WorldWideScience

Sample records for southern ocean controls

  1. Southern Ocean coccolithophore biogeography - controlling factors and implications for global biogeochemical cycles

    Science.gov (United States)

    Nissen, Cara; Vogt, Meike; Münnich, Matthias; Gruber, Nicolas

    2017-04-01

    Southern Ocean phytoplankton biogeography is important for the biogeochemical cycling of carbon, silicate, and the transport of macronutrients to lower latitudes. With the discovery of the "Great Calcite Belt" (GBC), revealing an unexpectedly high prevalence of calcifying phytoplankton in the subtropical frontal region between 40-55°S, the relative importance of Southern Ocean coccolithophores for phytoplankton biomass, net primary productivity and the carbon cycle need to be revisited. Using a regional high-resolution model with an embedded ecosystem module (ROMS-BEC) for the Southern Ocean (24-78°S) that has been extended to include an explicit representation of coccolithophores, we assess the environmental drivers of Southern Ocean coccolithophore biogeography over the course of the growing season. We thereby focus on biotic interactions and the relative importance of top-down (grazing) versus bottom-up factors (light, nutrient, temperature) controlling growth and abundance. In our simulation, coccolithophores are an important member of the Southern Ocean phytoplankton community, contributing 13% to annually integrated net primary productivity south of 30°S. We estimate the integrated annual calcification rate to account for 40% of the satellite derived global estimate. Modeled coccolithophore biomass is highest in February and March in a latitudinal band between 40-55°S, when diatoms become heavily silicate limited. This region is characterized by a number of divergent fronts with a low Si:Fe ratio of waters supplied to the mixed layer, supporting an increased growth of coccolithophores at the expense of diatoms. We find top down controls to be the major control on the relative abundance of diatoms and coccolithophores in the Southern Ocean. We perform iron and silicate fertilization experiments to assess the effects of changed nutrient availability on coccolithophore abundance in the GCB. We find that changes in nutrient stoichiometry significantly alter

  2. Southern Ocean Iron Experiment (SOFex)

    Energy Technology Data Exchange (ETDEWEB)

    Coale, Kenneth H.

    2005-07-28

    The Southern Ocean Iron Experiment (SOFeX) was an experiment decades in the planning. It's implementation was among the most complex ship operations that SIO has been involved in. The SOFeX field expedition was successful in creating and tracking two experimentally enriched areas of the Southern Ocean, one characterized by low silicic acid, one characterized by high silicic acid. Both experimental sites were replete with abundant nitrate. About 100 scientists were involved overall. The major findings of this study were significant in several ways: (1) The productivity of the southern ocean is limited by iron availability. (2) Carbon uptake and flux is therefore controlled by iron availability (3) In spite of low silicic acid, iron promotes non-silicious phytoplankton growth and the uptake of carbon dioxide. (4) The transport of fixed carbon from the surface layers proceeds with a C:N ratio that would indicate differential remineralization of nitrogen at shallow depths. (5) These finding have major implications for modeling of carbon export based on nitrate utilization. (6) The general results of the experiment indicate that, beyond other southern ocean enrichment experiments, iron inputs have a much wider impact of productivity and carbon cycling than previously demonstrated. Scientific presentations: Coale, K., Johnson, K, Buesseler, K., 2002. The SOFeX Group. Eos. Trans. AGU 83(47) OS11A-0199. Coale, K., Johnson, K. Buesseler, K., 2002. SOFeX: Southern Ocean Iron Experiments. Overview and Experimental Design. Eos. Trans. AGU 83 (47) OS22D-01. Buesseler, K.,et al. 2002. Does Iron Fertilization Enhance Carbon Sequestration? Particle flux results from the Southern Ocean Iron Experiment. Eos. Trans. AGU 83 (47), OS22D-09. Johnson, K. et al. 2002. Open Ocean Iron Fertilization Experiments From IronEx-I through SOFeX: What We Know and What We Still Need to Understand. Eos. Trans. AGU 83 (47), OS22D-12. Coale, K. H., 2003. Carbon and Nutrient Cycling During the

  3. Asthenosphere and lithosphere structure controls on early onset oceanic crust production in the southern South Atlantic

    Science.gov (United States)

    Taposeea, Chandra A.; Armitage, John J.; Collier, Jenny S.

    2017-10-01

    The southern South Atlantic has often been considered a classic example of continental break-up in the presence of a starting mantle plume. Evidence for a mantle plume includes the Paranà-Etendeka continental flood basalts, which are associated with the Rio Grande Rise and Walvis Ridge, and the wide-spread presence of seaward dipping reflectors and high-velocity lower-crustal bodies along the conjugate margins. Observations from seaward dipping reflector distributions suggested that lithospheric segmentation played a major role in the pattern of volcanism during break-up in this region, and consequent numerical modelling was used to test this. We tested this hypothesis ourselves by measuring the thickness of the earliest oceanic crust generated. This was done through the use of 37 measurements of initial oceanic crustal thickness from wide-angle and multichannel seismic profiles collected along the conjugate margins. These measurements show that at 450 km south of the Paranà-Etendeka flood basalts the oceanic crust is thicker than the global average at 11.7 km. Farther south the oceanic crust thins, reaching 6.1 km at a distance of 2300 km along-strike. Overall, the along-strike trend of oceanic crustal thickness is linear with a regression coefficient of 0.7 and little indication of segmentation. From numerical models representing extension of the lithosphere, we find that observed melt volumes are matched with the presence of a hot layer. If we assume this region of hot mantle has a thickness of 100 km, its excess temperature relative to the asthenosphere has to decrease from 200 to 50 °C, north to south. This decrease in temperature, also seen in published thermobarometry results, suggests that temperature was the primary control of volcanism during the opening of the southern South Atlantic.

  4. Variability in the mechanisms controlling Southern Ocean phytoplankton bloom phenology in an ocean model and satellite observations

    Science.gov (United States)

    Rohr, Tyler; Long, Matthew C.; Kavanaugh, Maria T.; Lindsay, Keith; Doney, Scott C.

    2017-05-01

    A coupled global numerical simulation (conducted with the Community Earth System Model) is used in conjunction with satellite remote sensing observations to examine the role of top-down (grazing pressure) and bottom-up (light, nutrients) controls on marine phytoplankton bloom dynamics in the Southern Ocean. Phytoplankton seasonal phenology is evaluated in the context of the recently proposed "disturbance-recovery" hypothesis relative to more traditional, exclusively "bottom-up" frameworks. All blooms occur when phytoplankton division rates exceed loss rates to permit sustained net population growth; however, the nature of this decoupling period varies regionally in Community Earth System Model. Regional case studies illustrate how unique pathways allow blooms to emerge despite very poor division rates or very strong grazing rates. In the Subantarctic, southeast Pacific small spring blooms initiate early cooccurring with deep mixing and low division rates, consistent with the disturbance-recovery hypothesis. Similar systematics are present in the Subantarctic, southwest Atlantic during the spring but are eclipsed by a subsequent, larger summer bloom that is coincident with shallow mixing and the annual maximum in division rates, consistent with a bottom-up, light limited framework. In the model simulation, increased iron stress prevents a similar summer bloom in the southeast Pacific. In the simulated Antarctic zone (70°S-65°S) seasonal sea ice acts as a dominant phytoplankton-zooplankton decoupling agent, triggering a delayed but substantial bloom as ice recedes. Satellite ocean color remote sensing and ocean physical reanalysis products do not precisely match model-predicted phenology, but observed patterns do indicate regional variability in mechanism across the Atlantic and Pacific.

  5. Southern Ocean Control of Glacial AMOC Stability and Dansgaard-Oeschger Interstadial Duration

    Science.gov (United States)

    Buizert, C.; Schmittner, A.

    2016-12-01

    Glacial periods exhibit abrupt Dansgaard-Oeschger (DO) climatic oscillations that are thought to be linked to instabilities in the Atlantic meridional overturning circulation (AMOC). Great uncertainty remains regarding the dynamics of the DO cycle, as well as controls on the timing and duration of individual events. Using ice core data we show that the duration of warm (interstadial) periods is strongly correlated with Antarctic climate, and presumably with Southern Ocean (SO) temperature and the position of the Southern Hemisphere (SH) westerlies. We propose a SO control on AMOC stability and interstadial duration via the rate of Antarctic bottom water formation, meridional density/pressure gradients, Agulhas Leakage, and SO adiabatic upwelling. This hypothesis is supported by climate model experiments that demonstrate SO warming leads to a stronger AMOC that is less susceptible to freshwater perturbations. In the AMOC stability diagram, SO warming and strengthening of the SH westerlies both shift the vigorous AMOC branch toward higher freshwater values, thus raising the threshold for AMOC collapse. The proposed mechanism could provide a consistent explanation for several diverse observations, including maximum DO activity during intermediate ice volume/SH temperature, and successively shorter DO durations within each Bond cycle. It may further have implications for the fate of the AMOC under future global warming.

  6. Biological and physical controls in the Southern Ocean on past millennial-scale atmospheric CO2 changes.

    Science.gov (United States)

    Gottschalk, Julia; Skinner, Luke C; Lippold, Jörg; Vogel, Hendrik; Frank, Norbert; Jaccard, Samuel L; Waelbroeck, Claire

    2016-05-17

    Millennial-scale climate changes during the last glacial period and deglaciation were accompanied by rapid changes in atmospheric CO2 that remain unexplained. While the role of the Southern Ocean as a 'control valve' on ocean-atmosphere CO2 exchange has been emphasized, the exact nature of this role, in particular the relative contributions of physical (for example, ocean dynamics and air-sea gas exchange) versus biological processes (for example, export productivity), remains poorly constrained. Here we combine reconstructions of bottom-water [O2], export production and (14)C ventilation ages in the sub-Antarctic Atlantic, and show that atmospheric CO2 pulses during the last glacial- and deglacial periods were consistently accompanied by decreases in the biological export of carbon and increases in deep-ocean ventilation via southern-sourced water masses. These findings demonstrate how the Southern Ocean's 'organic carbon pump' has exerted a tight control on atmospheric CO2, and thus global climate, specifically via a synergy of both physical and biological processes.

  7. Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography

    Directory of Open Access Journals (Sweden)

    F. Fripiat

    2012-07-01

    Full Text Available Southern Ocean biogeochemical processes have an impact on global marine primary production and global elemental cycling, e.g. by likely controlling glacial-interglacial pCO2 variation. In this context, the natural silicon isotopic composition (δ30Si of sedimentary biogenic silica has been used to reconstruct past Si-consumption:supply ratios in the surface waters. We present a new dataset in the Southern Ocean from a IPY-GEOTRACES transect (Bonus-GoodHope which includes for the first time summer δ30Si signatures of suspended biogenic silica (i for the whole water column at three stations and (ii in the mixed layer at seven stations from the subtropical zone up to the Weddell Gyre. In general, the isotopic composition of biogenic opal exported to depth was comparable to the opal leaving the mixed layer and did not seem to be affected by any diagenetic processes during settling, even if an effect of biogenic silica dissolution cannot be ruled out in the northern part of the Weddell Gyre. We develop a mechanistic understanding of the processes involved in the modern Si-isotopic balance, by implementing a mixed layer model. We observe that the accumulated biogenic silica (sensu Rayleigh distillation should satisfactorily describe the δ30Si composition of biogenic silica exported out of the mixed layer, within the limit of the current analytical precision on the δ30Si. The failures of previous models (Rayleigh and steady state become apparent especially at the end of the productive period in the mixed layer, when biogenic silica production and export are low. This results from (1 a higher biogenic silica dissolution:production ratio imposing a lower net fractionation factor and (2 a higher Si-supply:Si-uptake ratio supplying light Si-isotopes into the mixed layer. The latter effect is especially expressed when the summer mixed layer becomes strongly Si-depleted, together with a large

  8. Pteropods in Southern Ocean ecosystems

    Science.gov (United States)

    Hunt, B. P. V.; Pakhomov, E. A.; Hosie, G. W.; Siegel, V.; Ward, P.; Bernard, K.

    2008-09-01

    To date, little research has been carried out on pelagic gastropod molluscs (pteropods) in Southern Ocean ecosystems. However, recent predictions are that, due to acidification resulting from a business as usual approach to CO 2 emissions (IS92a), Southern Ocean surface waters may begin to become uninhabitable for aragonite shelled thecosome pteropods by 2050. To gain insight into the potential impact that this would have on Southern Ocean ecosystems, we have here synthesized available data on pteropod distributions and densities, assessed current knowledge of pteropod ecology, and highlighted knowledge gaps and directions for future research on this zooplankton group. Six species of pteropod are typical of the Southern Ocean south of the Sub-Tropical Convergence, including the four Thecosomes Limacina helicina antarctica, Limacina retroversa australis, Clio pyramidata, and Clio piatkowskii, and two Gymnosomes Clione limacina antarctica and Spongiobranchaea australis. Limacina retroversa australis dominated pteropod densities north of the Polar Front (PF), averaging 60 ind m -3 (max = 800 ind m -3) and 11% of total zooplankton at the Prince Edward Islands. South of the PF L. helicina antarctica predominated, averaging 165 ind m -3 (max = 2681 ind m -3) and up to >35% of total zooplankton at South Georgia, and up to 1397 ind m -3 and 63% of total zooplankton in the Ross Sea. Combined pteropods contributed pig ind -1 d -1), while those of L. helicina antarctica and C. pyramidata are in the upper range for all Southern Ocean zooplankton, in the latter species reaching 27,757 ng pig ind -1 d -1 and >40% of community grazing impact. Further research is required to quantify diet selectivity, the effect of phytoplankton composition on growth and reproductive success, and the role of carnivory in thecosomes. Life histories are a significant knowledge gap for Southern Ocean pteropods, a single study having been completed for L. retroversa australis, making population

  9. Arctic and Southern Ocean Sea Ice Concentrations

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Monthly sea ice concentration for Arctic (1901 to 1995) and Southern oceans (1973 to 1990) were digitized on a standard 1-degree grid (cylindrical projection) to...

  10. Southern Ocean - South African cooperative research programme.

    CSIR Research Space (South Africa)

    SANCOR

    1979-05-01

    Full Text Available South African research in the Southern Ocean has already produced some important and illuminating results. Most of these efforts, however, were of an individual and uncoordinated nature. Due to increasing interest in the ocean- in South Africa...

  11. Composition of settling particles in the Southern Ocean and processes controlling seasonal variations of deep export production

    Science.gov (United States)

    Cardinal, Damien; Ameur, Khedidja; Closset, Ivia; Bray, Stephen; Trull, Thomas W.

    2014-05-01

    In order to understand the processes controlling the biological carbon pump and the efficiency of export production, we need time series in contrasted oceanic regions that fully describe seasonality. Due to strong logistic constraints, especially in the Southern Ocean, such data can only be obtained from above (satellite) or from below (sediment traps). In this study, settling particles of Subantarctic Zone (SAZ), Polar Front Zone (PFZ) and Antarctic Zone (AZ) along the CLIVAR-SR3 transect (140°E, south to Tasmania) have been collected in sediment traps deployed at 1000, 2000 and 3800m (SAZ), 800 and 1500 m (PFZ) and 200 and 3700 m (AZ). In addition to the measurements of Particulate Organic Carbon, Particulate Inorganic Carbon, Biogenic silica we have measured particulate composition of some trace and major elements (Al, Ca, Fe, Ti, Ba, Sr, Mn, U, light Rare Earth Elements) by ICP-MS. When looking at correlations between elemental fluxes we show that there are generally different modes of variations. Surprisingly, those are not necessarily site-specific, i.e. different periods of SAZ and AZ traps can behave in a similar way, while they can be strongly decoupled at other periods. This is the case not only for biogenic elements (e.g. Ba, Ca, Sr) but also for elements usually representative of lithogenic particles (e.g., Al, Fe, Ti). More particularly Al vs. Fe fluxes appear to be strongly bimodal: Al fluxes are generally higher in northern traps while Fe fluxes are higher in AZ and PFZ traps; moreover single data points of both traps are distributed over two clear correlation lines, each one displaying little scattering. This suggests that the types of Fe- and/or Al- bearing particles vary more seasonally than spatially. In contrast, Ba fluxes, which are used in paleo-oceanography as a proxy of export production, are very similar to Ca fluxes, whatever the location. This suggests that carbonate productivity is more prone to deep carbon export compared to opal

  12. An Observing System for the Southern Ocean

    Science.gov (United States)

    Newman, L.; Schofield, O.; Wahlin, A.; Constable, A.; Swart, S.

    2016-02-01

    The Southern Ocean is fundamental to the operation of the Earth system, as it plays a central role in global climate and planetary-scale biogeochemical cycles. The Southern Ocean is changing rapidly, and the critical need to observe and understand the Southern Ocean is well established; however, the harsh conditions and remote location have led to it being the most under-sampled region of the world. Sustained observations are required to detect, interpret, and respond to the physical, chemical, and biological changes that are, and will continue to be measured. The Southern Ocean Observing System (SOOS) is an international initiative with the mission to integrate the global assets and efforts of the international community to enhance data collection, provide access to datasets, and guide the development of strategic-sustained-multidisciplinary science in the Southern Ocean. This presentation will provide an update on SOOS implementation activities, key products and tools, and data management efforts.

  13. A Southern Ocean mode of multidecadal variability

    NARCIS (Netherlands)

    Le Bars, D.|info:eu-repo/dai/nl/326165150; Viebahn, J. P.; Dijkstra, H. A.|info:eu-repo/dai/nl/073504467

    2016-01-01

    A 250 year simulation of a strongly eddying global version of the Parallel Ocean Program (POP) model reveals a new mode of intrinsic multidecadal variability, the Southern Ocean Mode (SOM), with a period of 40-50 year. The peak-to-peak difference in the global ocean heat content within a

  14. Dissolved aluminium in the Southern Ocean

    NARCIS (Netherlands)

    Middag, R.; van Slooten, C.; de Baar, H. J. W.; Laan, P.

    2011-01-01

    Dissolved aluminium (Al) occurs in a wide range of concentrations in the world oceans. The concentrations of Al in the Southern Ocean are among the lowest ever observed. An all-titanium CTD sampling system makes it possible to study complete deep ocean sections of Al and other trace elements with

  15. South African southern ocean research programme

    CSIR Research Space (South Africa)

    SASCAR

    1987-01-01

    Full Text Available This document describes the South African National Antarctic Research Programme's (SANARP) physical, chemical and biological Southern Ocean research programme. The programme has three main components: ecological studies of the Prince Edward Islands...

  16. New Perspectives on Southern Ocean Frontal Variability

    Science.gov (United States)

    Chapman, Christopher

    2017-04-01

    The frontal structure of the Southern Ocean is investigated using a the Wavelet/Higher Order Statistics Enhancement (WHOSE) frontal detection method, introduced in Chapman (2014). This methodology is applied to 21 years of daily gridded sea-surface height (SSH) data to obtain daily maps of the locations of the fronts. By forming frontal occurrence frequency maps and then approximating these occurrence-maps by a superposition of simple functions, the time-mean locations of the fronts, as well as a measure of their capacity to meander, are obtained and related to the frontal locations found by previous studies. The spatial and temporal variability of the frontal structure is then considered. The number of fronts is found to be highly variable throughout the Southern Ocean, increasing (`splitting') downstream of large bathymetric features and decreasing (`merging') in regions where the fronts are tightly controlled by the underlying topography. In contrast, frontal meandering remains relatively constant. Contrary to many previous studies, little no southward migration of the fronts over the 1993-2014 time period is found, and there is only weak sensitivity to atmospheric forcing related to SAM or ENSO. Finally, the implications of splitting and merging for the flux of tracers will be discussed.

  17. Climatically driven fluctuations in Southern Ocean ecosystems.

    Science.gov (United States)

    Murphy, Eugene J; Trathan, Philip N; Watkins, Jon L; Reid, Keith; Meredith, Michael P; Forcada, Jaume; Thorpe, Sally E; Johnston, Nadine M; Rothery, Peter

    2007-12-22

    Determining how climate fluctuations affect ocean ecosystems requires an understanding of how biological and physical processes interact across a wide range of scales. Here we examine the role of physical and biological processes in generating fluctuations in the ecosystem around South Georgia in the South Atlantic sector of the Southern Ocean. Anomalies in sea surface temperature (SST) in the South Pacific sector of the Southern Ocean have previously been shown to be generated through atmospheric teleconnections with El Niño Southern Oscillation (ENSO)-related processes. These SST anomalies are propagated via the Antarctic Circumpolar Current into the South Atlantic (on time scales of more than 1 year), where ENSO and Southern Annular Mode-related atmospheric processes have a direct influence on short (less than six months) time scales. We find that across the South Atlantic sector, these changes in SST, and related fluctuations in winter sea ice extent, affect the recruitment and dispersal of Antarctic krill. This oceanographically driven variation in krill population dynamics and abundance in turn affects the breeding success of seabird and marine mammal predators that depend on krill as food. Such propagating anomalies, mediated through physical and trophic interactions, are likely to be an important component of variation in ocean ecosystems and affect responses to longer term change. Population models derived on the basis of these oceanic fluctuations indicate that plausible rates of regional warming of 1oC over the next 100 years could lead to more than a 95% reduction in the biomass and abundance of krill across the Scotia Sea by the end of the century.

  18. The Future of Southern Ocean Observing Systems

    Science.gov (United States)

    Talley, L. D.

    2015-12-01

    Knowledge of the Southern Ocean's role in global climate from seasonal to millennial timescales is evolving, with rapidly increasing recognition of the centrality of the Southern Ocean to Earth's heat, carbon, nutrient, and freshwater budgets, and of the impact of interactions between the ocean and the major ice shelves and grounded ice sheets of Antarctica, which have been decreasing in mass. Observations in this data-sparse and logistically remote region have never been so important, and many nations are rising to the challenge of supporting both experiments and long-term sustained observations. As illustrated in the figure from Meredith et al. (Current Op. Env. Sustain. 2013), autonomous in situ technologies are at the fore because of the difficulty and expense of sending ships year-round and because the crucial satellite remote sensing must be accompanied by in situ observations, including beneath sea ice and ice shelves. The Southern Ocean Observing System (SOOS) has grown out of this recognized need for coordinated observations from the Antarctic coastline northward to the subtropics, from the bottom water production regions in coastal polynyas over the continental shelves, to the regions of interaction of warm ocean waters with Antarctic ice shelves, beneath the vast seasonal sea ice region, and in the hot spots of air-sea fluxes and cross-Antarctic Circumpolar Current (ACC) mixing where the ACC interacts with topography and continental boundaries. The future includes international coordination and collaboration and strengthening of new and existing technologies, which include satellite observing, ice-enabled profiling floats, profiling from marine mammals, moored measurements in many strategic locations, glider and other autonomous operations in all regions, and drilling through floating ice shelves to measure the ocean waters below. Improved and consistent weather observations around the Antarctic coastlines will improve forecasting and reanalysis. Ice

  19. Plutonium in Southern Hemisphere ocean Waters

    DEFF Research Database (Denmark)

    Hirose, K.; Aoyama, M.; Gastaud, J.

    2013-01-01

    Plutonium in seawater collected by the BEAGLE2003 cruise was determined using ICP- SF-MS and alpha spectrometry after Fe co-precipitation and radiochemical purification. Levels and distributions of dissolved plutonium activity concentrations in Southern Hemisphere ocean waters are summarized here......, including historical data. Pu-239 concentrations in surface water----of the central South Pacific (32.5 °S) in 2003 were around 1 mBq/m3. The 239Pu concentrations in the Indian Ocean surface waters (20°S) were similar to that in the South Pacific, whereas the 239Pu concentrations in the South Atlantic...... surface waters (30°S) were markedly lower than those in the South Pacific and Indian Oceans. The 239Pu vertical profile pattern was similar to that in the North Pacific subtropical gyre, although 239Pu concentrations in the deep South Pacific were significantly lower than those in the North Pacific. One...

  20. Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation

    OpenAIRE

    H. B. DeJong; R. B. Dunbar; D. A. Mucciarone; D. A. Koweek

    2015-01-01

    Predicting when surface waters of the Ross Sea and Southern Ocean will become undersaturated with respect to biogenic carbonate minerals is challenging in part due to the lack of baseline high resolution carbon system data. Here we present ~ 1700 surface total alkalinity measurements from the Ross Sea and along a transect between the Ross Sea and southern Chile from the austral autumn (February–March 2013). We calculate the saturation stat...

  1. Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation

    OpenAIRE

    H. B. DeJong; R. B. Dunbar; Mucciarone, D.; D. A. Koweek

    2015-01-01

    Predicting when surface waters of the Ross Sea and Southern Ocean will become undersaturated with respect to biogenic carbonate minerals is challenging in part due to the lack of baseline high-resolution carbon system data. Here we present ~ 1700 surface total alkalinity measurements from the Ross Sea and along a transect between the Ross Sea and southern Chile from the austral autumn (February–March 2013). We calculate the saturation state of aragonite (ΩAr) and calci...

  2. Modeling phytoplankton blooms and carbon export production in the Southern Ocean : dominant controls by light and iron in the Atlantic sector in Austral spring 1992

    NARCIS (Netherlands)

    Lancelot, C; Hannon, E; Becquevort, S; Veth, C.; de Baar, H.J.W.

    The high nutrient low chlorophyll (HNLC) conditions of the Southern Ocean were explored with an ecological model (SWAMCO) describing the cycling of C, N, P, Si and Fe through different, aggregated, chemical and biological compartments of the plankton ecosystem. The structure of the model was chosen

  3. Ecology of southern ocean pack ice.

    Science.gov (United States)

    Brierley, Andrew S; Thomas, David N

    2002-01-01

    Around Antarctica the annual five-fold growth and decay of sea ice is the most prominent physical process and has a profound impact on marine life there. In winter the pack ice canopy extends to cover almost 20 million square kilometres--some 8% of the southern hemisphere and an area larger than the Antarctic continent itself (13.2 million square kilometres)--and is one of the largest, most dynamic ecosystems on earth. Biological activity is associated with all physical components of the sea-ice system: the sea-ice surface; the internal sea-ice matrix and brine channel system; the underside of sea ice and the waters in the vicinity of sea ice that are modified by the presence of sea ice. Microbial and microalgal communities proliferate on and within sea ice and are grazed by a wide range of proto- and macrozooplankton that inhabit the sea ice in large concentrations. Grazing organisms also exploit biogenic material released from the sea ice at ice break-up or melt. Although rates of primary production in the underlying water column are often low because of shading by sea-ice cover, sea ice itself forms a substratum that provides standing stocks of bacteria, algae and grazers significantly higher than those in ice-free areas. Decay of sea ice in summer releases particulate and dissolved organic matter to the water column, playing a major role in biogeochemical cycling as well as seeding water column phytoplankton blooms. Numerous zooplankton species graze sea-ice algae, benefiting additionally because the overlying sea-ice ceiling provides a refuge from surface predators. Sea ice is an important nursery habitat for Antarctic krill, the pivotal species in the Southern Ocean marine ecosystem. Some deep-water fish migrate to shallow depths beneath sea ice to exploit the elevated concentrations of some zooplankton there. The increased secondary production associated with pack ice and the sea-ice edge is exploited by many higher predators, with seals, seabirds and whales

  4. Microphysics and Southern Ocean Cloud Feedback

    Science.gov (United States)

    McCoy, Daniel T.

    Global climate models (GCMs) change their cloud properties in the Southern Ocean (SO) with warming in a qualitatively consistent fashion. Cloud albedo increases in the mid-latitudes and cloud fraction decreases in the subtropics. This creates a distinctive 'dipole' structure in the SW cloud feedback. However, the shape of the dipole varies from model to model. In this thesis we discuss the microphysical mechanisms underlying the SW cloud feedback over the mid-latitude SO. We will focus on the negative lobe of the dipole. The negative SW cloud feedback in the mid-latitudes is created by transitions from ice to liquid in models. If ice transitions to liquid in mixed-phase clouds the cloud albedo increases because ice crystals are larger than liquid droplets and therefore more reflective for a constant mass of water. Decreases in precipitation efficiency further enhance this effect by decreasing sinks of cloud water. This transition is dependent on the mixed-phase cloud parameterization. Parameterizations vary wildly between models and GCMs disagree by up to 35 K on the temperature where ice and liquid are equally prevalent. This results in a wide spread in the model predictions of the increase in liquid water path (LWP, where the path is the vertically integrated mass of water) with warming that drives the negative optical depth cloud feedback. It is found that this disagreement also results in a wide array of climate mean-states as models that create liquid at lower temperatures have a higher mean-state LWP, lower ice water path (IWP), and higher condensed (ice and liquid) water path (CWP). This presents a problem in climate models. GCMs need to have a reasonable planetary albedo in their climate mean-state. We show evidence that GCMs have tuned cloud fraction to compensate for the variation in mid-latitude cloud albedo driven by the mixed-phase cloud parameterization. This tuning results in mid-latitude clouds that are both too few and too bright as well as a

  5. Late Holocene diatom-based sea-surface temperature reconstruction from the Conrad Rise, Southern Ocean

    Science.gov (United States)

    Orme, Lisa; Mietinnen, Arto; Crosta, Xavier; Mohan, Rahul

    2017-04-01

    The Southern Ocean plays an important role in the global climate system. The temperature and sea ice extent alter the latitudinal temperature gradient of the Southern Ocean, which can be transferred to the atmosphere resulting in changes in the southern westerly winds. The temperature, sea ice and wind variations are also factors influencing Antarctic Bottom Water formation, which is a control on the strength of the Atlantic Meridional Overturning Circulation. Therefore conditions in the Southern Ocean may influence the climate in the northern and southern hemispheres. The Southern Ocean and North Atlantic were connected during the Last Glacial during Dansgaard-Oeschger events, when variations in ocean circulation caused a bipolar seesaw of temperatures. For the Holocene there is less evidence for a bipolar seesaw, although recent research shows concurrent, opposite trends in ocean circulation in the North Atlantic and in the Southern Ocean. Further reconstructions are required from the Southern Ocean in particular to enable greater understanding of how the temperature and sea ice varied during the Holocene. The OCTEL project (Ocean-sea-ice-atmosphere teleconnections between the Southern Ocean and North Atlantic during the Holocene) aims to investigate the ocean, atmosphere and sea-ice teleconnections for the Holocene using new, high resolution records from both the Southern Ocean and North Atlantic. We here present initial results from diatom analysis conducted on a sediment core from the Southern Ocean, sampled from the Conrad Rise (54˚ 16.04'S, 39˚ 45.98'W). The preliminary results highlight a dominance of diatom species Fragilariopsis kerguelensis and Thalassiosira lentiginosa, with lower abundances of Thalassiothrix antarctica and Thalassiosira gracilis among others, which suggests an open ocean setting close to the polar front. The diatom data will be converted to quantitative reconstructions of summer sea surface temperature and sea ice presence using the

  6. New Hampshire / Southern Maine Ocean Uses Atlas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

  7. The SOOS Data Portal, providing access to Southern Oceans data

    Science.gov (United States)

    Proctor, Roger; Finney, Kim; Blain, Peter; Taylor, Fiona; Newman, Louise; Meredith, Mike; Schofield, Oscar

    2013-04-01

    The Southern Ocean Observing System (SOOS) is an international initiative to enhance, coordinate and expand the strategic observations of the Southern Oceans that are required to address key scientific and societal challenges. A key component of SOOS will be the creation and maintenance of a Southern Ocean Data Portal to provide improved access to historical and ongoing data (Schofield et al., 2012, Eos, Vol. 93, No. 26, pp 241-243). The scale of this effort will require strong leveraging of existing data centres, new cyberinfrastructure development efforts, and defined data collection, quality control, and archiving procedures across the international community. The task of assembling the SOOS data portal is assigned to the SOOS Data Management Sub-Committee. The information infrastructure chosen for the SOOS data portal is based on the Australian Ocean Data Network (AODN, http://portal.aodn.org.au). The AODN infrastructure is built on open-source tools and the use of international standards ensures efficiency of data exchange and interoperability between contributing systems. OGC standard web services protocols are used for serving of data via the internet. These include Web Map Service (WMS) for visualisation, Web Feature Service (WFS) for data download, and Catalogue Service for Web (CSW) for catalogue exchange. The portal offers a number of tools to access and visualize data: - a Search link to the metadata catalogue enables search and discovery by simple text search, by geographic area, temporal extent, keyword, parameter, organisation, or by any combination of these, allowing users to gain access to further information and/or the data for download. Also, searches can be restricted to items which have either data to download, or attached map layers, or both - a Map interface for discovery and display of data, with the ability to change the style and opacity of layers, add additional data layers via OGC Web Map Services, view animated timeseries datastreams

  8. Phytoplankton composition and biomass across the southern Indian Ocean

    DEFF Research Database (Denmark)

    Schlüter, Louise; Henriksen, Peter; Nielsen, Torkel Gissel

    2011-01-01

    Phytoplankton composition and biomass was investigated across the southern Indian Ocean. Phytoplankton composition was determined from pigment analysis with subsequent calculations of group contributions to total chlorophyll a (Chl a) using CHEMTAX and, in addition, by examination in the microscope...

  9. Seabird guano enhances phytoplankton production in the Southern Ocean.

    Science.gov (United States)

    Shatova, Olga; Wing, Stephen; Hoffmann, Linn; Jack, Lucy; Gault-Ringold, Melanie

    2015-04-01

    Great congregations of seabirds in sub-Antarctic and Antarctic coastal areas result in delivery of nutrient-rich guano to marine ecosystems that potentially enhances productivity and supports biodiversity in the region. Guano-derived bio-available micronutrients and macronutrients might be utilized by marine phytoplankton for photosynthetic production, however, mechanisms and significance of guano fertilization in the Southern Ocean are largely understudied. Over austral summers of 2012 and 2013 we performed a series of guano-enrichment phytoplankton incubation experiments with water samples collected from three different water masses in the Southern Ocean: Antarctic waters of the Ross sea and sub-Antarctic waters offshore the Otago Peninsula, both showing iron limitation of phytoplankton productivity in summer, and in the subtropical frontal zone offshore from the Snares Islands, which is generally micronutrient-repleted. Samples were enriched with known concentrations of guano-derived nutrients. Phytoplankton biomass increased significantly in guano-treated samples during all three incubation experiments (7-10 fold increase), while remained low in control samples. This response indicates that seabird guano provides nutrients that limit primary production in the Southern Ocean and that these nutrients are readily taken up by phytoplankton. Guano additions were compared to Fe and Macronutrient treatments (both added in quantities similar to those in the guano treatment). Phytoplankton biomass increased significantly in response to the Macronutrient treatment in the subtropical frontal zone, however, the response had a smaller magnitude compared to the guano treatment (2.8 µgL-1 vs 5.2 µgL-1) ; there was no significant effect of Fe on phytoplankton growth. This suggests the potential importance of synergistic effects of nutrients in guano. Incubation with sub-Antarctic waters showed that Fe and Macronutrients might be equally important for enhancement of

  10. Research Ship Southern Surveyor Underway Meteorological Data, Quality Controlled

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Research Ship Southern Surveyor Underway Meteorological Data (delayed ~10 days for quality control) are from the Shipboard Automated Meteorological and Oceanographic...

  11. Recent changes in the ventilation of the southern oceans.

    Science.gov (United States)

    Waugh, Darryn W; Primeau, Francois; Devries, Tim; Holzer, Mark

    2013-02-01

    Surface westerly winds in the Southern Hemisphere have intensified over the past few decades, primarily in response to the formation of the Antarctic ozone hole, and there is intense debate on the impact of this on the ocean's circulation and uptake and redistribution of atmospheric gases. We used measurements of chlorofluorocarbon-12 (CFC-12) made in the southern oceans in the early 1990s and mid- to late 2000s to examine changes in ocean ventilation. Our analysis of the CFC-12 data reveals a decrease in the age of subtropical subantarctic mode waters and an increase in the age of circumpolar deep waters, suggesting that the formation of the Antarctic ozone hole has caused large-scale coherent changes in the ventilation of the southern oceans.

  12. Tropical teleconnections via the ocean and atmosphere induced by Southern Ocean deep convective events

    Science.gov (United States)

    Marinov, I.; Cabre, A.; Gunn, A.; Gnanadesikan, A.

    2016-12-01

    The current generation (CMIP5) of Earth System Models (ESMs) shows a huge variability in their ability to represent Southern Ocean (SO) deep-ocean convection and Antarctic Bottom Water, with a preference for open-sea convection in the Weddell and Ross gyres. A long control simulation in a coarse 3o resolution ESM (the GFDL CM2Mc model) shows a highly regular multi-decadal oscillation between periods of SO open sea convection and non-convective periods. This process also happens naturally, with different frequencies and durations of convection across most CMIP5 models under preindustrial forcing (deLavergne et al, 2014). Here we assess the impact of SO deep convection and resulting sea surface temperature (SST) anomalies on the tropical atmosphere and ocean via teleconnections, with a focus on interannual to multi-decadal timescales. We combine analysis of our low-resolution coupled model with inter-model analysis across historical CMIP5 simulations. SST cooling south of 60S during non-convective decades triggers a stronger, northward shifted SH Hadley cell, which results in intensified northward cross-equatorial moist heat transport and a poleward shift in the ITCZ. Resulting correlations between the cross-equatorial atmospheric heat transport and ITCZ location are in good agreement with recent theories (e.g. Frierson et al. 2013; Donohoe et al. 2014). Lagged correlations between a SO convective index and cross-equatorial heat transports (in the atmosphere and ocean), as well as various tropical (and ENSO) climate indices are analyzed. In the ocean realm, we find that non-convective decades result in weaker AABW formation and weaker ACC but stronger Antarctic Intermediate Water (AAIW) formation, likely as a result of stronger SO westerlies (more positive SAM). The signals of AABW and AAIW are seen in the tropics on short timescales of years to decades in the temperature, heat storage and heat transport anomalies and also in deep and intermediate ocean oxygen. Most

  13. Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation

    Science.gov (United States)

    DeJong, H. B.; Dunbar, R. B.; Mucciarone, D. A.; Koweek, D.

    2016-02-01

    Predicting when surface waters of the Ross Sea and Southern Ocean will become undersaturated with respect to biogenic carbonate minerals is challenging in part due to the lack of baseline high resolution carbon system data. Here we present 1700 surface total alkalinity measurements from the Ross Sea and along a transect between the Ross Sea and southern Chile from the austral autumn (February-March 2013). We calculate the saturation state of aragonite (ΩAr) and calcite (ΩCa) using measured total alkalinity and pCO2. In the Ross Sea and south of the Polar Front, variability in carbonate saturation state (Ω) is mainly driven by algal photosynthesis. Freshwater dilution and calcification have minimal influence on Ω variability. We estimate an early spring surface water ΩAr value of 1.2 for the Ross Sea using a total alkalinity-salinity relationship and historical pCO2 measurements. Our results suggest that the Ross Sea is not likely to become undersaturated with respect to aragonite until the year 2070.

  14. Sea ice and climate feedbacks in the Southern Ocean

    Science.gov (United States)

    Frew, Rebecca; Feltham, Daniel; Holland, Paul

    2017-04-01

    Arctic sea ice is melting rapidly under the effects of climate change, but at the same time Antarctic sea ice is actually expanding overall. Understanding the reasons for this difference could provide significant insight into the workings of polar climate change. The behaviour of sea ice is not simple to understand because it is an integral part of the wider climate system, with many feedbacks affecting its evolution. For example, snow-covered sea ice is much more reflective than seawater, so if some ice is lost, the ice-ocean system will absorb more heat in summer, leading to further ice loss. There are several other important feedbacks, including examples associated with the insulating properties of sea ice, and the mixing of ocean heat up towards the surface as the ice forms. For example, during sea ice growth, the thickness of ice controls the growth rate, with the rate of growth decreasing as the ice thickens due to poorer heat conduction through the thick ice. On the other hand, increased melting of sea ice decreases the salinity of the mixed layer, therefore raising the freezing temperature of the seawater, making it easier to grow more sea ice. It is important to understand these feedbacks in the Southern Ocean surrounding Antarctica for many reasons. The changes in Antarctic sea ice over the last thirty years have a strong seasonal dependence, and the way that these changes grow in spring and decay in autumn suggests that feedbacks are strongly involved. The changes might ultimately be caused by winds, atmospheric warming, snowfall changes, etc., but we cannot understand these forcings without first untangling the feedbacks. A highly simplified coupled sea ice-mixed layer model has been developed to investigate the impact of feedbacks on the behaviour of sea ice in the Southern Ocean. The latest generation of climate models are very poor at modelling Antarctic sea ice. Solving this problem is of crucial importance to predicting the response of Antarctic

  15. Consistency of cruise data of the CARINA database in the Atlantic sector of the Southern Ocean

    Directory of Open Access Journals (Sweden)

    M. Hoppema

    2009-12-01

    Full Text Available Initially a North Atlantic project, the CARINA carbon synthesis was extended to include the Southern Ocean. Carbon and relevant hydrographic and geochemical ancillary data from cruises all across the Arctic Mediterranean Seas, Atlantic and Southern Ocean were released to the public and merged into a new database as part of the CARINA synthesis effort. Of a total of 188 cruises, 37 cruises are part of the Southern Ocean, including 11 from the Atlantic sector. The variables from all Southern Ocean cruises, including dissolved inorganic carbon (TCO2, total alkalinity, oxygen, nitrate, phosphate and silicate, were examined for cruise-to-cruise consistency in one collective effort. Seawater pH and chlorofluorocarbons (CFCs are also part of the database, but the pH quality control (QC is described in another Earth System Science Data publication, while the complexity of the Southern Ocean physics and biogeochemistry prevented a proper QC analysis of the CFCs. The area-specific procedures of quality control, including crossover analysis between stations and inversion analysis of all crossover data (i.e. secondary QC, are briefly described here for the Atlantic sector of the Southern Ocean. Data from an existing, quality controlled database (GLODAP were used as a reference for our computations – however, the reference data were included into the analysis without applying the recommended GLODAP adjustments so the corrections could be independently verified. The outcome of this effort is an internally consistent, high-quality carbon data set for all cruises, including the reference cruises. The suggested corrections by the inversion analysis were allowed to vary within a fixed envelope, thus accounting for natural variability. The percentage of cruises adjusted ranged from 31% (for nitrate to 54% (for phosphate depending on the variable.

  16. Assessing the internal consistency of the CARINA database in the Indian sector of the Southern Ocean

    Directory of Open Access Journals (Sweden)

    C. Lo Monaco

    2010-02-01

    Full Text Available Carbon and carbon-relevant hydrographic and hydrochemical ancillary data from previously not publicly available cruises were retrieved and recently merged to a new data base, CARINA (CARbon IN the Atlantic. The initial North Atlantic project, an international effort for ocean carbon synthesis, was extended to include the Arctic Mediterranean Seas (Arctic Ocean and Nordic Seas and all three sectors of the Southern Ocean. Of a total of 188 cruises, 37 cruises are part of the Southern Ocean. The present work focuses on data collected in the Indian sector (20° S–70° S; 30° E–150° E. The Southern Indian Ocean dataset covers the period 1992–2004 and includes seasonal repeated observations. Parameters including salinity, dissolved inorganic carbon (TCO2, total alkalinity (TA, oxygen, nitrate, phosphate and silicate were examined for cruise-to-cruise and overall consistency. In addition, data from an existing, quality controlled data base (GLODAP were introduced in the CARINA analysis to improve data coverage in the Southern Ocean. A global inversion was performed to synthesize the information deduced from objective comparisons of deep measurements (>1500 m at nearby stations (generally <220 km. The corrections suggested by the inversion were allowed to vary within a fixed envelope, thus accounting for ocean interior variability. The adjustments applied to CARINA data and those recommended for GLODAP data, in order to obtain a consistent merged dataset, are presented and discussed. The final outcome of this effort is a new quality controlled data base for TCO2 and other properties of the carbon system that can now be used to investigate the natural variability or stability of ocean chemistry and the accumulation of anthropogenic carbon. This data product also offers an important new synthesis of seasonal to decadal observations to validate ocean biogeochemical models in a region where available historical data were very

  17. Petasaria heterolepis (Prymnesiaceae) from the southern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, S.; Mohan, R.; Gazi, S.; Shetye, S.; Jafar, S.A.

    Sea surface and sub-surface (0-110m) water samples were collected from the Southern Indian Ocean between 39�S and 65�S (along ~48�E and 57.3�E) during the austral summer of 2010 which yielded Petasaria heterolepis Out of the two known P heterolepis...

  18. Antarctic and Southern Ocean influences on Late Pliocene global cooling

    NARCIS (Netherlands)

    McKay, R.; Naish, T.; Carter, L.; Riesselman, C.; Dunbar, R.; Sjunneskog, C.; Winter, D.; Sangiorgi, F.; Warren, C.; Pagani, M.; Schouten, S.; Willmot, V.; Levy, R.; DeConto, R.; Powell, R.D.

    2012-01-01

    The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL

  19. Environmental and Climatological Evolution of the early Paleogene Southern Ocean

    NARCIS (Netherlands)

    Bijl, P.K.

    2011-01-01

    Through application of palynological and organic geochemical tools, this thesis provides a detailed image of the early Paleogene greenhouse-icehouse transition of the Southern Ocean. The organic-walled dinoflagellate cyst (dinocyst) zonation for a large part of the early Paleogene may serve as guide

  20. Killer whales ( Orcinus orca ) at Marion Island, Southern Ocean ...

    African Journals Online (AJOL)

    Killer whales (Orcinus orca) were studied using data obtained on an opportunistic basis between 1973 and 1996 at Marion Island (46°54'S, 37°45'E) in the Southern Indian Ocean. A clear seasonal pattern of occurrence with the main peak between October and December was evident. Most killer whales were observed ...

  1. Banding of seabirds in the Southern Ocean has been undertaken ...

    African Journals Online (AJOL)

    spamer

    and the South African Prince Edward Islands, 1 068 km apart in the Southern Ocean. Most movements of banded birds (57) have ... two, one of which was dead, at Prince Edward Island). Age-class at banding is unknown for one .... Exclusive Economic Zones (EEZs), perhaps by way of a joint Plan of Action (FAO 2001); ...

  2. Insular endemism in Recent Southern Ocean benthic Ostracoda from Marion Island: palaeozoogeographical and evolutionary implications

    DEFF Research Database (Denmark)

    Dingle, R.V.

    2002-01-01

    benthic ostracods, subantarctic, endemism, insularity, Marion Island, Southern Ocean, colonisation, quaternary, eyes, ocular-rejuvenation, dormant genes, evolution......benthic ostracods, subantarctic, endemism, insularity, Marion Island, Southern Ocean, colonisation, quaternary, eyes, ocular-rejuvenation, dormant genes, evolution...

  3. Anthropogenic carbon dioxide transport in the Southern Ocean driven by Ekman flow.

    Science.gov (United States)

    Ito, T; Woloszyn, M; Mazloff, M

    2010-01-07

    The Southern Ocean, with its large surface area and vigorous overturning circulation, is potentially a substantial sink of anthropogenic CO(2) (refs 1-4). Despite its importance, the mechanism and pathways of anthropogenic CO(2) uptake and transport are poorly understood. Regulation of the Southern Ocean carbon sink by the wind-driven Ekman flow, mesoscale eddies and their interaction is under debate. Here we use a high-resolution ocean circulation and carbon cycle model to address the mechanisms controlling the Southern Ocean sink of anthropogenic CO(2). The focus of our study is on the intra-annual variability in anthropogenic CO(2) over a two-year time period. We show that the pattern of carbon uptake is correlated with the oceanic vertical exchange. Zonally integrated carbon uptake peaks at the Antarctic polar front. The carbon is then advected away from the uptake regions by the circulation of the Southern Ocean, which is controlled by the interplay among Ekman flow, ocean eddies and subduction of water masses. Although lateral carbon fluxes are locally dominated by the imprint of mesoscale eddies, the Ekman transport is the primary mechanism for the zonally integrated, cross-frontal transport of anthropogenic CO(2). Intra-annual variability of the cross-frontal transport is dominated by the Ekman flow with little compensation from eddies. A budget analysis in the density coordinate highlights the importance of wind-driven transport across the polar front and subduction at the subtropical front. Our results suggest intimate connections between oceanic carbon uptake and climate variability through the temporal variability of Ekman transport.

  4. Contribution of topographically generated submesoscale turbulence to Southern Ocean overturning

    Science.gov (United States)

    Ruan, Xiaozhou; Thompson, Andrew F.; Flexas, Mar M.; Sprintall, Janet

    2017-11-01

    The ocean's global overturning circulation regulates the transport and storage of heat, carbon and nutrients. Upwelling across the Southern Ocean's Antarctic Circumpolar Current and into the mixed layer, coupled to water mass modification by surface buoyancy forcing, has been highlighted as a key process in the closure of the overturning circulation. Here, using twelve high-resolution hydrographic sections in southern Drake Passage, collected with autonomous ocean gliders, we show that Circumpolar Deep Water originating from the North Atlantic, known as Lower Circumpolar Deep Water, intersects sloping topography in narrow and strong boundary currents. Observations of strong lateral buoyancy gradients, enhanced bottom turbulence, thick bottom mixed layers and modified water masses are consistent with growing evidence that topographically generated submesoscale flows over continental slopes enhance near-bottom mixing, and that cross-density upwelling occurs preferentially over sloping topography. Interactions between narrow frontal currents and topography occur elsewhere along the path of the Antarctic Circumpolar Current, which leads us to propose that such interactions contribute significantly to the closure of the overturning in the Southern Ocean.

  5. Ocean sea-ice modelling in the Southern Ocean around Indian ...

    Indian Academy of Sciences (India)

    An eddy-resolving coupled ocean sea-ice modelling is carried out in the Southern Ocean region (9∘–78∘E; 51∘–71∘S) using the MITgcm. The model domain incorporates the Indian Antarctic stations, Maitri (11.7∘E; 70.7∘S) and Bharati (76.1∘E; 69.4∘S). The realistic simulation of the surface variables, namely, sea ...

  6. A biologically relevant method for considering patterns of oceanic retention in the Southern Ocean

    Science.gov (United States)

    Mori, Mao; Corney, Stuart P.; Melbourne-Thomas, Jessica; Klocker, Andreas; Sumner, Michael; Constable, Andrew

    2017-12-01

    Many marine species have planktonic forms - either during a larval stage or throughout their lifecycle - that move passively or are strongly influenced by ocean currents. Understanding these patterns of movement is important for informing marine ecosystem management and for understanding ecological processes generally. Retention of biological particles in a particular area due to ocean currents has received less attention than transport pathways, particularly for the Southern Ocean. We present a method for modelling retention time, based on the half-life for particles in a particular region, that is relevant for biological processes. This method uses geostrophic velocities at the ocean surface, derived from 23 years of satellite altimetry data (1993-2016), to simulate the advection of passive particles during the Southern Hemisphere summer season (from December to March). We assess spatial patterns in the retention time of passive particles and evaluate the processes affecting these patterns for the Indian sector of the Southern Ocean. Our results indicate that the distribution of retention time is related to bathymetric features and the resulting ocean dynamics. Our analysis also reveals a moderate level of consistency between spatial patterns of retention time and observations of Antarctic krill (Euphausia superba) distribution.

  7. High Biomass Low Export Regimes in the Southern Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Phoebe J.; Bishop, James K.B.

    2006-01-27

    This paper investigates ballasting and remineralization controls of carbon sedimentation in the twilight zone (100-1000 m) of the Southern Ocean. Size-fractionated (<1 {micro}m, 1-51 {micro}m, >51 {micro}m) suspended particulate matter was collected by large volume in-situ filtration from the upper 1000 m in the Subantarctic (55 S, 172 W) and Antarctic (66 S, 172 W) zones of the Southern Ocean during the Southern Ocean Iron Experiment (SOFeX) in January-February 2002. Particles were analyzed for major chemical constituents (POC, P, biogenic Si, CaCO3), and digital and SEM image analyses of particles were used to aid in the interpretation of the chemical profiles. Twilight zone waters at 66 S in the Antarctic had a steeper decrease in POC with depth than at 55 S in the Subantarctic, with lower POC concentrations in all size fractions at 66 S than at 55 S, despite up to an order of magnitude higher POC in surface waters at 66 S. The decay length scale of >51 {micro}m POC was significantly shorter in the upper twilight zone at 66 S ({delta}{sub e}=26 m) compared to 55 S ({delta}{sub e}=81 m). Particles in the carbonate-producing 55 S did not have higher excess densities than particles from the diatom-dominated 66 S, indicating that there was no direct ballast effect that accounted for deeper POC penetration at 55 S. An indirect ballast effect due to differences in particle packaging and porosities cannot be ruled out, however, as aggregate porosities were high ({approx}97%) and variable. Image analyses point to the importance of particle loss rates from zooplankton grazing and remineralization as determining factors for the difference in twilight zone POC concentrations at 55 S and 66 S, with stronger and more focused shallow remineralization at 66 S. At 66 S, an abundance of large (several mm long) fecal pellets from the surface to 150 m, and almost total removal of large aggregates by 200 m, reflected the actions of a single or few zooplankton species capable of

  8. Organic complexation of iron in the Southern Ocean

    NARCIS (Netherlands)

    Boye, Marie; Berg, Constant M.G. van den; Jong, Jeroen T.M. de; Leach, Harry; Croot, Peter; Baar, Hein J.W. de

    2001-01-01

    The chemical speciation of iron was determined in the Southern Ocean along a transect from 48 to 70°S at 20°E. Dissolved iron concentrations were low at 0.1–0.6 nM, with average concentrations of 0.25±0.13 nM. Organic iron complexing ligands were found to occur in excess of the dissolved iron

  9. Krill excretion boosts microbial activity in the Southern Ocean.

    Directory of Open Access Journals (Sweden)

    Javier Arístegui

    Full Text Available Antarctic krill are known to release large amounts of inorganic and organic nutrients to the water column. Here we test the role of krill excretion of dissolved products in stimulating heterotrophic bacteria on the basis of three experiments where ammonium and organic excretory products released by krill were added to bacterial assemblages, free of grazers. Our results demonstrate that the addition of krill excretion products (but not of ammonium alone, at levels expected in krill swarms, greatly stimulates bacteria resulting in an order-of-magnitude increase in growth and production. Furthermore, they suggest that bacterial growth rate in the Southern Ocean is suppressed well below their potential by resource limitation. Enhanced bacterial activity in the presence of krill, which are major sources of DOC in the Southern Ocean, would further increase recycling processes associated with krill activity, resulting in highly efficient krill-bacterial recycling that should be conducive to stimulating periods of high primary productivity in the Southern Ocean.

  10. Modulation of the Southern Ocean cadmium isotope signature by ocean circulation and primary productivity

    NARCIS (Netherlands)

    Abouchami, W.; Galer, S.J.G.; de Baar, H.J.W.; Alderkamp, A.C.; Middag, R.; Laan, P.; Feldmann, H.; Andreae, M.O.

    2011-01-01

    The High Nutrient Low Chlorophyll (HNLC) Southern Ocean plays a key role in regulating the biological pump and the global carbon cycle. Here we examine the efficacy of stable cadmium (Cd) isotope fractionation for detecting differences in biological productivity between regions. Our results show

  11. Connecting tropical climate change with Southern Ocean heat uptake

    Science.gov (United States)

    Hwang, Yen-Ting; Xie, Shang-Ping; Deser, Clara; Kang, Sarah M.

    2017-09-01

    Under increasing greenhouse gas forcing, climate models project tropical warming that is greater in the Northern than the Southern Hemisphere, accompanied by a reduction in the northeast trade winds and a strengthening of the southeast trades. While the ocean-atmosphere coupling indicates a positive feedback, what triggers the coupled asymmetry and favors greater warming in the northern tropics remains unclear. Far away from the tropics, the Southern Ocean (SO) has been identified as the major region of ocean heat uptake. Beyond its local effect on the magnitude of sea surface warming, we show by idealized modeling experiments in a coupled slab ocean configuration that enhanced SO heat uptake has a profound global impact. This SO-to-tropics connection is consistent with southward atmospheric energy transport across the equator. Enhanced SO heat uptake results in a zonally asymmetric La-Nina-like pattern of sea surface temperature change that not only affects tropical precipitation but also has influences on the Asian and North American monsoons.

  12. Topographic enhancement of vertical turbulent mixing in the Southern Ocean

    Science.gov (United States)

    Mashayek, A.; Ferrari, R.; Merrifield, S.; Ledwell, J. R.; St Laurent, L.; Garabato, A. Naveira

    2017-03-01

    It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation.

  13. Mesoscale and submesoscale variability in Drake Passage, Southern Ocean: observations from ocean gliders

    Science.gov (United States)

    Thompson, A. F.; Flexas Sbert, M.; Sprintall, J.; Viglione, G.; Ruan, X.; Erickson, Z. K.

    2016-12-01

    The Southern Ocean is one of the most energetic regions of the global ocean. Its unique environment, characterized by strong, equivalent barotropic zonal flows and the outcropping of a broad range of density classes with outcrop, means that its mesoscale and submesoscale characteristics may be very different from other regions of the ocean. Observations of the Southern Ocean's subsurface velocity and density structure at mesoscale and submesoscale resolution are extremely limited. Here we present results deriving from observations collected by ocean gliders across two years. The first deployment, carried out during austral summer 2014-2015, used two gliders to focus on the interaction between the southern boundary of the Antarctic Circumpolar Current with the continental shelf and slope of the Antarctic Peninsula. Across three months of observations, we show that there are abrupt changes in mixed layer depths, eddy formation process and lateral surface buoyancy gradients occur across the Shackleton Fracture Zone (SFZ). We will also present recent observations from two ocean gliders deployed in southern Drake Passage in austral fall and winter, 2016 (May through August). These gliders completed multiple meridional transects across Drake Passage, including crossings of both the Polar Front and the Subantarctic Front. The gliders were flown in parallel for most of the mission with a spatial separation of approximately 10 km, permitting a three-dimensional calculation of buoyancy gradients in the upper 1000 m at submesoscale resolution. Preliminary results show that stratification and velocity structures indicative of submesoscale instabilities are strongly localized by the position of the ACC's frontal currents. Thin intrusions with vertical scales as small as 20 m as also pervasive in these frontal regions. This data set will be used to characterize the type and frequency of submesoscale instabilities that occur in winter when mixed layer depths are between 100 and

  14. Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation

    National Research Council Canada - National Science Library

    DeJong, H. B; Dunbar, R. B; Mucciarone, D; Koweek, D. A

    2015-01-01

    ...-resolution carbon system data. Here we present ~ 1700 surface total alkalinity measurements from the Ross Sea and along a transect between the Ross Sea and southern Chile from the austral autumn (February-March 2013...

  15. Early summer southern China rainfall variability and its oceanic drivers

    Science.gov (United States)

    Li, Weijing; Ren, Hong-Chang; Zuo, Jinqing; Ren, Hong-Li

    2017-09-01

    Rainfall in southern China reaches its annual peak in early summer (May-June) with strong interannual variability. Using a combination of observational analysis and numerical modeling, the present study investigates the leading modes of this variability and its dynamic drivers. A zonal dipole pattern termed the southern China Dipole (SCD) is found to be the dominant feature in early summer during 1979-2014, and is closely related to a low-level anomalous anticyclone over the Philippine Sea (PSAC) and a Eurasian wave-train pattern over the mid-high latitudes. Linear regressions based on observations and numerical experiments using the CAM5 model suggest that the associated atmospheric circulation anomalies in early summer are linked to decaying El Niño-Southern Oscillation-like sea surface temperature (SST) anomalies in the tropical Pacific, basin-scale SST anomalies in the tropical Indian Ocean, and meridional tripole-like SST anomalies in the North Atlantic in the previous winter to early summer. The tropical Pacific and Indian Ocean SST anomalies primarily exert an impact on the SCD through changing the polarity of the PSAC, while the North Atlantic tripole-like SST anomalies mainly exert a downstream impact on the SCD by inducing a Eurasian wave-train pattern. The North Atlantic tripole-like SST anomalies also make a relatively weak contribution to the variations of the PSAC and SCD through a subtropical teleconnection. Modeling results indicate that the three-basin combined forcing has a greater impact on the SCD and associated circulation anomalies than the individual influence from any single oceanic basin.

  16. Hydrographic characteristics of the Indian sector of the Southern Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shirodkar, P.V.; Somayajulu, Y.K.; Sarma, Y.V.B.; Rathod, V.

    sector of the Southern Ocean Page 3 of 11 file://C:\\My Documents\\articles16.htm 2/11/05 using the relation obtained by the analysis of sea water samples following Winklers’ titration method. The correlation of CTD DO values and the values obtained... through Winklers’ titration method gave the following equation: DOWink = DOCTD * 1.184175 + 0.430365, with correlation coefficient, r = 0.99. The above relation was used for correcting the CTD DO values. The analyses of calcium and magnesium were...

  17. Rapid ocean-atmosphere response to Southern Ocean freshening during the last glacial period

    Science.gov (United States)

    Turney, Christian; Jones, Richard; Phipps, Steven; Thomas, Zoë; Hogg, Alan; Kershaw, Peter; Fogwill, Christopher; Palmer, Jonathan; Bronk Ramsey, Christopher; Adolphi, Florian; Muscheler, Raimund; Hughen, Konrad; Staff, Richard; Grosvenor, Mark; Golledge, Nicholas; Rasmussen, Sune; Hutchinson, David; Haberle, Simon; Lorrey, Andrew; Boswijk, Gretel

    2017-04-01

    Contrasting Greenland and Antarctic temperature trends during the late last glacial period (60,000 to 11,703 years ago) are thought to be driven by imbalances in the rate of formation of North Atlantic and Antarctic Deep Water (the 'bipolar seesaw'), with cooling in the north leading the onset of warming in the south. Some events, however, appear to have occurred independently of changes in deep water formation but still have a southern expression, implying that an alternative mechanism may have driven some global climatic changes during the glacial. Testing these competing hypotheses is challenging given the relatively large uncertainties associated with correlating terrestrial, marine and ice core records of abrupt change. Here we exploit a bidecadally-resolved 14C calibration dataset obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate datasets spanning 28,400 to 30,400 years ago. We observe no divergence between terrestrial and marine 14C datasets implying limited impact of freshwater hosing on the Atlantic Meridional Overturning Circulation (AMOC). However, an ice-rafted debris event (SA2) in Southern Ocean waters appears to be associated with dramatic synchronous warming over the North Atlantic and contrasting precipitation patterns across the low latitudes. Using a fully coupled climate system model we undertook an ensemble of transient meltwater simulations and find that a southern salinity anomaly can trigger low-latitude temperature changes through barotropic and baroclinic oceanic waves that are atmospherically propagated globally via a Rossby wave train, consistent with contemporary modelling studies. Our results suggest the Antarctic ice sheets and Southern Ocean dynamics may have contributed to some global climatic changes through rapid ocean-atmospheric teleconnections, with implications for past (and future) change.

  18. Zooplankton excretion metabolites stimulate Southern Ocean phytoplankton growth

    KAUST Repository

    Coello-Camba, A.

    2017-04-24

    Warming over Antarctica is leading to changes in the zooplankton communities inhabiting the Southern Ocean. It has been observed that zooplankton not only regulates phytoplankton through grazing, but also through the recycling of nutrients that are essential for phytoplankton growth. In this way, the effects of warming on zooplankton populations will change the amount or proportion at which recycled nutrients are restored. To estimate how the recycled nutrients released by zooplankton populations, dominated by krill (Euphausia superba), amphipods or copepods, affect the phytoplankton uptake and communities, we performed four incubation experiments: two close to the Antarctic Peninsula and two at the Southern Atlantic Ocean. Our results showed a stimulating effect of the addition of metabolites on ammonia removal rates and on the net growth of phytoplankton communities, with different responses amongst the different phytoplankton groups. According to our results, phytoplankton net growth and community composition may be altered if this relevant source of nutrients is lost due to projected changes in the abundance or distribution of these zooplankton populations.

  19. Development of a southern oceanic air standard reference material.

    Science.gov (United States)

    Rhoderick, George C; Kelley, Michael E; Miller, Walter R; Brailsford, Gordon; Possolo, Antonio

    2016-02-01

    In 2009, the United States Congress charged the National Institute of Standards and Technology (NIST) with supporting climate change research. As part of this effort, the Gas Sensing Metrology Group at NIST began developing new gas standard mixtures for greenhouse gas mixtures relevant to atmospheric measurements. Suites of gravimetrically prepared primary standard mixtures (PSMs) were prepared at ambient concentration levels for carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in a dry-air balance. In parallel, 30 gas cylinders were filled, by the National Institute of Water and Atmospheric Research (NIWA) in Wellington, New Zealand, to high pressure from pristine southern oceanic air at Baring Head, New Zealand, and shipped to NIST. Using spectroscopic instrumentation, NIST analyzed the 30 cylinder samples for mole fractions of CO2, CH4, and N2O. Certified values were assigned to these mixtures by calibrating the instrumentation with the PSM suites that were recently developed at NIST. These mixtures became NIST Standard Reference Material (SRM) 1721 Southern Oceanic Air and are certified for ambient mole fraction, the first of their kind for NIST. The relative expanded uncertainties corresponding to coverage intervals with 95% probability are no larger than 0.06% of the certified values, representing the smallest uncertainties to date ever assigned to an NIST gas SRM.

  20. A new primnoid genus (Anthozoa: Octocorallia from the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Pablo J. López-González

    2002-12-01

    Full Text Available A new primnoid genus is here proposed based on the study of the type material of Primnoella gracilis Molander, 1929 and the abundant material collected during some recent Antarctic and Subantarctic cruises. The new genus, Arntzia, is compared with its closest primnoid genera, mainly Ainigmaptilon Dean and Primnoella Gray. Arntzia differs from other unbranched primnoids by a set of features such as its colonies of fleshy consistence, relatively low spicule density, polyps in whorls, fused basally, forming a common brood-chamber along the axial coenenchyme where oocytes develop, eight distalmost opercular scales larger than marginal or submarginal scales, two adaxial opercular scales smaller than the others, marginal scales in equal number to opercular, vertically aligned with opercular scales, not well-differentiated from the body scales below, and polyp body completely covered by scales, except for the proximal portion and basal part of the adaxial side. With the description of Arntzia, a total of 17 primnoid genera have been reported from the Southern Ocean (Antarctic and Subantarctic waters; moreover, 15 of them -50% of the total in the family- have been recorded exclusively in this area. Thus, the generic diversity of this family in the Southern Ocean should be considered remarkably high.

  1. On the fast response of the Southern Ocean to changes in the zonal wind

    Directory of Open Access Journals (Sweden)

    D. J. Webb

    2007-09-01

    Full Text Available Model studies of the Southern Ocean, reported here, show that the Antarctic Circumpolar Current responds within two days to changes in the zonal wind stress at the latitudes of Drake Passage. Further investigation shows that the response is primarily barotropic and that, as one might expect, it is controlled by topography. Analysis of the results show that the changes in the barotropic flow are sufficient to transfer the changed surface wind stress to the underlying topography and that during this initial phase baroclinic processes are not involved.

    The model results also show that the Deacon Cell responds to changes in the wind stress on the same rapid time scale. It is shown that the changes in the Deacon Cell can also be explained by the change in the barotropic velocity field, an increase in the zonal wind stress producing an increased northward flow in shallow regions and southward flow where the ocean is deep. This new explanation is unexpected as previously the Deacon Cell has been thought of as a baroclinic feature of the ocean.

    The results imply that where baroclinic processes do appear to be involved in either the zonal momentum balance of the Southern Ocean or the formation of the Deacon Cell, they are part of the long term baroclinic response of the ocean's density field to the changes in the barotropic flow.

  2. New Perspectives on Frontal Variability in the Southern Ocean Using a Local Identification Scheme

    CERN Document Server

    Chapman, Christopher C

    2016-01-01

    The frontal structure of the Southern Ocean is investigated using a sophisticated frontal detection methodology, the Wavelet/Higher Order Statistics Enhancement (WHOSE) method, introduced in \\cite{Chapman2014}. This methodology is applied to 21 years of daily gridded sea-surface height (SSH) data to obtain daily maps of the locations of the fronts. By forming `heat-maps' of the frontal occurrence frequency and then approximating these heat-maps by a superposition of simple functions, the time-mean locations of the fronts, as well as a measure of their capacity to meander, are obtained and related to the frontal locations found by previous studies. The spatial and temporal variability of the frontal structure is then considered. The number of fronts is found to be highly variable throughout the Southern Ocean, increasing (`splitting') downstream of large bathymetric features and decreasing (`merging') in regions where the fronts are tightly controlled by the underlying topography. In contrast, frontal meanderi...

  3. The role of Southern Ocean processes in orbital and millennial CO 2 variations - A synthesis

    Science.gov (United States)

    Fischer, Hubertus; Schmitt, Jochen; Lüthi, Dieter; Stocker, Thomas F.; Tschumi, Tobias; Parekh, Payal; Joos, Fortunat; Köhler, Peter; Völker, Christoph; Gersonde, Rainer; Barbante, Carlo; Le Floch, Martine; Raynaud, Dominique; Wolff, Eric

    2010-01-01

    Recent progress in the reconstruction of atmospheric CO 2 records from Antarctic ice cores has allowed for the documentation of natural CO 2 variations on orbital time scales over the last up to 800,000 years and for the resolution of millennial CO 2 variations during the last glacial cycle in unprecedented detail. This has shown that atmospheric CO 2 varied within natural bounds of approximately 170-300 ppmv but never reached recent CO 2 concentrations caused by anthropogenic CO 2 emissions. In addition, the natural atmospheric CO 2 concentrations show an extraordinary correlation with Southern Ocean climate changes, pointing to a significant (direct or indirect) influence of climatic and environmental changes in the Southern Ocean region on atmospheric CO 2 concentrations. Here, we compile recent ice core and marine sediment records of atmospheric CO 2, temperature and environmental changes in the Southern Ocean region, as well as carbon cycle model experiments, in order to quantify the effect of potential Southern Ocean processes on atmospheric CO 2 related to these orbital and millennial changes. This shows that physical and biological changes in the SO are able to explain substantial parts of the glacial/interglacial CO 2 change, but that none of the single processes is able to explain this change by itself. In particular, changes in the Southern Ocean related to changes in the surface buoyancy flux, which in return is controlled by the waxing and waning of sea ice may favorably explain the high correlation of CO 2 and Antarctic temperature on orbital and millennial time scales. In contrast, the changes of the position and strength of the westerly wind field were most likely too small to explain the observed changes in atmospheric CO 2 or may even have increased atmospheric CO 2 in the glacial. Also iron fertilization of the marine biota in the Southern Ocean contributes to a glacial drawdown of CO 2 but turns out to be limited by other factors than the total

  4. Oceanographic Research of Marine Hydrophysical Institute in the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Yu.V. Artamonov

    2016-12-01

    Full Text Available Basic stages of the oceanographic research carried out by Marine Hydrophysical Institute in the Southern ocean are considered. Each stage of the studies is illustrated by the schemes of expeditionary work; the most important results are presented. The oceanographic studies of Marine Hydrophysical Institute in the Southern ocean are shown to be developed in two basic directions: marine expeditionary research and analysis of the archival hydrometeorological data. Based on the results of expeditionary studies, the mechanisms of formation and variability of the water structure and circulation in the Antarctic coastal regions are described. Anomalies of hydrometeorological fields occurring along the route to Antarctica are assessed due to the measurements from the passing vessels. The archival hydrological and satellite data constitute a foundation for revealing the features of seasonal and interannual variability of the ocean surface temperature, fronts and sea ice in Antarctica. The effect of El Niño events on the interannual variation of the characteristics of Scotia Sea Front is revealed. It is shown that the formation of warm water positive anomaly areas in the tropical Pacific is caused by El Niño events. It’s accompanied by an appreciable displacement of the front to the south, by the weakening of its intensity and the decrease of temperature on the front axes. It is shown that maximum seasonal variation of the ice concentration is observed in the Weddell and Lazarev Seas. The ice in the Weddell, Amundsen and Bellingshausen Sea are shown to be exposed to the highest interannual variability.

  5. THE CD ISOTOPE SIGNATURE OF THE SOUTHERN OCEAN

    Science.gov (United States)

    Abouchami, W.; Galer, S. J.; Middag, R.; de Baar, H.; Andreae, M. O.; Feldmann, H.; Raczek, I.

    2009-12-01

    The availability of micronutrients can limit and control plankton ecosystems, notably in the Southern Ocean which plays a major role in regulating the CO2 biological pump. Cadmium has a nutrient-like distribution in seawater - it is directly incorporated into living plankton in the upper water column and re-mineralised at depth. The nutritional role of Cd (Price and Morel, 1990) makes it a potentially useful tracer of biological productivity. We report Cd concentration and Cd stable isotope data obtained using a double-spike TIMS method on seawater samples collected during the Zero and Drake Passage cruise (ANTXXIV-III, IPY-GEOTRACES 2008). Four vertical profiles were collected from 40 to 70°S across the Polar Front using the ultra-clean Titan frame (De Baar et al., 2008), providing a record of changes in biological productivity from the Subantarctic to the Antarctic region. Data from two profiles from the SE Atlantic (47.66°S, 4.28W) and Drake Passage (55.13°S, 65.53°W) obtained on 1 litre-sized samples are presented. Both profiles show a increase in Cd concentration with depth, with noticeably higher concentrations in the SE Atlantic. Cd and PO4 are positively correlated with distinct slopes for the two profiles. The Cd isotope data are expressed as ɛ112/110Cd relative to our JMC Mainz standard (± 8ppm, 2SD, N=17). ɛ112/110Cd values show a continuous decrease with increasing depth and a significant shift towards heavier values in the upper 400m at both stations resolvable outside analytical error (2SE ≤ 20ppm). The sense of Cd isotope fractionation confirms previous findings of uptake of “light” Cd by phytoplankton in the upper water column (Lacan et al., 2006; Ripperger et al., 2007; Schmidt et al., 2009). Most important is the evidence for a distinctive heavier Cd isotope signature in AASW relative to AAIW. This result demonstrates that different water masses carry distinct Cd isotopic compositions reflecting changes in Cd uptake by phytoplankton

  6. A data assimilating model for estimating Southern Ocean biogeochemistry

    Science.gov (United States)

    Verdy, A.; Mazloff, M. R.

    2017-09-01

    A Biogeochemical Southern Ocean State Estimate (B-SOSE) is introduced that includes carbon and oxygen fields as well as nutrient cycles. The state estimate is constrained with observations while maintaining closed budgets and obeying dynamical and thermodynamic balances. Observations from profiling floats, shipboard data, underway measurements, and satellites are used for assimilation. The years 2008-2012 are chosen due to the relative abundance of oxygen observations from Argo floats during this time. The skill of the state estimate at fitting the data is assessed. The agreement is best for fields that are constrained with the most observations, such as surface pCO2 in Drake Passage (44% of the variance captured) and oxygen profiles (over 60% of the variance captured at 200 and 1000 m). The validity of adjoint method optimization for coupled physical-biogeochemical state estimation is demonstrated with a series of gradient check experiments. The method is shown to be mature and ready to synthesize in situ biogeochemical observations as they become more available. Documenting the B-SOSE configuration and diagnosing the strengths and weaknesses of the solution informs usage of this product as both a climate baseline and as a way to test hypotheses. Transport of Intermediate Waters across 32°S supplies significant amounts of nitrate to the Atlantic Ocean (5.57 ± 2.94 Tmol yr-1) and Indian Ocean (5.09 ± 3.06 Tmol yr-1), but much less nitrate reaches the Pacific Ocean (1.78 ± 1.91 Tmol yr-1). Estimates of air-sea carbon dioxide fluxes south of 50°S suggest a mean uptake of 0.18 Pg C/yr for the time period analyzed.

  7. Saccharides enhance iron bioavailability to Southern Ocean phytoplankton

    NARCIS (Netherlands)

    Hassler, C.S.; Schoemann, V.; Nichols, C.M.; Butler, E.C.V.; Boyd, P.W.; Nichols, C.M.

    2011-01-01

    Iron limits primary productivity in vast regions of the ocean. Given that marine phytoplankton contribute up to 40% of global biological carbon fixation, it is important to understand what parameters control the availability of iron (iron bioavailability) to these organisms. Most studies on iron

  8. High storage rates of anthropogenic CO_{2} in the Indian sector of the Southern Ocean

    Science.gov (United States)

    Murata, Akihiko; Kumamoto, Yu-ichiro; Sasaki, Ken-ichi

    2017-04-01

    Using high-quality data for CO2-system and related properties collected 17 years apart through international observation programs, we examined decadal-scale increases of anthropogenic CO2 along a zonal section at nominal 62˚ S ranging from 30˚ E to 160˚ E in the Indian sector of the Southern Ocean. In contrast to previous studies, increases of anthropogenic CO2 were largest (> 9.0 μmol kg-1) in Antarctic Bottom Water, where little storage of anthropogenic CO2 has been reported. Significant increases of anthropogenic CO2 in bottom and/or deep waters were detected through the section, although they became reduced in magnitude and depth range west of 110˚ E. Vertical distributions of anthropogenic CO2 showed significant positive correlations with decadal-scale changes in CFC-12, a proxy of circulation and ventilation, meaning that the distributions were mainly controlled by physical processes. Comparison of increases of anthropogenic CO2 between calculation methods with and without total alkalinity presented differences of increases of anthropogenic CO2west of 50˚ E. This is probably because decreases in production of particulate inorganic carbons in the Southern Ocean. The highest storage rate of anthropogenic CO2 was estimated to be 1.1 ± 0.6 mol m-2 a-1 at longitudes 130˚ -160˚ E. The results highlight storage rates higher than ever reported in the Southern Ocean, where very low storage of anthropogenic CO2 has been evidenced.

  9. XBT Fall-rate study in the Southern Ocean

    Science.gov (United States)

    Ribeiro, N.; Mata, M. M.; Azevedo, J. L.

    2016-02-01

    Several studies have observed a more prominent warming of the Southern Ocean when compared to other ocean regions of the world in response to global climate change. However, the vast majority of available temperature data for that region is composed by eXpendable BathyTermographers profiles (XBTs). These probes are not equipped with a pressure sensor and thus do not measure depth directly. Depth is inferred by a fall-rate equation offered by the manufacturer that does not seem to adequately represent the extremely cold and high viscosity conditions of the region. Probes fall slower than expected and thus lead to an overestimation in heat content for those areas. In this study, a set of 850 collocated XBT (DB/T7 type) and CTD stations obtained from World Ocean Database (2013) and separated by a maximum distance of 12.5 nm and 10 hours is used. Those pairs are used to identify and quantify the depth errors in the XBT's temperature profiles, proposing a regional equation correction able to represent the peculiarities of the region. Hanawa et al. (1995) and Cheng et al. (2014) correction methods were applied to the dataset, with the latter producing better results. For the pairs in Drake Passage (151), South of Africa (244) and South of Tasmania (455), we found the ideal A coefficients to change by -0.88%, -1.4% and -2.2% from the original values, respectively. When a temperature profile is more homogeneous, there is no significant change if different values of B are used, which was proven to be true since they were .0021 for Drake Passage and .0020 for the other chokings. The ideal fall-rate equation for the Southern Ocean was determined using all pairs, being defined as instead of the proposed by the manufacturer. Overall, the results further support the hypothesis of a regional dependence of the XBT fall-rate on water temperature, and suggest the need of developing a bias correction scheme specific for the polar regions.

  10. The hydrography and dynamics of the ocean environment of the Prince Edward Islands (Southern Ocean)

    Science.gov (United States)

    Ansorge, I. J.; Lutjeharms, J. R. E.

    2002-11-01

    The Prince Edward Islands lie in the Indian sector of the Southern Ocean at 47°S and 38°E. They lie in the path of the Antarctic Circumpolar Current (ACC), between the Subantarctic Front (SAF) to the north and the Antarctic Polar Front (APF) to the south. Two extensive hydrographic surveys (MOES 2 and MIOS 2) have been carried out to establish for the first time the mesoscale hydrography and dynamics of the oceanic surroundings of these islands. During the MOES 2, the SAF was deflected northward around the islands, while the APF lay south of the survey grid and south of the islands. Water masses in the region changed gradually from Subantarctic Surface Water (SASW) to Antarctic Surface Water (AASW) on crossing the Polar Frontal Zone (PFZ). Downstream of the islands, a wake, resulting in the generation of broad meanders, was formed. As a consequence, water masses, in particular warm SASW, were displaced from north of the SAF across the PFZ, while cooler waters, which have been modified in the transitional band of the PFZ, were displaced northwards. In contrast, during MIOS 2, the surface expression of the SAF formed an intensive frontal band. On approaching the islands, the SAF split into two branches, with a branch deflected northwards around the islands, while a second branch meandered southward. In the downstream region, an intense cold eddy consisting of AASW was observed within the PFZ, displacing the SAF northwards. South of this eddy, a warm patch of SASW water was encountered, its position possibly controlled by the meandering SAF. Evidence from both these surveys demonstrates that the ACC exhibits high degrees of mesoscale variability in the vicinity of the Prince Edward Islands. The displacement of the SAF in both instances was apparent, resulting in the advection or the entrapment of neighbouring water masses into and across the PFZ. The speed of the incident current on approaching the islands may play a role in the degree of mesoscale mixing downstream

  11. Extraordinarily high biomass benthic community on Southern Ocean seamounts.

    Science.gov (United States)

    Thresher, R E; Adkins, J; Fallon, S J; Gowlett-Holmes, K; Althaus, F; Williams, A

    2011-01-01

    We describe a previously unknown assemblage of seamount-associated megabenthos that has by far the highest peak biomass reported in the deep-sea outside of vent communities. The assemblage was found at depths of 2-2.5 km on rocky geomorphic features off the southeast coast of Australia, in an area near the Sub-Antarctic Zone characterised by high rates of surface productivity and carbon export to the deep-ocean. These conditions, and the taxa in the assemblage, are widely distributed around the Southern mid-latitudes, suggesting the high-biomass assemblage is also likely to be widespread. The role of this assemblage in regional ecosystem and carbon dynamics and its sensitivities to anthropogenic impacts are unknown. The discovery highlights the lack of information on deep-sea biota worldwide and the potential for unanticipated impacts of deep-sea exploitation.

  12. Iron defecation by sperm whales stimulates carbon export in the Southern Ocean.

    Science.gov (United States)

    Lavery, Trish J; Roudnew, Ben; Gill, Peter; Seymour, Justin; Seuront, Laurent; Johnson, Genevieve; Mitchell, James G; Smetacek, Victor

    2010-11-22

    The iron-limited Southern Ocean plays an important role in regulating atmospheric CO(2) levels. Marine mammal respiration has been proposed to decrease the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere. Here, we show that by consuming prey at depth and defecating iron-rich liquid faeces into the photic zone, sperm whales (Physeter macrocephalus) instead stimulate new primary production and carbon export to the deep ocean. We estimate that Southern Ocean sperm whales defecate 50 tonnes of iron into the photic zone each year. Molar ratios of C(export):Fe(added) determined during natural ocean fertilization events are used to estimate the amount of carbon exported to the deep ocean in response to the iron defecated by sperm whales. We find that Southern Ocean sperm whales stimulate the export of 4 × 10(5) tonnes of carbon per year to the deep ocean and respire only 2 × 10(5) tonnes of carbon per year. By enhancing new primary production, the populations of 12 000 sperm whales in the Southern Ocean act as a carbon sink, removing 2 × 10(5) tonnes more carbon from the atmosphere than they add during respiration. The ability of the Southern Ocean to act as a carbon sink may have been diminished by large-scale removal of sperm whales during industrial whaling.

  13. Iron defecation by sperm whales stimulates carbon export in the Southern Ocean

    Science.gov (United States)

    Lavery, Trish J.; Roudnew, Ben; Gill, Peter; Seymour, Justin; Seuront, Laurent; Johnson, Genevieve; Mitchell, James G.; Smetacek, Victor

    2010-01-01

    The iron-limited Southern Ocean plays an important role in regulating atmospheric CO2 levels. Marine mammal respiration has been proposed to decrease the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere. Here, we show that by consuming prey at depth and defecating iron-rich liquid faeces into the photic zone, sperm whales (Physeter macrocephalus) instead stimulate new primary production and carbon export to the deep ocean. We estimate that Southern Ocean sperm whales defecate 50 tonnes of iron into the photic zone each year. Molar ratios of Cexport ∶Feadded determined during natural ocean fertilization events are used to estimate the amount of carbon exported to the deep ocean in response to the iron defecated by sperm whales. We find that Southern Ocean sperm whales stimulate the export of 4 × 105 tonnes of carbon per year to the deep ocean and respire only 2 × 105 tonnes of carbon per year. By enhancing new primary production, the populations of 12 000 sperm whales in the Southern Ocean act as a carbon sink, removing 2 × 105 tonnes more carbon from the atmosphere than they add during respiration. The ability of the Southern Ocean to act as a carbon sink may have been diminished by large-scale removal of sperm whales during industrial whaling. PMID:20554546

  14. How deep is deep enough? Ocean iron fertilization and carbon sequestration in the Southern Ocean

    Science.gov (United States)

    Robinson, J.; Popova, E. E.; Yool, A.; Srokosz, M.; Lampitt, R. S.; Blundell, J. R.

    2014-04-01

    Artificial ocean iron fertilization (OIF) enhances phytoplankton productivity and is being explored as a means of sequestering anthropogenic carbon within the deep ocean. To be considered successful, carbon should be exported from the surface ocean and isolated from the atmosphere for an extended period (e.g., the Intergovernmental Panel on Climate Change's standard 100 year time horizon). This study assesses the impact of deep circulation on carbon sequestered by OIF in the Southern Ocean, a high-nutrient low-chlorophyll region known to be iron stressed. A Lagrangian particle-tracking approach is employed to analyze water mass trajectories over a 100 year simulation. By the end of the experiment, for a sequestration depth of 1000 m, 66% of the carbon had been reexposed to the atmosphere, taking an average of 37.8 years. Upwelling occurs predominately within the Antarctic Circumpolar Current due to Ekman suction and topography. These results emphasize that successful OIF is dependent on the physical circulation, as well as the biogeochemistry.

  15. The effects of iron fertilization on carbon sequestration in the Southern Ocean.

    Science.gov (United States)

    Buesseler, Ken O; Andrews, John E; Pike, Steven M; Charette, Matthew A

    2004-04-16

    An unresolved issue in ocean and climate sciences is whether changes to the surface ocean input of the micronutrient iron can alter the flux of carbon to the deep ocean. During the Southern Ocean Iron Experiment, we measured an increase in the flux of particulate carbon from the surface mixed layer, as well as changes in particle cycling below the iron-fertilized patch. The flux of carbon was similar in magnitude to that of natural blooms in the Southern Ocean and thus small relative to global carbon budgets and proposed geoengineering plans to sequester atmospheric carbon dioxide in the deep sea.

  16. A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization.

    Science.gov (United States)

    Boyd, P W; Watson, A J; Law, C S; Abraham, E R; Trull, T; Murdoch, R; Bakker, D C; Bowie, A R; Buesseler, K O; Chang, H; Charette, M; Croot, P; Downing, K; Frew, R; Gall, M; Hadfield, M; Hall, J; Harvey, M; Jameson, G; LaRoche, J; Liddicoat, M; Ling, R; Maldonado, M T; McKay, R M; Nodder, S; Pickmere, S; Pridmore, R; Rintoul, S; Safi, K; Sutton, P; Strzepek, R; Tanneberger, K; Turner, S; Waite, A; Zeldis, J

    2000-10-12

    Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis'. For this reason, it is important to understand the response of pelagic biota to increased iron supply. Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest. Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days. This drawdown was mostly due to the proliferation of diatom stocks. But downward export of biogenic carbon was not increased. Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters. Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction.

  17. Southern Ocean fronts from the Greenwich meridian to Tasmania

    Science.gov (United States)

    Belkin, Igor M.; Gordon, Arnold L.

    1996-02-01

    distinguished in the Indian Ocean between 31° and 38°S. The front marks the southern boundary of the subtropical salty, warm water pool of the central South Indian Ocean. The NSTF location is coincident with the position of the wind convergence between westerlies and easterlies, suggesting the possible wind-driven frontogenesis.

  18. Increased dust deposition in the Pacific Southern Ocean during glacial periods

    Science.gov (United States)

    Lamy, Frank; Gersonde, Rainer; Winckler, Gisela; Esper, Oliver; Jaeschke, Andrea; Kuhn, Gerhard; Ullermann, Johannes; Martinez-Garcia, Alfredo; Lambert, Fabrice; Kilian, Rolf

    2014-05-01

    Dust deposition across the Southern Ocean plays a critical role for marine biological production through iron fertilization and is supposed to control a significant fraction of glacial-interglacial atmospheric CO2 changes. However, in the Pacific, the largest Southern Ocean sector, reliable sediment records are sparse and climate models mostly indicate low dust deposition both for modern times and the last glacial maximum. Here, we present comprehensive data-sets of dust supply based on the analysis of sediment records recently retrieved across the Pacific Southern Ocean. The shape and glacial/interglacial pattern of lithogenic sediment input records in the western and central sector reveals strong similarities to dust records from Antarctica and the South Atlantic. Though our new data document substantial sediment redistribution, glacial dust mass accumulation rates corrected for sediment focusing exceed interglacial values by a factor of ~3. The first-order changes in Subantarctic biological productivity largely follow increased dust supply during glacials. Taken together our new sediment records document a substantial glacial dust supply from Australian and New Zealand sources to the Pacific SO sector eastward to at least 125°W. Such enhancement of dust supply is consistent with stronger aridity in Australia and a glacial dust source in New Zealand. Although the most likely dust source for the South Pacific is Australia/New Zealand, the glacial/interglacial pattern and timing of lithogenic sediment deposition is similar to dust records from Antarctica and the South Atlantic dominated by Patagonian sources. These similarities imply large-scale common climate forcings such as latitudinal shifts of the southern westerlies and regionally enhanced glaciogenic dust mobilization in New Zealand and Patagonia.

  19. Exploring the link between micro-nutrients and phytoplankton in the Southern Ocean during the 2007 austral summer

    Directory of Open Access Journals (Sweden)

    Christel eHassler

    2012-07-01

    Full Text Available Bottle assays and large-scale fertilisation experiments have demonstrated that, in the Southern Ocean, iron often controls the biomass and the biodiversity of primary producers. To grow, phytoplankton need numerous other trace metals (micronutrients required for the activity of key enzymes and other intracellular functions. However, little is known of the potential these other trace elements have to limit the growth of phytoplankton in the Southern Ocean. This study investigates the link between the distribution of several micronutrients (Zn, Co, Cu, Cd, Ni and phytoplankton from samples collected during the SAZ-Sense oceanographic expedition (RV Aurora Australis, Jan.–Feb. 2007. Larger phytoplankton are usually associated with lower diffusive supply and higher micronutrient requirement; for this reason, the delineation between phytoplankton larger than 10 µm and those with a size ranging from 0.8–10 µm was made. In addition, different species of phytoplankton may have different requirements to sustain their growth; the phytoplankton biodiversity here was inferred using biomarker pigments. This study, therefore, attempts to elucidate whether micronutrients other than iron need to be considered as parameters for controlling the phytoplankton growth in the Australian sector of the Southern Ocean. Understanding of the parameters controlling phytoplankton is paramount, as it affects the functioning of the Southern Ocean, its marine resources and ultimately the global carbon cycle.

  20. Assessing the internal consistency of the CARINA data base in the Pacific sector of the Southern Ocean

    Directory of Open Access Journals (Sweden)

    C. L. Sabine

    2010-07-01

    Full Text Available The CARINA project is aimed at gathering and providing secondary quality control checks on carbon and carbon-relevant hydrographic and geochemical data from cruises all across the Atlantic, Arctic and Southern Ocean. In total the project gathered 188 cruises that were not previously available to the public. Of these 188 cruises, 37 are part of the Southern Ocean. Parameters from the Southern Ocean cruises, including total carbon dioxide (TCO2, total alkalinity, oxygen, nitrate, phosphate and silicate, were examined for cruise-to-cruise consistency. pH and chlorofluorocarbons (CFCs are also part of the data base, but are not discussed here. This paper focuses on the quality control of the Southern Ocean data from the Pacific sector which consisted of 29 cruises of which 17 were included in a previous synthesis called GLODAP, 11 were new cruises from the CARINA dataset, and one cruise was included in GLODAP but was updated with new data and therefore also included in CARINA. The Pacific sector quality control procedures included crossover analysis between stations and inversion analysis of all crossover data. The GLODAP data were included into the analysis as reference cruises but without applying the GLODAP recommended adjustments so the corrections could be independently verified. The outcome of this effort is an internally consistent, high-quality carbon data set for all cruises, including the reference cruises.

  1. New Hampshire / Southern Maine Ocean Uses Atlas: Fishing sector

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

  2. New Hampshire / Southern Maine Ocean Uses Atlas: Industrial sector

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

  3. New Hampshire / Southern Maine Ocean Uses Atlas: Dominant and Aggregates

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

  4. New Hampshire and Southern Maine Ocean Uses Atlas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

  5. Antarctic climate, Southern Ocean circulation patterns, and deep water formation during the Eocene

    Science.gov (United States)

    Huck, Claire E.; van de Flierdt, Tina; Bohaty, Steven M.; Hammond, Samantha J.

    2017-07-01

    We assess early-to-middle Eocene seawater neodymium (Nd) isotope records from seven Southern Ocean deep-sea drill sites to evaluate the role of Southern Ocean circulation in long-term Cenozoic climate change. Our study sites are strategically located on either side of the Tasman Gateway and are positioned at a range of shallow (Climatic Optimum and is associated with documented cooling across the study region and increased export of Antarctic deep waters, highlighting the complexity and importance of Southern Ocean circulation in the greenhouse climate of the Eocene.

  6. Changes in micronutrient supply to the surface Southern Ocean (Atlantic sector) across the glacial termination

    Science.gov (United States)

    Hendry, Katharine R.; Rickaby, Rosalind E. M.; Allen, Claire S.

    2011-09-01

    Major deepwater masses upwell and reach the surface in the Southern Ocean, forming an important conduit supplying nutrients and micronutrients to the surface and playing a key role in the regulation of global climate through ocean-atmosphere gas exchange. Here, we reconstruct changes in micronutrient distribution in this region in response to past changes in upwelling, oceanic mixing, and sea-ice seasonality. We present two downcore (Zn/Si)opal records from the Scotia Sea and Drake Passage region, which we interpret in the context of micronutrient distribution in the Atlantic sector of the Southern Ocean over the last glacial termination. Previous work shows that micronutrient availability in the surface waters in the South Atlantic appear to be controlled dominantly by upwelling and mixing of micronutrient rich deepwaters, which are additionally fuelled by the terrestrial sediment sources of the Scotia Arc and South Georgia. This is supported by our reconstructions, which show micronutrient availability to the west of the Scotia Arc and South Georgia are consistently lower than to the east over the last glacial termination due to downstream transport and mixing into surface waters of continentally derived material in the Antarctic Circumpolar Current. Micronutrient availability in this region was at a minimum from 20 to 25 ky BP, coinciding with maximum sea-ice coverage, and increased due to an expansion of the seasonal sea-ice zone and increased mixing of subsurface waters. Our findings are consistent with largely diminished upwelling of micronutrients during the maximum glacial extent, and reduced mixing due to the presence of persistent sea-ice. During the deglacial there was an increase in micronutrient availability, as well as other nutrients and inorganic carbon, within the Antarctic Circumpolar Current as a result of an increase in deep oceanic upwelling, mixing and strengthened zonal transport.

  7. Temperature and upwelling / downwelling irradiance data from drifting buoy in the Southern Oceans as part of the Joint Global Ocean Flux Study/Southern Ocean (JGOFS/Southern Ocean) project, from 1994-12-25 to 1998-06-28 (NODC Accession 9900183)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature and upwelling / downwelling irradiance data were collected using drifting buoy in the Southern Oceans from December 25, 1994 to June 28, 1998. Data were...

  8. The interdisciplinary marine system of the Amundsen Sea, Southern Ocean: Recent advances and the need for sustained observations

    Science.gov (United States)

    Meredith, Michael P.; Ducklow, Hugh W.; Schofield, Oscar; Wåhlin, Anna; Newman, Louise; Lee, SangHoon

    2016-01-01

    The Southern Ocean exerts a profound influence on the functioning of the Earth System, in part because its location and unique bathymetric configuration enable direct linkages to the other major ocean basins (Ganachaud and Wunsch, 2000; Lumpkin and Speer, 2007). It is the site of the world's largest current system, the Antarctic Circumpolar Current (ACC), which transfers waters and climatically/ecologically-important tracers between the Atlantic, Indian and Pacific Oceans (Rintoul et al., 2001). In addition to the strong horizontal connectivity, the ACC is also characterized by a vigorous overturning circulation, which upwells warm, nutrient-rich waters from intermediate depth to the surface, where they are modified by interactions with the atmosphere and cryosphere to form new water masses, some of which are lighter and others more dense (Marshall and Speer, 2012). This overturning circulation structures the Southern Ocean both horizontally and vertically, dictates the levels of its communication with the rest of the global ocean, and is a fundamental control on the sequestration of carbon from the atmosphere into the ocean interior (Sallée et al., 2012). In some locations, the upwelled waters can intrude onto the Antarctic shelves, supplying heat and nutrients to the shallower regions. This is believed to be especially effective in west Antarctica, where the southern edge of the ACC moves close to the shelf break (Martinson, 2011; Orsi et al., 1995; Thoma et al., 2008).

  9. Uncertainty in projections of Southern Ocean carbon uptake and acidification

    Science.gov (United States)

    Lovenduski, Nicole; Hauri, Claudine

    2017-04-01

    We investigate projections of carbon uptake and the associated acidification of the Southern Ocean over 2006-2080 using output from two ensembles of the Community Earth System Model run under business as usual (RCP8.5) and mitigation (RCP4.5) emission scenarios. On basin-wide and regional scales we observe a rapid onset of aragonite undersaturation in surface waters by mid-century that may be detrimental to calcareous organisms. An analysis of variance reveals that the speed of transition from supersaturation to undersaturation is driven almost entirely by emission scenario, as internal variability in saturation depth across ensemble members is small. Regional differences are observed in the timing and magnitude of aragonite saturation state changes. In the Patagonian Shelf region, undersaturation of the top 200m of the water column is observed by 2080 regardless of emission scenario. Whereas, in the Weddell Sea, saturation state is significantly different between the two emission scenarios by 2080, and undersaturation of the surface waters is "avoidable" if we follow RCP4.5, rather than RCP8.5.

  10. Source of the Magnetic Susceptibility Variations in Southern Ocean Sediments Over the Last Glacial Cycle

    Science.gov (United States)

    Maher, B.; Thompson, R.

    2014-12-01

    Changes in the sources, mineralogy and rates of iron supply to the Southern Ocean may have global impact and significance, by influencing plankton growth rates and nutrient take-up in this, the largest of the high nutrient low chlorophyll (HNLC) regions of the world ocean. Iron 'fertilization' in the Southern Ocean may increase rates of carbon export production and thus the ocean uptake flux of atmospheric CO2, and also diminish the northward flow of residual nutrients to the extra-polar ocean, especially the HNLC regions of the Pacific. Changes in Southern Ocean export production may contribute to global climate change over glacial-interglacial timescales. The key sources of iron for the Southern Ocean are reported to be windblown dust and sedimentary supply; their relative significance an issue of much long-standing debate. Links between aeolian dust fluxes to the Southern Ocean and to the Antarctic ice cores have been proposed for the Scotia Sea region of the Southern Ocean, downwind from the South American land mass. Regional downcore variations in the magnetic susceptibility of sediments from the Scotia Sea show remarkable similarity to variations in dust concentration and flux in East Antarctic ice cores (with glacial stages characterised by increases in ice dust and sediment magnetic susceptibility). Indeed, the strength of the ice dust/sediment magnetism correlations (r ~ 0.7) provides a pragmatic basis for use of the sedimentary magnetic susceptibility records as a chronostratigraphic proxy, a boon in the carbonate-free deep-sea sediments of the Southern Ocean. However, the source and causal basis of the sediment magnetism/ice dust co-variations remain controversial; aeolian dust, bacterial magnetite and wind-driven current transport of marine sediment have all been invoked as possible key sources. Here, we use magnetic and isotopic methods to resolve this debate, and identify and quantify the sources of magnetic material to the Scotia Sea for the last

  11. Bioavailability of organically bound Fe to model phytoplankton of the Southern Ocean

    Directory of Open Access Journals (Sweden)

    C. S. Hassler

    2009-10-01

    Full Text Available Iron (Fe is known to be mostly bound to organic ligands and to limit primary productivity in the Southern Ocean. It is thus important to investigate the bioavailability of organically bound Fe. In this study, we used four phytoplankton species of the Southern Ocean (Phaeocystis sp., Chaetoceros sp., Fragilariopsis kerguelensis and Thalassiosira antarctica Comber to measure the influence of various organic ligands on Fe solubility and bioavailability. Short-term uptake Fe:C ratios were inversely related to the surface area to volume ratios of the phytoplankton. The ratio of extracellular to intracellular Fe is used to discuss the relative importance of diffusive supply and uptake to control Fe bioavailability. The effect of excess organic ligands on Fe bioavailability cannot be solely explained by their effect on Fe solubility. For most strains studied, the bioavailability of Fe can be enhanced relative to inorganic Fe in the presence of porphyrin, catecholate siderophore and saccharides whereas it was decreased in presence of hydroxamate siderophore and organic amine. For Thalassiosira, iron bioavailability was not affected by the presence of porphyrin, catecholate siderophore and saccharides. The enhancement of Fe bioavailability in presence of saccharides is presented as the result from both the formation of bioavailable (or chemically labile organic form of Fe and the stabilisation of Fe within the dissolved phase. Given the ubiquitous presence of saccharides in the ocean, these compounds might represent an important factor to control the basal level of soluble and bioavailable Fe. Results show that the use of model phytoplankton is promising to improve mechanistic understanding of Fe bioavailability and primary productivity in HNLC regions of the ocean.

  12. Southern Ocean origin for the resumption of Atlantic thermohaline circulation during deglaciation.

    Science.gov (United States)

    Knorr, Gregor; Lohmann, Gerrit

    2003-07-31

    During the two most recent deglaciations, the Southern Hemisphere warmed before Greenland. At the same time, the northern Atlantic Ocean was exposed to meltwater discharge, which is generally assumed to reduce the formation of North Atlantic Deep Water. Yet during deglaciation, the Atlantic thermohaline circulation became more vigorous, in the transition from a weak glacial to a strong interglacial mode. Here we use a three-dimensional ocean circulation model to investigate the impact of Southern Ocean warming and the associated sea-ice retreat on the Atlantic thermohaline circulation. We find that a gradual warming in the Southern Ocean during deglaciation induces an abrupt resumption of the interglacial mode of the thermohaline circulation, triggered by increased mass transport into the Atlantic Ocean via the warm (Indian Ocean) and cold (Pacific Ocean) water route. This effect prevails over the influence of meltwater discharge, which would oppose a strengthening of the thermohaline circulation. A Southern Ocean trigger for the transition into an interglacial mode of circulation provides a consistent picture of Southern and Northern hemispheric climate change at times of deglaciation, in agreement with the available proxy records.

  13. Phytoplankton chemotaxonomy in the Atlantic sector of the Southern Ocean during late summer 2009

    CSIR Research Space (South Africa)

    Gibberd, M-J

    2013-08-01

    Full Text Available A chemotaxonomic investigation of surface phytoplankton was undertaken on a research cruise to the Atlantic sector of the Southern Ocean during late austral summer 2009. Based on pigment signatures, several distinct regions emerged that were...

  14. Surface water iron supplies in the Southern Ocean sustained by deep winter mixing

    CSIR Research Space (South Africa)

    Tagliabue, A

    2014-04-01

    Full Text Available Low levels of iron limit primary productivity across much of the Southern Ocean. At the basin scale, most dissolved iron is supplied to surfacewaters from subsurface reservoirs, because land inputs are spatially limited. Deep mixing in winter...

  15. Ecological biogeography of southern ocean islands: species-area relationships, human impacts, and conservation

    NARCIS (Netherlands)

    Chown, S.L.; Gremmen, N.J.M.; Gaston, K.J.

    1998-01-01

    Previous studies have concluded that southern ocean islands are anomalous because past glacial extent and current temperature apparently explain most variance in their species richness. Here, the relationships between physical variables and species richness of vascular plants, insects, land and

  16. Secondary calcification of planktic foraminifera from the Indian sector of Southern ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Mohan, R.; Shetye, S.; Tiwari, M.; AnilKumar, N.

    This study focused on planktic foraminifera in plankton tows and surface sediments from the western Indian sector of Southern Ocean in order to evaluate the potential foraminiferal secondary calcification and/or dissolution in the sediment...

  17. Southern Ocean Climate and Sea Ice Anomalies Associated with the Southern Oscillation

    Science.gov (United States)

    Kwok, R.; Comiso, J. C.

    2001-01-01

    The anomalies in the climate and sea ice cover of the Southern Ocean and their relationships with the Southern Oscillation (SO) are investigated using a 17-year of data set from 1982 through 1998. We correlate the polar climate anomalies with the Southern Oscillation index (SOI) and examine the composites of these anomalies under the positive (SOI > 0), neutral (0 > SOI > -1), and negative (SOI oscillating climate anomalies that are closely linked to the SO. Within these sectors, positive (negative) phases of the SOI are generally associated with lower (higher) sea-level pressure, cooler (warmer) surface air temperature, and cooler (warmer) sea surface temperature in these sectors. Associations between these climate anomalies and the behavior of the Antarctic sea ice cover are clearly evident. Recent anomalies in the sea ice cover that are apparently associated with the SOI include: the record decrease in the sea ice extent in the Bellingshausen Sea from mid- 1988 through early 199 1; the relationship between Ross Sea SST and ENSO signal, and reduced sea ice concentration in the Ross Sea; and, the shortening of the ice season in the eastern Ross Sea, Amundsen Sea, far western Weddell Sea, and the lengthening of the ice season in the western Ross Sea, Bellingshausen Sea and central Weddell Sea gyre over the period 1988-1994. Four ENSO episodes over the last 17 years contributed to a negative mean in the SOI (-0.5). In each of these episodes, significant retreats in the Bellingshausen/Amundsen Sea were observed providing direct confirmation of the impact of SO on the Antarctic sea ice cover.

  18. Effects of climate change and fisheries bycatch on Southern Ocean seabirds: a review

    OpenAIRE

    Rolland, Virginie; Jenouvrier, S.; Nevoux, Marie; Delord, Karine; Weimerskirch, Henri

    2012-01-01

    Over the last century, major climate changes and intense human exploitation of natural living resources have occurred in the Southern Ocean, potentially affecting its ecosystems up to top marine predators. Fisheries may also directly affect seabirds through bycatch and additional food resources provided by discards. The past 20 yr of research has seen an increasing number of studies investigating the effects of climate change and fisheries activities on Southern Ocean seabirds. Here, we revie...

  19. Iron limitation modulates ocean acidification effects on southern ocean phytoplankton communities.

    Science.gov (United States)

    Hoppe, Clara J M; Hassler, Christel S; Payne, Christopher D; Tortell, Philippe D; Rost, Björn; Trimborn, Scarlett

    2013-01-01

    The potential interactive effects of iron (Fe) limitation and Ocean Acidification in the Southern Ocean (SO) are largely unknown. Here we present results of a long-term incubation experiment investigating the combined effects of CO2 and Fe availability on natural phytoplankton assemblages from the Weddell Sea, Antarctica. Active Chl a fluorescence measurements revealed that we successfully cultured phytoplankton under both Fe-depleted and Fe-enriched conditions. Fe treatments had significant effects on photosynthetic efficiency (Fv/Fm; 0.3 for Fe-depleted and 0.5 for Fe-enriched conditions), non-photochemical quenching (NPQ), and relative electron transport rates (rETR). pCO2 treatments significantly affected NPQ and rETR, but had no effect on Fv/Fm. Under Fe limitation, increased pCO2 had no influence on C fixation whereas under Fe enrichment, primary production increased with increasing pCO2 levels. These CO2-dependent changes in productivity under Fe-enriched conditions were accompanied by a pronounced taxonomic shift from weakly to heavily silicified diatoms (i.e. from Pseudo-nitzschia sp. to Fragilariopsis sp.). Under Fe-depleted conditions, this functional shift was absent and thinly silicified species dominated all pCO2 treatments (Pseudo-nitzschia sp. and Synedropsis sp. for low and high pCO2, respectively). Our results suggest that Ocean Acidification could increase primary productivity and the abundance of heavily silicified, fast sinking diatoms in Fe-enriched areas, both potentially leading to a stimulation of the biological pump. Over much of the SO, however, Fe limitation could restrict this possible CO2 fertilization effect.

  20. Iron Limitation Modulates Ocean Acidification Effects on Southern Ocean Phytoplankton Communities

    Science.gov (United States)

    Hoppe, Clara J. M.; Hassler, Christel S.; Payne, Christopher D.; Tortell, Philippe D.; Rost, Björn; Trimborn, Scarlett

    2013-01-01

    The potential interactive effects of iron (Fe) limitation and Ocean Acidification in the Southern Ocean (SO) are largely unknown. Here we present results of a long-term incubation experiment investigating the combined effects of CO2 and Fe availability on natural phytoplankton assemblages from the Weddell Sea, Antarctica. Active Chl a fluorescence measurements revealed that we successfully cultured phytoplankton under both Fe-depleted and Fe-enriched conditions. Fe treatments had significant effects on photosynthetic efficiency (Fv/Fm; 0.3 for Fe-depleted and 0.5 for Fe-enriched conditions), non-photochemical quenching (NPQ), and relative electron transport rates (rETR). pCO2 treatments significantly affected NPQ and rETR, but had no effect on Fv/Fm. Under Fe limitation, increased pCO2 had no influence on C fixation whereas under Fe enrichment, primary production increased with increasing pCO2 levels. These CO2-dependent changes in productivity under Fe-enriched conditions were accompanied by a pronounced taxonomic shift from weakly to heavily silicified diatoms (i.e. from Pseudo-nitzschia sp. to Fragilariopsis sp.). Under Fe-depleted conditions, this functional shift was absent and thinly silicified species dominated all pCO2 treatments (Pseudo-nitzschia sp. and Synedropsis sp. for low and high pCO2, respectively). Our results suggest that Ocean Acidification could increase primary productivity and the abundance of heavily silicified, fast sinking diatoms in Fe-enriched areas, both potentially leading to a stimulation of the biological pump. Over much of the SO, however, Fe limitation could restrict this possible CO2 fertilization effect. PMID:24278207

  1. Fish from the Southern Ocean: biodiversity, ecology and conservation challenges

    Directory of Open Access Journals (Sweden)

    Marino Vacchi

    2015-11-01

    Living and functioning at subzero temperatures implied important adaptations, including freezing avoidance by antifreeze glycoproteins ( AFGPs. Among the system-wide adaptive traits holding major ecological implications, the acquisition of secondary pelagicism in some species (plesiomorphically devoid of swim-bladder is a major. In those notothenioids, lipid deposition and reduced ossification allowed to achieve partial or full neutral buoyancy, and enabled expansion into semi-pelagic, pelagic, and cryopelagic habitats. Such an impressive ecological expansion has allowed several notothenioids to play a primary role in the Antarctic marine ecosystems. On the other side, their fine adaptation to the environment, might expose these fishes to risks that need to be properly considered and addressed. For instance, a relationship between the Antarctic silverfish (Pleuragramma antarctica, a key species in the coastal Antarctic ecosystem and the sea-ice, has recently been assessed, thus making this species potentially threatened by the ongoing climatic change, with implications for the whole ecosystem. In addition, some Antarctic fish, such as toothfishes (Dissostichus eleginoides and Dissostichus mawsoni are primary targets of industrial fish harvesting in the SO. To increase and update the scientific knowledge on these species is mandatory in order to improve the management of Antarctic marine resources, in response to the increasing international request of exploitation. This task is presently being conducted by CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources, along with fighting the illegal, unreported and unregulated (IUU fishing and with the establishment of MPAs (Marine Protected Areas in various sectors of the Southern Ocean.

  2. Impacts of Atmosphere-Ocean Coupling on Southern Hemisphere Climate Change

    Science.gov (United States)

    Li, Feng; Newman, Paul; Pawson, Steven

    2013-01-01

    Climate in the Southern Hemisphere (SH) has undergone significant changes in recent decades. These changes are closely linked to the shift of the Southern Annular Mode (SAM) towards its positive polarity, which is driven primarily by Antarctic ozone depletion. There is growing evidence that Antarctic ozone depletion has significant impacts on Southern Ocean circulation change. However, it is poorly understood whether and how ocean feedback might impact the SAM and climate change in the SH atmosphere. This outstanding science question is investigated using the Goddard Earth Observing System Coupled Atmosphere-Ocean-Chemistry Climate Model(GEOS-AOCCM).We perform ensemble simulations of the recent past (1960-2010) with and without the interactive ocean. For simulations without the interactive ocean, we use sea surface temperatures and sea ice concentrations produced by the interactive ocean simulations. The differences between these two ensemble simulations quantify the effects of atmosphere-ocean coupling. We will investigate the impacts of atmosphere-ocean coupling on stratospheric processes such as Antarctic ozone depletion and Antarctic polar vortex breakup. We will address whether ocean feedback affects Rossby wave generation in the troposphere and wave propagation into the stratosphere. Another focuson this study is to assess how ocean feedback might affect the tropospheric SAM response to Antarctic ozone depletion

  3. Preliminary climatology and improved modelling of south Indian Ocean and Southern Ocean mid-latitude cyclones

    Science.gov (United States)

    Buckley, Bruce W.; Leslie, Lance M.

    2004-08-01

    The intense mid-latitude cyclones that traverse the southern waters of the Indian Ocean, between South Africa and southwestern Western Australia, are among the strongest depressions found anywhere in the world, outside tropical waters. Near-surface winds that exceed storm force (i.e. 24 m/s or 48 knots), and central pressures of 960 hPa and lower, are relatively common for these systems. They pose a constant threat to both open ocean and coastal shipping, and regularly generate severe weather over the populated southwestern corner of Australia. Large ocean waves and swell produce extensive coastal inundation and erosion.There were two main aims in this study. The first aim was to develop a preliminary climatology of these intense mid-latitude cyclones, for the region 20-60 °S, 30-130 °E. The climatology, which is the first that we are aware of for this notoriously data-sparse region, is based largely upon satellite observations, particularly scatterometer data, and is supplemented by ship, buoy and all available land observations. The climatology revealed that, historically, the frequency and intensity of the mid-latitude cyclones in this domain have been significantly underestimated. This underestimation has resulted in analyses that have serious flaws, and the resultant operational forecasts provided to the duty forecasters in the regional forecast centre located in Perth, Western Australia, are of highly variable quality. A number of other climatological features of these storms are discussed in this article.The second aim was to identify the factors that can contribute to a significant improvement in model forecasts of these storms. So far, there have been very few studies of explosively developing cyclones over this part of the world. Results are presented here from a series of high-resolution numerical simulations of an intense cool season Southern Ocean cyclone that developed in 2003, using the HIRES numerical weather prediction model developed by L

  4. Hydrographic and productivity characteristics along 45 degrees E longitude in the southwestern Indian Ocean and Southern Ocean during austral summer 2004

    Digital Repository Service at National Institute of Oceanography (India)

    Jasmine, P.; Muraleedharan, K.R.; Madhu, N.V.; AshaDevi, C.R.; Alagarsamy, R.; Achuthankutty, C.T.; Jayan, Z.; Sanjeevan, V.N.; Sahayak, S.

    During the austral summer 2004, an intensive multidisciplinary survey was carried out in the Indian Ocean sector of the Southern Ocean to study the main hydrographic features and the associated productivity processes. This sector includes...

  5. Transport and scavenging of Pu in surface waters of the Southern Hemisphere Oceans

    DEFF Research Database (Denmark)

    Gastaud, J.; Povinec, P.P.; Aoyama, M.

    2011-01-01

    The distribution of 239Pu in Atlantic and Indian Ocean waters about four decades after their main injection from atmospheric nuclear weapons tests is discussed. Recent data obtained in the framework of the SHOTS (Southern Hemisphere Ocean Tracer Studies) projects are evaluated and compared...

  6. Interactions of dissolved CO2 with cadmium isotopes in the Southern Ocean

    NARCIS (Netherlands)

    de Baar, Henricus; van Heuven, Steven; Abouchami, Wafa; Xue, Zichen; Galer, Stephen J. G.; Rehkamper, Mark; Middag, Rob; van Ooijen, J.

    Here we report the first ever observations of a strong correlation in ocean surface waters of the dissolved δ114Cd with dissolved CO2. This is observed in the Southern Ocean along the 0°W meridian in both the Antarctic Circumpolar Current and the Weddell Gyre, as well as in the Weddell Sea proper,

  7. The influence of UV irradiation on the photoreduction of iron in the Southern Ocean

    NARCIS (Netherlands)

    Rijkenberg, M J A; Fischer, AC; Kroon, JJ; Gerringa, LJA; Timmermans, KR; Wolterbeek, HT; de Baar, H J W

    2005-01-01

    An iron enrichment experiment, EisenEx, was performed in the Atlantic sector of the Southern Ocean during the Antarctic spring of 2000. Deck incubations of open ocean water were performed to investigate the influence of ultraviolet B (UVB: 280-315 nm) and ultraviolet A (UVA: 315-400 nm) on the

  8. Response of bacterioplankton to iron fertilization of the Southern Ocean, Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, S.K.; Kotakonda, A.; Kapardar, R.K.; Kankipati, H.K.; Rao, P.S.; Sankaranarayanan, P.M.; Vetaikorumagan, S.R.; Gundlapally, S.R.; Ramaiah, N.; Shivaji, S.

    Ocean iron fertilization is an approach to increase CO2 sequestration. The Indo-German iron fertilization experiment “LOHAFEX” was carried out in the Southern Ocean surrounding Antarctica in 2009 to monitor changes in bacterial community...

  9. Bacterial community dynamics during polysaccharide degradation at contrasting sites in the Southern and Atlantic Oceans.

    Science.gov (United States)

    Wietz, Matthias; Wemheuer, Bernd; Simon, Heike; Giebel, Helge-Ansgar; Seibt, Maren A; Daniel, Rolf; Brinkhoff, Thorsten; Simon, Meinhard

    2015-10-01

    The bacterial degradation of polysaccharides is central to marine carbon cycling, but little is known about the bacterial taxa that degrade specific marine polysaccharides. Here, bacterial growth and community dynamics were studied during the degradation of the polysaccharides chitin, alginate and agarose in microcosm experiments at four contrasting locations in the Southern and Atlantic Oceans. At the Southern polar front, chitin-supplemented microcosms were characterized by higher fractions of actively growing cells and a community shift from Alphaproteobacteria to Gammaproteobacteria and Bacteroidetes. At the Antarctic ice shelf, chitin degradation was associated with growth of Bacteroidetes, with 24% higher cell numbers compared with the control. At the Patagonian continental shelf, alginate and agarose degradation covaried with growth of different Alteromonadaceae populations, each with specific temporal growth patterns. At the Mauritanian upwelling, only the alginate hydrolysis product guluronate was consumed, coincident with increasing abundances of Alteromonadaceae and possibly cross-feeding SAR11. 16S rRNA gene amplicon libraries indicated that growth of the Bacteroidetes-affiliated genus Reichenbachiella was stimulated by chitin at all cold and temperate water stations, suggesting comparable ecological roles over wide geographical scales. Overall, the predominance of location-specific patterns showed that bacterial communities from contrasting oceanic biomes have members with different potentials to hydrolyse polysaccharides. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  10. Zooplankton Atlas of the Southern Ocean: The SCAR SO-CPR Survey (1991-2008)

    Science.gov (United States)

    McLeod, David J.; Hosie, Graham W.; Kitchener, John A.; Takahashi, Kunio T.; Hunt, Brian P. V.

    2010-08-01

    The SCAR Southern Ocean Continuous Plankton Recorder (SO-CPR) Survey produces one of the largest and most accessed zooplankton data sets in the world. These data serve as a reference for other Southern Ocean monitoring programmes such as those run by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and the developing Southern Ocean Observing System (SOOS). It has been instrumental in providing baseline data on zooplankton composition, communities, and distribution patterns on the ocean basin scale. The SO-CPR Survey is publishing the first detailed geographical atlas of the near-surface Southern Ocean zooplankton. This atlas is based on 22,553 CPR samples collected from 1991 to 2008 from voyages operated by Australia, Japan, Germany, New Zealand, USA and Russia. The Atlas documents the distribution and abundance of the 50 most abundant zooplankton taxa amongst the 200+ taxa sampled. The maps are printed in alphabetical order of the genera within each taxon and nomenclature is based on the Register of Antarctic Marine Species (RAMS) developed by the SCAR Marine Biodiversity Information Network (SCAR-MarBIN). The SO-CPR Atlas will operate as a ready reference to researchers interested in the distribution of zooplankton in the Southern Ocean, for example knowing the distribution of grazers in relation to phytoplankton production or the availability of prey for higher predators.

  11. Water masses as a unifying framework for understanding the Southern Ocean Carbon Cycle

    Directory of Open Access Journals (Sweden)

    D. Iudicone

    2011-05-01

    Full Text Available The scientific motivation for this study is to understand the processes in the ocean interior controlling carbon transfer across 30° S. To address this, we have developed a unified framework for understanding the interplay between physical drivers such as buoyancy fluxes and ocean mixing, and carbon-specific processes such as biology, gas exchange and carbon mixing. Given the importance of density in determining the ocean interior structure and circulation, the framework is one that is organized by density and water masses, and it makes combined use of Eulerian and Lagrangian diagnostics. This is achieved through application to a global ice-ocean circulation model and an ocean biogeochemistry model, with both components being part of the widely-used IPSL coupled ocean/atmosphere/carbon cycle model.

    Our main new result is the dominance of the overturning circulation (identified by water masses in setting the vertical distribution of carbon transport from the Southern Ocean towards the global ocean. A net contrast emerges between the role of Subantarctic Mode Water (SAMW, associated with large northward transport and ingassing, and Antarctic Intermediate Water (AAIW, associated with a much smaller export and outgassing. The differences in their export rate reflects differences in their water mass formation processes. For SAMW, two-thirds of the surface waters are provided as a result of the densification of thermocline water (TW, and upon densification this water carries with it a substantial diapycnal flux of dissolved inorganic carbon (DIC. For AAIW, principal formatin processes include buoyancy forcing and mixing, with these serving to lighten CDW. An additional important formation pathway of AAIW is through the effect of interior processing (mixing, including cabelling that serve to densify SAMW.

    A quantitative evaluation of the contribution of mixing, biology and gas exchange to the DIC evolution per water mass reveals that

  12. Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

    Science.gov (United States)

    Trull, Thomas W.; Passmore, Abraham; Davies, Diana M.; Smit, Tim; Berry, Kate; Tilbrook, Bronte

    2018-01-01

    The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO2. This comes with a cost - an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC) on particles filtered from surface seawater into two size fractions: 50-1000 µm to capture foraminifera (the most important biogenic carbonate-forming zooplankton) and 1-50 µm to capture coccolithophores (the most important biogenic carbonate-forming phytoplankton). Ancillary measurements of biogenic silica (BSi) and particulate organic carbon (POC) provided context, as estimates of the biomass of diatoms (the highest biomass phytoplankton in polar waters) and total microbial biomass, respectively. Results for nine transects from Australia to Antarctica in 2008-2015 showed low levels of PIC compared to Northern Hemisphere polar waters. Coccolithophores slightly exceeded the biomass of diatoms in subantarctic waters, but their abundance decreased more than 30-fold poleward, while diatom abundances increased, so that on a molar basis PIC was only 1 % of BSi in Antarctic waters. This limited importance of coccolithophores in the Southern Ocean is further emphasized in terms of their associated POC, representing less than 1 % of total POC in Antarctic waters and less than 10 % in subantarctic waters. NASA satellite ocean-colour-based PIC estimates were in reasonable agreement with the shipboard results in subantarctic waters but greatly overestimated PIC in Antarctic waters. Contrastingly, the NASA Ocean Biogeochemical Model (NOBM) shows coccolithophores as overly

  13. Southern Ocean circulation changes across the last deglaciation: contribution from Marion-Dufresne cruises

    Science.gov (United States)

    Michel, Elisabeth; Siani, Giuseppe; Mazaud, Alain; Paterne, Martine; deVries, Tim; Jaccard, Samuel; Waelbroeck, Claire; Crosta, Xavier; Isguder, Gulay; Dewilde, Fabien; De Pol-Holz, Ricardo; Skinner, Luke; Kissel, Catherine

    2015-04-01

    The last deglaciation is marked by rapid climatic events linked to large reorganizations of the deep ocean circulation. To decipher the role of the Southern Ocean in these deep circulation changes requires reconstructing the evolution of its stratification and its zonal behavior during the last deglaciation from high resolution, well dated records. Furthermore, nowadays the connection between atmosphere and the deep ocean occurs through the Southern Ocean, and it might had a leading role in the evolution of atmospheric CO2 concentrations across the deglaciation. However, establishing a precise chronology for marine sediment records in high latitudes is a difficult task, as it requires the determination of radiocarbon surface water age changes. It has been possible to retrieve high sedimentation rate cores during Indian and Pacific oceanographic cruises, particularly PACHIDERME and INDIEN SUD expeditions. We pre. We aim at tying these marine records to terrestrial records, using tephra deposited in marine and terrestrial region in the different sector of the Southern Ocean when it is possible. This work is in progress within a French-Swedish project. We will present results at different depth from South West Pacific sector of the Southern Ocean and from the Indian sector. A precise chronology in the Indian sector requires to first establish the tephrochronology of Kerguelen Islands that is under progress. We compare these new records with previously published records of the Atlantic and Pacific sectors. It indicates that upwelling events drive radiocarbon changes in waters above 2500 m depth and increases in atmospheric CO2. Oceanic circulation changes are not synchroneous at deeper depth between 2500 and 4000 m depth. Southern Ocean temperature and vertical mixing increases occurs synchroneously with temperature increase above the Antarctic and atmospheric CO2 increases within error of marine and Ice chronologies, while the ACC current intensity decrease (or

  14. The Impact of the Ozone Hole on the Salinity of the Southern Ocean

    Science.gov (United States)

    Solomon, A. L.; Polvani, L. M.; Abernathey, R. P.; Smith, K. L.

    2014-12-01

    Observations have revealed systematic changes in the temperature andsalinity of the Southern Ocean since 1960. These trends reflect theevolving exchange of heat and momentum between atmosphere and ocean andare, in part, driven by anthropogenic emissions. The key question is:which emissions are most important, greenhouse gases or ozone depletingsubstances? We answer this question using CESM-WACCM, a comprehensiveclimate model with interactive stratospheric chemistry, coupled tostate-of-the-art land, ocean and sea-ice components. We find that thechanges in Southern Ocean temperature South of 60S are primarily due tothe presence of a seasonal ozone hole, and between 60S and 40S thetrends are driven in equal measure by ozone depletion and all otherforcings combined. Furthermore, we demonstrate substantial changes inthe model's ocean salinity, and show that these are greatly enhanced byformation of the ozone hole, a fact that has not been previously reported.

  15. A review of Tertiary climate changes in southern South America and the Antarctic Peninsula. Part 1: Oceanic conditions

    Science.gov (United States)

    Le Roux, J. P.

    2012-03-01

    Oceanic conditions around southern South America and the Antarctic Peninsula have a major influence on climate patterns in these subcontinents. During the Tertiary, changes in ocean water temperatures and currents also strongly affected the continental climates and seem to have been controlled in turn by global tectonic events and sea-level changes. During periods of accelerated sea-floor spreading, an increase in the mid-ocean ridge volumes and the outpouring of basaltic lavas caused a rise in sea-level and mean ocean temperature, accompanied by the large-scale release of CO2. The precursor of the South Equatorial Current would have crossed the East Pacific Rise twice before reaching the coast of southern South America, thus heating up considerably during periods of ridge activity. The absence of the Antarctic Circumpolar Current before the opening of the Drake Passage suggests that the current flowing north along the present western seaboard of southern South American could have been temperate even during periods of ridge inactivity, which might explain the generally warm temperatures recorded in the Southeast Pacific from the early Oligocene to middle Miocene. Along the east coast of southern South America, water temperatures also fluctuated between temperate-cool and warm until the early Miocene, when the first incursion of temperate-cold to cold Antarctic waters is recorded. The cold Falkland/Malvinas Current initiated only after the middle Miocene. After the opening of the Drake Passage, the South Equatorial Current would have joined the newly developed, cold Antarctic Circumpolar Current on its way to Southern South America. During periods of increased sea-floor spreading, it would have contributed heat to the Antarctic Circumpolar Current that caused a poleward shift in climatic belts. However, periods of decreased sea-floor spreading would have been accompanied by diminishing ridge volumes and older, cooler and denser oceanic plates, causing global sea

  16. Glacial to Interglacial Changes in Southern Ocean Water Mass Geometry, the ACC, and the Southern Westerlies at Drake Passage

    Science.gov (United States)

    Ninnemann, U. S.

    2008-12-01

    Resolving ocean and atmospheric variability in the Drake Passage region is crucial for advancing our understanding of the role of the Southern Ocean in affecting ocean and climate change. Modeling studies suggest that altering the position or strength of the Southern Westerly Winds (SWW) and the Antarctic Circumpolar Current (ACC) relative to the Drake Passage could play a central role in driving observed glacial-interglacial changes in the atmospheric concentration of carbon dioxide and the global ocean circulation. The records of past ocean-atmosphere changes contained in sediment archives provide a natural testing ground for these hypotheses. Here we present high-resolution benthic and planktonic foraminiferal δ13C and δ18O records from new sediment cores recovered along both meridional (IMAGES PACHIDERME cruise onboard the R/V Marion Dufresne of IPEV) and zonal (IPY PALEODRAKE cruise) transects. Together with existing Southern Ocean cores, the new records provide constraints on the vertical and spatial gradients in surface and bottom water properties necessary to portray changes in the position of water masses and frontal systems relative to Drake Passage and Southern Chile. Our initial planktonic δ18O results over the last deglaciation show a greater magnitude change in the northern Drake Passage (2.0‰) and along the Chilean margin (2.5‰) than is generally observed in records which are either south or far to the North of the Subantarctic Front (SAF) today. These results are consistent in both sign and magnitude with a northward shift in the Subantarctic Front and an increase in the flux of polar and supbolar water northward along the coast of Chile during the glaciation. In addition, the large glacial decrease (>1.5‰) in benthic foraminiferal (C. wuellerstorfi) δ13C values in core MD07-3128 (52S, 1032m) suggests that the boundary between intermediate water (relatively high δ13C) and circumpolar deep water (low δ13C) was shifted northward (or

  17. Southern Ocean Predicted Seafloor Topography Poster - MGG9

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 36 by 48 inch full color poster is MGG Report 9. In many areas of the global ocean, the depth of the seafloor is not well known because survey lines by ships...

  18. Long-term decline in krill stock and increase in salps within the Southern Ocean.

    Science.gov (United States)

    Atkinson, Angus; Siegel, Volker; Pakhomov, Evgeny; Rothery, Peter

    2004-11-04

    Antarctic krill (Euphausia superba) and salps (mainly Salpa thompsoni) are major grazers in the Southern Ocean, and krill support commercial fisheries. Their density distributions have been described in the period 1926-51, while recent localized studies suggest short-term changes. To examine spatial and temporal changes over larger scales, we have combined all available scientific net sampling data from 1926 to 2003. This database shows that the productive southwest Atlantic sector contains >50% of Southern Ocean krill stocks, but here their density has declined since the 1970s. Spatially, within their habitat, summer krill density correlates positively with chlorophyll concentrations. Temporally, within the southwest Atlantic, summer krill densities correlate positively with sea-ice extent the previous winter. Summer food and the extent of winter sea ice are thus key factors in the high krill densities observed in the southwest Atlantic Ocean. Krill need the summer phytoplankton blooms of this sector, where winters of extensive sea ice mean plentiful winter food from ice algae, promoting larval recruitment and replenishing the stock. Salps, by contrast, occupy the extensive lower-productivity regions of the Southern Ocean and tolerate warmer water than krill. As krill densities decreased last century, salps appear to have increased in the southern part of their range. These changes have had profound effects within the Southern Ocean food web.

  19. Southern Ocean frontal structure and sea-ice formation rates revealed by elephant seals.

    Science.gov (United States)

    Charrassin, J-B; Hindell, M; Rintoul, S R; Roquet, F; Sokolov, S; Biuw, M; Costa, D; Boehme, L; Lovell, P; Coleman, R; Timmermann, R; Meijers, A; Meredith, M; Park, Y-H; Bailleul, F; Goebel, M; Tremblay, Y; Bost, C-A; McMahon, C R; Field, I C; Fedak, M A; Guinet, C

    2008-08-19

    Polar regions are particularly sensitive to climate change, with the potential for significant feedbacks between ocean circulation, sea ice, and the ocean carbon cycle. However, the difficulty in obtaining in situ data means that our ability to detect and interpret change is very limited, especially in the Southern Ocean, where the ocean beneath the sea ice remains almost entirely unobserved and the rate of sea-ice formation is poorly known. Here, we show that southern elephant seals (Mirounga leonina) equipped with oceanographic sensors can measure ocean structure and water mass changes in regions and seasons rarely observed with traditional oceanographic platforms. In particular, seals provided a 30-fold increase in hydrographic profiles from the sea-ice zone, allowing the major fronts to be mapped south of 60 degrees S and sea-ice formation rates to be inferred from changes in upper ocean salinity. Sea-ice production rates peaked in early winter (April-May) during the rapid northward expansion of the pack ice and declined by a factor of 2 to 3 between May and August, in agreement with a three-dimensional coupled ocean-sea-ice model. By measuring the high-latitude ocean during winter, elephant seals fill a "blind spot" in our sampling coverage, enabling the establishment of a truly global ocean-observing system.

  20. Cloud amount/frequency, SALINITY and other data from ORION, FUJI II and other platforms in the Southern Oceans, Indian Ocean and other waters from 1950-01-04 to 1989-03-16 (NODC Accession 9200239)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Serial data in this accession was collected in Southern Oceans (> 60 degrees South) as part of Global Ocean Data Archeaology and Rescue (GODAR) project...

  1. Phenotypic plasticity of southern ocean diatoms: key to success in the sea ice habitat?

    Directory of Open Access Journals (Sweden)

    Olivia Sackett

    Full Text Available Diatoms are the primary source of nutrition and energy for the Southern Ocean ecosystem. Microalgae, including diatoms, synthesise biological macromolecules such as lipids, proteins and carbohydrates for growth, reproduction and acclimation to prevailing environmental conditions. Here we show that three key species of Southern Ocean diatom (Fragilariopsis cylindrus, Chaetoceros simplex and Pseudo-nitzschia subcurvata exhibited phenotypic plasticity in response to salinity and temperature regimes experienced during the seasonal formation and decay of sea ice. The degree of phenotypic plasticity, in terms of changes in macromolecular composition, was highly species-specific and consistent with each species' known distribution and abundance throughout sea ice, meltwater and pelagic habitats, suggesting that phenotypic plasticity may have been selected for by the extreme variability of the polar marine environment. We argue that changes in diatom macromolecular composition and shifts in species dominance in response to a changing climate have the potential to alter nutrient and energy fluxes throughout the Southern Ocean ecosystem.

  2. Turbidity, SOLAR RADIATION - ATMOSPHERIC and other data from PROFESSOR SIEDLECKI in the Southern Oceans from 1977-01-01 to 1978-12-31 (NODC Accession 9600122)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Serial data in this accession was collected in Southern Oceans (> 60 degrees South) in Polish Antarctic stations as part of Global Ocean Data...

  3. The influence of historical climate changes on Southern Ocean marine predator populations: a comparative analysis.

    Science.gov (United States)

    Younger, Jane L; Emmerson, Louise M; Miller, Karen J

    2016-02-01

    The Southern Ocean ecosystem is undergoing rapid physical and biological changes that are likely to have profound implications for higher-order predators. Here, we compare the long-term, historical responses of Southern Ocean predators to climate change. We examine palaeoecological evidence for changes in the abundance and distribution of seabirds and marine mammals, and place these into context with palaeoclimate records in order to identify key environmental drivers associated with population changes. Our synthesis revealed two key factors underlying Southern Ocean predator population changes; (i) the availability of ice-free ground for breeding and (ii) access to productive foraging grounds. The processes of glaciation and sea ice fluctuation were key; the distributions and abundances of elephant seals, snow petrels, gentoo, chinstrap and Adélie penguins all responded strongly to the emergence of new breeding habitat coincident with deglaciation and reductions in sea ice. Access to productive foraging grounds was another limiting factor, with snow petrels, king and emperor penguins all affected by reduced prey availability in the past. Several species were isolated in glacial refugia and there is evidence that refuge populations were supported by polynyas. While the underlying drivers of population change were similar across most Southern Ocean predators, the individual responses of species to environmental change varied because of species specific factors such as dispersal ability and environmental sensitivity. Such interspecific differences are likely to affect the future climate change responses of Southern Ocean marine predators and should be considered in conservation plans. Comparative palaeoecological studies are a valuable source of long-term data on species' responses to environmental change that can provide important insights into future climate change responses. This synthesis highlights the importance of protecting productive foraging grounds

  4. Importance of mesoscale eddies and mean circulation in ventilation of the Southern Ocean

    Science.gov (United States)

    Kamenkovich, Igor; Garraffo, Zulema; Pennel, Romain; Fine, Rana A.

    2017-04-01

    This study examines the relative importance of the mean advection and mesoscale currents in the property exchange between the Southern Ocean mixed layer and downstream in the upper 2000 m; this exchange is referred to as ventilation. A new, highly efficient off-line tracer model employed here uses precalculated velocities to advect dynamically passive tracers. Two idealized tracers are considered: the Boundary Impulse Response (BIR) tracer, which helps to determine the ventilation pathways and time scales, and the Transient Surface Tracer (TST), which is relevant to transient atmospheric tracers. The importance of eddies is isolated by contrasting the control simulation with a simulation without mesoscale currents. The analysis reveals complex three-dimensional ventilation pathways, controlled by the interplay between the mean advection and eddy-induced spreading. The mean currents carry the tracers eastward within ACC and contribute to the formation of the Antarctic Intermediate Water (AAIW) in the South Pacific and South Atlantic. The main effect of eddies is to disperse tracers away from the mean pathways, and this dispersion acts to retain the BIR tracer in the Atlantic and Indian sectors and reduce the upstream influence of these regions on the South Pacific. In addition, the eddy-induced along-isopycnal spreading within ACC increases the ventilated depth and the inventory of TST. The results can be used to interpret distribution of tracers in the ocean in numerical simulations and observations.

  5. The Effects of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in an AOGCM

    Science.gov (United States)

    Li, Feng; Newman, Paul; Pawson, Steven; Waugh, Darryn

    2014-01-01

    Stratospheric ozone depletion has played a dominant role in driving Antarctic climate change in the last decades. In order to capture the stratospheric ozone forcing, many coupled atmosphere-ocean general circulation models (AOGCMs) prescribe the Antarctic ozone hole using monthly and zonally averaged ozone field. However, the prescribed ozone hole has a high ozone bias and lacks zonal asymmetry. The impacts of these biases on model simulations, particularly on Southern Ocean and the Antarctic sea ice, are not well understood. The purpose of this study is to determine the effects of using interactive stratospheric chemistry instead of prescribed ozone on Antarctic and Southern Ocean climate change in an AOGCM. We compare two sets of ensemble simulations for the 1960-2010 period using different versions of the Goddard Earth Observing System 5 - AOGCM: one with interactive stratospheric chemistry, and the other with prescribed monthly and zonally averaged ozone and 6 other stratospheric radiative species calculated from the interactive chemistry simulations. Consistent with previous studies using prescribed sea surface temperatures and sea ice concentrations, the interactive chemistry runs simulate a deeper Antarctic ozone hole and consistently larger changes in surface pressure and winds than the prescribed ozone runs. The use of a coupled atmosphere-ocean model in this study enables us to determine the impact of these surface changes on Southern Ocean circulation and Antarctic sea ice. The larger surface wind trends in the interactive chemistry case lead to larger Southern Ocean circulation trends with stronger changes in northerly and westerly surface flow near the Antarctica continent and stronger upwelling near 60S. Using interactive chemistry also simulates a larger decrease of sea ice concentrations. Our results highlight the importance of using interactive chemistry in order to correctly capture the influences of stratospheric ozone depletion on climate

  6. The post-2002 global surface warming slowdown caused by the subtropical Southern Ocean heating acceleration

    Science.gov (United States)

    Oka, A.; Watanabe, M.

    2017-04-01

    The warming rate of global mean surface temperature slowed down during 1998-2012. Previous studies pointed out role of increasing ocean heat uptake during this global warming slowdown, but its mechanism remains under discussion. Our numerical simulations, in which wind stress anomaly in the equatorial Pacific is imposed from reanalysis data, suggest that subsurface warming in the equatorial Pacific took place during initial phase of the global warming slowdown (1998-2002), as previously reported. It is newly clarified that the Ekman transport from tropics to subtropics is enhanced during the later phase of the slowdown (after 2002) and enhanced subtropical Ekman downwelling causes accelerated heat storage below depth of 700 m in the subtropical Southern Ocean, leading to the post-2002 global warming slowdown. Observational data of ocean temperature also support this scenario. This study provides clear evidence that deeper parts of the Southern Ocean play a critical role in the post-2002 warming slowdown.

  7. The Southern Ocean deep sea: first insights into biodiversity and biogeography

    DEFF Research Database (Denmark)

    Brandt, A.; Brix, S.; Brökeland, W.

    2007-01-01

    Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa1. The deeper parts of the Southern Ocean exhibit some unique environmen......Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa1. The deeper parts of the Southern Ocean exhibit some unique...

  8. Southern Ocean acidification: a tipping point at 450-ppm atmospheric CO2.

    Science.gov (United States)

    McNeil, Ben I; Matear, Richard J

    2008-12-02

    Southern Ocean acidification via anthropogenic CO(2) uptake is expected to be detrimental to multiple calcifying plankton species by lowering the concentration of carbonate ion (CO(3)(2-)) to levels where calcium carbonate (both aragonite and calcite) shells begin to dissolve. Natural seasonal variations in carbonate ion concentrations could either hasten or dampen the future onset of this undersaturation of calcium carbonate. We present a large-scale Southern Ocean observational analysis that examines the seasonal magnitude and variability of CO(3)(2-) and pH. Our analysis shows an intense wintertime minimum in CO(3)(2-) south of the Antarctic Polar Front and when combined with anthropogenic CO(2) uptake is likely to induce aragonite undersaturation when atmospheric CO(2) levels reach approximately 450 ppm. Under the IPCC IS92a scenario, Southern Ocean wintertime aragonite undersaturation is projected to occur by the year 2030 and no later than 2038. Some prominent calcifying plankton, in particular the Pteropod species Limacina helicina, have important veliger larval development during winter and will have to experience detrimental carbonate conditions much earlier than previously thought, with possible deleterious flow-on impacts for the wider Southern Ocean marine ecosystem. Our results highlight the critical importance of understanding seasonal carbon dynamics within all calcifying marine ecosystems such as continental shelves and coral reefs, because natural variability may potentially hasten the onset of future ocean acidification.

  9. Bioavailable iron in the Southern Ocean: the significance of the iceberg conveyor belt.

    Science.gov (United States)

    Raiswell, Rob; Benning, Liane G; Tranter, Martyn; Tulaczyk, Slawek

    2008-05-30

    Productivity in the Southern Oceans is iron-limited, and the supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine reservoir. Glacial sediment sources of iron have rarely been considered, as the iron has been assumed to be inert and non-bioavailable. This study demonstrates the presence of potentially bioavailable Fe as ferrihydrite and goethite in nanoparticulate clusters, in sediments collected from icebergs in the Southern Ocean and glaciers on the Antarctic landmass. Nanoparticles in ice can be transported by icebergs away from coastal regions in the Southern Ocean, enabling melting to release bioavailable Fe to the open ocean. The abundance of nanoparticulate iron has been measured by an ascorbate extraction. This data indicates that the fluxes of bioavailable iron supplied to the Southern Ocean from aeolian dust (0.01-0.13 Tg yr(-1)) and icebergs (0.06-0.12 Tg yr(-1)) are comparable. Increases in iceberg production thus have the capacity to increase productivity and this newly identified negative feedback may help to mitigate fossil fuel emissions.

  10. The Soundscape of the Southern Ocean – How Quiet and how Loud can Nature be?

    OpenAIRE

    Kindermann, Lars; Boebel, Olaf; van Opzeeland, Ilse

    2011-01-01

    The Southern Ocean around the Antarctic continent provides some of the most extreme environmental conditions on earth which shape also the unique underwater soundscape. The area probably contains the most quiet locations within the world's oceans but is also stage for some of the loudest natural events. It is still relatively void of anthropogenic noise and is one of the most important feeding grounds for great whales. However, comparatively little acoustic data exists from this region so far...

  11. Response of bacterioplankton to iron fertilization of the Southern Ocean, Antarctica

    OpenAIRE

    Singh, Sanjay K.; Kotakonda, Arunasri; Kapardar, Raj K.; Kankipati, Hara Kishore; Sreenivasa Rao, Pasupuleti; Sankaranarayanan, Pratibha Mambatta; Vetaikorumagan, Sundareswaran R.; Gundlapally, Sathyanarayana Reddy; Nagappa, Ramaiah; Shivaji, Sisinthy

    2015-01-01

    Ocean iron fertilization is an approach to increase CO2 sequestration. The Indo-German iron fertilization experiment “LOHAFEX” was carried out in the Southern Ocean surrounding Antarctica in 2009 to monitor changes in bacterial community structure following iron fertilization-induced phytoplankton bloom of the seawater from different depths. 16S rRNA gene libraries were constructed using metagenomic DNA from seawater prior to and after iron fertilization and the clones were sequenced for iden...

  12. IMOS: How seals are changing the way we monitor the Southern Ocean

    Science.gov (United States)

    Harcourt, R.; McMahon, C.; Jonsen, I.; Goldsworthy, S.; Hindell, M.; Hoenner, X.; Thums, M.

    2016-02-01

    IMOS (Integrated Marine Observing System) operates a wide range of ocean observing equipment throughout Australia's coastal waters and also the open oceans. This fully integrated, national system, covers physical, chemical and biological ocean sciences forming the basis for robust and informed study of the worlds oceans. Of particular interest in understanding global climate processes is the Southern Ocean (SO), but studying this remote region is difficult and most observations are collected during the short ice-free summer when the region is accessible. Through Winter and Spring it is extremely difficult to collect biophysical ocean information in the Southern Ocean. The importance of good observations from this region, the home of the Antarctic Circumpolar Current (ACC), the largest current system in the world, which connects water masses from the global ocean basins cannot be over emphasised. IMOS through the Australian Animal Tracking and Monitoring System (AATAMS) has made important inroads into collecting otherwise hard to obtain observations from the SO by using CTD bio-loggers to monitor coastal and oceanic movements of marine animals from the Australian mainland as far south as the Antarctic continent. In particular seals equipped with satellite-linked CTD tags have provided unique temporal and spatial coverage of the Southern Ocean. This includes extensive data from the Antarctic continental slope and shelf regions during the winter months, which is outside the conventional areas of Argo autonomous floats and ship-based studies. Over 75,000 temperature and salinity profiles have been collected from 20-140 °E, between the Kerguelen archipelago and Prydz Bay Antarctica. These data offer invaluable new insights into the water masses, oceanographic processes and provides a vital tool for oceanographers seeking to advance our understanding of this key component of the global ocean climate. Here we present an overview of the IMOS database of hydrographic (i

  13. Optical Measurements and Modeling to Estimate Concentrations and Fluxes of Organic Matter in the Southern Ocean

    Science.gov (United States)

    Stramski, Dariusz; Mitchell, B. Greg; Marra, John W. (Technical Monitor)

    2001-01-01

    This project was a collaboration between two Principal Investigators, Dr. Dariusz Stramski and Dr. Greg Mitchell of Scripps Institution of Oceanography, University of California San Diego. Our overall goal was to conduct optical measurements and modeling to estimate concentrations of organic matter in the Southern Ocean in support of the U.S. JGOFS Process Study in this region. Key variables and processes of high relevance to accomplish the JGOFS goals include time and space resolution of phytoplankton pigments, particulate organic carbon, and the formation and export of organic carbon. Our project focused on establishing the fundamental relationships for parameterization of these variables and processes in terms of the optical properties of seawater, and developing understanding of why the Southern Ocean differs from other low-latitude systems, or has differentiation within. Our approach builds upon historical observations that optical properties provide a useful proxy for key reservoirs of organic matter such as chlorophyll alpha (Chl) and particulate organic carbon (POC) concentrations, which are of relevance to the JGOFS objectives. We carried out detailed studies of in situ and water sample optical properties including spectral reflectance, absorption, beam attenuation, scattering, and backscattering coefficients. We evaluated the ability to estimate Chl from the spectral reflectance (ocean color) in the Southern Ocean. We examined relationships between the ocean optical properties and particulate organic carbon. We developed, for the first time, an algorithm for estimating particulate organic carbon concentration in the surface ocean from satellite imagery of ocean color. With this algorithm, we obtained maps of POC distribution in the Southern Ocean showing the seasonal progression of POC in the austral spring-summer season. We also developed a semianalytical reflectance model for the investigated polar waters based on our field measurements of absorption

  14. Phytoplankton community structure is influenced by seabird guano enrichment in the Southern Ocean

    Science.gov (United States)

    Shatova, O. A.; Wing, S. R.; Hoffmann, L. J.; Wing, L. C.; Gault-Ringold, M.

    2017-05-01

    Phytoplankton biomass, productivity and community structure are strongly influenced by differences in nutrient concentrations among oceanographic water masses. Changes in community composition, particularly in the distribution of cell sizes, can result in dramatic changes in the energetics of pelagic food webs and ecosystem function in terms of biogeochemical cycling and carbon sequestration. Here we examine responses of natural phytoplankton communities from four major water masses in the Southern Ocean to enrichment from seabird guano, a concentrated source of bioactive metals (Mn, Fe, Co, Ni, Cu, Zn) and macronutrients (N, P), in a series of incubation experiments. Phytoplankton communities from sub-tropical water, modified sub-tropical water from the Snares Island wake, sub-Antarctic water and Antarctic water from the Ross Sea, each showed dramatic changes in community structure following additions of seabird guano. We observed particularly high growth of prymnesiophytes in response to the guano-derived nutrients within sub-Antarctic and sub-tropical frontal zones, resulting in communities dominated by larger cell sizes than in control incubations. Community changes within treatments enriched with guano were distinct, and in most cases more extensive, than those observed for treatments with additions of macronutrients (N, P) or iron (Fe) alone. These results provide the first empirical evidence that seabird guano enrichment can drive significant changes in the structure and composition of natural phytoplankton communities. Our findings have important implications for understanding the consequences of accumulation of bioactive metals and macronutrients within food webs and the role of seabirds as nutrient vectors within the Southern Ocean ecosystem.

  15. 50 CFR Figure 1 to Subpart G of... - Boundaries of the Statistical Reporting Area in the Southern Ocean

    Science.gov (United States)

    2010-10-01

    ... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Boundaries of the Statistical Reporting Area in the Southern Ocean 1 Figure 1 to Subpart G of Part 300 Wildlife and Fisheries INTERNATIONAL... in the Southern Ocean EC01JY91.072 ...

  16. Astronomically-induced Mid-Brunhes Transition in the Southern and Deep Oceans

    Science.gov (United States)

    Yin, Qiuzhen

    2013-04-01

    The interglacials after 430 ka (ka: 1000 years) ago were characterized by warmer climates and higher atmospheric CO2 concentrations than the interglacials before, but the cause of this climatic transition (the so-called Mid-Brunhes Event, MBE) is unknown. Based on model simulations, my results show that, in response to insolation changes only, feedbacks between sea ice, temperature, evaporation and salinity caused vigorous pre-MBE Antarctic Bottom Water formation and Southern Ocean ventilation. My results also show that strong Westerlies increased the pre-MBE overturning in the Southern Ocean via an increased latitudinal insolation gradient created by changes in eccentricity during austral winter and in obliquity during austral summer. The stronger bottom water formation led to a cooler deep ocean during the older interglacials. These insolation-induced differences in the deep-sea temperature and in the Southern Ocean ventilation between the more recent interglacials and the older ones were not expected, because there is no straightforward visible systematic difference in the astronomical parameters between the interglacials before and after 430 ka ago. Rather than being a real "event", the apparent MBE (i.e. the difference in the interglacial intensity before and after 430 ka BP) appears in my results to come from the complex response of the climate system to the astronomical and insolation forcings prevailing before and after 430 ka BP. This does not mean that nothing could have happened between MIS-13 and MIS-11 which might have amplified such difference. Given the important roles of the Southern and Deep Oceans on the carbon cycle, these findings are a first step towards understanding the magnitude change of the interglacial CO2 concentration around 430 ka. Reference: Yin Q.Z., 2013. Insolation-induced Mid-Brunhes Transition in the Southern and Deep Oceans. Nature, DOI 10.1038/nature11790. Acknowledgement: This work is supported by the European Research Council

  17. Revisiting Ocean Color algorithms for chlorophyll a and particulate organic carbon in the Southern Ocean using biogeochemical floats

    Science.gov (United States)

    Haëntjens, Nils; Boss, Emmanuel; Talley, Lynne D.

    2017-08-01

    The Southern Ocean (SO) ecosystem plays a key role in the carbon cycle by sinking a major part (43%) of the ocean uptake of anthropogenic CO2, and being an important source of nutrients for primary producers. However, undersampling of SO biogeochemical properties limits our understanding of the mechanisms taking place in this remote area. The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project has been deploying a large number of autonomous biogeochemical floats to study the SO (as of December 2016, 74 floats out of 200 have been deployed). SOCCOM floats measurements can be used to extend remote sensing chlorophyll a (chl a) and particulate organic carbon (POC) products under clouds or during the polar night as well as adding the depth dimension to the satellite-based view of the SO. Chlorophyll a concentrations measured by a sensor embedded on the floats and POC concentrations derived from backscattering coefficients were calibrated with samples collected during the floats' deployment cruise. Float chl a and POC were compared with products derived from observations of MODIS and VIIRS sensors. We find the Ocean Color Index (OCI) global algorithm to agree well with the matchups (within 9%, on average, for the Visible Infrared Imaging Radiometer Suite (VIIRS) and 12%, on average, for the Moderate Resolution Imaging Spectroradiometer Aqua (MODIS)). SO-specific algorithms estimating chl a are offset by ˜45% south of the Sea Ice Extent Front (˜60°S). In addition, POC estimates based on floats agree well with NASA's POC algorithm.

  18. Iron fertilization and the structure of planktonic communities in high nutrient regions of the Southern Ocean

    Science.gov (United States)

    Quéguiner, Bernard

    2013-06-01

    In this review article, plankton community structure observations are analyzed both for artificial iron fertilization experiments and also for experiments dedicated to the study of naturally iron-fertilized systems in the Atlantic, Indian and Pacific sectors of the Southern Ocean in the POOZ (Permanently Open Ocean Zone) and the PFZ (Polar Frontal Zone). Observations made in natural systems are combined with those from artificially perturbed systems, in order to evaluate the seasonal evolution of pelagic communities, taking into account controlling factors related to the life cycles and the ecophysiology of dominant organisms. The analysis considers several types of planktonic communities, including both autotrophs and heterotrophs. These communities are spatially segregated owing to different life strategies. A conceptual general scheme is proposed to account for these observations and their variability, regardless of experiment type. Diatoms can be separated into 2 groups: Group 1 has slightly silicified fast growing cells that are homogeneously distributed in the surface mixed layer, and Group 2 has strongly silicified slowly growing cells within discrete layers. During the growth season, Group 1 diatoms show a typical seasonal succession of dominant species, within time windows of development that are conditioned by physical factors (light and temperature) as well as endogenous specific rhythms (internal clock), and biomass accumulation is controlled by the availability of nutrients. Group 1 diatoms are not directly grazed by mesozooplankton which is fed by protozooplankton, linking the microbial food web to higher trophic levels. Instead, successive dominant species of Group 1 are degraded via bacterial activity at the end of their growth season. Organic detritus fragments feed protozooplankton and mesozooplankton. The effective silicon pump leads to the progressive disappearance of silicic acid in surface waters. In contrast, Group 2 is resistant to grazing

  19. Distribution, abundance and ecological relevance of pelagic fishes in the Lazarev Sea, Southern Ocean

    NARCIS (Netherlands)

    Flores, Hauke; de Putte, Anton P. Van; Siegel, Volker; Pakhomov, Evgeny A.; Van Franeker, Jan A.; Meesters, Hugo W. G.; Volckaert, Filip A. M.

    2008-01-01

    The distribution and abundance of larval and postlarval fishes was investigated in the Lazarev Sea, Southern Ocean, in March and April 2004. The upper 200 m of the water column were sampled with an 8 m(2) rectangular midwater trawl at 93 stations. The larval species community clustered in a diverse

  20. Biogeochemical cycling of cadmium isotopes in the Southern Ocean along the Zero Meridian

    NARCIS (Netherlands)

    Abouchami, W.; Galer, S.J.G.; de Baar, H.J.W.; Middag, R.; Vance, D.; Zhao, Y.; Klunder, M.; Mezger, K.; Feldmann, H.; Andreae, M.O.; Bowie, Andrew Ross

    2014-01-01

    We present depth profiles of Cd isotopes and concentrations from the Southern Ocean at four stations in the Atlantic sector along the Greenwich Meridian (47 degrees S to 68 degrees S) located across the main Antarctic frontal zones and productivity belt. The vertical profiles of Cd concentration

  1. Biogeochemical cycling of zinc and its isotopes in the Southern Ocean

    NARCIS (Netherlands)

    Zhao, Y.; Vance, D.; Abouchami, W.; de Baar, H.J.W.; Rehkamper, Mark

    2014-01-01

    We report Zn concentration and isotope data for seawater samples from the Atlantic sector of the Southern Ocean, collected during the IPY/GEOTRACES ANT-XXIV/III cruise along the Greenwich Zero Meridian. Data are reported for the full depth range of the water column at three stations, as well as a

  2. Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning.

    Science.gov (United States)

    Golledge, N R; Menviel, L; Carter, L; Fogwill, C J; England, M H; Cortese, G; Levy, R H

    2014-09-29

    During the last glacial termination, the upwelling strength of the southern polar limb of the Atlantic Meridional Overturning Circulation varied, changing the ventilation and stratification of the high-latitude Southern Ocean. During the same period, at least two phases of abrupt global sea-level rise--meltwater pulses--took place. Although the timing and magnitude of these events have become better constrained, a causal link between ocean stratification, the meltwater pulses and accelerated ice loss from Antarctica has not been proven. Here we simulate Antarctic ice sheet evolution over the last 25 kyr using a data-constrained ice-sheet model forced by changes in Southern Ocean temperature from an Earth system model. Results reveal several episodes of accelerated ice-sheet recession, the largest being coincident with meltwater pulse 1A. This resulted from reduced Southern Ocean overturning following Heinrich Event 1, when warmer subsurface water thermally eroded grounded marine-based ice and instigated a positive feedback that further accelerated ice-sheet retreat.

  3. Wandering whales? : Relationships between baleen whales and the sea ice environment in the Southern Ocean

    NARCIS (Netherlands)

    Beekmans, Bas

    2017-01-01

    Each austral summer large baleen whales migrate into the Southern Ocean to feed on krill. The melting of sea ice leads to algal blooms which allow rapid growth and development of krill. In order to predict how baleen whales will respond to long-term changes in the physical environment, we need to

  4. Iron from melting glaciers fuels the phytoplankton blooms in Amundsen Sea (Southern Ocean) : Iron biogeochemistry

    NARCIS (Netherlands)

    Gerringa, Loes J. A.; Alderkamp, Anne-Carlijn; Laan, Patrick; Thuroczy, Charles-Edouard; De Baar, Hein J. W.; Mills, Matthew M.; van Dijken, Gert L.; van Haren, Hans; Arrigo, Kevin R.

    2012-01-01

    Dissolved iron (DFe) and total dissolvable Fe (TDFe) were measured in January-February 2009 in Pine Island Bay, as well as in the Pine Island and Amundsen polynyas (Amundsen Sea, Southern Ocean). Iron (Fe) has been shown to be a limiting nutrient for phytoplankton growth, even in the productive

  5. Accumulation status of persistent organochlorines in albatrosses from the North Pacific and the Southern Ocean.

    Science.gov (United States)

    Guruge, K S; Watanabe, M; Tanaka, H; Tanabe, S

    2001-01-01

    Current status of contamination by persistent organochlorines (OCs) such as polychlorinated biphenyles (PCBs), dichlorodiphenyl trichloroethane and its metabolites (DDTs), isomers of hexachlorocyclohexane (HCHs), hexachlorobenzene (HCB) and chlordane compounds (CHLs) were examined in 61 individuals belonging to eight albatross species collected from the North Pacific and the Southern Ocean. Generally high OC concentrations were found in albatrosses from the North Pacific than those from the Southern Oceans. Black-footed albatrosses had noticeably high PCBs and DDTs concentrations with mean values of 92 and 33 micrograms/g wet weight in subcutaneous fat, respectively. Among the other OCs, concentration of CHLs was higher than that of HCB in North Pacific albatrosses. HCHs accumulation was the lowest among all the OCs analyzed. Species-specific differences were observed for HCB, CHLs and DDTs in some species in the Southern Ocean. No significant difference of gender and age-related accumulation was observed in total OCs. However, PCB concentrations were higher in mature birds than those from immature ones in the Southern Ocean. Species-specific accumulation patterns of OCs in albatrosses were closely related with their feeding, migration, age and geographical ranges.

  6. Short-term photoacclimation effects on photoinhibition of phytoplankton in the Drake Passage (Southern Ocean)

    NARCIS (Netherlands)

    Alderkamp, A.C.; Garcon, V.; de Baar, H.J.W.; Arrigo, K.R.

    2011-01-01

    We assessed whether short-term photoacclimation responses of natural phytoplankton populations in the Drake Passage (Southern Ocean) were affecting protection from photodamage as cells are mixed up to the surface from depth. To this end, we measured phytoplankton fluorescence characteristics and

  7. Coccolith distribution patterns in South Atlantic and Southern Ocean surface sediments in relation to environmental gradients

    DEFF Research Database (Denmark)

    Boeckel, B.; Baumann, K.-H.; Henrich, R.

    2006-01-01

    In this study, the coccolith compositions of 213 surface sediment samples from the South Atlantic and Southern Ocean were analysed with respect to the environmental parameters of the overlying surface waters. From this data set, the abundance patterns of the main species and their ecological affi...

  8. Phytoplankton and pigment patterns across frontal zones in the Atlantic sector of the Southern Ocean

    NARCIS (Netherlands)

    Van Leeuwe, M.A.; Kattner, G.; van Oijen, T.; de Jong, J.T.M.; de Baar, H.J.W.

    2015-01-01

    Phytoplankton distribution and concentrations of macronutrients and iron were studied in the Polar Frontal Zone (PFZ) and the eastern Weddell Gyre of the Southern Ocean, during austral autumn. HPLC analysis of algal pigments was combined with microscopy observations to assess algal distribution.

  9. Biological oceanography across the Southern Indian Ocean – basinscale trends in the zooplankton community

    DEFF Research Database (Denmark)

    Jonasdottir, Sigrun; Nielsen, Torkel Gissel; Borg, Christian Marc Andersen

    2013-01-01

    We present a study on the protozooplankton 45 mm and copepods larger than 50 mm at a series of contrasting stations across the Southern Indian Ocean (SIO). Numerically, over 80% of the copepod community across the transect was less than 650 mm in size, dominated by nauplii, and smaller copepods, ...

  10. Cetacean surveys in the Southern Ocean using icebreaker-supported helicopters

    NARCIS (Netherlands)

    Scheidat, M.; Friedlaender, A.; Kock, K.H.; Lehnert, L.; Boebel, O.; Roberts, J.; Williams, R.

    2011-01-01

    Cetaceans in the Southern Ocean are potentially impacted by anthropogenic activities, such as direct hunting or through indirect effects of a reduced sea ice due to climate change. Knowledge on the distribution of cetacean species in this area is important for conservation, but the remoteness of the

  11. Exposing XBT bias in the Atlantic sector of the Southern Ocean

    CSIR Research Space (South Africa)

    Hutchinson, KA

    2013-10-01

    Full Text Available Hydrographic data from three research cruises, occupying the GoodHope line in the Atlantic sector of the Southern Ocean, are used to identify and quantify Expendable Bathythermograph (XBT) temperature biases. A set of 148 collocated XBT and CTD...

  12. Macrofauna under sea ice and in the open surface layer of the Lazarev Sea, Southern Ocean

    NARCIS (Netherlands)

    Florentino De Souza Silva, A.P.; Franeker, van J.A.; Cisewski, B.; Leach, H.; Putte, van de A.P.; Meesters, H.W.G.; Bathmann, U.; Wolff, W.J.

    2011-01-01

    A new fishing gear was used to sample the macrozooplankton and micronekton community in the surface layer (0–2 m) under ice and in open water, the Surface and Under Ice Trawl (SUIT). In total, 57 quantitative hauls were conducted in the Lazarev Sea (Southern Ocean) during 3 different seasons (autumn

  13. Macrofauna under sea ice and in the open surface layer of the Lazarev Sea, Southern Ocean

    NARCIS (Netherlands)

    Flores, Hauke; van Franeker, Jan-Andries; Cisewski, Boris; Leach, Harry; Van de Putte, Anton P.; Meesters, Erik (H. W. G.); Bathmann, Ulrich; Wolff, Wirn J.

    2011-01-01

    A new fishing gear was used to sample the macrozooplankton and micronekton community in the surface layer (0-2 m) under ice and in open water, the Surface and Under Ice Trawl (SUIT). In total, 57 quantitative hauls were conducted in the Lazarev Sea (Southern Ocean) during 3 different seasons (autumn

  14. First insights into the biodiversity and biogeography of the Southern Ocean deep sea

    NARCIS (Netherlands)

    Brandt, A.; Gooday, A.J.; Brandao, S.N.; Mesel, de I.G.

    2007-01-01

    Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique environmental

  15. The impact of ENSO on Southern African rainfall in CMIP5 ocean atmosphere coupled climate models

    Science.gov (United States)

    Dieppois, Bastien; Rouault, Mathieu; New, Mark

    2015-11-01

    We study the ability of 24 ocean atmosphere global coupled models from the Coupled Model Intercomparison Project 5 (CMIP5) to reproduce the teleconnections between El Niño Southern Oscillation (ENSO) and Southern African rainfall in austral summer using historical forced simulations, with a focus on the atmospheric dynamic associated with El Niño. Overestimations of summer rainfall occur over Southern Africa in all CMIP5 models. Abnormal westward extensions of ENSO patterns are a common feature of all CMIP5 models, while the warming of the Indian Ocean that happens during El Niño is not correctly reproduced. This could impact the teleconnection between ENSO and Southern African rainfall which is represented with mixed success in CMIP5 models. Large-scale anomalies of suppressed deep-convection over the tropical maritime continent and enhanced convection from the central to eastern Pacific are correctly simulated. However, regional biases occur above Africa and the Indian Ocean, particularly in the position of the deep convection anomalies associated with El Niño, which can lead to the wrong sign in rainfall anomalies in the northwest part of South Africa. From the near-surface to mid-troposphere, CMIP5 models underestimate the observed anomalous pattern of pressure occurring over Southern Africa that leads to dry conditions during El Niño years.

  16. A tale of three islands: Downstream natural iron fertilization in the Southern Ocean

    Science.gov (United States)

    Robinson, J.; Popova, E. E.; Srokosz, M. A.; Yool, A.

    2016-05-01

    Iron limitation of primary productivity prevails across much of the Southern Ocean but there are exceptions; in particular, the phytoplankton blooms associated with the Kerguelen Plateau, Crozet Islands, and South Georgia. These blooms occur annually, fertilized by iron and nutrient-rich shelf waters that are transported downstream from the islands. Here we use a high-resolution (1/12°) ocean general circulation model and Lagrangian particle tracking to investigate whether inter-annual variability in the potential lateral advection of iron could explain the inter-annual variability in the spatial extent of the blooms. Comparison with ocean color data, 1998-2007, suggests that iron fertilization via advection can explain the extent of each island's annual bloom, but only the inter-annual variability of the Crozet bloom. The area that could potentially be fertilized by iron from Kerguelen was much larger than the bloom, suggesting that there is another primary limiting factor, potentially silicate, that controls the inter-annual variability of bloom spatial extent. For South Georgia, there are differences in the year-to-year timing of advection and consequently fertilization, but no clear explanation of the inter-annual variability observed in the bloom's spatial extent has been identified. The model results suggest that the Kerguelen and Crozet blooms are terminated by nutrient exhaustion, probably iron and or silicate, whereas the deepening of the mixed layer in winter terminates the South Georgia bloom. Therefore, iron fertilization via lateral advection alone can explain the annual variability of the Crozet bloom, but not fully that of the Kerguelen and South Georgia blooms.

  17. Oceans around Southern Africa and regional effects of global change

    CSIR Research Space (South Africa)

    Lutjeharms, JRE

    2001-03-01

    Full Text Available Current proper.32 This does not imply that no water from the eastern side of the island of Madagascar reaches the AgulhasCurrent,butthatthiswaterdoesnotcomefromtheEast Madagascar Current itself. It is possible that rings and filaments of this water reach... in the South West In- dian Ocean subgyre.31 The contribution through the Mozambique Channel is small by comparison. It seems that the southernlimboftheEastMadagascarCurrent?anotherpoten- tial contributory ? makes no significant contribution to the Agulhas...

  18. Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice.

    Science.gov (United States)

    Liu, Jiping; Curry, Judith A

    2010-08-24

    The observed sea surface temperature in the Southern Ocean shows a substantial warming trend for the second half of the 20th century. Associated with the warming, there has been an enhanced atmospheric hydrological cycle in the Southern Ocean that results in an increase of the Antarctic sea ice for the past three decades through the reduced upward ocean heat transport and increased snowfall. The simulated sea surface temperature variability from two global coupled climate models for the second half of the 20th century is dominated by natural internal variability associated with the Antarctic Oscillation, suggesting that the models' internal variability is too strong, leading to a response to anthropogenic forcing that is too weak. With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean, and indicate that anthropogenic forcing exceeds natural internal variability. The increased heating from below (ocean) and above (atmosphere) and increased liquid precipitation associated with the enhanced hydrological cycle results in a projected decline of the Antarctic sea ice.

  19. Shearwater foraging in the Southern Ocean: the roles of prey availability and winds.

    Directory of Open Access Journals (Sweden)

    Ben Raymond

    Full Text Available BACKGROUND: Sooty (Puffinus griseus and short-tailed (P. tenuirostris shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. METHODOLOGY/PRINCIPAL FINDINGS: Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140 degrees E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters. CONCLUSIONS/SIGNIFICANCE: The shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem.

  20. Southern Ocean overturning, export production and climate variability over the past 1 Myr

    Science.gov (United States)

    Jaccard, S.; Hayes, C. T.; Martinez Garcia, A.; Galbraith, E. D.; Anderson, R. F.; Sigman, D. M.; Haug, G. H.

    2011-12-01

    Recently developed XRF core-scanning methods permit paleoceanographic reconstructions on time-scales similar to ice core temperature and atmospheric carbon dioxide measurements. We have investigated distribution of carbonate and biogenic barium (bioBa) - a proxy for integrated organic carbon export - in a sedimentary archive retrieved from the deep South Atlantic (ODP 1094, 53°S, 6°E, 2807 m) covering the past 1 Myr. These measurements are complemented with high-resolution, 230Th-normalized opal, bioBa and chlorin flux determinations spanning the last 150 kyrs. Our multi-proxy approach reveals that export production and biogenic carbonate preservation were tightly linked to atmospheric pCO2 reconstructions over the last 1 Myr. In particular, lukewarm interglacials (i.e. MIS 13-19) show generally lower organic matter export and reduced carbonate preservation when compared to more recent interglacials. This supports the critical contribution of Southern Ocean deglacial upwelling to modulate the partitioning of CO2 between the ocean interior and the atmosphere over the last million years, and immediately suggests that the moderate pCO2 increases during the lukewarm interglacials were due to a reduced dynamic range of Southern Ocean overturning. Changes in the vertical structure of the Southern Ocean water-column do not only prove to be crucial for the transitions from glacial to interglacial climate states. The decrease in upwelling following peak interglacial conditions leads the climate system to progressively converge towards colder, glacial conditions. Once a pCO2 threshold value of about 225 ppmv is reached, export production tends to stabilize around very low values, consistent with more strongly stratified conditions. This threshold also marks the abrupt inception of iron-rich mineral dust generation and deposition downwind of major South American dust sources, thereby catalyzing export production in the Subantarctic Zone of the Southern Ocean, to the north

  1. A euxinic southern North Atlantic Ocean during the Cenomanian/Turonian oceanic anoxic event

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Koster, J.

    1998-01-01

    During mid-Cretaceous times large amounts of organic carbon (Corg) became sequestered in black shales', possibly due to oceanic anoxic events' characterized by the development of an extended oxygen minimum zone (OMZ). Here, we provide the first direct evidence for an open ocean OMZ in the

  2. More losers than winners in a century of future Southern Ocean seafloor warming

    Science.gov (United States)

    Griffiths, Huw J.; Meijers, Andrew J. S.; Bracegirdle, Thomas J.

    2017-10-01

    The waters of the Southern Ocean are projected to warm over the coming century, with potential adverse consequences for native cold-adapted organisms. Warming waters have caused temperate marine species to shift their ranges poleward. The seafloor animals of the Southern Ocean shelf have long been isolated by the deep ocean surrounding Antarctica and the Antarctic Circumpolar Current, with little scope for southward migration. How these largely endemic species will react to future projected warming is unknown. By considering 963 invertebrate species, we show that within the current century, warming temperatures alone are unlikely to result in wholesale extinction or invasion affecting Antarctic seafloor life. However, 79% of Antarctica's endemic species do face a significant reduction in suitable temperature habitat (an average 12% reduction). Our findings highlight the species and regions most likely to respond significantly (negatively and positively) to warming and have important implications for future management of the region.

  3. Observing System Simulation Experiments for an array of autonomous biogeochemical profiling floats in the Southern Ocean

    Science.gov (United States)

    Kamenkovich, Igor; Haza, Angelique; Gray, Alison R.; Dufour, Carolina O.; Garraffo, Zulema

    2017-09-01

    This study uses Observing System Simulation Experiments (OSSEs) to examine the reconstruction of biogeochemical variables in the Southern Ocean from an array of autonomous profiling floats. In these OSSEs, designed to be relevant to the Southern Ocean Carbon and Climate Observation and Modeling (SOCCOM) project, the simulated floats move with oceanic currents and sample dissolved oxygen and inorganic carbon. The annual mean and seasonal cycle of these fields are then reconstructed and compared to the original model fields. The reconstruction skill is quantified with the reconstruction error (RErr), defined as the difference between the reconstructed and actual model fields, weighted by a local measure of the spatiotemporal variability. The square of the RErr is small (exception of the seasonal cycle in parts of the Indo-Atlantic, and that doubling this number to 300 results in a very modest increase in the reconstruction skill for dissolved oxygen.

  4. Closing history of the southern Tianshan oceanic basin, western China: an oblique collisional orogeny

    Science.gov (United States)

    Chen, Chuming; Lu, Huafu; Jia, Dong; Cai, Dongsheng; Wu, Shimin

    1999-02-01

    The Tianshan (Tien Shan) Range is an important Paleozoic collisional orogenic belt and the key to understand the central Asia tectonic evolution. This paper integrates our research results with the existing Chinese and international literature on sedimentology, geochemistry, isotopic geochronology, paleontonology and paleomagnetism of the Tianshan and Tarim regions to propose that the oblique collision may have played an important role in the late Paleozoic closing of the southern Tianshan oceanic basin. As a result of the Sinian (latest Proterozoic, younger than 800 Ma) continental extension and rifting process, the Tarim and Yili blocks separated from their parent continent in the Late Cambrian-Ordovician. The southern Tianshan oceanic crusts between the two blocks subducted northward beneath the southern margin of the Yili block in the Silurian. During the Devonian-Early Carboniferous, the Tarim block rapidly drifted to the north and rotated about 46° clockwise. This process induced the collision of the Yili micro-continent with the eastern segment (present geographical position) of the Tarim continent in the Late Devonian, and the southern Tianshan oceanic crust evolved to be a west-facing remnant oceanic basin. During the Late Carboniferous-Early Permian, the Tarim block, located within an almost constant latitude range, rotated about 26° clockwise with respect to the Yili micro-continent, which ultimately closed the remnant oceanic basin in a `scissors-like' manner from east to west and completed the Tarim-Yili collision. Subsequent A-type subduction of the Tarim continental crust and lithosphere-scale sinistral shearing generated a magmatic arc on the southern margin of the Tarim-Yili suture zone. The Late Permian-Early Triassic clastics deposited in a peripheral foreland basin developed above the arc.

  5. Climate-mediated changes to mixed-layer properties in the Southern Ocean: assessing the phytoplankton response

    Directory of Open Access Journals (Sweden)

    P. W. Boyd

    2008-05-01

    Full Text Available Concurrent changes in ocean chemical and physical properties influence phytoplankton dynamics via alterations in carbonate chemistry, nutrient and trace metal inventories and upper ocean light environment. Using a fully coupled, global carbon-climate model (Climate System Model 1.4-carbon, we quantify anthropogenic climate change relative to the background natural interannual variability for the Southern Ocean over the period 2000 and 2100. Model results are interpreted using our understanding of the environmental control of phytoplankton growth rates – leading to two major findings. Firstly, comparison with results from phytoplankton perturbation experiments, in which environmental properties have been altered for key species (e.g., bloom formers, indicates that the predicted rates of change in oceanic properties over the next few decades are too subtle to be represented experimentally at present. Secondly, the rate of secular climate change will not exceed background natural variability, on seasonal to interannual time-scales, for at least several decades – which may not provide the prevailing conditions of change, i.e. constancy, needed for phytoplankton adaptation. Taken together, the relatively subtle environmental changes, due to climate change, may result in adaptation by resident phytoplankton, but not for several decades due to the confounding effects of climate variability. This presents major challenges for the detection and attribution of climate change effects on Southern Ocean phytoplankton. We advocate the development of multi-faceted tests/metrics that will reflect the relative plasticity of different phytoplankton functional groups and/or species to respond to changing ocean conditions.

  6. The next generation of iron fertilization experiments in the Southern Ocean.

    Science.gov (United States)

    Smetacek, V; Naqvi, S W A

    2008-11-13

    Of the various macro-engineering schemes proposed to mitigate global warming, ocean iron fertilization (OIF) is one that could be started at short notice on relevant scales. It is based on the reasoning that adding trace amounts of iron to iron-limited phytoplankton of the Southern Ocean will lead to blooms, mass sinking of organic matter and ultimately sequestration of significant amounts of atmospheric carbon dioxide (CO2) in the deep sea and sediments. This iron hypothesis, proposed by John Martin in 1990 (Martin 1990 Paleoceanography 5, 1-13), has been tested by five mesoscale experiments that provided strong support for its first condition: stimulation of a diatom bloom accompanied by significant CO2 drawdown. Nevertheless, a number of arguments pertaining to the fate of bloom biomass, the ratio of iron added to carbon sequestered and various side effects of fertilization, continue to cast doubt on its efficacy. The idea is also unpopular with the public because it is perceived as meddling with nature. However, this apparent consensus against OIF is premature because none of the published experiments were specifically designed to test its second condition pertaining to the fate of iron-induced organic carbon. Furthermore, the arguments on side effects are based on worst-case scenarios. These doubts, formulated as hypotheses, need to be tested in the next generation of OIF experiments. We argue that such experiments, if carried out at appropriate scales and localities, will not only show whether the technique will work, but will also reveal a wealth of insights on the structure and functioning of pelagic ecosystems in general and the krill-based Southern Ocean ecosystem, in particular. The outcomes of current models on the efficacy and side effects of OIF differ widely, so data from adequately designed experiments are urgently needed for realistic parametrization. OIF is likely to boost zooplankton stocks, including krill, which could have a positive effect on

  7. A unified history of the ocean around southern Africa

    Science.gov (United States)

    Reeves, Colin; Master, Sharad

    2010-05-01

    The movement with respect to Africa of the hotspot marked by present-day Bouvet island is extrapolated backward in time to a position in the Lower Limpopo Valley at the time of the Karoo-Ferrar basalt event (183 Ma). In a tight reconstruction of the Precambrian fragments of Gondwana at this time, the triangular gap that remains between South Africa's Precambrian, that of Dronning Maud Land, Antarctica, and the eastward-extrapolated front of the Cape Fold Belt we fill with the Precambrian fragments of South Patagonia and the Falkland Islands. We postulate that the 183 Ma mantle upwelling produced a triple junction-type fracture marked by the alignments of the Lebombo, the SE margin of the Zimbabwe craton and the giant Botswana dyke swarm (178 Ma) that was rather quickly followed by the expulsion of the South Patagonia terranes from the Gondwana assembly along the alignment of the Falklands-Agulhas Fault Zone (FAFZ) as a transform margin. The space created was filled with igneous material akin to the present day Afar triangle. The magma supply generated not only oceanic crust but also overlying igneous deposits, much probably erupted subaerially. These developed progressively into the Falklands Plateau, the Mozambique Plains, the Mozambique Rise and the Explora Wedge of Antarctica. Not until the early Cretaceous did the growth of normal ocean crust start to exceed the ability of the declining mantle plume to cover the new ocean crust in a confined space with subaerial deposits that substantially thickened otherwise ‘oceanic' crust. When Antarctica and Africa began to separate before about 167 Ma, the future Mozambique Rise moved with Antarctica until, at about 125 Ma, a modest ridge reorganization east of Africa left Madagascar and the Mozambique Rise as part of the Africa Plate. An increasing westerly component to the movement of Antarctica against Africa preceded the initial opening of the South Atlantic and the fusing of the South Patagonia terranes with the

  8. Glacial to Holocene detrital flux and sediment provenance variations in the South Atlantic Southern Ocean

    Science.gov (United States)

    Noble, T. L.; Piotrowski, A. M.; Robinson, L. F.; McManus, J. F.

    2009-12-01

    Reconstructing input fluxes of detrital silicate material to the ocean through time provides insight into past atmospheric and ocean circulation pathways as well as the interaction between terrestrial and marine biogeochemical systems. The pathway of detrital input to the ocean can occur by a variety of mechanisms including riverine, aeolian, and ice rafting. Its provenance and flux may vary temporally. Constraining these inputs to the Southern Ocean is particularly important because productivity is limited by the lack of essential micronutrients such as Fe that are supplied by detritus. In this study we have combined 230Th-normalised detrital and mass fluxes with Pb, Nd and Sr isotope data measured on the silicate detrital phase as a tracer of sediment provenance to the Atlantic Sector of the Southern Ocean. The data presented compares the Last Glacial Maximum to the Holocene, from a transect of core sites that span the Subtropical Front in the north to the Southern Antarctic Polar Front. The latitudinal transect for the Holocene shows clearly defined sediment provinces that grade from predominately cratonic-derived-sediment at the northern sites, to a greater proportion of sediment with a mantle-derived chemical signature in the south. The northern signal is identified as silicate detritus sourced from southern Africa and a sediment component that may be derived from the North Atlantic. The sediment at the southern sites is derived primarily from the Scotia arc. The detrital flux decreases with distance away from the African continent towards Antarctica. Thus the Holocene pattern of sediment flux and provenance matches the known sediment source pathways and oceanic circulation in this region. The glacial flux and provenance is significantly different to the modern. There is no systematic pattern in the glacial detrital flux, unlike during the Holocene. In the northern sites, the detrital flux is similar to the Holocene at the shallower site (2000 mbsl), but

  9. Diatom resting spore ecology drives enhanced carbon export from a naturally iron-fertilized bloom in the Southern Ocean

    Science.gov (United States)

    Salter, Ian; Kemp, Alan E. S.; Moore, C. Mark; Lampitt, Richard S.; Wolff, George A.; Holtvoeth, Jens

    2012-03-01

    Southern Ocean Island systems sustain phytoplankton blooms induced by natural iron fertilization that are important for the uptake of atmospheric carbon dioxide and serve as analogues for past and future climate change. We present data on diatom flux assemblages and the biogeochemical properties of sinking particles to explain the enhanced particulate organic carbon (POC) export fluxes observed in response to natural iron supply in the Crozet Islands region (CROZeX). Moored deep-ocean sediment traps (>2000 m) were located beneath a naturally fertilized island bloom and beneath an adjacent High Nutrient Low Chlorophyll (HNLC) control site. Deep-ocean carbon flux from the naturally-fertilized bloom area was tightly correlated (R = 0.83, n = 12, P fertilized bloom enhanced carbon flux and the resulting Si/C and Si/N ratios were 2.0-3.4-fold and 2.2-3.5-fold lower than those measured in the adjacent HNLC control area. The enhanced carbon export and distinctive stoichiometry observed in naturally fertilized systems is therefore largely not attributable to iron relief of open ocean diatoms, but rather to the advection and growth of diatom species characteristic of island systems and the subsequent flux of resting spores. Carbon export estimates from current natural iron fertilization studies therefore represent a highly specific response of the island systems chosen as natural laboratories and may not be appropriate analogues for the larger Southern Ocean response. The broader implications of our results emphasize the role of phytoplankton diversity and ecology and highlight the need for a species-centered approach in order to understand the regulation of biogeochemical fluxes.

  10. Developing an enhanced tropical cyclone data portal for the Southern Hemisphere and the Western Pacific Ocean

    Science.gov (United States)

    Kuleshov, Yuriy; de Wit, Roald; Atalifo, Terry; Prakash, Bipendra; Waqaicelua, Alipate; Kunitsugu, Masashi; Caroff, Philippe; Chane-Ming, Fabrice

    2013-04-01

    Tropical cyclones are the most extreme weather phenomena which severely impact coastal communities and island nations. There is an ongoing research (i) on accurate analysis of observed trends in tropical cyclone occurrences, and (ii) how tropical cyclone frequency and intensity may change in the future as a result of climate change. Reliable historical records of cyclone activity are vital for this research. The Pacific Australia Climate Change Science and Adaptation Planning (PACCSAP) program is dedicated to help Pacific Island countries and Timor Leste gain a better understanding of how climate change will impact their regions. One of the key PACCSAP projects is focused on developing a tropical cyclone archive, climatology and seasonal prediction for the regions. As part of the project, historical tropical cyclone best track data have been examined and prepared to be subsequently displayed through the enhanced tropical cyclone data portal for the Southern Hemisphere and the Western Pacific Ocean. Data from the Regional Specialised Meteorological Centre (RSMC) Nadi, Fiji and Tropical Cyclone Warning Centres (TCWCs) in Brisbane, Darwin and Wellington for 1969-1970 to 2010-2011 tropical cyclone seasons have been carefully examined. Errors and inconsistencies which have been found during the quality control procedure have been corrected. To produce a consolidated data set for the South Pacific Ocean, best track data from these four centres have been used. Specifically, for 1969-1970 to 1994-1995 tropical cyclone seasons, data from TCWCs in Brisbane, Darwin and Wellington have been used. In 1995, RSMC Nadi, Fiji has been established with responsibilities for issuing tropical cyclone warnings and preparing best track data for the area south of the equator to 25°S, 160°E to 120°W. Consequently, data from RSMC Nadi have been used as a primary source for this area, starting from the 1995-1996 tropical cyclone season. These data have been combined with the data from

  11. Observed southern upper-ocean warming over 2005-2014 and associated mechanisms

    Science.gov (United States)

    Llovel, William; Terray, Laurent

    2016-12-01

    The climate system is gaining heat owing to increasing concentration of greenhouse gases due to human activities. As the world’s oceans are the dominant reservoir of heat in the climate system, an accurate estimation of the ocean heat content change is essential to quantify the Earth’s energy budget and global mean sea level rise. Based on the mean estimate of the three Argo gridded products considered, we provide a decadal ocean heat content estimate (over 2005-2014), down to 2000 m, of 0.76 ± 0.14 W m-2 and its spatial pattern since 2005 with unprecedented data coverage. We find that the southern hemisphere explains 90% of the net ocean heat uptake located around 40°S mainly for the Indian and Pacific oceans that corresponds to the center of their subtropical gyres. We find that this rapid upper ocean warming is linked to a poleward shift of mean wind stress curl enhancing Ekman pumping for the 45°S-60°S band. Therefore, the increase of Ekman pumping steepens the isopycnal surface and can enhance heat penetration into the deeper layers of the ocean. We also highlight a relative consistency between the year-to-year net top-of-the-atmosphere flux inferred by satellite measurements and the ocean heating rates (correlation coefficient of 0.53). We conclude that there is no strong evidence of missing energy in the climate system because of remaining large uncertainties in the observing system.

  12. Wind increase over cooling Southern Ocean driven by tropical warming and polar ozone hole

    Science.gov (United States)

    Schneider, D. P.; Fan, T.; Deser, C.

    2014-12-01

    Changing winds over the Southern Ocean have had dramatic impacts on Antarctic sea ice extent, anthropogenic heat and carbon uptake by the ocean, and the contribution of the Antarctic ice sheet to global sea level rise. An overall intensification of the surface westerly winds has been attributed to several different forcings, including stratospheric ozone depletion, greenhouse gasses, and tropical sea surface temperatures (SSTs). However, the relative roles of these drivers have not been well quantified. Reconciling previous explanations, here we show that a combination of tropical SSTs and stratospheric ozone loss largely explains the magnitude, regional patterns, and seasonality of observed lower tropospheric zonal wind trends over the Southern Ocean. We evaluate multiple ensembles of atmospheric model simulations, with each ensemble forced by one or a combination of drivers. Considering all months of the year, tropical SSTs are the largest contributor to observed zonal wind trends over 40°S-80°S. In austral summer, tropical SSTs and stratospheric ozone loss have contributed approximately equally to near-surface wind trends. The tropical contribution in austral summer is associated with tropics-wide warming, which has been moderated in recent decades by a prevalence of La-Niña events. The relative phasing of natural variability with anthropogenic forcing is therefore essential for understanding and predicting Southern Ocean climate change.

  13. Investigation on mechanisms controlling export production at the LGM with an biogeochemical ocean model

    Science.gov (United States)

    Oka, A.; Abe-Ouchi, A.; Chikamoto, M.; Ide, T.

    2012-04-01

    Using a biogeochemical ocean model that includes the iron cycle, we carry out preindustrial (control, CTL) and glacial (Last Glacial Maximum, LGM) climate simulations and investigate difference in export production (EP) between CTL and LGM. The model successfully reproduces general trends of a paleoclimate reconstruction of EP at the LGM except over the Atlantic Ocean. By conducting a series of sensitivity simulations, we investigate the mechanism controlling EP at the LGM in each basin. In the Southern Ocean, the model successfully reproduces the dipole pattern of the paleo reconstruction: the higher-latitude decrease and lower-latitude increase of EP. It is found that the lower-latitude increase of EP comes from iron fertilization effects by enhanced dust deposition, while the higher-latitude decrease of EP is caused by the reduction of surface shortwave due to spreading of sea ice there. We also find that increased dust input in other basins remotely affects EP in the Southern Ocean. In the Atlantic Ocean where the model fails to reproduce the paleo reconstruction, it is demonstrated that the response of EP in the Atlantic Ocean is strongly affected by distribution of iron limitation in a control climate. It is implied that the accurate evaluation of iron limitation in the present ocean is critical for evaluating changes in EP and associated reduction of atmospheric CO2 concentration at the LGM.

  14. Physical and chemical data collected from bottle casts in the Pacific Ocean and the Southern Oceans from ALBA and other platforms from 18 November 1962 to 04 May 1990 (NODC Accession 0000413)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical and chemical data were collected using bottle casts in the Pacific Ocean and the Southern Oceans from ALBA, LIRA, TAMGA and other platforms from 18 November...

  15. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from DISCOVERY in the Indian Ocean and Southern Oceans from 1994-02-19 to 1994-03-30 (NCEI Accession 0144242)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144242 includes discrete sample and profile data collected from DISCOVERY in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  16. Silicon pool dynamics and biogenic silica export in the Southern Ocean inferred from Si-isotopes

    Directory of Open Access Journals (Sweden)

    F. Fripiat

    2011-09-01

    Full Text Available Silicon isotopic signatures (δ30Si of water column silicic acid (Si(OH4 were measured in the Southern Ocean, along a meridional transect from South Africa (Subtropical Zone down to 57° S (northern Weddell Gyre. This provides the first reported data of a summer transect across the whole Antarctic Circumpolar Current (ACC. δ30Si variations are large in the upper 1000 m, reflecting the effect of the silica pump superimposed upon meridional water transfer across the ACC: the transport of Antarctic surface waters northward by a net Ekman drift and their convergence and mixing with warmer upper-ocean Si-depleted waters to the north. Using Si isotopic signatures, we determine different mixing interfaces: the Antarctic Surface Water (AASW, the Antarctic Intermediate Water (AAIW, and thermoclines in the low latitude areas. The residual silicic acid concentrations of end-members control the δ30Si alteration of the mixing products and with the exception of AASW, all mixing interfaces have a highly Si-depleted mixed layer end-member. These processes deplete the silicic acid AASW concentration northward, across the different interfaces, without significantly changing the AASW δ30Si composition. By comparing our new results with a previous study in the Australian sector we show that during the circumpolar transport of the ACC eastward, the δ30Si composition of the silicic acid pools is getting slightly, but significantly lighter from the Atlantic to the Australian sectors. This results either from the dissolution of biogenic silica in the deeper layers and/or from an isopycnal mixing with the deep water masses in the different oceanic basins: North Atlantic Deep Water in the Atlantic, and Indian Ocean deep water in the Indo-Australian sector. This isotopic trend is further transmitted to the subsurface waters, representing mixing interfaces between the surface and deeper layers.

  17. The role of zooplankton in the pelagic-benthic coupling of the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Sigrid B. Schnack-Schiel

    2005-12-01

    depths resuspended aggregates and single particles from shallow environments may constitute a considerable fraction of the “fresh” biogenic flux. Submarine canyons accelerate and cause more efficient transfer of energy to the deep-sea benthos. Both faecal pellets and aggregation increase the original sinking velocity of individual particles and reduce their residence time in the water column, thus creating rich organic mats over the seabed in shallow environments. In the Southern Ocean these rapid organic matter transfers are important since they allow the accumulation of highly nutritive material, which may fuel the benthos during the dark months due to constant resuspension by tidal currents. Several factors control the particle fluxes in the Southern Ocean, such as size and composition of phytoplankton blooms, currents, seasonality, depth, and ice coverage. Due to this complexity, despite many efforts there is still a long way to go before the pathway of this ecologically important link can be fully understood and described. Our knowledge of the pelagic-benthic coupling in the Magellan region is still extremely limited and offers many opportunities for future scientific research. The same holds true for the production of meroplanktonic larvae in the Southern Ocean.

  18. Planktonic foraminiferal biogeography in the Indian sector of the Southern Ocean: Contribution from CPR data

    Science.gov (United States)

    Meilland, Julie; Fabri-Ruiz, Salomé; Koubbi, Philippe; Monaco, Claire Lo; Cotte, Cédric; Hosie, Graham W.; Sanchez, Sophie; Howa, Hélène

    2016-04-01

    Within the framework of the Scientific Committee on Antarctic Research (SCAR) Southern Ocean-Continuous Plankton Recorder (SO-CPR) Survey, the oceanic regions around Crozet and Kerguelen Islands were investigated in February-March 2013. Living planktonic Foraminifera (LPF) were collected in the upper mixed layer with a CPR along a 2160 nautical mile sea transect that crossed main hydrological fronts in the Indian sector of the Southern Ocean. In the SO-CPR database, mean total abundances of Foraminifera occurring during late austral summer are highly variable at an inter-annual scale, from 10 to 250 ind.m-3, representing 10-40% of the total zooplankton abundance, respectively. In the Southern Ocean, major inter-annual changes in zooplankton community structure were already reported. In this study, we describe the large scale distributional pattern of individual planktonic foraminiferal species living in near-surface waters of the Indian sector of the Southern Ocean, and we attempt to explain why major spatial variability in relative species abundances occurs during a late austral summer. In February-March 2013, LPF total abundances recorded between 42.86°S and 56.42°S ranged from 0 to a maximum of 258 ind.m-3. In the Open Ocean Zone, the LPF community was composed of four major species (Globigerinita uvula, Neogloboquadrina pachyderma, Neogloboquadrina incompta, Globigerina bulloides). Generally, LPF total abundances are supposed to mirror primary production induced by hydrological fronts or induced by topography near Crozet and Kerguelen Islands. However, during late austral summer 2013, high foraminiferal abundances in the upper mixed layer did not always match the pattern of near-surface primary production (high Chl-a concentration areas delineated from satellite imagery). Low LPF standing stocks in late austral summer in the Southern Ocean contrasted with the presence of high densities of heavily silicified diatoms. This suggests that the late bloom

  19. Side effects and accounting aspects of hypothetical large-scale Southern Ocean iron fertilization

    Directory of Open Access Journals (Sweden)

    A. Oschlies

    2010-12-01

    Full Text Available Recent suggestions to slow down the increase in atmospheric carbon dioxide have included ocean fertilization by addition of the micronutrient iron to Southern Ocean surface waters, where a number of natural and artificial iron fertilization experiments have shown that low ambient iron concentrations limit phytoplankton growth. Using a coupled carbon-climate model with the marine biology's response to iron addition calibrated against data from natural iron fertilization experiments, we examine biogeochemical side effects of a hypothetical large-scale Southern Ocean Iron Fertilization (OIF that need to be considered when attempting to account for possible OIF-induced carbon offsets. In agreement with earlier studies our model simulates an OIF-induced increase in local air-sea CO2 fluxes by about 73 GtC over a 100-year period, which amounts to about 48% of the OIF-induced increase in organic carbon export out of the fertilized area. Offsetting CO2 return fluxes outside the region and after stopping the fertilization at 1, 7, 10, 50, and 100 years are quantified for a typical accounting period of 100 years. For continuous Southern Ocean iron fertilization, the CO2 return flux outside the fertilized area cancels about 20% of the fertilization-induced CO2 air-sea flux within the fertilized area on a 100-yr timescale. This "leakage" effect has a radiative impact more than twice as large as the simulated enhancement of marine N2O emissions. Other side effects not yet discussed in terms of accounting schemes include a decrease in Southern Ocean oxygen levels and a simultaneous shrinking of tropical suboxic areas, and accelerated ocean acidification in the entire water column in the Southern Ocean at the expense of reduced globally-averaged surface-water acidification. A prudent approach to account for the OIF-induced carbon sequestration would account for global air-sea CO2 fluxes rather

  20. Side effects and accounting aspects of hypothetical large-scale Southern Ocean iron fertilization

    Science.gov (United States)

    Oschlies, A.; Koeve, W.; Rickels, W.; Rehdanz, K.

    2010-12-01

    Recent suggestions to slow down the increase in atmospheric carbon dioxide have included ocean fertilization by addition of the micronutrient iron to Southern Ocean surface waters, where a number of natural and artificial iron fertilization experiments have shown that low ambient iron concentrations limit phytoplankton growth. Using a coupled carbon-climate model with the marine biology's response to iron addition calibrated against data from natural iron fertilization experiments, we examine biogeochemical side effects of a hypothetical large-scale Southern Ocean Iron Fertilization (OIF) that need to be considered when attempting to account for possible OIF-induced carbon offsets. In agreement with earlier studies our model simulates an OIF-induced increase in local air-sea CO2 fluxes by about 73 GtC over a 100-year period, which amounts to about 48% of the OIF-induced increase in organic carbon export out of the fertilized area. Offsetting CO2 return fluxes outside the region and after stopping the fertilization at 1, 7, 10, 50, and 100 years are quantified for a typical accounting period of 100 years. For continuous Southern Ocean iron fertilization, the CO2 return flux outside the fertilized area cancels about 20% of the fertilization-induced CO2 air-sea flux within the fertilized area on a 100-yr timescale. This "leakage" effect has a radiative impact more than twice as large as the simulated enhancement of marine N2O emissions. Other side effects not yet discussed in terms of accounting schemes include a decrease in Southern Ocean oxygen levels and a simultaneous shrinking of tropical suboxic areas, and accelerated ocean acidification in the entire water column in the Southern Ocean at the expense of reduced globally-averaged surface-water acidification. A prudent approach to account for the OIF-induced carbon sequestration would account for global air-sea CO2 fluxes rather than for local fluxes into the fertilized area only. However, according to our model

  1. Holocene Southern Ocean surface temperature variability west of the Antarctic Peninsula.

    Science.gov (United States)

    Shevenell, A E; Ingalls, A E; Domack, E W; Kelly, C

    2011-02-10

    The disintegration of ice shelves, reduced sea-ice and glacier extent, and shifting ecological zones observed around Antarctica highlight the impact of recent atmospheric and oceanic warming on the cryosphere. Observations and models suggest that oceanic and atmospheric temperature variations at Antarctica's margins affect global cryosphere stability, ocean circulation, sea levels and carbon cycling. In particular, recent climate changes on the Antarctic Peninsula have been dramatic, yet the Holocene climate variability of this region is largely unknown, limiting our ability to evaluate ongoing changes within the context of historical variability and underlying forcing mechanisms. Here we show that surface ocean temperatures at the continental margin of the western Antarctic Peninsula cooled by 3-4 °C over the past 12,000 years, tracking the Holocene decline of local (65° S) spring insolation. Our results, based on TEX(86) sea surface temperature (SST) proxy evidence from a marine sediment core, indicate the importance of regional summer duration as a driver of Antarctic seasonal sea-ice fluctuations. On millennial timescales, abrupt SST fluctuations of 2-4 °C coincide with globally recognized climate variability. Similarities between our SSTs, Southern Hemisphere westerly wind reconstructions and El Niño/Southern Oscillation variability indicate that present climate teleconnections between the tropical Pacific Ocean and the western Antarctic Peninsula strengthened late in the Holocene epoch. We conclude that during the Holocene, Southern Ocean temperatures at the western Antarctic Peninsula margin were tied to changes in the position of the westerlies, which have a critical role in global carbon cycling.

  2. Spatial distributions of Southern Ocean mesozooplankton communities have been resilient to long-term surface warming.

    Science.gov (United States)

    Tarling, Geraint A; Ward, Peter; Thorpe, Sally E

    2018-01-01

    The biogeographic response of oceanic planktonic communities to climatic change has a large influence on the future stability of marine food webs and the functioning of global biogeochemical cycles. Temperature plays a pivotal role in determining the distribution of these communities and ocean warming has the potential to cause major distributional shifts, particularly in polar regions where the thermal envelope is narrow. We considered the impact of long-term ocean warming on the spatial distribution of Southern Ocean mesozooplankton communities through examining plankton abundance in relation to sea surface temperature between two distinct periods, separated by around 60 years. Analyses considered 16 dominant mesozooplankton taxa (in terms of biomass and abundance) in the southwest Atlantic sector of the Southern Ocean, from net samples and in situ temperature records collected during the Discovery Investigations (1926-1938) and contemporary campaigns (1996-2013). Sea surface temperature was found to have increased significantly by 0.74°C between the two eras. The corresponding sea surface temperature at which community abundance peaked was also significantly higher in contemporary times, by 0.98°C. Spatial projections indicated that the geographical location of community peak abundance had remained the same between the two eras despite the poleward advance of sea surface isotherms. If the community had remained within the same thermal envelope as in the 1920s-1930s, community peak abundance would be 500 km further south in the contemporary era. Studies in the northern hemisphere have found that dominant taxa, such as calanoid copepods, have conserved their thermal niches and tracked surface isotherms polewards. The fact that this has not occurred in the Southern Ocean suggests that other selective pressures, particularly food availability and the properties of underlying water masses, place greater constraints on spatial distributions in this region. It

  3. Evolution of surface and deep water conditions in the Antarctic Southern Ocean across the MPT

    Science.gov (United States)

    Hasenfratz, A. P.; Jaccard, S.; Martinez-Garcia, A.; Hodell, D. A.; Vance, D.; Bernasconi, S. M.; Kleiven, H. F.; Haug, G. H.

    2016-12-01

    The mid-Pleistocene transition (MPT; 1.25-0.7 Myr) marked a fundamental change in the periodicity of the climate cycles, shifting from a 41-kyr to a high-amplitude, asymmetric 100-kyr cycle without any noticeable change in orbital forcing. Hypotheses to explain the MPT involve non-linear responses to orbital forcing, changes in glacial dynamics and internal changes in the carbon cycle. Specifically, a decrease in pCO2 during peak ice age conditions and the associated global cooling has been proposed as one of the possible triggers for the MPT. Previous results have indicated that the Southern Ocean provides a coherent two-part mechanism for the timing and amplitude of the glacial/interglacial pCO2 variations. However, there is still much uncertainty and debate regarding the response of the Antarctic Southern Ocean biogeochemistry to changes invoked for the MPT, and its contribution to the proposed pCO2 variations. Here, we show 1.5 Myr-long records of export production, and planktonic (Neogloboquadrina pachyderma) and benthic (Melonis pompilioides) foraminiferal stable isotopes and trace metals from ODP Site 1094 retrieved from the Atlantic sector of the Antarctic Southern Ocean (53.2°S, 5.1°E, 2807m). While glacial planktonic δ18O increases across the MPT, glacial Mg/Ca-derived SST decrease later, around 700 ka, when glacial atmospheric pCO2 has already dropped. As glacial export production that is crucially related to micronutrients upwelled from the subsurface ocean remains unchanged across the past 1.5 Myr, it seems that cooling of the glacial surface ocean did not significantly alter the stability of the water column. Furthermore, paired measurements of benthic δ18O and Mg/Ca enables the determination of seawater δ18O of the deep ocean, which allows us to estimate changes in the density gradient and the salinity of the deep water.

  4. The Impact of the Ozone Hole on the Temperature and Salinity of the Southern Ocean

    Science.gov (United States)

    Solomon, A. L.; Polvani, L. M.; Abernathey, R. P.; Smith, K. L.

    2016-02-01

    Observations have revealed systematic changes in the temperature and salinity of the Southern Ocean since 1960. These trends reflect the evolving exchange of heat and momentum between atmosphere and ocean and are, in part, driven by anthropogenic emissions. The key question is: which emissions are most important, greenhouse gases or ozone depleting substances? We answer this question using CESM-WACCM, a comprehensive climate model with interactive stratospheric chemistry, coupled to state-of-the-art land, ocean and sea-ice components. In accord with recent observations, the model reproduces the recent warming and freshening of the upper 1000m of the Southern Ocean. Furthermore, employing an ensemble of single forcing integrations allows us to attribute a third of the changes in temperature and salinity to the presence of a seasonal ozone hole. While the warming is caused by a local change in the surface energy budget, the trend in salinity results from a combination of melting sea-ice and changing ocean transport.

  5. Investigating the complex relationship between in situ Southern Ocean pCO2 and its ocean physics and biogeochemical drivers using a nonparametric regression approach

    CSIR Research Space (South Africa)

    Pretorius, W

    2014-01-01

    Full Text Available The objective in this paper is to investigate the use of a non-parametric model approach to model the relationship between oceanic carbon dioxide (pCO(sub2)) and a range of biogeochemical in situ variables in the Southern Ocean, which influence its...

  6. Studies on the nutrient distribution in the Southern Ocean waters along the 45 degrees E transect

    Digital Repository Service at National Institute of Oceanography (India)

    Rajakumar, A.; Alagarsamy, R.; Khare, N.; Saraswat, R.; Subramaniam, M.M.

    ) is located at approximately 42-43° S latitude in central south Indian Ocean4. _______________ 3Present address: Ministry of Earth Sciences, Block # 12, CGO Complex, Lodhi Road, New Delhi 110 003 India RAJKUMAR et al: NUTRIENT DISTRIBUTION...-103. 13 Nelson D M, DeMaster D J & Smith W O, Cycling of organic carbon and biogenic silica in the Southern Ocean: Estimates of water-column and sedimentary fluxes on the Ross Sea Continental Shelf, J. Geophy. Res., 101 (1996) 519-532. 14 Weisse T...

  7. King penguin population threatened by Southern Ocean warming.

    Science.gov (United States)

    Le Bohec, Céline; Durant, Joël M; Gauthier-Clerc, Michel; Stenseth, Nils C; Park, Young-Hyang; Pradel, Roger; Grémillet, David; Gendner, Jean-Paul; Le Maho, Yvon

    2008-02-19

    Seabirds are sensitive indicators of changes in marine ecosystems and might integrate and/or amplify the effects of climate forcing on lower levels in food chains. Current knowledge on the impact of climate changes on penguins is primarily based on Antarctic birds identified by using flipper bands. Although flipper bands have helped to answer many questions about penguin biology, they were shown in some penguin species to have a detrimental effect. Here, we present for a Subantarctic species, king penguin (Aptenodytes patagonicus), reliable results on the effect of climate on survival and breeding based on unbanded birds but instead marked by subcutaneous electronic tags. We show that warm events negatively affect both breeding success and adult survival of this seabird. However, the observed effect is complex because it affects penguins at several spatio/temporal levels. Breeding reveals an immediate response to forcing during warm phases of El Niño Southern Oscillation affecting food availability close to the colony. Conversely, adult survival decreases with a remote sea-surface temperature forcing (i.e., a 2-year lag warming taking place at the northern boundary of pack ice, their winter foraging place). We suggest that this time lag may be explained by the delay between the recruitment and abundance of their prey, adjusted to the particular 1-year breeding cycle of the king penguin. The derived population dynamic model suggests a 9% decline in adult survival for a 0.26 degrees C warming. Our findings suggest that king penguin populations are at heavy extinction risk under the current global warming predictions.

  8. Phytoplankton distribution and nitrogen dynamics in the southwest indian subtropical gyre and Southern Ocean waters

    Directory of Open Access Journals (Sweden)

    S. J. Thomalla

    2011-02-01

    Full Text Available During the 1999 Marion Island Oceanographic Survey (MIOS 4 in late austral summer, a northbound and reciprocal southbound transect were taken along the Southwest Indian and Madagascar Ridge, between the Prince Edward Islands and 31° S. The sections crossed a number of major fronts and smaller mesoscale features and covered a wide productivity spectrum from subtropical to subantarctic waters. Associated with the physical survey were measurements of size fractionated chlorophyll, nutrients and nitrogen (NO3, NH4 and urea uptake rates. Subtropical waters were characterised by low chlorophyll concentrations (max = 0.27.3 mg m−3 dominated by pico-phytoplankton cells (> 81% and very low f-ratios (< 0.1, indicative of productivity based almost entirely on recycled ammonium and urea. Micro-phytoplankton growth was limited by the availability of NO3 (< 0.5 mmol m−3 and Si(OH4 (< 1.5 mmol m−3 through strong vertical stratification preventing the upward flux of nutrients into the euphotic zone. Biomass accumulation of small cells was likely controlled by micro-zooplankton grazing. In subantarctic waters, total chlorophyll concentrations increased (max = 0.74 mg m−3 relative to the subtropical waters and larger cells became more prevalent, however smaller phytoplankton cells and low f-ratios (< 0.14 still dominated, despite sufficient NO3 availability. The results from this study favour Si(OH4 limitation, light-limited deep mixing and likely Fe deficiency as the dominant mechanisms controlling significant new production by micro-phytoplankton. The percentage of micro-phytoplankton cells and rates of new production did however increase at oceanic frontal regions (58.6% and 11.22%, respectively, and in the region of the Prince Edward archipelago (61.4% and 14.16%, respectively. Here, water column stabilization and local Fe-enrichment are

  9. Revision of Leucothoe (Amphipoda, Crustacea from the Southern Ocean: a cosmopolitanism concept is vanishing

    Directory of Open Access Journals (Sweden)

    Traudl Krapp-Schickel

    2014-04-01

    Full Text Available Among the 125 currently recognized species of the panoceanic genus Leucothoe, L. antarctica was described in 1888 from the Antarctic seas, but was soon synonymized with the so-called cosmopolitan Leucothoe spinicarpa Abildgaard, which was cited from the Southern Ocean about 70 times since this first record. After erecting a new Antarctic species again only in 1983, “morphological variants” were observed and discussed. In this paper, we revalidate the first defined Antarctic species (Leucothoe antarctica, redescribe the second one (L. orkneyi, describe 5 new Southern Ocean species (L. campbelli sp. nov., L. longimembris sp. nov., L. macquariae sp. nov., L. merletta sp. nov. and L. weddellensis sp. nov. and provide a key to all Antarctic and sub-Antarctic species.

  10. Southern Ocean deep-water carbon export enhanced by natural iron fertilization.

    Science.gov (United States)

    Pollard, Raymond T; Salter, Ian; Sanders, Richard J; Lucas, Mike I; Moore, C Mark; Mills, Rachel A; Statham, Peter J; Allen, John T; Baker, Alex R; Bakker, Dorothee C E; Charette, Matthew A; Fielding, Sophie; Fones, Gary R; French, Megan; Hickman, Anna E; Holland, Ross J; Hughes, J Alan; Jickells, Timothy D; Lampitt, Richard S; Morris, Paul J; Nédélec, Florence H; Nielsdóttir, Maria; Planquette, Hélène; Popova, Ekaterina E; Poulton, Alex J; Read, Jane F; Seeyave, Sophie; Smith, Tania; Stinchcombe, Mark; Taylor, Sarah; Thomalla, Sandy; Venables, Hugh J; Williamson, Robert; Zubkov, Mike V

    2009-01-29

    The addition of iron to high-nutrient, low-chlorophyll regions induces phytoplankton blooms that take up carbon. Carbon export from the surface layer and, in particular, the ability of the ocean and sediments to sequester carbon for many years remains, however, poorly quantified. Here we report data from the CROZEX experiment in the Southern Ocean, which was conducted to test the hypothesis that the observed north-south gradient in phytoplankton concentrations in the vicinity of the Crozet Islands is induced by natural iron fertilization that results in enhanced organic carbon flux to the deep ocean. We report annual particulate carbon fluxes out of the surface layer, at three kilometres below the ocean surface and to the ocean floor. We find that carbon fluxes from a highly productive, naturally iron-fertilized region of the sub-Antarctic Southern Ocean are two to three times larger than the carbon fluxes from an adjacent high-nutrient, low-chlorophyll area not fertilized by iron. Our findings support the hypothesis that increased iron supply to the glacial sub-Antarctic may have directly enhanced carbon export to the deep ocean. The CROZEX sequestration efficiency (the amount of carbon sequestered below the depth of winter mixing for a given iron supply) of 8,600 mol mol(-1) was 18 times greater than that of a phytoplankton bloom induced artificially by adding iron, but 77 times smaller than that of another bloom initiated, like CROZEX, by a natural supply of iron. Large losses of purposefully added iron can explain the lower efficiency of the induced bloom(6). The discrepancy between the blooms naturally supplied with iron may result in part from an underestimate of horizontal iron supply.

  11. Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    DEFF Research Database (Denmark)

    Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín

    2016-01-01

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global...... zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean....

  12. Environmental forcing and Southern Ocean marine predator populations: effects of climate change and variability.

    Science.gov (United States)

    Trathan, P N; Forcada, J; Murphy, E J

    2007-12-29

    The Southern Ocean is a major component within the global ocean and climate system and potentially the location where the most rapid climate change is most likely to happen, particularly in the high-latitude polar regions. In these regions, even small temperature changes can potentially lead to major environmental perturbations. Climate change is likely to be regional and may be expressed in various ways, including alterations to climate and weather patterns across a variety of time-scales that include changes to the long interdecadal background signals such as the development of the El Niño-Southern Oscillation (ENSO). Oscillating climate signals such as ENSO potentially provide a unique opportunity to explore how biological communities respond to change. This approach is based on the premise that biological responses to shorter-term sub-decadal climate variability signals are potentially the best predictor of biological responses over longer time-scales. Around the Southern Ocean, marine predator populations show periodicity in breeding performance and productivity, with relationships with the environment driven by physical forcing from the ENSO region in the Pacific. Wherever examined, these relationships are congruent with mid-trophic-level processes that are also correlated with environmental variability. The short-term changes to ecosystem structure and function observed during ENSO events herald potential long-term changes that may ensue following regional climate change. For example, in the South Atlantic, failure of Antarctic krill recruitment will inevitably foreshadow recruitment failures in a range of higher trophic-level marine predators. Where predator species are not able to accommodate by switching to other prey species, population-level changes will follow. The Southern Ocean, though oceanographically interconnected, is not a single ecosystem and different areas are dominated by different food webs. Where species occupy different positions in

  13. Atmospheric research in Southern Africa and Indian Ocean: a South Africa-France bilateral collaborative programme

    CSIR Research Space (South Africa)

    Sivakumar, V

    2009-09-01

    Full Text Available conference proceeding ATMOSPHERIC RESEARCH IN SOUTHERN AFRICA AND INDIAN OCEAN : A SOUTH AFRICA – FRANCE BILATERAL COLLABORATIVE PROGRAMME V. Sivakumar1,2 and R. Delmas3 1 South Africa Coordinator, Department of Geography, Geoinformatics..., Universite de la Reunion, Saint Denis, La Reunion, France. svenkataraman@csir.co.za 1. INTRODUCTION In the present context of global changes, atmospheric and climatic research should be more organized in the framework of international...

  14. A Roadmap for Antarctic and Southern Ocean Science for the Next Two Decades and Beyond

    Science.gov (United States)

    Kennicutt, M. C., II

    2015-12-01

    Abstract: Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to 'scan the horizon' to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone.

  15. An overview of Southern Ocean zooplankton data: abundance, biomass, feeding and functional relationships

    OpenAIRE

    Atkinson, Angus; Ward, Peter; Hunt, B.P.V.; Pakhomov, E.A.; Hosie,G.W.

    2012-01-01

    There is an enormous amount of data on Southern Ocean (SO) zooplankton, mostly on their distribution with a minority addressing rate processes. This review aims to summarise these data and show where it resides, to assist SO food-web modellers or those with limited specialist knowledge of SO zooplankton. First, a brief overview is provided of the diversity and basic biology of SO zooplankton, with an emphasis on abundance, distribution and feeding. Second, advice is provided on the uses, stre...

  16. Observations of high droplet number concentrations in Southern Ocean boundary layer clouds

    Directory of Open Access Journals (Sweden)

    T. Chubb

    2016-01-01

    Full Text Available Cloud physics data collected during the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER Pole-to-Pole Observations (HIPPO campaigns provide a snapshot of unusual wintertime microphysical conditions in the boundary layer over the Southern Ocean. On 29 June 2011, the HIAPER sampled the boundary layer in a region of pre-frontal warm air advection between 58 and 48° S to the south of Tasmania. Cloud droplet number concentrations were consistent with climatological values in the northernmost profiles but were exceptionally high for wintertime in the Southern Ocean at 100–200 cm−3 in the southernmost profiles. Sub-micron (0.06  < D <  1 µm aerosol concentrations for the southern profiles were up to 400 cm−3. Analysis of back trajectories and atmospheric chemistry observations revealed that while conditions in the troposphere were more typical of a clean remote ocean airmass, there was some evidence of continental or anthropogenic influence. However, the hypothesis of long-range transport of continental aerosol fails to explain the magnitude of the aerosol and cloud droplet concentration in the boundary layer. Instead, the gale force surface winds in this case (wind speed at 167 m above sea level was  > 25 m s−1 were most likely responsible for production of sea spray aerosol which influenced the microphysical properties of the boundary layer clouds. The smaller size and higher number concentration of cloud droplets is inferred to increase the albedo of these clouds, and these conditions occur regularly, and are expected to increase in frequency, over windy parts of the Southern Ocean.

  17. Rock Magnetic Record of the Middle Miocene Climatic Transition at ODP Site 747, Southern Ocean

    Science.gov (United States)

    Abrajevitch, A.; Roberts, A. P.; Kodama, K.

    2013-12-01

    ODP Site 747, located on the central Kerguelen Plateau, contains a compete record of the Middle Miocene Climatic Transition (MMCT) - a major cooling event that followed the warm mid-Miocene Climatic Optimum and culminated in an 'icehouse' climate regime. Because of its unusually well preserved and rich foraminiferal assemblages, the MMCT interval at Site 747 has been a focus of several high-resolution paleoclimatic studies that have effectively established this sequence as a reference for the Southern Ocean. Major changes in species abundances across the MMCT are conventionally interpreted to reflect changes in water temperature and salinity. Our XRF and rock magnetic study reveals a good correlation between terrigenous input (likely from local volcanic sources) and the abundances of the dominant planktonic foraminiferal species. Such a correlation suggests that nutrient flux (iron fertilization) played a significant role in controlling microplankton communities during the MMCT at Site 747. Concentration-dependent rock magnetic parameters appear to be a useful proxy for nutrient flux in this pelagic marine environment.

  18. Dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from POLARSTERN in the Indian Ocean, South Atlantic Ocean and Southern Oceans from 1996-03-17 to 1996-05-20 (NODC Accession 0116640)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0116640 includes discrete sample and profile data collected from POLARSTERN in the Indian Ocean, South Atlantic Ocean and Southern Oceans (> 60...

  19. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from DISCOVERY in the Indian Ocean, South Atlantic Ocean and Southern Oceans from 1993-02-06 to 1993-03-18 (NCEI Accession 0143944)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143944 includes discrete sample and profile data collected from DISCOVERY in the Indian Ocean, South Atlantic Ocean and Southern Oceans (> 60...

  20. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from AURORA AUSTRALIS in the Indian Ocean, South Pacific Ocean and Southern Oceans from 2011-01-04 to 2011-02-06 (NCEI Accession 0143947)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143947 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean, South Pacific Ocean and Southern Oceans (>...

  1. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from JAMES CLARK ROSS in the Indian Ocean, South Atlantic Ocean and Southern Oceans from 2008-12-26 to 2009-01-30 (NODC Accession 0110254)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0110254 includes discrete sample and profile data collected from JAMES CLARK ROSS in the Indian Ocean, South Atlantic Ocean and Southern Oceans (>...

  2. Partial pressure (or fugacity) of carbon dioxide, salinity and SEA SURFACE TEMPERATURE collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from ODEN in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2006-12-14 to 2006-12-26 (NODC Accession 0108159)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108159 includes Surface underway data collected from ODEN in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60 degrees...

  3. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from POLARSTERN in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2010-11-28 to 2011-02-05 (NODC Accession 0108155)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108155 includes discrete sample and profile data collected from POLARSTERN in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (>...

  4. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from RRS JAMES COOK in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2009-02-03 to 2009-03-03 (NODC Accession 0110379)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0110379 includes discrete sample and profile data collected from RRS JAMES COOK in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans...

  5. Dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from MIRAI in the Indian Ocean, South Pacific Ocean and Southern Oceans from 2012-11-28 to 2013-01-04 (NCEI Accession 0143950)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143950 includes discrete sample and profile data collected from MIRAI in the Indian Ocean, South Pacific Ocean and Southern Oceans (> 60 degrees...

  6. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, PAR Sensor and other instruments from AURORA AUSTRALIS in the Indian Ocean, South Pacific Ocean and Southern Oceans from 2007-12-16 to 2008-01-27 (NCEI Accession 0143932)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143932 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean, South Pacific Ocean and Southern Oceans (>...

  7. Meltwater Induced Changes in Micronutrient Availability and Productivity in the Southern Ocean During LGM

    Science.gov (United States)

    Jaccard, T.; Robinson, R. S.; Ariztegui, D.; Wilkinson, K. J.

    2008-12-01

    The Southern Ocean plays an important role in the CO2 air-sea balance and have regulated atmospheric CO2 concentrations over glacial-interglacial cycles. Increased productivity resulting from higher nutrient deposition over Antarctica could have contributed to lower the atmospheric CO2 content during ice ages. Although Fe-fertilization has been observed in waters of present Southern Ocean, there is still a lack of convincing evidence for such events in the past. Nutrients supply and consumption were reconstructed by analyzing the Zn incorporated in diatom frustules and diatom-bound δ 15N from sedimentary core RC13-259 from the Antarctic sector of the South Atlantic (54°S, 5°W). These data evidence for the first time a greater availability of westerlies-driven micronutrients to phytoplankton during the LGM. These changes in concert with higher nitrate consumption are resulting from massive meltwater discharge to the Southern Ocean. The widespread presence of meltwaters and free-drifting icebergs may have stimulated nutrient drawdown contributing in turn to the sequestration of CO2 during glacial times.

  8. Cytotoxic activity of marine sponge extracts from the sub-Antarctic Islands and the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Elisabeth K. Olsen

    2016-11-01

    Full Text Available Over the past 50 years, marine invertebrates, especially sponges, have proven to be a valuable source of new and/or bioactive natural products that have the potential to be further developed as lead compounds for pharmaceutical applications. Although marine benthic invertebrate communities occurring off the coast of South Africa have been explored for their biomedicinal potential, the natural product investigation of marine sponges from the sub-Antarctic Islands in the Southern Ocean for the presence of bioactive secondary metabolites has been relatively unexplored thus far. We report here the results for the biological screening of both aqueous and organic extracts prepared from nine specimens of eight species of marine sponges, collected from around Marion Island and the Prince Edward Islands in the Southern Ocean, for their cytotoxic activity against three cancer cell lines. The results obtained through this multidisciplinary collaborative research effort by exclusively South African institutions has provided an exciting opportunity to discover cytotoxic compounds from sub-Antarctic sponges, whilst contributing to our understanding of the biodiversity and geographic distributions of these cold-water invertebrates. Therefore, we acknowledge here the various contributions of the diverse scientific disciplines that played a pivotal role in providing the necessary platform for the future natural products chemistry investigation of these marine sponges from the sub- Antarctic Islands and the Southern Ocean.

  9. Southern Ocean ventilation and bottom water formation driven by Weddell Sea polynyas

    Science.gov (United States)

    Rheinlaender, Jonathan; Nisancioglu, Kerim; Smedsrud, Lars Henrik

    2017-04-01

    A distinct feature of the last glacial period, are the abrupt temperature fluctuations in Greenland associated with Dansgaard-Oeschger events and a similar but opposite response in Antarctica. The prevailing hypothesis behind this inter-hemispheric coupling, points to changes in deep water formation as the main driver, thus highlighting the pivotal role of the high latitude oceans in global climate. Bottom water formation through open-ocean deep convection in an Antarctic polynya, a large open water area inside the winter sea ice cover, provide a potential mechanism to trigger such changes in ocean circulation. In this study, an ocean-sea ice only version of the Norwegian Earth System Model (NorESM) is explored and shows strong open-ocean deep convection associated with large polynyas in the Weddell Sea. This provides us with an opportunity to test (1) how internal ocean dynamics can trigger abrupt changes in sea-ice cover and (2) how these polynyas affect the overturning circulation through changes in bottom water formation. During the 1,000 year long free-running simulation two polynyas are observed. We show, that the polynya is caused by subsurface warming leading to a gradual weakening of the surface stratification which destabilizes the whole water column and eventually triggers deep convective overturning. This mixes up relatively warm deep water causing extensive melt of sea ice in the Weddell Sea, while cold and fresh surface water sinks to the bottom. Consequently, the polynya leads to extensive bottom water formation and increase in the northward flow of Antarctic Bottom Water, while the southward flow of North Atlantic Deep Water is reduced. Finally, our results suggest that a decrease in the temperature of warm deep water in the Weddell Sea leads to cessation of open-ocean deep convection. This raises the question if open-ocean deep convection associated with polynyas in the Southern Ocean could be a realistic feature in a cold, glacial climate.

  10. Response of bacteria and phytoplankton from a subtropical front location Southern Ocean to micronutrient amendments ex-situ

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaiah, N.; Jain, A.; Meena, R.M.; Naik, R.K.; Verma, R.; Bhat, M.; Mesquita, A.; Nadkarni, A.; D`Souza, S.E.; Ahmed, T.; Bandekar, M.; Gomes, J.

    that the bacterial community composition in the 14    subarctic Pacific, the Southern Ocean, and the California coastal upwelling region scarcely changed after iron infusions, although their abundance and production increased. Arrieta et al. (2004) also reported...

  11. Tropical systems from the southwest Indian Ocean making landfall over the Limpopo River Basin, southern Africa: a historical perspective

    CSIR Research Space (South Africa)

    Malherbe, J

    2011-03-01

    Full Text Available The study provides perspective on the contribution of landfalling tropical systems (cyclones, depressions, storms and lows) from the southwest Indian Ocean (SWIO) towards rainfall over the eastern interior of southern Africa, over the period 1948...

  12. Photosynthetic Maximum Quantum Yield Increases Are an Essential Component of the Southern Ocean Phytoplankton Response to Iron

    National Research Council Canada - National Science Library

    Michael R. Hiscock; Veronica P. Lance; Amy M. Apprill; Robert R. Bidigare; Zackary I. Johnson; B. Greg Mitchell; Walker O. Smith; Richard T. Barber

    2008-01-01

    ... has not been clearly identified. The Southern Ocean iron enrichment experiment, an iron fertilization experiment in the waters closest to Antarctica, resulted in a 9-fold increase in chlorophyll (Chl...

  13. Evaluation of satellite and reanalysis wind products with in situ wave glider wind observations in the Southern Ocean

    CSIR Research Space (South Africa)

    Schmidt, KM

    2017-12-01

    Full Text Available Wave Glider (WG) deployments in the Southern Ocean with the intent to determine which blended satellite or reanalysis product best represents the magnitude and variability of the observed wind field. Results show that the ECMWF reanalysis product...

  14. Antarctic lakes suggest millennial reorganizations of Southern Hemisphere atmospheric and oceanic circulation.

    Science.gov (United States)

    Hall, Brenda L; Denton, George H; Fountain, Andrew G; Hendy, Chris H; Henderson, Gideon M

    2010-12-14

    The phasing of millennial-scale oscillations in Antarctica relative to those elsewhere in the world is important for discriminating among models for abrupt climate change, particularly those involving the Southern Ocean. However, records of millennial-scale variability from Antarctica dating to the last glacial maximum are rare and rely heavily on data from widely spaced ice cores, some of which show little variability through that time. Here, we present new data from closed-basin lakes in the Dry Valleys region of East Antarctica that show high-magnitude, high-frequency oscillations in surface level during the late Pleistocene synchronous with climate fluctuations elsewhere in the Southern Hemisphere. These data suggest a coherent Southern Hemisphere pattern of climate change on millennial time scales, at least in the Pacific sector, and indicate that any hypothesis concerning the origin of these events must account for synchronous changes in both high and temperate latitudes.

  15. Scatterometer-derived Southern Ocean mesoscale cyclone activity over the last decade

    Science.gov (United States)

    Irving, D.; Simmonds, I.; Keay, K.

    2010-08-01

    Mesoscale cyclones (or mesocyclones) play an important role in the weather and climate of the Southern Hemisphere (SH) mid-to-high latitudes. However, the relatively small size and short lifetime of these systems, combined with the lack of available conventional data in this region, means that we have a poor understanding of their climatological characteristics. In this study, the University of Melbourne cyclone finding algorithm was applied to relatively high resolution scatterometer-derived surface pressure fields in order to produce a decade-long (1999-2008) climatology of mesocyclone activity over the Southern Ocean. The frequency of mesocyclone activity was found to be highest just to the north of the sea-ice zone, reaching a maximum over the Amundsen and Bellingshausen Seas (ABS) and off the coast of Wilkes Land, while the southern Indian Ocean was associated with systems of the largest depth, intensity and mean surface fluxes of momentum and mechanical energy. Maximum wind speed data indicated that SH polar lows may be more frequent than the current literature suggests, while strong positive trends identified in mesocyclone frequency over the ABS may represent a contributing factor to the rapid warming observed in that region over recent years. Partial correlation analyses indicated a link between mesocyclone frequency and the Southern Annular Mode.

  16. Scatterometer-derived Southern Ocean mesoscale cyclone activity over the last decade

    Energy Technology Data Exchange (ETDEWEB)

    Irving, D; Simmonds, I; Keay, K, E-mail: damien.irving@csiro.a [School of Earth Sciences, University of Melbourne, Victoria (Australia)

    2010-08-15

    Mesoscale cyclones (or mesocyclones) play an important role in the weather and climate of the Southern Hemisphere (SH) mid-to-high latitudes. However, the relatively small size and short lifetime of these systems, combined with the lack of available conventional data in this region, means that we have a poor understanding of their climatological characteristics. In this study, the University of Melbourne cyclone finding algorithm was applied to relatively high resolution scatterometer-derived surface pressure fields in order to produce a decade-long (1999-2008) climatology of mesocyclone activity over the Southern Ocean. The frequency of mesocyclone activity was found to be highest just to the north of the sea-ice zone, reaching a maximum over the Amundsen and Bellingshausen Seas (ABS) and off the coast of Wilkes Land, while the southern Indian Ocean was associated with systems of the largest depth, intensity and mean surface fluxes of momentum and mechanical energy. Maximum wind speed data indicated that SH polar lows may be more frequent than the current literature suggests, while strong positive trends identified in mesocyclone frequency over the ABS may represent a contributing factor to the rapid warming observed in that region over recent years. Partial correlation analyses indicated a link between mesocyclone frequency and the Southern Annular Mode.

  17. The White Ocean hypothesis: a late Pleistocene Southern Ocean governed by Coccolithophores and driven by phosphorus

    Directory of Open Access Journals (Sweden)

    Jose Abel Flores

    2012-07-01

    Full Text Available Paleoproductivity is a critical component in past ocean biogeochemistry, but accurate reconstructions of productivity are often hindered by limited integration of proxies. Here, we integrate geochemical (phosphorus and micropaleontological proxies at millennial timescales, revealing that the coccolithophore record in the Subantarctic zone of the South Atlantic Ocean is driven largely by variations in marine phosphorus availability. A quantitative micropaleontological and geochemical analysis carried out in sediments retrieved from ODP Site 1089 (Subantarctic Zone reveals that most of the export productivity in this region over the last 0.5 my was due to coccolithophores. Glacial periods were generally intervals of high productivity, with productivity reaching a peak at terminations. Particularly high productivity was observed at Termination V and Termination IV, events that are characterized by high abundance of coccolithophores and maxima in the phosphorus/titanium and strontium/titanium records. We link the increase in productivity both to regional oceanographic phenomena, i.e., the northward displacement of the upwelling cell of the Antarctic divergence when the ice-sheet expanded, and to the increase in the inventory of phosphorus in the ocean due to enhanced transfer of this nutrient from continental margins during glacial lowstands in sea level. The Mid-Brunhes interval stands out from the rest of the record, being dominated by the small and highly-calcified species Gephyrocapsa caribbeanica that provides most of the carbonate in these sediments. This likely represents higher availability of phosphorus in the surface ocean, especially in mesotrophic and oligotrophic zones. Under these condition, some coccolithophore species developed an r-strategy (opportunistic species; growth rate maximized resulting in the bloom of G. caribbeanica. These seasonal blooms of may have inducedwhite tides similar to those observed today in Emiliania huxleyi.

  18. Ecosystem studies in the Indian Ocean sector of the Southern Ocean undertaken by the training vessel Umitaka-maru

    Science.gov (United States)

    Moteki, Masato; Odate, Tsuneo; Hosie, Graham W.; Takahashi, Kunio T.; Swadling, Kerrie M.; Tanimura, Atsushi

    2017-06-01

    This special issue provides an overview of the ten voyages undertaken by the Umitaka-maru from the austral summers of 2002/2003 to 2014/2015 to promote the next phase of study of the ecosystems in the Indian Ocean sector of the Southern Ocean. The voyages by the Umitaka-maru have mainly targeted three areas in the Indian Ocean sector: off Dumont d'Urville Base (France, 140°E transect), off Casey Station (Australia, 110°E transect), and off Syowa Station (Japan, north of Lützow Holm Bay). The findings of Umitaka-maru's research on the krill-independent food web, animal assemblages, community structure and distribution patterns from the epipelagic to the deeper waters provide invaluable information for elucidating the material cycle and predicting future ecosystem changes. Further studies on assessing the influence of sea ice on food webs in the water column are required, which will provide crucial information for predicting ecosystem changes as a result of projected sea ice changes in the near future.

  19. The International Bathymetric Chart of the Southern Ocean - A new Map of Antarctica

    Science.gov (United States)

    Arndt, J.; Schenke, H. W.

    2012-12-01

    The International Bathymetric Chart of the Southern Ocean (IBCSO) is an expert group of the Scientific Committee on Antarctic Research (SCAR) since the XXVIII SCAR Conference held on 30th July 2004 in Bremen Germany and a regional Mapping project of the General Bathymetric Chart of the Ocean (GEBCO) operated under the joint auspices of the Intergovernmental Oceanographic Commission (IOC) (of UNESCO) and the International Hydrographic Organization (IHO). The objective of IBCSO was to produce a first seamless bathymetric grid for the area south of latitude 60° S covering the area of the Antarctic Treaty. The IBCSO is going to be a benefit for scientific purposes. These include (a) interpretation of seabed geology, (b) the building of habitat models and maps, and (c) mapping and tracing of deep ocean current pathways. In addition the IBCSO is going to serve as database for the development of new Electronic Nautical Charts (ENC) in the Southern Ocean to improve the safety of navigation in Antarctic waters. As the first version of the IBCSO grid is close to be released, so is the corresponding map. It is proposed to present the latest draft version, or even the final version, of the new IBCSO map. Besides the map itself, the process to achieve the first version of the IBCSO grid and map is going to be presented. This includes a description of the datasets used to create the map and a rough explanation of the working steps to generate the first grid version of the IBCSO.

  20. Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO

    Science.gov (United States)

    Heuzé, C.; Ridley, J. K.; Calvert, D.; Stevens, D. P.; Heywood, K. J.

    2015-03-01

    Most CMIP5 models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross Seas. To identify the triggering mechanisms leading to Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean model NEMO forced by prescribed atmospheric fluxes. We vary the vertical velocity scale of the Langmuir turbulence, the fraction of turbulent kinetic energy transferred below the mixed layer, and the background diffusivity and run short simulations from 1980. All experiments exhibit deep convection in the Riiser-Larsen Sea in 1987; the origin is a positive sea ice anomaly in 1985, causing a shallow anomaly in mixed layer depth, hence anomalously warm surface waters and subsequent polynya opening. Modifying the vertical mixing impacts both the climatological state and the associated surface anomalies. The experiments with enhanced mixing exhibit colder surface waters and reduced deep convection. The experiments with decreased mixing are warmer, open larger polynyas and have deep convection across the Weddell Sea until the simulations end. Extended experiments reveal an increase in the Drake Passage transport of 4 Sv each year deep convection occurs, leading to an unrealistically large transport at the end of the simulation. North Atlantic deep convection is not significantly affected by the changes in mixing parameters. As new climate model overflow parameterisations are developed to form Antarctic Bottom Water more realistically, we argue that models would benefit from stopping Southern Ocean deep convection, for example by increasing their vertical mixing.

  1. Southern Ocean monthly wave fields for austral winters 1985-1988 by Geosat radar altimeter

    Science.gov (United States)

    Josberger, E.G.; Mognard, N.M.

    1996-01-01

    Four years of monthly averaged wave height fields for the austral winters 19851988 derived from the Geosat altimeter data show a spatial variability of the scale of 500-1000 km that varies monthly and annually. This variability is superimposed on the zonal patterns surrounding the Antarctic continent and characteristic of the climatology derived from the U.S. Navy [1992] Marine Climatic Atlas of the World. The location and the intensity of these large-scale features, which are not found in the climatological fields, exhibit strong monthly and yearly variations. A global underestimation of the climatological mean wave heights by more than l m is also found over large regions of the Southern Ocean. The largest monthly averaged significant wave heights are above 5 m and are found during August of every year in the Indian Ocean, south of 40??S. The monthly wave fields show more variability in the Atlantic and Pacific Oceans than in the Indian Ocean. The Seasat data from 1978 and the Geosat data from 1985 and 1988 show an eastward rotation of the largest wave heights. However, this rotation is absent in 1986 and 1987; the former was a year of unusually low sea states, and the latter was a year of unusually high sea states, which suggests a link to the El Nin??o-Southern Oscillation event of 1986. Copyright 1996 by the American Geophysical Union.

  2. Low densities of drifting litter in the African sector of the Southern Ocean.

    Science.gov (United States)

    Ryan, Peter G; Musker, Seth; Rink, Ariella

    2014-12-15

    Only 52 litter items (>1cm diameter) were observed in 10,467 km of at-sea transects in the African sector of the Southern Ocean. Litter density north of the Subtropical Front (0.58 items km(-2)) was less than in the adjacent South Atlantic Ocean (1-6 items km(-2)), but has increased compared to the mid-1980s. Litter density south of the Subtropical Front was an order of magnitude less than in temperate waters (0.032 items km(-2)). There was no difference in litter density between sub-Antarctic and Antarctic waters either side of the Antarctic Polar Front. Most litter was made of plastic (96%). Fishery-related debris comprised a greater proportion of litter south of the Subtropical Front (33%) than in temperate waters (13%), where packaging dominated litter items (68%). The results confirm that the Southern Ocean is the least polluted ocean in terms of drifting debris and suggest that most debris comes from local sources. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Changes in the C, N, and P cycles by the predicted salps-krill shift in the southern ocean

    OpenAIRE

    Alcaraz, Miquel; Almeda, Rodrigo; Duarte, Carlos M.; Horstkotte, Burkhard; Lasternas, Sebastien; Agustí, Susana

    2014-01-01

    The metabolic carbon requirements and excretion rates of three major zooplankton groups in the Southern Ocean were studied in February 2009. The research was conducted in the framework of the ATOS research project as part of the Spanish contribution to the International Polar Year. The objective was to ascertain the possible consequences of the predicted zooplankton shift from krill to salps in the Southern Ocean for the cycling of biogenic carbon and the concentration and stoichiometry of di...

  4. CHANGES IN THE C, N AND P CYCLES BY THE PREDICTED SALPS-KRILL SHIFT IN THE SOUTHERN OCEAN.

    OpenAIRE

    Miquel eAlcaraz; Rodrigo eAlmeda; Carlos Manuel Duarte; Burkhard eHorstkotte; Sebastien eLasternas; Susana eAgustí

    2014-01-01

    The metabolic carbon requirements and excretion rates of three major zooplankton groups in the Southern Ocean were studied in February 2009. The research was conducted in the framework of the ATOS research project as part of the Spanish contribution to the International Polar Year. The objective was to ascertain the possible consequences of the predicted zooplankton shift from krill to salps in the Southern Ocean for the cycling of biogenic carbon and the concentration and stoichiometry of di...

  5. Inter-annual variability in Antarctic krill (Euphausia superba) density at South Georgia, Southern Ocean: 1997 - 2013

    OpenAIRE

    Fielding, Sophie; Watkins, Jonathan L.; Trathan, Philip N.; Enderlein,Peter; Waluda, Claire M.; Stowasser, Gabriele; Tarling, Geraint A.; Eugene J. Murphy

    2014-01-01

    Antarctic krill (Euphausia superba) are a key species in Southern Ocean ecosystems, maintaining very large numbers of predators, and fluctuations in their abundance can affect the overall structure and functioning of the ecosystems. The interannual variability in the abundance and biomass of krill was examined using a 17-year time-series of acoustic observations undertaken in the Western Core Box (WCB) survey area to the northwest of South Georgia, Southern Ocean. Krill targets were identifie...

  6. Effect of varying frontal systems on stable oxygen and carbon isotopic compositions of modern planktic foraminifera of Southern Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Tiwari, M.; Mohan, R.; Meloth, T.; Naik, S.S.; Sudhakar, M.

    SCIENCE, VOL. 100, NO. 6, 25 MARCH 2011 881 *For correspondence. (e-mail: manish@ncaor.org) Effect of varying frontal systems on stable oxygen and carbon isotopic compositions of modern planktic foraminifera of Southern Ocean Manish Tiwari 1...: Carbon isotopes, foraminifera, oxygen iso- topes, Southern Ocean. PLANKTIC foraminifera thrive in various environments of the upper water column and are sensitive to changes occurring in the temperature, salinity, nutrients, food availability...

  7. A new species of Marumomysis (Mysidacea: Mysidae: Erythropini from the benthos of the Bellingshausen Sea (Southern Ocean

    Directory of Open Access Journals (Sweden)

    Carlos San Vicente

    2007-12-01

    Full Text Available A new mysid species, Marumomysis Antarctica n. sp., is described from specimens sampled with a suprabenthic sled in the Bellingshausen Sea (Southern Ocean. The new mysid is characterised by the small eyes lacking visual elements and with a long horn projecting anteriodorsally, the trilobate labrum and the shape and armature of the endopod of the uropod and telson. This new species is the first Marumomysis species described from the benthos (1320-1895 m depth of the Southern Ocean.

  8. Sea-ice transport driving Southern Ocean salinity and its recent trends

    Science.gov (United States)

    Haumann, F. Alexander; Gruber, Nicolas; Münnich, Matthias; Frenger, Ivy; Kern, Stefan

    2016-09-01

    Recent salinity changes in the Southern Ocean are among the most prominent signals of climate change in the global ocean, yet their underlying causes have not been firmly established. Here we propose that trends in the northward transport of Antarctic sea ice are a major contributor to these changes. Using satellite observations supplemented by sea-ice reconstructions, we estimate that wind-driven northward freshwater transport by sea ice increased by 20 ± 10 per cent between 1982 and 2008. The strongest and most robust increase occurred in the Pacific sector, coinciding with the largest observed salinity changes. We estimate that the additional freshwater for the entire northern sea-ice edge entails a freshening rate of -0.02 ± 0.01 grams per kilogram per decade in the surface and intermediate waters of the open ocean, similar to the observed freshening. The enhanced rejection of salt near the coast of Antarctica associated with stronger sea-ice export counteracts the freshening of both continental shelf and newly formed bottom waters due to increases in glacial meltwater. Although the data sources underlying our results have substantial uncertainties, regional analyses and independent data from an atmospheric reanalysis support our conclusions. Our finding that northward sea-ice freshwater transport is also a key determinant of the mean salinity distribution in the Southern Ocean further underpins the importance of the sea-ice-induced freshwater flux. Through its influence on the density structure of the ocean, this process has critical consequences for the global climate by affecting the exchange of heat, carbon and nutrients between the deep ocean and surface waters.

  9. Seasonal in situ observations of glyoxal and methylglyoxal over the temperate oceans of the Southern Hemisphere

    Science.gov (United States)

    Lawson, S. J.; Selleck, P. W.; Galbally, I. E.; Keywood, M. D.; Harvey, M. J.; Lerot, C.; Helmig, D.; Ristovski, Z.

    2015-01-01

    The dicarbonyls glyoxal and methylglyoxal have been measured with 2,4-dinitrophenylhydrazine (2,4-DNPH) cartridges and high-performance liquid chromatography (HPLC), optimised for dicarbonyl detection, in clean marine air over the temperate Southern Hemisphere (SH) oceans. Measurements of a range of dicarbonyl precursors (volatile organic compounds, VOCs) were made in parallel. These are the first in situ measurements of glyoxal and methylglyoxal over the remote temperate oceans. Six 24 h samples were collected in summer (February-March) over the Chatham Rise in the south-west Pacific Ocean during the Surface Ocean Aerosol Production (SOAP) voyage in 2012, while 34 24 h samples were collected at Cape Grim Baseline Air Pollution Station in the late winter (August-September) of 2011. Average glyoxal mixing ratios in clean marine air were 7 ppt at Cape Grim and 23 ppt over Chatham Rise. Average methylglyoxal mixing ratios in clean marine air were 28 ppt at Cape Grim and 10 ppt over Chatham Rise. The mixing ratios of glyoxal at Cape Grim are the lowest observed over the remote oceans, while mixing ratios over Chatham Rise are in good agreement with other temperate and tropical observations, including concurrent Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations. Methylglyoxal mixing ratios at both sites are comparable to the only other marine methylglyoxal observations available over the tropical Northern Hemisphere (NH) ocean. Ratios of glyoxal : methylglyoxal > 1 over Chatham Rise but water absorption or the use of an inappropriate normalisation reference value in the retrieval algorithm. This study provides much-needed data to verify the presence of these short-lived gases over the remote ocean and provide further evidence of an as yet unidentified source of both glyoxal and also methylglyoxal over the remote oceans.

  10. Late Pliocene Changes in Abyssal Southern Ocean Ventilation: New Insights from the Subantarctic Pacific

    Science.gov (United States)

    Waddell, L. M.; Hendy, I. L.; Moore, T. C.; Lyle, M. W.

    2008-12-01

    New stable isotope records from subantarctic southeast Pacific cores MV0502-4JC (50°20'S, 148°08'W, 4286m) and ELT 25-11 (50°02'S, 127°31'W, 3969m) suggest that the late Pliocene climate transition (LPCT) at ~2.75 Ma marked a dramatic increase in cold, poorly ventilated water in the deepest portion of the Southern Ocean. This conclusion is based on a striking vertical stable isotopic gradient that developed between MV0502-4JC and shallower South Atlantic ODP Site 704 (46°52'S, 7°5'E, 2532 m) in the late Pliocene, a sharp contrast to the comparable benthic δ13C and δ18O values recorded at the two sites during the late Miocene. Similar to existing shallower records from the South Atlantic, benthic stable isotope records from MV0502-4JC and ELT 25-11 record a significant decrease in δ13C accompanied by an increase in δ18O in the Late Pliocene. While the δ13C decrease and δ18O increase recorded at the South Atlantic sites appears to represent the onset of a glacial pattern of oxygen isotope enrichment and reduced deep water ventilation in the Southern Ocean, the transition in MV0502-4JC and ELT 25-11 signals a far more dramatic shift in conditions at abyssal depths. First, the benthic δ13C shift appears to be more extensive and prolonged in the deep subantarctic Pacific than in the South Atlantic, and second, the δ13C decrease was accompanied by an equally dramatic increase in benthic δ18O that stands out amongst other deep sea records prior to the late Pleistocene. In MV0502-4JC these δ13C and δ18O shifts amount to -1.05‰ and +1.1‰, respectively, over the period ~2.7 to 1.9 Ma (9.6-7.3 MBSF) and are followed by a dramatic return of the benthic δ13C values to pre-LPCT values after ~1.7 Ma that is also recorded in the planktonic record. These benthic δ13C and δ18O shifts likely indicate the accumulation of an ever-larger percentage of cold, poorly-ventilated AABW in the abyssal Southern Ocean during the late Pliocene, probably due to sea ice

  11. Observations of frozen skin of southern ocean from multifrequency scanning microwave radiometer (MSMR) onboard oceansat - 1

    Science.gov (United States)

    Vyas, N.; Bhandari, S.; Dash, M.; Pandey, P.; Khare, N.

    Encircling the Antarctic, Southern Ocean connects all the three oceans of the world with fastest current system found anywhere in the world. The region is thermally very stable and is covered with ice, which has a strong seasonal variability. The sea ice pulsates annually with seasonal migration varying from 4 million square kilometer to 20 million square kilometer during summer and winter respectively. This has strong influence on energy balance of the ocean-ice-atmosphere system, and hence on atmospheric general circulation affecting weather and climate. Sea ice also works as an insulator thus inhibiting the energy flux between ocean and atmosphere. It also influences the ecosystem of the southern ocean, which has rich fish resources with global economic values such as krill and tooth fish. During winter Krill survives on algae found at the under side of the sea ice. The southern ocean is known to have high nutrition but low concentration of chlorophyll-a, which is a proxy of the phytoplankton. It is now understood that iron is the limiting factor as has been shown by various iron fertilization experiments. Passive microwave radiometry from space has been extensively used for the study of sea ice types and concentration in the Arctic and the Antarctic regions. Since late 1970s, data from SMMR and SSM/I have been used to study trends in sea ice extent and area. We have further extended the above studies by using data from OCEANSAT - 1 MSMR. The data, acquired at 18 GHz (H) with 50 kilometer resolution and having a swath of 1360 kilometer and a repeat cycle of 2 days, was processed to generate the brightness temperature maps over the Antarctica for a period of 2 years and the results were analyzed in conjunction with those obtained earlier (since 1978) through the study of SMMR and SSM/I data. Besides strong seasonal variability, our analysis shows an increasing trend in the sea ice extent during the recent years and the rate appears to be accelerating contrary to

  12. Response of bacterioplankton to iron fertilization of the Southern Ocean, Antarctica.

    Science.gov (United States)

    Singh, Sanjay K; Kotakonda, Arunasri; Kapardar, Raj K; Kankipati, Hara Kishore; Sreenivasa Rao, Pasupuleti; Sankaranarayanan, Pratibha Mambatta; Vetaikorumagan, Sundareswaran R; Gundlapally, Sathyanarayana Reddy; Nagappa, Ramaiah; Shivaji, Sisinthy

    2015-01-01

    Ocean iron fertilization is an approach to increase CO2 sequestration. The Indo-German iron fertilization experiment "LOHAFEX" was carried out in the Southern Ocean surrounding Antarctica in 2009 to monitor changes in bacterial community structure following iron fertilization-induced phytoplankton bloom of the seawater from different depths. 16S rRNA gene libraries were constructed using metagenomic DNA from seawater prior to and after iron fertilization and the clones were sequenced for identification of the major bacterial groups present and for phylogenetic analyses. A total of 4439 clones of 16S rRNA genes from ten 16S rRNA gene libraries were sequenced. More than 97.35% of the sequences represented four bacterial lineages i.e. Alphaproteobacteria, Gammaproteobacteria, Bacteroidetes, and Firmicutes and confirmed their role in scavenging of phytoplankton blooms induced following iron fertilization. The present study demonstrates the response of Firmicutes due to Iron fertilization which was not observed in previous southern ocean Iron fertilization studies. In addition, this study identifies three unique phylogenetic clusters LOHAFEX Cluster 1 (affiliated to Bacteroidetes), 2, and 3 (affiliated to Firmicutes) which were not detected in any of the earlier studies on iron fertilization. The relative abundance of these clusters in response to iron fertilization was different. The increase in abundance of LOHAFEX Cluster 2 and Papillibacter sp. another dominant Firmicutes may imply a role in phytoplankton degradation. Disappearance of LOHAFEX Cluster 3 and other bacterial genera after iron fertilization may imply conditions not conducive for their survival. It is hypothesized that heterotrophic bacterial abundance in the Southern Ocean would depend on their ability to utilize algal exudates, decaying algal biomass and other nutrients thus resulting in a dynamic bacterial succession of distinct genera.

  13. Present and Past Impact of Glacially Sourced Dust on Iron Fertilization of the Southern Ocean

    Science.gov (United States)

    Shoenfelt, E. M.; Winckler, G.; Kaplan, M. R.; Sambrotto, R.; Bostick, B. C.

    2016-12-01

    An increase in iron-containing dust flux and a more efficient biological pump in the Southern Ocean have been associated with the CO2 drawdown and global cooling of the Last Glacial Maximum (LGM). While iron (Fe) mineralogy is known to affect Fe bioavailability through its impact on Fe solubility, there are limited studies investigating the importance of Fe mineralogy in dust fluxes to the Southern Ocean, and no previous studies investigating interactions between eukaryotic phytoplankton and particulate-phase Fe in natural dusts applicable to Southern Ocean environments. Since physically weathered bedrock becomes less soluble as it becomes weathered and oxidized, we hypothesized that glacially sourced dusts would contain more Fe(II)-rich primary minerals and would be more bioavailable than dusts from areas not impacted by glaciers. We used a series of natural dusts from Patagonia as the sole Fe source in incubation experiments with the model diatom Phaeodactylum tricornutum, and evaluated Fe bioavailability using culture growth rates, cell density, and variable fluorescence. Monod curves were also used to evaluate the efficiency of the different particulates as sources of nutrient Fe. Using these Monod curves fit to growth rates plotted against particulate Fe concentrations, we observed that 1) Fe(II)-rich primary silicates were significantly more effective as an Fe source to diatoms than Fe(III)-rich oxides, that 2) Fe(II) content itself was responsible for the difference in Fe bioavailability/efficiency of the Fe nutrient source, and that 3) surface interactions with the particulates were important. In an effort to explore the possibility that Fe mineralogy impacted Fe bioavailability in past oceans, we will present our hypotheses regarding productivity and Fe mineralogy/bioavailability through the last glacial cycle.

  14. Volcanism, Iron, and Phytoplankton in the Heard and McDonald Islands Region, Southern Indian Ocean

    Science.gov (United States)

    Coffin, M. F.; Arculus, R. J.; Bowie, A. R.; Chase, Z.; Robertson, R.; Trull, T. W.; Heobi in2016 v01 Shipboard Party, T.

    2016-12-01

    Phytoplankton supply approximately half of the oxygen in Earth's atmosphere, and iron supply limits the growth of phytoplankton in the anemic Southern Ocean. Situated entirely within the Indian Ocean sector of the Southern Ocean are Australia's only active subaerial volcanoes, Heard and McDonald islands (HIMI) on the central Kerguelen Plateau, a large igneous province. Widespread fields of submarine volcanoes, some of which may be active, extend for distances of up to several hundred kilometers from the islands. The predominantly eastward-flowing Antarctic Circumpolar Current sweeps across the central Kerguelen Plateau, and extensive blooms of phytoplankton are observed on the Plateau down-current of HIMI. The goal of RV Investigator voyage IN2016_V01, conducted in January/February 2016, is to test the hypothesis that hydrothermal fluids, which cool active submarine volcanoes in the HIMI region, ascend from the seafloor and fertilise surface waters with iron, thereby enhancing biological productivity beginning with phytoplankton. Significant initial shipboard results include: Documentation, for the first time, of the role of active HIMI and nearby submarine volcanoes in supplying iron to the Southern Ocean. Nearshore waters had elevated dissolved iron levels. Although biomass was not correspondingly elevated, fluorescence induction data indicated highly productive resident phytoplankton. Discovery of >200 acoustic plumes emanating from the seafloor and ascending up to tens of meters into the water column near HIMI. Deep tow camera footage shows bubbles rising from the seafloor in an acoustic plume field north of Heard Island. Mapping 1,000 km2 of uncharted seafloor around HIMI. Submarine volcanic edifices punctuate the adjacent seafloor, and yielded iron-rich rocks similar to those found on HIMI, respectively. Acoustic plumes emanating from some of these features suggest active seafloor hydrothermal systems.

  15. Factors limiting heterotrophic bacterial production in the southern Pacific Ocean

    Directory of Open Access Journals (Sweden)

    F. Van Wambeke

    2008-05-01

    Full Text Available The role of potential factors limiting bacterial growth was investigated along vertical and longitudinal gradients across the South Eastern Pacific Gyre. The effects of glucose, nitrate, ammonium and phosphate additions on heterotrophic bacterial production (using leucine technique were studied in parallel in unfiltered seawater samples incubated under natural daily irradiance. The enrichments realized on the subsurface showed three types of responses. From 141° W (Marquesas plateau to approx 125° W, bacteria were not bottom-up controlled, as confirmed by the huge potential of growth in non-enriched seawater (median of enhancement factor×39 in 24 h. Within the Gyre (125° W–95° W, nitrogen alone stimulated leucine incorporation rates (median×4.2, but rapidly labile carbon (glucose became a second limiting factor (median×37 when the two elements were added. Finally from the border of the gyre to the Chilean upwelling (95° W–73° W, labile carbon was the only factor stimulating heterotrophic bacterial production. Interaction between phytoplankton and heterotrophic bacterial communities and the direct versus indirect effect of iron and macronutrients on bacterial production were also investigated in four selected sites: two sites on the vicinity of the Marquesas plateau, the centre of the gyre and the Eastern border of the gyre. Both phytoplankton and heterotrophic bacteria were limited by availability of nitrogen within the gyre, but not by iron. Iron limited phytoplankton at Marquesas plateau and at the eastern border of the gyre. However 48 h enrichment experiments were not sufficient to show any clear limitation of heterotrophic bacteria within Marquesas plateau and showed a limitation of these organisms by labile carbon in the eastern border of the Gyre.

  16. Carbon demand, utilization, and metabolic diversity of bacterioplankton in the frontal regimes of the Indian sector of the Southern Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnan, K.P.; Sinha, R.K.; Nair, S.; Noronha, S.B.; Chacko, R.; Anilkumar, N.

    Bacterial production, respiration and metabolic diversity were measured up to 120 m depth in the Sub-Antarctic Front (SAF) and Polar Fronts I and II (PFI and PFII) of the Indian Ocean sector of the Southern Ocean during 2010 Austral Summer...

  17. Linking small-scale circulation dynamics with large-scale seasonal production (phytoplankton) in the Southern Ocean

    CSIR Research Space (South Africa)

    Nicholson, S

    2012-10-01

    Full Text Available Understanding the seasonal and intra-seasonal (daily to weekly) changes of the upper ocean and the impact on the primary production in the Southern Ocean is key to better understanding the sensitivities of the global carbon cycle....

  18. Comparisons of The Habitat Utilization Of Top Predators In The Southern Ocean And The North Pacific

    Science.gov (United States)

    Costa, D. P.; Robinson, P.; Huckstadt, L. E.; Crocker, D. E.; Goebel, M. E.

    2010-12-01

    Northern and Southern elephant seals (Mirounga angustirostris, M. leonina) separated some 4 MYA. While these congeners are physiologically very similar and thus have the potential to forage in similar ways they inhabit very different habitats. While southern elephant seals (SES) are distributed throughout the southern ocean, northern elephant seals (NES) are limited to the Northeast Pacific Ocean and range over lower latitudes than SES. In order to compare and contrast the physiological capability and response to different habitats we compared the foraging behavior of 167 adult female northern elephant seals (Año Nuevo and San Benitos Islands) and 55 southern elephant seals (Livingston Island, Antarctic Peninsula) using satellite telemetry and dive recorders. As expected both species carried out very similar dive depths (NES 509m ± 166 vs SES 345m±79) and dive durations (NES 23.0 min ± 6.7; SES 22.5 min ± 5.0). However, there were significant differences in their foraging pattern that we attribute to differences in the availability of continental shelf and suitable foraging habitat. While 85% of NES females foraged offshore, the dominant strategy for SES was benthic foraging on the continental shelf. Even with the differences in habitat, the fundamental components of their foraging patterns remained the same as when they foraged pelagically they both species relied on persistent large scale oceanographic features where mixing enhances productivity such as the North Pacific Transition zone (NES) and the Southern Antarctic Circumpolar Current Front (SES). Given the very different habitats and prey species consumed by these two species their overall foraging behavior is surprisingly similar suggesting that as a mesopelagic predator the elephant seal design is rather robust.

  19. Southern Ocean warming and Wilkes Land ice sheet retreat during the mid-Miocene.

    Science.gov (United States)

    Sangiorgi, Francesca; Bijl, Peter K; Passchier, Sandra; Salzmann, Ulrich; Schouten, Stefan; McKay, Robert; Cody, Rosemary D; Pross, Jörg; van de Flierdt, Tina; Bohaty, Steven M; Levy, Richard; Williams, Trevor; Escutia, Carlota; Brinkhuis, Henk

    2018-01-22

    Observations and model experiments highlight the importance of ocean heat in forcing ice sheet retreat during the present and geological past, but past ocean temperature data are virtually missing in ice sheet proximal locations. Here we document paleoceanographic conditions and the (in)stability of the Wilkes Land subglacial basin (East Antarctica) during the mid-Miocene (~17-13.4 million years ago) by studying sediment cores from offshore Adélie Coast. Inland retreat of the ice sheet, temperate vegetation, and warm oligotrophic waters characterise the mid-Miocene Climatic Optimum (MCO; 17-14.8 Ma). After the MCO, expansion of a marine-based ice sheet occurs, but remains sensitive to melting upon episodic warm water incursions. Our results suggest that the mid-Miocene latitudinal temperature gradient across the Southern Ocean never resembled that of the present day. We demonstrate that a strong coupling of oceanic climate and Antarctic continental conditions existed and that the East Antarctic subglacial basins were highly sensitive to ocean warming.

  20. Pleistocene atmospheric CO2 change linked to Southern Ocean nutrient utilization

    Science.gov (United States)

    Ziegler, M.; Diz, P.; Hall, I. R.; Zahn, R.

    2011-12-01

    Biological uptake of CO2 by the ocean and its subsequent storage in the abyss is intimately linked with the global carbon cycle and constitutes a significant climatic force1. The Southern Ocean is a particularly important region because its wind-driven upwelling regime brings CO2 laden abyssal waters to the surface that exchange CO2 with the atmosphere. The Subantarctic Zone (SAZ) is a CO2 sink and also drives global primary productivity as unutilized nutrients, advected with surface waters from the south, are exported via Subantarctic Mode Water (SAMW) as preformed nutrients to the low latitudes where they fuel the biological pump in upwelling areas. Recent model estimates suggest that up to 40 ppm of the total 100 ppm atmospheric pCO2 reduction during the last ice age were driven by increased nutrient utilization in the SAZ and associated feedbacks on the deep ocean alkalinity. Micro-nutrient fertilization by iron (Fe), contained in the airborne dust flux to the SAZ, is considered to be the prime factor that stimulated this elevated photosynthetic activity thus enhancing nutrient utilization. We present a millennial-scale record of the vertical stable carbon isotope gradient between subsurface and deep water (Δδ13C) in the SAZ spanning the past 350,000 years. The Δδ13C gradient, derived from planktonic and benthic foraminifera, reflects the efficiency of biological pump and is highly correlated (rxy = -0.67 with 95% confidence interval [0.63; 0.71], n=874) with the record of dust flux preserved in Antarctic ice cores6. This strongly suggests that nutrient utilization in the SAZ was dynamically coupled to dust-induced Fe fertilization across both glacial-interglacial and faster millennial timescales. In concert with ventilation changes of the deep Southern Ocean this drove ocean-atmosphere CO2 exchange and, ultimately, atmospheric pCO2 variability during the late Pleistocene.

  1. Viral effects on bacterial respiration, production and growth efficiency: Consistent trends in the Southern Ocean and the Mediterranean Sea

    Science.gov (United States)

    Bonilla-Findji, Osana; Malits, Andrea; Lefèvre, Dominique; Rochelle-Newall, Emma; Lemée, Rodolphe; Weinbauer, Markus G.; Gattuso, Jean-Pierre

    2008-03-01

    To investigate the potential effects of viruses on bacterial respiration (BR), production (BP) and growth efficiency (BGE), experiments were performed using natural microbial communities from the coastal Mediterranean Sea, from a typical high-nutrient low-chlorophyll (HNLC) region in the Southern Ocean and from a naturally iron (Fe)-fertilized algal bloom above the Kerguelen Plateau (Southern Ocean). Seawater was sequentially filtered and concentrated to produce a bacterial concentrate, a viral concentrate and a virus-free ultrafiltrate. The combination of all three fractions served as treatments with active viruses. Heating or microwaving was used to inactivate viruses for the control treatments. Despite the differences in the initial trophic state and community composition of the study sites, consistent trends were found. In the presence of active viruses, BR was stimulated (up to 113%), whereas BP and BGE were reduced (up to 51%). Our results suggest that viruses enhance the role of bacteria as oxidizers of organic matter, hence as producers of CO 2, and remineralizers of CO 2, N, P and Fe. In the context of Fe-fertilization, this has important implications for the final fate of organic carbon in marine systems.

  2. Factors controlling January-April rainfall over southern India and Sri Lanka

    Energy Technology Data Exchange (ETDEWEB)

    Vialard, J. [Universite Pierre et Marie Curie, Laboratoire d' Oceanographie Experimentation et Approches Numeriques (LOCEAN), CNRS, IRD, Paris (France); National Institute of Oceanography, Dona Paula, Goa (India); Terray, P. [Universite Pierre et Marie Curie, Laboratoire d' Oceanographie Experimentation et Approches Numeriques (LOCEAN), CNRS, IRD, Paris (France); Duvel, J.P. [CNRS, Laboratoire de Meteorologie Dynamique, Paris (France); Nanjundiah, R.S. [IISc, Center of Atmospheric and Oceanic Sciences, Bangalore (India); Shenoi, S.S.C. [Indian National Centre for Ocean Information Services, Hyderabad (India); Shankar, D. [National Institute of Oceanography, Dona Paula, Goa (India)

    2011-08-15

    Most of the annual rainfall over India occurs during the Southwest (June-September) and Northeast (October-December) monsoon periods. In March 2008, however, Southern peninsular India and Sri Lanka received the largest rainfall anomaly on record since 1979, with amplitude comparable to summer-monsoon interannual anomalies. This anomalous rainfall appeared to be modulated at intraseasonal timescale by the Madden Julian Oscillation, and was synchronous with a decaying La Nina event in the Pacific Ocean. Was this a coincidence or indicative of a teleconnection pattern? In this paper, we explore factors controlling rainfall over southern India and Sri Lanka between January and April, i.e. outside of the southwest and northeast monsoons. This period accounts for 20% of annual precipitation over Sri Lanka and 10% over the southern Indian states of Kerala and Tamil Nadu. Interannual variability is strong (about 40% of the January-April climatology). Intraseasonal rainfall anomalies over southern India and Sri Lanka are significantly associated with equatorial eastward propagation, characteristic of the Madden Julian Oscillation. At the interannual timescale, we find a clear connection with El Nino-Southern Oscillation (ENSO); with El Ninos being associated with decreased rainfall (correlation of -0.46 significant at the 98% level). There is also a significant link with local SST anomalies over the Indian Ocean, and in particular with the inter-hemispheric sea surface temperature (SST) gradient over the Indian Ocean (with colder SST south of the equator being conducive to more rainfall, correlation of 0.55 significant at the 99% level). La Ninas/cold SSTs south of the equator tend to have a larger impact than El Ninos. We discuss two possible mechanisms that could explain these statistical relationships: (1) subsidence over southern India remotely forced by Pacific SST anomalies; (2) impact of ENSO-forced regional Indian Ocean SST anomalies on convection. However, the

  3. The biogeochemical role of baleen whales and krill in Southern Ocean nutrient cycling.

    Directory of Open Access Journals (Sweden)

    Lavenia Ratnarajah

    Full Text Available The availability of micronutrients is a key factor that affects primary productivity in High Nutrient Low Chlorophyll (HNLC regions of the Southern Ocean. Nutrient supply is governed by a range of physical, chemical and biological processes, and there are significant feedbacks within the ecosystem. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but data on their contribution are scarce. We analysed the concentration of iron, cadmium, manganese, cobalt, copper, zinc, phosphorus and carbon in baleen whale faeces and muscle, and krill tissue using inductively coupled plasma mass spectrometry. Metal concentrations in krill tissue were between 20 thousand and 4.8 million times higher than typical Southern Ocean HNLC seawater concentrations, while whale faecal matter was between 276 thousand and 10 million times higher. These findings suggest that krill act as a mechanism for concentrating and retaining elements in the surface layer, which are subsequently released back into the ocean, once eaten by whales, through defecation. Trace metal to carbon ratios were also higher in whale faeces compared to whale muscle indicating that whales are concentrating carbon and actively defecating trace elements. Consequently, recovery of the great whales may facilitate the recycling of nutrients via defecation, which may affect productivity in HNLC areas.

  4. The biogeochemical role of baleen whales and krill in Southern Ocean nutrient cycling.

    Science.gov (United States)

    Ratnarajah, Lavenia; Bowie, Andrew R; Lannuzel, Delphine; Meiners, Klaus M; Nicol, Stephen

    2014-01-01

    The availability of micronutrients is a key factor that affects primary productivity in High Nutrient Low Chlorophyll (HNLC) regions of the Southern Ocean. Nutrient supply is governed by a range of physical, chemical and biological processes, and there are significant feedbacks within the ecosystem. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but data on their contribution are scarce. We analysed the concentration of iron, cadmium, manganese, cobalt, copper, zinc, phosphorus and carbon in baleen whale faeces and muscle, and krill tissue using inductively coupled plasma mass spectrometry. Metal concentrations in krill tissue were between 20 thousand and 4.8 million times higher than typical Southern Ocean HNLC seawater concentrations, while whale faecal matter was between 276 thousand and 10 million times higher. These findings suggest that krill act as a mechanism for concentrating and retaining elements in the surface layer, which are subsequently released back into the ocean, once eaten by whales, through defecation. Trace metal to carbon ratios were also higher in whale faeces compared to whale muscle indicating that whales are concentrating carbon and actively defecating trace elements. Consequently, recovery of the great whales may facilitate the recycling of nutrients via defecation, which may affect productivity in HNLC areas.

  5. Humpback whale song on the Southern Ocean feeding grounds: implications for cultural transmission.

    Directory of Open Access Journals (Sweden)

    Ellen C Garland

    Full Text Available Male humpback whales produce a long, complex, and stereotyped song on low-latitude breeding grounds; they also sing while migrating to and from these locations, and occasionally in high-latitude summer feeding areas. All males in a population sing the current version of the constantly evolving display and, within an ocean basin, populations sing similar songs; however, this sharing can be complex. In the western and central South Pacific region there is repeated cultural transmission of song types from eastern Australia to other populations eastward. Song sharing is hypothesized to occur through several possible mechanisms. Here, we present the first example of feeding ground song from the Southern Ocean Antarctic Area V and compare it to song from the two closest breeding populations. The early 2010 song contained at least four distinct themes; these matched four themes from the eastern Australian 2009 song, and the same four themes from the New Caledonian 2010 song recorded later in the year. This provides evidence for at least one of the hypothesized mechanisms of song transmission between these two populations, singing while on shared summer feeding grounds. In addition, the feeding grounds may provide a point of acoustic contact to allow the rapid horizontal cultural transmission of song within the western and central South Pacific region and the wider Southern Ocean.

  6. Humpback whale song on the Southern Ocean feeding grounds: implications for cultural transmission.

    Science.gov (United States)

    Garland, Ellen C; Gedamke, Jason; Rekdahl, Melinda L; Noad, Michael J; Garrigue, Claire; Gales, Nick

    2013-01-01

    Male humpback whales produce a long, complex, and stereotyped song on low-latitude breeding grounds; they also sing while migrating to and from these locations, and occasionally in high-latitude summer feeding areas. All males in a population sing the current version of the constantly evolving display and, within an ocean basin, populations sing similar songs; however, this sharing can be complex. In the western and central South Pacific region there is repeated cultural transmission of song types from eastern Australia to other populations eastward. Song sharing is hypothesized to occur through several possible mechanisms. Here, we present the first example of feeding ground song from the Southern Ocean Antarctic Area V and compare it to song from the two closest breeding populations. The early 2010 song contained at least four distinct themes; these matched four themes from the eastern Australian 2009 song, and the same four themes from the New Caledonian 2010 song recorded later in the year. This provides evidence for at least one of the hypothesized mechanisms of song transmission between these two populations, singing while on shared summer feeding grounds. In addition, the feeding grounds may provide a point of acoustic contact to allow the rapid horizontal cultural transmission of song within the western and central South Pacific region and the wider Southern Ocean.

  7. Waves in the Southern Ocean as observed by Sentinel1 synthetic aperture radars

    Science.gov (United States)

    Stopa, Justin E.; Sutherland, Peter; Ardhuin, Fabrice

    2017-04-01

    Sea ice plays an important role in the Earth system by regulating air-sea fluxes and moderating the global temperatures. These fluxes can be enhanced by the presence of waves, especially through the breaking of ice into floes which depends on the waves propagating across the ice. The paucity of adequate in-situ wave observations in ice covered seas limits our ability to understand wave-ice interactions. Synthetic Aperture Radar (SAR) imagery over sea ice appears consistent with a dominant modulation of the radar backscatter by velocity bunching (Ardhuin et al. GRL 2015). Because the presence of sea ice generally removes the blurring effects of short wave components, the SAR transformation is more simple than in the open ocean. This property makes it possible to retrieve phase-resolved maps of wave orbital velocities and wave spectra (Ardhuin et al., 2017 RSE). We can thus now use SAR imagery for scientific applications to wave-ice interactions. With the all-weather capabilities and extensive space-time coverage, the Sentinel1 constellation composed of two satellites (S1A & S1B) both equipped with SARs provides the opportunity to extract valuable wave observations in polar regions. Through the high resolution acquisition modes of S1A and S1B which cover the Southern Ocean in 20x20 km images with 4 m spatial resolution we are able to extract an large sample of wave observations. We analyzed more than 35,000 images in the Southern Ocean. Nearly 28% of the images contain wave features and 6% of the images contain well-imaged single wave systems (>2000 wave spectra), with a narrow directional distribution. This dataset of more than 2000 wave spectra is unique in the fact we cover the entire Southern Ocean sea ice with an unprecedented amount of observations. These observations support the idea that the attenuation of waves with periods longer than 10 s is dominated by dissipation processes with a limited effect of scattering. Dissipation rates are estimated from pairs

  8. Multi-elemental concentrations in the tissues of the oceanic squid Todarodes filippovae from Tasmania and the southern Indian Ocean.

    Science.gov (United States)

    Kojadinovic, Jessica; Jackson, Christine H; Cherel, Yves; Jackson, George D; Bustamante, Paco

    2011-07-01

    This study investigates 14 elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn) in the tissues of the oceanic ommastrephid squid Todarodes filippovae from waters surrounding Île Amsterdam (southern Indian Ocean) and Tasmania (Australia). As for other cephalopod species, the digestive gland and branchial hearts showed the highest concentrations of many elements (Ag, Cd, Se, V and Zn, and Cr and Ni, respectively) highlighting their role in bioaccumulation and detoxification processes. With the exception of As and Hg, the muscles showed relatively low trace element concentrations. Squid size was positively correlated to Ag, As, Cd, Hg and Zn concentrations in Tasmanian squid and negatively correlated to all but Hg and Zn concentrations in Île Amsterdam squid. Furthermore, no differences in elemental concentrations were noted between sexes. There were, however, some differences between mated and non-mated females from Tasmania. Comparing elemental concentrations in squid from both islands, higher concentrations of Cd, Co, Cr, Ni, Pb and V in squid sampled in Île Amsterdam reflect different exposure conditions. When considering T. filippovae as a dietary resource for humans it should be noted that, given their Hg content, squids from Île Amsterdam are not recommended for consumption on a regular basis. Moreover, regardless of the squid's origin, digestive glands should be avoided as Cd and Hg concentrations were above the European Union authorized limits in these organs. Copyright © 2011 Elsevier Inc. All rights reserved.

  9. A Linear Decomposition of the Southern Ocean Thermohaline Structure in only two Modes with Application to Frontal Detection

    Science.gov (United States)

    Pauthenet, E.; Roquet, F.; Nerini, D.; Madec, G.

    2016-02-01

    The Southern Ocean is a critical component of the World Ocean as it connects the three major ocean basins. Its thermohaline structure is deeply influenced by the presence of the Antarctic Circumpolar Current (ACC), where water masses of the World Ocean are advected, transformed and redistributed to the other basins. It remains challenging to describe and visualize the complex 3D pattern of this circulation and its associated tracer distribution. Here, we propose an objective method for decomposing the Southern Ocean thermohaline structure. A principal component analysis (PCA, which is a variant of the EOF method) is applied directly on the shape of temperature and salinity profiles to determine the main spatial patterns of their variations. Using the Southern Ocean state estimate (SOSE), we determined the vertical modes describing the Southern Ocean thermohaline structure between 0 and 2000 m. We found that the two first modes explain more than 90% of the combined temperature-salinity variance, thus providing a surprisingly good approximation of the thermohaline properties in the Southern Ocean. The first mode (72% of total variance) describes accurately temperature variations, as well as surface and deep salinity variations. The second mode (20%) mostly improves salinity at 500 m in the region of Antarctic Intermediate Water formation. These two modes present circumpolar patterns that can be closely related with standard frontal definitions, especially for the ACC fronts (Subtropical, Subantarctic, Polar and Southern ACC fronts). By projecting hydrographic profiles on the SOSE-derived modes, it is possible to determine their position relative to the fronts. This provides a new, objective, way to define ACC fronts and spatial variability. The concept is successfully applied on the WOCE-SR3 hydrographic section. This method can also provide a useful metric to compare model outputs with available observations and to better assess heat and salt content changes.

  10. A hierarchical classification of benthic biodiversity and assessment of protected areas in the Southern Ocean.

    Directory of Open Access Journals (Sweden)

    Lucinda L Douglass

    Full Text Available An international effort is underway to establish a representative system of marine protected areas (MPAs in the Southern Ocean to help provide for the long-term conservation of marine biodiversity in the region. Important to this undertaking is knowledge of the distribution of benthic assemblages. Here, our aim is to identify the areas where benthic marine assemblages are likely to differ from each other in the Southern Ocean including near-shore Antarctica. We achieve this by using a hierarchical spatial classification of ecoregions, bathomes and environmental types. Ecoregions are defined according to available data on biogeographic patterns and environmental drivers on dispersal. Bathomes are identified according to depth strata defined by species distributions. Environmental types are uniquely classified according to the geomorphic features found within the bathomes in each ecoregion. We identified 23 ecoregions and nine bathomes. From a set of 28 types of geomorphic features of the seabed, 562 unique environmental types were classified for the Southern Ocean. We applied the environmental types as surrogates of different assemblages of biodiversity to assess the representativeness of existing MPAs. We found that 12 ecoregions are not represented in MPAs and that no ecoregion has their full range of environmental types represented in MPAs. Current MPA planning processes, if implemented, will substantially increase the representation of environmental types particularly within 8 ecoregions. To meet internationally agreed conservation goals, additional MPAs will be needed. To assist with this process, we identified 107 spatially restricted environmental types, which should be considered for inclusion in future MPAs. Detailed supplementary data including a spatial dataset are provided.

  11. Regional differences in plastic ingestion among Southern Ocean fur seals and albatrosses.

    Science.gov (United States)

    Ryan, Peter G; de Bruyn, P J Nico; Bester, Marthán N

    2016-03-15

    We provide data on regional differences in plastic ingestion for two Southern Ocean top predators: Arctocephalus fur seals and albatrosses (Diomedeidae). Fur seals breeding on Macquarie Island in the 1990s excreted small (mainly 2-5 mm) plastic fragments, probably derived secondarily from myctophid fish. No plastic was found in the scats of these seals breeding on three islands in the southwest Indian and central South Atlantic Oceans, despite myctophids dominating their diets at these locations. Compared to recent reports of plastic ingestion by albatrosses off the east coast of South America, we confirm that plastic is seldom found in the stomachs of Thalassarche albatrosses off South Africa, but found no Diomedea albatrosses to contain plastic, compared to 26% off South America. The reasons for such regional differences are unclear, but emphasize the importance of reporting negative as well as positive records of plastic ingestion by marine biota. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. The role of atmospheric greenhouse gases, orbital parameters, and southern ocean gateways: an idealized model study

    CERN Document Server

    Hertwig, Eileen; Fraedrich, Klaus

    2016-01-01

    A set of idealized experiments are performed to analyze the competing effects of declining atmospheric CO2 concentrations, the opening of an ocean gateway, and varying orbital parameters. These forcing mechanisms, which influence the global mean climate state, may have played a role for triggering climate transitions of the past (for example during the Eocene-Oligocene climate transition and the build-up of the Antarctic Ice Sheet). Sensitivity simulations with a coupled atmosphere-ocean general circulation model are conducted to test these three forcings and their roles for the global climate. The simulations are carried out under idealized conditions to focus on the essentials. The combination of all three forcings triggers a climate transition which resembles the onset of the Antarctic glaciation. In particular, the temperatures in the southern high latitudes decrease and snow accumulates constantly. Moreover, the relative importance of each possible forcing is explored. All three of the mechanisms (atmosp...

  13. Southern Ocean areas of endemism: a reanalysis using benthic hydroids (Cnidaria, Hydrozoa

    Directory of Open Access Journals (Sweden)

    Thaís P Miranda

    2013-11-01

    Full Text Available The biogeographic history of the Southern Ocean (SO fauna is complex and poorly studied, especially the areas of endemism. We reanalyzed the data of Marques & Peña Cantero (2010, along with other geographical records of endemic benthic hydroids below 45°S. A Parsimony Analysis of Endemicity (PAE based on 5° latitude by 5° longitude matrix with 61 species resulted in eight areas of endemism. We discuss these results in the context of different hypotheses of the evolution of the SO fauna and previously proposed biogeography patterns.

  14. Long-Term Relationships between the Marine Environment, Krill and Salps in the Southern Ocean

    OpenAIRE

    Lee, Chung Il; Pakhomov, Evgeny; Atkinson,Angus; Siegel,Volker

    2010-01-01

    Long-term variations (1975–2002) in climatology of marine environmental parameters, Antarctic krill, Euphausia superba, and the pelagic tunicate, Salpa thompsoni, were compared within the Atlantic Sector of the Southern Ocean. Sea water temperature in the top 400 m increased at a rate of 0.020–0.030°C ⋅ yr−1, which was accompanied by the dissolved oxygen decline. Top 100 m water layer became fresher with lower concentrations of phosphates and nitrates, while at subsurface layers (200–400 m) b...

  15. Heavy metals in some parts of Antarctica and the southern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Kureishy, T.W.; Sengupta, R.; Mesquita, A.; Sanzgiri, S.

    11/November 1993 Marine Polhaion Bulletin, Volume 26, No. I 1, pp. 651-652, 1993. Printed in Great Britain, 0025-326X/93 $6.00+0.00 © 1993 Pergamon Press Ltd Heavy Metals in Some Parts of Antarctica and the Southern Indian Ocean TARIQ W...(}ha, Qatar Though remote in its geographical location Antarctica is known to be indirectly affected by industrial and agricultural activities on other continents. This is evident in the concentrations of synthetic chemicals such as the organochlorine...

  16. Oceanography and the base of the pelagic food web in the southern Indian Ocean

    DEFF Research Database (Denmark)

    Visser, Andre; Nielsen, Torkel Gissel; Middelboe, Mathias

    2015-01-01

    Processes governing productivity at the base of the pelagic food web of the southern Indian Ocean are influenced primarily by physical–chemical conditions with implications for the structure and function of the entire pelagic food web. Here, we report observations along a great circle transect from...... Cape Town, South Africa, to Broome in north western Australia. Primary production was tightly linked to water column stability and nutrient availability, with high productivity (1144 mg C m22 day21) in the sub-tropical convergence zone, and falling off by an order of magnitude in the sub-tropical gyre...

  17. Malacological survey in Phang-Nga Province, southern Thailand, pre- and post-Indian Ocean tsunami.

    Science.gov (United States)

    Sri-Aroon, Pusadee; Lohachit, Chantima; Harada, Masakazu; Chusongsang, Phiraphol; Chusongsang, Yupa

    2006-01-01

    Three malacological surveys were conducted in the Takua Pa District of Phang-Nga Province, southern Thailand, before and after the Indian Ocean Tsunami disaster. Twenty-nine species of fresh- and brackish-water snails were found, in which 10 species of freshwater snails were present, including live Pila polita; 8 species were of medical importance. Two brackish-water snails, Nerita articulata and Littorinopsis scabra, were absent after the tsunami disaster, while brackish-water Cerithidea cingulata and C. djadjariensis harbored 9 types of trematode cercariae.

  18. Climate change and Southern Ocean ecosystems I: how changes in physical habitats directly affect marine biota.

    Science.gov (United States)

    Constable, Andrew J; Melbourne-Thomas, Jessica; Corney, Stuart P; Arrigo, Kevin R; Barbraud, Christophe; Barnes, David K A; Bindoff, Nathaniel L; Boyd, Philip W; Brandt, Angelika; Costa, Daniel P; Davidson, Andrew T; Ducklow, Hugh W; Emmerson, Louise; Fukuchi, Mitsuo; Gutt, Julian; Hindell, Mark A; Hofmann, Eileen E; Hosie, Graham W; Iida, Takahiro; Jacob, Sarah; Johnston, Nadine M; Kawaguchi, So; Kokubun, Nobuo; Koubbi, Philippe; Lea, Mary-Anne; Makhado, Azwianewi; Massom, Rob A; Meiners, Klaus; Meredith, Michael P; Murphy, Eugene J; Nicol, Stephen; Reid, Keith; Richerson, Kate; Riddle, Martin J; Rintoul, Stephen R; Smith, Walker O; Southwell, Colin; Stark, Jonathon S; Sumner, Michael; Swadling, Kerrie M; Takahashi, Kunio T; Trathan, Phil N; Welsford, Dirk C; Weimerskirch, Henri; Westwood, Karen J; Wienecke, Barbara C; Wolf-Gladrow, Dieter; Wright, Simon W; Xavier, Jose C; Ziegler, Philippe

    2014-10-01

    Antarctic and Southern Ocean (ASO) marine ecosystems have been changing for at least the last 30 years, including in response to increasing ocean temperatures and changes in the extent and seasonality of sea ice; the magnitude and direction of these changes differ between regions around Antarctica that could see populations of the same species changing differently in different regions. This article reviews current and expected changes in ASO physical habitats in response to climate change. It then reviews how these changes may impact the autecology of marine biota of this polar region: microbes, zooplankton, salps, Antarctic krill, fish, cephalopods, marine mammals, seabirds, and benthos. The general prognosis for ASO marine habitats is for an overall warming and freshening, strengthening of westerly winds, with a potential pole-ward movement of those winds and the frontal systems, and an increase in ocean eddy activity. Many habitat parameters will have regionally specific changes, particularly relating to sea ice characteristics and seasonal dynamics. Lower trophic levels are expected to move south as the ocean conditions in which they are currently found move pole-ward. For Antarctic krill and finfish, the latitudinal breadth of their range will depend on their tolerance of warming oceans and changes to productivity. Ocean acidification is a concern not only for calcifying organisms but also for crustaceans such as Antarctic krill; it is also likely to be the most important change in benthic habitats over the coming century. For marine mammals and birds, the expected changes primarily relate to their flexibility in moving to alternative locations for food and the energetic cost of longer or more complex foraging trips for those that are bound to breeding colonies. Few species are sufficiently well studied to make comprehensive species-specific vulnerability assessments possible. Priorities for future work are discussed. © 2014 John Wiley & Sons Ltd.

  19. Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4

    Science.gov (United States)

    Heuzé, C.; Ridley, J. K.; Calvert, D.; Stevens, D. P.; Heywood, K. J.

    2015-10-01

    Most CMIP5 (Coupled Model Intercomparison Project Phase 5) models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross seas. To identify the mechanisms triggering Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean model NEMO3.4 forced by prescribed atmospheric fluxes. We vary the vertical velocity scale of the Langmuir turbulence, the fraction of turbulent kinetic energy transferred below the mixed layer, and the background diffusivity and run short simulations from 1980. All experiments exhibit deep convection in the Riiser-Larsen Sea in 1987; the origin is a positive sea ice anomaly in 1985, causing a shallow anomaly in mixed layer depth, hence anomalously warm surface waters and subsequent polynya opening. Modifying the vertical mixing impacts both the climatological state and the associated surface anomalies. The experiments with enhanced mixing exhibit colder surface waters and reduced deep convection. The experiments with decreased mixing give warmer surface waters, open larger polynyas causing more saline surface waters and have deep convection across the Weddell Sea until the simulations end. Extended experiments reveal an increase in the Drake Passage transport of 4 Sv each year deep convection occurs, leading to an unrealistically large transport at the end of the simulation. North Atlantic deep convection is not significantly affected by the changes in mixing parameters. As new climate model overflow parameterisations are developed to form Antarctic Bottom Water more realistically, we argue that models would benefit from stopping Southern Ocean deep convection, for example by increasing their vertical mixing.

  20. Temperature, salinity profiles and associated data collected in the Southern Oceans in support of the Global Ocean Ecosystem Dynamics project, 2001-04 to 2001-08 (NODC Accession 0001097)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The overall goal of the U.S. Southern Ocean GLOBEC program is to elucidate circulation processes and their effect on sea ice formation and Antarctic krill (Euphausia...

  1. Ventilation of the abyssal Southern Ocean during the late Neogene: A new perspective from the subantarctic Pacific

    Science.gov (United States)

    Waddell, Lindsey M.; Hendy, Ingrid L.; Moore, Theodore C.; Lyle, Mitchell W.

    2009-09-01

    Benthic foraminiferal stable carbon isotope records from the South Atlantic show significant declines toward more "Pacific-like" values at ˜7 and ˜2.7 Ma, and it has been posited that these shifts may mark steps toward increased CO2 sequestration in the deep Southern Ocean as climate cooled over the late Neogene. We generated new stable isotope records from abyssal subantarctic Pacific cores MV0502-4JC and ELT 25-11. The record from MV0502-4JC suggests that the Southern Ocean remained well mixed and free of vertical or interbasinal δ13C gradients following the late Miocene carbon shift (LMCS). According to the records from MV0502-4JC and ELT 25-11, however, cold, low δ13C bottom waters developed in the Southern Ocean in the late Pliocene and persisted until ˜1.7 Ma. These new data suggest that while conditions in the abyssal Southern Ocean following the LMCS were comparable to the present day, sequestration of respired CO2 may have increased in the deepest parts of the Southern Ocean during the late Pliocene, a critical period for the growth and establishment of the Northern Hemisphere ice sheets.

  2. Developing integrated models of Southern Ocean food webs: Including ecological complexity, accounting for uncertainty and the importance of scale

    Science.gov (United States)

    Murphy, E. J.; Cavanagh, R. D.; Hofmann, E. E.; Hill, S. L.; Constable, A. J.; Costa, D. P.; Pinkerton, M. H.; Johnston, N. M.; Trathan, P. N.; Klinck, J. M.; Wolf-Gladrow, D. A.; Daly, K. L.; Maury, O.; Doney, S. C.

    2012-09-01

    The Southern Ocean supports diverse and unique ecosystems that have been impacted by more than two centuries of exploitation and are now experiencing rapid changes in ocean temperature and seasonal ice cover due to climate warming. Understanding and projecting responses of Southern Ocean marine ecosystems to changing climate conditions and direct human impacts, such as fisheries, requires integrated ecosystem analyses at scales previously unexplored. Here we consider the main ecological and modelling challenges in predicting the responses of Southern Ocean ecosystems to change, and propose three interlinked focus areas that will advance the development of integrated models for Southern Ocean ecosystems. The first focus area is development of fundamental understanding of the factors that determine the structure and function of the food webs at multiple scales. Ecological research in the Southern Ocean is often centred on key species or localised systems, a tendency which is reflected in existing food web and ecosystem models. To build on this, a systematic analysis of regional food web structure and function is required. The second focus area is development of a range of mechanistic models that vary in their resolution of ecological processes, and consider links across physical scales, biogeochemical cycles and feedbacks, and the central role of zooplankton. These two focus areas underlie the third, which is development of methodologies for scenario testing across a range of trophic levels of the effects of past and future changes, which will facilitate consideration of the underlying complexity of interactions and the associated uncertainty. The complex nature of interactions determining Southern Ocean ecosystem structure and function will require new approaches, which we propose should be developed within a scale-based framework that emphasises both physical and ecological aspects.

  3. CLOUDS, AEROSOLS, RADIATION AND THE AIR-SEA INTERFACE OF THE SOUTHERN OCEAN: ESTABLISHING DIRECTIONS FOR FUTURE RESEARCH

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Robert [University of Washington; Bretherton, Chris [University of Washington; McFarquhar, Greg [University of Illinois - Urbana; Protat, Alain [Bureau of Meteorology - Melbourne; Quinn, Patricia [NOAA PMEL; Siems, Steven [Monash Univ., Melbourne, VIC (Australia); Jakob, Christian [Monash Univ., Melbourne, VIC (Australia); Alexander, Simon [Australian Antarctic Division; Weller, Bob [Woods Hole Oceanographic Institute

    2014-09-29

    A workshop sponsored by the Department of Energy was convened at the University of Washington to discuss the state of knowledge of clouds, aerosols and air-sea interaction over the Southern Ocean and to identify strategies for reducing uncertainties in their representation in global and regional models. The Southern Ocean plays a critical role in the global climate system and is a unique pristine environment, yet other than from satellite, there have been sparse observations of clouds, aerosols, radiation and the air-sea interface in this region. Consequently, much is unknown about atmospheric and oceanographic processes and their linkage in this region. Approximately 60 scientists, including graduate students, postdoctoral fellows and senior researchers working in atmospheric and oceanic sciences at U.S. and foreign universities and government laboratories, attended the Southern Ocean Workshop. It began with a day of scientific talks, partly in plenary and partly in two parallel sessions, discussing the current state of the science for clouds, aerosols and air-sea interaction in the Southern Ocean. After the talks, attendees broke into two working groups; one focused on clouds and meteorology, and one focused on aerosols and their interactions with clouds. This was followed by more plenary discussion to synthesize the two working group discussions and to consider possible plans for organized activities to study clouds, aerosols and the air-sea interface in the Southern Ocean. The agenda and talk slides, including short summaries of the highlights of the parallel session talks developed by the session chars, are available at http://www.atmos.washington.edu/socrates/presentations/SouthernOceanPresentations/.

  4. Southern Oceans Near Real-Time Temperature Profile Data from the GTSPP project from 01 January 2001 to 31 December 2001 (NODC Accession 0000921)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical data were collected from XBT casts from the Southern Oceans (> 60 degrees South). Data were collected from 01 January 2001 to 31 December 2001. Data were...

  5. Southern Oceans Near Real-Time Temperature Profile Data from the GTSPP project from 01 January 2002 to 31 December 2002 (NODC Accession 0000956)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical data were collected from XBT casts from the Southern Oceans (> 60 degrees South). Data were collected from 01 January 2002 to 31 December 2002. Data were...

  6. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Southern Oceans from 02 January 1990 to 05 February 1990 (NODC Accession 0000887)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Southern Oceans from the POLAR DUKE. Data were collected from 02 January 1990 to 05...

  7. NODC Standard Product: US Navy Geosat geophysical data records (GDRs) from the Southern Ocean 30-72 degrees south (2 disc set) (NODC Accession 9000189)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains U.S. Navy Geodetic Satellite (GEOSAT) Geophysical data records from the Southern Oceans 60 to 70 degrees south. March 31, 1985 to September...

  8. The distribution of the standing crop of zooplankton in the Southern Ocean, 02 January 1932 to 18 October 1951 (NODC Accession 0000842)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton data were collected using net casts in the Southern Ocean from the DISCOVERY II. Data were collected from 02 January 1932 to 18 October 1951. Data were...

  9. Zooplankton data collected by ELTANIN in Southern Oceans from zooplankton net casts; 13 October 1963 to 06 June 1968 (NODC Accession 9500111)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton data were collected using zooplankton net casts from ELTANIN in the Southern Oceans. Data were collected from 13 October 1963 to 06 June 1968 by National...

  10. Salp/krill interactions in the Southern Ocean: spatial segregation and implications for the carbon flux

    Science.gov (United States)

    Pakhomov, E. A.; Froneman, P. W.; Perissinotto, R.

    Available data on the spatial distribution and feeding ecophysiology of Antarctic krill, Euphausia superba, and the tunicate, Salpa thompsoni, in the Southern Ocean are summarized in this study. Antarctic krill and salps generally display pronounced spatial segregation at all spatial scales. This appears to be the result of a clear biotopical separation of these key species in the Antarctic pelagic food web. Krill and salps are found in different water masses or water mass modifications, which are separated by primary or secondary frontal features. On the small-scale (salps are usually restricted to the specific water parcels, or are well segregated vertically. Krill and salp grazing rates estimated using the in situ gut fluorescence technique are among the highest recorded in the Antarctic pelagic food web. Although krill and salps at times may remove the entire daily primary production, generally their grazing impact is moderate (⩽50% of primary production). The regional ecological consequences of years of high salp densities may be dramatic. If the warming trend, which is observed around the Antarctic Peninsula and in the Southern Ocean, continues, salps may become a more prominent player in the trophic structure of the Antarctic marine ecosystem. This likely would be coupled with a dramatic decrease in krill productivity, because of a parallel decrease in the spatial extension of the krill biotope. The high Antarctic regions, particularly the Marginal Ice Zone, have, however, effective physiological mechanisms that may provide protection against the salp invasion.

  11. Year-round observations of carbon biomass and flux variability in the Southern Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, James K.B.; Wood, Todd

    2009-02-01

    Three Carbon Explorer (CE) floats profiling to kilometer depths in the Southern Ocean tracked dawn-dusk variations of mixing/stratification, particulate organic carbon (POC), and light scattering and sedimentation at 100, 250, and 800 m continuously from January 2002 to April 2003. Data were analyzed in conjunction with contemporaneous satellite winds and chlorophyll and derived subsurface light fields. The CE deployed at 66{sup o}S 172{sup o}W operated in the ice edge zone in absence of light. Two CEs deployed at 55{sup o}S 172{sup o}W recorded wintertime mixing to {approx}400 m, yet observed very different bloom dynamics and sedimentation the following spring. Four hypotheses are explored. The strongest is that shallow transient stratification of the deep winter mixed layer to shallower than photosynthetic critical depth occurred more frequently in the non-bloom/higher sedimentation case. The lower particle export to 800 m under the bloom was hypothesized to be due to higher interception of sinking carbon by a relatively starved over wintering zooplankton population. In the Southern Ocean surface phytoplankton biomass may counter indicate particle flux at kilometer depths.

  12. Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo.

    Science.gov (United States)

    McCoy, Daniel T; Burrows, Susannah M; Wood, Robert; Grosvenor, Daniel P; Elliott, Scott M; Ma, Po-Lun; Rasch, Phillip J; Hartmann, Dennis L

    2015-07-01

    Atmospheric aerosols, suspended solid and liquid particles, act as nucleation sites for cloud drop formation, affecting clouds and cloud properties-ultimately influencing the cloud dynamics, lifetime, water path, and areal extent that determine the reflectivity (albedo) of clouds. The concentration N d of droplets in clouds that influences planetary albedo is sensitive to the availability of aerosol particles on which the droplets form. Natural aerosol concentrations affect not only cloud properties themselves but also modulate the sensitivity of clouds to changes in anthropogenic aerosols. It is shown that modeled natural aerosols, principally marine biogenic primary and secondary aerosol sources, explain more than half of the spatiotemporal variability in satellite-observed N d. Enhanced N d is spatially correlated with regions of high chlorophyll a, and the spatiotemporal variability in N d is found to be driven primarily by high concentrations of sulfate aerosol at lower Southern Ocean latitudes (35(o) to 45(o)S) and by organic matter in sea spray aerosol at higher latitudes (45(o) to 55(o)S). Biogenic sources are estimated to increase the summertime mean reflected solar radiation in excess of 10 W m(-2) over parts of the Southern Ocean, which is comparable to the annual mean increases expected from anthropogenic aerosols over heavily polluted regions of the Northern Hemisphere.

  13. How Does the Antarctic Circumpolar Current Affect the Southern Ocean Meridional Overturning Circulation?

    Science.gov (United States)

    Chapman, Christopher; Sallée, Jean-Baptiste

    2017-04-01

    The Meridional Overturning Circulation (MOC) in the Southern Ocean is investigated using hydrographic observations combined with satellite observations of sea-surface height. A three-dimensional (spatial and vertical) estimate of the isopycnal eddy-diffusivity in the Southern Ocean is obtained using the theory of Ferrari & Nikurashin (2010), that includes the influence of suppression of the diffusivity by the strong, time-mean flows. It is found that the eddy diffusivity is enhanced at depth, reaching a maximum at the "critical layer" near 1000m. The estimate of diffusivity is used with a simple diffusive parameterization to estimate the meridional eddy volume flux. Together with an estimate of the meridional Ekman transport and the time-mean meridional geostrophic transport, the eddy volume flux is used to reconstruct the time-mean overturning circulation. By comparing the reconstruction with, and without, suppression of the eddy diffusivity by the mean flow, the influence of the suppression on the overturning is illuminated. It is shown that the suppression of the eddy diffusivity results in a large reduction of interior eddy transports, and a more realistic eddy induced overturning circulation. We will also use a simple conceptual model is used to show that the MOC is influenced not only by the existence of enhanced diffusivity at depth, but also by the details of the vertical structure of the eddy diffusivity, such as the depth of the critical layer.

  14. The Radiative Impacts of Precipitating Ice on Arctic and Southern Ocean Sea Ice Simulations in GCMs

    Science.gov (United States)

    Li, J. L. F.; Hong, Y.; Lee, W. L.; Wang, Y. H.; Liu, Y.; Richardson, M.; Yu, J. Y.; Suhas, E.; Fetzer, E. J.; Liu, G.

    2016-12-01

    Using the NCAR-CESM1 model and observations we show that a bias in sea-ice concentration is attributable to erroneous cloud-radiative interaction associated with the exclusion of downwelling long-wave heating from precipitating ice over Arctic and Southern Oceans. These biases resemble those in CMIP5 models which commonly exclude the radiative effects of precipitating ice. This missing radiative effects, in conjunction with overestimated surface albedo, leads to colder surface temperatures (TS), near surface-air temperatures (SAT) and the associated surface energy-budget adjustments. These biases in turn increases the sea-ice concentration in Arctic and Southern Oceans. The inclusion of the precipitating ice radiative effects reduces the negative model biases in surface radiative fluxes by more than 20 W m-2, TS and SAT by 2—4 K and positive sea-ice concentration by 30—40%, leading to a more realistic seasonal cycle compared with simulations lacking the snow-radiative effects. The findings have implications to the simulation of projection of changes associated with sea-ice in CMIP models.

  15. Dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from POLARSTERN in the Indian Ocean, South Atlantic Ocean and Southern Oceans from 2002-11-24 to 2003-01-23 (NODC Accession 0108068)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108068 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the Indian Ocean, South Atlantic Ocean and Southern...

  16. Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from NATHANIEL B. PALMER in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-02-19 to 2011-04-23 (NODC Accession 0109933)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0109933 includes discrete sample and profile data collected from NATHANIEL B. PALMER in the South Atlantic Ocean, South Pacific Ocean and Southern...

  17. Enhanced productivity rather than enhanced preservation led to increased organic carbon burial in the euxinic southern proto North Atlantic Ocean during the Cenomanian/Turonian Oceanic Anoxic Event

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Kuypers, M.M.M.; Pancost, R.D.; Nijenhuis, I.A.

    2002-01-01

    Three Cenomanian/Turonian (C/T, ∼93.5 Ma) black shale sections along a northeast-southwest transect in the southern part of the proto-North Atlantic Ocean were correlated by stable carbon isotope stratigraphy using the characteristic excursion in δ¹³C values of both bulk organic matter (OM) and

  18. Seasonal and geographic variation of southern blue whale subspecies in the Indian Ocean.

    Science.gov (United States)

    Samaran, Flore; Stafford, Kathleen M; Branch, Trevor A; Gedamke, Jason; Royer, Jean-Yves; Dziak, Robert P; Guinet, Christophe

    2013-01-01

    Understanding the seasonal movements and distribution patterns of migratory species over ocean basin scales is vital for appropriate conservation and management measures. However, assessing populations over remote regions is challenging, particularly if they are rare. Blue whales (Balaenoptera musculus spp) are an endangered species found in the Southern and Indian Oceans. Here two recognized subspecies of blue whales and, based on passive acoustic monitoring, four "acoustic populations" occur. Three of these are pygmy blue whale (B.m. brevicauda) populations while the fourth is the Antarctic blue whale (B.m. intermedia). Past whaling catches have dramatically reduced their numbers but recent acoustic recordings show that these oceans are still important habitat for blue whales. Presently little is known about the seasonal movements and degree of overlap of these four populations, particularly in the central Indian Ocean. We examined the geographic and seasonal occurrence of different blue whale acoustic populations using one year of passive acoustic recording from three sites located at different latitudes in the Indian Ocean. The vocalizations of the different blue whale subspecies and acoustic populations were recorded seasonally in different regions. For some call types and locations, there was spatial and temporal overlap, particularly between Antarctic and different pygmy blue whale acoustic populations. Except on the southernmost hydrophone, all three pygmy blue whale acoustic populations were found at different sites or during different seasons, which further suggests that these populations are generally geographically distinct. This unusual blue whale diversity in sub-Antarctic and sub-tropical waters indicates the importance of the area for blue whales in these former whaling grounds.

  19. Seasonal and geographic variation of southern blue whale subspecies in the Indian Ocean.

    Directory of Open Access Journals (Sweden)

    Flore Samaran

    Full Text Available Understanding the seasonal movements and distribution patterns of migratory species over ocean basin scales is vital for appropriate conservation and management measures. However, assessing populations over remote regions is challenging, particularly if they are rare. Blue whales (Balaenoptera musculus spp are an endangered species found in the Southern and Indian Oceans. Here two recognized subspecies of blue whales and, based on passive acoustic monitoring, four "acoustic populations" occur. Three of these are pygmy blue whale (B.m. brevicauda populations while the fourth is the Antarctic blue whale (B.m. intermedia. Past whaling catches have dramatically reduced their numbers but recent acoustic recordings show that these oceans are still important habitat for blue whales. Presently little is known about the seasonal movements and degree of overlap of these four populations, particularly in the central Indian Ocean. We examined the geographic and seasonal occurrence of different blue whale acoustic populations using one year of passive acoustic recording from three sites located at different latitudes in the Indian Ocean. The vocalizations of the different blue whale subspecies and acoustic populations were recorded seasonally in different regions. For some call types and locations, there was spatial and temporal overlap, particularly between Antarctic and different pygmy blue whale acoustic populations. Except on the southernmost hydrophone, all three pygmy blue whale acoustic populations were found at different sites or during different seasons, which further suggests that these populations are generally geographically distinct. This unusual blue whale diversity in sub-Antarctic and sub-tropical waters indicates the importance of the area for blue whales in these former whaling grounds.

  20. Fluxes of biogenic carbon in the Southern Ocean: roles of large microphagous zooplankton1

    Science.gov (United States)

    Le Fèvre, Jacques; Legendre, Louis; Rivkin, Richard B.

    1998-11-01

    The Southern Ocean is an extreme environment, where waters are permanently cold, a seasonal ice cover extends over large areas, and the solar energy available for photosynthesis is severely restricted, either by vertical mixing to considerable depths or, especially south of the Antarctic Circle, by prolonged seasonal periods of low or no irradiance. Such conditions would normally lead to low productivity and a water column dominated by recycling processes involving microbial components of pelagic communities but this does not seem to be the case in the Southern Ocean, where there is efficient export to large apex predators and deep waters. This paper investigates the role of large microphagous zooplankton (salps, krill, and some large copepods) in the partitioning of biogenic carbon among the pools of short- and long-lived organic carbon and sequestered biogenic carbon. Large microphagous zooplankton are able to ingest microbial-sized particles and thus repackage small, non-sinking particles into both metazoan biomass and large, rapidly sinking faeces. Given the wide spatio-temporal extent of microbial trophic pathways in the Southern Ocean, large zooplankton that are omnivorous or able to ingest small food particles have a competitive advantage over herbivorous zooplankton. Krill efficiently transfer carbon to a wide array of apex predators and their faecal pellets are exported to depth during occasional brief sedimentation episodes in spring time. Salps may be a significant link towards some fish (directly) and other apex predators (indirectly) and, at some locations (especially in offshore waters) and time, they may account for most of the downward flux of biogenic carbon. Large copepods are a trophic link towards fish and at least one whale species, and their grazing activity generally impedes the export of organic particles to depth. As a result, biogenic carbon is channelled mainly towards apex predators and episodically into the deep ocean. Without these

  1. Trace Gas Distributions and Correlations Observed In The Southern Ocean Atmosphere During the ORCAS Mission

    Science.gov (United States)

    Atlas, E. L.; Schauffler, S.; Donets, V.; Apel, E. C.; Hornbrook, R. S.; Hills, A. J.; Stephens, B. B.; Kort, E. A.; Sweeney, C.; Gierach, M.

    2016-12-01

    The biologically productive waters of the Southern Ocean are potentially a significant source and sink for trace gases that impact atmospheric chemistry and climate. However, relatively little is known about the variations and atmospheric vertical structures of trace gases in this region. During January/February, 2016, we participated in the O2/N2 Ratio and CO2 Airborne Southern Ocean (ORCAS) Study, an airborne mission that included the measurement of a wide range of trace gases. This presentation will focus on a selection of gases measured from the Whole Air Sampler and from an in-situ GC/MS system (TOGA). The gases measured by these instruments included a range of reactive halocarbons produced by marine organisms in the surface ocean (e.g., dimethyl sulfide, bromoform, methyl iodide), produced from marine surface photochemistry (e.g., methyl nitrate), and introduced to the region from long-range transport (e.g., chlorinated solvents, CFCs and HCFCs, non-methane hydrocarbons). Distributions of these gases should reflect the biological productivity of the region, the surface flux rates, and the rates of atmospheric transport and mixing. The concentrations of biogenic trace gases that we measured in the marine boundary layer showed significant regional differences in concentrations and different seasonal changes over the course of the experiment. Vertical profiles of biogenic trace gases could be related to the surface sources, exchange with the free troposphere, and the photochemical lifetime of the different gases. Because of the potential relationship of biogenic trace gases to biological productivity in the surface ocean, the measurements will be compared to distributions of chlorophyll a, as observed remotely from the GV aircraft and from satellites. For trace gases with a large interhemispheric gradient and primarily northern hemisphere source (e.g. mainly anthropogenic sources), atmospheric vertical profiles showed an average increase in mixing ratio with

  2. Penguins as bioindicators of mercury contamination in the southern Indian Ocean: geographical and temporal trends.

    Science.gov (United States)

    Carravieri, Alice; Cherel, Yves; Jaeger, Audrey; Churlaud, Carine; Bustamante, Paco

    2016-06-01

    Penguins have been recently identified as useful bioindicators of mercury (Hg) transfer to food webs in the Southern Ocean over different spatial and temporal scales. Here, feather Hg concentrations were measured in adults and chicks of all the seven penguin species breeding in the southern Indian Ocean, over a large latitudinal gradient spanning Antarctic, subantarctic and subtropical sites. Hg was also measured in feathers of museum specimens of penguins collected at the same sites in the 1950s and 1970s. Our aim was to evaluate geographical and historical variations in Hg transfer to penguins, while accounting for feeding habits by using the stable isotope technique (δ(13)C, habitat; δ(15)N, diet/trophic level). Adult feather Hg concentrations in contemporary individuals ranged from 0.7 ± 0.2 to 5.9 ± 1.9 μg g(-1) dw in Adélie and gentoo penguins, respectively. Inter-specific differences in Hg accumulation were strong among both adults and chicks, and mainly linked to feeding habits. Overall, penguin species that feed in Antarctic waters had lower feather Hg concentrations than those that feed in subantarctic and subtropical waters, irrespective of age class and dietary group, suggesting different Hg incorporation into food webs depending on the water mass. While accounting for feeding habits, we detected different temporal variations in feather Hg concentrations depending on species. Notably, the subantarctic gentoo and macaroni penguins had higher Hg burdens in the contemporary rather than in the historical sample, despite similar or lower trophic levels, respectively. Whereas increases in Hg deposition have been recently documented in the Southern Hemisphere, future monitoring is highly needed to confirm or not this temporal trend in penguins, especially in the context of actual changing Hg emission patterns and global warming. Copyright © 2016. Published by Elsevier Ltd.

  3. The past, present and future distribution of a deep-sea shrimp in the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Zeenatul Basher

    2016-02-01

    Full Text Available Shrimps have a widespread distribution across the shelf, slope and seamount regions of the Southern Ocean. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity and adaptability in response to environmental change. We use species distribution models to predict changes in the geographic range of the deep-sea Antarctic shrimp Nematocarcinus lanceopes under changing climatic conditions from the Last Glacial Maximum to the present and to the year 2100. The present distribution range indicates a pole-ward shift of the shrimp population since the last glaciation. This occurred by colonization of slopes from nearby refugia located around the northern part of Scotia Arc, southern tip of South America, South Georgia, Bouvet Island, southern tip of the Campbell plateau and Kerguelen plateau. By 2100, the shrimp are likely to expand their distribution in east Antarctica but have a continued pole-ward contraction in west Antarctica. The range extension and contraction process followed by the deep-sea shrimp provide a geographic context of how other deep-sea Antarctic species may have survived during the last glaciation and may endure with projected changing climatic conditions in the future.

  4. The past, present and future distribution of a deep-sea shrimp in the Southern Ocean.

    Science.gov (United States)

    Basher, Zeenatul; Costello, Mark J

    2016-01-01

    Shrimps have a widespread distribution across the shelf, slope and seamount regions of the Southern Ocean. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity and adaptability in response to environmental change. We use species distribution models to predict changes in the geographic range of the deep-sea Antarctic shrimp Nematocarcinus lanceopes under changing climatic conditions from the Last Glacial Maximum to the present and to the year 2100. The present distribution range indicates a pole-ward shift of the shrimp population since the last glaciation. This occurred by colonization of slopes from nearby refugia located around the northern part of Scotia Arc, southern tip of South America, South Georgia, Bouvet Island, southern tip of the Campbell plateau and Kerguelen plateau. By 2100, the shrimp are likely to expand their distribution in east Antarctica but have a continued pole-ward contraction in west Antarctica. The range extension and contraction process followed by the deep-sea shrimp provide a geographic context of how other deep-sea Antarctic species may have survived during the last glaciation and may endure with projected changing climatic conditions in the future.

  5. Distribution and abundance of marine microbes in the Southern Ocean between 30 and 80°E

    Science.gov (United States)

    Thomson, Paul G.; Davidson, Andrew T.; van den Enden, Rick; Pearce, Imojen; Seuront, Laurent; Paterson, James S.; Williams, Guy D.

    2010-05-01

    Our study, as part of the Baseline Research on Oceanography, Krill and the Environment, West (BROKE-West) survey, emphasised the vital role of sea-ice retreat and upwelling in controlling the distribution, abundance and composition of marine microbial communities in the seasonal ice zone (SIZ). Autofluorescence or stains were used to detect the abundance of nanophytoplankton, heterotrophic nanoflagellates (HNF), virus like particles (VLP) and bacteria by flow cytometry. Correlations among microbial concentrations were determined and cluster analysis was performed to group sites of similar microbial composition and abundance. Distance to sea ice was the primary determinant of nanophytoplankton abundance and nanophytoplankton contributed up to 84% of the phytoplankton carbon biomass where melting sea ice caused shallow summer mixed layer depths. To the north, nanophytoplankton abundance was generally low except adjacent to the Southern Boundary (SB). HNF and bacterial abundance was positively correlated with the abundance of nanophytoplankton. Cluster analysis identified 5 groups of sites over the BROKE-West survey area. Clusters 1-4 grouped sites of different successional maturity of the microbial community along the continuum between bloom formation and senescence. Maturity increased with distance from the sea ice and, in areas of upwelling, with time since the development of phytoplankton blooms. Sites in cluster 5 occurred at the northernmost extreme of the survey area and were typical of communities in high nutrient low chlorophyll (HNLC) waters of the permanent open-ocean zone (POOZ) where phytoplankton growth was matched by mortality and decomposition. Synoptic-scale studies in Antarctic waters are rare but provide vital information about the control of microbial productivity, abundance and distribution in the Southern Ocean. Our study, covering over 40% of the SIZ off East Antarctica, enhances our understanding of the synoptic-scale factors that determine the

  6. Effects of whaling on the structure of the Southern Ocean food web: insights on the "krill surplus" from ecosystem modelling.

    Directory of Open Access Journals (Sweden)

    Szymon Surma

    Full Text Available The aim of this study was to examine the ecological plausibility of the "krill surplus" hypothesis and the effects of whaling on the Southern Ocean food web using mass-balance ecosystem modelling. The depletion trajectory and unexploited biomass of each rorqual population in the Antarctic was reconstructed using yearly catch records and a set of species-specific surplus production models. The resulting estimates of the unexploited biomass of Antarctic rorquals were used to construct an Ecopath model of the Southern Ocean food web existing in 1900. The rorqual depletion trajectory was then used in an Ecosim scenario to drive rorqual biomasses and examine the "krill surplus" phenomenon and whaling effects on the food web in the years 1900-2008. An additional suite of Ecosim scenarios reflecting several hypothetical trends in Southern Ocean primary productivity were employed to examine the effect of bottom-up forcing on the documented krill biomass trend. The output of the Ecosim scenarios indicated that while the "krill surplus" hypothesis is a plausible explanation of the biomass trends observed in some penguin and pinniped species in the mid-20th century, the excess krill biomass was most likely eliminated by a rapid decline in primary productivity in the years 1975-1995. Our findings suggest that changes in physical conditions in the Southern Ocean during this time period could have eliminated the ecological effects of rorqual depletion, although the mechanism responsible is currently unknown. Furthermore, a decline in iron bioavailability due to rorqual depletion may have contributed to the rapid decline in overall Southern Ocean productivity during the last quarter of the 20th century. The results of this study underscore the need for further research on historical changes in the roles of top-down and bottom-up forcing in structuring the Southern Ocean food web.

  7. Southern Sudan: An opportunity for NTD control and elimination?

    Science.gov (United States)

    Rumunu, John; Brooker, Simon; Hopkins, Adrian; Emerson, Paul; Chane, Fasil; Kolaczinski, Jan

    2009-01-01

    Southern Sudan has been ravaged by decades of conflict and is thought to have one of the highest burdens of neglected tropical diseases (NTDs) in the world. Health care delivery, including efforts to control or eliminate NTDs, is severely hampered by a lack of infrastructure and health systems. However, the post-conflict environment and Southern Sudan's emerging health sector provide the unprecedented opportunity to build new, innovative programmes targeting NTDs. This article describes the current status of NTDs and their control in Southern Sudan and outlines the opportunities for the development of evidence-based, innovative implementation of NTD control. PMID:19540164

  8. The oceanic segment of the southern Brazilian margin: Morpho-structural domains and their tectonic significance

    Science.gov (United States)

    Bassetto, Marcelo; Alkmim, Fernando F.; Szatmari, Peter; Mohriak, Webster U.

    A descriptive and evolutionary analysis of the main morpho-structural features of the oceanic domain of the southern portion of the Brazilian Continental Margin is supported by regional seismic profiles and potential field data from the Brazilian governmental LEPLAC (Plano de Levantamento da Plataforma Continental Brasileira) Project. The several morpho-structural elements can be differentiated, as for example: the dominant structural pattern of the acoustic basement, including extensional faulting and long-wavelength folding, crustal thickness changes, fracture zones location, distribution of volcanic centers, and development of wedges of seaward-dipping reflectors. Four broad distinct morpho-structural domains, separated by fracture zones and oceanic lineaments. Domain I is located south of the Porto Alegre Lineament; Domain II corresponds to the area between the Porto Alegre Lineament and the Rio Grande Fracture Zone; Domain III spans the area of the São Paulo Plateau; and Domain IV is located to the east of this plateau, towards the abyssal portions of the oceanic crust. These domains are defined by their distinct regional morphologic and structural characteristics. Sometimes these elements are well imaged in the seismic profiles, corroborated by gravity and magnetic anomalies, and eventually identified as prominent features at the sea bottom physiography. Using a multidisciplinary approach based on bathymetric maps, regional seismic interpretation, magnetic data analysis, and gravity models, this work attempts to characterize these elements in a descriptive and evolutionary view, identifying their role in the tectonic development of this portion of the South Atlantic.

  9. Planktonic blooms from the Patagonian Shelf to the Open Waters of the Atlantic Sector of the Southern Ocean

    Science.gov (United States)

    Spitz, Y. H.; Combes, V.; Matano, R. P.

    2016-02-01

    The Patagonian shelf hosts some of the largest chlorophyll-a blooms of the Southern Ocean. Previous studies have shown that several physical processes, including shelfbreak upwelling and tidal mixing, as well as nutrient loads from continental and groundwater discharges and aeolian dust deposition can sustain these blooms. The vigorous exchanges of mass between the deep ocean and the Patagonian shelf are also thought to be an important source of micro-nutrients for the fertilization of the Southern Ocean, the main reason why the Atlantic basin dominates the primary productivity cycle of the subpolar region. We have developed a high-resolution, coupled ecosystem/iron/circulation model to quantitatively examine the physical and bio-chemical processes underlying Patagonia's chlorophyll-a blooms and the interaction between this shelf and the deep ocean.

  10. Southern Ocean air-sea heat flux, SST spatial anomalies, and implications for multi-decadal upper ocean heat content trends.

    Science.gov (United States)

    Tamsitt, V. M.; Talley, L. D.; Mazloff, M. R.

    2014-12-01

    The Southern Ocean displays a zonal dipole (wavenumber one) pattern in sea surface temperature (SST), with a cool zonal anomaly in the Atlantic and Indian sectors and a warm zonal anomaly in the Pacific sector, associated with the large northward excursion of the Malvinas and southeastward flow of the Antarctic Circumpolar Current (ACC). To the north of the cool Indian sector is the warm, narrow Agulhas Return Current (ARC). Air-sea heat flux is largely the inverse of this SST pattern, with ocean heat gain in the Atlantic/Indian, cooling in the southeastward-flowing ARC, and cooling in the Pacific, based on adjusted fluxes from the Southern Ocean State Estimate (SOSE), a ⅙° eddy permitting model constrained to all available in situ data. This heat flux pattern is dominated by turbulent heat loss from the ocean (latent and sensible), proportional to perturbations in the difference between SST and surface air temperature, which are maintained by ocean advection. Locally in the Indian sector, intense heat loss along the ARC is contrasted by ocean heat gain of 0.11 PW south of the ARC. The IPCC AR5 50 year depth-averaged 0-700 m temperature trend shows surprising similarities in its spatial pattern, with upper ocean warming in the ARC contrasted by cooling to the south. Using diagnosed heat budget terms from the most recent (June 2014) 6-year run of the SOSE we find that surface cooling in the ARC is balanced by heating from south-eastward advection by the current whereas heat gain in the ACC is balanced by cooling due to northward Ekman transport driven by strong westerly winds. These results suggest that spatial patterns in multi-decadal upper ocean temperature trends depend on regional variations in upper ocean dynamics.

  11. Roles of wind stress and thermodynamic forcing in recent trends in Antarctic sea ice and Southern Ocean SST: An ocean-sea ice model study

    Science.gov (United States)

    Kusahara, Kazuya; Williams, Guy D.; Massom, Robert; Reid, Phillip; Hasumi, Hiroyasu

    2017-11-01

    In contrast to a strong decrease in Arctic sea ice extent, overall Antarctic sea ice extent has modestly increased since 1979. Several hypotheses have been proposed for the net Antarctic sea ice expansion, including atmosphere/ocean circulation and temperature changes, sea ice-atmospheric-ocean feedback, increased precipitation, and enhanced basal meltwater from ice shelves. Concomitant with this positive trend in Antarctic sea ice, sea surface temperatures (SSTs) over the Southern Ocean south of approximately 45°S have cooled over this period. However, the mechanisms responsible for the Antarctic sea ice expansion and the SST cooling trend remain poorly defined. Here, we conduct comprehensive sensitivity experiments using a coupled ocean-sea ice model with a steady-state ice shelf component in order to investigate the main drivers of recent trends in Antarctic sea ice and SST over the Southern Ocean. The results suggest that Antarctic sea ice expansion is mostly explained by trends in the thermodynamic surface forcing, notably cooling and drying and a reduction in longwave radiation. Similarly, thermodynamic forcing is found to be the main driver of the zonal SST cooling trend. While apparently less influential on sea ice extent and SST, wind stress plays a key role in sea ice motion, thickening coastal sea ice, and thinning and decreasing the concentration of ice in mid-pack regions of the Amundsen-eastern Ross seas and 65-95°E in winter-spring. Furthermore, the model suggests that ocean-ice shelf interaction does not significantly influence the observed trends in Antarctic sea ice coverage and Southern Ocean SST in recent decades.

  12. Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

    Directory of Open Access Journals (Sweden)

    T. J. Ryan-Keogh

    2017-09-01

    Full Text Available The Atlantic sector of the Southern Ocean is characterized by markedly different frontal zones with specific seasonal and sub-seasonal dynamics. Demonstrated here is the effect of iron on the potential maximum productivity rates of the phytoplankton community. A series of iron addition productivity versus irradiance (PE experiments utilizing a unique experimental design that allowed for 24 h incubations were performed within the austral summer of 2015/16 to determine the photosynthetic parameters αB, PBmax and Ek. Mean values for each photosynthetic parameter under iron-replete conditions were 1.46 ± 0.55 (µg (µg Chl a−1 h−1 (µM photons m−2 s−1−1 for αB, 72.55 ± 27.97 (µg (µg Chl a−1 h−1 for PBmax and 50.84 ± 11.89 (µM photons m−2 s−1 for Ek, whereas mean values under the control conditions were 1.25 ± 0.92 (µg (µg Chl a−1 h−1 (µM photons m−2 s−1−1 for αB, 62.44 ± 36.96 (µg (µg Chl a−1 h−1 for PBmax and 55.81 ± 19.60 (µM photons m−2 s−1 for Ek. There were no clear spatial patterns in either the absolute values or the absolute differences between the treatments at the experimental locations. When these parameters are integrated into a standard depth-integrated primary production model across a latitudinal transect, the effect of iron addition shows higher levels of primary production south of 50° S, with very little difference observed in the subantarctic and polar frontal zone. These results emphasize the need for better parameterization of photosynthetic parameters in biogeochemical models around sensitivities in their response to iron supply. Future biogeochemical models will need to consider the combined and individual effects of iron and light to better resolve the natural background in primary production and predict its response under a changing climate.

  13. Dense shelf water spreading from Antarctic coastal polynyas to the deep Southern Ocean: A regional circumpolar model study

    Science.gov (United States)

    Kusahara, Kazuya; Williams, Guy D.; Tamura, Takeshi; Massom, Robert; Hasumi, Hiroyasu

    2017-08-01

    The spreading of dense shelf water (DSW) from Antarctic coastal margins to lower latitudes plays a vital role in the ocean thermohaline circulation and the global climate system. Through enhanced localized sea ice production in Antarctic coastal polynyas, cold and saline DSW is formed over the continental shelf regions as a precursor to Antarctic Bottom Water (AABW). However, the detailed fate of coastal DSW over the Southern Ocean is still unclear. Here we conduct extensive passive tracer experiments using a circumpolar ocean-sea ice-ice shelf model to investigate pathways of the regional polynya-based DSW from the Antarctic margins to the deep Southern Ocean basins. In the numerical experiments, the Antarctic coastal margin is divided into nine regions, and a passive tracer is released from each region at the same rate as the local sea ice production. The modeled spatial distribution of the total concentration of the nine tracers is consistent with the observed AABW distribution and clearly demonstrates nine routes of the DSW over the Southern Ocean along its bottom topography. Furthermore, the model shows that while ˜50% of the total tracer is distributed northward from the continental shelf to the deep ocean, ˜7% is transported poleward beneath ice shelf cavities. The comprehensive tracer experiments allow us to estimate the contribution of local DSW to the total concentration along each of the pathways.

  14. An inter-comparison of six latent and sensible heat flux products over the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Lejiang Yu

    2011-11-01

    Full Text Available The latent heat fluxes (LHF and sensible heat fluxes (SHF over the Southern Ocean from six different data sets are inter-compared for the period 1988–2000. The six data sets include three satellite-based products, namely, the second version of the Goddard Satellite-Based Surface Turbulent Fluxes data set (GSSTF-2, the third version of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS-3 and the Japanese Ocean Fluxes Data Sets with Use of Remote Sensing Observations (J-OFURO; two global reanalysis products, namely, the National Centers for Environmental Prediction–Department of Energy Reanalysis 2 data set (NCEP-2 and the European Centre for Medium-Range Weather Forecasts 40 Year Re-analysis data set (ERA-40; and the Objectively Analyzed Air–Sea Fluxes for the Global Oceans data set (OAFlux. All these products reveal a similar pattern in the averaged flux fields. The zonal mean LHF fields all exhibit a continuous increase equatorward. With an exception of HOAPS-3, the zonal mean SHF fields display a minimum value near 50°S, increasing both pole- and equatorward. The differences in the standard deviation for LHF are larger among the six data products than the differences for SHF. Over the regions where the surface fluxes are significantly influenced by the Antarctic Oscillation and the Pacific–South American teleconnection, the values and distributions of both LHF and SHF are consistent among the six products. It was found that the spatial patterns of the standard deviations and trends of LHF and SHF can be explained primarily by sea–air specific humidity and temperature differences; wind speed plays a minor role.

  15. Effect of natural iron fertilization on carbon sequestration in the Southern Ocean.

    Science.gov (United States)

    Blain, Stéphane; Quéguiner, Bernard; Armand, Leanne; Belviso, Sauveur; Bombled, Bruno; Bopp, Laurent; Bowie, Andrew; Brunet, Christian; Brussaard, Corina; Carlotti, François; Christaki, Urania; Corbière, Antoine; Durand, Isabelle; Ebersbach, Frederike; Fuda, Jean-Luc; Garcia, Nicole; Gerringa, Loes; Griffiths, Brian; Guigue, Catherine; Guillerm, Christophe; Jacquet, Stéphanie; Jeandel, Catherine; Laan, Patrick; Lefèvre, Dominique; Lo Monaco, Claire; Malits, Andrea; Mosseri, Julie; Obernosterer, Ingrid; Park, Young-Hyang; Picheral, Marc; Pondaven, Philippe; Remenyi, Thomas; Sandroni, Valérie; Sarthou, Géraldine; Savoye, Nicolas; Scouarnec, Lionel; Souhaut, Marc; Thuiller, Doris; Timmermans, Klaas; Trull, Thomas; Uitz, Julia; van Beek, Pieter; Veldhuis, Marcel; Vincent, Dorothée; Viollier, Eric; Vong, Lilita; Wagener, Thibaut

    2007-04-26

    The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization--an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below--as invoked in some palaeoclimatic and future climate change scenarios--may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.

  16. Effect of natural iron fertilization on carbon sequestration in the Southern Ocean

    Science.gov (United States)

    Blain, Stéphane; Quéguiner, Bernard; Armand, Leanne; Belviso, Sauveur; Bombled, Bruno; Bopp, Laurent; Bowie, Andrew; Brunet, Christian; Brussaard, Corina; Carlotti, François; Christaki, Urania; Corbière, Antoine; Durand, Isabelle; Ebersbach, Frederike; Fuda, Jean-Luc; Garcia, Nicole; Gerringa, Loes; Griffiths, Brian; Guigue, Catherine; Guillerm, Christophe; Jacquet, Stéphanie; Jeandel, Catherine; Laan, Patrick; Lefèvre, Dominique; Lo Monaco, Claire; Malits, Andrea; Mosseri, Julie; Obernosterer, Ingrid; Park, Young-Hyang; Picheral, Marc; Pondaven, Philippe; Remenyi, Thomas; Sandroni, Valérie; Sarthou, Géraldine; Savoye, Nicolas; Scouarnec, Lionel; Souhaut, Marc; Thuiller, Doris; Timmermans, Klaas; Trull, Thomas; Uitz, Julia; van Beek, Pieter; Veldhuis, Marcel; Vincent, Dorothée; Viollier, Eric; Vong, Lilita; Wagener, Thibaut

    2007-04-01

    The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization-an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below-as invoked in some palaeoclimatic and future climate change scenarios-may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.

  17. Characterising cloud regimes associated with the Southern Ocean shortwave radiation bias

    Science.gov (United States)

    Mason, S.; Jakob, C.; Protat, A.

    2013-12-01

    The high-latitude Southern Ocean is the site of persistent cloud biases in GCMs. A deficit of shortwave cloud radiative effect especially between 50-65S causes an excess of absorbed shortwave radiation, which has been associated with other biases in the global circulation. Recent model evaluation studies have found that the shortwave radiation bias is potentially associated with low- and mid-level clouds in the cold-air part of extratropical cyclones and ahead of transient ridges. However a coherent description of the cloud properties and cloud processes most associated with the bias has not yet emerged. This study focuses on three cloud regimes that are most frequent in the area of the shortwave radiation bias during the austral summer. They are selected from the cloud regimes derived for the Southern Ocean from International Satellite Cloud Climatology Project (ISCCP) cloud observations. We characterise the selected cloud regimes in terms of their meteorological conditions using the ECMWF Interim reanalysis. We also study their vertical macrophysical structure and microphysical properties based on active satellite observations using the DARDAR (raDAR/liDAR) combined CloudSat and CALIPSO data product. We find that two cloud regimes identified as mid-topped in the ISCCP based data set are associated with distinct meteorological processes. An optically thin mid-level top cloud regime is related to cold mid-levels, cold-air advection and moderate subsidence, while an optically thicker cloud regime is associated with a broader range of conditions resembling weak to moderate frontal events, with warm and moist mid-levels, moderate ascent and warm-air advection. The vertical cloud structure derived from DARDAR profiles show that both these regimes contain mostly low clouds, but both also include frequent occurrences of mid-level cloud. We use a clustering method to quantify the differences in microphysical properties between the regimes. We find that the optically

  18. Isotopic investigation of contemporary and historic changes in penguin trophic niches and carrying capacity of the southern Indian ocean.

    Directory of Open Access Journals (Sweden)

    Audrey Jaeger

    Full Text Available A temperature-defined regime shift occurred in the 1970s in the southern Indian Ocean, with simultaneous severe decreases in many predator populations. We tested a possible biological link between the regime shift and predator declines by measuring historic and contemporary feather isotopic signatures of seven penguin species with contrasted foraging strategies and inhabiting a large latitudinal range. We first showed that contemporary penguin isotopic variations and chlorophyll a concentration were positively correlated, suggesting the usefulness of predator δ¹³C values to track temporal changes in the ecosystem carrying capacity and its associated coupling to consumers. Having controlled for the Suess effect and for increase CO₂ in seawater, δ¹³C values of Antarctic penguins and of king penguins did not change over time, while δ¹³C of other subantarctic and subtropical species were lower in the 1970s. The data therefore suggest a decrease in ecosystem carrying capacity of the southern Indian Ocean during the temperature regime-shift in subtropical and subantarctic waters but not in the vicinity of the Polar Front and in southward high-Antarctic waters. The resulting lower secondary productivity could be the main driving force explaining the decline of subtropical and subantarctic (but not Antarctic penguins that occurred in the 1970s. Feather δ¹⁵N values did not show a consistent temporal trend among species, suggesting no major change in penguins' diet. This study highlights the usefulness of developing long-term tissue sampling and data bases on isotopic signature of key marine organisms to track potential changes in their isotopic niches and in the carrying capacity of the environment.

  19. Friend or Foe: Variability in How Sea Ice Can Both Hinder and Enhance Phytoplankton Blooms Across the Southern Ocean

    Science.gov (United States)

    Rohr, T.

    2016-02-01

    Globally, a suite of physical and biogeochemical controls govern the structure, size, and timing of seasonal phytoplankton blooms. In the Southern Ocean, the introduction of seasonal sea ice provides an additional constraining factor. From a bottom-up perspective, a reduction in sea ice can both enhance bloom development by permitting greater levels of surface PAR uninhibited by ice and suppress a bloom when reduced fresh melt-water inputs and increased vulnerability to wind stress combine to create deeper mixed layers and decrease depth integrated light availability. Regions along the Western Antarctic Peninsula have already seen a contradictory response to reduced ice cover, with enhanced summertime chlorophyll concentrations in the South, and large declines to the North. This dichotomy is thought to arise from differences in the interannual mean sea ice state, with extensively ice covered regions benefiting from reduced coverage and more sparsely covered regions hindered by further reductions. The questions arises: 1) At what threshold does a reduction in sea ice transition from amplifying blooms to suppressing them? 2) How do additional environmental considerations such as nutrient availability and trophic interactions complicate this transition? Here, we combine remote sensing observations and in-situ data (from PAL LTER) with a hierarchy of 1-D water column and global general circulation (CESM) models to access the variability in how regional differences in mean ice state combine with other environmental forcings to dictate how interannual variability (or long term trends) in ice coverage will affect bloom structure, size and dynamics. In doing so we will gain a better understanding of how predicted changes in sea ice will effect Southern Ocean productivity, which of course will have important consequences in the global carbon cycle and sustainability of healthy marine ecosystems.

  20. Variability of SeaWiFs chlorophyll- a in the southwest Atlantic sector of the Southern Ocean: Strong topographic effects and weak seasonality

    Science.gov (United States)

    Park, Jisoo; Oh, Im-Sang; Kim, Hyun-Cheol; Yoo, Sinjae

    2010-04-01

    This study examined 11-year (1997-2008) weekly and monthly time series of satellite-observed ocean color to understand the dominant temporal and spatial patterns of chlorophyll- a in the southwest Atlantic sector of the Southern Ocean. Using empirical orthogonal function analysis and k-means classification, we classified the study area into eight regions, which were in good accordance with the oceanographic and topographic features. Examination of the chlorophyll- a time series in each region revealed that contrary to our expectation, regular seasonal phytoplankton blooms were observed only in a limited area. Of the eight regions, only two showed typical seasonal blooms, and one showed weak seasonality, whereas other regions exhibited irregular seasonal blooms of variable duration. We attribute the absence of regularity in seasonal blooms to relatively shallow winter mixing, which would prevent entrainment of limiting micronutrients such as iron and silicate. In the southwest Atlantic sector of the Southern Ocean, topographic effects and sea ice may be the most important factors controlling primary productivity. In the South Georgia region, chlorophyll- a showed a significant correlation with geostrophic current velocity, indicating that topographic effects depend on the interaction of current strength and topographic structure. Interannual variability of the surface chlorophyll in some regions also revealed longer periodicity (˜6 years). The periodicity seemed to be related to El Niño-Southern Oscillation and to sea-ice dynamics influenced by the Antarctic Circumpolar Current.

  1. Morphological and physiological effects in proboscia alata (bacillariophyceae) grown under different light and CO2 conditions of the modern Southern ocean

    NARCIS (Netherlands)

    Hoogstraten, Astrid; Timmermans, Klaas R.; de Baar, Hein J. W.

    The combined effects of different light and aqueous CO2 conditions were assessed for the Southern Ocean diatom Proboscia alata (Brightwell) Sundstrom in laboratory experiments. Selected culture conditions (light and CO2(aq)) were representative for the natural ranges in the modern Southern Ocean.

  2. Modulation of the Southern Africa precipitation response to the El Niño Southern Oscillation by the subtropical Indian Ocean Dipole

    Science.gov (United States)

    Hoell, Andrew; Funk, Chris; Zinke, Jens; Harrison, Laura

    2017-04-01

    The climate of Southern Africa, defined as the land area bound by the region 15°S-35°S; 12.5°E-42.5°E, during the December-March rainy season is driven by Indo-Pacific sea surface temperature (SST) anomalies associated with the El Niño Southern Oscillation (ENSO) and the Subtropical Indian Ocean Dipole (SIOD). The observed December-March 1979-2014 Southern Africa precipitation during the four ENSO and SIOD phase combinations suggests that the phase of the SIOD can disrupt or enhance the Southern Africa precipitation response to ENSO. Here, we use a large ensemble of model simulations driven by global SST and ENSO-only SST to test whether the SIOD modifies the relationship between Southern Africa precipitation and ENSO. Since ENSO-based precipitation forecasts are used extensively over Southern Africa, an improved understanding of how other modes of SST variability modulate the regional response to ENSO is important. ENSO, in the absence of the SIOD, forces an equivalent barotropic Rossby wave over Southern Africa that modifies the regional mid-tropospheric vertical motions and precipitation anomalies. El Niño (La Niña) is related with high (low) pressure over Southern Africa that produces anomalous mid-tropospheric descent (ascent) and decreases (increases) in precipitation relative to average. When the SIOD and ENSO are in opposite phases, the SIOD compliments the ENSO-related atmospheric response over Southern Africa by strengthening the regional equivalent barotropic Rossby wave, anomalous mid-tropospheric vertical motions and anomalous precipitation. By contrast, when the SIOD and ENSO are in the same phase, the SIOD disrupts the ENSO-related atmospheric response over Southern Africa by weakening the regional equivalent barotropic Rossby wave, anomalous mid-tropospheric vertical motions and anomalous precipitation.

  3. Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    DEFF Research Database (Denmark)

    Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín

    2016-01-01

    zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.......Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global...... biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs): six types of phytoplankton, three types of zooplankton, and heterotrophic procaryotes. We improved the representation of zooplankton dynamics in our model through (a) the explicit...

  4. Cloud condensation nuclei over the Southern Ocean: wind dependence and seasonal cycles

    Science.gov (United States)

    Gras, John L.; Keywood, Melita

    2017-04-01

    Multi-decadal observations of aerosol microphysical properties from regionally representative sites can be used to challenge regional or global numerical models that simulate atmospheric aerosol. Presented here is an analysis of multi-decadal observations at Cape Grim (Australia) that characterise production and removal of the background marine aerosol in the Southern Ocean marine boundary layer (MBL) on both short-term weather-related and underlying seasonal scales.A trimodal aerosol distribution comprises Aitken nuclei ( 350 nm) modes, with the Aitken mode dominating number concentration. Whilst the integrated particle number in the MBL over the clean Southern Ocean is only weakly dependent on wind speed, the different modes in the aerosol size distribution vary in their relationship with wind speed. The balance between a positive wind dependence in the coarse mode and negative dependence in the accumulation/CCN mode leads to a relatively flat wind dependence in summer and moderately strong positive wind dependence in winter. The changeover in wind dependence of these two modes occurs in a very small size range at the mode intersection, indicative of differences in the balance of production and removal in the coarse and accumulation/CCN modes.Whilst a marine biological source of reduced sulfur appears to dominate CCN concentration over the summer months (December to February), other components contribute to CCN over the full annual cycle. Wind-generated coarse-mode sea salt is an important CCN component year round and is the second-most-important contributor to CCN from autumn through to mid-spring (March to November). A portion of the non-seasonally dependent contributor to CCN can clearly be attributed to wind-generated sea salt, with the remaining part potentially being attributed to long-range-transported material. Under conditions of greater supersaturation, as expected in more convective cyclonic systems and their associated fronts, Aitken mode particles

  5. Marked phylogeographic structure of Gentoo penguin reveals an ongoing diversification process along the Southern Ocean.

    Science.gov (United States)

    Vianna, Juliana A; Noll, Daly; Dantas, Gisele P M; Petry, Maria Virginia; Barbosa, Andrés; González-Acuña, Daniel; Le Bohec, Céline; Bonadonna, Francesco; Poulin, Elie

    2017-02-01

    Two main hypotheses have been debated about the biogeography of the Southern Ocean: (1) the Antarctic Polar Front (APF), acting as a barrier between Antarctic and sub-Antarctic provinces, and (2) the Antarctic Circumpolar Current (ACC), promoting gene flow among sub-Antarctic areas. The Gentoo penguin is distributed throughout these two provinces, separated by the APF. We analyzed mtDNA (HVR1) and 12 microsatellite loci of 264 Gentoo penguins, Pygoscelis papua, from 12 colonies spanning from the Western Antarctic Peninsula and the South Shetland Islands (WAP) to the sub-Antarctic Islands (SAI). While low genetic structure was detected among WAP colonies (mtDNA Ф ST =0.037-0.133; microsatellite F ST =0.009-0.063), high differentiation was found between all SAI and WAP populations (mtDNA Ф ST =0.678-0.930; microsatellite F ST =0.110-0.290). These results suggest that contemporary dispersal around the Southern Ocean is very limited or absent. As predicted, the APF appears to be a significant biogeographical boundary for Gentoo penguin populations; however, the ACC does not promote connectivity in this species. Our data suggest demographic expansion in the WAP during the last glacial maximum (LGM, about 20kya), but stability in SAI. Phylogenetic analyses showed a deep divergence between populations from the WAP and those from the SAI. Therefore, taxonomy should be further revised. The Crozet Islands resulted as a basal clade (3.57Mya), followed by the Kerguelen Islands (2.32Mya) as well as a more recent divergence between the Falkland/Malvinas Islands and the WAP (1.27Mya). Historical isolation, local adaptation, and past climate scenarios of those Evolutionarily Significant Units may have led to different potentials to respond to climate changes. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Iron Speciation in Proximity to an Active Volcanic Hotspot, Kerguelen Plateau, Southern Ocean

    Science.gov (United States)

    Holmes, T.; Wuttig, K.; Chase, Z.; van der Merwe, P.; Townsend, A.; Bowie, A. R.

    2016-12-01

    Low iron (Fe) concentrations limit biological productivity in over a third of the world's oceans. The Southern Ocean (SO) is the largest of these regions of Fe deficiency. However, within the Indian sector of the SO lays an oasis of relatively Fe rich waters overlaying the Kerguelen Plateau. At the southern part of the central Kerguelen plateau is an active volcanic hotspot, hosting two volcanically active islands, Heard and MacDonald (HIMI), the former of which is largely covered by glaciers. Waters in the region are subject to an intense mixing regime, caused by shallow bathymetry and the location of the plateau in the path of strong currents associated with the polar front. Fed by the Fe rich waters formed on the plateau, a plankton bloom on the order of thousands of square kilometres forms in the lee of the plateau annually each summer. Here we present dissolved iron (dFe), dissolved iron(II) (dFe(II)) and hydrogen peroxide (H2O2) data from waters surrounding HIMI on the central Kerguelen Plateau collected on RV Investigator voyage IN2016_V01 in early 2016. Analysis was performed at sea using three separate flow injection - chemiluminescence instruments. Two broadly zonal transects revealed that dFe was present in limiting concentrations (island and accounted for up to 30% of the total dFe. We also observed an intense mixing regime homogenising short-lived Fe(II) and H2O2 species throughout the water column in shallow areas of the plateau. Our results revealed varying Fe speciation patterns between the islands indicating multiple Fe sources around HIMI, including reducing hydrothermal, sedimentary and glacial sources.

  7. Major Characteristics of Southern Ocean Cloud Regimes and Their Effects on the Energy Budget

    Science.gov (United States)

    Haynes, John M.; Jakob, Christian; Rossow, William B.; Tselioudis, George; Brown, Josephine

    2011-01-01

    Clouds over the Southern Ocean are often poorly represented by climate models, but they make a significant contribution to the top-of-atmosphere (TOA) radiation balance, particularly in the shortwave portion of the energy spectrum. This study seeks to better quantify the organization and structure of Southern Hemisphere midlatitude clouds by combining measurements from active and passive satellite-based datasets. Geostationary and polar-orbiter satellite data from the International Satellite Cloud Climatology Project (ISCCP) are used to quantify large-scale, recurring modes of cloudiness, and active observations from CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) are used to examine vertical structure, radiative heating rates, and precipitation associated with these clouds. It is found that cloud systems are organized into eight distinct regimes and that ISCCP overestimates the midlevel cloudiness of these regimes. All regimes contain a relatively high occurrence of low cloud, with 79%of all cloud layers observed having tops below 3 km, but multiple-layered clouds systems are present in approximately 34% of observed cloud profiles. The spatial distribution of regimes varies according to season, with cloud systems being geometrically thicker, on average, during the austral winter. Those regimes found to be most closely associated with midlatitude cyclones produce precipitation the most frequently, although drizzle is extremely common in low-cloud regimes. The regimes associated with cyclones have the highest in-regime shortwave cloud radiative effect at the TOA, but the low-cloud regimes, by virtue of their high frequency of occurrence over the oceans, dominate both TOA and surface shortwave effects in this region as a whole.

  8. Changes in the concentration of iron in different size fractions during an iron enrichment experiment in the open Southern Ocean

    NARCIS (Netherlands)

    Nishioka, Jun; Takeda, Shigenobu; Baar, Hein J.W. de; Croot, Peter L.; Boye, Marie; Laan, Patrick; Timmermans, Klaas R.

    2005-01-01

    An in situ iron enrichment experiment was carried out in the Southern Ocean Polar Frontal Zone and fertilized a patch of water within an eddy of the Antarctic Circumpolar Current (EisenEx, Nov. 2000). During the experiment, a physical speciation technique was used for iron analysis in order to

  9. Observation of consistent trends in the organic complexation of dissolved iron in the Atlantic sector of the Southern Ocean

    NARCIS (Netherlands)

    Thuróczy, C.E.; Gerringa, L.J.A.; Klunder, M.B.; Laan, P.; de Baar, H.J.W.

    2011-01-01

    Organic complexation of dissolved iron (dFe) was investigated in the Atlantic sector of the Southern Ocean in order to understand the distribution of Fe over the whole water column. The total concentration of dissolved organic ligands ([Lt]) measured by voltammetry ranged between 0.54 and 1.84 nEq

  10. Key role of organic complexation of iron in sustaining phytoplankton blooms in the Pine Island and Amundsen Polynyas (Southern Ocean)

    NARCIS (Netherlands)

    Thuroczy, Charles-Edouard; Alderkamp, Anne-Carlijn; Laan, Patrick; Gerringa, Loes J. A.; Mills, Matthew M.; Van Dijken, Gert L.; De Baar, Hein J. W.; Arrigo, Kevin R.

    2012-01-01

    Primary productivity in the Amundsen Sea (Southern Ocean) is among the highest in Antarctica. The summer phytoplankton bloom in 2009 lasted for > 70 days in both the Pine Island and Amundsen Polynyas. Such productive blooms require a large supply of nutrients, including the trace metal iron (Fe).

  11. Natural iron fertilization of the Atlantic sector of the Southern Ocean by continental shelf sources of the Antarctic Peninsula

    NARCIS (Netherlands)

    de Jong, J.; Schoemann, V.; Lannuzel, D.; Croot, P.; de Baar, H.; Tison, J.-L.

    2012-01-01

    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

  12. Algal pigment patterns in different watermasses of the Atlantic sector of the Southern Ocean during fall 1987

    NARCIS (Netherlands)

    Buma, Anita; Treguer, Paul J; Kraaij, Gijs W; Morvan, Jean

    1990-01-01

    During the autumn of 1987 a survey was carried out in the Atlantic sector of the Southern Ocean in order to study phytoplankton community structure in relation to hydrological features. The positions of the boundary zones, determined by means of hydrological and chemical properties (especially

  13. Major deviations of iron complexation during 22 days of a mesoscale iron enrichment in the open Southern Ocean

    NARCIS (Netherlands)

    Boye, Marie; Nishioka, Jun; Croot, Peter L.; Laan, Patrick; Timmermans, Klaas R.; Baar, Hein J.W. de

    2005-01-01

    The speciation of strongly chelated iron during the 22-day course of an iron enrichment experiment in the Atlantic sector of the Southern Ocean deviates strongly from ambient natural waters. Three iron additions (ferrous sulfate solution) were conducted, resulting in elevated dissolved iron

  14. Long-Term Relationships between the Marine Environment, Krill and Salps in the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Chung Il Lee

    2010-01-01

    Full Text Available Long-term variations (1975–2002 in climatology of marine environmental parameters, Antarctic krill, Euphausia superba, and the pelagic tunicate, Salpa thompsoni, were compared within the Atlantic Sector of the Southern Ocean. Sea water temperature in the top 400 m increased at a rate of 0.020–0.030°C ⋅ yr−1, which was accompanied by the dissolved oxygen decline. Top 100 m water layer became fresher with lower concentrations of phosphates and nitrates, while at subsurface layers (200–400 m both salinity and nutrients showed small increasing trend. Unlike phosphates and nitrates, silicate concentrations decreased in the entire water column. Shorter-term water temperature dynamics closely correlated with the El Nino events expressed as the Southern Oscillation Index which in turn was linked to the propagation of the Antarctic Circumpolar Wave (ACW. The variations of sea-ice extent matched well the changes in both air and water temperatures. In general, abundance of krill and salps showed opposite to each other trends. Due to large area considered in this study, no significant relationships between abiotic factors and both krill and salps were found. However, our analysis demonstrated that krill abundance was greater in years with lower sea water temperature, greater sea-ice extent and higher nutrient concentration, while salps showed the opposite pattern.

  15. Distribution, reproductive and energetic conditions of decapod crustaceans along the Scotia Arc (Southern Ocean

    Directory of Open Access Journals (Sweden)

    Gustavo A. Lovrich

    2005-12-01

    Full Text Available Studies on decapod distribution patterns and reproductive and energetic conditions were carried out along the islands and shallows of the Scotia Arc (Southern Ocean during the RV “Polarstern” LAMPOS expedition (ANT XIX/5 between April and May 2002. A clear biogeographic zonation was found. The Subantarctic Magellan-South Atlantic decapod fauna consisting of both “natant” (caridean and “reptant” (astacidean, anomuran, and brachyuran decapods appeared along the northern branch of the Scotia Arc to South Georgia, where Subantarctic and Antarctic faunas were found overlapping. An impoverished caridean shrimp fauna was found along the islands of the southern branch, from the South Sandwich Islands to the Antarctic Peninsula. Differences in the reproductive traits of the two most abundant species were detected. The reproductive cycle of Notocrangon antarcticus at South Georgia was more advanced than that at the South Orkney Islands, probably due to temperature differences between the two locations. Although the oogenesis and the reproductive cycle of Munida subrugosa seem to be in phase at Burdwood Bank and in the Beagle Channel, the oocyte number is probably lower at the former location. A new index was used to measure the energy devoted to reproduction by relating the energy contents of the egg mass/ovary plus hepatopancreas and the energy content of the whole body. This index revealed that the energy investment in reproduction was (1 independent of the sampling location, (2 species-specific, and (3 larger in caridean shrimps than in galatheid crabs.

  16. Persistent organic pollutants (POPs) in killer whales (Orcinus orca) from the Crozet Archipelago, southern Indian Ocean.

    Science.gov (United States)

    Noël, Marie; Barrett-Lennard, Lance; Guinet, Christophe; Dangerfield, Neil; Ross, Peter S

    2009-10-01

    Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs), are ubiquitous environmental contaminants of which significant concentrations are reported in upper trophic level animals. In 1998, we collected blubber biopsy samples (n=11) from killer whales (Orcinus orca) inhabiting the coastal waters around Possession Island, Crozet Archipelago, southern Indian Ocean, for contaminant analyses. Despite inhabiting an isolated region far removed from industrial activities, these killer whales can presently be considered among the most PCB-contaminated cetaceans in the southern hemisphere, with concentrations ranging from 4.4 to 20.5mg/kg lipid weight (lw). PCDD levels ranged from below the detection limit (5 ng/kg) to 77.1 ng/kg lw and PCDF levels from below the detection limit (7 ng/kg) to 36.1 ng/kg lw. Over 70% of our study animals had PCB concentrations which exceeded a 1.3mg/kg PCB threshold established for endocrine disruption and immunotoxicity in free-ranging harbour seals, suggesting that organic contaminants cannot be ruled out as an additional threat to this declining population.

  17. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2014-12-30 to 2015-07-01 (NCEI Accession 0144343)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144343 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  18. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-01-02 to 2011-12-18 (NCEI Accession 0148767)

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    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148767 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  19. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2002-12-29 to 2003-11-30 (NCEI Accession 0144351)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144351 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  20. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2007-01-02 to 2007-12-20 (NCEI Accession 0148773)

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    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148773 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  1. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2007-12-30 to 2008-10-28 (NCEI Accession 0144348)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144348 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  2. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-12-30 to 2012-12-24 (NCEI Accession 0144349)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144349 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  3. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2014-01-01 to 2014-12-20 (NCEI Accession 0145200)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0145200 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  4. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2007-01-02 to 2007-12-22 (NCEI Accession 0144528)

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    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144528 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  5. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-01-02 to 2011-12-19 (NCEI Accession 0144354)

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    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144354 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  6. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2002-03-23 to 2002-12-23 (NCEI Accession 0148766)

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    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148766 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  7. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2006-01-01 to 2006-12-27 (NCEI Accession 0144535)

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    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144535 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  8. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2013-12-31 to 2014-12-20 (NCEI Accession 0144532)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144532 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  9. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2002-03-07 to 2002-12-23 (NCEI Accession 0144356)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144356 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  10. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2011-12-30 to 2012-12-23 (NCEI Accession 0148774)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148774 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  11. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2006-01-02 to 2006-12-26 (NCEI Accession 0148764)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148764 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  12. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2010-01-01 to 2011-12-19 (NCEI Accession 0148765)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148765 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  13. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2003-01-01 to 2003-12-29 (NCEI Accession 0148770)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148770 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  14. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans from 2007-12-31 to 2008-10-27 (NCEI Accession 0148763)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0148763 includes Surface underway data collected from LAURENCE M. GOULD in the South Atlantic Ocean, South Pacific Ocean and Southern Oceans (> 60...

  15. Water mass mixing shapes bacterial biogeography in a highly hydrodynamic region of the Southern Ocean.

    Science.gov (United States)

    Hernando-Morales, Víctor; Ameneiro, Julia; Teira, Eva

    2017-03-01

    Even though compelling evidences indicate that marine microbes show biogeographic patterns, very little is known on the mechanisms driving those patterns in aquatic ecosystems. In the present study, bacterial community structure was examined in epipelagic waters of a highly hydrodynamic area of the Southern Ocean to gain insight into the role that biogeochemical factors and water mass mixing (a proxy of dispersal) have on microbial biogeography. Four water masses that converge and mix around the South Shetland Islands (northern tip of the Antarctic Peninsula) were investigated. Bacterioplankton communities were water-mass specific, and were best explained by dispersal rather than by biogeochemical factors, which is attributed to the relatively reduced environmental gradients found in these cold and nutrient rich waters. These results support the notion that currents and water mixing may have a considerable effect in connecting and transforming different water bodies, and consequently, in shaping communities of microorganisms. Considering the multidimensional and dynamic nature of the ocean, analysis of water mass mixing is a more suitable approach to investigate the role of dispersal on the biogeography of planktonic microorganisms rather than geographical distance. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  16. Southern Indian Ocean SST as a modulator for the progression of Indian summer monsoon

    Science.gov (United States)

    Shahi, Namendra Kumar; Rai, Shailendra; Mishra, Nishant

    2018-01-01

    This study explores the possibility of southern Indian Ocean (SIO) sea surface temperature (SST) as a modulator for the early phase of Indian summer monsoon and its possible physical mechanism. A dipole-like structure is obtained from the empirical orthogonal function (EOF) analysis which is similar to an Indian Ocean subtropical dipole (IOSD) found earlier. A subtropical dipole index (SDI) is defined based on the SST anomaly over the positive and negative poles. The regression map of rainfall over India in the month of June corresponding to the SDI during 1983-2013 shows negative patterns along the Western Ghats and Central India. However, the regression pattern is insignificant during 1952-1982. The multiple linear regression models and partial correlation analysis also indicate that the SDI acts as a dominant factor to influence the rainfall over India in the month of June during 1983-2013. The similar result is also obtained with the help of composite rainfall over the land points of India in the month of June for positive (negative) SDI events. It is also observed that the positive (negative) SDI delays (early) the onset dates of Indian monsoon over Kerala during the time domain of our study. The study is further extended to identify the physical mechanism of this impact, and it is found that the heating (cooling) in the region covering SDI changes the circulation pattern in the SIO and hence impacts the progression of monsoon in India.

  17. Isotopic disequilibrium in Globigerina bulloides and carbon isotope response to productivity increase in Southern Ocean

    Science.gov (United States)

    Prasanna, K.; Ghosh, Prosenjit; Bhattacharya, S. K.; Mohan, K.; Anilkumar, N.

    2016-01-01

    Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45°E and 80°E and 10°N to 53°S) were analysed and compared with the equilibrium δ18O and δ13C values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within ~0.25‰ for the region between 10°N and 40°S and 75–200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40°S to 55°S), however, the measured δ18O and δ13C values are higher than the expected values by ~2‰ and ~1‰ respectively. These enrichments can be attributed to either a ‘vital effect’ or a higher calcification rate. An interesting pattern of increase in the δ13C(DIC) value of the surface water with latitude is observed between 35°S and~ 60°S, with a peak at~ 42°S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the δ13C(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude. PMID:26903274

  18. Factors regulating the Great Calcite Belt in the Southern Ocean and its biogeochemical significance

    Science.gov (United States)

    Balch, William M.; Bates, Nicholas R.; Lam, Phoebe J.; Twining, Benjamin S.; Rosengard, Sarah Z.; Bowler, Bruce C.; Drapeau, Dave T.; Garley, Rebecca; Lubelczyk, Laura C.; Mitchell, Catherine; Rauschenberg, Sara

    2016-08-01

    The Great Calcite Belt (GCB) is a region of elevated surface reflectance in the Southern Ocean (SO) covering 16% of the global ocean and is thought to result from elevated, seasonal concentrations of coccolithophores. Here we describe field observations and experiments from two cruises that crossed the GCB in the Atlantic and Indian sectors of the SO. We confirm the presence of coccolithophores, their coccoliths, and associated optical scattering, located primarily in the region of the subtropical, Agulhas, and Subantarctic frontal regions. Coccolithophore-rich regions were typically associated with high-velocity frontal regions with higher seawater partial pressures of CO2 (pCO2) than the atmosphere, sufficient to reverse the direction of gas exchange to a CO2 source. There was no calcium carbonate (CaCO3) enhancement of particulate organic carbon (POC) export, but there were increased POC transfer efficiencies in high-flux particulate inorganic carbon regions. Contemporaneous observations are synthesized with results of trace-metal incubation experiments, 234Th-based flux estimates, and remotely sensed observations to generate a mandala that summarizes our understanding about the factors that regulate the location of the GCB.

  19. Mechanisms of the Indian Ocean Dipole influence on El Niño/Southern Oscillation

    Science.gov (United States)

    Izumo, Takeshi; Vialard, Jérome; Lengaigne, Matthieu; Jourdain, Nicolas; Dayan, Hugo; Suresh, Iyyappan

    2017-04-01

    Despite the tremendous socio-economic and environmental impacts of the El Niño-Southern Oscillation (ENSO), its forecasts at lead times longer than a few months remain challenging, as recently evidenced by the unexpected 2014-2015 El Niño sequence. Recent studies have suggested that negative (postive) Indian Ocean Dipole events may favour the development of El Niño (La Niña) events peaking one year later, hence possibly improving ENSO predictability and explaining ENSO biennal variability. These studies essentially show that this IOD influence on ENSO evolution is indeed robust in observations and most CMIP climate models. Accounting for the IOD influence in linear ENSO forecasts based on the tropical Pacific recharge-discharge process increases the explained variance by 10-30% at 14 months lead. This IOD influence on the ENSO forecast skill appears stronger than that of the Indian Ocean Basin-wide warming/cooling or ENSO itself. However, its underlying mechanisms are still debated. Here we use dedicated experiments from atmospheric and oceanic numerical models, and a conceptual approach based on the Pacific ocean linear response to a wind pulse, to investigate the mechanisms by which the IOD influences ENSO evolution. Our results suggest that: (1) the atmospheric bridge (through atmospheric teleconnections) dominates the oceanic bridge (through the Indonesian throughflow); (2) the temporal change of west Pacific zonal wind stress over a six month period (e.g. related to IOD demise) matters as much as the wind seasonal anomaly for the dynamical response of the equatorial Pacific; (3) the IOD eastern pole, and its demise, is the main driver of this wind change. The abrupt demise of the IOD eastern pole favours a fast temporal change of the zonal wind in the western Pacific between fall and winter-spring, thereby favouring ENSO phase transition. Revisiting statistical approaches by using relative sea surface temperature (i.e. with tropical mean removed) confirms

  20. Impact of Icebergs on Net Primary Productivity in the Southern Ocean

    Science.gov (United States)

    Wu, Shuang-Ye; Hou, Shugui

    2017-04-01

    Productivity in the Southern Ocean (SO) is iron-limited, and supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine environment. However, recent studies show that icebergs could provide comparable amount of bioavailable iron to the SO as aeolian dust. In addition, small scale areal studies suggest increased concentrations of chlorophyll, krill, and seabirds surrounding icebergs. Based on previous research, this study aims to examine whether iceberg occurrence has a significant impact on marine productivity at the scale of the SO, using remote sensing data of iceberg occurrences and ocean net primary productivity (NPP) covering the period 2002-2014. The impacts of both large and small icebergs are examined in four major ecological zones of the SO: the continental shelf zone (CSZ), the seasonal ice zone (SIZ), the permanent open ocean zone (POOZ) and the polar front zone (PFZ). We found that both large and small icebergs have an observable positive impact on NPP, but their impacts vary in different zones. Small icebergs on average increase NPP in most iron deficient zones: by 21% for the SIZ, 16% for the POOZ, and 12% for the PFZ, but have relatively small effect in the CSZ where iron is supplied from melt water and sediment input from the continent. Large icebergs on average increase the NPP by about 10%. Their impacts are stronger at higher latitudes, where they are more concentrated. From 1992-2014, there is a significant increasing trend for both small and large icebergs. The increase was most rapid in the early 2000s, and has levelled off since then. As the climate continues to warm, the Antarctic Ice Sheet is expected to experience increased mass loss as a whole, which could lead to more icebergs in the region. Based on our study, this could result in higher level of NPP in the SO as a whole, providing a negative feedback for global warming.

  1. Wide range of mercury contamination in chicks of southern ocean seabirds.

    Science.gov (United States)

    Blévin, Pierre; Carravieri, Alice; Jaeger, Audrey; Chastel, Olivier; Bustamante, Paco; Cherel, Yves

    2013-01-01

    Using top predators as sentinels of the marine environment, Hg contamination was investigated within the large subantarctic seabird community of Kerguelen Islands, a remote area from the poorly known Southern Indian Ocean. Chicks of 21 sympatric seabirds presented a wide range of Hg concentrations, with the highest contaminated species containing ~102 times more feather Hg than the less contaminated species. Hence, Kerguelen seabirds encompass the whole range of chick feather Hg values that were previously collected worldwide in poorly industrialized localities. Using stable isotopes, the effects of foraging habitats (reflected by δ(13)C) and trophic positions (reflected by δ(15)N) on Hg concentrations were investigated. Species-related Hg variations were highly and positively linked to feather δ(15)N values, thus highlighting the occurrence of efficient Hg biomagnification processes within subantarctic marine trophic webs. By contrast, Hg contamination overall correlated poorly with feeding habitats, because of the pooling of species foraging within different isotopic gradients corresponding to distinct seabird habitats (benthic, pelagic, neritic and oceanic). However, when focusing on oceanic seabirds, Hg concentration was related to feather δ(13)C values, with species feeding in colder waters (lower δ(13)C values) south of Kerguelen Islands being less prone to be contaminated than species feeding in northern warmer waters (higher δ(13)C values). Within the context of continuous increase in global Hg emissions, Kerguelen Islands that are located far away from anthropogenic sources can be considered as an ideal study site to monitor the temporal trend of global Hg contamination. The present work helps selecting some seabird species as sentinels of environmental pollution according to their high Hg concentrations and their contrasted foraging ecology.

  2. Wide range of mercury contamination in chicks of southern ocean seabirds.

    Directory of Open Access Journals (Sweden)

    Pierre Blévin

    Full Text Available Using top predators as sentinels of the marine environment, Hg contamination was investigated within the large subantarctic seabird community of Kerguelen Islands, a remote area from the poorly known Southern Indian Ocean. Chicks of 21 sympatric seabirds presented a wide range of Hg concentrations, with the highest contaminated species containing ~102 times more feather Hg than the less contaminated species. Hence, Kerguelen seabirds encompass the whole range of chick feather Hg values that were previously collected worldwide in poorly industrialized localities. Using stable isotopes, the effects of foraging habitats (reflected by δ(13C and trophic positions (reflected by δ(15N on Hg concentrations were investigated. Species-related Hg variations were highly and positively linked to feather δ(15N values, thus highlighting the occurrence of efficient Hg biomagnification processes within subantarctic marine trophic webs. By contrast, Hg contamination overall correlated poorly with feeding habitats, because of the pooling of species foraging within different isotopic gradients corresponding to distinct seabird habitats (benthic, pelagic, neritic and oceanic. However, when focusing on oceanic seabirds, Hg concentration was related to feather δ(13C values, with species feeding in colder waters (lower δ(13C values south of Kerguelen Islands being less prone to be contaminated than species feeding in northern warmer waters (higher δ(13C values. Within the context of continuous increase in global Hg emissions, Kerguelen Islands that are located far away from anthropogenic sources can be considered as an ideal study site to monitor the temporal trend of global Hg contamination. The present work helps selecting some seabird species as sentinels of environmental pollution according to their high Hg concentrations and their contrasted foraging ecology.

  3. Rapid nitrification of wastewater ammonium near coastal ocean outfalls, Southern California, USA

    Science.gov (United States)

    McLaughlin, Karen; Nezlin, Nikolay P.; Howard, Meredith D. A.; Beck, Carly D. A.; Kudela, Raphael M.; Mengel, Michael J.; Robertson, George L.

    2017-02-01

    In the southern California Bight (SCB), there has been a longstanding hypothesis that anthropogenic nutrient loading is insignificant compared to the nutrient loading from upwelling. However, recent studies have demonstrated that, in the nearshore environment, nitrogen (N) flux from wastewater effluent is equivalent to the N flux from upwelling. The composition of the N pool and N:P ratios of wastewater and upwelled water are very different and the environmental effects of wastewater discharges on coastal systems are not well characterized. Capitalizing on routine maintenance of the Orange County Sanitation District's ocean outfall, wherein a wastewater point source was ;turned off; in one area and ;turned on; in another for 23 days, we were able to document changes in coastal N cycling, specifically nitrification, related to wastewater effluent. A ;hotspot; of ammonium (NH4+) and nitrite (NO2-) occurred over the ocean outfall under normal operations and nitrification rates were significantly higher offshore when the deeper outfall pipe was operating. These rates were sufficiently high to transform all effluent NH4+ to nitrate (NO3-). The dual isotopic composition of dissolved NO3- (δ15NNO3 and δ18ONO3) indicated that N-assimilation and denitrification were low relative to nitrification, consistent with the relatively low chlorophyll and high dissolved oxygen levels in the region during the study. The isotopic composition of suspended particulate organic matter (POM) recorded low δ15NPN and δ13CPN values around the outfall under normal operations suggesting the incorporation of ;nitrified; NO3- and wastewater dissolved organic carbon into POM. Our results demonstrate the critical role of nitrification in nitrogen cycling in the nearshore environment of urban oceans.

  4. Interannual surface variability of the Southern Pacific Ocean in relation to the SAM pattern

    Science.gov (United States)

    Cotroneo, Yuri; Menna, Milena; Falco, Pierpaolo; Poulain, Pierre Marie

    2017-04-01

    Drifter and satellite data are used to define the response of the Pacific Sector of the Southern Ocean (PSSO) to the large scale climatic pattern (Southern Annular Mode index - SAMI) in the period 1995-2015. The SAMI, defined as the mean sea level pressure difference between the 40° S and 65°S latitudes (Marshall et al., 2003), affects the eddy activity of the Southern Ocean and consequently the large-scale zonal transport in the Antarctic Circumpolar Current (ACC; Meredith and Hoggs, 2006; Hogg et al., 2014). Drifter data were primarily corrected for the wind-induced slip and currents (Ekman), then used to estimate annual values of the Eddy Kinetic Energy (EKE) fields in bins of 2°x2° over the PSSO. Time series of the drifter EKEs were compared with the EKEs derived from altimeter data over the entire study area and with the temporal evolution of SAMI. A more quantitative evaluation of the surface eddy field response to the SAMI was performed counting the number and type (cyclonic or anticyclonic)of eddies produced in the whole PSSO and in correspondence of the Sub-Antarctic Front (SAF) and Polar Front (PF). The mean latitude of each front was determined using thermal criteria applied to a long time series of in situ XBT data collected by the Italian Antarctic Programme along the track between New Zealand and Antarctica from 1994 to 2016. Eddy counting was based on the results of the identification and tracking method performed by Chelton et al. (2011), retaining only those eddies with lifetimes of 4 weeks or longer. The drifter derived EKE shows a similar and quicker response to the SAMI variability with respect to the altimetry derived EKE; the time lag is of one year for drifters and of two years for the altimetry. Both the datasets reveal an anomalous behaviour of the EKE during the period 2003-2006. The SAMI variability induces a specific effect on the different frontal zones with changes in the number and type of eddy generated. Moreover the anomalous

  5. The monitoring of atmospheric mercury species in the Southern Indian Ocean at Amsterdam Island (38°S

    Directory of Open Access Journals (Sweden)

    Barret M.

    2013-04-01

    Full Text Available The role of oceans in the global cycle of mercury is still poorly characterized, mainly because of a lack a long-term data on atmospheric mercury concentrations in the remote Southern Ocean. In the frame of GMOS (Global Mercury Observation System, we present here the first results from a new monitoring station at Amsterdam Island in the Southern Indian Ocean. For the period January to April 2012, we recorded mean concentration of gaseous elemental mercury (GEM, reactive gaseous mercury (RGM and particulate-bounded mercury (PHg of 1.03 ng m−3, 0.37 and 0.34 pg m−3 respectively. While GEM concentrations showed little variations, RGM and PHg exhibited fast variations with alternation of value below the instrumental detection limit and maximum values up to 4 pg m−3.

  6. Rapid drawdown of Antarctica's Wordie Ice Shelf glaciers in response to ENSO/Southern Annular Mode-driven warming in the Southern Ocean

    Science.gov (United States)

    Walker, C. C.; Gardner, A. S.

    2017-10-01

    Here we investigate the largest acceleration in ice flow across all of Antarctica between ∼2008 InSAR and 2014 Landsat velocity mappings. This occurred in glaciers that used to feed into the Wordie Ice Shelf on the west Antarctic Peninsula, which rapidly disintegrated in ∼1989. Between 2008 and 2014, these glaciers experienced at least a threefold increase in surface elevation drawdown relative to the 2002-2008 time period. After ∼20 yrs of relative stability, it is unlikely that the ice shelf collapse played a role in the large response. Instead, we find that the rapid acceleration and surface drawdown is linked to enhanced melting at the ice-ocean boundary, attributable to changes in winds driven by global atmospheric circulation patterns, namely the El Niño-Southern Oscillation (ENSO) and Southern Annular Mode (SAM), linking changes in grounded ice to atmospheric-driven ocean warming.

  7. Novel Methods for Optically Measuring Whitecaps Under Natural Wave Breaking Conditions in the Southern Ocean

    Science.gov (United States)

    Randolph, K. L.; Dierssen, H. M.; Cifuentes-Lorenzen, A.; Balch, W. M.; Monahan, E. C.; Zappa, C. J.; Drapeau, D.; Bowler, B.

    2016-02-01

    Breaking waves on the ocean surface mark areas of significant importance to air-sea flux estimates of gas, aerosols, and heat. Traditional methods of measuring whitecap coverage using digital photography can miss features that are small in size or do not show high enough contrast to the background. The geometry of the images collected captures the near surface, bright manifestations of the whitecap feature and miss a portion of the bubble plume that is responsible for the production of sea salt aerosols and the transfer of lower solubility gases. Here, a novel method for accurately measuring both the fractional coverage of whitecaps and the intensity and decay rate of whitecap events using above water radiometry is presented. The methodology was developed using data collected during the austral summer in the Atlantic sector of the Southern Ocean under a large range of wind (speeds of 1 to 15 m s-1) and wave (significant wave heights 2 to 8 m) conditions as part of the Southern Ocean Gas Exchange experiment. Whitecap metrics were retrieved by employing a magnitude threshold based on the interquartile range of the radiance or reflectance signal for a single channel (411 nm) after a baseline removal, determined using a moving minimum/maximum filter. Breaking intensity and decay rate metrics were produced from the integration of, and the exponential fit to, radiance or reflectance over the lifetime of the whitecap. When compared to fractional whitecap coverage measurements obtained from high resolution digital images, radiometric estimates were consistently higher because they capture more of the decaying bubble plume area that is difficult to detect with photography. Radiometrically-retrieved whitecap measurements are presented in the context of concurrently measured meteorological (e.g., wind speed) and oceanographic (e.g., wave) data. The optimal fit of the radiometrically estimated whitecap coverage to the instantaneous wind speed, determined using ordinary least

  8. Coastal zone color scanner pigment concentrations in the Southern Ocean and relationships to geophysical surface features

    Science.gov (United States)

    Comiso, J. C.; McClain, C. R.; Sullivan, C. W.; Ryan, J. P.; Leonard, C. L.

    1993-02-01

    The spatial and seasonal distributions of phytoplankton pigment concentration over the entire southern ocean have been studied for the first time using the coastal zone color scanner historical data set (from October 1978 through June 1986). Enhanced pigment concentrations are observed between 35°S and 55°S throughout the year, with such enhanced regions being more confined to the south in the austral summer and extending further north in the winter. North and south of the polar front, phytoplankton blooms (>1 mg/m3) are not uniformly distributed around the circumpolar region. Instead, blooms appear to be located in regions of ice retreat (or high melt areas) such as the Scotia Sea and the Ross Sea, in relatively shallow areas (e.g., the Patagonian and the New Zealand shelves), in some regions of Ekman upwelling like the Tasman Sea, and near areas of high eddy kinetic energy such as the Agulhas retroflection. Among all features examined by regression analysis, bathymetry appears to be the one most consistently correlated with pigments (correlation coefficient being about -0.3 for the entire region). The cause of negative correlation with bathymetry is unknown but is consistent with the observed abundance of iron in shallow areas in the Antarctic region. It is also consistent with resuspension of phytoplankton cells by wind-induced mixing, especially in shallow waters. On the other hand, in the deep ocean (especially at latitudes nutrients may be limiting), upwelling induced by topographic features may cause resupply of nutrients to the surface and shoaling of the subsurface chlorophyll maximum. Low pigment values are common at low latitudes and in regions of high wind stress, where deep mixing and net loss of surface pigment occur. Nutrients (phosphate, nitrate, and silicate) are found to correlate significantly with pigments when the entire southern ocean is considered, but south of 55°S the correlation is poor, probably because the Antarctic waters are not

  9. An assessment of the role of the k-e vertical mixing scheme in the simulation of Southern Ocean upper dynamics

    CSIR Research Space (South Africa)

    Boodhraj, K

    2016-11-01

    Full Text Available Following the work done by Reffrey, Calone and Bourdalle-Badie (2015) we implemented a one dimensional (1D) ocean physical model in the sub-Antarctic Southern Ocean using the Nucleus for the European Modelling of the Ocean(NEMO) model. The 1D model...

  10. An Integrative Approach to Understand a Rich Ecosystem in the Southern Ocean From Carbon to Top Predators

    Science.gov (United States)

    Cotté, C.; d'Ovidio, F.; Behagle, N.; Roudaut, G.; Brehmer, P.; Bost, C. A.; Guinet, C.; Cherel, Y.

    2016-02-01

    Large parts of the Southern Ocean waters are rich in macronutrients, but blooms of phytoplankton occur in a patchy and localized way. This is in part due to the presence of sources of limiting micronutrients scattered along the continental breaks, whose inputs are stirred into the open ocean very inhomogeneously. At the highest levels of ecosystems, top predators reveal areas of ecological importance where no other information is available on the underpinning trophic web. A dramatic example of this situation is provided by the region around Kerguelen archipelago, in the Southern Indian Ocean. Here, the high nutrient, low iron waters transported eastward by the Antarctic Circumpolar Current encounter the iron-rich Kerguelen shelf break. As a consequence, a plume of high chlorophyll water develops east of the plateau, extending from the shelf break for hundreds of kms into the open ocean, and strongly modulated by the intense mesoscale activity. Large populations of top predators use this area to forage during the summer periode, despite very scarce knowledge on their micronektonic prey and on mid-trophic oragnisms. By combining in campaign data, satellite observations, and biologging, we adopt an end-to-end approach and describe the mechanisms by which the ocean physics impacts the regional biogeochemistry firstly by redistributing iron-rich coastal waters into the open ocean, and then by focusing on the trophic interactions. We consider in particular the role of mesoscale eddies and submesoscale fronts, whose temporal dynamics resonates with biological processes and organises the variability of ecosystems.

  11. The discovery of new deep-sea hydrothermal vent communities in the southern ocean and implications for biogeography.

    Directory of Open Access Journals (Sweden)

    Alex D Rogers

    2012-01-01

    Full Text Available Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp., stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae, bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more

  12. The Discovery of New Deep-Sea Hydrothermal Vent Communities in the Southern Ocean and Implications for Biogeography

    Science.gov (United States)

    Rogers, Alex D.; Tyler, Paul A.; Connelly, Douglas P.; Copley, Jon T.; James, Rachael; Larter, Robert D.; Linse, Katrin; Mills, Rachel A.; Garabato, Alfredo Naveira; Pancost, Richard D.; Pearce, David A.; Polunin, Nicholas V. C.; German, Christopher R.; Shank, Timothy; Boersch-Supan, Philipp H.; Alker, Belinda J.; Aquilina, Alfred; Bennett, Sarah A.; Clarke, Andrew; Dinley, Robert J. J.; Graham, Alastair G. C.; Green, Darryl R. H.; Hawkes, Jeffrey A.; Hepburn, Laura; Hilario, Ana; Huvenne, Veerle A. I.; Marsh, Leigh; Ramirez-Llodra, Eva; Reid, William D. K.; Roterman, Christopher N.; Sweeting, Christopher J.; Thatje, Sven; Zwirglmaier, Katrin

    2012-01-01

    Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR) in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp.), stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae), bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more complex than

  13. Ocean control of the breeding regime of the sooty tern in the southwest Indian Ocean

    Science.gov (United States)

    Jaquemet, S.; Le Corre, M.; Quartly, G. D.

    2007-01-01

    Food availability, which is often seasonal, is regarded as a key factor in the breeding success of seabirds. In oceanic tropical areas, the resources are mostly patchy and ephemeral at the surface, and the seasonality is less marked than at higher latitudes. Such a situation influences greatly the breeding strategies of the oceanic seabird species. We conducted a comparative study of the breeding phenology of the sooty tern ( Sterna fuscata) in relation to the local and regional oceanographic conditions around the four major colonies (Europa, Juan de Nova, Lys and Bird Islands) of the southwest Indian Ocean. Over the 1997-2003 period, around all the studied locations, the sea-surface temperature (SST) and the chlorophyll concentration in the Mozambique Channel and the Seychelles area showed clear seasonal differences related to the southern climate and the monsoon phenomena. The breeding activity is synchronized at each studied colony, but the timings are very different. Seasonal reproduction occurs in austral winter at Europa and Bird Island and in austral summer at Juan de Nova; at Lys Island the reproduction is non-seasonal. For the seasonal colonies, there is a large monthly change in SST just before the beginning of reproduction, which is a proxy indicating the annual phytoplankton bloom. This variation is accompanied by the development of oceanic features such as fronts that favour aggregation of prey, and may also play an important role in the presence of schools of surface tuna, which are very important for the foraging success of sooty terns. Conversely, around Lys Island the seasonal variations of the marine environment do not lead to pronounced development of oceanic structures, and consequently, the longer-lasting phytoplankton bloom could explain the non-seasonal breeding regime there. Further studies will help discern the advantages and disadvantages of seasonal and non-seasonal reproduction regime in response to unpredictable fluctuations of the

  14. The effects of natural iron fertilisation on deep-sea ecology: the Crozet Plateau, Southern Indian Ocean.

    Science.gov (United States)

    Wolff, George A; Billett, David S M; Bett, Brian J; Holtvoeth, Jens; FitzGeorge-Balfour, Tania; Fisher, Elizabeth H; Cross, Ian; Shannon, Roger; Salter, Ian; Boorman, Ben; King, Nicola J; Jamieson, Alan; Chaillan, Frédéric

    2011-01-01

    The addition of iron to high-nutrient low-chlorophyll (HNLC) oceanic waters stimulates phytoplankton, leading to greater primary production. Large-scale artificial ocean iron fertilization (OIF) has been proposed as a means of mitigating anthropogenic atmospheric CO(2), but its impacts on ocean ecosystems below the photic zone are unknown. Natural OIF, through the addition of iron leached from volcanic islands, has been shown to enhance primary productivity and carbon export and so can be used to study the effects of OIF on life in the ocean. We compared two closely-located deep-sea sites (∼400 km apart and both at ∼4200 m water depth) to the East (naturally iron fertilized; +Fe) and South (HNLC) of the Crozet Islands in the southern Indian Ocean. Our results suggest that long-term geo-engineering of surface oceanic waters via artificial OIF would lead to significant changes in deep-sea ecosystems. We found that the +Fe area had greater supplies of organic matter inputs to the seafloor, including polyunsaturated fatty acid and carotenoid nutrients. The +Fe site also had greater densities and biomasses of large deep-sea animals with lower levels of evenness in community structuring. The species composition was also very different, with the +Fe site showing similarities to eutrophic sites in other ocean basins. Moreover, major differences occurred in the taxa at the +Fe and HNLC sites revealing the crucial role that surface oceanic conditions play in changing and structuring deep-sea benthic communities.

  15. Against the flow: evidence of multiple recent invasions of warmer continental shelf waters by a Southern Ocean brittle star

    Directory of Open Access Journals (Sweden)

    Chester John Sands

    2015-06-01

    Full Text Available The Southern Ocean is anomalously rich in benthos. This biodiversity is native, mostly endemic and perceived to be uniquely threatened from climate- and anthropogenically- mediated invasions. Major international scientific effort throughout the last decade has revealed more connectivity than expected between fauna north and south of the worlds strongest marine barrier – the Polar Front (the strongest jet of the Antarctic Circumpolar Current. To date though, no research has demonstrated any radiations of marine taxa out from the Southern Ocean, except at abyssal depths (where conditions differ much less. Our phylogeographic investigation of one of the most ubiquitous and abundant clades at high southern latitudes, the ophiuroids (brittlestars, shows that one of them, Ophiura lymani, has gone against the flow. Remarkably our genetic data suggest that O. lymani has successfully invaded the South American shelf from Antarctica at least three times, in recent (Pleistocene radiation. Many previous studies have demonstrated links within clades across the PF this is the first in which northwards directional movement of a shelf-restricted species is the only convincing explanation. Rapid, recent, regional warming is likely to facilitate multiple range shift invasions into the Southern Ocean, whereas movement of cold adapted fauna (considered highly stenothermal out of the Antarctic to warmer shelves has, until now, seemed highly unlikely.

  16. Explanations for Temperature Increases in the Northern and Southern Atlantic Ocean are Proposed

    Science.gov (United States)

    Cimorelli, S. A.

    2012-04-01

    Primarily, consider some background hypotheses in the first paragraph: Three Types of mechanisms for Stellar Origin, Formation and Evolution are hypothesized. The first type (A) is well known; whereas, the other two (B&C) are new and proposed herein. The type A process, the presently universally accepted process, consists of the three phases of gravitation, followed by accretion, followed by fragmentation. In a Type B process, a star originates as an expanded, modified, category 3 Black Hole (BH) [1], with none or little help from gravitation/accretion, that begins to radiate, and continues to grow into a star. In a Type C process, a star would originate from a combination of the mechanisms described above for Type B and A. This mechanism, Type C, is perhaps the most common type. This type starts as an expanded, modified, category 3 BH inside of a gas and dust cloud. This then serves as the nucleus that starts the subsequent gravitation/accretion process; however, it greatly accelerates the accretion/formation process as in a standard Type A process. This mechanism could then explain how some super-cluster complexes, which have been estimated would take 40 to 60 billion years to form, can occur in a universe of a much younger age, i.e. 13.7 billion years. Also, consider that the ratio of the 'surface area to volume' is greater in a relatively smaller sphere; which would cause that smaller body of limited energy to cool off'/down, faster; however to continue to grow. A suggested sequence to explain why the Northern (South Greenland) and Southern Regions of the Atlantic Ocean are getting warmer is proposed: As the earth grows, two things occur, among others [1]. It is hypothesized the earth is expanding, circumferentially, about 3 cm per year at the equator (1 cm in the Atlantic, and 2 cm in the Pacific), rather than just 1 cm at the center of the Atlantic, as is commonly accepted. The earth may be expanding at an even greater rate, longitudinally (north and south

  17. Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age

    Science.gov (United States)

    Wang, Xingchen Tony; Sigman, Daniel M.; Prokopenko, Maria G.; Adkins, Jess F.; Robinson, Laura F.; Hines, Sophia K.; Chai, Junyi; Studer, Anja S.; Martínez-García, Alfredo; Chen, Tianyu; Haug, Gerald H.

    2017-03-01

    The Southern Ocean regulates the ocean’s biological sequestration of CO2 and is widely suspected to underpin much of the ice age decline in atmospheric CO2 concentration, but the specific changes in the region are debated. Although more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the 15N/14N of fossil-bound organic matter in the stony deep-sea coral Desmophyllum dianthus, a tool for reconstructing surface ocean nutrient conditions. The central robust observation is of higher 15N/14N across the Southern Ocean during the Last Glacial Maximum (LGM), 18-25 thousand years ago. These data suggest a reduced summer surface nitrate concentration in both the Antarctic and Subantarctic Zones during the LGM, with little surface nitrate transport between them. After the ice age, the increase in Antarctic surface nitrate occurred through the deglaciation and continued in the Holocene. The rise in Subantarctic surface nitrate appears to have had both early deglacial and late deglacial/Holocene components, preliminarily attributed to the end of Subantarctic iron fertilization and increasing nitrate input from the surface Antarctic Zone, respectively.

  18. Mechanisms controlling export production at the LGM: Effects of changes in oceanic physical fields and atmospheric dust deposition

    Science.gov (United States)

    Oka, Akira; Abe-Ouchi, Ayako; Chikamoto, Megumi O.; Ide, Tomoyuki

    2011-06-01

    Using a biogeochemical ocean model that includes the iron cycle, we carry out preindustrial (control, CTL) and glacial (Last Glacial Maximum, LGM) climate simulations focusing on changes in export production (EP). The model successfully reproduces general trends of a paleoclimate reconstruction of EP at the LGM except over the Atlantic Ocean. By conducting a series of sensitivity simulations, we investigate the mechanism controlling EP at the LGM in each basin. In the Southern Ocean, the model successfully reproduces the dipole pattern of the paleoreconstruction: the higher-latitude decrease and lower-latitude increase of EP. It is found that the lower-latitude increase of EP comes from iron fertilization effects by enhanced dust deposition, while the higher-latitude decrease of EP is caused by the reduction of surface shortwave due to spreading of sea ice there. We also find that increased dust input in other basins remotely affects EP in the Southern Ocean. In the Pacific Ocean, the model suggests that iron fertilization effects are dominant in open ocean regions. In the Atlantic Ocean, the model simulates overall reduction of EP, whereas the paleoreconstruction suggests the increase in some regions. We propose that the Atlantic response is strongly affected by distribution of iron limitation in a control climate. In our CTL simulation, the biological production is limited not by iron but by phosphate in the Atlantic Ocean, which leads to the decrease of EP in spite of the significant increase of dust deposition there. It is implied that the accurate evaluation of iron limitation in the present ocean is critical for evaluating changes in EP and associated reduction of atmospheric CO2 concentration at the LGM.

  19. The importance of oceanographic fronts to marine birds and mammals of the southern oceans

    Science.gov (United States)

    Bost, C. A.; Cotté, C.; Bailleul, F.; Cherel, Y.; Charrassin, J. B.; Guinet, C.; Ainley, D. G.; Weimerskirch, H.

    2009-10-01

    During the last 30 years, at-sea studies of seabirds and marine mammals in the oceans south of the Subtropical Front have described an association with major frontal areas. More recently, the advancement in microtechnology has allowed the tracking of individuals and investigations into how these marine predators actually use the frontal zones. In this review, we examine 1) the relative importance to apex predators of the different frontal zones in terms of spatial distribution and carbon flux; 2) the processes that determine their preferential use; and 3) how the mesoscale dynamics of frontal structures drive at-sea foraging strategies of these predators. We review published results from southern waters and place them in a broader context with respect to what has been learned about the importance of fronts in oceans farther north. Some fronts constitute important boundaries for seabird communities in southern waters. At a mesoscale the maximum values of seabird diversity and abundance correspond to the location of the main fronts. At-sea surveys show a strong curvilinear correlation between seabird abundance and sea surface temperatures. High mean species richness and diversity for whales and seabirds are consistently associated with the southern water mass boundary of the Antarctic Circumpolar Current, the Subtropical Front and the Subantarctic Front; in the case of the Polar Front mean seabird densities are more variable. At small-scales, variation in seabird occurrence has been directly related to the processes at fronts in a limited number of cases. A significant positive relation was found between some plankton feeding species and frontal temperature gradient-phytoplankton variables. Telemetric studies have revealed that several apex predators (penguins, albatrosses, seals) perform long, directed foraging trips either to the Subtropical front or Polar Front, depending on locality. Seabirds with low flight costs, such as albatrosses, are able to reach fronts at

  20. Southern Hemisphere anticyclonic circulation drives oceanic and climatic conditions in late Holocene southernmost Africa

    Science.gov (United States)

    Hahn, Annette; Schefuß, Enno; Andò, Sergio; Cawthra, Hayley C.; Frenzel, Peter; Kugel, Martin; Meschner, Stephanie; Mollenhauer, Gesine; Zabel, Matthias

    2017-06-01

    Due to the high sensitivity of southern Africa to climate change, a reliable understanding of its hydrological system is crucial. Recent studies of the regional climatic system have revealed a highly complex interplay of forcing factors on precipitation regimes. This includes the influence of the tropical easterlies, the strength of the southern hemispheric westerlies as well as sea surface temperatures along the coast of the subcontinent. However, very few marine records have been available in order to study the coupling of marine and atmospheric circulation systems. Here we present results from a marine sediment core, recovered in shallow waters off the Gouritz River mouth on the south coast of South Africa. Core GeoB18308-1 allows a closer view of the last ˜ 4 kyr. Climate sensitive organic proxies, like the distribution and isotopic composition of plant-wax lipids as well as indicators for sea surface temperatures and soil input, give information on oceanographic and hydrologic changes during the recorded time period. Moreover, the micropaleontology, mineralogical and elemental composition of the sediments reflect the variability of the terrigenous input to the core site. The combination of down-core sediment signatures and a catchment-wide provenance study indicate that the Little Ice Age ( ˜ 300-650 cal yr BP) was characterized by climatic conditions favorable to torrential flood events. The Medieval Climate Anomaly ( ˜ 950-650 cal yr BP) is expressed by lower sea surface temperatures in the Mossel Bay area and humid conditions in the Gouritz River catchment. These new results suggest that the coincidence of humid conditions and cooler sea surface temperatures along the south coast of South Africa resulted from a strengthened and more southerly anticyclonic circulation. Most probably, the transport of moisture from the Indian Ocean by strong subtropical easterlies was coupled with Agulhas Bank upwelling pulses, which were initiated by an increase in

  1. New Hampshire / Southern Maine Ocean Uses Atlas: Non-Consumptive sector

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Uses Atlas Project is an innovative partnership between the Coastal Response Research Center (CRRC) and NOAA's Office of Ocean and Coastal Resource...

  2. Temperature, salinity, nutrients, and other data from CTD and bottle casts in the Southern Ocean (> 60 South) from the R/V NATHANIEL B. PALMER from 14 September 1994 to 12 October 1994 (NODC Accession 0000481)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This report includes the primary ocean station data collected in the Pacific sector of the Southern Ocean during cruise 9405 of the Nathaniel B. Palmer. The cruise...

  3. Atmospheric trace elements in aerosols observed over the Southern Ocean and coastal East Antarctica

    Directory of Open Access Journals (Sweden)

    Guojie Xu

    2014-11-01

    Full Text Available Atmospheric aerosol samples were collected over the Southern Ocean (SO and coastal East Antarctica (CEA during the austral summer of 2010/11. Samples were analysed for trace elements, including Na, Mg, K, Al, Fe, Mn, Ni, Cd and Se, by inductively coupled plasma mass spectrometry (ICP-MS. The mean atmospheric concentrations over the SO were 1100 ng m−3 for Na, 190 ng m−3 for Mg, 150 ng m−3 for Al, 14 ng m−3 for Fe, 0.46 ng m−3 for Mn and 0.25 ng m−3 for Se. Over CEA, the mean concentrations were 990 ng m−3 for Na, 180 ng m−3 for Mg, 190 ng m−3 for Al, 26 ng m−3 for Fe, 0.70 ng m−3 for Mn and 0.29 ng m−3 for Se. Particle size distributions, enrichment factors (EFs and correlation analysis indicate that Na, Mg and K mainly came from the marine source, while Al, Fe and Mn were mainly from the crustal source, which also contributed to Mg and K over CEA. High EFs were associated with Ni, Cd and Se, suggesting likely contributions from mixed sources from the Antarctic continent, long-range transport, marine biogenic emissions and anthropogenic emissions. Sea-salt elements (Na, Mg, K were mainly accumulated in the coarse mode, and crustal elements (Al, Fe, Mn presented a bimodal size distribution pattern. Bioactive elements (Fe, Ni, Cd were enriched in the fine mode, especially with samples collected over the SO, possibly affecting biogeochemical cycles in this oceanic region.

  4. The residual circulation of the Southern Ocean: Which spatio-temporal scales are needed?

    Science.gov (United States)

    Ballarotta, Maxime; Drijfhout, Sybren; Kuhlbrodt, Till; Döös, Kristofer

    2013-04-01

    The Southern Ocean circulation consists of a complicated mixture of processes and phenomena that arise at different time and spatial scales which need to be parametrized in the state-of-the-art climate models. The temporal and spatial scales that give rise to the present-day residual mean circulation are here investigated by calculating the Meridional Overturning Circulation (MOC) in density coordinates from an eddy-permitting global model. The region sensitive to the temporal decomposition is located between 38°S and 63°S, associated with the eddy-induced transport. The "Bolus" component of the residual circulation corresponds to the eddy-induced transport. It is dominated by timescales between 1 month and 1 year. The temporal behavior of the transient eddies is examined in splitting the "Bolus" component into a "Seasonal", an "Eddy" and an "Inter-monthly" component, respectively representing the correlation between density and velocity fluctuations due to the average seasonal cycle, due to mesoscale eddies and due to large-scale motion on timescales longer than one month that is not due to the seasonal cycle. The "Seasonal" bolus cell is important at all latitudes near the surface. The "Eddy" bolus cell is dominant in the thermocline between 50°S and 35°S and over the whole ocean depth at the latitude of the Drake Passage. The "Inter-monthly" bolus cell is important in all density classes and is maximal in the Brazil-Malvinas Confluence and the Agulhas Return Current. The spatial decomposition indicates that a large part of the Eulerian mean circulation is recovered for spatial scales larger than 11.25°, implying that small-scale meanders in the Antarctic Circumpolar Current (ACC), near the Subantarctic and Polar Fronts, and near the Subtropical Front are important in the compensation of the Eulerian mean flow.

  5. Distribution and recurrence of phytoplankton blooms around South Georgia, Southern Ocean

    Directory of Open Access Journals (Sweden)

    I. Borrione

    2013-01-01

    Full Text Available South Georgia phytoplankton blooms are amongst the largest of the Southern Ocean and are associated with a rich ecosystem and strong atmospheric carbon drawdown. Both aspects depend on the intensity of blooms, but also on their regularity. Here we use data from 12 yr of SeaWiFS (Sea-viewing Wide Field-of-view Sensor ocean colour imagery and calculate the frequency of bloom occurrence (FBO to re-examine spatial and temporal bloom distributions. We find that upstream of the island and outside the borders of the Georgia Basin, blooms occurred in less than 4 out of the 12 yr (FBO < 4. In contrast, FBO was mostly greater than 8 downstream of the island, i.e., to the north and northwest, and in places equal to 12, indicating that blooms occurred every year. The typical bloom area, defined as the region where blooms occurred in at least 8 out of the 12 yr, covers the entire Georgia Basin and the northern shelf of the island. The time series of surface chlorophyll a (Chl a concentrations averaged over the typical bloom area shows that phytoplankton blooms occurred in every year between September 1997 and September 2010, and that Chl a values followed a clear seasonal cycle, with concentration peaks around December followed in many years by a second peak during late austral summer or early autumn, suggesting a bi-modal bloom pattern. The bloom regularity we describe here is in contrast with results of Park et al. (2010 who used a significantly different study area including regions that almost never exhibit bloom conditions.

  6. Geological record and reconstruction of the late Pliocene impact of the Eltanin asteroid in the Southern Ocean.

    Science.gov (United States)

    Gersonde, R; Kyte, F T; Bleil, U; Diekmann, B; Flores, J A; Gohl, K; Grahl, G; Hagen, R; Kuhn, G; Sierro, F J; Volker, D; Abelmann, A; Bostwick, J A

    1997-11-27

    In 1995, an expedition on board the research vessel FS Polarstern explored the impact site of the Eltanin asteroid in the Southern Ocean, the only known asteroid impact into a deep ocean basin. Analyses of the geological record of the impact region place the event in the late Pliocene (approximately 2.15 Myr) and constrain the size of the asteroid to be >1 km. The explosive force inferred for this event places it at the threshold of impacts believed to have global consequences, and its study should therefore provide a baseline for the reconstruction and modelling of similar events, which are common on geological timescales.

  7. Ertel Potential Vorticity versus Bernoulli Streamfunction in Earth's Southern Ocean: Comparison with the Atmospheres of Earth, Mars, Jupiter and Saturn

    Science.gov (United States)

    Dowling, Timothy E.; Stanley, Geoff; Bradley, Mary Elizabeth; Marshall, David P.

    2017-10-01

    We are working to expand the comparative planetology of vorticity-streamfunction correlations established for the atmospheres of Earth, Mars, Jupiter and Saturn to include Earth’s Antarctic Circumpolar Current (ACC), which is the only oceanic jet that encircles the planet. Interestingly, the ACC and its eddies scale like atmospheric jets and eddies on Jupiter and Saturn---the Southern Ocean is a “giant planet” with a zonal jet stream. Our input is the Southern Ocean State Estimate (SOSE; Mazloff et al 2010, J. Phys. Ocean. 40, 880-899), an optimal combination of observations and primitive-equation model that spans 2005-2010. Two hurdles not encountered in atmospheric work arise from the nonlinear equation of state of ocean water: non-zero helicity, which prevents the existence of truly neutral (analogous to adiabatic) surfaces, and the lack of a geostrophic streamfunction in general. We follow de Szoeke et al (2000, J. Phys. Ocean. 30, 2830-2852) to overcome these hurdles, regionally, by using orthobaric density as the vertical coordinate. In agreement with results for all atmospheres analyzed to date, scatter plots of Ertel potential vorticity, Q, versus Bernoulli streamfunction, B, on orthobaric density surfaces in the Southern Ocean are well correlated. The general shape of the correlation is like a hockey stick, with the “blade” corresponding to a broad horizontal region that spans the ACC, and the “handle” corresponding to shallow water. The same linear-regression Q versus B model employed for Mars is applied to the ACC (“blade”) signal. Results include that the deeper water on the equatorward side of the ACC is most prone to shear instability, and elsewhere the ACC is “supersonic” such that the net propagation of vorticity waves is eastward, not the usual westward. During the 6-year span of the SOSE data, there is a steady drift of the correlation to larger values at the top of the vertical profile, and to smaller values in the middle of

  8. Coastal ocean forecasting with an unstructured grid model in the southern Adriatic and northern Ionian seas

    Science.gov (United States)

    Federico, Ivan; Pinardi, Nadia; Coppini, Giovanni; Oddo, Paolo; Lecci, Rita; Mossa, Michele

    2017-01-01

    SANIFS (Southern Adriatic Northern Ionian coastal Forecasting System) is a coastal-ocean operational system based on the unstructured grid finite-element three-dimensional hydrodynamic SHYFEM model, providing short-term forecasts. The operational chain is based on a downscaling approach starting from the large-scale system for the entire Mediterranean Basin (MFS, Mediterranean Forecasting System), which provides initial and boundary condition fields to the nested system. The model is configured to provide hydrodynamics and active tracer forecasts both in open ocean and coastal waters of southeastern Italy using a variable horizontal resolution from the open sea (3-4 km) to coastal areas (50-500 m). Given that the coastal fields are driven by a combination of both local (also known as coastal) and deep-ocean forcings propagating along the shelf, the performance of SANIFS was verified both in forecast and simulation mode, first (i) on the large and shelf-coastal scales by comparing with a large-scale survey CTD (conductivity-temperature-depth) in the Gulf of Taranto and then (ii) on the coastal-harbour scale (Mar Grande of Taranto) by comparison with CTD, ADCP (acoustic doppler current profiler) and tide gauge data. Sensitivity tests were performed on initialization conditions (mainly focused on spin-up procedures) and on surface boundary conditions by assessing the reliability of two alternative datasets at different horizontal resolution (12.5 and 6.5 km). The SANIFS forecasts at a lead time of 1 day were compared with the MFS forecasts, highlighting that SANIFS is able to retain the large-scale dynamics of MFS. The large-scale dynamics of MFS are correctly propagated to the shelf-coastal scale, improving the forecast accuracy (+17 % for temperature and +6 % for salinity compared to MFS). Moreover, the added value of SANIFS was assessed on the coastal-harbour scale, which is not covered by the coarse resolution of MFS, where the fields forecasted by SANIFS

  9. A biomarker perspective on dust, productivity, and sea surface temperature in the Pacific sector of the Southern Ocean

    Science.gov (United States)

    Jaeschke, Andrea; Wengler, Marc; Hefter, Jens; Ronge, Thomas A.; Geibert, Walter; Mollenhauer, Gesine; Gersonde, Rainer; Lamy, Frank

    2017-05-01

    In this study, we present a new multiproxy data set of terrigenous input, marine productivity and sea surface temperature (SST) from 52 surface sediment samples collected along E-W transects in the Pacific sector of the Southern Ocean. Allochthonous terrigenous input was characterized by the distribution of plant wax n-alkanes and soil-derived branched glycerol dialkyl glycerol tetraethers (brGDGTs). 230Th-normalized burial of both compound groups were highest close to the potential sources in Australia and New Zealand and are strongly related to lithogenic contents (232Th), indicating common sources and transport. Detection of both long-chain n-alkanes and brGDGTs at the most remote sites in the open ocean strongly suggests a primarily eolian transport mechanism to at least 110°W, i.e. by prevailing westerly winds. Two independent organic SST proxies were used, the U37K‧ based on alkenones, and the TEX86 based on isoprenoid GDGTs. Both, U37K‧ and TEX86 indices show robust relationships with temperature over a temperature range between 0.5 and 20 °C, likely implying different seasonal and regional imprints on the temperature signal. Alkenone-based temperature estimates best reflect modern summer SST in the study area when using the polar calibration of Sikes et al. (1997). In contrast, TEX86-derived temperatures may reflect a subsurface signal rather than surface. 230Th-normalized burial of alkenones is highest close to the Subtropical Front and is positively related to the deposition of lithogenic material throughout the study area. In contrast, highest isoGDGT burial south of the Antarctic Polar Front may be largely controlled by diatom blooms, and thus high opal fluxes during austral summer.

  10. Carbon intake by zooplankton. Importance and role of zooplankton grazing in the Indian sector of the Southern Ocean

    Science.gov (United States)

    Mayzaud, P.; Tirelli, V.; Errhif, A.; Labat, J. P.; Razouls, S.; Perissinotto, R.

    Ingestion by mesozooplankton and micronekton was monitored during two of the ANTARES cruises in the Indian sector of the Southern Ocean in spring and summer. The composition of the mesozooplankton populations varied in space and with season. Copepods always dominated in number and biomass, but salps and pteropods were present in the northern part of the transect in summer. Five species of large copepod ( Calanus simillimus, Calanoides acutus, Rhincalanus gigas, Calanus propinquus and Metridia gerlachei) dominated the biomass with a North-South gradient. Smaller species ( Oithona spp., Ctenocalanus citer, Clausocalanus laticeps) were also present. Biomass showed a definite trend with highest levels towards the polar front zone and permanent open-ocean area. Feeding activity was monitored either for the total population (summer) or specific individuals (spring). In summer, depending on the area considered, grazing rates by mesozooplankton appeared to have a significant impact on phytoplankton primary production. In the northern part of the transect (polar front zone or PFZ), salps and to a minor extent pteropods and copepods contributed mostly to the feeding pressure. Maximum intensity was observed in the Coastal Antarctic Zone (CCSZ) where Euphausia superba (adults and calyptopis larvae) could ingest more than 100% of the daily primary production. In spring, the impact of copepods dominated the zooplankton community. Small calanoids and young stages of large species of copepods rather than adult stages were the dominant contributors to grazing pressure. In summer, respiration rates of the dominant copepod species showed that energy expenditure exceeded by far chlorophyll ingestion. This is generally interpreted as the consequence of ingestion of alternate non-chlorophyll food source. The inverse correlation between the biomass of microzooplankton and the area of maximum difference between grazing and respiration confirmed that in summer the protozoans are strongly

  11. Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron.

    Science.gov (United States)

    Hiscock, Michael R; Lance, Veronica P; Apprill, Amy M; Bidigare, Robert R; Johnson, Zackary I; Mitchell, B Greg; Smith, Walker O; Barber, Richard T

    2008-03-25

    It is well established that an increase in iron supply causes an increase in total oceanic primary production in many regions, but the physiological mechanism driving the observed increases has not been clearly identified. The Southern Ocean iron enrichment experiment, an iron fertilization experiment in the waters closest to Antarctica, resulted in a 9-fold increase in chlorophyll (Chl) concentration and a 5-fold increase in integrated primary production. Upon iron addition, the maximum quantum yield of photosynthesis (phi(m)) rapidly doubled, from 0.011 to 0.025 mol C.mol quanta(-1). Paradoxically, this increase in light-limited productivity was not accompanied by a significant increase in light-saturated productivity (P(max)(b)). P(max)(b), maximum Chl normalized productivity, was 1.34 mg C.mg Chl(-1).h(-1) outside and 1.49 mg C.mg Chl(-1).h(-1) inside the iron-enriched patch. The importance of phi(m) as compared with P(max)(b) in controlling the biological response to iron addition has vast implications for understanding the ecological response to iron. We show that an iron-driven increase in phi(m) is the proximate physiological mechanism affected by iron addition and can account for most of the increases in primary production. The relative importance of phi(m) over P(max)(b) in this iron-fertilized bloom highlights the limitations of often-used primary productivity algorithms that are driven by estimates of P(max)(b) but largely ignore variability in phi(m) and light-limited productivity. To use primary productivity models that include variability in iron supply in prediction or forecasting, the variability of light-limited productivity must be resolved.

  12. Sea-level and ocean-current control on carbonate-platform growth, Maldives, Indian Ocean

    NARCIS (Netherlands)

    Betzler, C.; Fürstenau, J.; Lüdmann, T.; Hübscher, C.; Lindhorst, S.; Paul, A.; Reijmer, J.J.G.; Droxler, A.W.

    2013-01-01

    Multichannel high-resolution seismic and multibeam data were acquired from the Maldives-isolated carbonate platform in the Indian Ocean for a detailed characterization of the Neogene bank architecture of this edifice. The goal of the research is to decipher the controlling factors of platform

  13. Macro- and megabenthic assemblages in the bathyal and abyssal Weddell Sea (Southern Ocean)

    Science.gov (United States)

    Linse, Katrin; Brandt, Angelika; Bohn, Jens M.; Danis, Bruno; De Broyer, Claude; Ebbe, Brigitte; Heterier, Vincent; Janussen, Dorte; López González, Pablo J.; Schüller, Myriam; Schwabe, Enrico; Thomson, Michael R. A.

    2007-08-01

    The assemblages inhabiting the continental shelf around Antarctica are known to be very patchy, in large part due to deep iceberg impacts. The present study shows that richness and abundance of much deeper benthos, at slope and abyssal depths, also vary greatly in the Southern and South Atlantic oceans. On the ANDEEP III expedition, we deployed 16 Agassiz trawls to sample the zoobenthos at depths from 1055 to 4930 m across the northern Weddell Sea and two South Atlantic basins. A total of 5933 specimens, belonging to 44 higher taxonomic groups, were collected. Overall the most frequent taxa were Ophiuroidea, Bivalvia, Polychaeta and Asteroidea, and the most abundant taxa were Malacostraca, Polychaeta and Bivalvia. Species richness per station varied from 6 to 148. The taxonomic composition of assemblages, based on relative taxon richness, varied considerably between sites but showed no relation to depth. The former three most abundant taxa accounted for 10-30% each of all taxa present. Standardised abundances based on trawl catches varied between 1 and 252 individuals per 1000 m 2. Abundance significantly decreased with increasing depth, and assemblages showed high patchiness in their distribution. Cluster analysis based on relative abundance showed changes of community structure that were not linked to depth, area, sediment grain size or temperature. Generally abundances of zoobenthos in the abyssal Weddell Sea are lower than shelf abundances by several orders of magnitude.

  14. Environmental drivers of coccolithophore abundance and calcification across Drake Passage (Southern Ocean)

    Science.gov (United States)

    Charalampopoulou, Anastasia; Poulton, Alex J.; Bakker, Dorothee C. E.; Lucas, Mike I.; Stinchcombe, Mark C.; Tyrrell, Toby

    2016-11-01

    Although coccolithophores are not as numerically common or as diverse in the Southern Ocean as they are in subpolar waters of the North Atlantic, a few species, such as Emiliania huxleyi, are found during the summer months. Little is actually known about the calcite production (CP) of these communities or how their distribution and physiology relate to environmental variables in this region. In February 2009, we made observations across Drake Passage (between South America and the Antarctic Peninsula) of coccolithophore distribution, CP, primary production, chlorophyll a and macronutrient concentrations, irradiance and carbonate chemistry. Although CP represented less than 1 % of total carbon fixation, coccolithophores were widespread across Drake Passage. The B/C morphotype of E. huxleyi was the dominant coccolithophore, with low estimates of coccolith calcite (˜ 0.01 pmol C coccolith-1) from biometric measurements. Both cell-normalised calcification (0.01-0.16 pmol C cell-1 d-1) and total CP (Drake Passage. Broadly, our results lend support to recent suggestions that coccolithophores, especially E. huxleyi, are advancing polewards. However, our in situ observations indicate that this may owe more to sea-surface warming and increasing irradiance rather than increasing CO2 concentrations.

  15. Salp distribution and size composition in the Atlantic sector of the Southern Ocean

    Science.gov (United States)

    Kawaguchi, S.; Siegel, V.; Litvinov, F.; Loeb, V.; Watkins, J.

    2004-06-01

    Salp abundance and length frequency were measured during the large-scale CCAMLR 2000 Survey conducted in the Atlantic Sector of the Southern Ocean in the 1999/2000 season. Results from regional surveys around Elephant Island in 1994/95 and 1996/97 seasons also were examined. During the CCAMLR 2000 Survey, salp abundance was higher in the Antarctic Peninsula and South Sandwich Island areas than in the central Scotia Sea. The probable reason for this pattern is a negative relationship with phytoplankton abundance; the central Scotia Sea having greater phytoplankton concentrations than required for optimal salp filter-feeding performance. Cluster analysis of salp size composition resulted in three cluster groups for each of the three surveys. Clusters comprising large salps occurred in warmer waters in all three surveys. The size composition of the salp populations suggests that the timing of intense asexual reproductive budding was earlier in warmer waters. As surface water temperatures generally decrease from north to south, and increase from spring to summer, the general spatio-temporal pattern of asexual reproduction by budding is likely to proceed from north to south as the summer season progresses.

  16. Microzooplankton community associated with phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean).

    Science.gov (United States)

    Christaki, Urania; Georges, Clément; Genitsaris, Savvas; Monchy, Sébastien

    2015-07-01

    The spatial and temporal community composition of microzooplankton (dinoflagellates and ciliates) was assessed in the Kerguelen area (Southern Ocean) during the KEOPS2 cruise in early spring (October-November) 2011. This naturally iron-fertilized region was characterized by a complex mesoscale circulation resulting in a patchy distribution of phytoplankton blooms. Collectively, 97 morphospecies of dinoflagellates and ciliates belonging to 41 genera were identified by microscopy, and 202 Alveolata-related OTUs (operational taxonomical units) were retrieved with tag-pyrosequencing. Microscopy and pyrosequencing data were in accordance, in that diatom-consuming dinoflagellates were the most enhanced taxa in the blooms. Dinoflagellates also showed significant positive relationships with phytoplankton pigments, while no major differences were found in the ciliate abundances inside and outside the blooms. Cluster analysis showed clear differences in the phytoplankton and microzooplankton community structures between the iron-fertilized and HNLC (high nutrient low chlorophyll) waters, and between the blooms, concerning their location and the fertilization mechanisms. These results were combined with the rates of primary production and mesozooplankton consumption determined for the study area. The potential role of dinoflagellates and ciliates as phytoplankton consumers and as prey for mesozooplankton was then evaluated. Overall, heterotrophic dinoflagellates were probably the most important group of phytoplankton grazers, and a potential food source for copepods. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  17. Blue and fin whale call source levels and propagation range in the Southern Ocean.

    Science.gov (United States)

    Sirović, Ana; Hildebrand, John A; Wiggins, Sean M

    2007-08-01

    Blue (Balaenoptera musculus) and fin whales (B. physalus) produce high-intensity, low-frequency calls, which probably function for communication during mating and feeding. The source levels of blue and fin whale calls off the Western Antarctic Peninsula were calculated using recordings made with calibrated, bottom-moored hydrophones. Blue whales were located up to a range of 200 km using hyperbolic localization and time difference of arrival. The distance to fin whales, estimated using multipath arrivals of their calls, was up to 56 km. The error in range measurements was 3.8 km using hyperbolic localization, and 3.4 km using multipath arrivals. Both species produced high-intensity calls; the average blue whale call source level was 189+/-3 dB re:1 microPa-1 m over 25-29 Hz, and the average fin whale call source level was 189+/-4 dB re:1 microPa-1 m over 15-28 Hz. Blue and fin whale populations in the Southern Ocean have remained at low numbers for decades since they became protected; using source level and detection range from passive acoustic recordings can help in calculating the relative density of calling whales.

  18. Biological physical interactions and pelagic productivity at the Prince Edward Islands, Southern Ocean

    Science.gov (United States)

    Perissinotto, R.; Lutjeharms, J. R. E.; van Ballegooyen, R. C.

    2000-03-01

    The Prince Edward Islands lie in the subantarctic zone of the Southern Ocean, just north of the Antarctic Polar Front (APF). Recent investigations have shown enhanced primary productivity in its immediate environment due to an island effect. An extensive cruise, covering ≈10 5 km 2 around the island group was carried out to study this supposed island effect in a wider setting. We report here on the biological productivity relative to the physico-chemical environment during the period 7-19 April 1989. Overall, the chlorophyll- a (chl- a) values as well as primary productivity were substantially lower on this occasion than those observed previously. The distribution of terrigenous urea and ammonia clearly demarcated the geographical limits of the immediate island effect, which did not extend further than 80 km off-shore. The hydrography exhibited strong flow past the islands and a distinct wake downstream of the archipelago. Vortices associated with this wake showed some degree of spatial covariance with the distribution of chl- a. No region of enhanced primary productivity was observed between the islands, a conspicuous feature observed during previous cruises to the area.

  19. Polychlorinated biphenyls in freshwater salmonids from the Kerguelen Islands in the Southern Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Jaffal, A. [Laboratoire d' Eco-Toxicologie, EA 2069 Vignes et Vins de Champagne, Universite de Reims Champagne-Ardenne, F51687 Reims Cedex 2 (France); Givaudan, N. [UMR8079, CNRS, Orsay F-91405 (France); Univ Paris-Sud, Ecologie Systematique et Evolution, Orsay F-91405 (France); Betoulle, S. [Laboratoire d' Eco-Toxicologie, EA 2069 Vignes et Vins de Champagne, Universite de Reims Champagne-Ardenne, F51687 Reims Cedex 2 (France); Terreau, A. [IPEV Institut Polaire Francais, F29280 Plouzane (France); Paris-Palacios, S.; Biagianti-Risbourg, S. [Laboratoire d' Eco-Toxicologie, EA 2069 Vignes et Vins de Champagne, Universite de Reims Champagne-Ardenne, F51687 Reims Cedex 2 (France); Beall, E. [ECOBIOP, UMR 1224 INRA-Universite de Pau-Pays de l' Adour F63310 St-Pee-sur-Nivelle (France); Roche, H., E-mail: helene.roche@u-psud.fr [UMR8079, CNRS, Orsay F-91405 (France); Univ Paris-Sud, Ecologie Systematique et Evolution, Orsay F-91405 (France)

    2011-05-15

    The Subantarctic Kerguelen Islands (49{sup o}S, 70{sup o}E) contain freshwater ecosystems among the most isolated in the world. Concentrations of polychlorinated biphenyls (PCBs) were assessed in the muscle of 48 brook trout and 38 brown trout caught during summer and spring 2006 in the rivers, lakes and ponds of Kerguelen. The sum of 29 PCBs averaged 404 and 358 ng g{sup -1} lipid, and dioxin-like PCB was 19 and 69 ng g{sup -1} lipid, in brook and brown trout, respectively. The values showed a high variability and some fish accumulated PCBs at levels similar to those of fish from impacted areas. While inter-sex differences were limited, the season and the morphotype appeared to have the most influence. Fish captured in summer had muscle PCB concentrations about three times higher than those caught in spring and the 'river' morphotype of brook trout showed the highest PCB levels. - Highlights: > First assessment of PCB contamination of biota in Kerguelen Islands, Sub-Antarctica. > PCB bioaccumulation level in trout varies from very high to undetectable. > Habitat and morphotype are the most influential factors on the variability. > Distribution pattern of PCBs in the muscle of fish is morphotype dependent. - Salmonids in hydrosystems of the Kerguelen Islands (Southern Ocean) show a high PCB bioaccumulation.

  20. The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound

    Science.gov (United States)

    Menze, Sebastian; Zitterbart, Daniel P.; van Opzeeland, Ilse; Boebel, Olaf

    2017-01-01

    This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (Balaenoptera physalus), Antarctic minke whales (Balaenoptera bonaerensis) and leopard seals (Hydrurga leptonyx). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton.

  1. Antarctic krill swarm characteristics in the Southeast Atlantic sector of the Southern Ocean

    KAUST Repository

    Krafft, BA

    2012-09-28

    Knowledge about swarm dynamics and underlying causes is essential to understand the ecology and distribution of Antarctic krill Euphausia superba. We collected acoustic data and key environmental data continuously across extensive gradients in the little-studied Southeast Atlantic sector of the Southern Ocean. A total of 4791 krill swarms with swarm descriptors including swarm height and length, packing density, swimming depth and inter-swarm distance were extracted. Through multivariate statistics, swarms were categorized into 4 groups. Group 2 swarms were largest (median length 108 m and thickness 18 m), whereas swarms in both Groups 1 and 4 were on average small, but differed markedly in depth distribution (median: 52 m for Group 1 vs. 133 m for Group 4). There was a strong spatial autocorrelation in the occurrence of swarms, and an autologistic regression model found no prediction of swarm occurrence from environmental variables for any of the Groups 1, 2 or 4. Probability of occurrence of Group 3 swarms, however, increased with increasing depth and temperature. Group 3 was the most distinctive swarm group with an order of magnitude higher packing density (median: 226 ind. m−3) than swarms from any of the other groups and about twice the distance to nearest neighbor swarm (median: 493 m). The majority of the krill were present in Group 3 swarms, and the absence of association with hydrographic or topographic concentrating mechanisms strongly suggests that these swarms aggregate through their own locomotion, possibly associated with migration.

  2. Assessment of marine weather forecasts over the Indian sector of Southern Ocean

    Science.gov (United States)

    Gera, Anitha; Mahapatra, D. K.; Sharma, Kuldeep; Prakash, Satya; Mitra, A. K.; Iyengar, G. R.; Rajagopal, E. N.; Anilkumar, N.

    2017-09-01

    The Southern Ocean (SO) is one of the important regions where significant processes and feedbacks of the Earth's climate take place. Expeditions to the SO provide useful data for improving global weather/climate simulations and understanding many processes. Some of the uncertainties in these weather/climate models arise during the first few days of simulation/forecast and do not grow much further. NCMRWF issued real-time five day weather forecasts of mean sea level pressure, surface winds, winds at 500 hPa & 850 hPa and rainfall, daily to NCAOR to provide guidance for their expedition to Indian sector of SO during the austral summer of 2014-2015. Evaluation of the skill of these forecasts indicates possible error growth in the atmospheric model at shorter time scales. The error growth is assessed using the model analysis/reanalysis, satellite data and observations made during the expedition. The observed variability of sub-seasonal rainfall associated with mid-latitude systems is seen to exhibit eastward propagations and are well reproduced in the model forecasts. All cyclonic disturbances including the sub-polar lows and tropical cyclones that occurred during this period were well captured in the model forecasts. Overall, this model performs reasonably well over the Indian sector of the SO in medium range time scale.

  3. The Discovery of New Deep-Sea Hydrothermal Vent Communities in the Southern Ocean and Implications for Biogeography

    OpenAIRE

    Chown, Steven L

    2012-01-01

    The diversity of many marine benthic groups is unlike that of most other taxa. Rather than declining from the tropics to the poles, much of the benthos shows high diversity in the Southern Ocean. Moreover, many species are unique to the Antarctic region. Recent work has shown that this is also true of the communities of Antarctic deep-sea hydrothermal vents. Vent ecosystems have been documented from many sites across the globe, associated with the thermally and chemically variable habitats fo...

  4. CHANGES IN THE C, N AND P CYCLES BY THE PREDICTED SALPS-KRILL SHIFT IN THE SOUTHERN OCEAN.

    Directory of Open Access Journals (Sweden)

    Miquel eAlcaraz

    2014-09-01

    Full Text Available The metabolic carbon requirements and excretion rates of three major zooplankton groups in the Southern Ocean were studied in February 2009. The research was conducted in the framework of the ATOS research project as part of the Spanish contribution to the International Polar Year. The objective was to ascertain the possible consequences of the predicted zooplankton shift from krill to salps in the Southern Ocean for the cycling of biogenic carbon and the concentration and stoichiometry of dissolved inorganic nutrients. The carbon respiratory demands and NH4-N and PO4-P excretion rates of < 5 mm size copepods, krill and salps were estimated by incubation experiments. The carbon-specific metabolic rates and N:P metabolic quotients of salps were higher than those of krill (furcilia spp. and adults and copepods, and as expected there was a significant negative relation between average individual zooplankton biomass and their metabolic rates, each metabolic process showing a particular response that lead to different metabolic N:P ratios. The predicted change from krill to salps in the Southern Ocean would encompass not only the substitution of a pivotal group for Antarctic food webs (krill by one with an indifferent trophic role (salps. In a zooplankton community dominated by salps the respiratory carbon demand by zooplankton will significantly increase, and therefore the proportion of primary production that should be allocated to compensate for the global respiratory C-losses of zooplankton. At the same time, the higher production by salps of larger, faster sinking fecal pellets will increase the sequestration rate of biogenic carbon. Similarly, the higher N and P excretion rates of zooplankton and the changes in the N:P stoichiometry of the metabolic products will modify the concentration and proportion of N and P in the nutrient pool, inducing quantitative and qualitative changes on primary producers that will translate to the whole Southern

  5. Instantaneous Linkages between Clouds and Large-Scale Meteorology over the Southern Ocean in Observations and a Climate Model

    Energy Technology Data Exchange (ETDEWEB)

    Wall, Casey J. [Department of Atmospheric Sciences, University of Washington, Seattle, Washington; Hartmann, Dennis L. [Department of Atmospheric Sciences, University of Washington, Seattle, Washington; Ma, Po-Lun [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington

    2017-12-01

    Instantaneous, coincident, footprint-level satellite observations of cloud properties and radiation taken during austral summer over the Southern Ocean are used to study relationships between clouds and large-scale meteorology. Cloud properties are very sensitive to the strength of vertical motion in the middle-troposphere, and low-cloud properties are sensitive to estimated inversion strength, low-level temperature advection, and sea surface temperature. These relationships are quantified. An index for the meteorological anomalies associated with midlatitude cyclones is presented, and it is used to reveal the sensitivity of clouds to the meteorology within the warm- and cold-sector of cyclones. The observed relationships between clouds and meteorology are compared to those in the Community Atmosphere Model version 5 (CAM5) using satellite simulators. Low-clouds simulated by CAM5 are too few, too bright, and contain too much ice, and low-clouds located in the cold-sector of cyclones are too sensitive to variations in the meteorology. The latter two biases are dramatically reduced when CAM5 is coupled with an updated boundary layer parameterization know as Cloud Layers Unified by Binormals (CLUBB). More generally, this study demonstrates that examining the instantaneous timescale is a powerful approach to understanding the physical processes that control clouds and how they are represented in climate models. Such an evaluation goes beyond the cloud climatology and exposes model bias under various meteorological conditions.

  6. Applications of very high-resolution imagery in the study and conservation of large predators in the Southern Ocean.

    Science.gov (United States)

    Larue, Michelle A; Knight, Joseph

    2014-12-01

    The Southern Ocean is one of the most rapidly changing ecosystems on the planet due to the effects of climate change and commercial fishing for ecologically important krill and fish. Because sea ice loss is expected to be accompanied by declines in krill and fish predators, decoupling the effects of climate and anthropogenic changes on these predator populations is crucial for ecosystem-based management of the Southern Ocean. We reviewed research published from 2007 to 2014 that incorporated very high-resolution satellite imagery to assess distribution, abundance, and effects of climate and other anthropogenic changes on populations of predators in polar regions. Very high-resolution imagery has been used to study 7 species of polar animals in 13 papers, many of which provide methods through which further research can be conducted. Use of very high-resolution imagery in the Southern Ocean can provide a broader understanding of climate and anthropogenic forces on populations and inform management and conservation recommendations. We recommend that conservation biologists continue to integrate high-resolution remote sensing into broad-scale biodiversity and population studies in remote areas, where it can provide much needed detail. © 2014 Society for Conservation Biology.

  7. Chlorophyll-a Variability in the Southern Ocean Mixed Layer and Euphotic Zone From Elephant Seals and Profiling Floats

    Science.gov (United States)

    Carranza, M. M.; Gille, S. T.; Franks, P. J. S.; Johnson, K. S.; Girton, J. B.

    2015-12-01

    The Southern Ocean contains some of the ocean's deepest mixed layers. Because deep mixed layers can transport phytoplankton below the euphotic zone, light levels depend on mixed-layer depth (MLD), and phytoplankton growth is hypothesized to be co-limited by iron and light. Estimates of Chl-a fluorescence, particle backscattering and hydrographic profiles collected by southern elephant seals, EM-APEX, and biogeochemical Argo floats are used to evaluate the extent to which MLD influences phytoplankton bloom development and the vertical structure of chlorophyll-a (Chl-a) in the Southern Ocean. We find that surface Chl-a (i.e., mean Chl-a for the upper light penetration depth) is a relatively good proxy of phytoplankton biomass (i.e., depth-integrated Chl-a) within the euphotic zone but gives an inadequate representation of biomass within the mixed layer, particularly in the summer. Although nearly vertically homogeneous Chl-a within the mixed layer prevails in seasonal mean profiles, subsurface Chl-a maxima are not uncommon from spring through fall. Deep Chl-a maxima that correlate with particle backscattering in summer and fall are found near the base of the mixed layer, closer to the nutrient maximum than the light maximum, suggesting that nutrient limitation (i.e., essentially iron) can play a greater role than light limitation in governing productivity.

  8. Biogeography in Cellana (Patellogastropoda, Nacellidae) with Special Emphasis on the Relationships of Southern Hemisphere Oceanic Island Species.

    Science.gov (United States)

    González-Wevar, Claudio A; Nakano, Tomoyuki; Palma, Alvaro; Poulin, Elie

    2017-01-01

    Oceanic islands lacking connections to other land are extremely isolated from sources of potential colonists and have acquired their biota mainly through dispersal from geographically distant areas. Hence, isolated island biota constitutes interesting models to infer biogeographical mechanisms of dispersal, colonization, differentiation, and speciation. Limpets of the genus Cellana (Nacellidae: Patellogastropoda) show limited dispersal capacity but are broadly distributed across the Indo-Pacific including many endemic species in isolated oceanic islands. Here, we examined main distributional patterns and geographic boundaries among Cellana lineages with special emphasis in the relationships of Southern Hemisphere oceanic islands species. Phylogenetic reconstructions based on mtDNA (COI) recognized three main clades in Cellana including taxa from different provinces of the Indo-Pacific. Clear genetic discontinuities characterize the biogeography of Cellana and several lineages are associated to particular areas of the Indo-Pacific supporting the low dispersal capacity of the genus across recognized biogeographical barriers in the region. However, evolutionary relationships within Cellana suggest that long-distance dispersal processes have been common in the history of the genus and probably associated to the origin of the species in Hawaii and Juan Fernández Archipelago. Therefore, the presence of Cellana species in geographically distant Southern Hemisphere oceanic islands, such as the Juan Fernández Archipelago, suggests that long-distance dispersal mediated by rafting may have played an important role in the biogeography of the genus.

  9. Biogeography in Cellana (Patellogastropoda, Nacellidae) with Special Emphasis on the Relationships of Southern Hemisphere Oceanic Island Species

    Science.gov (United States)

    Nakano, Tomoyuki; Palma, Alvaro; Poulin, Elie

    2017-01-01

    Oceanic islands lacking connections to other land are extremely isolated from sources of potential colonists and have acquired their biota mainly through dispersal from geographically distant areas. Hence, isolated island biota constitutes interesting models to infer biogeographical mechanisms of dispersal, colonization, differentiation, and speciation. Limpets of the genus Cellana (Nacellidae: Patellogastropoda) show limited dispersal capacity but are broadly distributed across the Indo-Pacific including many endemic species in isolated oceanic islands. Here, we examined main distributional patterns and geographic boundaries among Cellana lineages with special emphasis in the relationships of Southern Hemisphere oceanic islands species. Phylogenetic reconstructions based on mtDNA (COI) recognized three main clades in Cellana including taxa from different provinces of the Indo-Pacific. Clear genetic discontinuities characterize the biogeography of Cellana and several lineages are associated to particular areas of the Indo-Pacific supporting the low dispersal capacity of the genus across recognized biogeographical barriers in the region. However, evolutionary relationships within Cellana suggest that long-distance dispersal processes have been common in the history of the genus and probably associated to the origin of the species in Hawaii and Juan Fernández Archipelago. Therefore, the presence of Cellana species in geographically distant Southern Hemisphere oceanic islands, such as the Juan Fernández Archipelago, suggests that long-distance dispersal mediated by rafting may have played an important role in the biogeography of the genus. PMID:28099466

  10. Biogeography in Cellana (Patellogastropoda, Nacellidae with Special Emphasis on the Relationships of Southern Hemisphere Oceanic Island Species.

    Directory of Open Access Journals (Sweden)

    Claudio A González-Wevar

    Full Text Available Oceanic islands lacking connections to other land are extremely isolated from sources of potential colonists and have acquired their biota mainly through dispersal from geographically distant areas. Hence, isolated island biota constitutes interesting models to infer biogeographical mechanisms of dispersal, colonization, differentiation, and speciation. Limpets of the genus Cellana (Nacellidae: Patellogastropoda show limited dispersal capacity but are broadly distributed across the Indo-Pacific including many endemic species in isolated oceanic islands. Here, we examined main distributional patterns and geographic boundaries among Cellana lineages with special emphasis in the relationships of Southern Hemisphere oceanic islands species. Phylogenetic reconstructions based on mtDNA (COI recognized three main clades in Cellana including taxa from different provinces of the Indo-Pacific. Clear genetic discontinuities characterize the biogeography of Cellana and several lineages are associated to particular areas of the Indo-Pacific supporting the low dispersal capacity of the genus across recognized biogeographical barriers in the region. However, evolutionary relationships within Cellana suggest that long-distance dispersal processes have been common in the history of the genus and probably associated to the origin of the species in Hawaii and Juan Fernández Archipelago. Therefore, the presence of Cellana species in geographically distant Southern Hemisphere oceanic islands, such as the Juan Fernández Archipelago, suggests that long-distance dispersal mediated by rafting may have played an important role in the biogeography of the genus.

  11. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Barometric pressure sensor, Carbon dioxide (CO2) gas analyzer and other instruments from ROGER REVELLE in the South Pacific Ocean and Southern Oceans from 2005-01-06 to 2005-02-19 (NCEI Accession 0144243)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144243 includes Surface underway data collected from ROGER REVELLE in the South Pacific Ocean and Southern Oceans (> 60 degrees South) from...

  12. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans from 2003-01-03 to 2003-03-17 (NCEI Accession 0143930)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143930 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  13. Dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 1998-03-28 to 1998-05-23 (NODC Accession 0113595)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0113595 includes discrete sample and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (> 60 degrees South)...

  14. Dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 2005-01-22 to 2005-04-06 (NODC Accession 0108100)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108100 includes discrete sample and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (> 60 degrees South)...

  15. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from ROGER REVELLE in the Indian Ocean and Southern Oceans from 2007-02-04 to 2007-03-17 (NODC Accession 0108119)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108119 includes discrete sample and profile data collected from ROGER REVELLE in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  16. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from ROGER REVELLE in the South Pacific Ocean and Southern Oceans from 2005-01-09 to 2005-02-19 (NODC Accession 0108095)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108095 includes discrete sample and profile data collected from ROGER REVELLE in the South Pacific Ocean and Southern Oceans (> 60 degrees South)...

  17. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from unknown platforms in the South Pacific Ocean and Southern Oceans from 2010-12-28 to 2014-02-21 (NCEI Accession 0160574)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0160574 includes chemical, discrete sample, physical and profile data collected from unknown platforms in the South Pacific Ocean and Southern Oceans...

  18. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, PAR Sensor and other instruments from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans from 2012-01-05 to 2012-02-12 (NCEI Accession 0143949)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0143949 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  19. Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from NOAA Ship DISCOVERER in the South Pacific Ocean, Southern Oceans and Tasman Sea from 1996-01-05 to 1996-03-10 (NODC Accession 0115155)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0115155 includes chemical, discrete sample, physical and profile data collected from NOAA Ship DISCOVERER in the South Pacific Ocean, Southern Oceans...

  20. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 1990-11-17 to 1990-12-30 (NODC Accession 0117676)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0117676 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (>...

  1. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 2006-08-25 to 2006-10-29 (NODC Accession 0108157)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108157 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (>...

  2. Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, PAR Sensor and other instruments from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans from 2016-01-11 to 2016-03-15 (NCEI Accession 0163181)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0163181 includes chemical, discrete sample, optical, physical and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans...

  3. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from RRS JAMES COOK in the South Atlantic Ocean and Southern Oceans from 2010-03-19 to 2010-04-24 (NODC Accession 0108069)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108069 includes discrete sample and profile data collected from RRS JAMES COOK in the South Atlantic Ocean and Southern Oceans (> 60 degrees...

  4. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans from 1995-07-17 to 1995-09-02 (NCEI Accession 0144339)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144339 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  5. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from MARION DUFRESNE in the Indian Ocean and Southern Oceans from 1996-02-20 to 1996-03-31 (NODC Accession 0115012)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0115012 includes discrete sample and profile data collected from MARION DUFRESNE in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  6. Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, Coulometer for DIC measurement and other instruments from LAURENCE M. GOULD in the South Atlantic Ocean and Southern Oceans from 2009-09-16 to 2009-10-09 (NODC Accession 0112845)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0112845 includes discrete sample and profile data collected from LAURENCE M. GOULD in the South Atlantic Ocean and Southern Oceans (> 60 degrees...

  7. Temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from LAURENCE M. GOULD in the Gulf of Guinea, South Atlantic Ocean and Southern Oceans from 2006-03-23 to 2010-11-02 (NCEI Accession 0144979)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144979 includes discrete sample and profile data collected from LAURENCE M. GOULD in the Gulf of Guinea, South Atlantic Ocean and Southern Oceans...

  8. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 2007-11-28 to 2008-02-04 (NODC Accession 0108067)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108067 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (>...

  9. Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 1986-06-27 to 1986-12-14 (NODC Accession 0116642)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0116642 includes chemical, discrete sample, physical and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (>...

  10. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans from 2004-12-23 to 2005-02-17 (NODC Accession 0108076)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108076 includes discrete sample and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  11. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from POLARSTERN in the South Atlantic Ocean and Southern Oceans from 2008-02-10 to 2008-04-16 (NODC Accession 0108154)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108154 includes discrete sample and profile data collected from POLARSTERN in the South Atlantic Ocean and Southern Oceans (> 60 degrees South)...

  12. Partial pressure (or fugacity) of carbon dioxide, dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, Barometric pressure sensor and other instruments from ROGER REVELLE in the Indian Ocean and Southern Oceans from 2008-02-04 to 2008-03-17 (NODC Accession 0108118)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108118 includes discrete sample and profile data collected from ROGER REVELLE in the Indian Ocean and Southern Oceans (> 60 degrees South) from...

  13. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans from 2006-01-02 to 2006-03-12 (NODC Accession 0109922)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0109922 includes chemical, discrete sample, optical, physical and profile data collected from AURORA AUSTRALIS in the Indian Ocean and Southern Oceans...

  14. Southern Hemisphere anticyclonic circulation drives oceanic and climatic conditions in late Holocene southernmost Africa

    Directory of Open Access Journals (Sweden)

    A. Hahn

    2017-06-01

    Full Text Available Due to the high sensitivity of southern Africa to climate change, a reliable understanding of its hydrological system is crucial. Recent studies of the regional climatic system have revealed a highly complex interplay of forcing factors on precipitation regimes. This includes the influence of the tropical easterlies, the strength of the southern hemispheric westerlies as well as sea surface temperatures along the coast of the subcontinent. However, very few marine records have been available in order to study the coupling of marine and atmospheric circulation systems. Here we present results from a marine sediment core, recovered in shallow waters off the Gouritz River mouth on the south coast of South Africa. Core GeoB18308-1 allows a closer view of the last  ∼  4 kyr. Climate sensitive organic proxies, like the distribution and isotopic composition of plant-wax lipids as well as indicators for sea surface temperatures and soil input, give information on oceanographic and hydrologic changes during the recorded time period. Moreover, the micropaleontology, mineralogical and elemental composition of the sediments reflect the variability of the terrigenous input to the core site. The combination of down-core sediment signatures and a catchment-wide provenance study indicate that the Little Ice Age ( ∼  300–650 cal yr BP was characterized by climatic conditions favorable to torrential flood events. The Medieval Climate Anomaly ( ∼  950–650 cal yr BP is expressed by lower sea surface temperatures in the Mossel Bay area and humid conditions in the Gouritz River catchment. These new results suggest that the coincidence of humid conditions and cooler sea surface temperatures along the south coast of South Africa resulted from a strengthened and more southerly anticyclonic circulation. Most probably, the transport of moisture from the Indian Ocean by strong subtropical easterlies was coupled with Agulhas Bank

  15. An iron budget during the natural iron fertilisation experiment KEOPS (Kerguelen Islands, Southern Ocean

    Directory of Open Access Journals (Sweden)

    F. Chever

    2010-02-01

    Full Text Available Total dissolvable iron (TDFe was measured in the water column above and in the surrounding of the Kerguelen Plateau (Indian sector of the Southern Ocean during the KErguelen Ocean Plateau compared Study (KEOPS cruise. TDFe concentrations ranged from 0.90 to 65.6 nmol L−1 above the plateau and from 0.34 to 2.23 nmol L−1 offshore of the plateau. Station C1 located south of the plateau, near Heard Island, exhibited very high values (329–770 nmol L−1. Apparent particulate iron (Feapp, calculated as the difference between the TDFe and the dissolved iron measured on board (DFe represented 95±5% of the TDFe above the plateau, suggesting that particles and refractory colloids largely dominated the iron pool. This paper presents a budget of DFe and Feapp above the plateau. Lateral advection of water that had been in contact with the continental shelf of Heard Island seems to be the predominant source of Feapp and DFe above the plateau, with a supply of 9.7±3.6×106 and 8.3±11.6×103 mol d−1, respectively. The residence times of 1.7 and 48 days estimated for Feapp and DFe respectively, indicate a rapid turnover in the surface water. A comparison between Feapp and total particulate iron (TPFe suggests that the total dissolved fraction is mainly constituted of small refractory colloids. This fraction does not seem to be a potential source of iron to the phytoplankton in our study. Finally, when taking into account the lateral supply of dissolved iron, the seasonal carbon sequestration efficiency was estimated at 154 000 mol C (mol Fe−1, which is 4-fold lower than the previously estimated value in this area but still 18-fold higher than the one estimated during the other study of a natural iron fertilisation experiment, CROZEX.

  16. A uniform, quality controlled Surface Ocean CO2 Atlas (SOCAT

    Directory of Open Access Journals (Sweden)

    B. Pfeil

    2013-04-01

    Full Text Available A well-documented, publicly available, global data set of surface ocean carbon dioxide (CO2 parameters has been called for by international groups for nearly two decades. The Surface Ocean CO2 Atlas (SOCAT project was initiated by the international marine carbon science community in 2007 with the aim of providing a comprehensive, publicly available, regularly updated, global data set of marine surface CO2, which had been subject to quality control (QC. Many additional CO2 data, not yet made public via the Carbon Dioxide Information Analysis Center (CDIAC, were retrieved from data originators, public websites and other data centres. All data were put in a uniform format following a strict protocol. Quality control was carried out according to clearly defined criteria. Regional specialists performed the quality control, using state-of-the-art web-based tools, specially developed for accomplishing this global team effort. SOCAT version 1.5 was made public in September 2011 and holds 6.3 million quality controlled surface CO2 data points from the global oceans and coastal seas, spanning four decades (1968–2007. Three types of data products are available: individual cruise files, a merged complete data set and gridded products. With the rapid expansion of marine CO2 data collection and the importance of quantifying net global oceanic CO2 uptake and its changes, sustained data synthesis and data access are priorities.

  17. A laboratory analogue of current-topography interaction in the Southern Ocean.

    Science.gov (United States)

    Ajayi, Adekunle; Sommeria, Joel; Raja, Keshav; Staquet, Chantal; Viboud, Samuel; Voisin, Bruno

    2017-04-01

    The Antarctic Circumpolar Current (ACC) is an active site of turbulent mixing in the circulation of Southern Ocean (SO). This is attributed to the instabilities of waves and eddies resulting from the interaction of geostrophic flow with bottom topography. For the first time, the dynamics of the Antarctic Circumpolar Current is reproduced in the laboratory using the rotating Coriolis platform with diameter 13m. The tank is filled with a 1m thick layer of uniformly stratified salt water. A uniform circular current around the tank is produced by a small change of tank rotation speed which persists by inertia for the duration of the experiment, during which the flow conditions can be considered quasi-steady. Spherical cap(s) was introduce as bottom topography in the flow configuration. The experimental module was divided into two cases: with Coriolis effect and without Coriolis effect. Several experiments with multiple caps to mimic rough topography features were conducted with various values of Froude and Rossby number. Waves and eddies resulting from the interaction of the flow with the topography were studied. It was realised that rotation greatly enhances vertical transport of momentum from the bottom. Inertial oscillations were observed and likely contribute to this transport. Turbulence generation was observed close the topography but also in the fluid interior far above it, which presumably results from wave breaking. Consistently, analysis of the density probes showed vertical mixing in the water column both at the bottom and in the interior. The link with the theoretical modelling by Nikurashin & Ferrari (2010) and Labreuche et al. (2016) will be discussed.

  18. Diversity of Southern Ocean deep-sea Isopoda (Crustacea, Malacostraca) — a comparison with shelf data

    Science.gov (United States)

    Brandt, Angelika; Brökeland, Wiebke; Brix, Saskia; Malyutina, Marina

    2004-07-01

    Samples were taken during the expeditions ANDEEP I & II (ANT XIX/3-4) (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) with RV Polarstern for the analysis of the Southern Ocean (SO) deep-sea isopod biodiversity in the Drake Passage, off Elephant Island, along the South Shetland Islands, in the northwestern Weddell Sea, and at the South Sandwich Islands. In total 5525 specimens of Isopoda were sampled and 317 species were discriminated. Isopoda were the most abundant peracarid taxon, with 38% of all Peracarida, 98% of the Isopoda belonging to the suborder Asellota. Species richness was highest in the northwestern Weddell Sea; diversity and evenness were relatively high at all stations. The Munnopsididae were the most dominant isopod family, with 61% of the specimens, 118 species divided among 28 genera; the Haploniscidae comprised 15% of all isopods with 36 species from four genera, followed by the Ischnomesidae with 7% and 30 species from five genera. The families Desmosomatidae, Macrostylidae and Nannoniscidae comprised 10% of the isopod specimens. The Desmosomatidae were the second most diverse family, with 48 species from 12 genera. Species of the suborder Valvifera or the family Serolidae were much rarer in the SO deep-sea than on the shelf. 141 of isopod species (46% of the total number) were rare, occurring only at one of the 21 epibenthic-sledge stations. A cluster analysis showed no clear relation between isopod communities and geographic area. Depth was the most important factor for differences in isopod community patterns. The species accumulation curve shows that the SO deep sea was not sampled representatively during ANDEEP I & II and further sampling is necessary. The SO deep-sea differs in faunal composition from the shelf.

  19. On the quality of hydrographic data collected in the Southern Ocean by instrumented elephant seals

    Science.gov (United States)

    Roquet, F.; Charrassin, J.-B.; Park, Y.-H.; Fedak, M.; Biuw, M.; Boehme, L.; Guinet, C.

    2009-04-01

    To study the foraging ecology of elephant seals in relation to oceanographic conditions, Satellite-Relayed Data Loggers (SRDL) with an integrated Conductivity-Temperature-Depth (CTD) have been developped by the Sea Mammal Research Unit (University of St Andrews), which autonomously collect and transmit hydrographic profiles (temperature/salinity) in near-real time via Argos satellites. These devices have the potential to provide detailed oceanographic information in logistically difficult areas at comparatively low cost, being therefore highly interesting for the oceanographic community as well. Large efforts for calibrating and validating the huge amount of collected hydrographic data have been constantly made since the first deployments in 2004, as a necessary step to produce data useful for oceanography. When possible, at-sea experiments were performed on ships of opportunity before deployments on seals, consisting in comparing hydrographic profiles from SRDLs with reference profiles obtained simultaneously with a standard CTD. These experiments brought to light a satisfying repeatability of SRDL sensors but also the presence of systematic biases, especially for salinity, which should be corrected. In 2007 and 2008, more than 6000 valid temperature/salinity (T/S) profiles were collected by 17 SRDLs around the Kerguelen Islands in the Southern Indian Ocean. We present several delayed-mode methods of estimation and reduction of systematic biases, applied to this peculiar seal dataset. These methods are based on comparisons of T/S profiles from SRDLs with available historical profiles (mainly CTD and ARGO profiles) or with each other (cross-comparisons). Based on this two-fold procedure, we show here the important technical and methodological improvements made since 2004 to produce hydrographic data suitable for oceanographic studies.

  20. The effects of natural iron fertilisation on deep-sea ecology: the Crozet Plateau, Southern Indian Ocean.

    Directory of Open Access Journals (Sweden)

    George A Wolff

    Full Text Available The addition of iron to high-nutrient low-chlorophyll (HNLC oceanic waters stimulates phytoplankton, leading to greater primary production. Large-scale artificial ocean iron fertilization (OIF has been proposed as a means of mitigating anthropogenic atmospheric CO(2, but its impacts on ocean ecosystems below the photic zone are unknown. Natural OIF, through the addition of iron leached from volcanic islands, has been shown to enhance primary productivity and carbon export and so can be used to study the effects of OIF on life in the ocean. We compared two closely-located deep-sea sites (∼400 km apart and both at ∼4200 m water depth to the East (naturally iron fertilized; +Fe and South (HNLC of the Crozet Islands in the southern Indian Ocean. Our results suggest that long-term geo-engineering of surface oceanic waters via artificial OIF would lead to significant changes in deep-sea ecosystems. We found that the +Fe area had greater supplies of organic matter inputs to the seafloor, including polyunsaturated fatty acid and carotenoid nutrients. The +Fe site also had greater densities and biomasses of large deep-sea animals with lower levels of evenness in community structuring. The species composition was also very different, with the +Fe site showing similarities to eutrophic sites in other ocean basins. Moreover, major differences occurred in the taxa at the +Fe and HNLC sites revealing the crucial role that surface oceanic conditions play in changing and structuring deep-sea benthic communities.

  1. A Southern Ocean variability study using the Argo-based Model for Investigation of the Global Ocean (AMIGO)

    Science.gov (United States)

    Lebedev, Konstantin

    2017-04-01

    The era of satellite observations of the ocean surface that started at the end of the 20th century and the development of the Argo project in the first years of the 21st century, designed to collect information of the upper 2000 m of the ocean using satellites, provides unique opportunities for continuous monitoring of the Global Ocean state. Starting from 2005, measurements with the Argo floats have been performed over the majority of the World Ocean. In November 2007, the Argo program reached coverage of 3000 simultaneously operating floats (one float in a three-degree square) planned during the development of the program. Currently, 4000 Argo floats autonomously profile the upper 2000-m water column of the ocean from Antarctica to Spitsbergen increasing World Ocean temperature and salinity databases by 12000 profiles per month. This makes it possible to solve problems on reconstructing and monitoring the ocean state on an almost real-time basis, study the ocean dynamics, obtain reasonable estimates of the climatic state of the ocean in the last decade and estimate existing intraclimatic trends. We present the newly developed Argo-Based Model for Investigation of the Global Ocean (AMIGO), which consists of a block for variational interpolation of the profiles of drifting Argo floats to a regular grid and a block for model hydrodynamic adjustment of variationally interpolated fields. Such a method makes it possible to obtain a full set of oceanographic characteristics - temperature, salinity, density, and current velocity - using irregularly located Argo measurements (the principle of the variational interpolation technique entails minimization of the misfit between the interpolated fields defined on the regular grid and irregularly distributed data; hence the optimal solution passes as close to the data as possible). The simulations were performed for the entire globe limited in the north by 85.5° N using 1° grid spacing in both longitude and latitude. At the

  2. Oceanic evolution of Spl-peridotites of the Frido Unit ophiolites (Southern Apennine-Italy)

    Science.gov (United States)

    Cristi Sansone, Maria T.; Prosser, Giacomo; Rizzo, Giovanna; Tartarotti, Paola

    2010-05-01

    The southern Apennine chain is a fold-and thrust belt formed between the upper Oligocene and Quaternary as a result of the convergence between the African and European plates and a simultaneous SE-directed rollback of the Ionian subducting lithospere. The ophiolitic sequences, which are part of the Southern Apennines, are remnants of the Ligurian oceanic lithosphere pertaining to the Jurassic western Tethys. The Liguride Units of the Southern Apennines include sequences characterized by an HP/LT metamorphic overprint in the Frido Unit and sequences lacking orogenic metamorphism North-Calabria Unit. The ophiolitic rocks occurring in the Frido Unit include serpentinite derived from a lherzolitic to harzburgitic mantle, as suggested by microstructural and petrographical features. The serpentinites are frequently associated to tectonic slices and dykes composed of diabase and medium to high-grade metamorphic rocks such as amphibolites, gneiss, granofels as well as gabbros and basalts with a pillow structure. The studied serpentinites of the Frido Unit show mesh, xenomorphic and mylonitic texture. Primary mantle minerals are represented by olivine, orthopyroxene, clinopyroxene and spinel. Pseudomorphic minerals are serpentine, magnetite and tremolite. Olivine is replaced by serpentine forming a mesh texture; orthopyroxene is mostly altered to bastite and in some cases shows exsolution lamellae of clinopyroxene and kink bands. Clinopyroxene is armoured by a tremolite rim. Spinel shows a holly-leaf habit and is often armoured by a corona of Cr-chlorite. The core of the analysed spinel has a Cr-Al spinel composition corresponding to chromite (Al2O3=29-31 wt %; Cr2O3= 28-37 wt%), whereas the rim has a Fe-Cr spinel composition corresponding to ferritchromite (Al2O3= 1-2% wt; Cr2O3=28-30 wt %). The Cr-Al spinel/ferritchromite ratio may be various in different spinel porphyroclasts. Serpentine has a fibrous stretched subidiomorphic habit, it is colourless or pale green

  3. Penguins as bioindicators of mercury contamination in the Southern Ocean: birds from the Kerguelen Islands as a case study.

    Science.gov (United States)

    Carravieri, Alice; Bustamante, Paco; Churlaud, Carine; Cherel, Yves

    2013-06-01

    Seabirds have been used extensively as bioindicators of mercury (Hg) contamination in the marine environment, although information on flightless species like penguins remains limited. In order to assess the use of penguins as bioindicators of Hg contamination in subantarctic and Antarctic marine ecosystems, Hg concentrations were evaluated in the feathers of the four species that breed on the Kerguelen Islands in the southern Indian Ocean. Compared to other seabirds, adult Kerguelen penguins had low to moderate feather Hg concentrations, with an average ranging from 1.96 ± 0.41 μgg(-1) dry weight in the southern rockhopper penguin to 5.85 ± 3.00 μg g(-1) dry weight in the gentoo penguin. The species was a major determinant of Hg contamination, with feather Hg concentrations being lower in the oceanic species (king and crested penguins) than in the coastal one (gentoo penguin). In all species however, feather Hg concentrations were higher in adults than in chicks, reflecting the different periods of Hg bioaccumulation in the internal tissues of the two age classes. The relationship between adult penguin trophic ecology and Hg burdens was investigated using stable isotopes. Feeding habits (reflected by δ(15)N values) had a greater effect on adult feather Hg concentrations when compared to foraging habitats (reflected by δ(13)C values), indicating Hg biomagnification in Kerguelen neritic and oceanic waters. Dietary preferences were crucial in explaining individual feather Hg concentrations, as highlighted by intra-specific variation in Hg levels of gentoo penguins sampled at two different breeding sites of the archipelago. Penguins appear to reflect Hg bioavailability reliably in their foraging environment and could serve as efficient bioindicators of Hg contamination in the Southern Ocean on different spatial and temporal scales. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Austral summer Southern Africa precipitation extremes forced by the El Niño-Southern oscillation and the subtropical Indian Ocean dipole

    Science.gov (United States)

    Hoell, Andrew; Cheng, Linyin

    2017-07-01

    Southern Africa, defined here as the African continent south of 15°S latitude, is prone to seasonal precipitation extremes during December-March that have profound effects on large populations of people. The intensity of summertime precipitation extremes can be remarkable, with wet seasons experiencing up to a doubling of the seasonal average precipitation. Recognizing the importance of understanding the causes of Southern Africa precipitation extremes for the purpose of improved early warning, an 80-member ensemble of atmospheric model simulations forced by observed time-varying boundary conditions during 1979-2016 is used to examine the mechanisms by which December-March precipitation extremes are delivered to Southern Africa and whether the El Niño-Southern Oscillation (ENSO) and the Subtropical Indian Ocean Dipole (SIOD) modify the probabilities of extreme seasonal precipitation occurrences. The model simulations reveal that the synchronous ENSO and SIOD phasing conditions the probability of December-March extreme precipitation occurrences. The probability of extreme wet seasons is greatly increased by La Niña, especially so when combined with a positive SIOD, and greatly decreased by El Niño regardless of SIOD phasing. By contrast, the probability of extreme dry seasons is increased by El Niño and is decreased by La Niña. The mechanisms by which extreme precipitation are delivered are the same regardless of ENSO and SIOD phase. Extreme wet seasons are a result of an anomalous lower tropospheric cyclone over Southern Africa that increases convergence and moisture fluxes into the region while extreme dry seasons are a result of an anomalous lower tropospheric anticyclone that decreases convergence and moisture fluxes into the region.

  5. The effects of dilution and mixed layer depth on deliberate ocean iron fertilization: 1-D simulations of the southern ocean iron experiment (SOFeX)

    Science.gov (United States)

    Krishnamurthy, Aparna; Moore, J. Keith; Doney, Scott C.

    To better understand the role of iron in driving marine ecosystems, the Southern Ocean Iron Experiment (SOFeX) fertilized two surface water patches with iron north and south of the Antarctic Polar Front Zone (APFZ). Using 1-D coupled biological-physical simulations, we examine the biogeochemical dynamics that occurred both inside and outside of the fertilized patches during and shortly after the SOFeX field campaign. We focus, in particular, on three main issues governing the biological response to deliberate iron fertilization: the interaction among phytoplankton, light, macronutrient and iron limitation; dilution and lateral mixing between the fertilized patch and external, unfertilized waters; and the effect of varying mixed layer depth on the light field. At the patch south of the APFZ, sensitivity simulations with no dilution results in the maximum bloom magnitude, whereas dilution with external water extends the development of the north patch bloom by relieving silicon limitation. In model sensitivity studies for both sites, maximum chlorophyll concentration and dissolved inorganic carbon depletion inside the fertilized patches are inversely related to mixed layer depth, similar to the patterns observed across a number of iron fertilization field experiments. Our results suggest that Southern Ocean phytoplankton blooms resulting from natural or deliberate iron fertilization will tend to become iron-light co-limited unless the mixed layer depth is quite shallow.

  6. Penguins as bioindicators of mercury contamination in the Southern Ocean: Birds from the Kerguelen Islands as a case study

    Energy Technology Data Exchange (ETDEWEB)

    Carravieri, Alice, E-mail: carravieri@cebc.cnrs.fr [Centre d' Etudes Biologiques de Chizé, UPR 1934 du Centre National de la Recherche Scientifique, BP 14, 79360 Villiers-en-Bois (France); Littoral Environnement et Sociétés (LIENSs), UMRi 7266 CNRS-Université de la Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle (France); Bustamante, Paco, E-mail: pbustama@univ-lr.fr [Littoral Environnement et Sociétés (LIENSs), UMRi 7266 CNRS-Université de la Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle (France); Churlaud, Carine [Littoral Environnement et Sociétés (LIENSs), UMRi 7266 CNRS-Université de la Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle (France); Cherel, Yves [Centre d' Etudes Biologiques de Chizé, UPR 1934 du Centre National de la Recherche Scientifique, BP 14, 79360 Villiers-en-Bois (France)

    2013-06-01

    Seabirds have been used extensively as bioindicators of mercury (Hg) contamination in the marine environment, although information on flightless species like penguins remains limited. In order to assess the use of penguins as bioindicators of Hg contamination in subantarctic and Antarctic marine ecosystems, Hg concentrations were evaluated in the feathers of the four species that breed on the Kerguelen Islands in the southern Indian Ocean. Compared to other seabirds, adult Kerguelen penguins had low to moderate feather Hg concentrations, with an average ranging from 1.96 ± 0.41 μg g{sup −1} dry weight in the southern rockhopper penguin to 5.85 ± 3.00 μg g{sup −1} dry weight in the gentoo penguin. The species was a major determinant of Hg contamination, with feather Hg concentrations being lower in the oceanic species (king and crested penguins) than in the coastal one (gentoo penguin). In all species however, feather Hg concentrations were higher in adults than in chicks, reflecting the different periods of Hg bioaccumulation in the internal tissues of the two age classes. The relationship between adult penguin trophic ecology and Hg burdens was investigated using stable isotopes. Feeding habits (reflected by δ{sup 15}N values) had a greater effect on adult feather Hg concentrations when compared to foraging habitats (reflected by δ{sup 13}C values), indicating Hg biomagnification in Kerguelen neritic and oceanic waters. Dietary preferences were crucial in explaining individual feather Hg concentrations, as highlighted by intra-specific variation in Hg levels of gentoo penguins sampled at two different breeding sites of the archipelago. Penguins appear to reflect Hg bioavailability reliably in their foraging environment and could serve as efficient bioindicators of Hg contamination in the Southern Ocean on different spatial and temporal scales. - Highlights: • Hg contamination was evaluated in 4 species of penguins at the Kerguelen Islands. • Adults

  7. Dominant covarying climate signals in the Southern Ocean and Antarctic Sea Ice influence during last three decades

    Science.gov (United States)

    Cerrone, Dario; Fusco, Giannetta; Simmonds, Ian; Aulicino, Giuseppe; Budillon, Giorgio

    2017-04-01

    A composite dataset (comprising geopotential height, sea surface temperature, zonal and meridional surface winds, precipitation, cloud cover, surface air temperature, latent plus sensible heat fluxes , and sea ice concentration) has been investigated with the aim of revealing the dominant timescales of variability from 1982 to 2013. Three covarying climate signals associated with variations in the sea ice distribution around Antarctica have been detected through the application of the Multiple-Taper Method with Singular Value Decomposition (MTM-SVD). Features of the established patterns of variation over the Southern Hemisphere (SH) extratropics have been identified in each of these three climate signals in the form of coupled or individual oscillations. The climate patterns considered here are the Southern Annular Mode (SAM), the Pacific-South America (PSA) teleconnection, the Semi-Annual Oscillation (SAO) and Zonal Wavenumber-3 (ZW3) mode. It is shown that most of the sea ice temporal variance is concentrated at the quasi-triennial scale resulting from the constructive superposition of the PSA and ZW3 patterns. In addition the combination of the SAM and SAO patterns is found to promote the interannual sea ice variations underlying a general change in the Southern Ocean atmospheric and oceanic circulations. These two modes of variability are also found consistent with the occurrence of the SAM+/PSA- or SAM-/PSA+ combinations, which could have favored the cooling of the sub-Antarctic and important changes in the Antarctic sea ice distribution since 2000.

  8. Wandering albatrosses document latitudinal variations in the transfer of persistent organic pollutants and mercury to Southern Ocean predators.

    Science.gov (United States)

    Carravieri, Alice; Bustamante, Paco; Tartu, Sabrina; Meillère, Alizée; Labadie, Pierre; Budzinski, Hélène; Peluhet, Laurent; Barbraud, Christophe; Weimerskirch, Henri; Chastel, Olivier; Cherel, Yves

    2014-12-16

    Top marine predators are effective tools to monitor bioaccumulative contaminants in remote oceanic environments. Here, we used the wide-ranging wandering albatross Diomedea exulans to investigate potential geographical variations of contaminant transfer to predators in the Southern Ocean. Blood concentrations of 19 persistent organic pollutants and 14 trace elements were measured in a large number of individuals (N = 180) of known age, sex and breeding status from the subantarctic Crozet Islands. Wandering albatrosses were exposed to a wide range of contaminants, with notably high blood mercury concentrations. Contaminant burden was markedly influenced by latitudinal foraging habitats (inferred from blood δ(13)C values), with individuals feeding in warmer subtropical waters having lower concentrations of pesticides, but higher concentrations of mercury, than those feeding in colder subantarctic waters. Sexual differences in contaminant burden seemed to be driven by gender specialization in feeding habitats, rather than physiological characteristics, with females foraging further north than males. Other individual traits, such as adult age and reproductive status, had little effect on blood contaminant concentrations. Our study provides further evidence of the critical role of global distillation on organic contaminant exposure to Southern Ocean avian predators. In addition, we document an unexpected high transfer of mercury to predators in subtropical waters, which merits further investigation.

  9. Glacial greenhouse-gas fluctuations controlled by ocean circulation changes.

    Science.gov (United States)

    Schmittner, Andreas; Galbraith, Eric D

    2008-11-20

    Earth's climate and the concentrations of the atmospheric greenhouse gases carbon dioxide (CO(2)) and nitrous oxide (N(2)O) varied strongly on millennial timescales during past glacial periods. Large and rapid warming events in Greenland and the North Atlantic were followed by more gradual cooling, and are highly correlated with fluctuations of N(2)O as recorded in ice cores. Antarctic temperature variations, on the other hand, were smaller and more gradual, showed warming during the Greenland cold phase and cooling while the North Atlantic was warm, and were highly correlated with fluctuations in CO(2). Abrupt changes in the Atlantic meridional overturning circulation (AMOC) have often been invoked to explain the physical characteristics of these Dansgaard-Oeschger climate oscillations, but the mechanisms for the greenhouse-gas variations and their linkage to the AMOC have remained unclear. Here we present simulations with a coupled model of glacial climate and biogeochemical cycles, forced only with changes in the AMOC. The model simultaneously reproduces characteristic features of the Dansgaard-Oeschger temperature, as well as CO(2) and N(2)O fluctuations. Despite significant changes in the land carbon inventory, CO(2) variations on millennial timescales are dominated by slow changes in the deep ocean inventory of biologically sequestered carbon and are correlated with Antarctic temperature and Southern Ocean stratification. In contrast, N(2)O co-varies more rapidly with Greenland temperatures owing to fast adjustments of the thermocline oxygen budget. These results suggest that ocean circulation changes were the primary mechanism that drove glacial CO(2) and N(2)O fluctuations on millennial timescales.

  10. Moisture transport between the South Atlantic Ocean and southern Africa: relationships with summer rainfall and associated dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Vigaud, N.; Rouault, M. [University of Cape Town, Oceanography Department, Rondebosch (South Africa); Richard, Y.; Fauchereau, N. [UMR 5210 CNRS/ Universite de Bourgogne, Centre de Recherches de Climatologie, Dijon (France)

    2009-01-15

    Moisture exchange between the South Atlantic and southern Africa is examined in this study through zonal moisture transport. Along the west coast of southern Africa, a multivariate analysis of the zonal flow of moisture computed from NCEP-DOE AMIP II Re-analyses reveals a primary mode of variability typical of variations in intensity and of the latitudinal migration of the circulation associated with the midlatitude westerlies and the South Atlantic anticyclone. In austral summer (January-February), this mode, referred to as the South Atlantic midlatitude mode, is found to be well correlated with rainfall over southern Africa (i.e. to the south of the upper lands surrounding the Congo basin). Its positive/negative phases are found to correspond with surface pressures changes over the South Atlantic region in austral summer when the South Atlantic anticyclone is shifted northward/southward respectively. Such changes are accompanied by dipole-like SST anomalies in the midlatitude South Atlantic Ocean, while simultaneous SST anomalies with a similar structure are also found over South Indian Ocean regions. In January-February, positive/negative events linked to the South Atlantic midlatitude mode are marked by meridional shifts (northward/southward) and weakening/strengthening of the ITCZ over the southern tropics, together with modulations in intensity (weakened/sustained) of the Angola low, which could act as a tropical source of moisture for Tropical Temperate Troughs (TTTs). In association with a strengthened/weakened zonal component of the southern extension of the African Easterly Jet (AEJ), this could modulate the meridional transfer of moisture south of 15 S to the advantage/detriment of Angolan coastal regions, where above/below rainfall are expected. Variations in the latitudinal position (northward/southward) of the South Atlantic anticyclone, and thus of the midlatitude westerlies, are also found to reduce/favour moisture advection towards southern Africa

  11. Southern Ocean Eddy Heat Flux and Eddy-Mean Flow Interactions in Drake Passage

    Science.gov (United States)

    Foppert, Annie

    The Antarctic Circumpolar Current (ACC) is a complex current system composed of multiple jets that is both unique to the world's oceans and relatively under observed compared with other current systems. Observations taken by current- and pressure-recording inverted echo sounders (CPIES) over four years, from November 2007 to November 2011, quantify the mean structure of one of the main jets of the ACC - the Polar Front - in a composite-mean sense. While the array of CPIES deployed in Drake Passage included a 3 x 7 local dynamics array, analysis of the Polar Front makes use of the line of CPIES that spanned the width of Drake Passage (C-Line). The Polar Front tends to prefer one of two locations, separated along the C-Line by 1° of latitude, with the core of the jet centered on corresponding geopotential height contours (with a 17 cm dierence between the northern and southern jets). Potential vorticity fields suggest that the Polar Front is susceptible to baroclinic instability, regardless of whether it is found upstream (farther south along the C-Line) or downstream (farther north along the C-Line) of the Shackleton Fracture Zone (SFZ), yet the core of the jet remains a barrier to smaller-scale mixing, as inferred from estimated mixing lengths. Within the local dynamics array of CPIES, the observed offset between eddy heat flux (EHF) and eddy kinetic energy (EKE) and the alignment of EHF with sea surface height (SSH) standard deviation motivates a proxy for depth-integrated EHF that can be estimated from available satellite SSH data. An eddy-resolving numerical model develops the statistics of a logarithmic fit between SSH standard deviation and cross-frontal EHF that is applied to the ACC in a circumglobal sense. We find 1.06 PW enters the ACC from the north and 0.02 PW exits towards Antarctica. The magnitude of the estimated EHF, along with contemporaneous estimates of the mean heat flux, suggests that the air-sea heat flux south of the PF is an overestimate

  12. Asteroids, ophiuroids and holothurians from the southeastern Weddell Sea (Southern Ocean

    Directory of Open Access Journals (Sweden)

    Julian Gutt

    2014-08-01

    Full Text Available Until the early 1980s, the composition and distribution of the asteroid (starfish, ophiuroid (brittle star and holothurian (sea cucumber bottom fauna of the southeastern Weddell Sea was virtually unknown. This southernmost part of the Atlantic sector of the Southern Ocean is a typical high-latitude Antarctic region located in the circumpolar permanent pack-ice zone. It became accessible for large-scale scientific surveys only through the availability of modern ice-breaking research vessels, such as the German RV “Polarstern”. Here, we describe a dataset of the faunal composition and abundance of starfish, brittle star and sea cucumber assemblages in this area, based on collections from trawl catches carried out during three “Polarstern” cruises in 1983, 1984 and 1985. The set comprises a total of 4,509 records of abundances of 35 asteroid species (with a total of 2,089 specimens and 38 ophiuroid species (with a total of 18,484 specimens from 34 stations, as well as of 66 holothurian species (with a total of 20,918 specimens from 59 stations including zero-abundances (absences. A synthesizing zoogeographical community analysis confirms the presence of three distinct assemblages of asteroids, ophiuroids, and holothurians with highest species richness on the eastern shelf. Overall, starfishes, brittle stars and sea cucumbers were present at all sites investigated in the study area but composition and abundance of asterozoan (asteroids and ophiuroids together and holothurian fauna varied considerably. A synthesizing zoogeographical community analysis confirms the presence of three distinct assemblages of asteroids, ophiuroids, and holothurians with highest species richness on the eastern shelf. In the case of asterozoans, water depth and latitude seemed to be the most important drivers of assemblage distribution and composition. One of the holothurian assemblages was part of the rich macrozoobenthic community dominated by a diverse and

  13. Asteroids, ophiuroids and holothurians from the southeastern Weddell Sea (Southern Ocean).

    Science.gov (United States)

    Gutt, Julian; Piepenburg, Dieter; Voß, Joachim

    2014-01-01

    Until the early 1980s, the composition and distribution of the asteroid (starfish), ophiuroid (brittle star) and holothurian (sea cucumber) bottom fauna of the southeastern Weddell Sea was virtually unknown. This southernmost part of the Atlantic sector of the Southern Ocean is a typical high-latitude Antarctic region located in the circumpolar permanent pack-ice zone. It became accessible for large-scale scientific surveys only through the availability of modern ice-breaking research vessels, such as the German RV "Polarstern". Here, we describe a dataset of the faunal composition and abundance of starfish, brittle star and sea cucumber assemblages in this area, based on collections from trawl catches carried out during three "Polarstern" cruises in 1983, 1984 and 1985. The set comprises a total of 4,509 records of abundances of 35 asteroid species (with a total of 2,089 specimens) and 38 ophiuroid species (with a total of 18,484 specimens) from 34 stations, as well as of 66 holothurian species (with a total of 20,918 specimens) from 59 stations including zero-abundances (absences). A synthesizing zoogeographical community analysis confirms the presence of three distinct assemblages of asteroids, ophiuroids, and holothurians with highest species richness on the eastern shelf. Overall, starfishes, brittle stars and sea cucumbers were present at all sites investigated in the study area but composition and abundance of asterozoan (asteroids and ophiuroids together) and holothurian fauna varied considerably. A synthesizing zoogeographical community analysis confirms the presence of three distinct assemblages of asteroids, ophiuroids, and holothurians with highest species richness on the eastern shelf. In the case of asterozoans, water depth and latitude seemed to be the most important drivers of assemblage distribution and composition. One of the holothurian assemblages was part of the rich macrozoobenthic community dominated by a diverse and abundant epifauna, mainly

  14. The Early Toarcian Oceanic Anoxic Event: A Southern Hemisphere record from Chile

    Science.gov (United States)

    Fantasia, Alicia; Föllmi, Karl B.; Adatte, Thierry; Spangenberg, Jorge E.; Bernárdez, Enrique; Mattioli, Emanuela

    2016-04-01

    The Early Toarcian was marked by important environmental changes, marine oxygen deficiency and extensive organic-rich sediment deposition (T-OAE; ˜182 Ma, Early Jurassic). The T-OAE coincides with a marked negative carbon isotope excursion (CIE) recorded in marine carbonate, and marine and terrestrial organic carbon. This is commonly attributed to the massive release of isotopically light carbon to the atmospheric and oceanic reservoirs derived from the destabilization of methane hydrates from marine sediments and/or the emissions of thermogenic methane from the eruption of the Karoo-Ferrar LIP (e.g., Hesselbo et al., 2000; Kemp et al., 2005; Svensen et al., 2007; Mazzini et al., 2010). Moreover, in most documented marine sections, this episode is marked by a generalized crisis in carbonate production and marine invertebrate extinctions (e.g. Jenkyns, 1988; Röhl et al., 2005; Suan et al., 2001). Several studies of the T-OAE have been conducted on sediments in central and northwest Europe, but only few data are available from the Southern Hemisphere, leading to large uncertainty concerning the exact expression of this event in this part of the world. The aims of this study are to characterize the sediments deposited during the Andean equivalents of the tenuicostatum and falciferum European Zones and establish in which way the T-OAE affected this region. In the Early Jurassic, the Andean basin was in a back-arc setting with marine corridors connected to Panthalassa. In this study, we have generated new high-resolution sedimentological, geochemical and mineralogical data from the sections of El Peñon and Quebrada Asiento, located in Chile in the northeastern area of the city of Copiapó, Atacama region. The biostratigraphy of these sections has been studied by von Hillebrandt and Schidt-Effing (1981) and complemented here by a biostratigraphy based on calcareous nannofossils. The sections consist of a succession of marl, limestone and siltstone of Pliensbachian and

  15. Influence of freshwater input on the skill of decadal forecast of sea ice in the Southern Ocean

    Directory of Open Access Journals (Sweden)

    V. Zunz

    2015-03-01

    Full Text Available Recent studies have investigated the potential link between the freshwater input derived from the melting of the Antarctic ice sheet and the observed recent increase in sea ice extent in the Southern Ocean. In this study, we assess the impact of an additional freshwater flux on the trend in sea ice extent and concentration in simulations with data assimilation, spanning the period 1850–2009, as well as in retrospective forecasts (hindcasts initialised in 1980. In the simulations with data assimilation, the inclusion of an additional freshwater flux that follows an autoregressive process improves the reconstruction of the trend in ice extent and concentration between 1980 and 2009. This is linked to a better efficiency of the data assimilation procedure but can also be due to a better representation of the freshwater cycle in the Southern Ocean. The results of the hindcast simulations show that an adequate initial state, reconstructed thanks to the data assimilation procedure including an additional freshwater flux, can lead to an increase in the sea ice extent spanning several decades that is in agreement with satellite observations. In our hindcast simulations, an increase in sea ice extent is obtained even in the absence of any major change in the freshwater input over the last decades. Therefore, while the additional freshwater flux appears to play a key role in the reconstruction of the evolution of the sea ice in the simulation with data assimilation, it does not seem to be required in the hindcast simulations. The present work thus provides encouraging results for sea ice predictions in the Southern Ocean, as in our simulation the positive trend in ice extent over the last 30 years is largely determined by the state of the system in the late 1970s.

  16. Sources and input mechanisms of hafnium and neodymium in surface waters of the Atlantic sector of the Southern Ocean

    Science.gov (United States)

    Stichel, Torben; Frank, Martin; Rickli, Jörg; Hathorne, Ed C.; Haley, Brian A.; Jeandel, Catherine; Pradoux, Catherine

    2012-10-01

    Radiogenic isotopes of hafnium (Hf) and neodymium (Nd) are powerful tracers for water mass transport and trace metal cycling in the present and past oceans. However, due to the scarcity of available data the processes governing their distribution are not well understood. Here we present the first combined dissolved Hf and Nd isotope and concentration data from surface waters of the Atlantic sector of the Southern Ocean. The samples were collected along the Zero Meridian, in the Weddell Sea and in the Drake Passage during RV Polarstern expeditions ANTXXIV/3 and ANTXXIII/3 in the frame of the International Polar Year (IPY) and the GEOTRACES program. The general distribution of Hf and Nd concentrations in the region is similar. However, at the northernmost station located 200 km southwest of Cape Town a pronounced increase of the Nd concentration is observed, whereas the Hf concentration is minimal, suggesting much less Hf than Nd is released by the weathering of the South African Archean cratonic rocks. From the southern part of the Subtropical Front (STF) to the Polar Front (PF) Hf and Nd show the lowest concentrations (relatively homogeneous (ɛNd ˜ -8 to -8.5) towards the STF, within the Antarctic Circumpolar Current, in the Weddell Gyre, and the Drake Passage. The Hf isotope compositions in the entire study area only show a small range between ɛHf = + 6.1 and +2.8 support Hf to be more readily released from young mafic rocks compared to old continental ones. The Nd isotope composition ranges from ɛNd = -18.9 to -4.0 showing Nd isotopes to be a sensitive tracer for the provenance of weathering inputs into surface waters of the Southern Ocean.

  17. The International Bathymetric Chart of the Southern Ocean (IBCSO) Can we delete the last "White Spots" in Antarctica?

    Science.gov (United States)

    Schenke, H. W.; Black, J.; Jakobsson, M.; Nitsche, F. O.; Tate, A. J.

    2011-12-01

    IBCSO is a major project for the entire Ocean and Earth Science community since it not only contributes to international research programmes but also to global mapping projects like the General Bathymetric Chart of the Oceans (GEBCO) and to the production of Nautical Charts in Antarctic waters. The IBCSO Editorial Board comprises representatives from SCAR-nations conducting specific research in the Antarctic Treaty Area and has an interest in developing an improved bathymetric chart of the Southern Ocean for scientific purposes. These include (a) creating a chart of the seafloor for interpreting seabed geology, (b) building the basis for habitat maps and modelling, and (c) mapping and tracing the pathways of deep oceanic currents. The objective of IBCSO is the production of a homogeneous and seamless bathymetric grid for the Southern Ocean with an associated meta-database. Echosounding data in these harsh regions are heterogeneous in terms of age, acquisition system, environmental condition, accuracy, and documentation. In ice-covered regions, systematic multibeam surveys are rare. As a consequence, the production of a bathymetric grid requires special expertise in hydrography and ocean mapping. Metadata is needed for quality assessment and accurate sonar data processing and gridding. Bathymetric grids have been compiled in regions of special research activities around the Antarctic continent (Bellingshausen/Amundsen Seas, Weddell Sea, Prydz Bay, Kerguelen Plateau, Antarctic Peninsula, and Ross Sea). The results of these regional compilations will be used as basis for the production of the first seamless Circum-Antarctic bathymetric map. The IBCSO version 1 will consequently be an assembly of existing grids produced by different research institutes. The regions not covered will be modelled by using single- and multibeam sonar data in combination with predicted bathymetry. Professional production of this bathymetric chart requires the utilization of a Geographic

  18. Non-Rayleigh control of upper-ocean Cd isotope fractionation in the western South Atlantic

    Science.gov (United States)

    Xie, Ruifang C.; Galer, Stephen J. G.; Abouchami, Wafa; Rijkenberg, Micha J. A.; de Baar, Hein J. W.; De Jong, Jeroen; Andreae, Meinrat O.

    2017-08-01

    We present seawater Cd isotopic compositions in five depth profiles and a continuous surface water transect, from 50°S to the Equator, in the western South Atlantic, sampled during GEOTRACES cruise 74JC057 (GA02 section, Leg 3), and investigate the mechanisms governing Cd isotope cycling in the upper and deep ocean. The depth profiles generally display high ε 112 / 110Cd at the surface and decrease with increasing depth toward values typical of Antarctic Bottom Water (AABW). However, at stations north of the Subantarctic Front, the decrease in ε 112 / 110Cd is interrupted by a shift to values intermediate between those of surface and bottom waters, which occurs at depths occupied by North Atlantic Deep Water (NADW). This pattern is associated with variations in Cd concentration from low surface values to a maximum at mid-depths and is attributed to preferential utilization of light Cd by phytoplankton in the surface ocean. Our new results show that in this region Cd-deficient waters do not display the extreme, highly fractionated ε 112 / 110Cd reported in some earlier studies from other oceanic regions. Instead, in the surface and subsurface southwest (SW) Atlantic, when [Cd] drops below 0.1 nmol kg-1, ε 112 / 110Cd are relatively homogeneous and cluster around a value of +3.7, in agreement with the mean value of 3.8 ± 3.3 (2SD, n = 164) obtained from a statistical evaluation of the global ocean Cd isotope dataset. We suggest that Cd-deficient surface waters may acquire their Cd isotope signature via sorption of Cd onto organic ligands, colloids or bacterial/picoplankton extracellular functional groups. Alternatively, we show that an open system, steady-state model is in good accord with the observed Cd isotope systematics in the upper ocean north of the Southern Ocean. The distribution of ε 112 / 110Cd in intermediate and deep waters is consistent with the water mass distribution, with the north-south variations reflecting changes in the mixing proportion

  19. Drilling of Early Cretaceous Oceanic Anoxic Event 1a in Southern France

    Directory of Open Access Journals (Sweden)

    Wolfgang Kuhnt

    2010-04-01

    Full Text Available The massive concentration of black, laminated, organic carbon-rich shales at certain time periods during the Cretaceous period (∼140–65 Ma led to the concept of Oceanic Anoxic Events (OAEs. These events are characterized by unusually enhanced preservation of organic matteracross environments ranging from the deep oceans to shelf seas. Enhanced productivity of siliceous and organic-walled primary producers and/or strongly dysaerobic or anoxic conditions in all major oceans were both suggested as likely causes (Meyer and Kump, 2008. Fundamental chemical and biological changes in the world ocean must have been associated with these events.

  20. Modeling UV-B Effects on Primary Production Throughout the Southern Ocean Using Multi-Sensor Satellite Data

    Science.gov (United States)

    Lubin, Dan

    2001-01-01

    This study has used a combination of ocean color, backscattered ultraviolet, and passive microwave satellite data to investigate the impact of the springtime Antarctic ozone depletion on the base of the Antarctic marine food web - primary production by phytoplankton. Spectral ultraviolet (UV) radiation fields derived from the satellite data are propagated into the water column where they force physiologically-based numerical models of phytoplankton growth. This large-scale study has been divided into two components: (1) the use of Total Ozone Mapping Spectrometer (TOMS) and Special Sensor Microwave Imager (SSM/I) data in conjunction with radiative transfer theory to derive the surface spectral UV irradiance throughout the Southern Ocean; and (2) the merging of these UV irradiances with the climatology of chlorophyll derived from SeaWiFS data to specify the input data for the physiological models.

  1. Changes in the C, N, and P cycles by the predicted salps-krill shift in the southern ocean

    DEFF Research Database (Denmark)

    Alcaraz, Miquel; Almeda, Rodrigo; Duarte, Carlos M.

    2014-01-01

    was to ascertain the possible consequences of the predicted zooplankton shift from krill to salps in the Southern Ocean for the cycling of biogenic carbon and the concentration and stoichiometry of dissolved inorganic nutrients. The carbon respiratory demands and NH4-N and PO4-P excretion rates of ... time, the higher production by salps of larger, faster sinking fecal pellets will increase the sequestration rate of biogenic carbon. Similarly, the higher N and P excretion rates of zooplankton and the changes in the N:P stoichiometry of the metabolic products will modify the concentration...

  2. Fronts, water masses and heat content variability in the Western Indian sector of the Southern Ocean during austral summer 2004

    Digital Repository Service at National Institute of Oceanography (India)

    AnilKumar, N.; Luis, A.J.; Somayajulu, Y.K.; RameshBabu, V.; Dash, M.K.; Pednekar, S.M.; Babu, K.N.; Sudhakar, M.; Pandey, P.C.

    of the southern sector of the Indian Ocean (Fu, 1986; Nagata et al, 1988; Park et al, 1993; Orsi et al., 1995; Belkin and Gordon, 1996; Sparrow et al., 1996; Holliday and Read, 1998; Park et al., 1998; Reid, 2003) which emphasized that the areas west... compared to previous studies (Park et al, 1993; Belkin and Gordon, 1996; Sparrow et al., 1996) are noted in the position of SAF in the present study. SAF narrowed from ~4? to 1.5? latitude width along 45?E and 57?30?E sections, respectively. On the other...

  3. Ocean warming and seabird communities of the southern California Current System (1987-98): response at multiple temporal scales

    Science.gov (United States)

    Hyrenbach, K. David; Veit, Richard R.

    2003-08-01

    Declines in ocean productivity and shifts in species assemblages along the West Coast of North America during the second half of the XXth century have been attributed to the concurrent warming of the California Current. This paper addresses changes in the avifauna off southern California between May 1987 and September 1998, in response to shifting water mass distributions over short (seabird abundance decreased; the relative importance of cold-water seabirds that dive in pursuit of prey declined; and warm-water species that feed at the surface and plunge to capture prey became more numerous. These community-level changes are consistent with the northward shifts in species ranges and the declining ocean productivity anticipated as a result of global warming. However, the response of individual taxa with an affinity for warm-water and cold-water conditions has been more difficult to predict, due to differences in species-specific responses to ocean warming. The three cold-water species investigated (Sooty Shearwater Puffinus griseus, Cassin's Auklet Ptychoramphus aleuticus, and Rhinoceros Auklet Cerorhinca monocerata) decreased in abundance during this study. On the other hand, only one of the six warm-water species considered (Pink-footed Shearwater, Puffinus creatopus) increased significantly over the long term. Yet, the warm-water Leach's Storm-petrel ( Oceanodroma leucorhoa) increased between 1987 and 1993, and then declined between 1994 and 1998. Moreover, cross-correlations between seasonally adjusted anomalies of bird abundance and ocean temperature revealed that seabirds responded differently to ocean warming over intermediate (1-8 years), and long (8-12 years) time scales. We hypothesize that this nonlinear behavior of seabird populations in response to ocean warming is caused by the juxtaposition of distinct behavioral and demographic responses operating at different temporal scales.

  4. Phytoplankton species composition, abundance and distribution in Fishing area 58 of Indian Ocean sector of Southern Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rathod, V.

    Indian and Pacific Oceans. In Antarctic ecology (ed. Hodgate, M. W.) Academic Press., 1970, London. Pp 148-153. 7 Steyaert, J., Distribution of plankton diatom along an African-Anractic transect. Invest Pesq, 1973a, 37, 295-328. 8 Steyart, J...., Distribution of some selected diatom species during the Belgo-Dutch Antarctic Exp of 1964-65 and 1966- 67. Invest Pesq, 1974, 38, 259-288. 9 Jacques, G., Descolas-Gros, C., Grall, J.R., Sournia, A., Phytoplankton distribution in the Antarctic sector...

  5. Controllability, not chaos, key criterion for ocean state estimation

    Science.gov (United States)

    Gebbie, Geoffrey; Hsieh, Tsung-Lin

    2017-07-01

    The Lagrange multiplier method for combining observations and models (i.e., the adjoint method or 4D-VAR) has been avoided or approximated when the numerical model is highly nonlinear or chaotic. This approach has been adopted primarily due to difficulties in the initialization of low-dimensional chaotic models, where the search for optimal initial conditions by gradient-descent algorithms is hampered by multiple local minima. Although initialization is an important task for numerical weather prediction, ocean state estimation usually demands an additional task - a solution of the time-dependent surface boundary conditions that result from atmosphere-ocean interaction. Here, we apply the Lagrange multiplier method to an analogous boundary control problem, tracking the trajectory of the forced chaotic pendulum. Contrary to previous assertions, it is demonstrated that the Lagrange multiplier method can track multiple chaotic transitions through time, so long as the boundary conditions render the system controllable. Thus, the nonlinear timescale poses no limit to the time interval for successful Lagrange multiplier-based estimation. That the key criterion is controllability, not a pure measure of dynamical stability or chaos, illustrates the similarities between the Lagrange multiplier method and other state estimation methods. The results with the chaotic pendulum suggest that nonlinearity should not be a fundamental obstacle to ocean state estimation with eddy-resolving models, especially when using an improved first-guess trajectory.

  6. Controllability, not chaos, key criterion for ocean state estimation

    Directory of Open Access Journals (Sweden)

    G. Gebbie

    2017-07-01

    Full Text Available The Lagrange multiplier method for combining observations and models (i.e., the adjoint method or 4D-VAR has been avoided or approximated when the numerical model is highly nonlinear or chaotic. This approach has been adopted primarily due to difficulties in the initialization of low-dimensional chaotic models, where the search for optimal initial conditions by gradient-descent algorithms is hampered by multiple local minima. Although initialization is an important task for numerical weather prediction, ocean state estimation usually demands an additional task – a solution of the time-dependent surface boundary conditions that result from atmosphere–ocean interaction. Here, we apply the Lagrange multiplier method to an analogous boundary control problem, tracking the trajectory of the forced chaotic pendulum. Contrary to previous assertions, it is demonstrated that the Lagrange multiplier method can track multiple chaotic transitions through time, so long as the boundary conditions render the system controllable. Thus, the nonlinear timescale poses no limit to the time interval for successful Lagrange multiplier-based estimation. That the key criterion is controllability, not a pure measure of dynamical stability or chaos, illustrates the similarities between the Lagrange multiplier method and other state estimation methods. The results with the chaotic pendulum suggest that nonlinearity should not be a fundamental obstacle to ocean state estimation with eddy-resolving models, especially when using an improved first-guess trajectory.

  7. Warming of the Indian Ocean Threatens Eastern and Southern Africa, but could be Mitigated by Agricultural Development

    Science.gov (United States)

    Funk, Chris; Dettinger, Michael D.; Brown, Molly E.; Michaelsen, Joel C.; Verdin, James P.; Barlow, Mathew; Howell, Andrew

    2008-01-01

    Since 1980, the number of undernourished people in eastern and southern Africa has more than doubled. Rural development stalled and rural poverty expanded during the 1990s. Population growth remains very high and declining per capita agricultural capacity retards progress towards Millennium Development goals. Analyses of in situ station data and satellite observations of precipitation identify another problematic trend. Main growing season rainfall receipts have diminished by approximately 15% in food insecure countries clustered along the western rim of the Indian Ocean. Occurring during the main growing seasons in poor countries dependent on rain fed agriculture, these declines are societally dangerous. Will they persist or intensify? Tracing moisture deficits upstream to an anthropogenically warming Indian Ocean leads us to conclude that further rainfall declines are likely. We present analyses suggesting that warming in the central Indian Ocean disrupts onshore moisture transports, reducing continental rainfall. Thus late 20th century anthropogenic Indian Ocean warming has probably already produced societally dangerous climate change by creating drought and social disruption in some of the world's most fragile food economies. We quantify the potential impacts of the observed precipitation and agricultural capacity trends by modeling millions of undernourished people as a function of rainfall, population, cultivated area, seed and fertilizer use. Persistence of current tendencies may result in a 50% increase in undernourished people. On the other hand, modest increases in per capita agricultural productivity could more than offset the observed precipitation declines. Investing in agricultural development can help mitigate climate change while decreasing rural poverty and vulnerability.

  8. Multi-decadal changes in southern hemisphere subduction rates in a 1/12° ocean model hindcast

    Science.gov (United States)

    Nowatzki, Eva; Patara, Lavinia; Böning, Claus; Karstensen, Johannes

    2017-04-01

    Mode and Intermediate Waters formed in the mid-latitudes of the Southern Ocean represent a major agent for the ventilation of the southern hemisphere lower thermocline, playing a key role in the uptake and intermittent storage of anthropogenic CO2. Long-term hydrographic records as well as modelling studies have provided indications that characteristics of these water masses have been changing over the last decades. Changes in heat, freshwater and momentum fluxes may all contribute to the water mass variability. In this study, we investigate the temporal and spatial variability of Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) formation and its linkages to changing atmospheric conditions with a global ocean - sea-ice model for the time period 1979-2007. The model employs a horizontal resolution of 1/12° for the Southern Ocean and is forced with the CORE-II interannually-varying atmospheric forcing data set. The hindcast simulation is complemented by a second experiment with a repeated 'normal-year' atmospheric forcing in order to separate atmospherically-related changes from stochastic variability and spurious model trends. We find that subduction rates in the density range of SAMW and AAIW are dominated by the lateral induction term and as such are tightly linked to the maximum mixed layer depth (MLD) at the end of winter. The model simulation shows multi-decadal trends in subduction rates, however the trends are not uniform across the density range of SAMW/ AAIW and differ between the Pacific and Indian Ocean sectors. Largest changes in AAIW formation are found in the southeast Pacific, whereas changes in SAMW formation are most pronounced in the Indian Ocean. In the Pacific, the decrease of subduction rates in the AAIW range is contrasted by a positive trend in the SAMW range. The changes in subduction rates are linked to salinity and thus density trends of the winter mixed layer that can be traced to multi-decadal trends in heat and

  9. Control of the Antarctic ice sheet by ocean ice interaction

    Science.gov (United States)

    Bye, John; May, Joel; Simmonds, Ian

    2006-02-01

    The Antarctic ice cap is the largest ice sheet of modern times. It is of considerable importance to predict the sea level variability due to the associated changes in ice volume. We present the results of a simple grounded ice sheet model, developed from Oerlemans [Oerlemans, J., 2002. Global dynamics of the Antarctic Ice Sheet, Climate Dynamics 19, 85-93.], in which the net oceanic evaporation influences the ice cap volume in two ways, through changes in: (i) the accumulation rate, and (ii) the mean sea level. The net evaporation changes are driven by the sea surface temperature (SST) anomaly time series of Howard [Howard, W.R., 1997. A warm future in the past, Nature, 388, 418-419.] for the subantarctic Southern Ocean over the period 220 kyr to the present. The effect of the waxing and waning of the northern hemisphere ice sheets is integrated into the model using an independent model, in which ice melting depends on the SST anomaly and ice calving depends on the sea level anomaly. A series of analytical expressions are derived for the related properties of the coupled ocean-ice system applicable over time scales of 100 kyr, which show, in particular, that the Antarctic ice cap volume changes are due mainly to the effects of the northern hemisphere ice sheets on sea level (which influences ice calving), rather than directly to changes in SST, and hence the ice cap volume is greatest during interglacial periods. This conclusion, which is independent of the specification of the ice melting regime for the northern hemisphere ice sheets, strongly suggests that the changes in accumulation flux estimated from the Vostok proxy temperature data and used in other studies of the Antarctic mass balance have been overestimated. A simple expression is also presented for the lag of ice cap volume to SST, and it is found that the predictions for the mean sea level variability are similar to observations for a melting flux of the northern hemisphere ice sheets about twice their

  10. CDOM Sources and Photobleaching Control Quantum Yields for Oceanic DMS Photolysis

    KAUST Repository

    Galí, Martí

    2016-11-14

    Photolysis is a major removal pathway for the biogenic gas dimethylsulfide (DMS) in the surface ocean. Here we tested the hypothesis that apparent quantum yields (AQY) for DMS photolysis varied according to the quantity and quality of its photosensitizers, chiefly chromophoric dissolved organic matter (CDOM) and nitrate. AQY compiled from the literature and unpublished studies ranged across 3 orders of magnitude at the 330 nm reference wavelength. The smallest AQY(330) were observed in coastal waters receiving major riverine inputs of terrestrial CDOM (0.06-0.5 m3 (mol quanta)-1). In open-ocean waters, AQY(330) generally ranged between 1 and 10 m3 (mol quanta)-1. The largest AQY(330), up to 34 m3 (mol quanta)-1), were seen in the Southern Ocean potentially associated with upwelling. Despite the large AQY variability, daily photolysis rate constants at the sea surface spanned a smaller range (0.04-3.7 d-1), mainly because of the inverse relationship between CDOM absorption and AQY. Comparison of AQY(330) with CDOM spectral signatures suggests there is an interplay between CDOM origin (terrestrial versus marine) and photobleaching that controls variations in AQYs, with a secondary role for nitrate. Our results can be used for regional or large-scale assessment of DMS photolysis rates in future studies.

  11. Deep carbon export from a Southern Ocean iron-fertilized diatom bloom

    NARCIS (Netherlands)

    Smetacek, V.; Klaas, C.; Strass, V.H.; Assmy, P.; Montresor, M.; Cisewski, B.; Savoye, N.; Webb, A.; d'Ovidio, F.; Arrieta, J.M.; Bathmann, U.; Bellerby, R.; Berg, G.M.; Croot, P.; Gonzalez, S.; Henjes, J.; Herndl, G.J.; Hoffmann, L.J.; Leach, H.; Losch, M.; Mills, M.M.; Neill, C.; Peeken, I.; Röttgers, R.; Sachs, O.; Sauter, E.; Schmidt, M.M.; Schwarz, J.; Terbrüggen, A.; Wolf-Gladrow, D.

    2012-01-01

    Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of

  12. Southern Ocean warming and Wilkes Land ice sheet retreat during the mid-Miocene

    NARCIS (Netherlands)

    Sangiorgi, F.; Bijl, P.K.; Passchier, S.; Salzmann, U.; Schouten, S.; McKay, R.M.; Cody, R.D.; Pross, J.; van de Flierdt, T.; Bohaty, S.M.; Levy, R.; Williams, T.; Escutia, C.; Brinkhuis, H.

    2018-01-01

    Observations and model experiments highlight the importance of ocean heat in forcing icesheet retreat during the present and geological past, but past ocean temperature data arevirtually missing in ice sheet proximal locations. Here we document paleoceanographicconditions and the (in)stability of

  13. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE and NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 08 April 1997 to 05 May 1997 (NODC Accession 0000897)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...

  14. Carbon dioxide, temperature, salinity, and other variables collected via surface underway survey from Volunteer Observing Ship AURORA AUSTRALIS in the Southern Oceans (> 60 degrees South) from 1992-10-19 to 2001-12-12 (NODC Accession 0081031)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Surface and Atmospheric fCO2 measurements in the Southern Ocean during the VOS Project line onboard the oceanographic ship Aurora Australis.

  15. Temperature, salinity, nutrient, meteorological data from CTD, bottle casts, and other instruments in the Southern Oceans (>60 degrees South) from the NATHANIEL B. PALMER from 14 February 1994 to 31 March 1994 (NODC Accession 0000484)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CTD, bottle, meteorological, and other data were collected from the Southern Oceans (>60 degrees South) from the Nathaniel B. Palmer from 14 February 1994 to 31...

  16. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE and NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 10 November 1997 to 12 December 1997 (NODC Accession 0000898)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...

  17. Temperature profile and nutrients data collected using bottle casts from the NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 09 November 1994 to 08 December 1994 (NODC Accession 0000899)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the NATHANIEL B. PALMER. Data were collected from...

  18. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE AND NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 12 January 1997 to 09 February 1997 (NODC Accession 0000896)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...

  19. Temperature profile and nutrients data collected using bottle casts from the NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 16 December 1995 to 13 January 1996 (NODC Accession 0000889)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the NATHANIEL B. PALMER. Data were collected from...

  20. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 06 September 1996 to 12 September 1996 (NODC Accession 0000890)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from POLAR DUKE. Data were collected from 06 September...

  1. Application of sediment core modelling to interpreting the glacial-interglacial record of Southern Ocean silica cycling

    Directory of Open Access Journals (Sweden)

    A. Ridgwell

    2007-07-01

    Full Text Available Sediments from the Southern Ocean reveal a meridional divide in biogeochemical cycling response to the glacial-interglacial cycles of the late Neogene. South of the present-day position of the Antarctic Polar Front in the Atlantic sector of the Southern Ocean, biogenic opal is generally much more abundant in sediments during interglacials compared to glacials. To the north, an anti-phased relationship is observed, with maximum opal abundance instead occurring during glacials. This antagonistic response of sedimentary properties provides an important model validation target for testing hypotheses of glacial-interglacial change against, particularly for understanding the causes of the concurrent variability in atmospheric CO2. Here, I illustrate a time-dependent modelling approach to helping understand climates of the past by means of the mechanistic simulation of marine sediment core records. I find that a close match between model-predicted and observed down-core changes in sedimentary opal content can be achieved when changes in seasonal sea-ice extent are imposed, whereas the predicted sedimentary response to iron fertilization on its own is not consistent with sedimentary observations. The results of this sediment record model-data comparison supports previous inferences that the changing cryosphere is the primary driver of the striking features exhibited by the paleoceanographic record of this region.

  2. Application of sediment core modelling to interpreting the glacial-interglacial record of Southern Ocean silica cycling

    Science.gov (United States)

    Ridgwell, A.

    2007-07-01

    Sediments from the Southern Ocean reveal a meridional divide in biogeochemical cycling response to the glacial-interglacial cycles of the late Neogene. South of the present-day position of the Antarctic Polar Front in the Atlantic sector of the Southern Ocean, biogenic opal is generally much more abundant in sediments during interglacials compared to glacials. To the north, an anti-phased relationship is observed, with maximum opal abundance instead occurring during glacials. This antagonistic response of sedimentary properties provides an important model validation target for testing hypotheses of glacial-interglacial change against, particularly for understanding the causes of the concurrent variability in atmospheric CO2. Here, I illustrate a time-dependent modelling approach to helping understand climates of the past by means of the mechanistic simulation of marine sediment core records. I find that a close match between model-predicted and observed down-core changes in sedimentary opal content can be achieved when changes in seasonal sea-ice extent are imposed, whereas the predicted sedimentary response to iron fertilization on its own is not consistent with sedimentary observations. The results of this sediment record model-data comparison supports previous inferences that the changing cryosphere is the primary driver of the striking features exhibited by the paleoceanographic record of this region.

  3. Antarctic icebergs: A significant natural ocean sound source in the Southern Hemisphere

    OpenAIRE

    Matsumoto, Haru; Bohnenstiehl, DelWayne R.; Tournadre, Jean; Robert P. Dziak; Joseph H Haxel; Lau, T. -k. A.; Fowler, Matt; Salo, Sigrid A.

    2014-01-01

    In late 2007, two massive icebergs, C19a and B15a, drifted into open water and slowly disintegrated in the southernmost Pacific Ocean. Archived acoustic records show that the high-intensity underwater sounds accompanying this breakup increased ocean noise levels at mid-to-equatorial latitudes over a period of ∼1.5 years. More typically, seasonal variations in ocean noise, which are characterized by austral summer-highs and winter-lows, appear to be modulated by the annual cycle of Antarctic i...

  4. Evidence for transoceanic migrations by loggerhead sea turtles in the southern Pacific Ocean

    National Research Council Canada - National Science Library

    M.C. Boyle; N.N. FitzSimmons; C.J. Limpus; S. Kelez; X. Velez-Zuazo; M. Waycott

    2009-01-01

    .... Similar migratory behaviour is hypothesized in the South Pacific Ocean as post-hatchling loggerhead turtles are observed in Peruvian fisheries, yet no loggerhead rookeries occur along the coast of South America...

  5. Tectonic control of Triassic sedimentation in southern New Brunswick: Local and regional implications

    Science.gov (United States)

    Nadon, G. C.; Middleton, G. V.

    1984-10-01

    Both regional and local tectonics controlled the sediment distribution in the Fundy half-graben during the Triassic. Locally, alluvial fans built out into the basin from the western boundary fault along what is now the south shore of New Brunswick. The alluvial fan red beds of the Honeycomb Point Formation are covered by fluvial conglomerates of the Quaco Formation, which in turn are buried by a resurgence of alluvial fan deposition represented by the Echo Cove Formation. Pollen recovered from the upper part of the Echo Cove Formation indicates that, regionally, the system of Triassic-Jurassic grabens along the eastern seaboard is composed of two separate graben systems; one stretching from South Carolina to Connecticut, the other from the Gulf of Maine to the southern Grand Banks. Initial graben formation began at the southern end of each system, followed by successive grabens opening toward the north. The areal distribution of both graben systems appears to have been controlled by four large transform-fault systems from the Middle Triassic through the Jurassic. The age and overall distribution of sediments within the Fundy Basin confirm the existence of a hot spot along the Kelvin Seamount chain and refines determination of the position and timing of the initial rifting that led to the formation of the present Atlantic Ocean.

  6. Latitudinal exposure to DDTs, HCB, PCBs, PBDEs and DP in giant petrels (Macronectes spp.) across the Southern Ocean.

    Science.gov (United States)

    Roscales, Jose L; González-Solís, Jacob; Zango, Laura; Ryan, Peter G; Jiménez, Begoña

    2016-07-01

    Studies on Persistent Organic Pollutants (POPs) in Antarctic wildlife are scarce, and usually limited to a single locality. As a result, wildlife exposure to POPs across the Southern Ocean is poorly understood. In this study, we report the differential exposure of the major southern ocean scavengers, the giant petrels, to POPs across a wide latitudinal gradient. Selected POPs (PCBs, HCB, DDTs, PBDEs) and related compounds, such as Dechlorane Plus (DP), were analyzed in plasma of southern giant petrels (Macronectes giganteus) breeding on Livingston (62°S 61°W, Antarctica), Marion (46°S 37°E, sub-Antarctic), and Gough (40°S 10°W, cool temperate) islands. Northern giant petrels (Macronectes halli) from Marion Island were also studied. Stable isotope ratios of C and N (δ(13)C and δ(15)N) were used as dietary tracers of the marine habitat and trophic level, respectively. Breeding locality was a major factor explaining petrel exposure to POPs compared with species and sex. Significant relationships between δ(13)C values and POP burdens, at both inter- and intra-population levels, support latitudinal variations in feeding grounds as a key factor in explaining petrel pollutant burdens. Overall, pollutant levels in giant petrels decreased significantly with latitude, but the relative abundance (%) of the more volatile POPs increased towards Antarctica. DP was found at negligible levels compared with legacy POPs in Antarctic seabirds. Spatial POP patterns found in giant petrels match those predicted by global distribution models, and reinforce the hypothesis of atmospheric long-range transport as the main source of POPs in Antarctica. Our results confirm that wildlife movements out of the polar region markedly increase their exposure to POPs. Therefore, strategies for Antarctic wildlife conservation should consider spatial heterogeneity in exposure to marine pollution. Of particular relevance is the need to clarify the exposure of Antarctic predators to emerging

  7. Evolution of aerosol and CCN properties on the Antarctic Peninsula and Southern Ocean during the spring and summer seasons.

    Science.gov (United States)

    Corrigan, C.; Roberts, G.; Grant, G.

    2014-12-01

    The Southern Ocean has been identified as one of the key regions that need aerosol measurements to improve our models of global climate change. The Portable AERosol Observing System (PAEROS) was deployed in an extended field campaign to measure CCN and aerosols in Antarctica and the Southern Ocean from October 2013 to mid-March 2014. PAEROS is a lightweight, man-portable instrument package developed at the Scripps Institution of Oceanography for the purpose of collecting autonomous measurements of aerosol and cloud condensation nuclei (CCN) properties in remote and challenging environments. The initial phase involved the PAEROS package sampling onboard the R/V Gould during the five-day transit of the Drake Passage between Punta Arenas, Chile and Palmer Station on the Antarctic Peninsula. Upon arrival at Palmer Station, PAEROS was transferred to land and installed on top of a hill about 500 m from the main buildings. For five months, aerosol and CCN number concentrations, size distributions, black carbon concentrations, solar fluxes, and meteorological parameters were continuously measured at Palmer Station. The experiment covered most of an austral spring and summer cycle, during which time the sea ice retreated and biological activity flourished along the Antarctic Peninsula. While crossing the Drake Passage, a distinct gradient in aerosol concentrations was observed with increasing distance from South America. At Palmer Station, the total aerosol concentrations showed a seasonal cycle with lowest concentration in air masses originating from the Antarctic continent and highest number concentrations coming from the ocean during the peak of biological activity. Chlorophyll concentrations are routinely measured at Palmer Station and showed peak activity in the month of January 2014. Total aerosol and CCN concentrations increased in late spring (November) as the sea ice recedes from Palmer Station, probably a result of being closer to sea spray and biological activity

  8. Gaseous elemental mercury in the marine boundary layer and air-sea flux in the Southern Ocean in austral summer.

    Science.gov (United States)

    Wang, Jiancheng; Xie, Zhouqing; Wang, Feiyue; Kang, Hui

    2017-12-15

    Gaseous elemental mercury (GEM) in the marine boundary layer (MBL), and dissolved gaseous mercury (DGM) in surface seawater of the Southern Ocean were measured in the austral summer from December 13, 2014 to February 1, 2015. GEM concentrations in the MBL ranged from 0.4 to 1.9ngm -3 (mean±standard deviation: 0.9±0.2ngm -3 ), whereas DGM concentrations in surface seawater ranged from 7.0 to 75.9pgL -1 (mean±standard deviation: 23.7±13.2pgL -1 ). The occasionally observed low GEM in the MBL suggested either the occurrence of atmospheric mercury depletion in summer, or the transport of GEM-depleted air from the Antarctic Plateau. Elevated GEM concentrations in the MBL and DGM concentrations in surface seawater were consistently observed in the ice-covered region of the Ross Sea implying the influence of the sea ice environment. Diminishing sea ice could cause more mercury evasion from the ocean to the air. Using the thin film gas exchange model, the air-sea fluxes of gaseous mercury in non-ice-covered area during the study period were estimated to range from 0.0 to 6.5ngm -2 h -1 with a mean value of 1.5±1.8ngm -2 h -1 , revealing GEM (re-)emission from the East Southern Ocean in summer. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Changes in oxygenation reveal an asymmetry in the Antarctic Intermediate Water production of the Pacific sector of the Southern Ocean during the Last Glacial Maximum

    Science.gov (United States)

    Chase, Z.; Durand, A.; Noble, T. L.; Townsend, A.; Bostock, H. C.; Neil, H.; Jaccard, S.

    2016-12-01

    We studied 21 sediment cores located on the Campbell and Challenger Plateaux surrounding New Zealand to investigate changes in oxygenation at intermediate depths of southwest Pacific sector the Southern-Ocean since the Last Glacial Maximum (LGM). The cores span Antarctic Intermediate Water (AAIW) and Upper Circumpolar Deep Water (UCDW). The sedimentary concentrations of redox sensitive elements reveal that intermediate depths of the southwest Pacific sector of the Southern Ocean (800-1500m) were oxygen depleted during the LGM compared to the Holocene and present day. These data, together with variations in benthic foraminiferal δ13C are consistent with a shallower AAIW-UCDW boundary in the southwest Pacific sector of the Southern Ocean during the LGM (800m vs 1200m today). Moreover, δ 13C data indicate that AAIW still bathed the shallower core sites (Holocene; however redox sensitive elements in these cores also reveal lower oxygen content in glacial AAIW compared to the Holocene. These findings are in opposition to what has been found in the South East Pacific sector of the Southern Ocean, where redox sensitive element variations showed that AAIW was more oxygenated and extended deeper during the LGM. Therefore, during the LGM, AAIW extent and oxygen content were asymmetrical between the eastern and western regions of the Pacific sector of the Southern Ocean. Consequently, the AAIW repartition in the Pacific sector of the Southern Ocean was dramatically different during the LGM compared to present, where AAIW depth range is quasi constant. Differences in the position of the Westerlies between the eastern and western side, as well as differences in sea-ice melt discharges could have potentially driven this glacial asymmetry.

  10. Long-term vegetation, climate and ocean dynamics inferred from a 73,500 years old marine sediment core (GeoB2107-3) off southern Brazil

    Science.gov (United States)

    Gu, Fang; Zonneveld, Karin A. F.; Chiessi, Cristiano M.; Arz, Helge W.; Pätzold, Jürgen; Behling, Hermann

    2017-09-01

    Long-term changes in vegetation and climate of southern Brazil, as well as ocean dynamics of the adjacent South Atlantic, were studied by analyses of pollen, spores and organic-walled dinoflagellate cysts (dinocysts) in marine sediment core GeoB2107-3 collected offshore southern Brazil covering the last 73.5 cal kyr BP. The pollen record indicates that grasslands were much more frequent in the landscapes of southern Brazil during the last glacial period if compared to the late Holocene, reflecting relatively colder and/or less humid climatic conditions. Patches of forest occurred in the lowlands and probably also on the exposed continental shelf that was mainly covered by salt marshes. Interestingly, drought-susceptible Araucaria trees were frequent in the highlands (with a similar abundance as during the late Holocene) until 65 cal kyr BP, but were rare during the following glacial period. Atlantic rainforest was present in the northern lowlands of southern Brazil during the recorded last glacial period, but was strongly reduced from 38.5 until 13.0 cal kyr BP. The reduction was probably controlled by colder and/or less humid climatic conditions. Atlantic rainforest expanded to the south since the Lateglacial period, while Araucaria forests advanced in the highlands only during the late Holocene. Dinocysts data indicate that the Brazil Current (BC) with its warm, salty and nutrient-poor waters influenced the study area throughout the investigated period. However, variations in the proportion of dinocyst taxa indicating an eutrophic environment reflect the input of nutrients transported mainly by the Brazilian Coastal Current (BCC) and partly discharged by the Rio Itajaí (the major river closest to the core site). This was strongly related to changes in sea level. A stronger influence of the BCC with nutrient rich waters occurred during Marine Isotope Stage (MIS) 4 and in particular during the late MIS 3 and MIS 2 under low sea level. Evidence of Nothofagus pollen

  11. Sea ice contribution to the air-sea CO{sub 2} exchange in the Arctic and Southern Oceans

    Energy Technology Data Exchange (ETDEWEB)

    Rysgaard, Soeren (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Centre for Earth Observation Science, CHR Faculty of Environment Earth and Resources, Univ. of Manitoba, Winnipeg (Canada)), e-mail: rysgaard@natur.gl; Bendtsen, Joergen (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Centre for Ice and Climate, Niels Bohr Inst., Univ. of Copenhagen, Copenhagen O (Denmark)); Delille, Bruno (Unit' e d' Oceanographie Chimique, Interfacultary Centre for Marine Research, Universite de Liege, Liege (Belgium)); Dieckmann, Gerhard S. (Alfred Wegener Inst. for Polar and Marine Research, Bremerhaven (Germany)); Glud, Ronnie N. (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Scottish Association of Marine Sciences, Scotland UK, Southern Danish Univ. and NordCee, Odense M (Denmark)); Kennedy, Hilary; Papadimitriou, Stathys (School of Ocean Sciences, Bangor Univ., Menai Bridge, Anglesey, Wales (United Kingdom)); Mortensen, John (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark)); Thomas, David N. (School of Ocean Sciences, Bangor Univ., Menai Bridge, Anglesey, Wales (United Kingdom); Finnish Environment Inst. (SYKE), Marine Research Centre, Helsinki (Finland)); Tison, Jean-Louis (Glaciology Unit, Dept. of Earth and Environmental Sciences, Universite Libre de Bruxelles, Bruxelles, (Belgium))

    2011-11-15

    Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO{sub 2} and the subsequent effect on air-sea CO{sub 2} exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air-sea CO{sub 2} exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO{sub 2} uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO{sub 2} uptake in ice-free polar seas. This sea-ice driven CO{sub 2} uptake has not been considered so far in estimates of global oceanic CO{sub 2} uptake. Net CO{sub 2} uptake in sea-ice-covered oceans can be driven by; (1) rejection during sea-ice formation and sinking of CO{sub 2}-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air-sea CO{sub 2} exchange during winter, and (3) release of CO{sub 2}-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO{sub 2} drawdown during primary production in sea ice and surface oceanic waters

  12. Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches

    Science.gov (United States)

    Closset, I.; Lasbleiz, M.; Leblanc, K.; Quéguiner, B.; Cavagna, A.-J.; Elskens, M.; Navez, J.; Cardinal, D.

    2014-10-01

    A massive diatom bloom is observed each year in the surface waters of the naturally Fe-fertilized Kerguelen Plateau (Southern Ocean). We measured biogenic silica production and dissolution fluxes (ρSi and ρDiss, respectively) in the mixed layer in the vicinity of the Kerguelen Plateau during austral spring 2011 (KEOPS-2 cruise). We compare results from a high-nutrient low-chlorophyll reference station and stations with different degrees of iron enrichment and bloom conditions. Above the plateau biogenic ρSi are among the highest reported so far in the Southern Ocean (up to 47.9 mmol m-2 d-1). Although significant (10.2 mmol m-2 d-1 on average), ρDiss were generally much lower than production rates. Uptake ratios (ρSi : ρC and ρSi : ρN) confirm that diatoms strongly dominate primary production in this area. At the bloom onset, decreasing dissolution-to-production ratios (D : P) indicate that the remineralization of silica could sustain most of the low silicon uptake and that the system progressively shifts toward a silica production regime which must be mainly supported by new source of silicic acid. Moreover, by comparing results from the two KEOPS expeditions (spring 2011 and summer 2005), we suggest that there is a seasonal evolution of the processes decoupling Si and N cycles in the area. Indeed, the consumption of H4SiO4 standing stocks occurs only during the growing stage of the bloom when strong net silica production is observed, contributing to higher H4SiO4 depletion relative to NO3-. Then, the decoupling of H4SiO4 and NO3- is mainly controlled by the more efficient nitrogen recycling relative to Si. Gross Si : N uptake ratios were higher in the Fe-rich regions compared to the high-nutrient low-chlorophyll (HNLC) area, likely due to different diatom communities. This suggests that the diatom responses to natural Fe fertilization are more complex than previously thought, and that natural iron fertilization over long timescales does not necessarily

  13. Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated from Si isotopic approaches

    Science.gov (United States)

    Closset, I.; Lasbleiz, M.; Leblanc, K.; Quéguiner, B.; Cavagna, A.-J.; Elskens, M.; Navez, J.; Cardinal, D.

    2014-05-01

    A massive diatom-bloom is observed each year in the surface waters of the naturally Fe fertilized Kerguelen Plateau (Southern Ocean). We measured biogenic silica production and dissolution fluxes in the mixed layer in the vicinity of the Kerguelen Plateau during austral spring 2011 (KEOPS-2 cruise). We compare results from a High-Nutrient Low-Chlorophyll reference station and stations with different degrees of iron enrichment and bloom conditions. Above the Plateau biogenic silica production fluxes are among the highest reported so far in the Southern Ocean (up to 47.9 mmol m-2 d-1). Although significant (10.2 mmol m-2 d-1 in average), silica dissolution rates were generally much lower than production rates. Uptake ratios (Si:C and Si:N) confirm that diatoms strongly dominate the primary production in this area. At the bloom onset, decreasing dissolution to production ratios (D:P) indicate that the remineralization of silica could sustained most of the low silicon uptake and that the system progressively shifts toward a silica production regime which must be mainly supported by new source of silicic acid. Moreover, by comparing results from the two KEOPS-expeditions (spring 2011 and summer 2005), we suggest that there is a seasonal evolution on the processes decoupling Si and N cycles in the area. Indeed, the consumption of H4SiO4 standing stocks occurs only during the growing stage of the bloom when strong net silica production is observed, contributing to a higher H4SiO4 depletion relative to NO3-. Then, the decoupling between H4SiO4 and NO3- is mainly controlled by the more efficient nitrogen recycling relative to Si. Gross-Si:N uptake ratios were higher in the Fe-rich regions compared to the HNLC area, likely due to different diatoms communities. This suggests that the diatom responses to natural Fe fertilization are more complex than previously thought, and that natural iron fertilization over long time scales does not necessarily decrease Si:N uptake ratios

  14. Structure and tectonic evolution of the Southern Eurasia Basin, Arctic Ocean

    Science.gov (United States)

    Sekretov, Sergey B.

    2002-07-01

    Multichannel seismic reflection data acquired by Marine Arctic Geological Expedition (MAGE) of Murmansk, Russia in 1990 provide the first view of the geological structure of the Arctic region between 77-80°N and 115-133°E, where the Eurasia Basin of the Arctic Ocean adjoins the passive-transform continental margin of the Laptev Sea. South of 80°N, the oceanic basement of the Eurasia Basin and continental basement of the Laptev Sea outer margin are covered by 1.5 to 8 km of sediments. Two structural sequences are distinguished in the sedimentary cover within the Laptev Sea outer margin and at the continent/ocean crust transition: the lower rift sequence, including mostly Upper Cretaceous to Lower Paleocene deposits, and the upper post-rift sequence, consisting of Cenozoic sediments. In the adjoining Eurasia Basin of the Arctic Ocean, the Cenozoic post-rift sequence consists of a few sedimentary successions deposited by several submarine fans. Based on the multichannel seismic reflection data, the structural pattern was determined and an isopach map of the sedimentary cover and tectonic zoning map were constructed. A location of the continent/ocean crust transition is tentatively defined. A buried continuation of the mid-ocean Gakkel Ridge is also detected. This study suggests that south of 78.5°N there was the cessation in the tectonic activity of the Gakkel Ridge Rift from 33-30 until 3-1 Ma and there was no sea-floor spreading in the southernmost part of the Eurasia Basin during the last 30-33 m.y. South of 78.5°N all oceanic crust of the Eurasia Basin near the continental margin of the Laptev Sea was formed from 56 to 33-30 Ma.

  15. Impacts of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in the Goddard Earth Observing System Version 5 (GEOS-5)

    Science.gov (United States)

    Li, Feng; Vikhliaev, Yury V.; Newman, Paul A.; Pawson, Steven; Perlwitz, Judith; Waugh, Darryn W.; Douglass, Anne R.

    2016-01-01

    Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer's evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. In this study we investigate the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean. Two sets of 1960-2010 ensemble transient simulations are conducted with the coupled ocean version of the Goddard Earth Observing System Model, version 5: one with interactive stratospheric chemistry and the other with prescribed ozone derived from the same interactive simulations. The model's climatology is evaluated using observations and reanalysis. Comparison of the 1979-2010 climate trends between these two simulations reveals that interactive chemistry has important effects on climate change not only in the Antarctic stratosphere, troposphere, and surface, but also in the Southern Ocean and Antarctic sea ice. Interactive chemistry causes stronger Antarctic lower stratosphere cooling and circumpolar westerly acceleration during November-December-January. It enhances stratosphere-troposphere coupling and leads to significantly larger tropospheric and surface westerly changes. The significantly stronger surface wind stress trends cause larger increases of the Southern Ocean Meridional Overturning Circulation, leading to year-round stronger ocean warming near the surface and enhanced Antarctic sea ice decrease.

  16. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from SOUTHERN SURVEYOR in the North Pacific Ocean and South Pacific Ocean from 2009-02-03 to 2009-03-24 (NODC Accession 0108082)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108082 includes chemical, discrete sample, physical and profile data collected from SOUTHERN SURVEYOR in the North Pacific Ocean and South Pacific...

  17. Dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, PAR Sensor and other instruments from MIRAI in the Indian Ocean and Southern Oceans from 2013-01-06 to 2013-02-15 (NCEI Accession 0156925)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0156925 includes biological, chemical, discrete sample, optical, physical and profile data collected from MIRAI in the Indian Ocean and Southern...

  18. Southern Carpathian rock glaciers: Inventory, distribution and environmental controlling factors

    Science.gov (United States)

    Onaca, Alexandru; Ardelean, Florina; Urdea, Petru; Magori, Brigitte

    2017-09-01

    Rock glaciers are valuable diagnostic landforms indicating permafrost creeping during their genesis and activity. Based on the analysis of high quality air-orthophoto and field work, a first polygon-based inventory of rock glaciers from the Southern Carpathians has been elaborated. In total, 306 rock glaciers were included in the inventory comprising 79 debris and 227 talus rock glaciers. Most of these landforms were classified as relict (258), while only 48, covering 2.81 km2, were considered intact. The size of rock glaciers, considered as a proxy for past environmental conditions, and the relationships with the predictor variables (lithology, aspect, contributing area, geographic coordinates, elevation and slope range) were analysed using bivariate statistics, analysis of variance (ANOVA) and various post hoc tests. The statistical analysis revealed that the rock glaciers occurring in the highest mountain ranges in areas composed of granites and granodiorites are considerably larger than the others, because their duration of activity is greater. Strong dependences between rock glacier size and other topographic attributes (contributing area, aspect and slope range) were also confirmed. The rock glacier distribution in the Southern Carpathians is clearly controlled by topography, lithology and debris availability. The abundance of rock glaciers increases with altitude, but their size decreases slightly. In mountain units where granites and granodiorites predominate (Retezat and Parâng Mountains), the density of rock glaciers and the mean specific area covered by these spectacular landforms are considerably higher than in other areas. The higher continentality effects of the Southern Carpathians enabled the formation of rock glaciers at substantially lower elevations than in the Alps. The mean altitude of intact rock glaciers front, which could be used as a morphological indicator of discontinuous permafrost, is located at 2088 m.

  19. Controls on the spatial distribution of oceanic δ13CDIC

    Directory of Open Access Journals (Sweden)

    P. B. Holden

    2013-03-01

    Full Text Available We describe the design and evaluation of a large ensemble of coupled climate–carbon cycle simulations with the Earth system model of intermediate complexity GENIE. This ensemble has been designed for application to a range of carbon cycle questions, including the causes of late-Quaternary fluctuations in atmospheric CO2. Here we evaluate the ensemble by applying it to a transient experiment over the recent industrial era (1858 to 2008 AD. We employ singular vector decomposition and principal component emulation to investigate the spatial modes of ensemble variability of oceanic dissolved inorganic carbon (DIC δ13C, considering both the spun-up pre-industrial state and the transient change. These analyses allow us to separate the natural (pre-industrial and anthropogenic controls on the δ13CDIC distribution. We apply the same dimensionally-reduced emulation techniques to consider the drivers of the spatial uncertainty in anthropogenic DIC. We show that the sources of uncertainty related to the uptake of anthropogenic δ13CDIC and DIC are quite distinct. Uncertainty in anthropogenic δ13C uptake is controlled by air–sea gas exchange, which explains 63% of modelled variance. This mode of variability is largely absent from the ensemble variability in CO2 uptake, which is rather driven by uncertainties in thermocline ventilation rates. Although the need to account for air–sea gas exchange is well known, these results suggest that, to leading order, uncertainties in the ocean uptake of anthropogenic 13C and CO2 are governed by very different processes. This illustrates the difficulties in reconstructing one from the other, and furthermore highlights the need for careful targeting of both δ13CDIC and DIC observations to better constrain the ocean sink of anthropogenic CO2.

  20. Controls on 231Pa/230Th in the Indian Ocean: Circulation or Productivity?

    Science.gov (United States)

    Thomas, A. L.; Henderson, G. M.; McCave, N.

    2004-12-01

    (231Paxs/230Thxs)0 ratios in marine sediments are a potential proxy of palaeoproductivity and/or past ocean circulation. Studies in the Atlantic have demonstrated the particular potential of this proxy to assess the rate of past circulation AƒAøAøâ_sA¬Aøâ,¬Å" an important environmental variable which is otherwise difficult to reconstruct {[1, 2]}. In this study, we present new water-column and sediment data from the western Indian Ocean to improve understanding of the controls on (231Paxs/230Thxs)0 and test the use of this proxy. The Indian Ocean differs from the Atlantic because deep waters forming in the Southern Ocean and transported into the basin have high rather than low Pa and Th concentrations [3]. The ability to reconstruct past rates of flow into the Indian Ocean would be a powerful new use of Pa/Th, but no data presently exist to test this application. Water samples (10 litre), surface sediments, and a 5.5m Kasten core were collected on the Charles Darwin cruise CD154 from the area East of Madagascar. The down-core record, from10°S extends to 150 ka, and is coupled with a stable isotope stratigraphy and a sortable silt record. Water and sediment samples were analysed for isotopes of Pa, Th and U on a Nu Instruments MC-ICP-MS. The water-column dataset (26 samples) indicate that Pa concentrations are high in NADW transported into the Indian Ocean from the Atlantic, while opal scavenging has lowered Pa concentrations in deeper water masses. Sedimentary 230Th data indicate that there has been significant sediment focusing and that sediment mass fluxes are low. Preliminary sedimentary Pa/Th data show little relation to the sortable silt record. Ongoing Pa/Th and Ba data will complete this downcore record and allow comparison of a Pa/Th record with independent proxies of current speed and productivity in the same core. [1] E.F. Yu, et al, Nature 379, 689-694, 1996. [2] J.F. McManus, et al, Nature 428, 834-837, 2004. [3] M. M. Rutgers van der Loeff

  1. Warming of the Indian Ocean threatens eastern and southern African food security but could be mitigated by agricultural development

    Science.gov (United States)

    Funk, Chris C.; Dettinger, Michael D.; Michaelsen, Joel C.; Verdin, James P.; Brown, Molly E.; Barlow, Mathew; Hoell, Andrew

    2008-01-01

    Since 1980, the number of undernourished people in eastern and southern Africa has more than doubled. Rural development stalled and rural poverty expanded during the 1990s. Population growth remains very high, and declining per-capita agricultural capacity retards progress toward Millennium Development goals. Analyses of in situ station data and satellite observations of precipitation have identified another problematic trend: main growing-season rainfall receipts have diminished by ???15% in food-insecure countries clustered along the western rim of the Indian Ocean. Occurring during the main growing seasons in poor countries dependent on rain-fed agriculture, these declines are societally dangerous. Will they persist or intensify? Tracing moisture deficits upstream to an anthropogenically warming Indian Ocean leads us to conclude that further rainfall declines are likely. We present analyses suggesting that warming in the central Indian Ocean disrupts onshore moisture transports, reducing continental rainfall. Thus, late 20th-century anthropogenic Indian Ocean warming has probably already produced societally dangerous climate change by creating drought and social disruption in some of the world's most fragile food economies. We quantify the potential impacts of the observed precipitation and agricultural capacity trends by modeling 'millions of undernourished people' as a function of rainfall, population, cultivated area, seed, and fertilizer use. Persistence of current tendencies may result in a 50% increase in undernourished people by 2030. On the other hand, modest increases in per-capita agricultural productivity could more than offset the observed precipitation declines. Investing in agricultural development can help mitigate climate change while decreasing rural poverty and vulnerability. ?? 2008 by The National Academy of Sciences of the USA.

  2. Southern hemisphere climate variability as represented by an ocean-atmosphere coupled model

    CSIR Research Space (South Africa)

    Beraki, A

    2012-09-01

    Full Text Available , 1996: Relationship of air temperature in New Zealand to regional anomalies in sea-surface temperature and atmospheric circulation. Int. J. Climatol., 16, 405?425. Beraki, A., D. DeWitt, W.A. Landman and O. Cobus, 2011: Ocean-Atmosphere Coupled... variability as represented by an ocean-atmosphere coupled model Asmerom Beraki1,2, Willem A. Landman2,3 and David DeWitt4 1South African Weather Service Pretoria, South Africa, asmerom.beraki@weahtersa.co.za 2Departement of Geography...

  3. Export fluxes in a naturally iron-fertilized area of the Southern Ocean - Part 2: Importance of diatom resting spores and faecal pellets for export

    Science.gov (United States)

    Rembauville, M.; Blain, S.; Armand, L.; Quéguiner, B.; Salter, I.

    2015-06-01

    The biological composition of the material exported to a moored sediment trap located under the winter mixed layer of the naturally fertilized Kerguelen Plateau in the Southern Ocean was studied over an annual cycle. Despite iron availability in spring, the annual particulate organic carbon (POC) export (98.2 mmol m-2) at 289 m was low, but annual biogenic silica export was significant (114 mmol m-2). This feature was related to the abundance of empty diatom cells and the ratio of full to empty cells exerted a first-order control in BSi : POC export stoichiometry of the biological pump. Chaetoceros Hyalochaete spp. and Thalassiosira antarctica resting spores were responsible for more than 60% of the annual POC flux that occurred during two very short export events of 80%). The seasonal progression of faecal pellet types revealed a clear transition from small spherical shapes (small copepods) in spring, to larger cylindrical and ellipsoid shapes in summer (euphausiids and large copepods) and finally to large tabular shapes (salps) in autumn and winter. We propose in this high-biomass, low-export (HBLE) environment that small but highly silicified and fast-sinking resting spores are able to bypass the intense grazing pressure and efficient carbon transfer to higher trophic levels that are responsible for the low fluxes observed the during the remainder of the year. More generally our study also provides a statistical framework linking the ecological succession of diatom and zooplankton communities to the seasonality of carbon and silicon export within an iron-fertilized bloom region in the Southern Ocean.

  4. Export fluxes in a naturally fertilized area of the Southern Ocean, the Kerguelen Plateau: ecological vectors of carbon and biogenic silica to depth (Part 2)

    Science.gov (United States)

    Rembauville, M.; Blain,