annual biogenic particle fluxes to the interior of the north atlantic ocean studied at 34 n 21 w and 48 n 21 w abstract in order to clarify the annual quality quantity and export processes of biogenic particles from the euphotic zone to the deep ocean interior an array of automated time series sediment traps were deployed for 1 year from 4 april 1989 to 17 april 1990 at 34 n 21 w and 48 n 21 w as part of the joint global ocean flux program jgofs north atlantic bloom experiment nabe three sediment traps with 13 time series sediment collectors were placed at both stations approximately 1 and 2 km below the surface and 0 7 km above the bottom they collected settling particles during 26 14 day intervals for 376 days with an 20 day hiatus in september october 1989 for changeover of the trap moorings the collection periods of the six traps were synchronized forming a spatio temporal matrix of 156 samples the annual mass flux at about 2 km deep during this experiment was 22 and 27 g m 2 y 1 at the 34 and 48 n stations consisting of biogenic particles with traceable quantities of lithogenic particle flux the spring particle bloom characterized by the sedimentation of particles relatively enriched by norg began in january at the 34 n station and in march at the 48 n station the bloom continued for 4 5 and 3 months and provided 62 and 50 of the annual biogenic particle mass flux at 2 km at the 34 and 48 n stations the surface bloom penetrated to the ocean interior within a few weeks with apparently accelerated settling speed at deeper layers the order of susceptibility of biogenic elements to mineralization while settling in the 0 7 1 km a b water column was from least to most resistant p norg corg si and ca the c n p ratio at 0 7 km a b was 154 18 1 at the 34 n station and 148 18 1 at the 48 n station

surface eddy momentum flux and velocity variances in the southern ocean from geosat altimetry abstract satellite altimetry has previously been used to map the magnitude of the surface eddy variability of the global oceans but the direction of the time variable velocities have been more difficult to determine here a technique is presented for resolving both magnitude and direction of residual surface geostrophic velocities at geosat altimeter crossover points providing a two year time series with a temporal resolution of 17 days and horizontal resolution of around 100 km the time series of residual velocity components are then used to determine surface eddy statistics in the southern ocean and to investigate the role of transient eddies in the southern ocean momentum balance the surface eddy statistics from geosat crossover points show a complex spatial distribution in the surface reynolds stresses u 2 v 2 u v in contrast to the assumptions of isotropic variability in previous analyses of altimeter data velocity variance ellipses are found to be distinctly anisotropic in many regions

regional variation of spring n uptake and new production in the southern ocean 1 nitrate ammonium and urea uptake were examined in the southern ocean australian sector during the 2001 austral spring on the basis of n uptake conditions three regions were distinguished 1 the sub antarctic zone and the sub antarctic front 2 the polar and inter polar frontal zones and 3 the antarctic zone south and the seasonal ice zone n uptake was highest in region 3 and dominated by new production region 1 had the lowest n uptake and switched from regenerated to new production between two visits approximately 1 month apart region 2 displayed intermediate n uptake and the lowest new production this contrasts with previous study at 170 w where new production was high around the polar front and indicates that this area is not highly productive nor particle exporting at all longitudes overall n uptake and new production were low all along the latitudinal transect compared to other areas of the southern ocean under spring conditions

regional retrograde metamorphism of a high grade terrain the willyama complex broken hill australia abstract retrograde metamorphism has been a major influence in the development of the presently observed lithologies of the willyama complex broken hill two broad types of retrogression are distinguished pseudomorphous and kinematic retrogression the former type of retrogression involves replacement of prograde phases without complete loss of the high grade fabric hence the prograde assemblage can frequently be inferred kinematic retrogression involves the development of a new schistose fabric and like pseudomorphous retrogression is commonly related to f3 deformation retrogression was initiated during the waning stage of prograde metamorphism and was accompanied by an influx of aqueous fluid at similar pressure but lower temperature conditions than prograde metamorphism the source of the water is believed to be the crystallization of cooling partial melts the regional nature of this willyama style of retrogression is attributed to the metasediment rich nature of the sequence the high geothermal gradient and the considerable amount of in situ partial melting

biological and physical controls on n2 o2 and co2 distributions in contrasting southern ocean surface waters we present measurements of pco2 o2 concentration biological oxygen saturation o2 ar and n2 saturation n2 in southern ocean surface waters during austral summer 2010 2011 phytoplankton biomass varied strongly across distinct hydrographic zones with high chlorophyll a chl a concentrations in regions of frontal mixing and sea ice melt pco2 and o2 ar exhibited large spatial gradients range 90 to 450 atm and 10 to 60 respectively and covaried strongly with chl a however the ratio of biological o2 accumulation to dissolved inorganic carbon dic drawdown was significantly lower than expected from photosynthetic stoichiometry reflecting the differential time scales of o2 and co2 air sea equilibration we measured significant oceanic co2 uptake with a mean air sea flux 10 mmol m 2 d 1 that significantly exceeded regional climatological values n2 was mostly supersaturated in surface waters mean n2 of 2 5 while physical processes resulted in both supersaturation and undersaturation of mixed layer o2 mean o2phys 2 1 box model calculations were able to reproduce much of the spatial variability of n2 and o2phys along the cruise track demonstrating significant effects of air sea exchange processes e g atmospheric pressure changes and bubble injection and mixed layer entrainment on surface gas disequilibria net community production ncp derived from entrainment corrected surface o2 ar data ranged from 40 to 300 mmol o2 m 2 d 1 and showed good coherence with independent ncp estimates based on seasonal mixed layer dic deficits elevated ncp was observed in hydrographic frontal zones and stratified regions of sea ice melt reflecting physical controls on surface water light fields and nutrient availability

the δ15n of nitrate in the southern ocean consumption of nitrate in surface waters we report nitrogen isotope data for nitrate from transects of hydrocast and surface samples collected in the eastern indian and pacific sectors of the southern ocean focusing here on the data from the upper water column to study the effect of nitrate consumption by phytoplankton the 15n of nitrate increases by 1 2 from deep water into the antarctic summertime surface layer due to kinetic isotopic fractionation during nitrate uptake estimation of the nitrate uptake isotope effect from antarctic depth profiles yields values in the range of 5 6 in east indian sector and 4 5 in the east pacific sector surface transect data from the pacific sector also yield values of 4 5 the major uncertainty in the profile based estimation of the isotope effect involves the 15n of nitrate from the temperature minimum layer below the summertime antarctic surface layer which deviates significantly from the predictions of simple models of isotope fractionation for the subantarctic surface it is possible to distinguish between nitrate supplied laterally from the surface antarctic and nitrate supplied vertically from the subantarctic thermocline because of the distinctive relationships between the 15n and concentration of nitrate in these two potential sources our subantarctic samples collected during the summer and fall indicate that nitrate is supplied to the subantarctic surface largely by northward transport of antarctic surface water isotopic data from the pacific sector of the subantarctic suggest an isotope effect of 4 5 indistinguishable from the antarctic estimates in this sector

the use of an outlier detecting method in time series of continuous daily measurements of underground water level and temperature in earthquake prediction investigation abstract continuous daily measurements of underground water level and temperature have been monitored in four selected shallow wells in a seismically active area close to thessaloniki greece the aim was to study the changes in the underground water level and temperature with respect to earthquakes occurring in the same area during 1 january 1988 to 31 december 1989 a graphical method has been applied to analyze the time series in order to detect outliers our results reveal that a strong correlation exists the earthquakes occurred in the area and the water level time series the correlation was found to be weak in the case of the water temperature time series most of the outliers found correspond to a time interval varying between 1 and 7 days before or after the earthquakes the magnitude of the underground water level change varies from 3 to 10 cm and that of temperature from 0 3 to 0 8 c the strongest outliers correlate to earthquakes of magnitude greater than 3 0 the software developed to detect outliers use immediate preceding observations in the time series of continuous daily measurements at the time of their occurrence this is very important in studying precursory phenomena of impending earthquakes

particulate organic carbon fluxes to the ocean interior and factors controlling the biological pump a synthesis of global sediment trap programs since 1983 particulate organic carbon poc is vertically transported to the oceanic interior by aggregates and their ballasts mainly caco3 and biogenic opal with a smaller role for lithogenic aerosols through the mesopelagic zone diel migrating zooplankton communities effect vertical transport and remineralization of poc in the upper layers of the ocean below 1 5 km the presence of zooplankton is reduced and thus the aggregates travel mainly by gravitational transport we normalized the fluxes of poc caco3 and biogenic opal from data published on samples collected at 134 globally distributed bottom tethered time series sediment trap ts trap stations to annual mole fluxes at the mesopelagic bathypelagic boundary m b at 2 km and defined them as fm bcorg fm bcinorg and fm bsibio using this global data set we investigated 1 the geographic contrasts of poc export at m b and 2 the supply rate of co2 to the world mesopelagic water column fm bcorg varies from 25 pacific warm pool to 605 divergent arabian sea mmolc m 2 yr 1 fm bcinorg varies from 8 high latitude polar oceans or 15 pacific warm pool to 459 divergent arabian sea mmolc m 2 yr 1 and fm bsibio the most spatially temporally variable flux ranges from 6 north atlantic drift to 1118 pacific subarctic gyre mmolsi m 2 yr 1 the oceanic region exhibiting the highest poc flux over a significantly large region is the area of the north pacific boreal gyres where the average fm bcorg 213 fm bcinorg 126 and fm bsibio 578 mmol m 2 yr 1 fm bcorg and fm bcinorg are particularly high in large upwelling margins including the divergent arabian sea and off cape verde one of the data sets showing the lowest flux over a significant region basin is fm bcorg 39 fm bcinorg 69 and fm bsibio 22 mmol m 2 yr 1 in the north pacific subtropical tropical gyres pan atlantic average fluxes are similar except fm bsibio fluxes are even lower where corg cinorg and sibio cinorg are 1 defines the carbonate ocean and where these ratios are 1 defines the silica ocean the carbonate ocean occupies about 80 of the present world pelagic ocean between the two major oceanographic fronts the north pacific polar front and the antarctic polar front and the silica ocean is found on the polar sides of these fronts the total global annual fluxes of fm bcorg fm bcinorg and fm bsibio at m b calculated by parameterizations of the export flux data from 134 stations are surprisingly similar 36 2 33 8 and 34 6 teramol yr 1 120 112 and 114 mmol m 2 yr 1 respectively resulting in a near uniform binary ratio between the above three elements of about one the global ternary ratios estimated from 152 ts trap samples of the three elements are 35 32 33 from our global fm bcorg and a published model estimate of the global export production we estimate the regeneration rate of co2 through the mesopelagic zone by the biological pump is 441 teramolc yr 1 based on our global fm bcinorg and recently estimated global primary production of pic 36 86 teramolc yr 1 of pic is assumed to be dissolved within the upper 2 km of the water column

relevance of silicon isotopes to si nutrient utilization and si source assessment in antarctic waters 1 we analyzed 29si of dissolved silicate for eight water column profiles across the southern ocean south of australia in spring 2001 from the seasonal ice zone siz north to the subantarctic zone saz including the first isotopic compositions measured for si depleted seawaters all profiles display mixed layer enrichments in heavy si isotopes relative to deep water in accordance with preferential uptake of the light isotope by diatoms as silicate levels decrease from the siz northward across the polar front zone pfz to the saz surface and mesopelagic 29si signatures generally become progressively heavier but the most si depleted saz waters do not exhibit 29si values heavier than in the pfz this intricacy appears to derive from variations in the vertical and horizontal supply of silicate to surface waters and by applying a steady state open system model we estimate a fractionation factor 29 between diatoms and seawater of 0 45 0 17 independently of zones and phytoplankton community though encouraging these results are related to latitudinal changes in mesopelagic 29si values complexity in surface silicate 29si correlations and differences from previous studies which underline the need for caution in the use of silicon isotopes in paleoceanographic studies until systematic efforts have been undertaken to better understand modern variations

an early pliocene thermal disturbance of the main central thrust central nepal implications for himalayan tectonics since the beginning of the collision between india and asia at about 50 ma the convergence in the himalaya has largely been taken up along major thrust zones in this study samples of the lesser himalaya formations up to 10 km below the main central thrust mct and the greater himalaya sequence up to 12 km above the mct have been analyzed by the 40ar 39ar and u pb methods to investigate the thermal history of the mct the ages can be summarized as follows 1 the youngest ages from muscovites 3 1 ma biotites 3 4 ma and hornblendes 4 1 ma all come from within 1 km of the mct 2 there is a marked asymmetry of ages between the footwall and the hanging wall of the mct the maximum mica age in the hanging wall greater himalaya sequence is 13 ma whereas a muscovite 5 km below the mct in the footwall has an age spectrum with a gradient from 400 to 1400 ma 3 five k feldspars from 6 2 to 11 9 km above the mct all give minimum ages in the range 3 0 6 4 ma and 4 a 206pb 238u age on a brannerite from the greater himalayan sequence is 4 8 ma structural and petrologic observations preclude the possibility that this age distance distribution reflects faulting within the greater himalaya sequence and production of the necessary thermal energy by shear heating requires unrealistically high shear stresses infiltration of hot fluids through the mct zone appears to be the best hypothesis to explain these data simple numerical simulations which account for heat transfer by advection within the fluid flow zone and by conduction outside it indicate that the observed age distribution could have been produced by infiltration of hot fluids through the mct zone at circa 5 to 4 ma within the following range of conditions the fluids heated rocks to temperatures in the range 470 to 510 c for less than 1 million years in a region narrower than the entire mct zone the temperature of the thermal disturbance inferred from the 40ar 39ar data is consistent with petrologic data from albitic alteration assemblages in the greater himalaya sequence and the u pb age of the brannerite is similar to the youngest 40ar 39ar hornblende age this scenario hydrothermal heating culminating at about 4 ma is similar to the model of le fort 1981 for the generation of the high himalayan leucogranites in the late oligocene early miocene by dehydration of the footwall rocks of an active thrust in the younger instance we interpret that fluids derived from the footwall rocks of the main boundary thrust migrated upward through the lesser himalaya formations and were subsequently channeled along the mct producing the thermal disturbance

quantifying export production in the southern ocean implications for the ba xs proxy the water column and sedimentary baxs distribution around the crozet plateau is used to decipher the controls and timing of barite formation and to evaluate how export production signals are recorded in sediments underlying a region of natural fe fertilization within the fe limited southern ocean export production estimated from preserved vertical sedimentary baxs accumulation rates are compared with published export fluxes assessed from an integrated study of the biological carbon pump to determine the validity of baxs as a quantitative proxy under different fe supply conditions typical of the southern ocean detailed assessment of the geochemical partitioning of ba in sediments and the lithogenic end member allows appropriate correction of the bulk ba content and determination of the baxs content of sediments and suspended particles the upper water column distribution of baxs is extremely heterogeneous spatially and temporally organic carbon baxs ratios in deep traps from the fe fertilized region are similar to other oceanic settings allowing quantification of the inferred carbon export based on established algorithms there appears to be some decoupling of poc and ba export in the fe limited region south of the plateau the export production across the crozet plateau inferred from the baxs sedimentary proxy indicates that the fe fertilized area to the north of the plateau experiences enhanced export relative to equivalent southern ocean settings throughout the holocene and that this influence may also have impacted the site to the south for significant periods this interpretation is corroborated by alternative productivity proxies opal accumulation 231paxs 230thxs baxs can be used to quantify export production in complex settings such as naturally fe fertilized volcanoclastic areas providing appropriate lithogenic correction is undertaken and sediment focusing is corrected for along with evaluation of barite preservation

sensitivity of δ15n of nitrate surface suspended and deep sinking particulate nitrogen to seasonal nitrate depletion in the southern ocean 1 we report measurements of the 15n of nitrate suspended particulate nitrogen pn and sinking pn from cruises and moored sediment traps in the subantarctic zone saz and polar frontal zone pfz south of australia as expected surface water nitrate 15n increased as nitrate was consumed during the spring summer bloom in contrast the seasonal cycles of surface water suspended and sinking pn 15n did not fit expectations from nitrate assimilation alone rather than increasing the 15n of surface suspended pn was relatively constant in the saz at 1 and decreased during the summer in the pfz from 0 to 4 most likely due to the production of low 15n pn by summertime ammonium recycling deep sediment trap pn 15n also displayed seasonal decreases from 4 to 1 in the saz and from 3 5 to 0 5 in the pfz which correlated with pon flux magnitude during high flux periods exported pn 15n values were close to expectations from nitrate based export but low flux periods exhibited higher 15n consistent with either a reduction in the isotope effect of nitrate assimilation or more extensive isotopic alteration of the sinking material during low flux periods the mass balance between net nitrate supply and exported pn that links sinking flux 15n to nitrate utilization requires only that the annually integrated rather than the seasonally varying sinking flux of pn 15n correlates with nitrate depletion while a correlation between annually integrated sinking pn 15n to nitrate depletion was observed in both the saz and pfz the sensitivity of sinking pn 15n to nitrate depletion was lower than expected moreover the seasonal observations raise the possibility that loss of the summertime high flux period represents an alternative explanation to increased nitrate utilization for the high sedimentary pn 15n observed during glacial periods

moored sediment trap measurements of carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia sediment trap moorings were deployed from september 21 1997 through february 21 1998 at three locations south of australia along 140 e at 47 s in the central subantarctic zone saz with traps at 1060 2050 and 3850 m depth at 51 s in the subantarctic front with one trap at 3080 m and at 54 s in the polar frontal zone pfz with traps at 830 and 1580 m particle fluxes were high at all the sites 18 32 g m 2 yr 1 total mass and 0 5 1 4 g organic carbon m 2 yr 1 at 1000 m assuming minimal flux outside the sampled summer period these values are similar to other southern ocean results and to the median estimated for the global ocean by lampitt and antia 1997 and emphasize that the southern ocean exports considerable carbon to the deep sea despite its high nutrient low chlorophyll characteristics the saz site was dominated by carbonate 50 of total mass and the pfz site by biogenic silica 50 of total mass both sites exhibited high export in spring and late summer with an intervening low flux period in december for the 153 day collection period particulate organic carbon export was somewhat higher in all the traps in the saz range 0 57 0 84 gc m 2 than in the pfz range 0 31 0 53 with an intermediate value observed at the saf 0 60 the fraction of surface organic carbon export estimated from seasonal nutrient depletion lourey and trull 2001 reaching 1000 m was indistinguishable in the saz and pfz despite different algal communities

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

iron deficiency limits phytoplankton growth in antarctic waters enrichment experiments were performed in the ross sea to test the hypothesis that iron deficiency is responsible for the phytoplankton s failure to use up the luxuriant major nutrient supplies found in these and all other offshore antarctic ocean waters nitrate uptake rates in the controls without added trace elements ranged from 0 58 to 1 22 mol kg 1 d 1 the addition of 1 to 5 nmol of unchelated fe per liter resulted in rates that were 2 to 10 times higher 2 54 to 6 00 mol no3 kg 1 d 1 rates in bottles with 2 nmol mn added were identical to those in the controls 0 57 to 1 04 mol no3 kg 1 d 1 total decreases in no3 were balanced by increases in particulate organic n these results suggest that fe deficiency is the primary reason that the present day southern ocean biological pump is shut off in contrast iron was 50 times more abundant during the last glacial maximum greater fe availability may have stimulated the biological pump and contributed to the ice age drawdown of atmospheric c02 these results also imply that large scale southern ocean fe fertilization is feasible at least in terms of the total amounts of fe required i e 100 000 to 500 000 tons yr 1

location and dynamics of the antarctic polar front from satellite sea surface temperature data the location of the antarctic polar front pf was mapped over a 7 year period 1987 1993 within images of satellite derived sea surface temperature the mean path of the pf is strongly steered by the topographic features of the southern ocean the topography places vorticity constraints on the dynamics of the pf that strongly affect spatial and temporal variability over the deep ocean basins the surface expression of the pf is weakened and the pf meanders over a wide latitudinal range near large topographic features width and temperature change across the front increase and large scale meandering is inhibited elevated mesoscale variability is seen within and downstream of these areas and may be the result of baroclinic instabilities initiated where the pf encounters large topographic features the strong correlations between topography and pf dynamics can be understood in the context of the planetary potential vorticity ppv or f h field mean ppv at the pf varies by more than a factor of 2 along its circumpolar path however at the mesoscale the pf remains within a relatively narrow range of ppv values around the local mean away from large topographic features the pf returns to a preferred ppv value of 25 10 9 m 1 s 1 despite large latitudinal shifts the mean paths of the surface and subsurface expressions of the pf are closely coupled over much of the southern ocean

eddy variability and energetics from direct current measurements in the antarctic circumpolar current south of australia two year time series measurements of current velocity and temperature in the subantarctic front saf south of australia from 1993 to 1995 provide estimates of eddy fluxes of heat and momentum across the antarctic circumpolar current acc and further insight into the variability of the acc the saf was found to be an energetic meandering jet with vertically coherent fluctuations varying on a timescale of 20 days with typical amplitude 30 cm s21 at 1150 dbar a daily varying coordinate frame that follows the direction of flow allowed mesoscale variability of the saf to be isolated from variability due to meandering of the front and proved very successful for examining eddy fluxes vertically averaged cross stream eddy heat flux was 11 3 kw m 22 poleward and significantly different from zero at 95 for fluctuations in the 2 90 day band zonally integrated this eddy heat flux 50 9 pw is more than large enough to balance heat lost south of the polar front and is as large as cross saf fluxes found in drake passage cross stream eddy momentum fluxes were small not significantly different from zero and of indeterminate sign but tending to decelerate the mean flow a relationship between vertical motion and meander phase identified in the gulf stream was found to hold for the acc eddy kinetic energy levels were similar to those in drake passage and southeast of new zealand eddy potential energy was up to an order of magnitude larger than at other acc sites most likely because meandering of the front is more common here baroclinic conversion was found to be the dominant mechanism by which eddies grow south of australia typical eddy growth time is estimated to be 30 days approximately twice as fast as in drake passage consistent with eddy energy growing rapidly downstream

carbonate counter pump stimulated by natural iron fertilization in the polar frontal zone the production of organic carbon in the ocean s surface and its subsequent downward export transfers carbon dioxide to the deep ocean this co2 drawdown is countered by the biological precipitation of carbonate followed by sinking of particulate inorganic carbon which is a source of carbon dioxide to the surface ocean and hence the atmosphere over 100 1 000 year timescales1 the net transfer of co2 to the deep ocean is therefore dependent on the relative amount of organic and inorganic carbon in sinking particles2 in the southern ocean iron fertilization has been shown to increase the export of organic carbon3 4 5 but it is unclear to what degree this effect is compensated by the export of inorganic carbon here we assess the composition of sinking particles collected from sediment traps located in the polar frontal zone of the southern ocean we find that in high nutrient low chlorophyll regions that are characterized by naturally high iron concentrations fluxes of both organic and inorganic carbon are higher than in regions with no iron fertilization however the excess flux of inorganic carbon is greater than that of organic carbon we estimate that the production and flux of carbonate in naturally iron fertilized waters reduces the overall amount of co2 transferred to the deep ocean by 6 32 compared to 1 4 at the non fertilized site we suggest that an increased export of organic carbon stimulated by iron availability in the glacial sub antarctic oceans may have been accompanied by a strengthened carbonate counter pump

controls on the carbon isotopic composition of southern ocean phytoplankton carbon isotopic compositions of suspended organic matter and biomarker compounds were determined for 59 samples filtered from southern ocean surface waters in january 1994 along two north south transects woce sr3 from tasmania to antarctica and across the princess elizabeth trough pet east of prydz bay antarctica along the sr3 line bulk organic matter show generally decreasing 13c contents southward which are well correlated with increasing dissolved molecular carbon dioxide concentrations co2 aq this relationship does not hold along the pet transect using concentrations and isotopic compositions of molecular compounds we evaluate the relative roles of several factors affecting the 13c of southern ocean suspended particulate organic matter along the woce sr3 transect the concentration of co2 aq plays an important role it is well described by a supply versus demand model for the extent of cellular co2 utilization and its associated linear dependence of isotopic fractionation ep on the reciprocal of co2 aq an equally important factor appears to be changes in algal assemblages along the sr3 transect with their contribution to isotopic fractionation also well described by the supply and demand model when formulated to include the cell surface volume control of supply changes in microalgal growth rates appear to have a minor effect on ep along the pet transect algal assemblage changes and possibly changes in microalgal growth rates appear to strongly affect the carbon isotopic variations of suspended organic matter these results can be used to improve the formulation of modern carbon cycle models that include phytoplankton carbon isotopic fractionation

mixing and remineralization in waters detrained from the surface into subantarctic mode water and antarctic intermediate water in the southeastern pacific a hydrographic data set collected in the region and season of subantarctic mode water and antarctic intermediate water samw and aaiw formation in the southeastern pacific allows us to estimate the preformed properties of surface water detrained into these water masses from deep mixed layers north of the subantarctic front and antarctic surface water south of the front using 10 measured seawater properties we estimate the fractions of samw aaiw that originate as surface source waters as well as fractions that mix into these water masses from subtropical thermocline water above and upper circumpolar deep water below the subducted samw aaiw ages associated with the detrained surface water and remineralization and dissolution rates and ratios the mixing patterns imply that cabbeling can account for 0 005 0 03 kg m 3 of additional density in aaiw and 0 0 02 kg m 3 in samw we estimate a shallow depth 300 700 m above the aragonite saturation horizon calcium carbonate dissolution rate of 0 4 0 2 mol caco3 kg 1 yr 1 a phosphate remineralization rate of 0 031 0 009 mol p kg 1 yr 1 and remineralization ratios of p n o2 corg of 1 15 5 0 6 143 10 104 22 for samw aaiw our shallow depth calcium carbonate dissolution rate is comparable to previous estimates for our region our o2 p ratio is smaller than many global averages our model suggests neglecting diapycnal mixing of preformed phosphate has likely biased previous estimates of o2 p and corg p high but that the corg p ratio bias may have been counteracted by a second bias in previous studies from neglecting anthropogenic carbon gradients

the fate of diatom valves in the subantarctic and polar frontal zones of the southern ocean sediment trap versus surface sediment assemblages abstract an array of deep ocean sediment traps was initiated in 1997 within the australian sector of the southern ocean and serviced annually for over a decade the subantarctic site is ongoing as part of the southern ocean time series here we expand on previous findings obtained from the shallow traps 1000 m depth in the polar frontal zone pfz and subantarctic zone saz by examining the chemical composition and diatom assemblages collected by sediment traps deployed at bathypelagic depths in the pfz 1500 m depth years 1997 1998 1999 2000 and 2003 2004 and saz 2000 and 3800 m year 1999 2000 additionally the diatom assemblages of the surface sediments below the traps were analyzed to document how the seasonal signal is recorded in the sedimentary record analysis of the changes of the bsi poc ratios with depth at both sites confirms previous work suggesting that the decoupling between si and c cycles in the southern ocean is not different from other biogeochemical provinces of the world s ocean comparison of the seasonal flux pattern registered by the traps indicates that the diatom assemblages in the sediments of the antarctic zone and pfz mainly represent the summer period in contrast the assemblages found in the sediments of the saz are a reflection of the spring and summer months a period characterized by a larger variability in chemical and physical parameters the strong correlation between the poc fluxes and the relative abundance of a group of diatom species mainly pseudo nitzschia and small fragilariopsis in the pfz traps suggest that there is an intimate relationship between the development of these species and the poc pulses to the deepest layers of the water column in this region interestingly analysis of the diatom assemblages in the surface sediments reveals that the strong dissolution in the sediment water interface removed the signal of these carbon sinkers from the sedimentary record leaving the sediment assemblage enriched in heavily silicified species

seasonal variations origin and fate of settling diatoms in the southern ocean tracked by silicon isotope records in deep sediment traps the southern ocean plays a pivotal role in the control of atmospheric co 2 levels via both physical and biological sequestration processes the biological carbon transfer to the ocean interior is tightly coupled to the availability of other elements especially iron as a trace limiting nutrient and dissolved silicon as the mineral substrate that allows diatoms to dominate primary production importantly variations in the silicon cycling are large but not well understood here we use 30 si measurements to track seasonal flows of silica to the deep sea as captured by sediment trap time series for the three major zones antarctic az polar frontal pfz and sub antarctic saz of the open southern ocean variations in the exported flux of biogenic silica bsi and its 30 si composition reveal a range of insights including that i the sinking rate of bsi exceeds 200 m d 1 in summer in the az yet decreases to very low values in winter that allow particles to remain in the water column through to the following spring ii occasional vertical mixing events affect the 30 si composition of exported bsi in both the saz and az and iii the 30 si signature of diatoms is well conserved through the water column despite strong bsi and particulate organic carbon poc attenuation at depth and is closely linked to the si consumption in surface waters with the strong coupling observed between bsi and poc fluxes in pfz and az these data provide new constraints for application to biogeochemical models of seasonal controls on production and export

δ18o seasonality of planktonic foraminifera from southern ocean sediment traps latitudinal gradients and implications for paleoclimate reconstructions abstract the oxygen isotopic record obtained from globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s was analysed for 5 sediment traps moored in the southern ocean and southwest pacific the traps extend from subtropical to the polar frontal environments providing the first analysis of seasonal foraminiferal 18 o records from these latitudes comparison between the foraminiferal records and various equations for predicted 18 o of calcite reveals that the predicted 18 o is best captured by the equations of epstein et al 1953 epstein s buchsbaum r lowenstam h a urey h c 1953 revised carbonate water isotopic temperature scale geological society of america bulletin 64 1315 1326 and kim and o neil 1997 kim s t o neil j r 1997 equilibrium and non equilibrium oxygen isotope effects in synthetic carbonates geochimica et cosmochimica acta 61 3461 3475 the epstein equation shows a constant offset from the 18 o of g bulloides and n pachyderma s across the full range of latitudes the seasonal range in 18 o values for these two species implies a near surface habitat across all sites while g inflata most likely dwells at 50 m depth a significant finding in this study was that offsets from predicted 18 o for g bulloides do not correlate to changes in the carbonate ion concentration this suggests that co 3 2 in and of itself may not capture the full range of carbonate chemistry conditions in the marine system this sediment trap deployment also reveals distinct seasonal flux patterns for each species comparison between flux weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint at the 51 s site g bulloides has a spring flux peak while n pachyderma s is dominated by summer production the imprint of these differing seasonal production patterns on the flux weighted 18 o values results in more depleted 18 o for n pachyderma s than for g bulloides interpretations of n pachyderma s isotopic composition as a record of subsurface conditions may therefore need to be refined with implications for interpretation of depleted glacial 13 c for this species sigman boyle 2000 sigman d m boyle e a 2000 glacial interglacial variations in atmospheric carbon dioxide nature 407 859 869

the age of water and ventilation timescales in a global ocean model abstract the age of water in the world ocean is studied using a passive age tracer introduced into a global ocean model additional information is derived from a transient dye tracer that tracks the time dependent spreading of surface waters into the model ocean interior of particular interest is the nature of ocean ventilation over the 10 100 yr timescale as well as the simulated age of deep and bottom water masses in the upper model levels young water is found to correspond with regions of convergence and downwelling in the surface ekman layer upwelling and convection are both shown to age the upper ocean by entraining older waters into the surface mixed layer in the deep model levels water age varies greatly between oceans with young water found in convectively active regions in the north atlantic and in the ross and weddell seas and old water found in the deep north pacific the oldest water mass mixture located at 2228 m depth in the western pacific ocean is dated at 1494 years made

coastal zone color scanner pigment concentrations in the southern ocean and relationships to geophysical surface features the spatial and seasonal distributions of phytoplankton pigment concentration over the entire southern ocean have been studied for the first time using the coastal zone color scanner historical data set from october 1978 through june 1986 enhanced pigment concentrations are observed between 35 s and 55 s throughout the year with such enhanced regions being more confined to the south in the austral summer and extending further north in the winter north and south of the polar front phytoplankton blooms 1 mg m3 are not uniformly distributed around the circumpolar region instead blooms appear to be located in regions of ice retreat or high melt areas such as the scotia sea and the ross sea in relatively shallow areas e g the patagonian and the new zealand shelves in some regions of ekman upwelling like the tasman sea and near areas of high eddy kinetic energy such as the agulhas retroflection among all features examined by regression analysis bathymetry appears to be the one most consistently correlated with pigments correlation coefficient being about 0 3 for the entire region the cause of negative correlation with bathymetry is unknown but is consistent with the observed abundance of iron in shallow areas in the antarctic region it is also consistent with resuspension of phytoplankton cells by wind induced mixing especially in shallow waters on the other hand in the deep ocean especially at latitudes 30 in average pigment concentration over the entire region during different seasons indicates possible influence of time dependent parameters

controls on mesopelagic particle fluxes in the sub antarctic and polar frontal zones in the southern ocean south of australia in summer perspectives from free drifting sediment traps the saz sense project examined ecosystem controls on southern ocean carbon export during austral summer january february 2007 at three locations p1 in the low biomass subantarctic zone saz west of tasmania p3 in a region of elevated biomass in the saz east of tasmania fuelled by enhanced iron supply and p2 in high nutrient low chlorophyll hnlc polar frontal zone pfz waters south of p1 and p3 sinking particles were collected using i a cylindrical time series pps3 3 trap for bulk geochemical fluxes ii indented rotating sphere irs traps operated as in situ settling columns to determine the flux distribution across sinking rate fractions and iii cylindrical traps filled with polyacrylamide gels to obtain intact particles for image analysis particulate organic carbon poc flux at 150 m pps3 3 trap was highest at p1 lower at p2 and lowest at p3 3 3 1 8 2 1 0 9 and 0 9 0 4 mmol m 2 d 1 respectively biogenic silica bsi flux was very low in the saz 0 2 0 2 and 0 02 0 005 mmol m 2 d 1 at p1 and p3 respectively and much higher in the pfz 2 3 0 5 mmol m 2 d 1 at p2 hence the high biomass site p3 did not exhibit a correspondingly high flux of either poc or bsi separation of sinking rate fractions with the irs traps at 170 and 320 m depth was only successful at the pfz site p2 where a relatively uniform distribution of flux was observed with 1 3 of the poc sinking faster than 100 m d 1 and 1 3 sinking slower than 10 m d 1 analysis of thousands of particles collected with the gel traps at 140 190 240 and 290 m depth enabled us to identify 5 different categories fluff aggregates low density porous or amorphous aggregates faecal aggregates denser aggregates composed of different types of particles cylindrical and ovoid faecal pellets and isolated phyto cells chains and single cells faecal aggregates dominated the flux at all sites and were larger in size at p1 in comparison to p3 the pfz site p2 differed strongly from both saz sites in having a much higher abundance of diatoms and relatively small sized faecal aggregates overall the particle images suggest that grazing was an important influence on vertical export at all three sites with differences in the extents of large aggregate formation and direct diatom export further influencing the differences among the sites

water activity changes across an amphibolite granulite facies transition broken hill australia phase compositions in pelitic and mafic gneisses place tight constraints on pressure ranging from 3 up to 6 kb and to a lesser extent on temperature 500 up to 800 c during prograde regional metamorphism of the willyama complex broken hill se australia these limits allow an evaluation of water activity across the terrain using various equilibria in pelitic and mafic gneisses the stability of cummingtonite and biotite over much of the terrain places upper limits on temperature and the presence of syn metamorphic partial melts in the metasediments places lower limits on a h2o garnet biotitesillimanite k feldspar quartz relations combined with the partial melting data suggest a decrease in water activity from near 1 0 in the lower grade zones to 0 5 0 2 in the broken hill little broken hill part of the two pyroxene zone this result is compatible with less precise hornblende orthopyroxene clinopyroxene quartz relations

an empirical estimate of the southern ocean air sea co2 flux 1 despite improvements in our understanding of the southern ocean air sea flux of co2 discrepancies still exist between a variety of differing ocean atmosphere methodologies here we employ an independent method to estimate the southern ocean air sea flux of co2 that exploits all available surface ocean measurements for dissolved inorganic carbon dic and total alkalinity alk beyond 1986 the dic concentrations were normalized to the year 1995 using coinciding cfc measurements in order to account for the anthropogenic co2 signal we show that independent of season surface normalized dic and alk can be empirically predicted to within 8 mol kg using standard hydrographic properties the predictive equations were used in conjunction with world ocean atlas 2001 climatologies to give a first estimate of the annual cycle of dic and alk in the surface southern ocean these seasonal distributions will be very useful in both validating biogeochemistry in general circulation models and for use in situ biological studies within the southern ocean using optimal co2 dissociation constants we then estimate an annual cycle of pco2 and associated net air sea co2 flux including the effects of sea ice we estimate a southern ocean 50 s co2 sink of 0 4 0 25 pg c yr our analysis also indicates a substantial co2 sink of 1 1 0 6 pg c yr within the sub antarctic zone 40 s 50 s associated with strong cooling and high winds our results imply the southern ocean co2 flux south of 50 s to be very similar to those found by takahashi et al 2002 but on the higher end of a range of atmospheric oceanic co2 inversion methodologies this paper estimates for the first time basic seasonal carbon cycle parameters within the circumpolar southern ocean which have up to now been extremely difficult to measure and sparse the application of such an empirical technique using more widely available hydrographic parameters in the southern ocean provides an important independent estimate to not only co2 uptake but also for other future biogeochemical studies refining and testing these empirical methods with new carbon measurements will be important to further reduce uncertainties and extend our understanding of southern ocean co2 dynamics

ecology and biogeochemistry of the antarctic circumpolar current during austral spring a summary of southern ocean jgofs cruise ant x 6 of r v polarstern the r v polarstern cruise ant x 6 part of the international southern ocean jgofs programme investigated phytoplankton spring bloom development and its biogeochemical effects in different water masses of the atlantic sector of the southern ocean the polar frontal region pfr the southern antarctic circumpolar current zone sacc its boundary with the weddell gyre awb and the marginal ice zone miz the relative roles of physical stability iron limitation and grazing pressure in enhancing or constraining phytoplankton biomass accumulation were examined three sections were carried out between the pfr and the ice edge along the 6 w meridian from early october to late november 1992 this paper summarises the major findings of the cruise and discusses their implications for our understanding of southern ocean ecology and biogeochemistry a major finding was the negligible build up of plankton biomass and concomitant absence of co2 drawdown associated with seasonal retreat of the ice cover in striking contrast to this unexpected poverty of both the miz and the frontal region of the awb distinct phytoplankton blooms dominated by different diatom species accumulated in the pfr chlorophyll stocks in the sacc remained monotonously low throughout the study our findings confirm those of other studies that frontal regions are the major productive sites in the southern ocean and that input of meltwater and associated ice algae to the surface layer from a retreating ice edge is by itself an insufficient condition for induction of phytoplankton blooms the blooms in the pfr developed under conditions of shallow mixing layers high iron concentrations and relatively low grazing pressure however in all three blooms high biomass extended to deeper than 70 m which cannot be explained by either in situ growth or sinking out of a part of the population from the upper euphotic zone subduction of adjoining shallower layers to explain depth distribution is invoked despite a clear co2 drawdown in the polar frontal region the highly variable conditions encountered render reliable estimation of annual co2 fluxes in the southern ocean difficult

eddy induced carbon transport across the antarctic circumpolar current the implications of a mesoscale eddy for relevant properties of the southern ocean carbon cycle are examined with in situ observations we explored carbon properties inside a large 190 km diameter cyclonic eddy that detached from the subantarctic front saf south of tasmania in march 2016 based on remote sensing the eddy was present for 2 months in the subantarctic zone saz an important region of oceanic carbon dioxide co2 uptake throughout the annual cycle and carbon subduction i e where mode and intermediate waters form before it was reabsorbed into the saf the eddy was sampled during the middle of its life 1 month after it spawned comparatively the eddy was 3 c colder 0 5 practical salinity unit fresher and less biologically productive than surrounding saz waters the eddy was also richer in dissolved inorganic carbon dic and had lower saturation states of aragonite and calcite than the surrounding saz waters as a consequence it was a strong source of co2 to the atmosphere with fluxes up to 25 mmol c m 2 d 1 compared to the saf waters from which it originated dic concentration in the eddy was 20 mol kg 1 lower indicating lateral mixing small scale recirculation or eddy stirring with lower dic saz waters by the time the eddy was observed as they are commonly spawned from the antarctic circumpolar current and as 50 of them decay in the saz the rest being reabsorbed by the saf n these types of eddies may represent a significant south north transport pathway for carbon across the acc and may alter the carbon properties of saz waters

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

seasonal variations in foraminiferal flux in the southern ocean campbell plateau new zealand abstract time incremental sediment trap moorings were deployed at two sites across campbell plateau new zealand one in the relatively quiet waters of the plateau interior pukaki rise and the other at the antarctic circumpolar current swept margin eastern campbell flank a continuous record of particle flux over 416 days identifies marked differences in faunal composition and seasonal occurrence in response to these two dynamically different southern ocean settings in the shallow and thermally isolated interior of the pukaki rise site the flux of foraminifera was closely linked to the austral spring pulse of primary production at which time 97 of the total foraminiferal production for the year occurred this seasonal flux of foraminifera at pukaki rise was dominated by the species globorotalia inflata and globigerina bulloides the collapse of phytoplankton production at the end of spring was most likely a result of a co limitation of iron and silicic acid over the deep and dynamic eastern flank of campbell plateau there were four seasonal pulses of foraminiferal flux the largest in spring when almost half of the foraminiferal production occurred most of the spring flux at this site consisted of globorotalia inflata and globigerinita glutinata summer at eastern campbell flank exhibited the lowest flux of foraminifera but the highest species diversity while autumn and winter fluxes were dominated by the deep dwelling globorotalia truncatulinoides although there was only a single pulse of foraminiferal flux at pukaki rise its mass g m 2 d 1 was still greater than that which occurred over the flank summed across all four seasons however the overall standing stock tests m 2 d 1 on the flank was more than twice that which occurred at the pukaki rise site an examination of core top material taken from gravity cores collected in the vicinity of the sediment trap locations revealed typical southern ocean foraminiferal assemblages that were markedly dissimilar in proportion to those observed in the sediment traps

geochemistry of suspended particles in the subantarctic and polar frontal zones south of australia constraints on export and advection processes filtered particles from a southern ocean meridional transect from 42 s to 54 s along 142 e off tasmania were studied between surface and 600 m water depth saz 1998 expedition february april 1998 particulate ba sr ca p u th ti al mn light rare earth elements and zr contents were analyzed by inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectroscopy mesopelagic baxs total ba minus a lithogenic fraction estimated from al contents were higher within the polar front zone pfz in comparison with the northern areas indicating that c export to the intermediate and deep ocean is more important in the pfz average surface uxs versus latitude covaries with mesopelagic baxs contrasting with organic matter proxies such as pp and chlorophyll a this similar behavior suggests that u might be preferentially adsorbed on organic material which subsequently becomes involved with barite precipitation srp and cap contents decrease sharply with depth following total particle content for the northern area 42 47 s surface ce anomaly reflects essentially a lithogenic signature 0 6 ce ce 1 ascribed to the supply from the tasmanian continental shelf suspended matter from surface waters at stations south of 47 s shows an enhanced seawater signature 0 3 ce ce 0 6 in all stations ce anomalies increase with depth toward values close to 1 this is likely due to the increase of lithogenic authigenic ratio of particles with depth rather than redox processes finally an advective event is identified at 45 s below 200 m by a strong increase of lithogenic element contents which affects baxs

groundwater monitoring for earthquake prediction by an amateur network in japan since 1976 groundwater levels and the temperature of thermal water have been monitored in 100 wells distributed mostly in the southern kanto and tokai districts of japan in order to predict earthquakes good examples of groundwater precursors were recognized prior to the following destructive earthquakes the 1978 west off izu oshima earthquake m 7 0 the 1978 off miyagi earthquakes m 7 4 and the 1980 east off izu peninsula earthquake m 6 7 in the 1978 west off izu oshima earthquake groundwater levels and the japan meteorological agency jma volume strainmeters installed in the izu peninsula showed precursory changes at about the same time in the other cases however precursory behavior was observed only in water level and temperature monitoring empirical relations are given between earthquake magnitude and the epicentral distance of the farthest groundwater anomaly and between earthquake magnitude and the precursor time of groundwater

the vertical flux of biogenic and lithogenic material in the ross sea moored sediment trap observations 1996 1998 abstract as part of the usjgofs aesops program we deployed an array of moored sediment traps and determined the composition and vertical flux of particulate matter through the water column of the continental shelf environment of the ross sea we deployed two moorings with two traps each one mooring was located in the southcentral ross sea along the line of aesops process studies the other mooring was located in the northcentral ross sea the flux in the southern ross sea was generally double that in the north and there was a significant increase in flux into the deep traps indicating horizontal transport and possible focusing of particulate matter the particles are primarily biogenic although lithogenic contributions can increase to over 30 of the flux in the near bottom trap nearer to the ice shelf the fluxes collected by the traps were generally low but within the range of previous observations several unique observations stand out from these data 1 the export of organic matter to 200 m during the spring and summer was extremely low consistent with observations that the ongoing phytoplankton bloom was being stored or recycled in the upper water column 2 a major pulse of biogenic silica export occurred in the fall just as ice was reforming the correlation of this event with lithogenous particles excess fe and with the early breakout of katabatic winds suggests that this event might be related to fe fertilization of diatom production and export 3 the largest flux of organic matter during 1996 1997 was carried by the pteropod limacina helicina and was observed at both moorings under the ice in the late fall just after the diatom pulse although it is difficult to estimate the proportion of these organisms that were swimmers contaminating the flux we believe that a significant fraction settled into the traps and may represent the die out of this herbivore population after the suspended pom concentration had dropped to very low levels fluxes to the upper traps were much lower than estimates of export flux made by other methods during synoptic ship studies these differences are discussed and the fluxes are compared with preliminary data from the roaverrs trap program which was simultaneously deployed in the ross sea

reconstruction of paleo particulate organic carbon fluxes for the campbell plateau region of southern new zealand using the zinc content of sponge spicules 1 the zinc concentration of siliceous sponge spicules was determined from spicules recovered from four sediment cores spanning the last 160 kyr from the campbell plateau region southeast of new zealand zinc si results showed little difference between holocene and glacial aged spicules an increase in zn si was observed for core y14 where zn si peaked at about 0 6 mol mol during marine isotope stages 5a 5b to better understand the role carbon export has on sponge zn si we explored the strong relationship observed between surficial sediment particulate organic carbon poc and the zn si of sponge silica and related this to sediment trap poc flux estimates conversion of the zn si records to benthic poc fluxes suggests that there has been little change in the amount of poc reaching campbell plateau sediments over the past 30 kyr these results suggest that surface productivity over the campbell plateau has remained relatively low over the past 160 kyr and suggests that glacial productivity was not significantly higher than the present day finally this work reveals that living marine sponges appear to act as the biological equivalents of moored sediment traps recording the flux of poc to the seafloor by archiving zinc associated with sinking poc in the growing silica skeleton

excess40ar in metamorphic rocks from broken hill new south wales implications for40ar 39ar age spectra and the thermal history of the region 40ar 39ar age spectrum analyses of samples from broken hill new south wales indicate that the region has experienced a complex thermal history following high grade metamorphism 1660 ma ago the terrain cooled slowly 3 c ma 1 until about 1570 ma ago when the temperature fell below about 500 c following granitoid emplacement 1500 ma ago the region remained relatively cold until affected by a thermal pulse 520 40ma ago causing temperatures to rise to 350 c in some places during this event accumulated40ar was released from minerals causing a significant ar partial pressure to develop laboratory ar solubility data combined with the40ar 39ar age spectra gives a local estimate of this partial pressure of 10 4atm the region finally cooled below 100 c about 280 ma ago 40ar 39ar age spectrum analyses of hornblende plagioclase and clinopyroxene containing excess40ar are characterized by saddle shaped age spectra detailed analysis of plagioclase samples reveals a complex diffusion behaviour which is controlled by exsolution structures this effect in conjunction with the presumed different lattice occupancy of excess40ar with respect to radiogenic40ar appears to be responsible for the saddle shaped age spectra

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

mean sea surface height of the antarctic circumpolar current from geosat data method and application the mean sea surface height across the antarctic circumpolar current has been reconstructed from height variability measured by the geosat altimeter without assuming prior knowledge of the geoid for this study an automated technique has been developed to estimate mean sea surface height for each satellite ground track using a meandering gaussian jet model and errors have been estimated using monte carlo simulation the results are objectively mapped to produce a picture of the mean subantarctic and polar fronts which together comprise the major components of the antarctic circumpolar current the meandering jet model explains between 40 and 70 of the height variance along the jet axes the results show that the fronts are substantially steered by topography and that the jets have an average gaussian width of about 44 km in the meridional direction and meander about 75 km to either side of their mean locations the average height difference across the subantarctic front saf is 0 7 m and across the polar front pf 0 6 m the mean widths of the fronts are correlated with the size of the baroclinic rossby radius

seasonal nutrient depletion and carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia seasonal surface water nitrate and phosphate depletions were calculated for the subantarctic zone saz and polar frontal zone pfz of the southern ocean along the world ocean circulation experiment sr3 repeat section south of tasmania australia and three other transects slightly to the west the depletions were calculated between a single winter july section and eight other sections from october to march in the years 1991 1998 and corrected for frontal movements and changes in water masses between the cruises using observed quasi linear nutrient salinity relationships arranged in a seasonal progression depletion began in approximately october and continued through march in good agreement with satellite biomass based estimates of production nitrate depletion in the saz 510 mmol n m 2 was approximately twice that of the pfz 250 mmol n m 2 but phosphate depletions were similar 29 and 24 mmol p m 2 for the saz and pfz respectively the saz exhibited a redfield n p depletion ratio 15 1 2 3 but the pfz ratio was much lower 8 3 5 4 while the saz exhibits greater seasonal nutrient depletion the relative magnitudes of export in the two zones remain uncertain because supply of nutrients from south of the polar front may lower the observed nutrient depletions in the pfz however comparisons with sediment trap and production measurements for the region south of australia suggest the saz and pfz differences derive from differences in production assuming a redfield c n ratio 6 6 carbon export for the longest period examined july march averaged 3400 430 mmol c m 2 in the saz with a range between 2700 and 3900 mmol c m 2 depending on latitude in the pfz carbon export averaged 1600 350 mmol c m 2 with a range of 1100 to 2000 mmol c m 2 these averages represent minimum annual export production estimates because neither resupply nor export outside the july march observational period is included

particle fluxes to the interior of the southern ocean in the western pacific sector along 170 w abstract an array of five bottom tethered moorings with 19 parflux time series sediment trap at three depths 1 and 2 km below the surface and 0 7 km above the sea floor was deployed in the western pacific sector of the southern ocean along 170 w the five stations were selected to sample settling particles in the main hydrological zones of the southern ocean the sampling period spanned 425 days november 28 1996 january 23 1998 and was divided into 13 or 21 synchronized time intervals a total of 174 sequential samples were recovered and analyzed to estimate fluxes of total mass tmf organic carbon carbonate biogenic silica and lithogenic particles the fluxes of biogenic material were higher than anticipated challenging the notion that the southern ocean is a low productivity region organic carbon fluxes at 1 km depth within the polar frontal zone and the antarctic zone were relatively uniform 1 7 2 3 g m 2 yr 1 and about twice the estimated ocean wide average ca 1 g m 2 yr 1 carbonate fluxes were also high and uniform between the subantarctic front and ca 64 s 11 13 g m 2 yr 1 a large fraction of the carbonate flux in the antarctic zone was due to the presence of pteropod shells coccoliths were found only to the north of the polar front and calcium carbonate became the dominant phase in the subantarctic zone in contrast carbonate particles were nearly absent near 64 s latitudinal variations in biogenic silica fluxes were substantial the large opal flux 57 g m 2 yr 1 measured in the antarctic zone suggests that opal productivity in this region has been previously underestimated and helps to explain the high sedimentary opal accumulation often found south of the polar front unlike biogenic material fluxes of lithogenic particles were among the lowest measured in the open ocean 0 12 0 05 g m 2 yr 1 reflecting a very low dust input

anomalous water level changes and possible relation with earthquakes since late 1976 abandoned water wells have been monitored along the san andreas and san jacinto faults to detect water level changes which may be premonitory to earthquakes an m5 5 earthquake occurred 25 february 1980 within the san jacinto fault zone near anza the water level in a continuously recorded well in borrego valley 35 km from the epicenter rose 0 5 m and returned to its prior level during a four hour period beginning 88 hours before the earthquake the water level in this well had been remarkably steady compared to other wells being monitored another well in borrego valley showed a much smaller rise and fall in water level at the same time because these changes are unique for the long term records of these wells they may represent precursors to the earthquake several wells along the palmdale valyermo segment of the san andreas fault showed possibly anomalous long term water level changes which are not clearly related to rainfall between early 1979 and early 1980 water levels in six wells were 6 to 4 5 m higher and levels in two wells were about 3 m lower than would have been predicted based on the previous records the water level increases could have been the result of delayed response to seasonal rainfall following a long drought however it is interesting that the possibly anomalous water level changes first occurred at the same time as the reported changes in strain pattern from compression to expansion along the san andreas fault in the same area

controls on biogenic silica burial in the southern ocean understanding the controls on opal export in the southern ocean can inform both the prediction of how the leakage of silicic acid from the southern ocean responds to climate and the interpretation of paleo proxies we have compiled a database of 185 230thorium normalized opal burial rates and 493 opal concentration measurements in southern ocean sediments and matched these with environmental climatologies by subdividing the southern ocean on the basis of oceanographic regions and interpolating the opal burial rates we estimate a total biogenic si burial south of 40 s of 2 3 1 0 tmol si yr 1 in both the seasonally ice covered and permanently ice free regions we can explain 73 of opal burial variability from surface ocean properties where sea ice is present for at least part of the year the length of the ice free season determines the upper limit of opal burial in the underlying sediments in the ice free regions of the southern ocean the supply of silicic acid through winter mixing is the most important factor our results do not support a strong role of iron in controlling opal burial we do however find that satellite derived net primary production increases with increasing modeled dust delivery these findings support the decoupling between carbon and opal fluxes in the southern ocean when corrected for opal dissolution the observed opal fluxes are in reasonable agreement with fluxes simulated using an ocean biogeochemical model however the results suggest current preservation algorithms for opal could be improved by incorporating the composition of particle flux not only its magnitude

planktonic foraminiferal δ13c records from southern ocean sediment traps new estimates of the oceanic suess effect the carbon isotopic composition is measured for three species of planktonic foraminifera globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s from southern ocean sediment traps the sediment traps represent the annual flux of foraminifera in subtropical to polar frontal environments from the western pacific southern australia sector comparison between the seasonal 13c composition of the foraminifera and estimated 13c of dissolved inorganic carbon dic allows disequilibrium effects to be determined disequilibrium exhibits a latitudinal trend with greatest offsets from equilibrium at lower latitudes this effect causes a north to south increase in foraminiferal 13c while the 13cdic displays a decrease across these latitudes disequilibrium in g bulloides can be accounted for by changes in temperature the relationship between disequilibrium and temperature which we derive in this field study is consistent with the laboratory relationship of bemis et al 2000 corrected 13c for g bulloides is closely correlated to seasonal changes in nutrients at each site indicating the utility of g bulloides 13c as a nutrient tracer in southern ocean environments comparison between flux weighted sediment trap values and nearby core tops indicates a modern depletion in 13c which we attribute to the oceanic suess effect the imprint of this effect on the foraminiferal isotopes provides further evidence for the equilibration between surface waters and the atmosphere in the subantarctic zone

planktonic foraminiferal flux seasonality in subantarctic sediment traps a test for paleoclimate reconstructions sediment trap moorings deployed during 1997 and 1998 in the subantarctic to polar frontal regions of the southern ocean reveal distinct seasonality in foraminiferal flux foraminiferal assemblages vary between each site yet major species exhibit very similar patterns of seasonal succession which can be associated with changes in mixed layer depth enhanced foraminiferal productivity is also associated with periods of high biogenic silica and particulate organic carbon flux on a broader scale foraminiferal assemblages are strongly delineated by temperature temperature estimates derived from the assemblages using the modern analog technique mat are mostly within 2 5 c of the satellite advanced very high resolution radiometer temperatures observed during the deployment period this indicates that core top sediments included in the mat database do reflect modern observed conditions at the sea surface providing a robust technique for estimating past temperature change from foraminiferal assemblages in southern ocean environments

high biomass low export regimes in the southern ocean high biomass low export regimes in the southern ocean phoebe j lam 1 2 and james k b bishop 1 earth sciences division lawrence berkeley national laboratory 1 cyclotron road berkeley ca 94720 usa department of earth and planetary science university of california berkeley berkeley ca 94720 usa now at department of marine chemistry and geochemistry woods hole oceanographic institution woods hole ma 02543 submitted january 27 2006 to deep sea research ii special topics in oceanography special volume on the role of marine organic carbon and calcite fluxes in driving climate change past and future revised version accepted june 28 2006 keywords ballast remineralization poc twilight zone mesopelagic southern ocean mulvfs opal carbonate phosphorus

circulation and seasonal evolution of polar waters south of australia implications for iron fertilization of the southern ocean abstract the southern ocean iron release experiment soiree was carried out in late summer february 1999 south of australia 61 s 140 e this region of the southern antarctic zone az s between the southern branch of the polar front pf and the southern front of the antarctic circumpolar current saacf is characterized by weak currents and is remote from the influence of sea ice or coastal waters the soiree site exhibits high nutrient concentrations year round phosphate nitrate and silicate remain above 10 m low chlorophyll accumulations

modeling the geochemical cycle of iron in the oceans and its impact on atmospheric co2 concentrations iron occurs at very low concentrations in seawater and seems to be a limiting factor for primary production in the equatorial pacific and the southern ocean the global distribution of iron is still not well understood because of a lack of data and the complex chemistry of iron we develop a 10 box model to study the oceanic distribution of iron and its effect on atmospheric co2 concentration subject to our assumptions we find that a lack of interocean fractionation of deep sea iron concentrations as suggested by johnson et al 1997a is not readily explained by a balance of eolian deposition scavenging and regeneration incorporation of organic complexation in the model as suggested by johnson et al to reduce the scavenging rate of iron when concentrations fall below some ligand stabilized concentration is one solution to this difficulty alternatively the deep sea concentration may be more variable than the current rather sparse data coverage suggests in the model deep sea iron concentrations are responsive to the atmospheric source even if we adopt stabilization of concentrations by a ligand as modeled by johnson et al l997a in the southern ocean where the model suggests iron supply has an important limiting effect on the biota more than 99 of the iron supply to the surface in the present day comes from upwelling and not from the local atmospheric flux in the context of glacial interglacial changes to atmospheric co2 the model suggests that increasing atmospheric iron to the entire global ocean by a factor of 2 leads to decreases in atmospheric co2 of 10 30 ppm depending on assumptions however in our model co2 concentrations are almost unaffected by changes in southern ocean atmospheric fluxes alone unless these are unrealistically large 100 times present day the effect on atmospheric carbon dioxide is slightly stronger if accompanied by increased stratification of the southern ocean the model suggests that eolian iron fertilization of the ocean could have importantly influenced glacial atmospheric co2 concentrations but that other processes must also be at work to account for the full magnitude of the glacial interglacial change