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

trace metal concentrations in the ross sea and their relationship with nutrients and phytoplankton growth abstract dissolved and particulate trace metal concentrations dissolved fe zn cd co cu and ni particulate fe mn and al were measured along two transects in the ross sea during austral summer of 1990 total fe concentrations in southern ross sea and inshore waters were elevated 3 5 times that of northern waters dissolved zn cd and co concentrations were lower by factors of 4 5 3 5 and 1 6 in southern surface waters relative to northern waters dissolved cu and ni concentrations were similar in both areas elevated fe concentrations coincided with areas of increased productivity phytoplankton biomass and nutrient drawdown indicating that fe is an important factor controlling the location of phytoplankton blooms in the ross sea particulate concentrations of fe mn and al indicate two possible sources of iron to the ross sea resuspension of continental shelf sediments and iron incorporated in annual sea ice and released with meltwaters

quartz grains reveal sedimentary palaeoenvironment and past storm events a case study from eastern baltic abstract sediment record collected from the coastal lake serves as a powerful tool for reconstructing changes in palaeoenvironment and understanding the potential signals of past storminess in this study we use several proxies from sediment of the holocene thermal maximum at coastal lake lilaste latvia we focus on surface texture of quartz grains from the mineral inorganic fraction as indicators of depositional environments we then use this as a proxy for potential storm transport and combine with information on granulometry diatom stratigraphy and chronology to answer the question whether flux of quartz grains in the lake originated from the sea or from the land analyses in a binocular and scanning electron microscope reveal that most of the investigated quartz grains originate from dwelling in the seawater and wave action in the nearshore zone grains representing very energetic subaqueous environment similar to storm events are also present terrestrial record is of minor significance and visible through occurrence of aeolian quartz grains during drier and colder conditions an influx of sand with aeolian imprint was delivered to the lake between 8500 and 7800 cal yr bp marine and terrestrial conditions alternated between 7800 and 6000 cal yr bp storm induced grains were likely deposited three times at 7300 cal yr bp 6600 6400 cal yr bp and 6200 6000 cal yr bp overall stable marine environmental conditions prevailed between 6000 and 4000 cal yr bp except of the last portion of terrestrial induced sediment at 4100 cal yr bp

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

iron solubility driven by speciation in dust sources to the ocean particulate aerosols are thought to be the primary source of iron to the oceans but the factors determining their solubility and thus bioavailability are unclear x ray absorption analysis reveals that speciation controls the solubility of iron in three large sources of aerosol iron

three dimensional characterization of sand grain shape and surface texture using a nitrogen gas adsorption technique abstract shape and surface texture are fundamental characteristics of sand grains which have long been used by sedimentologists to provide information about grain provenance transport pathways and postdepositional weathering hitherto most work on the gross aspects of grain shape sphericity roundness or angularity has been undertaken on two dimensional digitized grain images analyzed by fourier or fractal methods or simple shape factor measurements and studies of grain surface textures have mainly involved qualitative or semiquantitative recording of the relative abundance of a number of discrete surface textural features here we describe a new nitrogen gas adsorption technique that can be used to provide information on three dimensional shape and surface texture with very high precision and to test hypotheses about sediment sources and postdepositional alteration the method has been tested on a range of sandy sediments from around the world and found to provide a useful quantitative measure of the shape and surface texture of different sediments provided that strict protocols are observed in sample preparation

microtextural characteristics of quartz grains transported and deposited by tsunamis and storms article i nfo the complex transport and depositional processes associated with tsunamis and storms and the peculiarities of local inundation present questions associated with the recognition and differentiation of the sedimentary signature of these events this work presents a study of quartz grains transported and deposited by tsunami and storm waves with the objective of identifying specific microtextural signatures caused by high energy marine inundations and to correlate them with their principal sedimentary sources in this empirical study 1150 quartz grains 78 samples and their microtextural signatures were observed analyzed and classified using scanning electron microscope photomicrographs the results suggest that although no specific microtextural signature is associated with high energy inundations there are strong increases in the percent age of fresh surfaces and percussion marks when compared with the potential source material moreover tsunami and storm grains present the greatest microtextural variance among all the grains analyzed never theless specific local conditions and sediment concentrations constrain the microtextural implications on tsunami or storm grains one laboratory experiment was designed to test microtextural implications in grains subjected to variable velocities sediment concentration and time the surface microscopic signature in quartz grains of high energy events further contributes to the development of more efficient sedimentological criteria to identify deposits associated with tsunami and storm events

fe and h2o2 distributions in the upper water column in the indian sector of the southern ocean total dissolvable iron tdfe particulate iron pfe and hydrogen peroxide h2o2 measurements were performed along a n s transect in the upper 250 m in the southern ocean 62 00e 66 42s 49 00s antares ii cruise february 1994 tdfe was organically extracted apdc dddc chloroform and analysed by graphite furnace atomic absorption spectrometry gfaas pfe was analysed by gfaas following a strong mixed acid leach and h2o2 was analysed on board by fluorometry the respective detection limits are equal to 0 13 nmol kg 0 02 nmol kg and 3 0 nmol kg tdfe concentrations vary from 0 4 to 6 2 nmol kg and profiles are not completely depleted in the surface pfe concentrations vary from 0 02 to 0 2 nmol kg iron carbon fe c uptake ratios for phytoplankton were calculated either from seawater or particle measurements they are variable along the transect but are consistent when they could be compared all the observed ratios are within the range of values proposed for the fe c uptake ratios by phytoplankton using our uptake ratio calculated in the permanent open ocean zone 4 10 6 mol mol we estimate that the primary production which can be supported by the iron input flux into the surface waters is two times higher than the measured primary production in the same area in the surface waters h2o2 concentrations vary from 5 0 to 19 7 nmol kg such low concentrations are due to strong vertical mixing low dissolved organic matter concentrations and the latitude of the site

direct measurements of atmospheric iron cobalt and aluminum derived dust deposition at kerguelen islands 1 atmospheric deposition is one of the major sources of nutrients bringing trace metals to remote marine biota in this study total atmospheric deposition and crustal aerosol concentrations were monitored at kerguelen islands 49 18 s 70 07 e in the southern ocean during a short campaign in early 2005 and then continuously for about 2 years 2009 2010 results show very low levels of atmospheric dust and trace metals concentrations but higher deposition fluxes than expected the averaged total dust deposition flux as derived from al deposition measurements is 659 g m 2 d 1 simultaneously measured fe and co deposition fluxes are respectively 29 g m 2 d 1 520 nmol m 2 d 1 and 0 014 g m 2 d 1 0 24 nmol m 2 d 1 giving typically crustal elemental ratios to al of 0 54 and 2 6 10 4 measured dust deposition is in relatively good agreement with those simulated by current atmospheric models but suggest that previous indirect calculations from field experiments are too low by a factor of 20 observations and model results show that dust is transported above the marine atmospheric boundary layer to kerguelen islands and thus that surface concentrations are not representative of the total dust column indeed using surface concentrations leads to very large computed wet scavenging ratios and to the conclusion that it is not appropriate to derive deposition fluxes from surface concentrations at remote ocean sites

the use of fourier descriptors in the classification of particle shape a new quantitative method for characterizing quartz grain shape is presented the method employs a harmonic analysis based upon fourier descriptors which is a distinct variation of the traditional and widely used fourier series quartz grain images from a scanning electron microscope were frame grabbed and converted to a digitized grey level image the image processing techniques of enhancement segmentation and boundary tracking were applied to remove all features except the image boundary this boundary was sampled at uniform intervals of are length and represented mathematically on the complex plane in this way problems associated with the location of particle centroid and re entrant values were avoided the resulting data was standardized relative to scale rotation and starting position hence the discrete fourier transform was applied using modern fast fourier transform techniques and the modulus of the resulting harmonic amplitude used to characterize the grain shape the technique was applied to a sample of 0 5 m quartz grains from three distinct populations desert quartz beach grains fire island new york and brazilian crushed quartz whilst plots of average amplitude vs harmonic number for each population appeared similar discriminant analysis applied to each grain sample distinguished characteristic grain shape with an excellent degree of success the problems of location of the centroid and re entrant values were eliminated this allowed the technique to be applied to a much wider group of irregularly shaped sedimentary particles such as loess

the active portion of the campi flegrei caldera structure imaged by 3 d inversion of gravity data 1 we present an improved density model and a new structural map of the neapolitan yellow tuff caldera the active portion of the nested campi flegrei caldera the model was built using a new 3 d inversion of the available high precision gravity data and a new digital terrain and marine model the inversion procedure based on a variable depth lumped assembling of the subsurface gravity distribution via cell aggregation gives better defined insights into the internal caldera architecture that well agree with the available geological geophysical and geochemical data the adopted 3 d gravity method is highly efficient for characterizing the shallow caldera structure down to 3 km depth and defining features related to regional or volcano tectonic lineaments and dynamics in particular the resulting density distribution highlights a pronounced density low in correspondence of the central portion of the caldera with a detail not available till now the joint interpretation of the available data suggests a subsurface structural setting that supports a piecemeal collapse of the caldera and allows the identification of its headwall positive gravity anomalies localize dense intrusions presently covered by late volcanic deposits along the caldera marginal faults and the main structural lineaments both bordering the resurgent block and cutting the caldera floor these results allow us to both refine the current geological structural framework and propose a new structural map that highlights the caldera boundary and its internal setting this map is useful to interpret the phenomena occurring during unrest and to improve both short term and long term volcanic hazards assessment

provenance of multicycle quartz arenites of pliocene age at arcos southwestern spain abstract a typical deposit of multicycle quartz arenites of considerable economic significance located in arcos sw spain has been studied to establish the provenance of the grains and their stages of sedimentary evolution the quartz grains were studied by sem and the composition of the sand determined by modal analysis of the heavy and light minerals the sources of the silica sands were the numidic sandstones known as aljibe in the betic cordilleras and the late miocene calcarenites of the guadalquivir basin four phases in the evolution of the arcos quartzose sands are a the initial surface features upturned plates b mechanical features an association of conchoidal fractures and arcuate steps formed in littoral environments inherited from the late miocene calcarenites c fluviatile features such as mechanical v s and grooves and d a final stage of chemical features oriented etch pits solution pits and hollows and silica globules developed in a hot humid climate the most important process producing the enrichment of the quartzose sands takes place during erosion depositional cycles

southwest pacific ocean response to a warming world using mg ca zn ca and mn ca in foraminifera to track surface ocean water masses during the last deglaciation in situ measurements of mg ca zn ca mn ca and ba ca in globigerinoides bulloides and globigerina ruber from southwest pacific core top sites and plankton tow are reported and their potential as paleoproxies is explored the modern samples cover 20 degrees of latitude from 34 degrees s to 54 degrees s 7 19 degrees c water temperature and variable influence of subantarctic saw and subtropical stw surface waters trace element signatures recorded in core top and plankton tow planktic foraminifera are examined in the context of the chemistry and nutrient profiles of their modern water masses our observations suggest that zn ca and mn ca may have the potential to trace saw and stw intraspecies and interspecies offsets identified by in situ measurements of mg ca and zn ca indicate that these ratios may also record changes in thermal and nutrient stratification in the upper ocean we apply these potential proxies to fossilized foraminifera from the high resolution core md97 2121 at the last glacial maximum surface water mg ca temperature estimates indicate that temperatures were approximately 6 7 degrees c lower than those of the present accompanied by low levels of mn ca and zn ca and minimal thermal and nutrient stratification this is consistent with regional dominance of saw and reduced stw inflow associated with a reduced south pacific gyre spg upper ocean thermal and nutrient stratification collapsed during the antarctic cold reversal before poleward migration of the zonal winds and ocean fronts invigorated the spg and increased stw inflow in the early holocene together with reduced winds this favored a stratified upper ocean from circa 10ka to the present

spatial and particle size distributions of atmospheric dissolvable iron in aerosols and its input to the southern ocean and coastal east antarctica 1 to characterize atmospheric dissolvable iron over the southern ocean so and coastal east antarctica cea bulk and size segregated 0 056 18 m in diameter aerosols were collected from 34 s 109 e to 69 s 76 e and between 69 s 76 e and 66 s 110 e during a cruise during november 2010 to march 2011 aerosols were analyzed for total dissolvable fe and fe ii by uv visible spectroscopy and total fe by inductively coupled plasma mass spectrometry the average concentrations of total fe were 19 ng m 3 range 10 38 ng m 3 over the so and 26 ng m 3 range 14 56 ng m 3 in cea the average fe ii concentrations were 0 22 ng m 3 range 0 13 0 33 ng m 3 over the so and 0 53 ng m 3 range 0 18 1 3 ng m 3 over cea the total dissolvable fe followed the same trend over the so a single peak size distribution of fe ii existed over cea a bimodal size distribution of fe ii appeared with the first peak at 0 32 0 56 m and the second peak at 5 6 10 m higher fe concentrations over cea than over the so and the existence of coarse mode fe ii over cea suggest potential dust sources in antarctica the fractional fe ii solubility ranged from 0 58 to 6 5 and decreased with total fe concentration increase the estimated atmospheric fluxes of fe ii were 0 007 0 092 mg m 2 yr 1 over the so and 0 022 0 21 mg m 2 yr 1 in cea total dissolvable fe fluxes were 0 007 0 52 mg m 2 yr 1 over the so the atmospheric dissolvable fe input contributes to the dissolved fe pool in the so surface waters

scanning electron microscope evidence for offshore onshore sand transport at fire island new york usa balancing the sediment budget of the atlantic shoreline of long island has proved to be problematic because more sediment has been found to be moving westward in littoral drift than was estimated to be supplied by wave erosion of the ronkonkoma terminal moraine at montauk point there is a need for the existence of an additional possibly offshore source as part of a larger atlantic shore study 11 beach samples from fire island were compared with samples representing the known glacial source at montauk point and also with four offshore samples to the south comparisons were based upon quartz sand grain surface texture patterns derived by scanning electron microscope checklist analysis initial evidence of an offshore onshore link was provided by qualitative results examining surface texture variability between samples illustrated by photographic evidence and written notes this evidence was confirmed consistently during quantitative analysis in particular canonical variate analysis grouped two offshore samples representing deposits of buried glacial to fluvioglacial lobes with beach samples from fire island in adjacent onshore locations or slightly downdrift in addition canonical variate analysis and factor analysis using the spssx package together with cluster analysis using the arthur package depicted the main factors and texture variables largely responsible for sample discrimination the significance of both the offshore onshore link and the associated factors influencing quartz grain surface texture was revealed by the fact that they are strongly related to each other and to the regional geomorphology

fecycle attempting an iron biogeochemical budget from a mesoscale sf6 tracer experiment in unperturbed low iron waters 1 an improved knowledge of iron biogeochemistry is needed to better understand key controls on the functioning of high nitrate low chlorophyll hnlc oceanic regions iron budgets for hnlc waters have been constructed using data from disparate sources ranging from laboratory algal cultures to ocean physics in summer 2003 we conducted fecycle a 10 day mesoscale tracer release in hnlc waters se of new zealand and measured concurrently all sources with the exception of aerosol deposition to sinks of iron from and rates of iron recycling within the surface mixed layer a pelagic iron budget timescale of days indicated that oceanic supply terms lateral advection and vertical diffusion were relatively small compared to the main sink downward particulate export remote sensing and terrestrial monitoring reveal 13 dust or wildfire events in australia prior to and during fecycle one of which may have deposited iron at the study location however iron deposition rates cannot be derived from such observations illustrating the difficulties in closing iron budgets without quantification of episodic atmospheric supply despite the threefold uncertainties reported for rates of aerosol deposition duce et al 1991 published atmospheric iron supply for the new zealand region is 50 fold i e 7 to 150 fold greater than the oceanic iron supply measured in our budget and thus was comparable i e a third to threefold to our estimates of downward export of particulate iron during fecycle the fluxes due to short term hours biological iron uptake and regeneration were indicative of rapid recycling and were tenfold greater than for new iron i e estimated atmospheric and measured oceanic supply giving an fe ratio uptake of new iron uptake of new regenerated iron of 0 17 i e a range of 0 06 to 0 51 due to uncertainties on aerosol iron supply and an fe ratio biogenic fe export uptake of new regenerated iron of 0 09 i e 0 03 to 0 24

environmental discrimination based on quartz grain surface textures a statistical investigation the relative abundance of thirty two surface features identified on the surfaces of quartz sand grains from eight coded samples was noted independently by five scanning electron microscopists these data reduced to binary form were the subject of canonical variate analyses which discriminated clearly between all samples thirteen variables were important in distinguishing between the eight samples this indicates that there are no single key surface features which on their own would allow rapid environmental discrimination the contention that a multiplicity of surface features should be recorded for the purpose of environmental discrimination is therefore upheld operator variance although considerable in the recognition of individual surface features is negligible in discrimination of samples based on binary data the sem technique of analysis of quartz grain surface textures is a reliable and statistically valid means of discriminating between samples from different environments

quartz grain surface textures and depositional interpretations nile delta region egypt abstract this study using the scanning electron microscope sem identifies the assemblages of quartz grain surface textures in sands from six modern environments in the northeastern nile delta and adjoining regions of egypt differences in the proportions of mechanical and chemical features serve to distinguish aeolian dominated settings desert coastal dunes from subaqueous ones the assemblage of surface features also serves to identify open marine nearshore offshore shelf beach and river sands the sem results show a considerable overlap in the types of surface features from environment to environment as might be expected in this deltaic system where sediment has been recycled between markedly different dune fluvial coastal marine settings in some cases this overlap phenomenon complicates the correlation of subsurface sand layers of late pleistocene and holocene age between cores nevertheless the present investigation shows that identification of surface textures in the nile delta is most helpful in interpreting subsurface layers in cores such as those of river and dune origin i e those quartz rich sands that otherwise are usually devoid of depositionally diagnostic mineralogical faunal and floral components

a pliocene mega tsunami deposit and associated features in the ranquil formation southern chile abstract an exceptionally large tsunami affected the coastline of southern chile during the pliocene its backflow eroded coarse beach and coastal dune sediments and redistributed them over the continental shelf and slope sandstone dykes and sills injected from the base of the resulting hyperconcentrated flow into underlying cohesive muds assisted in plucking up large blocks of the latter and incorporating them into the flow locally the rip up intraclasts were fragmented further by smaller scale injections to form a distinct breccia of angular to rounded mudstone clasts within a medium to coarse sandstone matrix sandstone sills in places mimic normal sedimentary beds complete with structures resembling inverse gradation planar laminae as well as ripple and trough cross lamination these were probably formed by internal sediment flow and shear stress as the semi liquefied sand was forcefully injected into cracks in borehole cores such sills can easily be misinterpreted as normal sedimentary beds which can have important implications for hydrocarbon exploration

distributions of dissolved and particulate iron in the sub antarctic and polar frontal southern ocean australian sector this paper presents iron fe profiles in the upper 1000 m from nine short term transect stations and three long term process stations occupied in the australian sector of the southern ocean during the saz sense expedition in austral summer january february 2007 strong vertical and horizontal gradients in fe concentrations were observed between the 18 sampled profiles i e 0 09 0 63 nmol l dissolved fe dfe average dfe concentrations in surface gggwaters in the northern sub antarctic zone saz n west station p1 were 0 2770 04 nmol l this is lower in the saz n east region station p3 and around where average dfe values in the mixed layer were 0 4870 10 nmol l the polar front pf station p2 exhibited the lowest average surface fe values i e 0 2270 02 nmol l iron concentrations in deep waters down to 1000 m were more uniform 0 25 0 37 nmol l dfe which is in accordance with values reported elsewhere in remote waters of the southern ocean but lower than those observed in the north atlantic and north pacific basins a strong decoupling was observed between dfe and nutrient cycles at all stations particulate fe levels were generally very low for all saz stations o0 08 1 38 nmol l with higher values observed at stations collected near tasmania and in the saz n east region the intrusion of subtropical waters enriched with fe from sediments or dust further north is thought to mediate fe input to the saz n and stz areas while input from below would be the main source of fe in the pf region we applied the tracer fen fen dfe rfe p po4 3 where rfe p is the algal uptake ratio to estimate the degree to which the water masses were fe limited in this study fen tended to be negative and decreased with increasing depths and latitude positive fen values indicating fe sufficiency were observed in the near surface waters collected in the saz n east and near continental sources where primary production was higher and ultimately limited by the lack of macro nutrients not fe micro organisms residing in the saz n west and pf on the other hand experienced negative fen indicating a strong co limitation by low silicic acid concentration and fe supply and light in the case of pf

biogeochemistry of iron in australian dust from eolian uplift to marine uptake 1 dust is an important vector for iron supply to the ocean which subsequently impacts ocean productivity atmospheric co2 concentrations and hence global climate here we synthesize the processes influencing the biogeochemistry of australian dust and compare them with those from other southern hemisphere dust sources our observations range from soil and dust physical properties to abrasion and cloud chamber chemistry experiments to dust storms and their dispersion and deposition we then present satellite observations of the impact of episodic dust deposition events on the productivity of low iron oceanic waters north i e low nitrate low chlorophyll lnlc and south i e high nitrate low chlorophyll hnlc of australia dust deposition from the largest dust storm in over 40 years did not result in iron mediated algal blooms in either oceanic region a comparison of australia with other southern hemisphere source regions reveals that the relatively well sampled australian system is a poor generic model furthermore there are marked distinctions between southern and northern hemisphere iron dust biogeochemistry that must be recognized by modelers and included in future simulations better information is required on the relative role of the atmosphere and ocean on influencing iron biogeochemistry and how their relative influences might change in the future due to climate change

analysis of barrier island surface sediments by scanning electron microscopy abstract the analysis of quartz grain surface microtextures from a sedimentary environment where grain transport and depositional pathways were closely interconnected allowed insight into subtle microfeature alteration during movement between subenvironments four fire island new york and one montauk point beach sample were analysed principally through use of a checklist approach using 36 common surface features beach overwash floodtidal delta dune and inlet grains displayed similar surface features only the latter two samples displaying distinctive microtextural patterns the pattern of development of inlet grains was related to the application of higher shear stresses on the grains during transport in the shallow channel the results from dune grains testify to the effectiveness of aeolian transport mechanisms in rapidly altering existing features glacially derived microtextures altered by subsequent subaqueous action were prevalent but whether these glacial microfeatures are derived from the headland region montauk point or from a closer offshore glacial lobe source is not determined comparison of offshore lobe and adjacent sediments revealed contrasting surface and morphological differences statistical treatment of checklist data in binary form 1 0 using stepwise discriminant analysis proved workable but more rigorous testing is required to prove its relevance and use in deciphering raw textural data

natural iron fertilization of the atlantic sector of the southern ocean by continental shelf sources of the antarctic peninsula in large parts of the southern ocean primary production is limited due to shortage of iron fe we measured vertical fe profiles in the western weddell sea weddell scotia confluence and antarctic circumpolar current acc showing that fe is derived from benthic fe diffusion and sediment resuspension in areas characterized by high turbulence due to rugged bottom topography our data together with literature data reveal an exponential decrease of dissolved fe dfe concentrations with increasing distance from the continental shelves of the antarctic peninsula and the western weddell sea this decrease can be observed 3500 km eastward of the antarctic peninsula area downstream the acc we estimated dfe summer fluxes into the upper mixed layer of the atlantic sector of the southern ocean and found that horizontal advection dominates dfe supply representing 54 15 of the total flux with significant vertical advection second most important at 29 13 horizontal and vertical diffusion are weak with 1 2 and 1 1 respectively the atmospheric contribution is insignificant close to the antarctic continent but increases to 15 10 in the remotest waters 1500 km offshore of the acc translating southern ocean carbon fixation by primary producers into biogenic fe fixation shows a twofold excess of new dfe input close to the antarctic continent and a one third shortage in the open ocean fe recycling with an estimated fe ratio of 0 59 is the likely pathway to balance new dfe supply and fe fixation

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

a comparative sem study on the micromorphology of glacial and nonglacial clasts with varying age and lithology preliminary research on striated clasts from a variety of depositional environments suggests that scanning electron microscopy sem of striated clasts of varying lithology in diamictons may prove useful in interpreting a glacial origin evaluating whether sem analysis of clasts from diamictons is an applicable technique to define a glacial origin requires a better understanding of the microfeatures occurring on glacial and nonglacial clasts we describe microtextures and surface characteristics for samples of quartzite granite limestone basalt chert pillow basalt and quartz pebbles collected from a variety of depositional environments our study suggests that it is possible to differentiate between glacial and nonglacial deposits based on frequency and morphology of diagnostic surface microfeatures observed on entrained clasts these microfeatures are best preserved and identified on competent and monomineralic samples e g quartzite chert limestone and poorly preserved on less resistant and p

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

iron transport by mesoscale haida eddies in the gulf of alaska abstract a two year study of the iron distributions in anticyclonic mesoscale haida eddies of the eastern north pacific ocean has shown that such eddies are a major source of iron to the high nitrate low chlorophyll hnlc waters of the central gulf of alaska basin these eddies which are typically about 100 km in diameter form off the west coast of canada in winter and then track roughly westward into the open ocean therefore they carry large quantities of iron rich coastal waters into iron limited waters of the oligotrophic gyre when the eddies had first formed their dissolved iron concentrations were nearly two orders of magnitude higher than is typically observed at station papa 50 n 145 w 3 n m versus less than 0 05 n m and the total iron in the eddies surface waters 10 40 m was more than 13 n m higher than open ocean waters of the alaska gyre 14 n m versus 0 5 n m while the overall iron content of the eddies decreased rapidly during the first year after they formed the eddy we were able to track the longest still contained 1 5 2 times more iron than the surrounding waters 16 months after its formation therefore although iron concentrations in the surface mixed layers of the eddies drop to levels observed outside very rapidly within 4 months upward transport along isopycnals and upwelling due to eddy decay as well as vertical advective and diffusive transports typical of north pacific waters probably provide steady fluxes of iron into the euphotic zone from the still iron rich eddy core waters throughout the lifetime of the eddy

limitation of algal growth by iron deficiency in the australian subantarctic region in march 1998 we measured iron in the upper water column and conducted iron and nutrient enrichment bottle incubation experiments in the open ocean subantarctic region southwest of tasmania australia in the subtropical convergence zone 42 s 142 e silicic acid concentrations were low 1 5 m in the upper water column whereas pronounced vertical gradients in dissolved iron concentration 0 12 0 84 nm were observed presumably reflecting the interleaving of subtropical and subantarctic waters and mineral aerosol input results of a bottle incubation experiment performed at this location indicate that phytoplankton growth rates were limited by iron deficiency within the iron poor layer of the euphotic zone in the subantarctic water mass 46 8 s 142 e low concentrations of dissolved iron 0 05 0 11 nm and silicic acid 1 m were measured throughout the upper water column and our experimental results indicate that algal growth was limited by iron deficiency these observations suggest that availability of dissolved iron is a primary factor limiting phytoplankton growth over much of the subantarctic southern ocean in the late summer and autumn

dissolved fe and al in the upper 1000 m of the eastern indian ocean a high resolution transect along 95 e from the antarctic margin to the bay of bengal a high resolution section of dissolved iron dfe and aluminum dal was obtained along 95 e in the upper 1000 m of the eastern indian ocean from the antarctic margin 66 s to the bay of bengal 18 n during the u s climate variability and predictability clivar co2 repeat hydrography i08s and i09n sections february april 2007 in the southern ocean low concentrations of dal

loess in italy genesis characteristics and occurrence abstract there is currently a renewed interest in loess genesis and occurrence in italy well known loess profiles in northern italy have been re examined and previously unknown loess deposits in central and southern italy have been reported this work combines a meta analysis of published data with new data presented here for the first time to provide the state of the art on the spatial distribution characteristics genesis and deposition ages of loess in italy a database of 98 soil horizons from 91 soil profiles was created and made available it stores information on soils formed from loess or containing layers that show admixture of loess soil data include the source of information the topographic geomorphological and geological setting kind of parent material and land use main soil horizon properties as described in the field soil classification particle size distribution and chemical data loess is reported from almost all regions of italy it is generally pedogenized throughout the entire loess body and forms the parent material of deep and complex soil profiles the thickness of the loess deposits varies from a few decimeters to a few meters pedogenesis and local reworking partially change the original loess characteristics in this study we propose a set of parameters that help recognizing loess in soils particle size distribution and sorting geomorphological setting pedostratigraphic position shape of the grains under optical and scanning electron microscope sem and soil micromorphological characteristics the ages of the loess deposits range between 70 ka bp and 18 ka bp there are also a number of samples that have been dated to the holocene the meta analysis suggests that climate is not the only driver of loess deposition in italy geomorphological instability and human disturbance as well as the influence of saharan dust most likely played major roles too this study demonstrates that loess is much more widespread in italy than previously estimated yet further research on the spatial and temporal distribution of loess deposition across the mediterranean region is needed to better understand its genesis sources and trajectories periods of enhanced loess formation and the role of loess deposits in ecosystem functioning and resilience

the record of continental dust from australia in tasman sea sediments abstract the flux of aeolian dust from australia to sediments of the tasman sea has increased during glacial stages of the last four glacial cycles low fluxes of dust from australia before 350 ka were followed by an increase in stage 10 and high fluxes in peak glacial periods thereafter the initiation of higher dust fluxes in stage 10 is consisten with previous estimates of the age of onset of aridity in the source area dust flux to the tasman sea is thought to record the intensity of deflation from the source area in interior southeastern australia which was marked by arid conditions and possibly greater windiness during the last glacial a transect of five cores from the central tasman sea revealed consistently low dust fluxes north of 33 s increasing southward to approximately 40 s glacial to interglacial movement of the northern boundary of the dust plume governed by the position of the subtropical ridge was less than 6 latitude probably closer to 3 350 km the position of the dust plume determined in this study and its response to climate change are significantly different from a previous reconstruction based on the measurement of quartz content of the non biogenic sediment fraction

aerosol iron and aluminum solubility in the northwest pacific ocean results from the 2002 ioc cruise dust aerosol samples were collected across the western north pacific ocean during may june 2002 samples were analyzed for soluble aerosol fe ii fe ii fe iii and al as well as major cations and anions the aerosol samples were leached using a 10 second exposure to either filtered surface seawater or ultrapure deionized water yielding a measure of the instantaneous soluble fraction a variety of analytical methods were employed including 57fe isotope dilution high resolution icp ms energy dispersive x ray fluorescence graphite furnace aas ion chromatography and the felume chemiluminescent technique fe was found to be more soluble in ultrapure deionized water leaches especially during periods of higher dust concentrations fe solubility averaged 9 8 in ultrapure water leaches and 6 5 in seawater leaches significant correlations were found between both soluble aerosol fet and soluble fe ii concentrations and aerosol acidity however the percentages of soluble aerosol fet and fe ii did not correlate with aerosol acidity we also did not observe significant correlations between total and soluble aerosol fe concentrations and the concentrations of either particulate fe or dissolved fe in surface waters

scanning electron microscope analysis of sediments from tabun cave mount carmel israel received 6 february 1984 revised ms accepted 30 august 1984 scanning electron microscope analysis of sediments from tabun cave has revealed a detailed palaeoenvironmental history for the area basal units garrod s f and g layers derive from wind blown materials intermediate units e are wind blown derivatives but with marine modification and the upper units d b c exhibit only aeolian modification to grain surfaces as had been previously postulated the analyses also provide supporting evidence for chemical alteration phases within the sediments keywords scanning electron microscope aeolian sub aqueous sediment cave environmental reconstruction introduction prehistoric cave sediments have been studied for at least the past 40 years lais 1941 most workers especially those active in europe bonifay 1956 miskovsky 1973 laville 1975 have tended to use the same analytical tool kit generally consisting of grain size and morphometric studies and a few chemical mineralogical analyses such as ph calcimetry organic matter clay and heavy mineral studies within the last decade however other techniques have begun to make their impact both as independent methods in their own right or as complements to more classical procedures principal among these are micromorphology goldberg 1979a b and scanning electron microscopy em of quartz grains tankard 1974 bull 1981a b this latter technique is now becoming more widely accepted as recent statistical analysis culver et al 1983 has shown that the various suites of quartz grain surface textures can be used to indicate past environments of modification as was initially intimated nearly 20 years ago see krinsley doornkamp 1973 for review in this study we present an application of the technique to an archaeologically related problem cf tankard 1974 and attempt to show how these results and interpretations compare with those based on more classical sedimentological techniques goldberg 1973 1980 farrand 1979

sem analysis of quartz sand grain surface textures indicates alluvial colluvial origin of the quaternary glacial boulder clays at huangshan yellow mountain east central china abstract geomorphic features and pleistocene deposits on huangshan have been attributed to glaciation recent reassessment questions this interpretation as part of the reassessment quartz sand grains from deposits identified as glacial boulder clays till composed of boulders in a clay or silt matrix were analyzed by scanning electron microscope for evidence of their sedimentary history surface textures found on the boulder clay grains were compared with those on grains with known sedimentary histories including glacial grus colluvial and alluvial grains the analysis shows that the grains lack typical glacial textures the surface textures present indicate a complex history nonuniformly weathered grain surfaces point to chemical weathering of the source rock this is supported by the deep weathering of the nonquartz clasts in the sand sized fraction as well as in boulders at the outcrops the close correspondence in surface texture frequencies with those of the alluvial grains indicates an alluvial component to the grains history the similarity with the colluvial grains and the outcrops structures suggest an alluvial colluvial origin for the deposits the history indicated by the surface textures agrees with the recent reassessment of the geomorphic features and points to warm climatic conditions in east central china for at least part of the pleistocene

iron fractionation in pack and fast ice in east antarctica temporal decoupling between the release of dissolved and particulate iron during spring melt abstract iron is a fundamental nutrient limiting phytoplankton growth in vast regions of the southern ocean sea ice which covers 80 of the southern ocean south of 60 s during maximum extent can concentrate iron up to two orders of magnitude higher than in the underlying sea water the fractionation of iron between the particulate and dissolved fractions depends on the location and type of sea ice formation and can impact on the bioavailability of this important trace element this study is the first to document iron fractionation and concentration in both pack and fast ice during a single research study sampling was from within the 110 130 e sector of antarctica we observed markedly higher concentrations of particulate iron at our fast ice site 0 96 214 nm relative to several pack ice sites 0 87 77 7 nm a high particulate to dissolved iron ratio was observed at the fast ice site 285 1 relative to the highest observed in pack ice 23 1 this suggests a decoupling between the sources and or sinks of the dissolved and particulate fractions preferential release of dissolved iron and not particulate iron into brines at all sites sampled with the sack hole method and therefore indicative of brine drainage indicates the diffuse nature of the dissolved fraction furthermore this indicates that there may be a temporal decoupling between the release of the dissolved and the particulate fractions into the water column as sea ice becomes more permeable during the seasonal melt implications for phytoplankton production in antarctic sea ice are discussed

slope process change and colluvium deposition in swaziland an sem analysis electron microscope analysis of sixty samples taken from six colluvium sites in swaziland has shown that the quartz grains exhibit marked edge abrasion in the uppermost beds of exposures this edge abrasion is lacking in the lower beds in all sections examined and indicates slope process change during colluvium deposition a model of slope evolution is provided in which slope erosion progressively brings about more channelling and causes greater surface roughness because of the exhumation of more core stones and differentially weathered rock this roughness causes increased edge abrasion

are mediterranean mountains entisols weakly developed the case of orthents from sierra nevada southern spain two orthents from sierra nevada national park spain classified as loamy skeletal mesic typic xerorthent and loamyskeletal frigid lithic cryorthent were studied they were situated at 1460 and 2000 m derived from micaschists and quartzites under mediterranean mountain climate conditions with mesic and cryic temperature regimes and xeric moisture regime these orthents are weakly developed as shown by their reduced thickness their lack of diagnostics subsurface horizons sandy loam textures skeletal and lithochromic colors quartz is present in significant amounts particularly in the fine light sand fraction analysis of the quartz grains of the fine light sand by scanning electron microscope sem and backscattered electron images bse revealed the presence of significant physical and chemical alteration features such as fractures corrosion gulfs fields of etch pits and dissolution of intergranular surfaces this process is confirmed by electron microprobe analysis empa since the edges of the quartz grains have a higher proportion of cations other than si compared to their centre further evidence indicates the authigenic nature of the process starting from quartz etching an assessment of soil weathering has been made w index from marcelino et al 1999 the alteration of the quartz together with the development of a ultramicrofabric with several fabric units investigated with sem and other characteristics mineralogical chemical etc are considered indicative of some pedogenic evolution these facts are especially interesting in the case of weakly developed mediterranean mountain soils from sierra nevada where processes of chemical weathering have traditionally not been considered very active d 2003 elsevier b v all rights reserved

tectonically controlled piecemeal caldera collapse a case study of glencoe volcano scotland caldera collapse at glencoe scotland was incremental and involved complex movements of numerous fault blocks before formation of the ring fault for which the volcano is renowned intracaldera depocenters had the form of grabens or half grabens locally with downsag and bounding monoclinal flexures and these changed form and location for each of the five major ignimbrite eruptions that represent the early volcanic history this piecemeal caldera collapse is in contrast to previous interpretations in which all subsidence was thought to have involved a coherent crustal block moving on the ring fault collapse and magmatic plumbing were profoundly influenced by preexisting tectonic faults trending northwest and northeast a dominant northwest trending graben controlled the general location and form of major caldera depocenters and repeatedly channeled a major river through glencoe the main graben was transected orthogonally by two cross grabens each of the first three caldera eruption cycles involved initial phreatomagmatic explosivity which built tuff cones followed by magmatic fountaining that produced lava like silicic ignimbrites the three lava like ignimbrites total more than 300 m thick two later eruptions produced eutaxitic silicic ignimbrites together more than 300 m thick and contemporaneous progressive downsag was associated with the formation of extensional fractures crevasses hundreds of meters deep sills up to 100 m thick of mingled andesite and rhyolite between the intracaldera ignimbrites were accommodated by increments of subsidence unconformities and sedimentary layers within the stratigraphic succession record fluvial erosion and abrupt switches to alluvial and or lacustrine deposition between each ignimbrite eruption the changes in drainage and sedimentation and the development of coarse debris avalanche breccias reflect tectonic faulting during the periods between major eruptions the duration of the period including the five caldera forming eruptions was probably 0 5 m y and the magnitude of the tectonic faulting that occurred prior to and during the caldera developments 0 5 km m y normal displacement is similar to that of the most actively subsiding sedimentary basins glencoe shows that the piecemeal nature of calderas may be plainly evident only in deeply dissected systems which with knowledge that caldera volcanoes commonly overlie faults suggests that piecemeal calderas may be more common than previously recognized the research also shows that the emplacement of granites s l was episodic rather than synchronous throughout the magmatic province and it suggests that numerous plutons in the province e g in donegal ireland may have formed at sites of central volcanoes that are no longer preserved

fault controls on the geometry and location of the okataina caldera taupo volcanic zone new zealand abstract okataina caldera is located within the taupo rift and formed due to collapse following eruptions at 325 and 61 ka gravity seismic reflection topographic and geological data indicate that active rift faults pass into the caldera and have influenced its location and geometry the caldera has a minimum gravity anomaly of 50 mgal is elongate north south with an inferred minimum depth to caldera floor of 3 0 5 km at the rift axis and occupies a 10 km hard linked left step in the rift the principal rift faults 55 75 dip define the location and geometry of the northwest and southeast caldera margins and locally accommodate piecemeal collapse segments of the east and west margins of the caldera margin are near vertical 70 90 dip trend north south and are inferred to be faults formed by the reactivation of a pervasive mesozoic basement fabric i e faults and or lithological contacts the fault sets which define the caldera geometry predate it while the step in the rift across the okataina volcanic centre ovc is at least as old as the caldera within the ovc displacement on rift faults induced by gravitational caldera collapse at 61 ka exceeds tectonic displacement since this time by at least a factor of two collapse along pre existing rift faults and in particular mesozoic basement fabric are important for caldera formation elsewhere in the taupo volcanic zone

dust deposition in the eastern indian ocean the ocean perspective from antarctica to the bay of bengal atmospheric deposition is an important but still poorly constrained source of trace micronutrients to the open ocean because of the dearth of in situ measurements of total deposition i e wet dry deposition in remote regions in this work we discuss the upper ocean distribution of dissolved fe and al in the eastern indian ocean along a 95 e meridional transect spanning the antarctic margin to the bay of bengal we use the mixed layer concentration of dissolved al in conjunction with empirical data in a simple steady state model to produce 75 estimates of total dust deposition that we compare with historical observations and atmospheric model estimates except in the northern bay of bengal where the ganges brahmaputra river plume contributes to the inventory of dissolved al the surface distribution of dissolved al along 95 e is remarkably consistent with the large scale gradients in mineral dust deposition and multiple source regions impacting the eastern indian ocean the lowest total dust deposition fluxes are calculated for the southern ocean 66 60 mg m 2 yr 1 and the highest for the northern end of the south indian subtropical gyre up to 940 mg m 2 yr 1 at 18 s and in the southern bay of bengal 2500 570 mg m 2 yr 1 our total deposition fluxes which have an uncertainty on the order of a factor of 3 5 are comparable with the composite atmospheric model data of mahowald et al 2005 except in the south indian subtropical gyre where models may underestimate total deposition using available measurements of the solubility of fe in aerosols we confirm that dust deposition is a minor source of dissolved fe to the southern ocean and show that aeolian deposition of dissolved fe in the southern bay of bengal may be comparable to that observed underneath the saharan dust plume in the atlantic ocean

distinguishing depositional setting for sandy deposits in coastal landscapes using grain shape abstract several methods exist that use sediment properties to characterize depositional setting and related mechanisms of transport including analysis of grain size distributions sediment petrology micromorphology and grain structure techniques that rely on electron or optical microscopy produce results with varying degrees of success and applicability here a new method is presented and used to differentiate between littoral and eolian sands that were extracted from recently formed landforms as well as landforms that are from mid to late holocene in age the method utilizes a standard optical microscope with a mounted digital camera paired with freely available software imagej to characterize grain shape parameters the method was tested on nearly 6000 sand grains from samples with varied transport histories and it was found that grain solidity was the most distinguishable characteristic between eolian and littoral samples differentiating them 86 of the time for calibration samples the method was used to correctly identify the mechanism of transport for 76 of the samples patterns in the results indicated that this method could be extended to link potential sediment sources to various depositional basins and future work includes testing the method in areas with a different mineralogy and or landscape history

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

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

subsurface structure of interannual temperature anomalies in the australian sector of the southern ocean 1 a 7 year time series of austral summer expendable bathythermograph xbt sections between tasmania and antarctica is used to describe the subsurface structure of southern ocean interannual temperature anomalies comparison of the discontinuous xbt record with a continuous weekly average satellite based sst data set confirms that the xbt sampling is adequate to resolve interannual variability significant correlations are found between changes in surface and subsurface temperature along much of the section in the subantarctic zone surface and subsurface changes are coherent because deep convection in winter homogenizes the upper 600 m and the summer mixed layer temperature reflects the preconditioning of the previous winter at other latitudes the regions of high correlation generally extend well beyond the depth of direct atmospheric influence i e the depth of the winter mixed layer negative positive temperature anomalies at interannual timescales are coherent with poleward equatorward displacements of fronts the simplest explanation for the correspondence between deep vertically coherent temperature anomalies and the location of acc fronts is that the observed features reflect meridional shifts of temperature gradients associated with the fronts the link between temperature anomalies and front displacements suggests southern ocean sea surface temperature sst anomalies primarily reflect a dynamical response of the ocean to wind or other forcing rather than surface trapped features produced by anomalous air sea heat flux the xbt record contains both interannual and longer unresolved period signals which cannot be isolated in the short discontinuous xbt time series spectral analysis of the 17 year sst data set reveals roughly equal variability in 2 7 year and 7 year bands

on the relationship between fronts of the antarctic circumpolar current and surface chlorophyll concentrations in the southern ocean 1 we reexamine the relationship between circulation bathymetry and surface chlorophyll in the southern ocean using new high resolution maps of the frontal structure of the antarctic circumpolar current acc derived from satellite altimetry the maps reveal that the acc consists of multiple filaments or jets by averaging surface chlorophyll measurements along streamlines we show that the fronts define the limits of zones with similar concentrations and seasonality of surface chlorophyll the overall pattern of surface chlorophyll is consistent with strongest upwelling of nutrient rich deep water south of the polar front pf however the distribution of chlorophyll in the southern ocean is concentrated in a number of persistent blooms observed downstream of islands and bathymetric features in contrast to previous studies we find little evidence that the fronts of the acc are associated with enhanced productivity at least where the fronts are distant from topography rather we find that most regions of elevated chlorophyll in the open southern ocean can be explained by upwelling of nutrients both macronutrients and micronutrients where the acc interacts with topography followed by downstream advection the upwelling is shown to be the consequence of the bottom pressure torque established by the large scale flow rather than being due to small scale instabilities of the jets the interaction of the flow with the topography therefore establishes both the large scale dynamical balance of the acc and determines the productivity of the open southern ocean

the continental margin is a key source of iron to the hnlc north pacific ocean here we show that labile particulate iron and manganese concentrations in the upper 500m of the western subarctic pacific an iron limited high nutrient low chlorophyll hnlc region have prominent subsurface maxima between 100 200 m reaching 3 nm and 600 pm respectively the subsurface concentration maxima in particulate fe are characterized by a more reduced oxidation state suggesting a source from primary volcagenic minerals such as from the kuril kamchatka margin the systematics of these profiles suggest a consistently strong lateral advection of labile mn and fe from redox mobilized labile sources at the continental shelf supplemented by a more variable source of fe from the upper continental slope this subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing and is likely a key source of bioavailable fe to the hnlc north pacific

a simple method to classify diamicts by scanning electron microscope from surface microtextures interpretation of quartz sand grain surface microtextures with scanning electron microscopy has been riddled with inconsistencies invalid assumptions and much subjectivity therefore a novel classification for analysing grain surface microtextures is presented based on the origin of complete grain surfaces this novel method has solved most of the earlier problems of interpretation of surface microtextures and it is easy to use and to quickly find evident genetic interpretations of diamicts the data are plotted graphically in 2 history diagrams or 3 history diagrams for quick visual inspection and statistical evaluation source rocks and quaternary glacial deposits from scandinavia and southern ontario representing different ice substrate dynamics are analysed to define surface microtextures from typical glacigenic grains bedrock and fluvially transported grains typical glacially crushed grains display large scale fractures and abrasion shield bedrock grains display large or small scale fractures and solution precipitation microtextures fluvially transported grains exhibit abrasion and solution precipitation microtextures

multiple sources of soluble atmospheric iron to antarctic waters the ross sea antarctica is a highly productive region of the southern ocean significant new sources of iron fe are required to sustain phytoplankton blooms in the austral summer atmospheric deposition is one potential source the fractional solubility of fe is an important variable determining fe availability for biological uptake to constrain aerosol fe inputs to the ross sea region fractional solubility of fe was analyzed in a snow pit from roosevelt island eastern ross sea in addition aluminum dust and refractory black carbon rbc concentrations were analyzed to determine the contribution of mineral dust and combustion sources to the supply of aerosol fe we estimate exceptionally high dissolved fe dfe flux of 1 2 10 6 g m 2 y 1 and total dissolvable fe flux of 140 10 6 g m 2 y 1 for 2011 2012 deposition of dust fe al and rbc occurs primarily during spring summer the observed background fractional fe solubility of 0 7 is consistent with a mineral dust source radiogenic isotopic ratios and particle size distribution of dust indicates that the site is influenced by local and remote sources in 2011 2012 summer relatively high dfe concentrations paralleled both mineral dust and rbc deposition around half of the annual aerosol fe deposition occurred in the austral summer phytoplankton growth season however the fractional fe solubility was low our results suggest that the seasonality of dfe deposition can vary and should be considered on longer glacial interglacial timescales

observational evidence for a southern hemisphere oceanic supergyre 1 a high resolution hydrographic atlas resolves the narrow boundary flow of the western pacific gyre and its pathway around tasmania southern australia and into the indian ocean basin this confirms recent model descriptions of a southern hemisphere supergyre a nested system of subtropical gyres the observations show that the gyre flow is squeezed into a narrow band between tasmania and the antarctic circumpolar current the residue of east australian current transport turns westward around tasmania and leaks into the indian ocean while there is also a limited form of gyre connection between the indian and atlantic systems south of africa with a mean outflow of agulhas current water into the atlantic basin these gyre circulations remain far more discrete the gyre coupling and the east australian current in particular provide the mechanism by which sub antarctic mode water and antarctic intermediate water are distributed between the ocean basins

episodic enhancement of phytoplankton stocks in new zealand subantarctic waters contribution of atmospheric and oceanic iron supply 1 around 30 of oceanic waters are high nitrate low chlorophyll hnlc where low iron levels limit algal growth hnlc waters have mainly been studied using shipboard and lab experiments since 1997 remote sensing of phytoplankton via seawifs ocean color has permitted monitoring of the constancy of this hnlc condition i e spatial homogeneity and low temporal variability of chlorophyll over annual cycles these trends can be exploited as episodic iron inputs should be conspicuous by subsequent expression as iron elevated algal stocks subantarctic sa waters near new zealand are hnlc and the proximity of the arid australian landmass and the iron rich subtropical front provide natural laboratories to detect episodic atmospheric and oceanic iron supply respectively two approaches were used oceanic supply was inferred from episodic increases in chlorophyll concentrations in sa waters detected using ocean color archives additional archives were used to confirm the oceanic provenance of iron supply and identify supply mechanism s atmospheric supply was assessed using data on source areas and loads for dust storms monitored in central australia dust transport and its fate was assessed using air mass forward trajectories and seawifs ocean color and aerosol optical depth maps during 1997 2001 episodic elevated chlorophyll events occurred in sa waters southeast of new zealand there was no evidence of these events being mediated by atmospheric iron supply however neither wind driven lateral advection or vertical mixing alone could account for these episodes dust storms over this period sent plumes either into high iron subtropical st waters or into sa waters in early spring when cells are probably light rather than iron limited

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

chemical textures on quartz grains an experimental approach using salts two groups of fresh crushed brazilian quartz grains 0 4 0 6 mm were placed in 10 ml of various saturated salt solutions sodium sulphate sodium chloride magnesium sulphate sodium carbonate and sodium carbonate and soil one group was placed in an environmental cabinet programmed to simulate summer diurnal temperature and relative humidity values recorded in wheeler valley a dry valley in southern victoria land antarctica the other group was allowed to remain at normal laboratory conditions quartz grains from both groups were removed at pre selected intervals for examination using the scanning electron microscope after 50 hours chemical surface textures were formed on the quartz grains in all but the sodium sulphate solution at the 140 hour interval all the salt solutions used were producing chemical surface textures on the quartz grains this paper demonstrates that chemical surface textures can be produced on quartz grain surfaces by saturated salt solutions in a short period of time and may prove to be representative of chemical surface textures produced in a saturated saline environment

loess and soils in the eastern ebro basin abstract wind blown sandy and silty deposits were formed during the late quaternary in the ne iberian peninsula they are the most significant in the west mediterranean region together with those described in the tagus river basin iberian south subplateau forming small scattered patches across parts of the se ebro depression and sw catalan mediterranean range two major depositional environments are distinguished the first largest outcrop covers the lower ebro reaches on the se border of the ebro depression the prelitoral coastal range and the mora d ebre basin a second outcrop to the north consists of a few patches scattered over a wide amphitheatre surrounding the western tributaries of the segre river from the wind exposed segria platforms to the almenara range in its northernmost part they consist of highly sorted fine sands and silts 1 12 m thick though most typically 3 4 m thick and coarser than typical loess they are highly uniform lack any sedimentary structures and are pale ochre the deposits are calcareous 30 45 caco3 basic to alkaline and with some soluble salts five selected sequences of primary loess namely mas de l alerany tivissa guiamets batea and almenara were studied to ascertain deposit characteristics and soil development all sections show a consistent vertical granulometric variability that may be attributed to wind intensity changes and hinders the recognition of spatial particle size distribution pedogenesis is mostly related to calcium carbonate redistribution which accumulates as nodules large rhizocretions or biogenic calcite secondary gypsum batea and almenara sequences is probably related to primary gypsum blown from the source areas that was redistributed by leaching and precipitation at the bottom of the profiles in a few places mas de l alerany outcrop a fersialitic rubefacted recalcified soil indicates the presence of an older generation of loess while the dominant wnw winds and particle coarseness suggest that the loess originates from nearby alluvial fans and fluvial plains the presence of gypsum and mg anomalies may be evidence of more distant sources of the central ebro depression and ondara corb alluvial fans optical stimulated luminiscence osl ages for the more recent deposits guiamets batea almenara are between 18 and 34 ka while the old mas de l alerany sequence is more than 115 ka these ages indicate loess deposition during the last cold phases of the quaternary and with pedogenesis occuring during warm interglacial periods

oceanic iron supply mechanisms which support the spring diatom bloom in the oyashio region western subarctic pacific 1 multiyear 2003 2008 time series observations along the a line provided information on the temporal variability of the dissolved iron diss fe concentration in the oyashio region of the western subarctic pacific and the data indicated that there was an annual cycle in the concentration of surface diss fe occurring every year diss fe was supplied into the surface water in this region every winter and supports the spring phytoplankton bloom after development of the thermocline the diss fe concentration was drawn down during the phytoplankton bloom period and was depleted in summer in some water masses then diss fe increased from autumn to winter with the increasing depth of the surface mixed layer the high diss fe concentrations in the surface layer in winter were controlled by mesoscale oceanic intrinsic processes such as vertical winter mixing and horizontal fe rich intermediate water transport difference in magnitude of the winter mixing processes among different water masses caused the heterogeneous distribution of diss fe concentration in the surface layer moreover the vertical section profiles along a cross oyashio transect showed the occurrence of fe rich intermediate water and upward transport of materials from the intermediate water to the surface layer via tidal and winter mixing processes are important mechanisms to explain the high winter surface diss fe concentrations additionally the substantially higher diss fe no3 ratio in the winter surface layer in this studied area other than the high nutrient low chlorophyll region indicates that the winter surface water in the oyashio and the oyashio kuroshio transition zone has a high potential to stimulate phytoplankton growth

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

twilight zone organic carbon remineralization in the polar front zone and subantarctic zone south of tasmania abstract we report on the distribution of excess non lithogenic particulate barium ba xs a proxy for twilight zone remineralization of organic matter in the australian sector of the southern ocean during the mid austral summer 2007 this study was part of a broader investigation focusing on macro and micronutrient availability controlling ecosystem functioning in this area mesopelagic particulate excess ba ba xs in the twilight zone focus was on the 100 600 m depth layer proved to be significantly controlled by the vertical distribution of bacterial activity with higher ba xs contents in situations where significant bacterial activity extended deeper in the water column however despite this covariation the magnitude of the carbon fluxes as estimated from ba xs and bacterial activity did not match well with carbon demand based on bacterial activity largely exceeding organic carbon remineralization estimated from ba xs possible reasons for this discrepancy are discussed it appeared that the magnitude of the mesopelagic carbon remineralization flux obtained from ba xs was realistic when weighted against primary new and export productions our findings corroborate earlier results indicating that mesopelagic carbon remineralization in the 100 600 m depth layer increases from the subantarctic zone saz toward the polar front and from spring to late summer we observed furthermore that the iron replete subantarctic zone east of the tasman plateau had a higher mesopelagic remineralization efficiency on average 91 20 of the carbon exported from the upper 100 m was remineralized before reaching 600 m compared to the fe limited saz area west of the plateau and the polar front zone where mesopelagic remineralization efficiencies ranged between 21 5 and 64 24 respectively saz east and saz west sites thus differed in their efficiency of carbon sequestration into the deep 600 m water column with saz west exceeding the sequestration capacity of saz east

sinking fluxes of minor and trace elements in the north pacific ocean measured during the vertigo program as part of the vertical transport in the global ocean vertigo program we collected and analyzed sinking particles using sediment traps at three depths in the oceanic mesopelagic zone and at two biogeochemically contrasting sites n central pacific at aloha n pacific western subarctic gyre at k2 in this paper we present the results of minor and trace element determinations made on these samples minor and trace elements in the sinking material showed 2 trends in flux with depth increasing and constant the sinking particulate phase of some elements al fe mn was dominated by material of lithogenic origin and exhibited flux that was constant with depth and consistent with eolian dust inputs aloha or increasing in flux with depth as a result of lateral inputs from a shelf k2 this shelf derived material also appears to have been confined to very small particles whose inherent sinking rates are slow and residence time within the mesopelagic twilight zone would be consequently long furthermore the flux of this material did not change with substantial changes in the rain of biogenic material from the surface k2 suggesting mechanistic decoupling from the flux of organic carbon and macronutrients micronutrient fe co zn and cu fluxes examined in a 1 d mass balance suggest widely differing sources and sinks in the water column as well as impacts from biological uptake and regeneration for example total fe fluxes into and out of the euphotic zone appeared to be dominated by lithogenic material and far exceed biological requirements the export flux of fe however appeared to be balanced by the eolian input of soluble fe for zn and cu the situation is reversed with atmospheric inputs insufficient to support fluxes and the cycling therefore dominated by the draw down of an internal pool for co the situation lies in between with important but ultimately insufficient atmospheric inputs

australian dust storms in 2002 2003 and their impact on southern ocean biogeochemistry during late 2002 and early 2003 southern australia was in the grip of drought and experienced one of its most active dust storm seasons in the last 40 years with large dust plumes frequently advected over the adjacent southern ocean we use meteorological records of dust activity satellite ocean colour and aerosol optical depth data and dust transport modeling to investigate the transport and deposition of mineral dust from australia over adjacent ocean regions and to correlate it with biological response in phytoplankton standing stock as measured by chlorophyll a concentration in five degree latitude bands from 40 60 s seasonal maxima in mean surface chlorophyll a of 0 5 mg m 3 were not achieved until late jan 2003 or during february in the more southerly bands which when compared with a 9 year satellite mean climatology suggests the phenology of the bloom in 2002 03 was atypical contemporaneous field data on co2 fugacity collected on transects between tasmania and antarctica show that significant atmospheric co2 drawdown occurred as far south as 60 s during february 2003 our results provide strong evidence for a large scale natural dust fertilization event in the australian sector of the southern ocean and highlight the importance of dust derived nutrients in the marine carbon cycle of the southern ocean

multidisciplinary characterization of the middle holocene eolian deposits of the elsa river basin central italy abstract in temperate regions eolian deposits of different natures are often pedogenically altered and mixed with underlying sediments the research reported in this paper identifies for the first time the presence of eolian deposits in soils of central tuscany and investigates the characteristics and origin five relict polycyclic paleosol profiles were studied p1 was situated in a natural dust trap a doline on top of an isolated limestone hill p2 and p3 were both situated on a limestone plateau and p4 and p5 on a mid and foot slope on schist the profiles were sampled for routine analyses iron forms heavy minerals major and trace elements and pollen spores and non pollen palynomorphs undisturbed samples were taken for micromorphological and sem analyses nine soil horizons were sampled for osl dating eolian deposits were dominant or abundant in the first layers of p1 p2 and p3 osl age determinations of soil horizons deriving from eolian parent material were middle holocene chemical and heavy mineral analyses indicated different possible sources including bare slopes alluvial fans and wide channels coming from the nearby streams that drain the middle tuscany ridge and the mounts of chianti marginal contribution of volcanic ashes was only found in p1 the research demonstrated that wind soil erosion accompanied water erosion and colluvial deposition during the middle holocene in the elsa river basin pollen spectra in particular indicated that soil degradation occurred in an environment showing signs of incipient desertification resulting from an increase of aridity in a land already strongly influenced by humans although central italy is currently considered to be only marginally affected by wind soil erosion a climate change which would imply increased arid conditions could trigger a new cycle of slope denudation wind erosion and loess deposition

dissolved iron and iron ii distributions beneath the pack ice in the east antarctic 120 e during the winter spring transition distributions of dissolved iron dfe and its reduced form fe ii to a depth of 1000 m were investigated under the seasonal pack ice off east antarctica during the sea ice physics and ecosystem experiment sipex 2 sea ice voyage in september october 2012 concentrations of dfe were elevated up to five fold relative to southern ocean background concentrations and were spatially variable the mean dfe concentration was 0 44 0 4 nm with a range from 0 09 to 3 05 nm profiles of dfe were more variable within and among stations than were macronutrients suggesting that coupling between these biologically essential elements was weak at the time of the study brine rejection and drainage from sea ice are estimated to be the dominant contributors to elevated dfe concentrations in the mixed layer but mass budget considerations indicate that estimated dfe fluxes from brine input alone are insufficient to account for all observed dfe melting icebergs and shelf sediments are suspected to provide the additional dfe fe ii was mostly below the detection limit but elevated at depth near the continental shelf implying that benthic processes are a source of reduced fe in bottom waters the data indicate that dfe builds up under the seasonal sea ice cover during winter and that reduction of fe may be hampered in early spring by several factors such as lack of electron donors low biological productivity and inadequate light below the sea ice the accumulated dfe pool in the mixed layer is expected to contribute to the formation of the spring bloom as the ice retreats

silicic acid enrichment of subantarctic surface water from continental inputs along the patagonian archipelago interior sea 41 56 s abstract we estimated si the surplus or deficit of orthosilicic acid dsi relative to nitrate available for diatom growth in the chilean patagonian archipelago interior sea pais si and salinity were negatively correlated in the pais because of the mixing of high nitrate low dsi subantarctic surface water and high dsi low nitrate continental freshwater runoff both the slope and the intercept of this relationship decreased from northern to southern patagonia which was likely a consequence of reduced dsi inputs from several overlapping hydrological biological and geological drivers along this gradient in general lower freshwater dsi concentrations were expected below 46 s and a lower total dsi load was expected from reduced runoff below 51 s the north south decreasing dsi concentration trend may be linked to dilutions from a higher proportion of runoff in latitudes with higher precipitation rates 45 53 s the transition to more resistant granitic rocks and glacial melt water from the northern and southern patagonia ice fields 46 51 s and a reduced density of volcanoes active during the holocene 48 56 s the intensification of a southward dsi deficit may be a forcing factor involved in the reported southward reductions in plankton biomass and a more frequent occurrence of non diatom blooms in southern pais

microtextural analysis of quartz grains of tsunami and non tsunami deposits a case study from tirua chile abstract in order to estimate the tsunami hazard it is essential to reliably identify and differentiate tsunami deposits from other high energy events like storms recently the microtextural analysis of quartz grain surfaces was introduced as a method to differentiate between tsunami and other deposits using tsunami deposits sampled from a bank profile of the tirua river central chile an area that was significantly affected by the 2010 and 1960 chile tsunamis we tested the microtextural analysis method for its capability to identify tsunami deposits a total of 815 quartz grain surfaces of two tsunami layers two non tsunami marsh sediment samples and three reference samples from nearby beach dune and river were analyzed using scanning electron microscopy sem we grouped the detected microtexture features into five microtextural families angularity fresh surfaces percussion marks adhering particles and dissolution features both the tsunami deposits and reference samples reveal high numbers of fresh surfaces and percussion marks thus there are no statistically significant differences between tsunami beach dune and river deposits in characteristics and abundances in all microtextural families our study indicates that the microtextural analysis of quartz grains may not be a suitable method to identify tsunami deposits in tirua chile due to local factors such as high numbers of inherited microtextures and the possible effects of the high amount of heavy minerals

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

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

some observations concerning the morphology and sedimentology of a protalus rampart okstindan norway a protaius rampart up to 4 75 m high and consisting largely of angular clasts up to boulder size is described bulk samples contained up to 35 per cent fines by weight compared with up to 68 per cent fines in adjacent till although the rampart material was clast dominated fines filled much of the void space in contrast with most other protalus ramparts described in the literature

surface microtextures of quartz grains from vistulian loesses from selected profiles of poland and some other countries abstract the vistula glaciation loesses have been investigated in comparison to some profiles from central europe on the basis of quartz grains examination in sem and referring to lithological features a reconstruction of the sedimentary environment and transport type is made analysis of frequency of quartz grains with definite features shows important variations in terms of type and quantity amongst the features the most varied microtextures are observed on 1 0 0 5 mm grains and smaller 0 5 0 25 mm completely different microtextures have been recognized on 0 1 0 5 mm grains on which encrusted smooth surface formed due to precipitation of silica at deflation sites can be observed the 0 1 0 05 mm quartz grains from the polish loesses indicate one source area with an arid climate the grains were probably transported by high winds from a distant area located in the east in contrast the coarser sand sized quartz grains indicate a variable provenance they usually originated from an adjacent area and underwent limited transport a distinct difference in microtextures of quartz grains occurs at the boundary of the younger middle loess lms and younger upper loess lmg lmg is best defined by more aeolian and fewer corrosional post sedimentary features