area s oldest fluvial terrace and appears at least 16km long in roughly n s orientation its progressive deformations are all recorded in associated terraces developed during the middle to late quaternary in the north the system consists of two subparallel activefaults thetunglofaultandtungloeastfault strikingn sandfacingeachotherfromoppositesidesofthenorthwardflowing hsihu river whose course may be controlled by interactions of above mentioned two active faults the northern part of the tunglo fault to the west of the river is a reverse fault with upthrown side on the west conversely the tunglo east fault to the east is also a reverse fault but with upthrown side on the east both faults are marked by a flexural scarp or eastward tilting of fluvial terraces considering a quaternary syncline lies subparallel to the east of this fault system the tunglo fault might be originated as a bending moment fault and the tunglo east fault as a flexural slip fault however they have developed as obvious reverse faults which have progressive deformation under e w compressive stress field of taiwan farther south a west facing high scarp the tunglo south fault strikes nne ssw oblique to the region s e w direction of compression probably due to the strain partitioning the tunglo southfaultgeneratesenechelon elongatedridgesandswalestoaccommodateright lateralstrike slipdisplacement otherstructures intheareaincludeeastward strikingportionofthesanyifault whichhasnoevidenceforlatequaternarysurfaceruptureonthisfault perhaps slip on this part of sanyi fault ceased when the tunglo fault system became active

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

decadal sea level variability in the south pacific in a global eddy resolving ocean model hindcast sea level variability and related oceanic changes in the south pacific from 1970 to 2003 are investigated using a hindcast simulation of an eddy resolving ocean general circulation model ogcm for the earth simulator ofes along with sea level data from tide gauges since 1970 and a satellite altimeter since 1992 the first empirical orthogonal function mode of sea level anomalies slas of ofes exhibits broad positive slas over the central and western south pacific the corresponding principal component indicates roughly stable high low and high slas separated by a rapid sea level fall in the late 1970s and sea level rise in the late 1990s consistent with tide gauge and satellite observations these decadal changes are accompanied by circulation changes of the subtropical gyre at 1000 m depth and changes of upper ocean zonal current and eddy activity around the tasman front in general agreement with previous related studies it is found that sea level variations in the tasman sea can be explained by propagation of long baroclinic rossby waves forced by wind stress curl anomalies if the impact of new zealand is taken into account the corresponding atmospheric variations are associated with decadal variability of el nino southern oscillation enso thus decadal sea level variability in the western and central south pacific in the past three and half decades and decadal enso variability are likely to be connected the sea level rise in the 1990s which attracted much attention in relation to the global warming is likely associated with the decadal cooling in the tropical pacific

on the east australian current variability encroachment and upwelling 1 observations from an intensive oceanographic field program which took place in 1998 1999 about the separation point of the east australian current eac show significant spatial and temporal variability of the eac upstream of the separation point southward flowing currents are strong with subinertial velocities of up to 130 cm s 1 in the near surface waters whereas downstream currents are highly variable in both strength 1 70 cm s 1 and direction upwelling is observed to occur through both wind driven and current driven processes with wind effects playing a lesser role by contrast the encroachment of the eac upon the coast has a profound effect on the coastal waters accelerating the southward alongshore currents and decreasing the temperature in the bottom boundary layer bbl by up to 5 degreesc as the axis of the jet moves onshore negative vorticity increases in association with an increase in nonlinear acceleration during this time bottom friction is increased the burger number is reduced and the bbl shut down time lengthens the observed upwelling is attributed to enhanced onshore ekman pumping through the bbl resulting from increased bottom stress as the southerly flow accelerates when the eac encroaches across the continental shelf

the southwest pacific ocean circulation and climate experiment spice the southwest pacific ocean circulation and climate experiment spice is an international research program under the auspices of clivar the key objectives are to understand the southwest pacific ocean circulation and the south pacific convergence zone spcz dynamics as well as their influence on regional and basin scale climate patterns south pacific thermocline waters are transported in the westward flowing south equatorial current sec toward australia and papua new guinea on its way the sec encounters the numerous islands and straits of the southwest pacific and forms boundary currents and jets that eventually redistribute water to the equator and high latitudes the transit in the coral solomon and tasman seas is of great importance to the climate system because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate the el nino southern oscillation while the southward transports influence the climate and biodiversity in the tasman sea after 7 years of substantial in situ oceanic observational and modeling efforts our understanding of the region has much improved we have a refined description of the spcz behavior boundary currents pathways and water mass transformation including the previously undocumented solomon sea the transports are large and vary substantially in a counter intuitive way with asymmetries and gating effects that depend on time scales this paper provides a review of recent advancements and discusses our current knowledge gaps and important emerging research directions

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

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

variation in sea temperature and the east australian current in the solitary islands region between 2001 2008 abstract improved understanding of the east australian current eac and sea temperature patterns within the solitary islands region of northern new south wales an area where tropical and temperate faunas overlap is an essential step in explaining cross shelf gradients in biotic patterns sea temperature at 10 m was logged using thermistors at seven stations every 30 minutes between january 2001 and december 2008 stations were replicated in three distance from shore categories 6 km from the coast corresponding with predominant assemblage patterns of reef fish daily monthly seasonal and yearly sea temperature patterns were compared between and within stations and distance from shore categories sst images were examined to determine the role of the eac in producing short period 2 to 4 days temperature anomalies sea temperatures ranged between 16 6 27 5 c and were highest offshore and lowest inshore offshore sites experienced average temperatures 1 c higher than nearshore sites over the 8 year study there was considerable variation in sea temperature between years with 2002 and 2006 being the warmest and 2007 the coolest these patterns correspond with strong inter annual variability of the eac at the scale of the solitary islands region the eac influenced shelf waters most strongly during late spring summer when temperatures were also most variable over the smallest temporal scales hours days short period anomalies between and within stations could largely be explained by variable encroachment of the eac across the shelf and or colder intrusions of water forming adjacent to the coastline previous assumptions that the eac strongly influences gradients in the distribution of tropical species in this nearshore region are strongly supported

upper crustal folding of the 2013 lushan earthquake area in southern longmen shan china insights from late quaternary fluvial terraces abstract a thrust earthquake of mw6 6 occurred on april 20 2013 near lushan county in the southern longmen shan at the east margin of tibetan plateau this earthquake did not produce a surface rupture zone and the late quaternary activities of the outcropped faults in the earthquake area were not obvious which increased the difficulty of studying the seismogenic structure this article took as the research target the middle reach of the qingyijiang river which traverses the earthquake area by surveying correlating the fluvial terraces studied quantitatively the late quaternary tectonic deformation and further discussed the seismotectonics the longitudinal profile of river terraces along the middle reach of the qingyijiang river reveals that the principal deformation style in the late quaternary was anticline type folding the folding is a typical fault bend fold involving the basement which is controlled by the newest flat ramp flat structure possibly formed in the pliocene or the early pleistocene across the fold the average shortening rate in the late quaternary is 0 6 1 3 mm yr about one third of the crustal shortening rate by gps data across the longmen shan fold and thrust belt and its foreland the foreland thin skinned structure developed in the cretaceous to paleogene strata in the earthquake area was passively involved into the fault bend folding in the late quaternary which commend the thrust ramp developing in a piggyback style the newest ramp appears to have controlled the rupture and the surface deformation of the 2013 lushan earthquake in the process of thrust sheet sliding toward foreland along the flat ramp flat detachment the ramp acts as a locking structure where earthquake ruptures the coseismic surface deformation seems to be passive folding of the thrust sheet climbing the ramp

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

climate and vegetation dynamics in the tundra and forest zone during the late glacial and holocene abstract analysis of palynological successions has enabled reconstruction of climate variations throughout the late glacial and holocene in the tundra and forest zones of northern eurasia statistical analysis allows estimation of mean annual precipitation and mean annual and july temperatures based on palynological assemblages thus the dynamic relationships between climate and vegetation changes can be established throughout the late glacial and holocene climate fluctuations were more dramatic in eastern europe than in siberia primarily as a result of the influence of westerly air masses in contrast the autochthonous climate of siberia dominated by local air masses was less prone to influence from climate changes elsewhere in the northern hemisphere and shows only an attenuated younger dryas signal mid holocene warming characterizes all of northern eurasia although the regions of siberia most influenced by continental climates show less pronounced cooling during the later holocene sharp changes between summer monsoonal and winter anti cyclonic regimes characterize the pacific maritime region

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

enso to multi decadal time scale changes in east australian current transports and fort denison sea level oceanic rossby waves as the connecting mechanism the connection between east australian current eac transport variability and australia s east coast sea level has received little treatment in the literature this is due in part to the complex interacting physical processes operating in the coastal zone combined with the sparsity of observations available to improve our understanding of these possible connections this study demonstrates a statistically significant at the 490 level relationship between interannual to decadal time scale variations in observed estimates of the eac transport changes and east coast sea level measured at the high quality long record fort denison tide gauge in sydney harbour australia 3315101800s 15111303200e we further demonstrate using a linear reduced gravity ocean model that enso to decadal time scale variations and the ocean adjusted multi decadal trend approx 1 cm decade in observed sea level at fort denison are strongly connected to modulations of eac transports by incoming westward propagating oceanic rossby waves we show that eac transport and fort denison sea level vary in a manner expected from both tasman sea generated rossby waves which account for the interannual and multi annual variability and remotely forced from east of new zealand rossby wave connections through the mid latitudes accounting for the ocean adjusted multi decadal trend observed at the new south wales coast with the regional tasman sea forcing explaining the greatest overall proportion of eac transport and sea level variances

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

a synthesis of the geologic evolution of taiwan abstract the island arc of taiwan is composed of cenozoic geosynclinal sediments more than 10 000 m thick lying on a pre tertiary metamorphic basement pleistocene to miocene andesitic islands surround the main island and are related mostly to arc magmatism the penghu island group in the taiwan strait is covered with pleistocene flood basalt neogene shallow marine clastic sediments are exposed mainly in the western foothills with pleistocene andesitic extrusives at the northern tip and the northeastern offshore islands a thick sequence of paleogene to miocene argillitic to slaty metaclastic rocks underlies the western central range and forms the immediate sedimentary cover on the pre tertiary metamorphic complex to the east which represents an older mesozoic arc trench system the coastal range in eastern taiwan is a neogene andesitic magmatic arc including also a large variety of volcaniclastic and turbiditic sediments cenozoic taiwan is the site of arc continent collision where the luzon arc on the philippine sea plate overrides the chinese continental margin on the eurasian plate east and northeast of taiwan the polarity of subduction changes whereby the oceanic philippine sea plate is subducting beneath the ryukyu arc system on the eurasian plate continent arc collision in taiwan island is anomalous and may occur in a broad belt of deformation rather than along a well defined plate boundary or subduction zone

eddy momentum flux and its contribution to the southern ocean momentum balance a large amount of momentum is transferred to the southern ocean by strong westerly winds analytical and numerical models have suggested that transient eddies may be important in transporting this momentum away from the region of wind forcing either horizontally1or vertically downwards where it is balanced by bottom topographic drag2 5 there are however few long term in situ observations of horizontal eddy momentum flux6 8 and no large scale measurements of vertical eddy fluxes to test these models as a result the momentum balance of the antarctic circumpolar current acc remains uncertain and the role of eddies controversial here we use geosat satellite altimeter data to resolve directional eddy kinetic energy and horizontal eddy momentum flux in the acc on fine spatial and temporal scales the complex spatial distribution of surface eddy momentum flux is strongly influenced by bottom topography the horizontal eddy momentum flux tends generally to concentrate the mean flow although some regions of divergence are observed our results show that the zonally averaged horizontal eddy momentum flux from transient eddies is an order of magnitude too small and in the wrong direction to directly balance the eastward momentum input from wind1

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

observed bottom boundary layer transport and uplift on the continental shelf adjacent to a western boundary current western boundary currents strongly influence the dynamics on the adjacent continental shelf and in particular the cross shelf transport and uplift through the bottom boundary layer four years of moored in situ observations on the narrow southeastern australian shelf in water depths of between 65 and 140 m were used to investigate bottom cross shelf transport both upstream 30 s and downstream 34 s of the separation zone of the east australian current eac bottom transport was estimated and assessed against ekman theory showing consistent results for a number of different formulations of the boundary layer thickness net bottom cross shelf transport was onshore at all locations ekman theory indicates that up to 64 of the transport variability is driven by the along shelf bottom stress onshore transport in the bottom boundary layer was more intense and frequent upstream than downstream occurring 64 of the time at 30 s wind driven surface ekman transport estimates did not balance the bottom cross shelf flow at both locations strong variability was found in bottom water transport at periods of approximately 90 100 days this corresponds with periodicity in eac fluctuations and eddy shedding as evidenced from altimeter observations highlighting the eac as a driver of variability in the continental shelf waters ocean glider and hf radar observations were used to identify the bio physical response to an eac encroachment event resulting in a strong onshore bottom flow the uplift of cold slope water and elevated coastal chlorophyll concentrations

cross shelf dynamics in a western boundary current regime implications for upwelling abstractthe cross shelf dynamics up and downstream of the separation of the south pacific ocean s western boundary current wbc are studied using two years of high resolution velocity and temperature measurements from mooring arrays the shelf circulation is dominated by the east australian current eac and its eddy field with mean poleward depth integrated magnitudes on the shelf break of 0 35 and 0 15 m s 1 up and downstream of the separation point respectively the high cross shelf variability is analyzed though a momentum budget showing a dominant geostrophic balance at both locations among the secondary midshelf terms the bottom stress influence is higher upstream of the separation point while the wind stress is dominant downstream this study investigates the response of the velocity and temperature cross shelf structure to both wind and eac intrusions despite the deep water up to 140 m the response to a dominant along shelf wind stress forcing is a classic two layer ekman structure du

closing the time varying mass and heat budgets for large ocean areas the tasman box abstract the role of oceanic advection in seasonal to interannual balances of mass and heat is studied using a 12 yr time series of quarterly eddy resolving expendable bathythermograph xbt surveys around the perimeter of a region the authors call the tasman box in the southwestern pacific the region contains the south pacific s subtropical western boundary current system and associated strong mesoscale variability mean geostrophic transport in the warm upper ocean temperature greater than 12 c is about 3 8 sv 1 sv 106 m3 s 1 southward into the box across the brisbane australia fiji northern edge net outflows are 3 3 sv eastward across the auckland new zealand fiji edge and 2 7 sv southward across sydney australia wellington new zealand mean ekman convergence of 2 2 sv closes the mass budget net water mass conversions in the upper ocean consist of inflow of waters averaging about 26 c and 35 4 psu balanced by outflow at about 18 c and 35 7 psu and reflect the net evaporation and heat los

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

enso and short term variability of the south equatorial current entering the coral sea abstracthistorical section data extending to 1985 are used to estimate the interannual variability of transport entering the coral sea between new caledonia and the solomon islands typical magnitudes of this variability are 5 8 sv sv 106 m3 s 1 in the 0 400 m layer relative to 400 m and 8 12 sv in the 0 2000 m layer relative to 2000 m on a mean of close to 30 sv relative to 2000 m transport increases a few months after an el nino event and decreases following a la nina interannual transport variability is well simulated by a reduced gravity long rossby wave model vigorous westward propagating mesoscale eddies can yield substantial aliasing on individual ship or glider surveys since transport variability is surface intensified and well correlated with satellite derived surface geostrophic currents a simple index of south equatorial current transport based on satellite altimetry is developed

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

river terrace development in response to folding above active wedge thrusts in houli central taiwan abstract folding at the leading edge of the western taiwan thrust belt is well preserved by a flight of fluvial terraces at houli strain in this region is driven by slip on the north trending changhua and sanyi blind wedge thrusts and occurs at the boundary between the miaoli and taichung neotectonic domains located respectively to the north and south in the past century two large historical earthquakes occurred in these two domains and produced surface ruptures within or close to the study area indicating houli is not only tectonically active but also critical for understanding the interaction between the neighboring active systems although abundant river terraces and their deformation by active structures have long been well known in the area a kinematical model for this region has not yet been proposed we have therefore remapped the geomorphic features using the 40 m dem and aerial photos to identify often subtle structural features in order to separate the effects of folding interference produced by different active structural systems besides the tuntzuchiao fault ttcf which generated the 1935 earthquake two other active regional scale structural systems have been reported in houli area the tiechanshan tcs anticline and the changhua fault chf our results demonstrate a number of tectonic scarps and warped surfaces in association with the chf and its coupled back thrust indicating that the chf system is active in contrast the flight of fluvial terraces distributed in the middle of the study area cannot be related to the growth of the tcs anticline instead terraces here record growth of another smaller and previously unknown anticline yuehmei tentatively named in this study and shortened to ym in the text although it has developed parallel to the tcs anticline relevant seismic profiles show the ym anticline as a local drag fold attached to the southern limb of the tcs anticline and restricted in the houli area based on the above observation the tcs anticline can be interpreted as becoming less active where strain is instead transferred to the more rapidly uplifting ym anticline this structural switch may be the result of interference between the newly developed southern taichung system and the preexisting tcs anticline

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

aspects of the mean wintertime circulation along australia s southern shelves numerical studies abstract a high resolution numerical model is used to study the mean wintertime shelf slope circulation between the gulfs of south australia and the west coast of tasmania the mean downwelling favorable winds for the region result in a continuous eastward coastal current cc extending from cape leeuwin to the eastern coast of tasmania the magnitude of the cc is generally largest over the shelf break has speeds of more than 40 cm s 1 transport 2 4 sv sv 106 m3 s 1 and is generally in good agreement with observations the relative importance of the leeuwin current zonal winds and density gradients to the shelf circulation is established within bass strait the eastward circulation is in good agreement with observations and simple models show that about 30 of the transport arises from local winds and the remainder from the cc the total transport through the strait 0 95 sv is shown to be controlled by sea level on the east coast of tasmania a current of up to 10 cm s 1 is also found to flow

seasonal circulation around tasmania an interface between eastern and western boundary dynamics 1 the seasonal circulation connecting the pacific and indian oceans around tasmania is documented using seasonal maps from satellite altimetry and sea surface temperature sst and in situ mean fields from a high resolution climatology of the region commonwealth scientific and industrial research organisation csiro atlas of regional seas cars in general the surface variability displays a very different character off the east and west coasts off the east coast the variability is generated externally being dominated by the western boundary dynamics of the east australian current eac in the west it is weaker and arises from the seasonal rise and fall of the coastal sea level which is due to the seasonal reversing wind patterns a high variability tongue associated with the eac stretches poleward off the east coast tracing out a waveguide between the major topographic structures it has a broad peak in power between 180 and 365 days 0 08 m which is a surface height expression of the energetic mesoscale eddy activity associated with the eac distinctive summer and winter patterns of the surface circulation are described which are influenced by the eac and the zeehan current zc respectively on the east coast in summer january march there is a poleward advection of warm saline water forced by an episodic coastal boundary flow the cross shelf pressure gradient driving this flow is formed from the difference between the seasonal changes in coastal sea level and the offshore eddies there is a seasonal reversal of this flow in winter with cool fresh modified subantarctic surface waters drawn up from the south off the west coast the zeehan current operates 180 out of phase with the eac it is strongest in winter when it projects warm relatively saline waters down the western tasmania coast and around the southern tip of tasmania there is a sharp division between the eac and zc influence adjacent to the tasman peninsula off southeast tasmania

geomorphic evidence for prior earthquakes lessons from the 1999 chichi earthquake in central taiwan the september 21 1999 mw 7 6 chichi earthquake destroyed several thousand buildings and caused more than 2000 fatalities in central taiwan the earthquake occurred along the chelungpu fault a thrust fault on the western flank of the taiwan fold and thrust belt the surface rupture was more than 90 km long and vertical displacements ranged from 3 to 8 m although pre existing scarps were identified along the chelungpu fault the fault had previously been categorized as a less important active fault owing to the lack of geochronologic evidence and the failure to recognize fault related geomorphic features identifying geomorphic features at active faults in taiwan will permit the delineation of future sur face ruptures and the determination of past magnitudes of past earthquakes thus contributing to hazard assessment

pleistocene alluvial deposits dating along frontal thrust of changhua fault in western taiwan the cosmic ray exposure point of view abstract to tackle the history of active thrusts it is necessary to open the observation window on time scales on the order of 104 105 years by studying the surface morphologies resulting from their activities because fluvial systems are particularly sensitive to recent environmental changes geomorphic features such as alluvial terraces are frequently used as markers to gauge tectonic deformation together with the measurement of cumulative displacements the chronological framework of emplacement and abandonment of these geomorphic markers is thus fundamental to determine long term fault slip rates in taiwan the geomorphic features associated with fault activity have been studied in detail with a high level of resolution however the use of deformed and partially preserved alluvial terraces is often hampered by the absence of well documented ages the purpose of this paper is two fold first we take the opportunity to review the chronological constraints that have been published in taiwan so far second we present how the cosmogenic dating method in situ produced 10be can be used to constraint the chronological framework of alluvial deposits over a pleistocene time scale thanks to a comparison of our cosmogenic derived ages with existing data we present a consistent regional chronological framework for the pakua tadu area along the changhua fault one of the most active frontal thrusts in the western foothills of the taiwan mountain belt we also discuss its relationships with global eustatism and its tectonic implications for the timing of propagation of the deformation front during the last 450 kyr

neotectonic architecture of taiwan and its implications for future large earthquakes the disastrous effects of the 1999 chi chi earthquake in taiwan demonstrated an urgent need for better knowledge of the island s potential earthquake sources toward this end we have prepared a neotectonic map of taiwan the map and related cross sections are based upon structural and geomorphic expression of active faults and folds both in the field and on shaded relief maps prepared from a 40 m resolution digital elevation model augmented by geodetic and seismologic data the active tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the eurasian continental margin have created two neotectonic belts in taiwan in the southern part of the orogen both belts are in the final stage of consuming oceanic crust collision and suturing occur in the middle part of both belts and postcollisional collapse and extension dominate the island s northern and northeastern flanks both belts consist of several distinct neotectonic domains seven domains kaoping chiayi taichung miaoli hsinchu ilan and taipei constitute the western belt and four domains lutao lanyu taitung hualien and ryukyu make up the eastern belt each domain is defined by a distinct suite of active structures for example the chelungpu fault source of the 1999 earthquake and its western neighbor the changhua fault are the principal components of the taichung domain whereas both its neighboring domains the chiayi and miaoli domains are dominated by major blind faults in most of the domains the size of the principal active fault is large enough to produce future earthquakes with magnitudes in the mid 7 values