a 6 year record of baroclinic transport variability of the antarctic circumpolar current at 140 e derived from expendable bathythermograph and altimeter measurements 1 repeat hydrographic sections across the antarctic circumpolar current are used to derive an empirical relationship between upper ocean temperature and the baroclinic transport stream function cross validation shows this relationship can be used to infer baroclinic transport above and relative to 2500 dbar from temperature measurements with an error of a few per cent the mean transport distribution derived from 31 austral summer expendable bathythermograph xbt sections over a 6 year period consists of westward flow immediately south of tasmania a broad band of strong eastward flow between 50 and 55 s and three cores of eastward flow south of 55 s by defining a second empirical relationship between surface dynamic height and cumulative transport a continuous time series of baroclinic transport is derived from altimeter measurements of sea surface height transports derived from altimetry in this way agree well with simultaneous in situ estimates root mean square error in net transport is 4 106 m3 s 1 suggesting sea level anomalies largely reflect baroclinic changes above 2500 dbar the 10 day sampling of the altimeter transport time series shows the irregular xbt sampling aliases variability at unresolved timescales the standard deviation of net transport above and relative to 2500 m is 4 3 106 m3 s 1 the variability in net transport is largest 2 7 106 m3 s 1 in the quasi annual band periods of 4 months to 1 5 years slightly smaller 2 3 106 m3 s 1 in the mesoscale band 1 5 years 1 5 106 m3 s 1 changes in transport are correlated with local changes in both wind stress and wind stress curl in the quasi annual and interannual bands but the transport time series is too short to draw significant conclusions

winter time dissolved iron and nutrient distributions in the subantarctic zone from 40 52s 155 160e 1 in hnlc oceanic regions iron fe controls phytoplankton productivity yet large gaps remain in our understanding of iron s biogeochemical cycle here we present the first comprehensive winter dataset for dissolved fe dfe and nitrate no3 distributions 0 1000 m depth between 40s 52s which transects the subantarctic zone saz west of new zealand surface concentrations 0 2 nmol fe kg 1 were conspicuously low i e probably biologically limiting even at winter reserve levels at frontal zones between 43s subtropical front and 51s subantarctic front a fivefold range in fe no3 molar ratios was observed along the transect with subtropical waters where blooms occur having the highest ratios in subsurface waters the major wintertime supply of dfe in the saz is from ekman advection of waters from the south but calculated source water dfe is 0 2 nmol fe kg 1 suggesting that mixed layer dfe concentration is controlled by how long these southern waters remain at the surface 3 years

high archean climatic temperature inferred from oxygen isotope geochemistry of cherts in the 3 5 ga swaziland supergroup south africa new and compiled oxygen isotope data combined with the results of geological and sedimentological studies demonstrate that enclaves of synsedimentary to very early diagenetic cherts are widely preserved in the 3 5 3 2 ga swaziland supergroup barberton greenstone belt south africa the low 1 8 o values of these cherts indicate extremely high ocean temperatures of 55 85 c previously the large depletion in 1 8 o shown by all barberton cherts relative to their phanerozoic counterparts has been attributed to low 1 8 o in archean oceans chert formation during late diagenesis wholesale loss of 1 8 o during alteration and or regional silicification of sediments around hot springs these alternative explanations are not compatible with the new results cherts in the onverwacht group display an isotopic stratigraphy that is inversely repeated in conglomerates in the overlying fig tree and moodies groups demonstrating that the chert 8 0 o values were fixed prior to archean uplift and erosion which started at 3 26 ga the maximum 1 8 o value in barberton cherts 22 is lower than the minimum values 23 in phanerozoic bedded cherts precluding late diagenesis as the explanation of the overall low 1 8 o values regional metamorphic hydrothermal or long term resetting of original 1 8 o values is also precluded by preservation of 1 8 o values across different metamorphic grades and by systematic 1 8 o differences among interbedded chert types stratigraphic units and conglomerate clasts the 7 1 8 o variation of these archean cherts is similar to that of phanerozoic deep sea cherts formed when opal converted to microquartz during burial but the actual archean values are 10 lower marine opal was apparently converted to microquartz during burial to depths of 1 km cherts with 1 8 o 15 reflect conversion during deepest burial or in local areas of enhanced geothermal gradient and or hydrothermal activity cherts with higher 1 8 o values formed during early diagenesis and indicate an extremely hot archean ocean and surface environment

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

geochemistry of a silicified felsic volcaniclastic suite from the early archaean panorama formation pilbara block western australia an evaluation of depositional and post depositional processes with special emphasis on the rare earth elements abstract many elements in a suite of pervasively silicified dacitic volcaniclastic and volcanic rocks from the early archaean panorama formation warrawoona group western australia were strongly depleted or enriched relative to those in equivalent unaltered units during widespread post depositional metasomatism the present compositions of the altered rocks are dominated by al 2 o 3 k 2 o and sio 2 and lie on or close to a quartz sericite mixing line the al contents were probably inherited from the original dacitic rocks while si some k and possibly rb may have been introduced during metasomatism the elements mg ca na and to a lesser extent fe mn and sr have been depleted relative to al during alteration whereas silica has been greatly enriched the high and variable ba concentrations suggest that ba like si was introduced during silicification the ree and th were relatively immobile during alteration and were diluted during silicification in the same proportion as al most of the rocks represent detrital sand and silt sized felsic tephra debris eroded from felsic volcanic rocks or ash fall deposits that underwent a short interval of transport and deposition dominated by physical rather than chemical processes a few siltstones contain clay minerals that probably formed by the chemical weathering of warrawoona group basalts the siltstones have lower th and la concentrations lower la lu ratios and higher sc and cr concentrations than felsic rocks in the suite regional alteration pervasively silicified the original sediments shortly after deposition the replacement mineral assemblage indicates a maximum temperature for hydrothermal alteration of about 350 c because of the lack of chemical weathering and the low temperature of post depositional alteration ree abundances in volcaniclastic rocks of the panorama formation reflect their felsic volcanic provenance and are interpreted to have preserved a relict magmatic signature the lack of a negative eu anomaly and high la lu ratio chondrite normalized ratio is 7 to 39 suggest that magmas of the panorama formation formed by direct melting of an eclogite residue without subsequent crystallization of feldspar during the commencement of cratonization of the pilbara block this origin differs from the origin of some other silicic volcanic rocks of the duffer formation representing earlier felsic volcanic activity of the warrawoona group that were produced by fractional crystallization from basaltic parents this suggests a polygenetic origin for felsic magmas of the warrawoona group

tracing fluid pathways in fossil hydrothermal systems with near infrared spectroscopy we present a new method to detect and reconstruct fluid pathways in fossil hydrothermal systems that is based on systematic study of white micas in hydrothermally altered rock using near infrared spectroscopy this method developed in an early archean volcanic sequence in the panorama district in western australia uses new near infrared spectroscopic data and published geological and geochemical data of fossil submarine hydrothermal systems in the area analysis of new near infrared spectroscopic data revealed that the abundance of white mica and its al content in altered volcanic rock vary systematically along fossil fluid pathways from zones of low temperature recharge to zones of high temperature discharge as a function of hydrothermal fluid chemistry temperature of alteration coexisting minerals and composition of volcanic host rock the abundance of white mica relative to that of chlorite and the al content of white micas can be used to discriminate among the hydrothermal alteration facies along these fluid pathways which permits detection and reconstruction of fossil fluid pathways

a northern boundary current along australia s southern shelves the flinders current 1 south of australia the monthly mean wind stress curl is positive during both summer and winter and leads to ekman pumping and downwelling throughout the region sverdrup dynamics indicates that this downwelling should lead to a northward transport of around 5 10 sv 1 sv 10 m3 s 1 classical arguments for western boundary currents are adapted to show that this transport should be deflected into an upwelling favorable boundary current that flows from east to west along australia s southern shelves the flinders current support for this proposition is obtained from results of the ocean circulation and climate advanced modelling project occam sverdrup transports and limited observations for the region in addition the occam results show that the northward transport leads to upwelling at depths below 400 m and that the flinders current 1 intensifies from victoria to western australia transport 8 sv with speeds up to 15 cm s 1 2 can extend from the surface to depths of 800 m and 3 is found during both summer and winter during winter the winds are downwelling favorable and lead to a coastal current that flows from west to east and opposes the flinders current further support for the origin and nature of the flinders current is obtained from simple numerical experiments made using a rectangular domain and idealized representations of the summer and winter wind stress

tree ring reconstructions of cool season temperature for far southeastern australia 1731 2007 at the global scale reconstructions of cool season temperature over past centuries are relatively rare here we present 277 year reconstructions of cool season july october temperatures for southern australia based on three different data sets a spatial field reconstruction based on highly resolved temperature data from the australian water availability product data reconstructions for the four southeast australian states based on the berkeley earth mean temperature data for each state and reconstructions for individual stations in southeastern australia from the australian bureau of meteorology s australian climate observations reference network surface air temperature data our reconstructions typically capture 25 50 of the variation over the late twentieth century calibration period and are strongest for the southern state of tasmania and the southeastern part of mainland australia all three use tasmanian tree rings sensitive to cool season temperatures and display similar variability in the context of our reconstructions the persistent warming in the observed record since 1950 is unprecedented while the low frequency variability of winter temperatures is generally in step with that in summer december february temperatures high frequency variability is not illustrating the need for seasonal reconstructions to help improve understanding of variability in inter seasonal dynamics and the historical importance of this on the environment the reconstructions covary with changes in the southern annular mode and may be useful for future reconstructions of this phenomenon

effects of turbulence on the transport of individual particles as bedload in a gravel bed river this study investigates the association between mean and turbulent flow variables and the movement of individual particles in a gravel bed river the experimental design implemented in the eaton north river quebec canada is based on the simultaneous observations at a high temporal resolution of both particle movements as bedload using an underwater video camera and of the streamwise and vertical flow velocity components using a vertical array of three electromagnetic current meters ecms the frequency and distance of displacement of particles larger than 20 mm that were sliding or rolling on the bed were measured from a 10 minutes long film mean and turbulent flow properties obtained for periods without sediment transport are compared to those when particles were sliding and rolling when particles are sliding weak differences are present for the mean streamwise velocity and normal vertical stresses instantaneous reynolds shear stresses are significantly lower for sliding events which was not expected but could be explained by the important dominance of quadrant 3 events inward interactions when particles are rolling only the vertical normal stresses show a weak difference from those observed in the absence of transport but they tend to occur when quadrant 2 ejections dominate the flow field for both sliding and rolling particles vertical and or streamwise fluid accelerations show high magnitude values when compared to periods without transport for sliding particles streamwise acceleration is mostly negative and combines most of the time with a positive vertical acceleration for rolling particles streamwise and vertical acceleration are predominantly of opposite sign these results suggest that fluid acceleration or deceleration in the streamwise and vertical directions is affecting the pressure field around particles in this study fluid acceleration seems to play a more important role than reynolds shear stress or normal stresses for bedload movements copyright 2010 john wiley sons ltd

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

characterizing the semidiurnal internal tide off tasmania using glider data the spatial structure of the semidiurnal internal tide in the vicinity of tasmania is characterized using temperature and salinity data from seaglider and slocum glider deployments wavelet analysis of isopycnal displacements measured by the gliders was used to isolate the semidiurnal internal tide with a solid signal observed both to the east and to the south of tasmania the signal south of tasmania was attributed to local forcing while that to the east of tasmania was found to have propagated from the south east to the north west a result which supports previous studies indicating the presence of an internal tidal beam originating over the macquarie ridge south of new zealand displacement amplitudes were observed to be amplified in the vicinity of the continental slope with the incoming tidal beam shown to be both reflected and scattered on the continental slope and shelf and energy transferred to higher modes

volcanic degassing hydrothermal circulation and the flourishing of early life on earth a review of the evidence from c 3490 3240 ma rocks of the pilbara supergroup pilbara craton western australia abstract new data gathered during mapping of c 3490 3240 ma rocks of the pilbara supergroup in the pilbara craton show that most bedded chert units originated as epiclastic and evaporative sedimentary rocks that were silicified by repeated pulses of hydrothermal fluids that circulated through the footwall basalts during hiatuses in volcanism for most cherts fossil hydrothermal fluid pathways are preserved as silica barite fe bearing veins that cut through the footwall and up to the level of individual bedded chert units but not above indicating the contemporaneity of hydrothermal silica veining and bedded chert deposition at the end of volcanic eruptive events silica barite fe bearing vein swarms are accompanied by extensive hydrothermal alteration of the footwall to the bedded chert units and occurred under alternating high sulphidation and low sulphidation conditions these veins provided pathways to the surface for elements leached from the footwall e g si ba fe and volcanogenic emissions from underlying felsic magma chambers e g co 2 h 2 s hs so 2 stratigraphic evidence of shallowing upward and subsequent deepening associated with the deposition of warrawoona group cherts is interpreted to relate to the emplacement of subvolcanic laccoliths and subsequent eruption and or degassing of these magmas heat from these intrusions drove episodes of hydrothermal circulation listric normal faulting during caldera collapse produced basins with restricted circulation of seawater eruption of volcanogenic emissions into these restricted basins formed brine pools with concentration of the volcanogenic components thereby providing habitats suitable for early life forms fossil stromatolites from two distinct stratigraphic units in the north pole dome grew in shallow water conditions but in two very different geological settings with different morphologies stratiform and domical stromatolites in the stratigraphically lower c 3490 ma dresser formation of the warrawoona group are intimately associated with barite and chert precipitates from hydrothermal vents suggesting that component microbes may have been chemoautotrophic hyperthermophiles evidence of shallow water to periodically exposed conditions active growth faulting and soft sediment deformation indicates that the volcanogenic emissions were erupted into a shallow water tectonically active caldera and concentrated therein to produce an extreme habitat for early life widespread conical and pseudocolumnar stromatolites in the c 3400 ma strelley pool chert at the base of the unconformably overlying kelly group occur in shallow marine platform carbonates silicification was the result of later hydrothermal circulation driven by heat from the overlying newly erupted euro basalt the markedly different morphology and geological setting of these only slightly younger stromatolites compared with the dresser formation suggests a diversity of microbial life on early earth the biogenicity of putative microfossils from this and younger hydrothermal silica veins in the warrawoona group remains controversial and requires further detailed study

constraints on the age of the warrawoona group eastern pilbara block western australia abstract zircons from mafic and felsic volcanic rocks in the type area of the warrawoona group the basal archaean greenstone succession of the eastern pilbara block have been dated precisely using the ion microprobe shrimp the results allow two alternative time frames for the duration of the warrawoona group dependent on how the dated zircons are considered to relate to the volcanic rocks our favoured interpretation requires a hiatus of 135 5 ma between the duffer formation at 3 46 ga and the overlying felsic volcanic rocks of the wyman formation and a hydrothermal or later magmatic origin for zircons of age 3 33 ga within one duffer formation sample and the underlying metabasalts the alternative time frame requires a short time for deposition of the entire group less than 15 ma at 3 33 ga and a xenocrystic origin for the 3 46 ga zircons of the duffer formation outside the type area of the warrawoona group the age of an intrusive granodiorite requires that greenstones be older than 3 43 ga and the group formed over an interval of 120 ma visibly different zircons within one of the duffer formation samples were found to be palaeozoic in age and presumably constitute hydrothermal growth of new zircon within the rock at low temperature similar zircons were found within samples from other rock units but with a spread of proterozoic ages

distribution abundance and seasonal flux of pteropods in the sub antarctic zone pteropods were identified from epipelagic net and trawl samples in the sub antarctic zone during the 2007 mid summer january 17 february 20 sub antarctic zone sensitivity to environmental change saz sense voyage as well as in a moored sediment trap in the same region overall pteropod densities during saz sense were lower than those reported for higher latitude southern ocean waters the four major contributors to the sub antarctic zone pteropod community during the saz sense voyage clio pyramidata forma antarctica clio recurva limacina helicina antarctica and limacina retroversa australis accounted for 93 of all pteropods observed the distribution of the two dominant pteropods collected in the sub antarctic zone l retroversa australis and c pyramidata forma antarctica is strongly related to latitude and depth l retroversa australis is typical of cold southern 50 54 s polar waters and c pyramidata forma antarctica is typical of shallow top 20 m sub antarctic zone waters a moored sediment trap deployed to 2100 m at 47 s 141 e in 2003 04 showed the pteropod flux in the sub antarctic zone had late spring and mid summer peaks the diversity abundance and distribution of pteropods collected during saz sense provide a timely benchmark against which to monitor future changes in saz ocean pteropod communities particularly in light of predictions of declining aragonite saturation in the southern ocean by the end of the century

carbon isotopes and petrography of kerogens in 3 5 ga hydrothermal silica dikes in the north pole area western australia more than 600 specimens of 3 5 ga old hydrothermal silica dikes from the north pole area pilbara craton western australia have been studied petrographically the kerogens in 44 samples have been analyzed isotopically c and n and chemically c n and h the silica dikes are composed mainly of fine grained silica modal abundance 97 and are classified into two types by minor mineral assemblages b black type and g gray type the b type silica dikes contain kerogen 0 37 to 6 72 mgc g average 2 44 mgc g n 21 and disseminated sulfides dominantly pyrite and fe poor sphalerite in some cases carbonate and apatite are also present their silica dominated and sulfide poor mineral assemblages suggest precipitation from low temperature reducing hydrothermal fluid likely 100 200 c on the other hand the g type silica dikes are sulfide free and concentrations of kerogen are relatively low 0 05 to 0 41 mgc g average 0 17 mgc g n 13 they typically contain fe oxide mainly hematite which commonly replaces cubic pyrite and rhombic carbonate some g types occur along secondary quartz veins these textures indicate that the g type silica dikes were formed by postdepositional metasomatism oxidation of the b types and that the b types probably possess premetasomatic signatures the 13c values of kerogen in the b types are 38 1 to 33 1 average 35 9 n 21 which are 4 lower than those of the g types 34 5 to 30 0 average 32 2 n 19 and 6 lower than bedded chert 31 2 to 29 4 average 30 5 n 4 this indicates the preferential loss of 12c during the metasomatism estimated fractionation factor 0 9985 considering the metasomatic effect on carbon isotopes with probably minor diagenetic and metamorphic overprints we conclude that the original 13c values of the kerogen in the silica dikes would have been heterogeneous 5 and at least some material had initial 13c values of 38 the inferred 13c depletions of organic carbon could have been produced by anaerobic chemoautotrophs such as methanogen but not by aerobic photoautotrophs this is consistent with the estimated physical and chemical condition of the hydrothermal fluid which was probably habitable for anaerobic and thermophilic hyperthermophilic chemoautotrophs alternatively the organic matter may have been possibly produced by abiological reaction such as fischer tropsch type ftt synthesis under the hydrothermal condition however the estimated condition is inconsistent with the presence of the effective catalysts for the ftt reaction i e fe ni alloy magnetite and hematite these lines of evidence suggest the possible existence of biosphere in the 3 5 ga sub seafloor hydrothermal system

radiocarbon evidence for mid late holocene changes in southwest pacific ocean circulation variability in the southwest sw pacific ocean circulation is influenced by the changes in the south pacific subtropical gyre and its western boundary current the east australian current eac the eac plays a significant role in transporting warm well ventilated nutrient poor waters to more temperate higher latitudes recent climate changes associated with eac intensification have led to anomalous warming in the south tasman with implications for marine ecosystems and environment a clear understanding of the significance of these changes requires knowledge of past natural variability here we have reconstructed a 4500 year record of regional sea surface radiocarbon reservoir ages r and local reservoir effects r our results reveal the centennial scale variability over the last 4500 years with r ranges as large as 390 14c yr older r 410 14c yr between 1610 to 1860 a d in our record corresponding to the little ice age suggests a weaker influence of the eac in the south tasman between 4000 and 1900 cal years b p r and r were significantly younger than the modern with values of 170 and 130 14c yr respectively indicating increased eac transport of tropical waters into the south tasman we propose that the large r variability was influenced by strong and abrupt el nino events which punctuated the muted el nino southern oscillation enso period in the mid late holocene and enabled increased westward flow of gyre waters into the sw pacific the strengthening of the eac extension appears to have been a response to the precession modulated enso southern annular mode interactions

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 5500 km long boundary flow off western and southern australia 1 the path of the shelf edge flow off southwestern australia is documented using results from satellite altimetry and sea surface temperature sst and a climatogical in situ analysis during austral winter a continuous current is shown to extend from its origin at north west cape to the southern tip of tasmania a distance of 5500 km satellite sst observations and surface buoy tracks confirm the location and continuity of the current trajectory while the leeuwin current is forced by the strong alongshore pressure gradient associated with the meridional portion of the western australian coastal boundary our results suggest that the essentially zonal shelf edge flow along the southern australian coast arises from the setup of coastal sea level by onshore ekman flow driven by the winter westerly wind and possibly a further alongshore pressure gradient the timing of these two different forcing mechanisms means that the west coast pressure gradient delivers the leeuwin current to the south coast just as the winds reverse and are thus able to maintain the eastward passage of the current the shelf edge flow consists of two main water masses a low salinity warm water type of tropical origin associated with the leeuwin current and a high salinity warm water inflow formed on the western end of the great australian bight continental shelf a naming convention is proposed the leeuwin current representing flow from north west cape to the great australian bight gab the south australian current between the eastern gab and western bass strait and the zeehan current off western tasmania

the south pacific current the southern hemisphere subtropical front stf is a narrow zone of transition between upper level subtropical waters to the north and subantarctic waters to the south it is found near 40 degrees s across the south atlantic and south indian oceans and is associated with an eastward geostrophic current band the current band in each basin is found at or just north of the surface front except near the eastern boundaries where most of the subtropical waters turn north into the eastern limbs of the subtropical gyres the bands associated with the stf are thus distinct features separated from the strong zonal flows of the antarctic circumpolar current farther south the authors have referred to the current bands in the two respective oceans as the south atlantic current and the south indian ocean current in this paper the authors use the historical database from the south pacific ocean to investigate the geostrophic flow associated with the stf there the stf extends across the southern tasman sea from south of tasmania to southern new zealand and a weak eastward flow appears to be associated with it the transport amounts to only about 3 sv 1sv 10 6 m 3 s 1 little of which passes south of new zealand mixing within the eddy rich tasman sea may account for this weakness while also setting up another more significant front in the northern tasman sea the tasman front it branches off from the east australian current toward the north of new zealand along which moves a flow of about 14 sv after passing north of new zealand a portion of this current flows east to contribute to a current band near 30 degrees s while another portion turns south as the east auckland current and meets with subantarctic waters near chatham rise 44 degrees s thus reestablishing the stf an enhanced eastward current band is associated with the front there one that extends across the remainder of the south pacific and is referred to as the south pacific current in comparison with its counterparts in the other basins which typically begin by carrying 30 sv atlantic to 60 sv indian in the upper 1000 m in their western portions before weakening to 10 15 sv in the east the south pacific current is weak near chatham rise it starts with a transport of approximately 5 sv and it remains near this strength as it shifts gradually north across the basin toward south america the current appears to split into two smaller bands in the region of 115 degrees 85 degrees w while near 28 degrees 5 83 degrees w it begins to turn more strongly north and becomes shallower and weaker potential vorticity distributions indicate that this current acts as an impediment toward the northward spreading of antarctic intermediate water but why the south pacific current east of new zealand should be so much weaker than its counterparts in the other basins is not particularly clear it may be due to the presence of new zealand and other topographic barriers to deep now east of australia to the axis of the subtropical gyre in the south pacific shifting more rapidly southward with depth than those elsewhere thus causing greater reductions in the underlying zonal velocities and to strong poleward eddy heat and salt fluxes in the other two basins leading to smaller cross stf gradients in the pacific

biogeochemical iron budgets of the southern ocean south of australia decoupling of iron and nutrient cycles in the subantarctic zone by the summertime supply 1 climate change is projected to significantly alter the delivery stratification boundary currents aridification of landmasses glacial melt of iron to the southern ocean we report the most comprehensive suite of biogeochemical iron budgets to date for three contrasting sites in subantarctic and polar frontal waters south of australia distinct regional environments were responsible for differences in the mode and strength of iron supply mechanisms with higher iron stocks and fluxes observed in surface northern subantarctic waters where atmospheric iron fluxes were greater subsurface waters southeast of tasmania were also enriched with particulate iron manganese and aluminum indicative of a strong advective source from shelf sediments subantarctic phytoplankton blooms are thus driven by both seasonal iron supply from southward advection of subtropical waters and by wind blown dust deposition resulting in a strong decoupling of iron and nutrient cycles we discuss the broader global significance our iron budgets for other ocean regions sensitive to climate driven changes in iron supply

upb zircon geochronology of archaean felsic units in the marble bar region pilbara craton western australia abstract archaean supracrustal rocks that are well exposed in the marble bar region pilbara craton have been assigned to the warrawoona group and younger sequences the predominantly volcanic warrawoona group previously dated at 3300 to 3500 ma is largely basaltic with locally intercalated thick felsic volcanic units the supracrustal rocks have been folded and are distributed around the margins of large roughly circular to ovoid granitic gneissic batholiths a u pb zircon geochronology study was undertaken to obtain precise age constraints for some of the ore deposits in the area especially the big stubby north pole barite and miralga creek zn pb cu au deposits in support of efforts to improve archaean lead isotope models the results also help significantly in interpreting stratigraphic relationships and crustal evolution in the area the new conventional zircon u pb data indicate that most of the warrawoona group from the duffer formation upwards was deposited over a period of 20 ma from 3470 ma to 3450 ma the age of the duffer formation is closely constrained by results of 3471 5 ma and 3465 3 ma and the age of the upper salgash subgroup appears to be established at 3454 1 ma the panorama formation at the southern margin of the north pole dome is 3458 1 9 ma unless the duffer formation was deposited over a period of at least 10 ma this casts doubt on a previously suggested panorama duffer correlation the age of the lower part of the north pole succession is greater than 3458 ma consistent with the correlation of the basal greenstones at north pole with the talga talga subgroup the north pole chert barite unit which is well known for its preservation of early archean stromatolites microfossils and evaporite sediments is clearly older than 3458 ma the 3325 ma age now established for the wyman formation shows that this unit must be excluded from the warrawoona group the age of the talga talga subgroup remains uncertain a felsic schist in the mount ada basalt which has been dated at 3449 3 ma is interpreted to be a sill probably related to the 3450 ma granitoid bodies an age 3724 ma for a zircon xenocryst in the panorama formation is the oldest obtained so far for zircon from the pilbara granite greenstone terrane and indicates the existence of pre pilbara supergroup sialic basement ages of 3465 3 ma and 3449 2 ma applied to previous pb isotope data for the big stubby and miralga creek deposits respectively in combination with comparable data for other syngenetic archaean sulphide deposits yield a general single stage pb evolution model with the parameters t0 4560 ma a0 9 0818 b0 9 9002 and c0 29 343 this gives model ages in accord with known constraints for many archean deposits a model lead age of 3490 ma for the north pole deposit which is older than 3457 ma may be too great but attempts to directly date this deposit have not yet succeeded there are striking parallels between the warrawoona group ages reported here and those recently obtained for the barberton region kaapvaal craton south africa the talga talga subgroup and lower onverwacht tjakastad subgroup sequences have approximately equivalent constraints and an age for the upper salgash subgroup agrees closely with those for the hoogenoeg formation of the upper onverwacht group geluk subgroup

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

hydrothermal alteration at the panorama formation north pole dome pilbara craton western australia an airborne hyperspectral remote sensing dataset was obtained of the north pole dome region of the pilbara craton in october 2002 it has been analyzed for indications of hydrothermal minerals here we report on the identification and mapping of hydrothermal minerals in the 3 459 ga panorama formation and surrounding strata the spatial distribution of a pattern of subvertical pyrophyllite rich veins connected to a pyrophyllite rich palaeohorizontal layer is interpreted to represent the base of an acid sulfate epithermal system that is unconformably overlain by the stromatolitic 3 42 ga strelley pool chert

theory and validation of the multiple window sea surface temperature technique the development of the split window approach for correcting satellite measurement of radiance for atmospheric attenuation is reviewed then the theoretical results are compared to results from actual measurements which consist of satellite measurements in the three infrared windows of the avhrr ground truth for the comparisons comes from buoys the satellite measurements were screened for clouds and the remaining ones were used in the analysis using this data set several statistical analyses were performed these showed that when the two channels that are truly a split window are used the result of the statistical model agrees with the one derived from theoretical considerations when the 3 8 m channel is combined with one in the 10 12 m region the result of the statistical model does not take the split window form results show that the method is capable of producing sea surface temperatures with a standard deviation of 1 k or less

simulation of chlorophyll and iron supplies in the sub antarctic zone south of australia the sub antarctic zone saz is part of the high nutrient low chlorophyll region of the southern ocean where low iron availability limits phytoplankton productivity in the tasman sea the saz displays a unique and large zonal gradient in the surface chlorophyll concentrations in situ measurements show higher dissolved iron in the east than in the west which could explain the zonal chlorophyll gradient to assess and quantify the major sources of iron in this region we use an eddy resolving model to simulate the dissolved fe distribution arising from both the shelf and the dust supply of iron the simulation showed that dissolved fe from the shelf is only transported eastward to about 155 e and the shelf source of dissolved iron is unable to supply iron to the entire tasman sea saz region even when we assume that there no iron losses the simulation with the atmospheric source of iron showed that through a combination of atmospheric transport and ocean transport enough dissolved fe can be supplied to the entire tasman sea saz region to relieve iron limitation from the model simulations we conclude that atmospheric iron supply is essential to generating the observed gradient of the chlorophyll in the saz region of the tasman sea

volcanic sedimentary and tectonostratigraphic environments of the 3 46 ga warrawoona megasequence a review abstract the warrawoona megasequence comprises a 3 46 ga assemblage of tholeiitic and calc alkaline volcanic rocks interlayered with cherty sedimentary rocks deposition occurred in a range of shallow to deeper water environments ranging from the shoreline to distal deposits in sediment starved basins volcanism provided the dominant or only source of clastic sediment sedimentary rocks also contain evaporites probable stromatolites other evidence for the existence of microbial life and possible evidence of meteorite impact the tectonostratigraphic assemblage and its contained facies associations are most similar to those developed in younger volcanic arc or near arc settings the compositions of volcanic rocks are also comparable with those of younger tholeiitic and calc alkaline suites developed above subduction zones the calc alkaline suite has a complex petrogenesis which probably involves mantle derived basaltic melts intermediate to silicic melts derived from subducted mafic crust magma mixing and fractional crystallization intense hydrothermal alteration and a distinctive association of metal deposits are also compatible with the interpretation that the warrawoona megasequence contains examples of early archaean volcanic arc and near arc assemblages

southwest pacific sea surface conditions during marine isotope stage 11 results from dinoflagellate cysts abstract dinoflagellate cyst dinocyst assemblages are examined from three sw pacific marine sediment cores covering marine isotope stage 11 mis11 423 ka 380 ka md06 2988 and md06 2989 are in the east tasman sea north of the subtropical front stf whilst dsdp594 is in subantarctic surface waters saw off eastern new zealand sea surface temperature sst estimates from dinocyst assemblages indicate that the east tasman sea was 2 5 c warmer than present during the peak warmth of mis11 in the east tasman sea north of the stf there is a two step warming into mis11 in cores md06 2988 and md06 2989 east of new zealand and south of the stf at core site dsdp594 dinocyst sst estimates suggest that mis11 was an extended warm period similar to or slightly warmer than present conditions although data from the early phase prior to 417 ka may be compromised due to insufficient modern analogues at all sites glacial interglacial climatic fluctuations were accompanied by large assemblage changes glacial intervals were characterised by higher abundances of assemblages typical of saw nematosphaeropsis labyrinthus selenopemphix antarctica brigantedinium spp subtropical surface water stw assemblages dominated during the interglacial in the east tasman sea including impagidinium aculeatum i patulum and spiniferites mirabilis whilst assemblages consistent with continued saw influence remained during the interglacial at core site dsdp594 albeit with reduced cold water indicators such as s antarctica the changes are particularly pronounced in the east tasman sea where the stf is inferred to have been located further north during glacials mis12 and mis10 the influence of stw at dsdp594 during mis11 and the holocene is inferred to have been less than during mis5e a qualitative dinocyst based index likely reflecting primary productivity also influenced by oxygen concentration on the sea floor is broadly anti phased with sst on glacial interglacial timescales at all sites

subantarctic mode water variability influenced by mesoscale eddies south of tasmania 1 subantarctic mode water samw is formed by deep mixing on the equatorward side of the antarctic circumpolar current the subduction and export of samw from the southern ocean play an important role in global heat freshwater carbon and nutrient budgets however the formation process and variability of samw remain poorly understood largely because of a lack of observations to determine the temporal variability of samw in the australian sector of the southern ocean we used a 15 year time series of repeat expendable bathythermograph sections from 1993 to 2007 seven repeat conductivity temperature depth sections from 1991 to 2001 and sea surface height maps the mean temperature of the samw lies between 8 5 c and 9 5 c mean of 8 8 c standard deviation of 0 3 c and there is no evidence of a trend over the 18 year record however the temperature salinity and pycnostad strength of the samw can change abruptly from section to section in addition the samw pool on a single section often consists of two or more modes with distinct temperature salinity and vertical homogeneity characteristics but similar density we show that the multiple types of mode water can be explained by the advection of anomalous water from eddies and meanders of the fronts bounding the subantarctic zone and by recirculation of samw of different ages our results suggest that infrequently repeated sections can potentially produce misleading results because of aliasing of high interannual variability

the north pole dome a non diapiric dome in the archaean pilbara craton western australia abstract the northeastern part of the archaean pilbara craton is characterised by an ovoid dome and basin pattern of domal granites separated by synformal greenstones supracrustal rocks this ovoid pattern is variably preserved at various structural and stratigraphic levels with the most deeply eroded domes being granite dominated and the least eroded domes being greenstone dominated the north pole dome npd is an example of a relatively high level dome that has a flanking syncline preserving some of the youngest rocks of the craton fortescue group to be involved in the doming process at the apex of the npd is a small intrusive granite that was considered by some workers to be the top of a large underlying domal granite batholith the npd comprises mostly dense basaltic greenstones that range in age from approximately 3500 to 2700 ma the approximately 3460 ma north pole monzogranite a volumetrically insignificant intrusive granite body intrudes the greenstones in the apex of the dome no marginal shear zones occur around the intrusion a new model based on a detailed gravity traverse across the monzogranite suggests that the granite intrusion is plug like up to 1 5 km thick and does not represent the exposed top of a larger underlying domal batholith results from potential field modelling show that the dome is relatively flat bottomed with a base around 5 5 6 5 km deep the npd has no significant granitic material within the dome but like all greenstones is underlain by felsic crust granite below its base the development of the npd and flanking syncline was a multistage process the first stage of doming involved relatively minor doming tilting possibly associated with the emplacement of the monzogranite because palaeocurrents of synchronous volcanic rocks flowed radially outward from the dome it is likely that this doming was minor as there are no recorded unconformities in the warrawoona group in the npd above these volcanic rocks a major dome forming event tilting 20 occurred in the period between 3240 and 2772 ma and was unrelated to the emplacement of the small granite plug diapirism regional folding and refolding from horizontal compression deformed the area into a domal shape type i fold interference pattern uplift and erosion of the dome was superseded by extension and deposition of flood basalts fortescue group that flowed towards the dome three further stages of shortening folded the regional unconformity and the underlying and overlying units further amplified the underlying dome developed the flanking marble bar syncline as well as fold interference patterns in the fortescue group the npd was developed over a 800 ma time frame ostensibly by a process of fold interference due to multiple stages of horizontal compression this work shows that diapirism was not the cause of the development of the domal geometry of the npd and its flanking syncline rather folding and refolding due to horizontal compression was the principal controlling factor

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

intermediate depth circulation of the indian and south pacific oceans measured by autonomous floats as part of the world ocean circulation experiment 306 autonomous floats were deployed in the tropical and south pacific ocean and 228 were deployed in the indian ocean to observe the basinwide circulation near 900 m depth mean velocities seasonal variability and lateral eddy diffusivity from the resultant 2583 float years of data are presented area averages local function fits and a novel application of objective mapping are used to estimate the mean circulation patterns of mean circulation resemble those at the surface in both basins well developed subtropical gyres twice as strong in the indian ocean as in the pacific feed western boundary currents tropical gyres are separated by eastward flow along the equator in both hemispheres of both basins although the indian subcontinent splits the north indian tropical gyre the antarctic circumpolar current acc and west wind drifts are prominent in both basins generally tending slightly southward but deviating to the north behind the del cano kerguelen and campbell plateaus and of course south america remarkably the eastern boundaries of the southern subtropical gyres in all three basins apparently occur in the ocean interior away from land the indian ocean s subtropical gyre and perhaps part of the south atlantic s reaches east to a retroflection just upstream of the campbell plateau south of new zealand seasonal variability at 900 m is focused around the equator with weaker variability found near certain bathymetric features there is a remarkable agreement between the observed seasonable variability and that predicted by the jet propulsion laboratory jpl estimating the circulation and climate of the ocean ecco data assimilating numerical model aside from seasonal effects eddy variability is greatest along the equator in tropical and subtropical western basins and along the acc integrals of velocity across regional passages tasman sea mozambique channel provide useful reference for hydrographic analyses of transport across whole ocean basins however the uncertainty associated with the appropriate continuity relation for horizontal flow e g geostrophy vs nondivergence is comparable to the mean flow

regional circulation and its impact on upper ocean variability south of tasmania ocean colour images of the subantarctic zone saz south of tasmania show a higher biomass in the east than in the west to identify the main features of the regional circulation and the physical drivers of the east west contrast we used world ocean circulation experiment hydrographic sections sr3 and p11s west and east of tasmania respectively argo float profiles and trajectories and high resolution climatology the east australian current and the tasman outflow are the mechanisms driving the variability in the eastern subantarctic zone this region has a weak flow and an enhanced input of subtropical waters through eddies interleaving and a subsurface salinity maximum intruding from the north to south in the western subantarctic zone the regional circulation is dominated by a northwestward circulation and a deep reaching anticyclonic recirculation the south tasman rise acts as a barrier inhibiting exchange between waters southeast and southwest of tasmania the regional circulation and mixing processes result in the strong contrast in water properties between the eastern and western subantarctic zone cooler and fresher in the west and warmer and saltier in the east the subantarctic mode water samw pycnostad is more prominent in the west with a local variety of samw associated with the anticyclonic recirculation west of the south tasman rise antarctic intermediate water aaiw formed in the southeastern pacific and southwestern atlantic oceans meet in the saz south of tasmania cool fresh and well ventilated aaiw is found in the west and southeast saz relatively warm salty and low oxygen aaiw enters the saz from the tasman sea after having traversed the pacific ocean subtropical gyre enhanced input of subtropical water high in micronutrients such as iron in the east likely supports the higher surface biomass observed there the physical processes responsible for maintaining the east west contrast south of tasmania e g regional circulation eddies and intrusions are likely to drive variability in physical and biogeochemical properties of samw aaiw and the subantarctic zone elsewhere in the southern ocean

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

oceanography of the subantarctic and polar frontal zones south of australia during summer setting for the saz sense study abstract this paper provides a description of the physical and chemical properties temperature salinity macro nutrient and oxygen concentrations and bulk biomass indicators chlorophyll and beam attenuation prevailing in the subantarctic zone and polar front zones south of tasmania australia during the sensitivity of the subantarctic zone to environmental change saz sense expedition carried out in the austral summer of 2007 phytoplankton biomass showed a characteristic north south gradient of decreasing chlorophyll from the subantarctic zone to polar frontal zone as well as a zonal gradient in the northern subantarctic zone with an increase in chlorophyll from southwest to southeast of tasmania the representativeness of the observations was assessed by comparison to previous studies including satellite observation of chlorophyll biomass over a 10 year period we consider the possible role of spatial differences in i ocean water masses and frontal systems ii upper mixed layer stratification at three process stations and iii nutrient availability in controlling the observed variations in phytoplankton biomass in the region zonal gradients of the basic oceanographic physical and chemical conditions in the subantarctic zone were relatively small and therefore unlikely to control the three fold west to east differences observed in the accumulation of phytoplankton biomass the zonal variation in subantarctic zone chlorophyll biomass appears to be driven at least partly by greater micro nutrient iron supply to the waters east of tasmania as reported also by others bowie et al 2009 mongin et al 2011a despite this condition the region of higher phytoplankton biomass to the southeast of tasmania was only marginally more productive than the region of lower biomass west of tasmania and south of the polar front and exported less particulate carbon than the lower biomass waters jacquet et al 2011

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