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Sample records for island southern ocean

  1. Osmium isotopic evidence for ancient subcontinental lithospheric mantle beneath the kerguelen islands, southern indian ocean

    PubMed

    Hassler; Shimizu

    1998-04-17

    Upper mantle xenoliths found in ocean island basalts are an important window through which the oceanic mantle lithosphere may be viewed directly. Osmium isotopic data on peridotite xenoliths from the Kerguelen Islands, an archipelago that is located on the northern Kerguelen Plateau in the southern Indian Ocean, demonstrate that pieces of mantle of diverse provenance are present beneath the Islands. In particular, peridotites with unradiogenic osmium and ancient rhenium-depletion ages (to 1.36 x 10(9) years old) may be pieces of the Gondwanaland subcontinental lithosphere that were incorporated into the Indian Ocean lithosphere as a result of the rifting process. PMID:9545216

  2. Airborne dust transport to the eastern Pacific Ocean off southern California: Evidence from San Clemente Island

    NASA Astrophysics Data System (ADS)

    Muhs, Daniel R.; Budahn, James; Reheis, Marith; Beann, Jossh; Skipp, Gary; Fisher, Eric

    2007-07-01

    Islands are natural dust traps, and San Clemente Island, California, is a good example. Soils on marine terraces cut into Miocene andesite on this island are clay-rich Vertisols or Alfisols with vertic properties. These soils are overlain by silt-rich mantles, 5-20 cm thick, that contrast sharply with the underlying clay-rich subsoils. The silt mantles have a mineralogy that is distinct from the island bedrock. Silt mantles are rich in quartz, which is rare in the island andesite. The clay fraction of the silt mantles is dominated by mica, also absent from local andesite, and contrasts with the subsoils, dominated by smectite. Ternary plots of immobile trace elements (Sc-Th-La and Ta-Nd-Cr) show that the island andesite has a composition intermediate between average upper continental crust and average oceanic crust. In contrast, the silt and, to a lesser extent, clay fractions of the silt mantles have compositions closer to average upper continental crust. The silt mantles have particle size distributions similar to loess and Mojave Desert dust, but are coarser than long-range-transported Asian dust. We infer from these observations that the silt mantles are derived from airborne dust from the North American mainland, probably river valleys in the coastal mountains of southern California and/or the Mojave Desert. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when "Santa Ana" conditions prevail, caused by a high-pressure cell centered over the Great Basin. Examination of satellite imagery shows that easterly Santa Ana winds carry abundant dust to the eastern Pacific Ocean and the California Channel Islands. Airborne dust from mainland North America may be an important component of the offshore sediment budget in the easternmost Pacific Ocean, a finding of potential biogeochemical and climatic significance.

  3. Airborne dust transport to the eastern Pacific Ocean off southern California: Evidence from San Clemente Island

    USGS Publications Warehouse

    Muhs, D.R.; Budahn, J.; Reheis, M.; Beann, J.; Skipp, G.; Fisher, E.

    2007-01-01

    Islands are natural dust traps, and San Clemente Island, California, is a good example. Soils on marine terraces cut into Miocene andesite on this island are clay-rich Vertisols or Alfisols with vertic properties. These soils are overlain by silt-rich mantles, 5-20 cm thick, that contrast sharply with the underlying clay-rich subsoils. The silt mantles have a mineralogy that is distinct from the island bedrock. Silt mantles are rich in quartz, which is rare in the island andesite. The clay fraction of the silt mantles is dominated by mica, also absent from local andesite, and contrasts with the subsoils, dominated by smectite. Ternary plots of immobile trace elements (Sc-Th-La and Ta-Nd-Cr) show that the island andesite has a composition intermediate between average upper continental crust and average oceanic crust. In contrast, the silt and, to a lesser extent, clay fractions of the silt mantles have compositions closer to average upper continental crust. The silt mantles have particle size distributions similar to loess and Mojave Desert dust, but are coarser than long-range-transported Asian dust. We infer from these observations that the silt mantles are derived from airborne dust from the North American mainland, probably river valleys in the coastal mountains of southern California and/or the Mojave Desert. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when "Santa Ana" conditions prevail, caused by a high-pressure cell centered over the Great Basin. Examination of satellite imagery shows that easterly Santa Ana winds carry abundant dust to the eastern Pacific Ocean and the California Channel Islands. Airborne dust from mainland North America may be an important component of the offshore sediment budget in the easternmost Pacific Ocean, a finding of potential biogeochemical and climatic significance.

  4. 10Be application to soil development on Marion Island, southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Haussmann, N.; Aldahan, A.; Boelhouwers, J.; Possnert, G.

    2010-04-01

    Marion Island, located in the southern Indian Ocean, constitutes the summit of an active shield volcano. It is a small terrestrial environment where glacially abraded bedrock became exposed c × 10 kyr ago. These conditions provide an interesting possibility for the assessment of 10Be accumulation rates and their application to soil erosion studies on the island. 10Be concentrations were measured in precipitation, soil profiles and an Azorella selago cushion plant. The data reveal a 10Be precipitation flux several times higher than model prediction. Estimation of the 10Be accumulation based on the soil inventory suggests a span between 2000 and 7000 yr. This time span is not in accordance with the accepted notion that the island was covered with ice about 10,000 yr ago and suggests either removal of 10Be from the soil profile, an overestimated Holocene 10Be-flux or a delayed soil development history. Our results provide new data on 10Be concentrations from the sub-Antarctic islands and contribute towards enlarging the southern-hemisphere 10Be database.

  5. Patterns in floral traits and plant breeding systems on Southern Ocean Islands

    PubMed Central

    Lord, Janice M.

    2015-01-01

    The harsh climatic conditions and paucity of potential pollinators on Southern Ocean Islands (SOIs; latitude 46°S–55°S) lead to the expectation that anemophily or self-fertilization are the dominant modes of plant sexual reproduction. However, at least some species have showy inflorescences suggesting biotic pollination or dimorphic breeding systems necessitating cross-pollination. This study investigates whether anemophily and self-compatibility are common on SOIs, whether species or genera with these traits are more widespread or frequent at higher latitudes, and whether gender dimorphy is correlated with anemophily, as might occur if reliance on pollinators was a disadvantage. Of the 321 flowering plant species in the SOI region, 34.3 % possessed floral traits consistent with anemophily. Compatibility information was located for 94 potentially self-fertilizing species, of which 92.6 % were recorded as partially or fully self-compatible. Dioecy occurred in 7.1 % of species overall and up to 10.2 % of island floras, but has not clearly arisen in situ. Gynodioecy occurred in 3.4 % of species. The frequency of anemophily and gender dimorphy did not differ between the SOI flora and southern hemisphere temperate reference floras. At the species level, gender dimorphy was positively associated with fleshy fruit, but at the genus level it was associated with occurrence in New Zealand and a reduced regional distribution. Anemophily was more prevalent in genera occurring on subantarctic islands and the proportion of species with floral traits suggestive of biotic pollination was significantly higher on climatically milder, cool temperate islands. These results support the contention that reliance on biotic pollinators has constrained the distribution of species on SOIs; however, it is also clear that the reproductive biology of few SOI species has been studied in situ and many species likely employ a mixed mating strategy combining biotic pollination with self

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Seasonal evolution of the upper-ocean adjacent to the South Orkney Islands, Southern Ocean: Results from a “lazy biological mooring”

    NASA Astrophysics Data System (ADS)

    Meredith, Michael P.; Nicholls, Keith W.; Renfrew, Ian A.; Boehme, Lars; Biuw, Martin; Fedak, Mike

    2011-07-01

    A serendipitous >8-month time series of hydrographic properties was obtained from the vicinity of the South Orkney Islands, Southern Ocean, by tagging a southern elephant seal ( Mirounga leonina) on Signy Island with a Conductivity-Temperature-Depth/Satellite-Relay Data Logger (CTD-SRDL) in March 2007. Such a time series (including data from the austral autumn and winter) would have been extremely difficult to obtain via other means, and it illustrates with unprecedented temporal resolution the seasonal progression of upper-ocean water mass properties and stratification at this location. Sea ice production values of around 0.15-0.4 m month -1 for April to July were inferred from the progression of salinity, with significant levels still in September (around 0.2 m month -1). However, these values presume that advective processes have negligible effect on the salinity changes observed locally; this presumption is seen to be inappropriate in this case, and it is argued that the ice production rates inferred are better considered as "smeared averages" for the region of the northwestern Weddell Sea upstream from the South Orkneys. The impact of such advective effects is illustrated by contrasting the observed hydrographic series with the output of a one-dimensional model of the upper-ocean forced with local fluxes. It is found that the difference in magnitude between local (modelled) and regional (inferred) ice production is significant, with estimates differing by around a factor of two. A halo of markedly low sea ice concentration around the South Orkneys during the austral winter offers at least a partial explanation for this, since it enabled stronger atmosphere/ocean fluxes to persist and hence stronger ice production to prevail locally compared with the upstream region. The year of data collection was an El Niño year, and it is well-established that this phenomenon can impact strongly on the surface ocean and ice field in this sector of the Southern Ocean, thus

  8. Projected poleward shift of king penguins' (Aptenodytes patagonicus) foraging range at the Crozet Islands, southern Indian Ocean

    PubMed Central

    Péron, Clara; Weimerskirch, Henri; Bost, Charles-André

    2012-01-01

    Seabird populations of the Southern Ocean have been responding to climate change for the last three decades and demographic models suggest that projected warming will cause dramatic population changes over the next century. Shift in species distribution is likely to be one of the major possible adaptations to changing environmental conditions. Habitat models based on a unique long-term tracking dataset of king penguin (Aptenodytes patagonicus) breeding on the Crozet Islands (southern Indian Ocean) revealed that despite a significant influence of primary productivity and mesoscale activity, sea surface temperature consistently drove penguins' foraging distribution. According to climate models of the Intergovernmental Panel on Climate Change (IPCC), the projected warming of surface waters would lead to a gradual southward shift of the more profitable foraging zones, ranging from 25 km per decade for the B1 IPCC scenario to 40 km per decade for the A1B and A2 scenarios. As a consequence, distances travelled by incubating and brooding birds to reach optimal foraging zones associated with the polar front would double by 2100. Such a shift is far beyond the usual foraging range of king penguins breeding and would negatively affect the Crozet population on the long term, unless penguins develop alternative foraging strategies. PMID:22378808

  9. Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

    NASA Astrophysics Data System (ADS)

    Cavagna, A. J.; Fripiat, F.; Elskens, M.; Mangion, P.; Chirurgien, L.; Closset, I.; Lasbleiz, M.; Florez-Leiva, L.; Cardinal, D.; Leblanc, K.; Fernandez, C.; Lefèvre, D.; Oriol, L.; Blain, S.; Quéguiner, B.; Dehairs, F.

    2015-11-01

    Although the Southern Ocean is considered a high-nutrient, low-chlorophyll (HNLC) area, massive and recurrent blooms are observed over and downstream of the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N uptake (NO3- and NH4+), and nitrification rates were measured at eight stations in austral spring 2011 (October-November) during the KEOPS 2 cruise in the Kerguelen Plateau area. Natural iron fertilization stimulated primary production, with mixed layer integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m-2 d-1 and up to 0.31 d-1 respectively) compared to the HNLC reference site (12 mmol C m-2 d-1 and 0.06 d-1 respectively). Primary production was mainly sustained by nitrate uptake, with f ratios (corresponding to NO3--uptake / (NO3--uptake + NH4+-uptake)) lying at the upper end of the observations for the Southern Ocean (up to 0.9). We report high rates of nitrification (up to ~ 3 μmol N L-1 d-1, with ~ 90 % of them < 1 μmol N L-1 d-1) typically occurring below the euphotic zone, as classically observed in the global ocean. The specificity of the studied area is that at most of the stations, the euphotic layer was shallower than the mixed layer, implying that nitrifiers can efficiently compete with phytoplankton for the ammonium produced by remineralization at low-light intensities. Nitrate produced by nitrification in the mixed layer below the euphotic zone is easily supplied to the euphotic zone waters above, and nitrification sustained 70 ± 30 % of the nitrate uptake in the productive area above the Kerguelen Plateau. This complicates estimations of new production as potentially exportable production. We conclude that high productivity in deep mixing system stimulates the N cycle by increasing both assimilation and regeneration.

  10. Satellite remote sensing of the island mass effect on the Sub-Antarctic Kerguelen Plateau, Southern Ocean

    NASA Astrophysics Data System (ADS)

    Jena, Babula

    2016-04-01

    The presence of the Kerguelen Plateau and surrounding bathymetric features has a strong influence on the persistently eastward flowing Antarctic Circumpolar Current (ACC), resulting in enhancement of surface chlorophyll-a (Chl-a) in the downstream section of the plateau along the polar front (PF). The phenomenon is reported in this paper as the island mass effect (IME). Analysis of climatological Chl-a datasets from Aqua- Moderate Resolution Imaging Spectroradiometer (Aqua- MODIS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) shows distinct bloomy plumes (Chl-a>0.5 mg/m3) during austral spring-summer spreading as far as ~1800 km offshore up to 98°E along the downstream of the north Kerguelen Plateau (NKP). Similar IME phenomena is apparent over the south Kerguelen Plateau (SKP) with the phytoplankton bloom extending up to 96.7°E, along the southern boundary of ACC. The IME phenomena are pronounced only during austral spring-summer period with the availability of light and sedimentary source of iron from shallow plateau to sea surface that fertilizes the mixed layer. The NKP bloom peaks with a maximum areal extent of 1.315 million km2 during December, and the SKP bloom peaks during January with a time lag of one month. The blooms exist for at least 4 months of a year and are significant both as the base of regional food web and for regulating the biogeochemical cycle in the Southern Ocean. Even though the surface water above the Kerguelen Plateau is rich in Chl-a, an exception of an oligotrophic condition dominated between NKP and SKP due to apparent intrusion of iron limited low phytoplankton regime waters from the Enderby basin through the northeastward Fawn Trough Current.

  11. Satellite remote sensing of the island mass effect on the Sub-Antarctic Kerguelen Plateau, Southern Ocean

    NASA Astrophysics Data System (ADS)

    Jena, Babula

    2016-09-01

    The presence of the Kerguelen Plateau and surrounding bathymetric features has a strong influence on the persistently eastward flowing Antarctic Circumpolar Current (ACC), resulting in enhancement of surface chlorophyll-a (Chl- a) in the downstream section of the plateau along the polar front (PF). The phenomenon is reported in this paper as the island mass effect (IME). Analysis of climatological Chl- a datasets from Aqua- Moderate Resolution Imaging Spectroradiometer (Aqua- MODIS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) shows distinct bloomy plumes (Chl- a>0.5 mg/m3) during austral spring-summer spreading as far as ~1800 km offshore up to 98°E along the downstream of the north Kerguelen Plateau (NKP). Similar IME phenomena is apparent over the south Kerguelen Plateau (SKP) with the phytoplankton bloom extending up to 96.7°E, along the southern boundary of ACC. The IME phenomena are pronounced only during austral spring-summer period with the availability of light and sedimentary source of iron from shallow plateau to sea surface that fertilizes the mixed layer. The NKP bloom peaks with a maximum areal extent of 1.315 million km2 during December, and the SKP bloom peaks during January with a time lag of one month. The blooms exist for at least 4 months of a year and are significant both as the base of regional food web and for regulating the biogeochemical cycle in the Southern Ocean. Even though the surface water above the Kerguelen Plateau is rich in Chl- a, an exception of an oligotrophic condition dominated between NKP and SKP due to apparent intrusion of iron limited low phytoplankton regime waters from the Enderby basin through the northeastward Fawn Trough Current.

  12. Quantitative distribution and functional groups of intertidal macrofaunal assemblages in Fildes Peninsula, King George Island, South Shetland Islands, Southern Ocean.

    PubMed

    Liu, Xiaoshou; Wang, Lu; Li, Shuai; Huo, Yuanzi; He, Peimin; Zhang, Zhinan

    2015-10-15

    To evaluate spatial distribution pattern of intertidal macrofauna, quantitative investigation was performed in January to February, 2013 around Fildes Peninsula, King George Island, South Shetland Islands. A total of 34 species were identified, which were dominated by Mollusca, Annelida and Arthropoda. CLUSTER analysis showed that macrofaunal assemblages at sand-bottom sites belonged to one group, which was dominated by Lumbricillus sp. and Kidderia subquadrata. Macrofaunal assemblages at gravel-bottom sites were divided into three groups while Nacella concinna was the dominant species at most sites. The highest values of biomass and Shannon-Wiener diversity index were found in gravel sediment and the highest value of abundance was in sand sediment of eastern coast. In terms of functional group, detritivorous and planktophagous groups had the highest values of abundance and biomass, respectively. Correlation analysis showed that macrofaunal abundance and biomass had significant positive correlations with contents of sediment chlorophyll a, phaeophorbide and organic matter. PMID:26233302

  13. Mite dispersal among the Southern Ocean Islands and Antarctica before the last glacial maximum

    PubMed Central

    Mortimer, E.; Jansen van Vuuren, B.; Lee, J. E.; Marshall, D. J.; Convey, P.; Chown, S. L.

    2011-01-01

    It has long been maintained that the majority of terrestrial Antarctic species are relatively recent, post last glacial maximum, arrivals with perhaps a few microbial or protozoan taxa being substantially older. Recent studies have questioned this ‘recolonization hypothesis’, though the range of taxa examined has been limited. Here, we present the first large-scale study for mites, one of two dominant terrestrial arthropod groups in the region. Specifically, we provide a broad-scale molecular phylogeny of a biologically significant group of ameronothroid mites from across the maritime and sub-Antarctic regions. Applying different dating approaches, we show that divergences among the ameronothroid mite genera Podacarus, Alaskozetes and Halozetes significantly predate the Pleistocene and provide evidence of independent dispersals across the Antarctic Polar Front. Our data add to a growing body of evidence demonstrating that many taxa have survived glaciation of the Antarctic continent and the sub-Antarctic islands. Moreover, they also provide evidence of a relatively uncommon trend of dispersals from islands to continental mainlands. Within the ameronothroid mites, two distinct clades with specific habitat preferences (marine intertidal versus terrestrial/supralittoral) exist, supporting a model of within-habitat speciation rather than colonization from marine refugia to terrestrial habitats. The present results provide additional impetus for a search for terrestrial refugia in an area previously thought to have lacked ice-free ground during glacial maxima. PMID:20943685

  14. Methane at Ascension Island, southern tropical Atlantic Ocean: continuous ground measurement and vertical profiling above the Trade-Wind Inversion

    NASA Astrophysics Data System (ADS)

    Lowry, David; Brownlow, Rebecca; Fisher, Rebecca; Nisbet, Euan; Lanoisellé, Mathias; France, James; Thomas, Rick; Mackenzie, Rob; Richardson, Tom; Greatwood, Colin; Freer, Jim; Cain, Michelle; Warwick, Nicola; Pyle, John

    2015-04-01

    Methane mixing ratios have been rising rapidly worldwide since 2007. At Ascension Island (8oS in the equatorial Atlantic), a sustained rise has occurred. Prior to 2010, growth was comparable to other regions, but in 2010-11, during a strong la Nina event, the increase was 10ppb year-on-year. Reduced growth followed in 2011-12, but in 2012-13 strong growth resumed and continues. This rise has been accompanied by a shift to lighter δ13CCH4 values in 2010-11 in the equatorial tropics. The most likely cause of this shift is emissions from isotopically 'light' biological sources in the equatorial and savanna tropics. Ascension Island is in the Trade Wind belt of the tropical Atlantic, perfectly located to measure the South Atlantic marine boundary layer. The SE Trade Winds are almost invariant, derived from the deep South Atlantic and with little contact with Africa. However, above the Trade Wind Inversion (TWI) at about 1200-2000m asl, the air masses are very different, coming dominantly from tropical Africa and occasionally S. America. Depending on season, air above the TWI is sourced from the African southern savanna grasslands or the equatorial wetlands of Congo and Uganda, with inputs of air also from southern tropical S. America (Brazil, Paraguay, Bolivia). African methane sources are a major contributor to the global methane budget, but although local campaign studies have been made, African emissions are not well studied in bulk. In September 2014, an octocopter was used to retrieve air samples from heights up to 2700m asl on Ascension (see Thomas, R. et al, this volume). This allowed sampling through the marine boundary layer, across the TWI cloud layer, and into the mid-troposphere. Samples were collected in part-filled 5L Tedlar bags, which were analysed for CH4 concentration using Royal Holloway's Picarro 1301 CRDS system at the Met Office, Ascension. This has high precision and accuracy, with a 6-gas calibration suite. Bags were then analysed in the UK for

  15. The Last Termination in the South Indian Ocean: A unique terrestrial record from Kerguelen Islands (49°S) situated within the Southern Hemisphere westerly belt

    NASA Astrophysics Data System (ADS)

    Van der Putten, Nathalie; Verbruggen, Cyriel; Björck, Svante; Michel, Elisabeth; Disnar, Jean-Robert; Chapron, Emmanuel; Moine, Bertrand N.; de Beaulieu, Jacques-Louis

    2015-08-01

    The awareness of the significance of the Southern Ocean in the Earth's climate system has become increasingly obvious. The deglacial atmospheric CO2 rise during warming periods in Antarctica has been attributed to CO2 ventilation from the deep ocean caused by enhanced upwelling around the Antarctic Divergence. It has been hypothesized that, more intense Southern Hemisphere westerly winds aligned with the Antarctic Circumpolar Current due to a southward shift of the wind belt from its Last Glacial Maximum equator-ward position, are the main drivers. Reconstructions of past changes in atmospheric circulation in the Southern Hemisphere are still scarce and the overall picture is patchy with sometimes contradictory results. For obvious reasons, most terrestrial records originate from southern South America and New Zealand. Here we present a terrestrial record from the Indian sector of the Southern Ocean, from Kerguelen Islands located at 49°S. A peat record is investigated using a multi-proxy approach (pollen and plant macrofossils, magnetic susceptibility, XRF analyses, biogenic silica content, Rock-Eval6 analysis and humification degree). Peat accumulation starts at about 16,000 cal yr BP with relatively warm and dry conditions. The most prominent change in our proxy data occurs at 13,600 cal yr BP, when peat ponds were established on the peat surface, resulting in lacustrine-type deposits, as a result of very high humidity, and with proxies implying very windy conditions. Within chronological uncertainties, this onset coincides with the onset of the so-called Oceanic Cold Reversal, based on the deuterium excess data in the EPICA Dome C ice core record. Kerguelen Islands are located in the moisture source area of Dome C and a change in atmospheric circulation at that time could explain both records. Around 12,900 cal yr BP, at the end of the Antarctic Cold Reversal, pond/lake sediments give way to more peaty deposits, with proxies suggesting slightly drier

  16. Pteropods in Southern Ocean ecosystems

    NASA Astrophysics Data System (ADS)

    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 <5% to total zooplankton in the Lazarev Sea, but 15% (max = 93%) to macrozooplankton in the East Antarctic. In addition to regional density distributions we have synthesized data on vertical distributions, seasonal cycles, and inter-annual density variation. Trophically, gymnosome are specialist predators on thecosomes, while thecosomes are considered predominantly herbivorous, capturing food with a mucous web. The ingestion rates of L. retroversa australis are in the upper range for sub-Antarctic mesozooplankton (31.2-4196.9 ng pig ind -1 d -1), while those of L

  17. Southern Ocean eddy phenomenology

    NASA Astrophysics Data System (ADS)

    Frenger, I.; Münnich, M.; Gruber, N.; Knutti, R.

    2015-11-01

    Mesoscale eddies are ubiquitous features in the Southern Ocean, yet their phenomenology is not well quantified. To tackle this task, we use satellite observations of sea level anomalies and sea surface temperature (SST) as well as in situ temperature and salinity measurements from profiling floats. Over the period 1997-2010, we identified over a million mesoscale eddy instances and were able to track about 105 of them over 1 month or more. The Antarctic Circumpolar Current (ACC), the boundary current systems, and the regions where they interact are hot spots of eddy presence, representing also the birth places and graveyards of most eddies. These hot spots contrast strongly to areas shallower than about 2000 m, where mesoscale eddies are essentially absent, likely due to topographical steering. Anticyclones tend to dominate the southern subtropical gyres, and cyclones the northern flank of the ACC. Major causes of regional polarity dominance are larger formation numbers and lifespans, with a contribution of differential propagation pathways of long-lived eddies. Areas of dominance of one polarity are generally congruent with the same polarity being longer-lived, bigger, of larger amplitude, and more intense. Eddies extend down to at least 2000 m. In the ACC, eddies show near surface temperature and salinity maxima, whereas eddies in the subtropical areas generally have deeper anomaly maxima, presumably inherited from their origin in the boundary currents. The temperature and salinity signatures of the average eddy suggest that their tracer anomalies are a result of both trapping in the eddy core and stirring.

  18. First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia

    NASA Astrophysics Data System (ADS)

    Römer, M.; Torres, M.; Kasten, S.; Kuhn, G.; Graham, A. G. C.; Mau, S.; Little, C. T. S.; Linse, K.; Pape, T.; Geprägs, P.; Fischer, D.; Wintersteller, P.; Marcon, Y.; Rethemeyer, J.; Bohrmann, G.

    2014-10-01

    An extensive submarine cold-seep area was discovered on the northern shelf of South Georgia during R/V Polarstern cruise ANT-XXIX/4 in spring 2013. Hydroacoustic surveys documented the presence of 133 gas bubble emissions, which were restricted to glacially-formed fjords and troughs. Video-based sea floor observations confirmed the sea floor origin of the gas emissions and spatially related microbial mats. Effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near-bottom waters. Stable carbon isotopic signatures pointed to a predominant microbial methane formation, presumably based on high organic matter sedimentation in this region. Although known from many continental margins in the world's oceans, this is the first report of an active area of methane seepage in the Southern Ocean. Our finding of substantial methane emission related to a trough and fjord system, a topographical setting that exists commonly in glacially-affected areas, opens up the possibility that methane seepage is a more widespread phenomenon in polar and sub-polar regions than previously thought.

  19. A 50 year comparison of ambient ocean noise near San Clemente Island: a bathymetrically complex coastal region off Southern California.

    PubMed

    McDonald, Mark A; Hildebrand, John A; Wiggins, Sean M; Ross, Donald

    2008-10-01

    Repeated ocean ambient noise measurements at a shallow water (110 m) site near San Clemente Island reveal little increase in noise levels in the absence of local ships. Navy reports document ambient noise levels at this site in 1958-1959 and 1963-1964 and a seafloor recorder documents noise during 2005-2006. When noise from local ships was excluded from the 2005-2006 recordings, median sound levels were essentially the same as were observed in 1958 and 1963. Local ship noise, however, was present in 31% of the recordings in 1963 but was present in 89% of the recordings in 2005-2006. Median levels including local ships are 6-9 dB higher than median levels chosen from times when local ship noise was absent. Biological sounds and the sound of wind driven waves controlled ambient noise levels in the absence of local ships. The median noise levels at this site are low for an open water site due to the poor acoustic propagation and low average wind speeds. The quiet nature of this site in the absence of local ships allows correlation of wind speed to wave noise across the 10-220 Hz spectral band of this study. PMID:19062838

  20. The Southern Ocean CIRCLE initiative

    NASA Astrophysics Data System (ADS)

    Murphy, E. J.; Ellis-Evans, J. C.

    2003-04-01

    The circumpolar Southern Ocean is the principal ocean connection between the Atlantic, Pacific and Indian Oceans, and exerts a profound influence on world climate through ocean circulation and its major role in the global carbon cycle. It is a major repository of biodiversity and also the only ocean system where significant marine living resources are yet to be fully exploited. However, this key component of the Earth System is still poorly understood, in part due to the logistical problems of a harsh, remote location and the circumpolar nature of the environment. Circumpolar patterns of variability have now been recognized and the current challenge is to understand how, at a circumpolar scale, this variability is generated, its impact on the regional biogeochemical cycles, its interaction with ecosystem processes and the links to global scale processes. Many of these scientific issues can only be addressed by Southern Ocean scale studies, and although a range of national and international research programmes are already targeting particular aspects, the research effort is largely uncoordinated. The European Polar Board is sponsoring a pan-European initiative (Southern Ocean CIRCLE) to coordinate the currently disparate Southern Ocean research effort and this initiative aims to address climate variability, biogeochemical cycling and ecosystem dynamics with particular reference to the links between these aspects in the circumpolar Southern Ocean. This poster outlines the development of the SO CIRCLE initiative, the major areas of science and proposals for implementation. It also outlines how SO CIRCLE will link to other programmes with a Southern Ocean component (e.g. CLIVAR, CliC, GLOBEC, SOLAS). A key aspect of the initiative will be to coordinate European scientific effort in the Southern Ocean with that of the wider international community.

  1. Southern Ocean Iron Experiment (SOFex)

    SciTech Connect

    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 Southern

  2. A high resolution seismic reflection image for the oceanic LAB (Lithosphere-Asthenosphere Boundary), beneath southern North Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Stern, T. A.; Henrys, S. A.; Okaya, D. A.; Savage, M. K.; Sato, H.; Iwasaki, T.; Louie, J. N.; Lamb, S. H.

    2014-12-01

    We present the first high-resolution, multichannel, seismic-reflection image for the base of an oceanic plate. Our image is based on an 85 km-long, ~ 900 station deployment across the lower North Island of New Zealand. 12 x 500 kg dynamite shots were used as seismic sources. Strong reflections at a two way travel time of 9-12 s define the top of the plate that dips to the NW at ~ 12-15 degrees. Between 27-32 s we identify a pair of reflections on some shot gathers that are interpreted to come from a reflection 90-100 km deep, that dips to the NW at 15 degrees. We interpret the reflection pair as marking a Lithosphere-Asthenosphere Boundary (LAB) zone at the base of the Pacific plate. Using all 12 shots we made a CDP-stacked image (maximum fold = 15) that shows the LAB as a double event (2-3 s apart) dipping roughly parallel to the top of the plate and Benioff zone. Shot quality varies but the highest frequencies we record from the base of the plate are ~ 18 Hz, suggesting a boundary zone < 1 km thick. Seismic amplitude attributes, calibrated to the reflection from the top of the plate, indicate P-wave speed drops off at least 8% across the LAB boundary. The double reflection at the LAB is interpreted to be a 10 km-thick layer of low seismic wave speed. Because it is so sharp it cannot be a thermal boundary and must represent some form of mechanical change. Previous attempts to explain the abruptness of seismic wave speed changes at the LAB have appealed to layered zones of ponded melt, or anelastic relaxation due to water accumulating beneath the LAB. Both mechanisms may explain our observations and both would point to low viscosity below the LAB. However, the fact we see a ~ 10 km thick channel, with strong acoustic impedances each side of the channel, suggests a shear zone where plate motion ( ~ 9 cm/y in hotspot reference frame) is taken up and strain rates of ~3 x 10-13 s-1 are generated. This interpreted, low wave-speed, low-viscosity, shear zone appears to be

  3. Is heterostyly rare on oceanic islands?

    PubMed Central

    Watanabe, Kenta; Sugawara, Takashi

    2015-01-01

    Heterostyly has been considered rare or absent on oceanic islands. However, there has been no comprehensive review on this issue. Is heterostyly truly rare on oceanic islands? What makes heterostyly rare on such islands? To answer these questions, we review the reproductive studies on heterostyly on oceanic islands, with special emphasis on the heterostylous genus Psychotria in the Pacific Ocean as a model system. Overall, not many reproductive studies have been performed on heterostylous species on oceanic islands. In Hawaiian Psychotria, all 11 species are thought to have evolved dioecy from distyly. In the West Pacific, three species on the oceanic Bonin and Lanyu Islands are distylous (Psychotria homalosperma, P. boninensis and P. cephalophora), whereas three species on the continental Ryukyu Islands show various breeding systems, such as distyly (P. serpens), dioecy (P. rubra) and monoecy (P. manillensis). On some other Pacific oceanic islands, possibilities of monomorphy have been reported. For many Psychotria species, breeding systems are unknown, although recent studies indicate that heterostylous species may occur on some oceanic islands. A shift from heterostyly to other sexual systems may occur on some oceanic islands. This tendency may also contribute to the rarity of heterostyly, in addition to the difficulty in colonization/autochthonous evolution of heterostylous species on oceanic islands. Further investigation of reproductive systems of Psychotria on oceanic islands using robust phylogenetic frameworks would provide new insights into plant reproduction on oceanic islands. PMID:26199401

  4. Synthesizing knowledge of ocean islands

    NASA Astrophysics Data System (ADS)

    Jefferson, Anne J.; Lees, Jonathan M.; McClinton, Tim

    2011-11-01

    AGU Chapman Conference on the Galápagos as a Laboratory for the Earth Sciences; Puerto Ayora, Galápagos, Ecuador, 25-30 July 2011 An inspiration for Darwin's theory of evolution, the Galápagos Islands and surrounding waters are a natural laboratory for a wide range of Earth science topics. The Galápagos are perfectly situated for geophysical and geochemical investigations of deep-Earth processes at a hot spot, and proximity to a spreading center allows exploration of hot spot-ridge interactions. Several highly active volcanoes show rapid deformation facilitating investigation of melt transport paths and volcanic structure. The islands exhibit a range of ages, eruptive styles, and climatic zones that allow analysis of hydrogeologic and geomorphic processes. The Galápagos Islands are a World Heritage Site and are an ideal setting for developing an integrated biological and geological understanding of ocean island evolution.

  5. Diversity of Dicotyledenous-Infecting Geminiviruses and Their Associated DNA Molecules in Southern Africa, Including the South-West Indian Ocean Islands

    PubMed Central

    Rey, Marie E. C.; Ndunguru, Joseph; Berrie, Leigh C.; Paximadis, Maria; Berry, Shaun; Cossa, Nurbibi; Nuaila, Valter N.; Mabasa, Ken G.; Abraham, Natasha; Rybicki, Edward P.; Martin, Darren; Pietersen, Gerhard; Esterhuizen, Lindy L.

    2012-01-01

    The family Geminiviridae comprises a group of plant-infecting circular ssDNA viruses that severely constrain agricultural production throughout the temperate regions of the world, and are a particularly serious threat to food security in sub-Saharan Africa. While geminiviruses exhibit considerable diversity in terms of their nucleotide sequences, genome structures, host ranges and insect vectors, the best characterised and economically most important of these viruses are those in the genus Begomovirus. Whereas begomoviruses are generally considered to be either monopartite (one ssDNA component) or bipartite (two circular ssDNA components called DNA-A and DNA-B), many apparently monopartite begomoviruses are associated with additional subviral ssDNA satellite components, called alpha- (DNA-αs) or betasatellites (DNA-βs). Additionally, subgenomic molecules, also known as defective interfering (DIs) DNAs that are usually derived from the parent helper virus through deletions of parts of its genome, are also associated with bipartite and monopartite begomoviruses. The past three decades have witnessed the emergence and diversification of various new begomoviral species and associated DI DNAs, in southern Africa, East Africa, and proximal Indian Ocean islands, which today threaten important vegetable and commercial crops such as, tobacco, cassava, tomato, sweet potato, and beans. This review aims to describe what is known about these viruses and their impacts on sustainable production in this sensitive region of the world. PMID:23170182

  6. Islands of Education: Schooling, Civil War and the Southern Sudanese (1983-2004)

    ERIC Educational Resources Information Center

    Sommers, Marc

    2005-01-01

    Victims of warfare, famine, slavery, and isolation, the Southern Sudanese are one of the most undereducated populations in the world. Since the inception of formal education in southern Sudan a century ago, schooling has largely consisted of island-like entities surrounded by oceans of educational emptiness. Islands of Education is the first book…

  7. Bats of the Western Indian Ocean Islands

    PubMed Central

    O'Brien, John

    2011-01-01

    Simple Summary The purpose of this paper is to review the literature pertaining to the bat faunas of the western Indian Ocean islands, particularly in light of the identification of many new species on Madagascar and the taxonomic reassignment of others, and to summarise details of their general biology, feeding ecology, reproduction and conservation. Abstract The natural colonisation of many remote oceanic islands by bats, including those of the western Indian Ocean, has been facilitated by their unique capability among mammals for powered flight. In the western Indian Ocean region, only the Malagasy islands of Madagascar and the Comoros archipelago have been naturally colonised by non-volant mammals. Despite their greater potential for inter-island dispersal, and thus gene transfer, endemicity of Chiroptera in the western Indian Ocean islands is high. Given their vulnerability to stochastic and anthropogenic disturbances, greater focus needs to be placed on investigating the demographic and ecological history of bats on Western Indian Ocean islands to safeguard not only their future, but also the ecosystem functioning on these islands, for which they are undoubtedly such an integral part. Here, I summarise the taxonomic and life history information available on bats from Western Indian Ocean islands and highlight knowledge gaps and conservation issues that threaten the continued persistence of some species. PMID:26486500

  8. Ceilometer measurements in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    McDonald, Adrian; Alexander, Simon; French, John; Harvey, Mike; Ichoja, Andrew; Klekociuk, Andrew; Plank, Graeme; Katurji, Marwan

    2016-04-01

    Current climate models display a consistent deficit of reflected shortwave radiation over the Southern Ocean which is mainly due to the poor representation of clouds. Recent work has also shown that reanalysis also perform poorly relative to satellite observations in terms of cloud fraction. In particular, satellite observations have shown that low-level clouds (with tops below 3 km) are ubiquitous over the Southern Ocean. But, most satellite instruments, even the current generation of active satellite instruments, have difficulties in sampling low level clouds. As part of the New Zealand Deep South challenge project focussed on improving the representation of clouds in the Southern Ocean, we have begun to deploy autonomous instruments on 'ships of opportunity'. This study discusses measurements from a Väisälä CL51 laser ceilometer and ancillary instruments on the first two research voyages in the Southern Ocean and initial results. The route of the first voyage covers a return trip from Wellington (New Zealand) to Terra Nova Bay (Antarctica) onboard the R/V Tangaroa and occurred in January to mid-February 2015. The second deployment is onboard the Aurora Australis Australian Antarctic Division supply ship and began in October 2015 and is planned to finish at Macquarie Island in March 2016. The sampling provided by the ships route allows the ceilometer measurements of the height of the cloud base in a region where limited data apart from, potentially biased, satellite measurements of low-level cloud exist. Analysis of the boundary layer height derived from the ceilometer is also presented. The climatological structure derived from the ceilometer measurements is first detailed. We then compare these measurements with satellite and ground-based observations. We then examine variations in these measurements relative to their meteorological context. Details of plans for future voyages are also detailed. We will also present a preliminary analysis of a case study of

  9. Rates of species introduction to a remote oceanic island.

    PubMed Central

    Gaston, Kevin J; Jones, Alex G; Hänel, Christine; Chown, Steven L

    2003-01-01

    The introduction of species to areas beyond the limits of their natural distributions has a major homogenizing influence, making previously distinct biotas more similar. The scale of introductions has frequently been commented on, but their rate and spatial pervasiveness have been less well quantified. Here, we report the findings of a detailed study of pterygote insect introductions to Gough Island, one of the most remote and supposedly pristine temperate oceanic islands, and estimate the rate at which introduced species have successfully established. Out of 99 species recorded from Gough Island, 71 are established introductions, the highest proportion documented for any Southern Ocean island. Estimating a total of approximately 233 landings on Gough Island since first human landfall, this equates to one successful establishment for every three to four landings. Generalizations drawn from other areas suggest that this may be only one-tenth of the number of pterygote species that have arrived at the island, implying that most landings may lead to the arrival of at least one alien. These rates of introduction of new species are estimated to be two to three orders of magnitude greater than background levels for Gough Island, an increase comparable to that estimated for global species extinctions (many of which occur on islands) as a consequence of human activities. PMID:12803900

  10. The Southern Ocean: Source and sink?

    NASA Astrophysics Data System (ADS)

    Strugnell, J. M.; Cherel, Y.; Cooke, I. R.; Gleadall, I. G.; Hochberg, F. G.; Ibáñez, C. M.; Jorgensen, E.; Laptikhovsky, V. V.; Linse, K.; Norman, M.; Vecchione, M.; Voight, J. R.; Allcock, A. L.

    2011-03-01

    Many members of the benthic fauna of the Antarctic continental shelf share close phylogenetic relationships to the deep-sea fauna adjacent to Antarctica and in other ocean basins. It has been suggested that connections between the Southern Ocean and the deep sea have been facilitated by the presence of a deep Antarctic continental shelf coupled with submerging Antarctic bottom water and emerging circumpolar deep water. These conditions may have allowed 'polar submergence', whereby shallow Southern Ocean fauna have colonised the deep sea and 'polar emergence', whereby deep-sea fauna colonised the shallow Southern Ocean. A recent molecular study showed that a lineage of deep-sea and Southern Ocean octopuses with a uniserial sucker arrangement on their arms appear to have arisen via polar submergence. A distantly related clade of octopuses with a biserial sucker arrangement on their arms (historically placed in the genus Benthoctopus) is also present in the deep-sea basins of the world and the Southern Ocean. To date their evolutionary history has not been examined. The present study investigated the origins of this group using 3133 base pairs (bp) of nucleotide data from five mitochondrial genes (12S rRNA, 16S rRNA, cytochrome c oxidase subunit I, cytochrome c oxidase subunit III, cytochrome b) and the nuclear gene rhodopsin from at least 18 species (and 7 outgroup taxa). Bayesian relaxed clock analyses showed that Benthoctopus species with a high-latitude distribution in the Southern Hemisphere represent a paraphyletic group comprised of three independent clades. The results suggest that the Benthoctopus clade originated in relatively shallow Northern Hemisphere waters. Benthoctopus species distributed in the Southern Ocean are representative of polar emergence and occur at shallower depths than non-polar Benthoctopus species.

  11. Bacterial biodiversity in deep-sea sediments from two regions of contrasting surface water productivity near the Crozet Islands, Southern Ocean

    NASA Astrophysics Data System (ADS)

    Jamieson, R. E.; Heywood, J. L.; Rogers, A. D.; Billett, D. S. M.; Pearce, D. A.

    2013-05-01

    The relationship between surface-derived particulate organic matter (POM) and deep-sea sediment bacterial abundance, community structure and composition was investigated in two different sediment layers from two zones of contrasting surface water productivity in the southern Indian Ocean. Bacterial sediment communities from high chlorophyll (HC) and low chlorophyll (LC) sites were characterized and compared using direct counts, clone library construction, denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH). Of the 1566 bacterial clones generated from the sediment communities, 1010 matched published 16S rDNA sequences at ≥97% identity. A comparison of surface sediment clone libraries showed that at least one third of all identified operational taxonomic units (OTUs) were common to both HC and LC sites. DGGE community profiles were consistent (82% similar) and evenness of the major phylogenetic groups was 96% similar between surface sediment communities, where gamma- and alpha-Proteobacteria were dominant. Sediment communities shared similarly high biodiversity, while species richness was marginally higher at the LC site. Intra-site shifts in bacterial abundance and composition were observed with increasing sediment depth. Despite the differences in organic matter input between sites, the consistency observed between HC and LC sediment communities pointed to (1) the extent of remineralisation by mega and meio-fauna as a potential factor affecting the quantity and quality of POM available to sediment bacteria, (2) sampling during the early 'nutrient assimilation phase' of the bacterial response to freshly deposited POM or (3) that the action of bacteria in the water column could affect the quantity and quality of POM available to sediment bacteria. Although factors other than these may explain the observed similarities, this first comparison of such deep-sea sediment communities in relation to surface-derived productivity may

  12. Alpheid shrimps (Decapoda: Caridea) of the Trindade & Martin Vaz Archipelago, off Brazil, with new records, description of a new species of Synalpheus and remarks on zoogeographical patterns in the oceanic islands of the tropical southern Atlantic.

    PubMed

    Anker, Arthur; Tavares, Marcos

    2016-01-01

    The present study deals with shrimps of the family Alpheidae collected in the shallow waters around the remote Trindade & Martin Vaz Archipelago, situated 1200 km off the coast of Espírito Santo, Brazil. A few additional samples came from dredges on top of the seamounts of the Vitória-Trindade Seamount Chain. A total of 23 species in eight genera are reported, the vast majority representing new records for the area. One species is described as new, Synalpheus trinitatis sp. nov., based on the type material from Trindade Island. The new species clearly belongs to the Synalpheus brooksi Coutière, 1909 species complex, differing from all its other members by at least two morphological features. Four species represent new records for Brazil and the southwestern Atlantic: Alpheopsis aequalis Coutière, 1897 sensu lato, Alpheopsis chalciope de Man, 1910 sensu lato, Alpheus crockeri (Armstrong, 1941) and Prionalpheus gomezi Martínez-Iglesias & Carvacho, 1991; the two species of Alpheopsis are recorded from the Atlantic Ocean for the first time. The colour pattern of the recently described Alpheus rudolphi Almeida & Anker, 2011, a species endemic to Brazil, is shown for the first time and compared to the colour patterns of the four closely related species of the A. armatus Rathbun, 1901 complex from the Caribbean-Florida region. A brief zoogeographical analysis of the alpheid fauna of the oceanic islands of the tropical southern Atlantic (Trindade & Martin Vaz, Fernando de Noronha, Atol das Rocas, São Pedro & São Paulo, Ascension, Saint Helena, Cape Verde, São Tomé & Príncipe) is also provided. PMID:27470751

  13. Southern Ocean Eddies as Weather Makers

    NASA Astrophysics Data System (ADS)

    Frenger, Ivy; Byrne, David; Gruber, Nicolas; Knutti, Reto; Münnich, Matthias; Papritz, Lukas

    2013-04-01

    Several hundred mesoscale eddies populate the Southern Ocean south of 30°S at any time, however, little is known about their effect on the overlying atmosphere. As these eddies feature sea surface temperature (SST) anomalies one can expect them to play a role in the coupling of the atmosphere and the ocean. Here we show based on satellite observations of about 600,000 eddies occurring between 1997 and 2010, that these ocean eddies significantly alter near surface wind, cloud properties and rainfall by several percent. Relative to the atmospheric variability, the magnitude of the anomalies related to ocean eddies represents ±13-15 % (wind, cloud fraction), ±6-10 % (cloud water content) and ±2-6 % (rain). This impact on the atmosphere is striking given the fact that oceanic eddies constitute non-stationary SST fronts of moderate size relative to the much larger atmospheric low pressure systems which are constantly passing by at these latitudes. The spatial pattern of these changes is consistent with a mechanism labeled downward momentum mechanism in which the SST anomalies related to eddies modify the stability and thus turbulence of the atmospheric boundary layer. We will investigate the mechanisms and impact of the atmospheric modifications associated with ocean eddies in a regional high-resolution coupled atmosphere-ocean model (COSMO-ROMS) over the Southern Ocean.

  14. Indian Ocean, Maldive Islands, India, and Sri Lanka

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This scene shows a fantastic view of the Indian Ocean with oblique views of the southern portion of India, Palk Strait and Sri Lanka (1.5N, 77.5E). The bottom portion of the photo shows the complete chain of the Maldive Islands. This is a rare detailed view of the atolls that form the Maldives. The dusty atmosphere over India is clearly visible as it extends towards the Bay of Bengal but the atmosphere over the Maldives appears to be clear at this time.

  15. Southern Ocean biological impacts on global ocean oxygen

    NASA Astrophysics Data System (ADS)

    Keller, David P.; Kriest, Iris; Koeve, Wolfgang; Oschlies, Andreas

    2016-06-01

    Southern Ocean (SO) physical and biological processes are known to have a large impact on global biogeochemistry. However, the role that SO biology plays in determining ocean oxygen concentrations is not completely understood. These dynamics are investigated here by shutting off SO biology in two marine biogeochemical models. The results suggest that SO biological processes reduce the ocean's oxygen content, mainly in the deep ocean, by 14 to 19%. However, since these processes also trap nutrients that would otherwise be transported northward to fuel productivity and subsequent organic matter export, consumption, and the accompanying oxygen consumption in midlatitude to low-latitude waters, SO biology helps to maintain higher oxygen concentrations in these subsurface waters. Thereby, SO biology can influence the size of the tropical oxygen minimum zones. As a result of ocean circulation the link between SO biological processes and remote oxygen changes operates on decadal to centennial time scales.

  16. Gentle Africanized bees on an oceanic island

    PubMed Central

    Rivera-Marchand, Bert; Oskay, Devrim; Giray, Tugrul

    2012-01-01

    Oceanic islands have reduced resources and natural enemies and potentially affect life history traits of arriving organisms. Among the most spectacular invasions in the Western hemisphere is that of the Africanized honeybee. We hypothesized that in the oceanic island Puerto Rico, Africanized bees will exhibit differences from the mainland population such as for defensiveness and other linked traits. We evaluated the extent of Africanization through three typical Africanized traits: wing size, defensive behavior, and resistance to Varroa destructor mites. All sampled colonies were Africanized by maternal descent, with over 65% presence of European alleles at the S-3 nuclear locus. In two assays evaluating defense, Puerto Rican bees showed low defensiveness similar to European bees. In morphology and resistance to mites, Africanized bees from Puerto Rico are similar to other Africanized bees. In behavioral assays on mechanisms of resistance to Varroa, we directly observed that Puerto Rican Africanized bees groomed-off and bit the mites as been observed in other studies. In no other location, Africanized bees have reduced defensiveness while retaining typical traits such as wing size and mite resistance. This mosaic of traits that has resulted during the invasion of an oceanic island has implications for behavior, evolution, and agriculture. PMID:23144660

  17. Deglacial Atlantic Radiocarbon: A Southern Ocean Perspective

    NASA Astrophysics Data System (ADS)

    Robinson, L. F.; Burke, A.; Adkins, J. F.; Chen, T.; Spooner, P.

    2014-12-01

    It is widely accepted that the Southern Ocean is an important component of the climate system, acting as a key site for carbon and heat exchange between the atmosphere and oceans. The deglaciation with its associated millenial climate changes is a key time period for testing the mechanisms behind these exchanges. Ascertaining the precise timing of these events is a challenge given complications from variable and largely unconstrained reservoir ages, dissolution of carbonate hard parts and sediment redistribution by strong currents. Nevertheless improvements to our understanding of Southern Ocean dynamics in the past requires accurately-dated proxy records that can be embedded in GCM models. Radiocarbon measured in deep-sea corals offers just such an archive and proxy. Using the skeletons of deep-sea corals we are now able to reconstruct aspects of the history of three distinct water masses in the Drake Passage on a precise timescale, allowing direct comparison to U-series dated speleothem terrestrial records and polar ice cores. We present here a new deglacial radiocarbon record from the Drake Passage which more than doubles the resolution of published records. We focus on the deglacial, as well as providing insights from the contrasting period leading up to the LGM. Together with new data from far-field sites we interpret our results as evidence for a Southern Ocean control on atmospheric carbon dioxide and radiocarbon evolution during the deglaciation, and a northern hemisphere control during the run up to the LGM.

  18. Primary production in Southern Ocean waters

    NASA Astrophysics Data System (ADS)

    Arrigo, Kevin R.; Worthen, Denise; Schnell, Anthony; Lizotte, Michael P.

    1998-07-01

    The Southern Ocean forms a link between major ocean basins, is the site of deep and intermediate water ventilation, and is one of the few areas where macronutrients are underutilized by phytoplankton. Paradoxically, prior estimates of annual primary production are insufficient to support the Antarctic food web. Here we present results from a primary production algorithm based upon monthly climatological phytoplankton pigment concentrations from the coastal zone color scanner (CZCS). Phytoplankton production was forced using monthly temperature profiles and a radiative transfer model that computed changes in photosynthetically usable radiation at each CZCS pixel location. Average daily productivity (g C m-2 d-1) and total monthly production (Tg C month-1) were calculated for each of five geographic sectors (defined by longitude) and three ecological provinces (defined by sea ice coverage and bathymetry as the pelagic province, the marginal ice zone, and the shelf). Annual primary production in the Southern Ocean (south of 50°S) was calculated to be 4414 Tg C yr-1, 4-5 times higher than previous estimates made from in situ data. Primary production was greatest in the month of December (816 Tg C month-1) and in the pelagic province (contributing 88.6% of the annual primary production). Because of their small size the marginal ice zone (MIZ) and the shelf contributed only 9.5% and 1.8%, respectively, despite exhibiting higher daily production rates. The Ross Sea was the most productive region, accounting for 28% of annual production. The fourfold increase in the estimate of primary production for the Southern Ocean likely makes the notion of an "Antarctic paradox" (primary production insufficient to support the populations of Southern Ocean grazers, including krill, copepods, microzooplankton, etc.) obsolete.

  19. The Future of Southern Ocean Observing Systems

    NASA Astrophysics Data System (ADS)

    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

  20. Bicarbonate uptake by Southern Ocean phytoplankton

    NASA Astrophysics Data System (ADS)

    Cassar, Nicolas; Laws, Edward A.; Bidigare, Robert R.; Popp, Brian N.

    2004-06-01

    Marine phytoplankton have the potential to significantly buffer future increases in atmospheric carbon dioxide levels. However, in order for CO2 fertilization to have an effect on carbon sequestration to the deep ocean, the increase in dissolved CO2 must stimulate primary productivity; that is, marine phototrophs must be CO2 limited [, 1993]. Estimation of the extent of bicarbonate (HCO3-) uptake in the oceans is therefore required to determine whether the anthropogenic carbon sources will enhance carbon flux to the deep ocean. Using short-term 14CO2-disequilibrium experiments during the Southern Ocean Iron Experiment (SOFeX), we show that HCO3- uptake by Southern Ocean phytoplankton is significant. Since the majority of dissolved inorganic carbon (DIC) in the ocean is in the form of bicarbonate, the biological pump may therefore be insensitive to anthropogenic CO2. Approximately half of the DIC uptake observed was attributable to direct HCO3- uptake, the other half being direct CO2 uptake mediated either by passive diffusion or active uptake mechanisms. The increase in growth rates and decrease in CO2 concentration associated with the iron fertilization did not trigger any noticeable changes in the mode of DIC acquisition, indicating that under most environmental conditions the carbon concentrating mechanism (CCM) is constitutive. A low-CO2 treatment induced an increase in uptake of CO2, which we attributed to increased extracellular carbonic anhydrase activity, at the expense of direct HCO3- transport across the plasmalemma. Isotopic disequilibrium experimental results are consistent with Southern Ocean carbon stable isotope fractionation data from this and other studies. Although iron fertilization has been shown to significantly enhance phytoplankton growth and may potentially increase carbon flux to the deep ocean, an important source of the inorganic carbon taken up by phytoplankton in this study was HCO3-, whose concentration is negligibly affected by the

  1. Cadmium isotope variations in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Xue, Zichen; Rehkämper, Mark; Horner, Tristan J.; Abouchami, Wafa; Middag, Rob; van de Flierd, Tina; de Baar, Hein J. W.

    2013-11-01

    Cadmium concentrations and isotope compositions were determined for 47 seawater samples from the high nutrient low chlorophyll (HNLC) zone of the Atlantic sector of the Southern Ocean. The samples include 13 surface waters from a transect of the Weddell Gyre and 3 depth profiles from the Weddell Sea and Drake Passage. The Southern Ocean mixed layer samples from this study and Abouchami et al. (2011) define a clear but broad ‘HNLC trend’ in a plot of εCd114/110 versus [Cd], which is primarily a consequence of isotopic fractionation associated with biological uptake (εCd114/110 is the deviation of the 114Cd/110Cd ratio of a sample from NIST SRM 3108 Cd in parts per 10,000). The trend is especially apparent in comparison to the large range of values shown by a global set of seawater Cd data for shallow depths. The Southern Ocean samples are also distinguished by their relatively high Cd concentrations (typically 0.2 to 0.6 nmol/kg) and moderately fractionated εCd114/110 (generally between +4 and +8) that reflect the limited biological productivity of this region. Detailed assessment reveals fine structure within the ‘HNLC trend’, which may record differences in the biological fractionation factor, different scenarios of closed and open system isotope fractionation, and/or distinct source water compositions. Southern Ocean seawater from depths ⩾1000 m has an average εCd114/110 of +2.5±0.2 (2se, n=16), and together with previous results this establishes a relatively constant εCd114/110 value of +3.0±0.3 (2se, n=27) for global deep waters. Significant isotopic variability was observed at intermediate depths in the Southern Ocean. Seawater from 200 m to 400 m in Weddell Sea has high Cd concentrations and εCd114/110 as low as +1, presumably due to remineralization of Cd from biomass that records incomplete nutrient utilization. Antarctic Intermediate Water, which was sampled at 150 to 750 m depth in the Drake Passage, features a distinct Cd isotope

  2. Large-amplitude mesospheric response to an orographic wave generated over the Southern Ocean Auckland Islands (50.7°S) during the DEEPWAVE project

    NASA Astrophysics Data System (ADS)

    Pautet, P.-D.; Taylor, M. J.; Fritts, D. C.; Bossert, K.; Williams, B. P.; Broutman, D.; Ma, J.; Eckermann, S. D.; Doyle, J. D.

    2016-02-01

    The Deep Propagating Gravity Wave Experiment (DEEPWAVE) project was conducted over New Zealand and the surrounding regions during June and July 2014, to more fully understand the generation, propagation, and effects of atmospheric gravity waves. A large suite of instruments collected data from the ground to the upper atmosphere (~100 km), with several new remote-sensing instruments operating on board the NSF Gulfstream V (GV) research aircraft, which was the central measurement platform of the project. On 14 July, during one of the research flights (research flight 23), a spectacular event was observed as the GV flew in the lee of the sub-Antarctic Auckland Islands (50.7°S). An apparent "ship wave" pattern was imaged in the OH layer (at ~83.5 km) by the Utah State University Advanced Mesospheric Temperature Mapper and evolved significantly over four successive passes spanning more than 4 h. The waves were associated with orographic forcing generated by relatively strong (15-20 m/s) near-surface wind flowing over the rugged island topography. The mountain wave had an amplitude T' ~ 10 K, a dominant horizontal wavelength ~40 km, achieved a momentum flux exceeding 300 m2 s-2, and eventually exhibited instability and breaking at the OH altitude. This case of deep mountain wave propagation demonstrates the potential for strong responses in the mesosphere arising from a small source under suitable propagation conditions and suggests that such cases may be more common than previously believed.

  3. Southern Ocean Response to NADW Changes

    NASA Technical Reports Server (NTRS)

    Rind, David; Schmidt, G.; Russell, G.; deMenocal, P.; Hansen, James E. (Technical Monitor)

    2000-01-01

    The possibility of North Atlantic Deep Water (NADW) changes in both past and future climates has raised the issue of how the Southern Ocean would respond. Recent experiments with the GISS coupled atmosphere-ocean model have shown that a "bipolar see-saw" between NADW production and Antarctic Bottom Water (AABW) production in the Weddell Sea can occur in conjunction with freshening of the North Atlantic. However, this effect operates not through a slow ocean response but via a rapid atmospheric mechanism. As NADW reduces, colder temperatures in the North Atlantic, and Northern Hemisphere in general, are associated with higher surface pressure (increased atmospheric mass). Reduced mass in the Southern Hemisphere occurs in response, with lower pressure over the South Pole (an EOF #1 effect, the "high phase" of the Antarctic Oscillation).The lower pressure is associated with stronger west winds that generate an intensified Antarctic Circumpolar Current (ACC), which leads to longitudinal heat divergence in the South Atlantic (and heat convergence in the Southern Indian Ocean). Colder temperatures in the Weddell Sea region lead to sea ice growth, increased salinity and surface water density, and greater Weddell Sea Bottom Water production. Increased poleward transport of heat occurs in the South Atlantic in conjunction with increased bottom water production, but its convergence at high latitudes is not sufficient to offset the longitudinal heat divergence due to the intensified ACC. The colder temperatures at high latitudes in the South Atlantic increase the latitudinal temperature gradient, baroclinic instability, eddy energy and eddy poleward transport of momentum, helping to maintain the lower pressure over the pole in an interactive manner. The heat flux convergence in the Indian Ocean provides a warming tendency in that region, and overall global production of AABW remains unchanged. These results have implications for the interpretation of the ice core records of

  4. Transient tracer applications in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Stöven, T.; Tanhua, T.; Hoppema, M.

    2014-10-01

    Transient tracers can be used to constrain the Inverse-Gaussian transit time distribution (IG-TTD) and thus provide information about ocean ventilation. Individual transient tracers have different time and application ranges which are defined by their atmospheric history (chronological transient tracers) or their decay rate (radioactive transient tracers). The classification ranges from tracers for highly ventilated water masses, e.g. sulfur hexafluoride (SF6), the decay of Tritium (δ3H) and to some extent also dichlorodifluoromethane (CFC-12) to tracers for less ventilated deep ocean basins, e.g. CFC-12, Argon-39 (39Ar) and radiocarbon (14C). The IG-TTD can be empirically constrained by using transient tracer couples with sufficiently different input functions. Each tracer couple has specific characteristics which influence the application limit of the IG-TTD. Here we provide an overview of commonly used transient tracer couples and their validity areas within the IG-TTD by using the concept of tracer age differences (TAD). New measured CFC-12 and SF6 data from a section along 10° E in the Southern Ocean in 2012 are presented. These are combined with a similar data set of 1998 along 6° E in the Southern Ocean as well as with 39Ar data from the early 1980s in the western Atlantic Ocean and the Weddell Sea for investigating the application limit of the IG-TTD and to analyze changes in ventilation in the Southern Ocean. We found that the IG-TTD can be constrained south to 46° S which corresponds to the Subantarctic Front (SAF) denoting the application limit. The constrained IG-TTD north of the SAF shows a slight increase in mean ages between 1998 and 2012 in the upper 1200 m between 42-46° S. The absence of SF6 inhibits ventilation analyses below this depth. The time lag analysis between the 1998 and 2012 data shows an increase in ventilation down to 1000 m and a steady ventilation between 2000 m-bottom south of the SAF between 51-55° S.

  5. Phytoplankton and cloudiness in the Southern Ocean.

    PubMed

    Meskhidze, Nicholas; Nenes, Athanasios

    2006-12-01

    The effect of ocean biological productivity on marine clouds is explored over a large phytoplankton bloom in the Southern Ocean with the use of remotely sensed data. Cloud droplet number concentration over the bloom was twice what it was away from the bloom, and cloud effective radius was reduced by 30%. The resulting change in the short-wave radiative flux at the top of the atmosphere was -15 watts per square meter, comparable to the aerosol indirect effect over highly polluted regions. This observed impact of phytoplankton on clouds is attributed to changes in the size distribution and chemical composition of cloud condensation nuclei. We propose that secondary organic aerosol, formed from the oxidation of phytoplankton-produced isoprene, can affect chemical composition of marine cloud condensation nuclei and influence cloud droplet number. Model simulations support this hypothesis, indicating that 100% of the observed changes in cloud properties can be attributed to the isoprene secondary organic aerosol. PMID:17082422

  6. Observations of change in the Southern Ocean.

    PubMed

    Jacobs, Stan

    2006-07-15

    The Southern Ocean has been in a state of disequilibrium with its atmosphere and cryosphere during recent decades. Ocean station and drifting float observations have revealed rising temperatures in the upper 3000m. Salinity has declined in intermediate waters and more rapidly in the sparsely sampled high latitudes. Dissolved oxygen levels may also have decreased, but measurement accuracy is inconsistent. Sea ice area increased from 1979 to 1998, particularly in the Ross Sea, while a decline in ice extent since the early 1970s has been led by the Amundsen-Bellingshausen sector. Fresher waters with lower oxygen isotope content on the Pacific-Antarctic continental shelf are consistent with increased melting of continental ice. Newly forming bottom water has become colder and less salty downstream from that region, but generally warmer in the Weddell Sea. Many ice shelves have retreated or thinned, but others have grown and no trend is apparent in the large iceberg calving rate. Warming and isotherm shoaling within the polar gyres may result in part from changes in the Southern Annular Mode, which could facilitate deep-water access to the continental shelves. Sea-level rise over the past half century has a strong eustatic component and has recently accelerated. Observations over longer periods and with better spatial coverage are needed to better understand the processes causing these changes and their links to the Antarctic ice sheet. PMID:16782605

  7. Benthic myodocopid Ostracoda (Philomedidae) from the Southern Ocean.

    PubMed

    Chavtur, Vladimir G; Keyser, Dietmar

    2016-01-01

    This study is based on the material of myodocopid ostracodes of the family Philomedidae collected by the Russian Antarctic Polar Expeditions (1963-2007) and the Germany Expeditions on R/V "Polarstern" (1990-2002) from the continental shelf and upper slope near the Mawson and Davis stations, the Weddell Seas, the region of the South Shetland Islands near the Russian Polar station "Molodezhnaya" and adjacent waters. Eight philomedid species belonging to two genera were identified in these collections. Scleroconcha tuberculata sp. nov. is described and figured as a new species. Additional descriptions and figures for the species S. gallardoi Kornicker, 1971, Philomedes assimilis Brady, 1907, P. charcoti Daday, 1908, P. heptatrix Kornicker, 1975, P. rotunda Skogsberg, 1920, P. orbicularis Brady, 1907 and P. tetrathrix Kornicker, 1975 are given. Keys for all species of the mentioned genera known from the Southern Ocean are presented. A list of sampling stations and species collected is provided in the Appendix 1. PMID:27470832

  8. A Southern Ocean mode of multidecadal variability

    NASA Astrophysics Data System (ADS)

    Le Bars, D.; Viebahn, J. P.; Dijkstra, H. A.

    2016-03-01

    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 multidecadal cycle is up to 60 ZJ. This change results from surface heat flux variations in the South Atlantic and propagation of temperature anomalies along the Antarctic Circumpolar Current and into the Weddell gyre around 30°E. The temperature anomalies propagate as deep as 5000 m along the isopycnals between 50°S and 30°S and induce multidecadal changes in the Atlantic Meridional Overturning Circulation. A positive feedback loop between the generation of eddies through baroclinic instability and the dynamics of the mean circulation is essential for the existence of the SOM. The dominant physics appears similar to that responsible for variability found in a three-layer quasi-geostrophic eddy-resolving model. This combined with the fact that the SOM is not found in a noneddying version of the same global POP model further suggests that eddy processes are crucial for its existence and/or excitation.

  9. Eddy stirring in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Naveira Garabato, A. C.; Ferrari, R.; Polzin, K. L.

    2011-09-01

    There is an ongoing debate concerning the distribution of eddy stirring across the Antarctic Circumpolar Current (ACC) and the nature of its controlling processes. The problem is addressed here by estimating the isentropic eddy diffusivity κ from a collection of hydrographic and altimetric observations, analyzed in a mixing length theoretical framework. It is shown that, typically, κ is suppressed by an order of magnitude in the upper kilometer of the ACC frontal jets relative to their surroundings, primarily as a result of a local reduction of the mixing length. This observation is reproduced by a quasi-geostrophic theory of eddy stirring across a broad barotropic jet based on the scaling law derived by Ferrari and Nikurashin (2010). The theory interprets the observed widespread suppression of the mixing length and κ in the upper layers of frontal jets as the kinematic consequence of eddy propagation relative to the mean flow within jet cores. Deviations from the prevalent regime of mixing suppression in the core of upper-ocean jets are encountered in a few special sites. Such `leaky jet' segments appear to be associated with sharp stationary meanders of the mean flow that are generated by the interaction of the ACC with major topographic features. It is contended that the characteristic thermohaline structure of the Southern Ocean, consisting of multiple upper-ocean thermohaline fronts separated and underlaid by regions of homogenized properties, is largely a result of the widespread suppression of eddy stirring by parallel jets.

  10. The reinvigoration of the Southern Ocean carbon sink.

    PubMed

    Landschützer, Peter; Gruber, Nicolas; Haumann, F Alexander; Rödenbeck, Christian; Bakker, Dorothee C E; van Heuven, Steven; Hoppema, Mario; Metzl, Nicolas; Sweeney, Colm; Takahashi, Taro; Tilbrook, Bronte; Wanninkhof, Rik

    2015-09-11

    Several studies have suggested that the carbon sink in the Southern Ocean-the ocean's strongest region for the uptake of anthropogenic CO2 -has weakened in recent decades. We demonstrated, on the basis of multidecadal analyses of surface ocean CO2 observations, that this weakening trend stopped around 2002, and by 2012, the Southern Ocean had regained its expected strength based on the growth of atmospheric CO2. All three Southern Ocean sectors have contributed to this reinvigoration of the carbon sink, yet differences in the processes between sectors exist, related to a tendency toward a zonally more asymmetric atmospheric circulation. The large decadal variations in the Southern Ocean carbon sink suggest a rather dynamic ocean carbon cycle that varies more in time than previously recognized. PMID:26359401

  11. Atmosphere-ocean interactions in the Pacific Southern Ocean

    NASA Astrophysics Data System (ADS)

    Lamy, F.; Gersonde, R.; Purcell, C.; Winckler, G.; Tiedemann, R.; Knorr, G.

    2014-12-01

    Atmosphere-ocean interactions play an important role for understanding processes and feedbacks in the Southern Ocean (SO) that play a key role for explaining the variability in atmospheric CO2 concentrations. The most important atmospheric forcing at high and mid-latitudes of the Southern Hemisphere is the westerly wind belt which strongly impacts the strength and extension of the Antarctic Circumpolar Current (ACC), upwelling of deep-water masses, and also controls the back-flow of intermediate waters to the tropics. We combine sea surface temperature, current strength, and mineral dust proxy data from the Pacific SO including Drake Passage with climate model results. Our data show that Drake Passage throughflow was reduced and the ACC generally weakened during the last glacial. The reduced Drake Passage throughflow was accompanied by a pronounced northward extension of the Antarctic cold-water sphere in the Southeast Pacific sector and stronger export of surface and intermediate water into the South Pacific gyre. These oceanographic changes are consistent with reduced westerly winds within the modern maximum wind strength zone over the subantarctic ACC and reduced wind forcing due to extended sea-ice further south. Despite of reduced winds in the core of the westerlies, we observe 3-fold higher dust deposition during glacial periods in the Pacific SO. This observation may be explained by a combination of factors including more expanded arid dust source areas in Australia and a northward extent or enhancement of the westerlies over Southeast Australia during glacials that would plausibly increase the dust uptake and export into the Pacific SO. Such scenario would imply stronger westerlies at the present northernmost margin of the wind belt coeval with weaker core westerlies and reduced ACC strength including Drake Passage throughflow during glacials. These results have strong implications for the global meridional overturning circulation and the interbasin

  12. Warming of the Southern Ocean since the 1950s.

    PubMed

    Gille, Sarah T

    2002-02-15

    Autonomous Lagrangian Circulation Explorer floats recorded temperatures in depths between 700 and 1100 meters in the Southern Ocean throughout the 1990s. These temperature records are systematically warmer than earlier hydrographic temperature measurements from the region, suggesting that mid-depth Southern Ocean temperatures have risen 0.17 degrees C between the 1950s and the 1980s. This warming is faster than that of the global ocean and is concentrated within the Antarctic Circumpolar Current, where temperature rates of change are comparable to Southern Ocean atmospheric temperature increases. PMID:11847337

  13. Birth of two volcanic islands in the southern Red Sea.

    PubMed

    Xu, Wenbin; Ruch, Joël; Jónsson, Sigurjón

    2015-01-01

    Submarine eruptions that lead to the formation of new volcanic islands are rare and far from being fully understood; only a few such eruptions have been witnessed since Surtsey Island emerged to the south of Iceland in the 1960s. Here we report on two new volcanic islands that were formed in the Zubair archipelago of the southern Red Sea in 2011-2013. Using high-resolution optical satellite images, we find that the new islands grew rapidly during their initial eruptive phases and that coastal erosion significantly modified their shapes within months. Satellite radar data indicate that two north-south-oriented dykes, much longer than the small islands might suggest, fed the eruptions. These events occurred contemporaneously with several local earthquake swarms of the type that typically accompany magma intrusions. Earthquake activity has been affecting the southern Red Sea for decades, suggesting the presence of a magmatically active zone that has previously escaped notice. PMID:26010945

  14. Birth of two volcanic islands in the southern Red Sea

    PubMed Central

    Xu, Wenbin; Ruch, Joël; Jónsson, Sigurjón

    2015-01-01

    Submarine eruptions that lead to the formation of new volcanic islands are rare and far from being fully understood; only a few such eruptions have been witnessed since Surtsey Island emerged to the south of Iceland in the 1960s. Here we report on two new volcanic islands that were formed in the Zubair archipelago of the southern Red Sea in 2011–2013. Using high-resolution optical satellite images, we find that the new islands grew rapidly during their initial eruptive phases and that coastal erosion significantly modified their shapes within months. Satellite radar data indicate that two north–south-oriented dykes, much longer than the small islands might suggest, fed the eruptions. These events occurred contemporaneously with several local earthquake swarms of the type that typically accompany magma intrusions. Earthquake activity has been affecting the southern Red Sea for decades, suggesting the presence of a magmatically active zone that has previously escaped notice. PMID:26010945

  15. The Evolution of Volcanic Ocean Islands and Biota

    NASA Astrophysics Data System (ADS)

    Dietrich, W. E.; Power, M. E.; Perron, T.

    2011-12-01

    Species or taxon abundances on ocean island archipelagoes consistently show a power law dependency on island area. Nearly 50 years ago, MacArthur and Wilson proposed a theory to explain this dependency, focusing on the equilibrium species number that arises from the balance of immigration and extinction. Subsequent studies have strongly supported this revolutionary theory, applying it to ecological islands ranging in scale from cobbles to sub-continents. The MacArthur and Wilson theory assumes speciation on islands was unimportant, yet studies of remote ocean islands, where endemics dominate many taxa, suggest that simultaneous evolution of organisms and their islands is a first order process influencing species richness. Molecular clock studies now allow tracking of species radiation events across islands, in many cases showing evidence of progression from older to younger islands. Recently efforts have been made to add speciation to the MacArthur and Wilson model (most notably by Whittaker et al., 2008, J.Biogeogr), specifically tying it to the time and physical evolution of ocean islands. This challenges evolutionary scientists, ecologists, and geoscientists to develop mutually useful understanding of how island evolution drives speciation. Volcanic ocean islands over mantle plumes (e.g. Hawaii, Society, Galapagos, Marquesas, and Samoa island chains) present the possibility of a well-defined age succession, observable physical changes, and abundant endemics. These island chains present some appealing constraints: active island construction typically is about 1 million years and in most cases the oldest island is about 5 million years. Once the islands are sufficiently tall and wide they can increase precipitation by over 3 times relative to the open ocean. But this precipitation is commonly non uniform, with windward sides much wetter, and, if islands attain sufficient height, maximum precipitation occurring below the island peak. Coarsely, islands build

  16. The reinvigoration of the Southern Ocean carbon sink

    NASA Astrophysics Data System (ADS)

    Landschützer, Peter; Gruber, Nicolas; Haumann, F. Alexander; Rödenbeck, Christian; Bakker, Dorothee C. E.; van Heuven, Steven; Hoppema, Mario; Metzl, Nicolas; Sweeney, Colm; Takahashi, Taro; Tilbrook, Bronte; Wanninkhof, Rik

    2015-09-01

    Several studies have suggested that the carbon sink in the Southern Ocean—the ocean’s strongest region for the uptake of anthropogenic CO2 —has weakened in recent decades. We demonstrated, on the basis of multidecadal analyses of surface ocean CO2 observations, that this weakening trend stopped around 2002, and by 2012, the Southern Ocean had regained its expected strength based on the growth of atmospheric CO2. All three Southern Ocean sectors have contributed to this reinvigoration of the carbon sink, yet differences in the processes between sectors exist, related to a tendency toward a zonally more asymmetric atmospheric circulation. The large decadal variations in the Southern Ocean carbon sink suggest a rather dynamic ocean carbon cycle that varies more in time than previously recognized.

  17. Macquarie island and the cause of oceanic linear magnetic anomalies.

    PubMed

    Varne, R; Gee, R D; Quilty, P G

    1969-10-10

    Macquarie Islands is formed of probably Pliocene oceanic crust. Intruded into pillow lavas is a belt of harzburgite and layered gabbro mnasses cut by dike swarms. Similar belt-like structures may cause the linear magnetic anomalies of the ocean. PMID:17731490

  18. Extratropical Cyclone in the Southern Ocean

    NASA Technical Reports Server (NTRS)

    2001-01-01

    These images from the Multi-angle Imaging SpectroRadiometer portray an occluded extratropical cyclone situated in the Southern Ocean, about 650 kilometers south of the Eyre Peninsula, South Australia.

    Parts of the Yorke Peninsula and a portion of the Murray-Darling River basin are visible between the clouds near the top of the left-hand image, a true-color view from MISR's nadir(vertical-viewing) camera. Retrieved cloud-tracked wind velocities are indicated by the superimposed arrows. The image on the right displays cloud-top heights. Areas where cloud heights could not be retrieved are shown in black. Both the wind vectors and the cloud heights were derived using data from multiple MISR cameras within automated computer processing algorithms. The stereoscopic algorithms used to generate these results are still being refined, and future versions of these products may show modest changes.

    Extratropical cyclones are the dominant weather system at midlatitudes, and the term is used generically for region allow-pressure systems in the mid- to high-latitudes. In the southern hemisphere, cyclonic rotation is clockwise. These storms obtain their energy from temperature differences between air masses on either side of warm and cold fronts, and their characteristic pattern is of warm and cold fronts radiating out from a migrating low pressure center which forms, deepens, and dissipates as the fronts fold and collapse on each other. The center of this cyclone has started to decay, with the band of cloud to the south most likely representing the main front that was originally connected with the cyclonic circulation.

    These views were acquired on October 11, 2001 during Terra orbit 9650, and represent an area of about 380 kilometers x 1900 kilometers.

  19. Extratropical Cyclone in the Southern Ocean

    NASA Technical Reports Server (NTRS)

    2002-01-01

    These images from the Multi-angle Imaging SpectroRadiometer (MISR) portray an occluded extratropical cyclone situated in the Southern Ocean, about 650 kilometers south of the Eyre Peninsula, South Australia. The left-hand image, a true-color view from MISR's nadir (vertical-viewing) camera, shows clouds just south of the Yorke Peninsula and the Murray-Darling river basin in Australia. Retrieved cloud-tracked wind velocities are indicated by the superimposed arrows. The image on the right displays cloud-top heights. Areas where cloud heights could not be retrieved are shown in black. Both the wind vectors and the cloud heights were derived using data from multiple MISR cameras within automated computer processing algorithms. The stereoscopic algorithms used to generate these results are still being refined, and future versions of these products may show modest changes. Extratropical cyclones are the dominant weather system at midlatitudes, and the term is used generically for regional low-pressure systems in the mid- to high-latitudes. In the southern hemisphere, cyclonic rotation is clockwise. These storms obtain their energy from temperature differences between air masses on either side of warm and cold fronts, and their characteristic pattern is of warm and cold fronts radiating out from a migrating low pressure center which forms, deepens, and dissipates as the fronts fold and collapse on each other. The center of this cyclone has started to decay, with the band of cloud to the south most likely representing the main front that was originally connected with the cyclonic circulation. These views were acquired on October 11, 2001, and the large view represents an area of about 380 kilometers x 1900 kilometers. Image courtesy NASA/GSFC/LaRC/JPL, MISR Team.

  20. Exploring the southern ocean response to climate change

    NASA Technical Reports Server (NTRS)

    Martinson, Douglas G.; Rind, David; Parkinson, Claire

    1993-01-01

    The purpose of this project was to couple a regional (Southern Ocean) ocean/sea ice model to the existing Goddard Institute for Space Science (GISS) atmospheric general circulation model (GCM). This modification recognizes: the relative isolation of the Southern Ocean; the need to account, prognostically, for the significant air/sea/ice interaction through all involved components; and the advantage of translating the atmospheric lower boundary (typically the rapidly changing ocean surface) to a level that is consistent with the physical response times governing the system evolution (that is, to the base of the fast responding ocean surface layer). The deeper ocean beneath this layer varies on time scales several orders of magnitude slower than the atmosphere and surface ocean, and therefore the boundary between the upper and deep ocean represents a more reasonable fixed boundary condition.

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

    NASA Astrophysics Data System (ADS)

    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

  2. Sea Ice on the Southern Ocean

    NASA Technical Reports Server (NTRS)

    Jacobs, Stanley S.

    1998-01-01

    Year-round satellite records of sea ice distribution now extend over more than two decades, providing a valuable tool to investigate related characteristics and circulations in the Southern Ocean. We have studied a variety of features indicative of oceanic and atmospheric interactions with Antarctic sea ice. In the Amundsen & Bellingshausen Seas, sea ice extent was found to have decreased by approximately 20% from 1973 through the early 1990's. This change coincided with and probably contributed to recently warmer surface conditions on the west side of the Antarctic Peninsula, where air temperatures have increased by approximately 0.5 C/decade since the mid-1940's. The sea ice decline included multiyear cycles of several years in length superimposed on high interannual variability. The retreat was strongest in summer, and would have lowered the regional mean ice thickness, with attendant impacts upon vertical heat flux and the formation of snow ice and brine. The cause of the regional warming and loss of sea ice is believed to be linked to large-scale circulation changes in the atmosphere and ocean. At the eastern end of the Weddell Gyre, the Cosmonaut Polyna revealed greater activity since 1986, a recurrence pattern during recent winters and two possible modes of formation. Persistence in polynya location was noted off Cape Ann, where the coastal current can interact more strongly with the Antarctic Circumpolar Current. As a result of vorticity conservation, locally enhanced upwelling brings warmer deep water into the mixed layer, causing divergence and melting. In the Ross Sea, ice extent fluctuates over periods of several years, with summer minima and winter maxima roughly in phase. This leads to large interannual cycles of sea ice range, which correlate positively with meridinal winds, regional air temperatures and subsequent shelf water salinities. Deep shelf waters display considerable interannual variability, but have freshened by approximately 0.03/decade

  3. Oceanic Platform of the Canary Islands: an ocean testbed for ocean energy converters

    NASA Astrophysics Data System (ADS)

    González, Javier; Hernández-Brito, Joaquín.; Llinás, Octavio

    2010-05-01

    The Oceanic Platform of the Canary Islands (PLOCAN) is a Governmental Consortium aimed to build and operate an off-shore infrastructure to facilitate the deep sea research and speed up the technology associated. This Consortium is overseen by the Spanish Ministry of Science and Innovation and the Canarian Agency for Research and Innovation. The infrastructure consists of an oceanic platform located in an area with depths between 50-100 meters, close to the continental slope and four kilometers off the coast of Gran Canaria, in the archipelago of the Canary Islands. The process of construction will start during the first months of 2010 and is expected to be finished in mid-year 2011. PLOCAN serves five strategic lines: an integral observatory able to explore from the deep ocean to the atmosphere, an ocean technology testbed, a base for underwater vehicles, an innovation platform and a highly specialized training centre. Ocean energy is a suitable source to contribute the limited mix-energy conformed in the archipelago of the Canary Islands with a total population around 2 million people unequally distributed in seven islands. Islands of Gran Canaria and Tenerife support the 80% of the total population with 800.000 people each. PLOCAN will contribute to develop the ocean energy sector establishing a marine testbed allowing prototypes testing at sea under a meticulous monitoring network provided by the integral observatory, generating valuable information to developers. Reducing costs throughout an integral project management is an essential objective to be reach, providing services such as transportation, customs and administrative permits. Ocean surface for testing activities is around 8 km2 with a depth going from 50 to 100 meters, 4km off the coast. Selected areas for testing have off-shore wind power conditions around 500-600 W/m2 and wave power conditions around 6 kW/m in the East coast and 10 kW/m in the North coast. Marine currents in the Canary Islands are

  4. An observing system simulation for Southern Ocean carbon dioxide uptake.

    PubMed

    Majkut, Joseph D; Carter, Brendan R; Frölicher, Thomas L; Dufour, Carolina O; Rodgers, Keith B; Sarmiento, Jorge L

    2014-07-13

    The Southern Ocean is critically important to the oceanic uptake of anthropogenic CO2. Up to half of the excess CO2 currently in the ocean entered through the Southern Ocean. That uptake helps to maintain the global carbon balance and buffers transient climate change from fossil fuel emissions. However, the future evolution of the uptake is uncertain, because our understanding of the dynamics that govern the Southern Ocean CO2 uptake is incomplete. Sparse observations and incomplete model formulations limit our ability to constrain the monthly and annual uptake, interannual variability and long-term trends. Float-based sampling of ocean biogeochemistry provides an opportunity for transforming our understanding of the Southern Ocean CO2 flux. In this work, we review current estimates of the CO2 uptake in the Southern Ocean and projections of its response to climate change. We then show, via an observational system simulation experiment, that float-based sampling provides a significant opportunity for measuring the mean fluxes and monitoring the mean uptake over decadal scales. PMID:24891388

  5. The Southern Ocean biological response to aeolian iron deposition.

    PubMed

    Cassar, Nicolas; Bender, Michael L; Barnett, Bruce A; Fan, Songmiao; Moxim, Walter J; Levy, Hiram; Tilbrook, Bronte

    2007-08-24

    Biogeochemical rate processes in the Southern Ocean have an important impact on the global environment. Here, we summarize an extensive set of published and new data that establishes the pattern of gross primary production and net community production over large areas of the Southern Ocean. We compare these rates with model estimates of dissolved iron that is added to surface waters by aerosols. This comparison shows that net community production, which is comparable to export production, is proportional to modeled input of soluble iron in aerosols. Our results strengthen the evidence that the addition of aerosol iron fertilizes export production in the Southern Ocean. The data also show that aerosol iron input particularly enhances gross primary production over the large area of the Southern Ocean downwind of dry continental areas. PMID:17717181

  6. Decreased calcification in the Southern Ocean over the satellite record

    NASA Astrophysics Data System (ADS)

    Freeman, Natalie M.; Lovenduski, Nicole S.

    2015-03-01

    Widespread ocean acidification is occurring as the ocean absorbs anthropogenic carbon dioxide from the atmosphere, threatening marine ecosystems, particularly the calcifying plankton that provide the base of the marine food chain and play a key role within the global carbon cycle. We use satellite estimates of particulate inorganic carbon (PIC), surface chlorophyll, and sea surface temperature to provide a first estimate of changing calcification rates throughout the Southern Ocean. From 1998 to 2014 we observe a 4% basin-wide reduction in summer calcification, with ˜9% reductions in large regions (˜1 × 106 km2) of the Pacific and Indian sectors. Southern Ocean trends are spatially heterogeneous and primarily driven by changes in PIC concentration (suspended calcite), which has declined by ˜24% in these regions. The observed decline in Southern Ocean calcification and PIC is suggestive of large-scale changes in the carbon cycle and provides insight into organism vulnerability in a changing environment.

  7. Southern Ocean warming delayed by circumpolar upwelling and equatorward transport

    NASA Astrophysics Data System (ADS)

    Armour, Kyle C.; Marshall, John; Scott, Jeffery R.; Donohoe, Aaron; Newsom, Emily R.

    2016-07-01

    The Southern Ocean has shown little warming over recent decades, in stark contrast to the rapid warming observed in the Arctic. Along the northern flank of the Antarctic Circumpolar Current, however, the upper ocean has warmed substantially. Here we present analyses of oceanographic observations and general circulation model simulations showing that these patterns--of delayed warming south of the Antarctic Circumpolar Current and enhanced warming to the north--are fundamentally shaped by the Southern Ocean's meridional overturning circulation: wind-driven upwelling of unmodified water from depth damps warming around Antarctica; greenhouse gas-induced surface heat uptake is largely balanced by anomalous northward heat transport associated with the equatorward flow of surface waters; and heat is preferentially stored where surface waters are subducted to the north. Further, these processes are primarily due to passive advection of the anomalous warming signal by climatological ocean currents; changes in ocean circulation are secondary. These findings suggest the Southern Ocean responds to greenhouse gas forcing on the centennial, or longer, timescale over which the deep ocean waters that are upwelled to the surface are warmed themselves. It is against this background of gradual warming that multidecadal Southern Ocean temperature trends must be understood.

  8. Postglacial Records of Southern Hemisphere Westerly Wind Variability From the New Zealand Subantarctic Auckland Islands

    NASA Astrophysics Data System (ADS)

    Moy, C. M.; Vandergoes, M.; Gilmer, G. J.; Nichols, J. E.; Dagg, B. J.; Wilson, G. S.; Browne, I. M.; Curtin, L. G.; Aebig, C.; McGlone, M.

    2015-12-01

    The strength and latitudinal position of the Southern Hemisphere westerly winds (SHWW) play a fundamental role in influencing mid latitude climate and carbon dioxide exchange between the Southern Ocean and the atmosphere. Despite their importance, our understanding of past changes in the SHWW is limited by few paleoclimate records from the modern wind maximum that are often not in agreement. The New Zealand subantarctic Auckland Islands are located within the core of the modern wind belt (50°S) where the ocean-atmospheric linkages between the Antarctic and middle latitudes are strong. In contrast to other subantarctic islands on the Campbell Plateau, the Auckland Islands have protected fjord sub-basins, deep lakes, and peatlands that are advantageous for the development of high-resolution paleoclimate records. We will present ongoing work towards the establishment of multi-proxy and multi-site reconstructions of past SHWW variability from the Auckland Islands. Modern process and paleoclimate results from two research cruises in 2014 and 2015 suggest that in lacustrine and fjord settings, the degree of water column mixing, the stable isotopic composition of n-alkanes and benthic foraminifera, the influx of terrestrial organic matter are good indicators of wind-induced mixing of the water column or precipitation-driven erosion within catchments. In ombrotrophic peatlands, hydrogen isotope ratios of specific organic molecules allow reconstructions of the hydrogen isotope ratios of precipitation, which is related to precipitation source area and the latitudinal position of the SHWW. Using macrofossil counts paired with abundances of leaf wax biomarkers, we are able to estimate the moisture balance at peatland coring sites. Early results indicate an overall strengthening of the SHWW at the Auckland Islands through the Holocene. We will discuss these results within the context of complimentary records developed from New Zealand and southern South America to ultimately

  9. [Dengue fever in the Reunion Island and in South Western islands of the Indian Ocean].

    PubMed

    D'Ortenzio, E; Balleydier, E; Baville, M; Filleul, L; Renault, P

    2011-09-01

    South Western islands of the Indian Ocean are permanently threatened by dengue fever outbreaks. On the Reunion Island, two dengue outbreaks were biologically documented (1977-1978 and 2004). And since July 2004 there has been an inter-epidemic period for the island with sporadic cases and clusters. Between January 1, 2007 and October 5, 2009, the epidemiologic surveillance system detected five confirmed autochthonous cases, five confirmed imported cases (South-East Asia), and 71 probable cases. All the five autochthonous confirmed cases occurred in Saint-Louis during two consecutive clusters. In other South Western islands of the Indian Ocean, several dengue fever outbreaks have been reported. Importation of dengue virus from South-East Asia is a major risk for a new outbreak on the island. The introduction of a new serotype could lead to the emergence of new and severe clinical forms, including dengue hemorrhagic fever. PMID:21295427

  10. Recent Changes in the Ventilation of the Southern Oceans

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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. PMID:23372011

  12. Microphysics and Southern Ocean Cloud Feedback

    NASA Astrophysics Data System (ADS)

    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

  13. Controls on biogenic silica burial in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Chase, Zanna; Kohfeld, Karen E.; Matsumoto, Katsumi

    2015-10-01

    Understanding the controls on opal export in the Southern Ocean can inform both the prediction of how the leakage of silicic acid from the Southern Ocean responds to climate and the interpretation of paleo-proxies. We have compiled a database of 185 230Thorium-normalized opal burial rates and 493 opal concentration measurements in Southern Ocean sediments and matched these with environmental climatologies. By subdividing the Southern Ocean on the basis of oceanographic regions and interpolating the opal burial rates, we estimate a total biogenic Si burial south of 40°S of 2.3 ± 1.0 Tmol Si yr-1. In both the seasonally ice-covered and permanently ice-free regions we can explain 73% of opal burial variability from surface ocean properties. Where sea ice is present for at least part of the year, the length of the ice-free season determines the upper limit of opal burial in the underlying sediments. In the ice-free regions of the Southern Ocean, the supply of silicic acid through winter mixing is the most important factor. Our results do not support a strong role of iron in controlling opal burial. We do however find that satellite-derived net primary production increases with increasing (modeled) dust delivery. These findings support the decoupling between carbon and opal fluxes in the Southern Ocean. When corrected for opal dissolution, the observed opal fluxes are in reasonable agreement with fluxes simulated using an ocean biogeochemical model. However, the results suggest current preservation algorithms for opal could be improved by incorporating the composition of particle flux, not only its magnitude.

  14. Pronounced warming in the Indian and Pacific sectors of the Southern Ocean during the 1970s

    NASA Astrophysics Data System (ADS)

    Turney, Chris; Fogwill, Chris; Palmer, Jonathan; van Sebille, Erik; Thomas, Zoë; McGlone, Matt; Richardson, Sarah; Wilmshurst, Janet; Fenwick, Pavla; Carter, Lionel; Jones, Richard; Harsch, Melanie; Wilson, Kerry-Jayne; Clark, Graeme; Marzinelli, Ezequiel; Rogers, Tracey; Rainsley, Eleanor; Ciasto, Laura; Waterman, Stephanie; Antarctic Expedition 2013-2014 Members, Australasian

    2015-04-01

    Occupying some 20% of the world's ocean surface, the Southern Ocean is home to a diverse and unique biota and plays a fundamental role in global oceanic circulation, climate variability, Antarctic ice sheet stability and carbon cycling. Significant warming has been observed over recent decades, most prominently in the Antarctic Circumpolar Current (ACC). The mechanism(s) behind this warming, however, remain uncertain. Here, we integrate historic ocean and atmospheric observations and climate-sensitive tree growth on subantarctic islands from the northern limit of the ACC to extend historic and satellite measurements to produce a unique proxy record of temperature across 4˚ of latitude in the southwest Pacific. We demonstrate a hitherto unobserved abrupt warming during the 1970s that is unprecedented over the past 130 years, coincident with a significant decline in marine vertebrate populations and wider warming across the Indian Ocean. Comparison between our reconstruction and high-resolution ocean modelling provides a possible mechanism, suggesting warmer waters resulted from a poleward migration of the subtropical and ACC fronts. Projected increases in the strength of westerly winds are likely to continue the fronts' migration, driving warming in the Southern Ocean (>50˚S), with significant impacts on biota.

  15. Seismic structure of the lithosphere beneath the ocean islands near the mid-oceanic ridges

    NASA Astrophysics Data System (ADS)

    Haldar, C.; Kumar, P.; Kumar, M. Ravi

    2013-10-01

    Deciphering the seismic character of the young lithosphere near the mid-oceanic ridges (MOR) is a challenging endeavor. In this study, we determine the seismic structure of the oceanic plate near the MORs, using the P-to-s conversions isolated from good quality data recorded at 5 broadband seismological stations situated on the ocean Islands in their vicinity. Estimates of the crustal and lithospheric thickness values from waveform modeling of the P receiver function stacks reveal that the crustal thickness varies between 6 and 8 km with the corresponding depths to the lithosphere asthenosphere boundary (LAB) varying between 43 and 68 km. However, the depth to the LAB at Macquire Island is intriguing in view of the observation of a thick (~ 87 km) lithosphere beneath a relatively young crust. At three other stations i.e., Ascension Island, Sao Jorge and Easter Island, we find evidence for an additional deeper low velocity layer probably related to the presence of a hotspot.

  16. An oceanic teleconnection between the equatorial and southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Schouten, M. W.; de Ruijter, W. P. M.; van Leeuwen, P. J.; Dijkstra, H. A.

    2002-08-01

    Sequences of Kelvin and Rossby waves are found to rapidly carry sea surface height anomalies across the Indian Ocean, and have an impact on Indian to Atlantic interocean exchange. Satellite altimeter data reveal an oceanic teleconnection between equatorial winds and variability of the interocean exchange. Four times per year, we observe an equatorial Kelvin wave to hit Indonesia, forced by monsoon variability. The signal then propagates southward along the Indonesian coast and triggers Rossby waves that propagate westward across the subtropical Indian Ocean. On reaching the Madagascar and Mozambique Channel regions, large rings form at the same four per year frequency. These drift towards the Agulhas retroflection where they control the shedding of Agulhas rings. Disturbances of this pin-ball-like propagating signal can be traced from Indian Ocean Dipole/El Niño events in 1994 and 1997/1998, to decreases of Indian-Atlantic ocean exchange by Agulhas rings over two years later.

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

    NASA Astrophysics Data System (ADS)

    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

  18. Microwave remote sensing of the Southern Ocean ice cover

    NASA Astrophysics Data System (ADS)

    Comiso, Josefino C.; Grenfell, Thomas C.; Lange, Manfred; Lohanick, Alan W.; Moore, Richard K.; Wadhams, Peter

    The Southern Ocean sea ice cover grows dramatically to about 20 × 106 km2 in the spring and breaks up abruptly to about 4 × 106 km2 in the summer (e.g., Zwally et al. [1983b]). This makes it one of the most seasonally variable climate parameters on the surface of the globe. Compared to the Northern Hemisphere, the ice cover in the Southern Ocean is about 20% greater at its maximum extent [Comiso and Zwally, 1984; Gloersen and Campbell, 1988]. By virtue of its size alone, the impact of the Southern Ocean ice cover on the regional and global climate can be considerable, since sea ice drastically changes surface albedo and roughness and insulates the ocean from the atmosphere. Seasonal and interannual variations in the spatial distribution of sea ice also cause the redistribution of salts, which, in turn, cause changes in the vertical stratification of the ocean. Compared to the Arctic, the environmental geographical background for sea ice in the Antarctic is also very different. Land surrounds most of the southern limits of the Arctic ice cover, whereas in the Antarctic, there is no corresponding land boundary in the north. The Southern Ocean ice cover is more divergent since it is more vulnerable to dynamic forcing than its Arctic counterpart. Accurate estimation of the percentage of open water is important because heat and salinity fluxes increase considerably even with just small increases in the fraction of open water or new ice [Maykut, 1978; Allison, 1981]. These fluxes are, in turn, closely linked with bottom water formation, ocean circulation, and momentum exchange between the ocean and the atmosphere. Oceanic heat flux is also believed to be a major determinant of ice growth rate [Bagriantsev et. al., 1989].

  19. 33 CFR 334.1420 - Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing range. 334.1420 Section 334.1420... AND RESTRICTED AREA REGULATIONS § 334.1420 Pacific Ocean off Orote Point, Apra Harbor, Island of...

  20. 33 CFR 334.1420 - Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing range. 334.1420 Section 334.1420... AND RESTRICTED AREA REGULATIONS § 334.1420 Pacific Ocean off Orote Point, Apra Harbor, Island of...

  1. 33 CFR 334.1420 - Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing range. 334.1420 Section 334.1420... AND RESTRICTED AREA REGULATIONS § 334.1420 Pacific Ocean off Orote Point, Apra Harbor, Island of...

  2. 33 CFR 334.1420 - Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing range. 334.1420 Section 334.1420... AND RESTRICTED AREA REGULATIONS § 334.1420 Pacific Ocean off Orote Point, Apra Harbor, Island of...

  3. 33 CFR 334.1420 - Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean off Orote Point, Apra Harbor, Island of Guam, Marianas Islands; small arms firing range. 334.1420 Section 334.1420... AND RESTRICTED AREA REGULATIONS § 334.1420 Pacific Ocean off Orote Point, Apra Harbor, Island of...

  4. On the role of sea ice for Southern Ocean stratification

    NASA Astrophysics Data System (ADS)

    Haumann, F. Alexander; Münnich, Matthias; Gruber, Nicolas

    2013-04-01

    The formation, subsequent lateral transport, and melt of sea ice represents a key process for the determination of upper ocean stratification in the Southern Ocean. Sea ice is transported northward in large parts of the Southern Ocean by strong near-surface winds and melts along the ice edge south of the polar front, an important upwelling region. Here, it adds freshwater to the surface ocean, lowers the sea-water density, and possibly reduces upwelling by increasing the stratification. Consequently, this redistribution of freshwater in time and space affects the vertical overturning circulation which is an important determinant of the ocean-atmosphere CO2 exchange and, thus, of the global climate. We investigate the Southern Ocean sea-ice ocean system using satellite observations together with simulations with a newly developed regional ocean sea-ice model on the basis of ROMS. As it is not possible yet to derive sea-ice volume transport from remote sensing data due to a lack of ice thickness data, we quantify the freshwater flux exerted by the sea ice from the model and compare it to the observed sea-ice area transport. This shows that the transport is large in the Weddell and Ross Seas where sea ice extends to its lowest latitudes. We assess the importance of sea-ice freshwater transport on the stratification and circulation by comparing this flux to the net atmospheric freshwater flux from reanalysis data and by perturbing our model simulations.

  5. Near-island biological hotspots in barren ocean basins.

    PubMed

    Gove, Jamison M; McManus, Margaret A; Neuheimer, Anna B; Polovina, Jeffrey J; Drazen, Jeffrey C; Smith, Craig R; Merrifield, Mark A; Friedlander, Alan M; Ehses, Julia S; Young, Charles W; Dillon, Amanda K; Williams, Gareth J

    2016-01-01

    Phytoplankton production drives marine ecosystem trophic-structure and global fisheries yields. Phytoplankton biomass is particularly influential near coral reef islands and atolls that span the oligotrophic tropical oceans. The paradoxical enhancement in phytoplankton near an island-reef ecosystem--Island Mass Effect (IME)--was first documented 60 years ago, yet much remains unknown about the prevalence and drivers of this ecologically important phenomenon. Here we provide the first basin-scale investigation of IME. We show that IME is a near-ubiquitous feature among a majority (91%) of coral reef ecosystems surveyed, creating near-island 'hotspots' of phytoplankton biomass throughout the upper water column. Variations in IME strength are governed by geomorphic type (atoll vs island), bathymetric slope, reef area and local human impacts (for example, human-derived nutrient input). These ocean oases increase nearshore phytoplankton biomass by up to 86% over oceanic conditions, providing basal energetic resources to higher trophic levels that support subsistence-based human populations. PMID:26881874

  6. Near-island biological hotspots in barren ocean basins

    PubMed Central

    Gove, Jamison M.; McManus, Margaret A.; Neuheimer, Anna B.; Polovina, Jeffrey J.; Drazen, Jeffrey C.; Smith, Craig R.; Merrifield, Mark A.; Friedlander, Alan M.; Ehses, Julia S.; Young, Charles W.; Dillon, Amanda K.; Williams, Gareth J.

    2016-01-01

    Phytoplankton production drives marine ecosystem trophic-structure and global fisheries yields. Phytoplankton biomass is particularly influential near coral reef islands and atolls that span the oligotrophic tropical oceans. The paradoxical enhancement in phytoplankton near an island-reef ecosystem—Island Mass Effect (IME)—was first documented 60 years ago, yet much remains unknown about the prevalence and drivers of this ecologically important phenomenon. Here we provide the first basin-scale investigation of IME. We show that IME is a near-ubiquitous feature among a majority (91%) of coral reef ecosystems surveyed, creating near-island ‘hotspots' of phytoplankton biomass throughout the upper water column. Variations in IME strength are governed by geomorphic type (atoll vs island), bathymetric slope, reef area and local human impacts (for example, human-derived nutrient input). These ocean oases increase nearshore phytoplankton biomass by up to 86% over oceanic conditions, providing basal energetic resources to higher trophic levels that support subsistence-based human populations. PMID:26881874

  7. Sea level trends in the Southern Ocean over the last century from historical data

    NASA Astrophysics Data System (ADS)

    Testut, Laurent; Martin-Miguez, Belén.; Watson, Christopher; Wöppelmann, Guy; Coleman, Richard; Creach, Ronan; Brolsma, Henk; Handsworth, Roger; Pouvreau, Nicolas; Legrésy, Benoit

    2010-05-01

    It is well known that the spatial distribution of sea level measurements throughout the Southern Ocean is sparse and mostly consists of datasets with short records. The PSMSL (Permanent Service for Mean Sea Level) has only a few sea level time series below 45° South and most of them are shorter than twenty years. The lack of observations constrains the ability to determine or reconstruct global estimates of mean sea level change over the past century. For this reason, any available historical information becomes invaluable for deriving long-term estimates of sea level change in this part of the world. The aim of this presentation is to describe the way we have recovered and analysed the available historic sea level observations made in few sites of the Southern Ocean and to propose new reliable long term sea level trend estimates in this region. The first site is Saint-Paul, a small island of the Southern Indian Ocean where historical measurements were done in 1874 and connected to the permanent GLOSS tide gauge. The two other historical observations were recorded by the Australasian Antarctic Expedition lead by Sir Douglas Mawson in 1912 at Maquarie Island and Cap Denison (Antarctica). The last site concerned by this presentation is the Dumont d'Urville (Antarctica) where historical information from the beginning of the 1950's were found and analysed.

  8. Travel-associated Diseases, Indian Ocean Islands, 1997–2010

    PubMed Central

    Gautret, Philippe; Gaudart, Jean; Field, Vanessa; Castelli, Francesco; López-Vélez, Rogelio; Lim, Poh Lian; Shaw, Marc; von Sonnenburg, Frank; Loutan, Louis; Simon, Fabrice

    2013-01-01

    Data collected by the GeoSentinel Surveillance Network for 1,415 ill travelers returning from Indian Ocean islands during 1997–2010 were analyzed. Malaria (from Comoros and Madagascar), acute nonparasitic diarrhea, and parasitoses were the most frequently diagnosed infectious diseases. An increase in arboviral diseases reflected the 2005 outbreak of chikungunya fever. PMID:23876977

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

    PubMed

    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. PMID:26827096

  10. Reduced calcification in modern Southern Ocean planktonic foraminifera

    NASA Astrophysics Data System (ADS)

    Moy, Andrew D.; Howard, William R.; Bray, Stephen G.; Trull, Thomas W.

    2009-04-01

    Anthropogenic carbon dioxide has been accumulating in the oceans, lowering both the concentration of carbonate ions and the pH (ref. 1), resulting in the acidification of sea water. Previous laboratory experiments have shown that decreased carbonate ion concentrations cause many marine calcareous organisms to show reduced calcification rates. If these results are widely applicable to ocean settings, ocean acidification could lead to ecosystem shifts. Planktonic foraminifera are single-celled calcite-secreting organisms that represent between 25 and 50% of the total open-ocean marine carbonate flux and influence the transport of organic carbon to the ocean interior. Here we compare the shell weights of the modern foraminifer Globigerina bulloides collected from sediment traps in the Southern Ocean with the weights of shells preserved in the underlying Holocene-aged sediments. We find that modern shell weights are 30-35% lower than those from the sediments, consistent with reduced calcification today induced by ocean acidification. We also find a link between higher atmospheric carbon dioxide and low shell weights in a 50,000-year-long record obtained from a Southern Ocean marine sediment core. It is unclear whether reduced calcification will affect the survival of this and other species, but a decline in the abundance of foraminifera caused by acidification could affect both marine ecosystems and the oceanic uptake of atmospheric carbon dioxide.

  11. Radiological conditions at the Southern Islands of Rongelap Atoll

    SciTech Connect

    Robison, W.L.; Conrado, C.L.

    1996-03-01

    The data presented in the following tables is the total available for each southern island; they include both the data from the 1978 Northern Marshall Island Radiological Survey (NMIRS) and trips to Rongelap Atoll from 1986 through 1991. There are additional samples that were taken at Rongelap Island in 1990 and 1991, and the data are unavailable for this report. In one table we present the number of vegetation samples collected in the 1978 NMIRS and from 1986 through 1991. Again, the majority of the {sup 137}Cs is from the 1986-1991 trips. We have not made additional analyses of {sup 239+240}Pu, {sup 241}Am and {sup 90}Sr because the concentrations are very low and these radionuclides contribute less than 5% of an already very small dose. In another table we show the number of soil samples collected at each island in 1978 and the number collected since 1986. Most of the data are from 1986 through 1991. The major exception is {sup 90}Sr where all of the data are from the 1978 NMIRS. We have done some additional Pu analyses of soils from Rongelap Eniaetok, and Borukka Island but none of the other southern islands. A significant amount of new data for {sup 137}Cs and {sup 241}Am have been generated from the samples collected from 1986 through 1991. The data are presented in the form of summary tables, graphics, detailed appendices and aerial photographs of the islands with the sample locations marked. The identified sample locations from the 1978 NMIRS will be added later.

  12. Excitation of T waves in the Indian Ocean between Srilanka and southern India

    NASA Astrophysics Data System (ADS)

    Chadha, R. K.

    1994-06-01

    T phases of three earthquakes from the Indian Ocean region, recorded by a short-period vertical-component seismic station network located in the vicinity of Kanyakumari on the southernmost tip of India, are studied. Two of these earthquakes are located west of 90°E ridge and one in the Nicobar Island region. However, seven other earthquakes which occurred 150 200 km south of Kanyakumari in the ocean did not produce T phases. An analysis of T-waves (tertiary waves) travel time reveals the zone of P-wave to T-wave conversion (i.e., PT phase) region to coincide with the western continental slope of Srilanka. Further, it is observed that the disposition of the bathymetry between Srilanka and southern India strongly favours the downslope propagation mechanism of T-wave travel to the southern coast of India through SOFAR channel. These observations are reported for the first time from India.

  13. Low-frequency vocalizations of sei whales (Balaenoptera borealis) in the Southern Ocean.

    PubMed

    Calderan, Susannah; Miller, Brian; Collins, Kym; Ensor, Paul; Double, Michael; Leaper, Russell; Barlow, Jay

    2014-12-01

    Simultaneous sightings and acoustic detections of sei whales (Balaenoptera borealis) are scarce, and there are few published data describing their vocalizations. Analysis of recordings from directional frequency analysis and recording sonobuoys in the presence of sei whales in the Southern Ocean in March 2013 identified both downsweep and upsweep calls. Sound frequencies within all calls were between 34 and 87 Hz with an average call duration of 1.1 s. These very low-frequency sounds share characteristics with sei whale calls recorded near the Hawaiian Islands and off Cape Cod in winter and summer, respectively, but are the first documented sei whale calls in the Southern Ocean that are clearly less than 100 Hz. PMID:25480092

  14. Improved representation of Southern Ocean fronts in a finite element ocean model

    NASA Astrophysics Data System (ADS)

    Janjic, T.; Timmerman, R.; Schroeter, J.

    2012-04-01

    Orsi et al. 1995 determined the positions of fronts in Southern Ocean based on the water mass criteria from hydrographic sections data. Following Orsi et al. 1995 three main Southern Ocean fronts are distinguished, the subantarctic front (SAF), the polar front (PF) and the southern Antarctic Circumpolar current (sACC) front. All three fronts are continuous features of the ACC, and extend from the sea surface to the deep ocean. Several studies used satellite observations (gradients of sea surface height and sea surface temperature) to locate ACC fronts. In recent work by Sokolov and Rintoul 2009, the authors introduced south, north and middle branches of each of the three major fronts. The position of the branches are determined based on the contour lines of absolute SSH, where the absolute SSH values were calculated by adding the SSH anomalies to the mean surface dynamic height (relative to 2500 dbar) derived from the World Ocean Circulation Experiment climatology. In this work, we estimate the locations of the Southern Ocean fronts using the finite element ocean model and the same criteria as specified in Orsi et al. 1995. The ocean model representation of the locations of fronts is improved by assimilating dynamical ocean topography (DOT) data. In our study, the DOT is generated using the satellite altimetry and our knowledge of the geoid as given by the GOCO2S model which combines GRACE and GOCE gravity data. In addition, front locations determined in such a way are compared to the streamline approach of Sokolov and Rintoul 2009.

  15. Limited overwater dispersal and genetic differentiation of the snake-eyed skink (Cryptoblepharus nigropunctatus) in the Oceanic Ogasawara Islands, Japan.

    PubMed

    Hayashi, Fumio; Shima, Akina; Horikoshi, Kazuo; Kawakami, Kazuto; Segawa, Ryoko D; Aotsuka, Tadashi; Suzuki, Tadashi

    2009-08-01

    The genetic differentiation and speciation of lizards on oceanic islands may be affected by their rate of overwater dispersal. Cryptoblepharus is one of the most geographically widespread scincid lizards throughout the Indo-Pacific and Australian regions. Cryptoblepharus nigropunctatus is the northernmost species of the genus, dwelling on several small Pacific islands. To examine the colonization history of this lizard, mitochondrial 16S rDNA and D-loop sequences were compared among populations of the Ogasawara Islands consisting of four island groups (the Muko-jima, Chichi-jima, Haha-jima, and Kazan groups), and an isolated island, Minamitori-shima (Marcus Island). These four groups and Minamitori-shima have not been connected to each other because each is surrounded by deep sea (>100 m). DNA analyses showed that the lizard populations on individual islands had each representative haplotypes. The ancestors of C. nigropunctatus probably arrived on the islands from the southern Pacific Ocean via wave dispersal and differentiated to produce the present state. They appear to have dispersed from their origin along two independent pathways: one between Kitaiwo-to (Kazan group) and the Muko-jima and Chichi-jima groups, and the other among the Minamitori-shima, Minamiiwo-to (Kazan group), and Haha-jima groups. Limited long-distance overwater dispersal may be responsible for the genetic structure of the C. nigropunctatus populations on these oceanic islands. However, among the small islands within the same island group, D-loop haplotypes were shared and the local genetic diversity was usually high, suggesting frequent gene flow across the same group of islands. PMID:19719406

  16. Last Glacial - Holocene climate variability in the Atlantic sector of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Xiao, Wenshen; Esper, Oliver; Gersonde, Rainer

    2016-03-01

    The Southern Ocean plays a major role in the glacial/interglacial global carbon cycle. However, there is a substantial lack of information from its Antarctic Zone south of the Polar Front (PF) to understand key climate processes (e.g., sea ice variability, productivity changes, CO2 source region, shifts of the Southern Westerly Wind) active in this region during the glacial/interglacial transition, due to the limited high-resolution sediment records from this area. To close this gap, we investigated high resolution diatom records from a series of sediment cores from the Atlantic and Western Indian sectors of the Southern Ocean between the modern PF and the Winter Sea Ice (WSI) edge. Summer Sea Surface Temperature (SSST) and sea ice information spanning the past 30 thousand years were derived from diatom transfer functions and indicators, which augment comprehensive information on past surface ocean conditions and related ocean and atmospheric circulation, as well as opal deposition. These complementary lines of evidences also provide important environmental boundary conditions for climate simulations understanding the past climate development in the high latitudes Southern Ocean. Our reconstructions show that the Last Glacial (LG) SSSTs south of the modern PF are 1-3 °C colder than modern conditions, WSI expanded to the modern PF. Our data suggests effective carbon export in the Antarctic Zone during the LG. Deglacial two steps of warming support the bipolar seesaw mechanism. Antarctic Zone is an important source region for the CO2 deglacial increase. The warming was more suppressed towards south, due to continuous ice discharge from Antarctica. The SSSTs exceeded modern values during the early Holocene optimum, when WSI extent probably retreated south of its modern position. The southern boundary of maximum opal deposition zone may have shifted to south of 55°S in the Bouvet Island area at this time. The mid-late Holocene cooling with WSI re-expanding to the

  17. Imaging Canary Island hotspot material beneath the lithosphere of Morocco and southern Spain

    NASA Astrophysics Data System (ADS)

    Miller, Meghan S.; O'Driscoll, Leland J.; Butcher, Amber J.; Thomas, Christine

    2015-12-01

    The westernmost Mediterranean has developed into its present day tectonic configuration as a result of complex interactions between late stage subduction of the Neo-Tethys Ocean, continental collision of Africa and Eurasia, and the Canary Island mantle plume. This study utilizes S receiver functions (SRFs) from over 360 broadband seismic stations to seismically image the lithosphere and uppermost mantle from southern Spain through Morocco and the Canary Islands. The lithospheric thickness ranges from ∼65 km beneath the Atlas Mountains and the active volcanic islands to over ∼210 km beneath the cratonic lithosphere in southern Morocco. The common conversion point (CCP) volume of the SRFs indicates that thinned lithosphere extends from beneath the Canary Islands offshore southwestern Morocco, to beneath the continental lithosphere of the Atlas Mountains, and then thickens abruptly at the West African craton. Beneath thin lithosphere between the Canary hot spot and southern Spain, including below the Atlas Mountains and the Alboran Sea, there are distinct pockets of low velocity material, as inferred from high amplitude positive, sub-lithospheric conversions in the SRFs. These regions of low seismic velocity at the base of the lithosphere extend beneath the areas of Pliocene-Quaternary magmatism, which has been linked to a Canary hotspot source via geochemical signatures. However, we find that this volume of low velocity material is discontinuous along strike and occurs only in areas of recent volcanism and where asthenospheric mantle flow is identified with shear wave splitting analyses. We propose that the low velocity structure beneath the lithosphere is material flowing sub-horizontally northeastwards beneath Morocco from the tilted Canary Island plume, and the small, localized volcanoes are the result of small-scale upwellings from this material.

  18. Inferring source regions and supply mechanisms of iron in the Southern Ocean from satellite data

    NASA Astrophysics Data System (ADS)

    Graham, Robert M.; de Boer, Agatha M.; van Sebille, Erik; kohfeld, Karen E.; Schlosser, Christian

    2016-04-01

    In many biogeochemical models a large shelf sediment iron flux is prescribed through the seafloor over all areas of bathymetry shallower than 1000 m. Here we infer the likely location of shelf sediment iron sources by identifying where mean annual satellite chlorophyll concentrations are enhanced over shallow bathymetry ( > 1000 m). We show that mean annual chlorophyll concentrations are not visibly enhanced over areas of shallow bathymetry located more than 500 km from a coastline. Chlorophyll concentrations > 2 mg m-3 are only found within 50 km of a continental or island coastline. These results suggest that large sedimentary iron fluxes only exist on continental or island shelves. Large sedimentary iron fluxes are unlikely to be found on isolated seamounts and submerged plateaus. We further compare satellite chlorophyll concentrations to the position of ocean fronts to assess the relative role of horizontal advection and upwelling for supplying iron to the ocean surface. Sharp gradients in chlorophyll concentrations are observed across western boundary currents. Large chlorophyll blooms develop where western boundary currents detach from the continental shelves and turn eastwards into the Southern Ocean. Chlorophyll concentrations are enhanced along contours of sea surface height extending off continental and island shelves. These observations support the hypothesis that bioavailable iron from continental shelves is entrained into western boundary currents and advected into the Sub-Antarctic Zone along the Dynamical Subtropical Front. Likewise, iron from island shelves is entrained into nearby fronts and advected downstream. Mean annual chlorophyll concentrations are very low in open ocean regions with large modelled upwelling velocities, where fronts cross over topographic ridges. These results suggests that open ocean upwelling is unlikely to deliver iron to the surface from deep sources such as hydrothermal vents.

  19. Resource partitioning through oceanic segregation of foraging juvenile southern elephant seals ( Mirounga leonina).

    PubMed

    Field, Iain C; Bradshaw, Corey J A; Burton, Harry R; Sumner, Michael D; Hindell, Mark A

    2005-01-01

    In highly dynamic and unpredictable environments such as the Southern Ocean, species that have evolved behaviors that reduce the effects of intra-specific competition may have a selective advantage. This is particularly true when juveniles face disadvantages when foraging due to morphological or physiological limitation, which is the case for many marine mammals. We tracked the at-sea movements of 48 juvenile southern elephant seals ( Mirounga leonina) between the ages of 1 and 4 years from the population at Macquarie Island using locations derived from recorded light levels. There were significant differences in the total amount of the Southern Ocean covered by the different age-groups. The younger seals used a smaller area than the older seals. On average, the younger individuals also made more trips to sea than the older seals and did not travel as far on each trip. Females spent more time at sea than males and there were no significant differences between the total areas used by male and females. In summary, younger seals remained closer to the island at all times, and they spent more time in more northerly regions that older seals. These differences in behavior created temporal and spatial segregation between juveniles of different ages. Therefore, we suggest that these temporal and spatial separations help to avoid intra-specific competition for resources on land, space on beaches, and at-sea foraging areas. Such modifications of haul-out timing and behavior enable them to exploit a patchy and unpredictable environment. PMID:15365810

  20. Constraints on soluble aerosol iron flux to the Southern Ocean at the Last Glacial Maximum

    PubMed Central

    Conway, T.M.; Wolff, E.W.; Röthlisberger, R.; Mulvaney, R.; Elderfield, H.E.

    2015-01-01

    Relief of iron (Fe) limitation in the Southern Ocean during ice ages, with potentially increased carbon storage in the ocean, has been invoked as one driver of glacial–interglacial atmospheric CO2 cycles. Ice and marine sediment records demonstrate that atmospheric dust supply to the oceans increased by up to an order of magnitude during glacial intervals. However, poor constraints on soluble atmospheric Fe fluxes to the oceans limit assessment of the role of Fe in glacial–interglacial change. Here, using novel techniques, we present estimates of water- and seawater-soluble Fe solubility in Last Glacial Maximum (LGM) atmospheric dust from the European Project for Ice Coring in Antarctica (EPICA) Dome C and Berkner Island ice cores. Fe solubility was very variable (1–42%) during the interval, and frequently higher than typically assumed by models. Soluble aerosol Fe fluxes to Dome C at the LGM (0.01–0.84 mg m−2 per year) suggest that soluble Fe deposition to the Southern Ocean would have been ≥10 × modern deposition, rivalling upwelling supply. PMID:26204562

  1. Constraints on soluble aerosol iron flux to the Southern Ocean at the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Conway, T. M.; Wolff, E. W.; Röthlisberger, R.; Mulvaney, R.; Elderfield, H. E.

    2015-07-01

    Relief of iron (Fe) limitation in the Southern Ocean during ice ages, with potentially increased carbon storage in the ocean, has been invoked as one driver of glacial-interglacial atmospheric CO2 cycles. Ice and marine sediment records demonstrate that atmospheric dust supply to the oceans increased by up to an order of magnitude during glacial intervals. However, poor constraints on soluble atmospheric Fe fluxes to the oceans limit assessment of the role of Fe in glacial-interglacial change. Here, using novel techniques, we present estimates of water- and seawater-soluble Fe solubility in Last Glacial Maximum (LGM) atmospheric dust from the European Project for Ice Coring in Antarctica (EPICA) Dome C and Berkner Island ice cores. Fe solubility was very variable (1-42%) during the interval, and frequently higher than typically assumed by models. Soluble aerosol Fe fluxes to Dome C at the LGM (0.01-0.84 mg m-2 per year) suggest that soluble Fe deposition to the Southern Ocean would have been >=10 × modern deposition, rivalling upwelling supply.

  2. A new, rare type of oceanic islands: The case of Norfolk Island

    NASA Astrophysics Data System (ADS)

    Nebel, O.; Whan, T.; Arculus, R. J.; O'Neill, H. S.; Yaxley, G. M.; McAlpine, S.; Smith, I. E.

    2014-12-01

    Most intra-plate oceanic islands are considered to be expressions of partial melting of hot, ascending mantle plumes. Mantle plume activity is often evident by progressively-aged volcanic island chains, early flood basalts, or elevated mantle temperatures (hot-spots). However, some isolated volcanic islands lack these characteristics. Their mantle sources, causes of melting, and geodynamic settings remain elusive. Here we present petrologic and geochemical data for an example of this type of ocean island: Norfolk Island and neighbouring Phillip Island. These islands are only 7 km apart and are located in the Southwest Pacific. They are the only sub-aerial volcanic islands on the Norfolk Ridge, which extends roughly linearly south from New Caledonia and north from New Zealand. The Norfolk Ridge is a continental slice rifted from the eastern Australian margin during opening of the Tasman Sea and the on-going break-up of Gondwana. There are a few isolated, unexplored volcanic edifices trending NNW from the Norfolk Ridge north of Norfolk Island that may be a hot spot trace. Norfolk and Phillip islands are both composed of young (ca. 2-3 Ma), primitive basalts and basaltic andesites containing abundant phenocrysts of olivine and rare pyroxene and feldspar. Major element systematics are unique among the global spectrum of ocean island basalts, with low CaO, high Al2O3, and high Na/Ti indicating that melting processes and/or the mantle source differs from that of any other OIB. However, Fe/Mn are high, similar to other OIB, and REE patterns carry the typical OIB garnet signature. The highest MgO contents approach 9 wt%. The unusual major-element chemistry results in olivine-dominated crystallization extending to low MgO (ca. 6-7 wt%), hence little increase of incompatible elements with decreasing MgO, but surprisingly Ni and Cr also remain nearly constant with MgO. Isotopic compositions (Sr-Nd-Hf) indicate either a primitive mantle source composition (ɛNd=6

  3. Ocean mixing beneath Pine Island Glacier Ice Shelf

    NASA Astrophysics Data System (ADS)

    Kimura, Satoshi; Dutrieux, Pierre; Jenkins, Adrian; Forryan, Alexander; Naveira Garabato, Alberto; Firing, Yvonne

    2016-04-01

    Ice shelves around Antarctica are vulnerable to increase in ocean-driven melting, with the melt rate depending on ocean temperature and strength of sub-ice-shelf-cavity circulations. We present repeated measurements of velocity, temperature, salinity, turbulent kinetic energy dissipation rate and thermal variance dissipation rate beneath Pine Island Glacier Ice Shelf, collected by CTD, ADCP and turbulence sensors mounted on an Autonomous Underwater Vehicle (AUV). The turbulence quantities measured by the AUV outside the ice shelf are in good agreement with ship-based measurements. The highest rate of turbulent kinetic energy dissipation is found near the grounding line, while its temporal fluctuation over seabed ridge within the cavity corresponds to the tidal fluctuation predicted in the Pine Island Bay to the west. The highest thermal variance dissipation rate is found when the AUV was 0.5 m away from the ice, and the thermal variance dissipation generally increases with decreasing distance between the AUV and ice.

  4. Influence of the Southern Ocean on the Global deep ocean stratification

    NASA Astrophysics Data System (ADS)

    Sun, S.; Eisenman, I.; Stewart, A.

    2015-12-01

    The stratification of the deep ocean plays a key role in the climate system by influencing the ocean circulation and regulating the outgassing of CO2. Previous studies have suggested that Southern Ocean processes control the global ocean stratification below the main thermocline (i.e., below ~500m). In this study, three ocean-only simulations are carried out with the Community Earth System Model (CESM1): one control simulation forced with Pre-industrial (PI) surface conditions, a second control simulation forced with Last Glacial Maximum (LGM) surface conditions, and a test simulation forced with LGM surface conditions in southern high latitudes and PI surface conditions elsewhere. We find that the test simulation does broadly reproduce the LGM density stratification of the global ocean below 2000m, but not at intermediate depths between 500m and 1500m. We propose a mechanism whereby the stratification of the intermediate-depth waters is influenced by the differing effects on the surface buoyancy distribution of fixed versus restoring aspects of the surface buoyancy forcing. This implies the Southern Ocean exerts less influence over the global deep ocean stratification than has been previously suggested, at least when considering the difference between LGM and PI climates in CESM1.

  5. A nomenclator of Pacific oceanic island Phyllanthus (Phyllanthaceae), including Glochidion

    PubMed Central

    Wagner, Warren L.; Lorence, David H.

    2011-01-01

    Abstract Recent molecular phylogenetic studies and reevaluation of morphological characters have led to the inclusion of Glochidion within a broader delimitation of Phyllanthus. It is necessary for preparation of the Vascular Flora of the Marquesas Islands to make new combinations for the Marquesan species. We also provide the relevant combinations and listing of all of the currently accepted species of Phyllanthus on Pacific oceanic islands for a total of 69 native species in oceanic Pacific islands. Glochidion tooviianum J. Florenceis here placed into synonymy of Phyllanthus marchionicus (F. Br.) W. L. Wagner & Lorence based on new assessment of recently collected specimens from Nuku Hiva. Glochidion excorticans Fosberg var. calvum Fosberg is placed into synonomy of Phyllanthus ponapense (Hosokawa) W. L. Wagner & Lorenceand Glochidion puberulum Hosokawa and Glochidion excorticans Fosberg are placed in synonymy of Phyllanthus senyavinianus (Glassman)W. L. Wagner & Lorence based on new study of all Micronesian specimens available to us. No infraspecific taxa are recognized within Phyllanthus pacificus of the Marquesas Islands. Species already with valid names in Phyllanthus are also listed for completeness and convenience. Brief distributional comments are given for each species. We propose new names for species for which a new combination is not possible: Phyllanthus florencei W. L. Wagner & Lorence, nom. nov., Phyllanthus mariannensis W.L. Wagner & Lorence, nom. nov., Phyllanthus otobedii W. L. Wagner & Lorence, Phyllanthus raiateaensis W. L. Wagner & Lorence, Phyllanthus st-johnii W. L. Wagner & Lorence, nom. nov., and Phyllanthus vitilevuensis W.L. Wagner & Lorence, nom. nov. We provide information for four additional naturalized species within the region (Phyllanthus amarus, Phyllanthus debilis, Phyllanthus tenellus, and Phyllanthus urinaria). The name Glochidion ramiflorum widely applied to Pacific island populations is here considered to be a species further

  6. Tropical inter-annual SST oscillations and Southern Ocean swells

    NASA Astrophysics Data System (ADS)

    Fan, Yalin; Rogers, Erick; Jensen, Tommy

    2016-04-01

    The possibility of teleconnections between Southern Ocean swells and sea surface temperature (SST) anomalies on inter-annual time scales in the Eastern Pacific Niño3 region and southeastern Indian Ocean is investigated using numerical wave models. Two alternative parameterizations for swell dissipation are used. It is found that swell dissipation in the models is not directly correlated with large inter-annual variations such as the El Nino - Southern Oscillation (ENSO) or Indian Ocean Dipole (IOD). However, using one of the two swell dissipation parameterizations, a correlation is found between observed SST anomalies and the modification of turbulent kinetic energy flux (TKEF) by Southern Ocean swells due to the damping of short wind waves: modeled reduction of TKEF is in opposite phase with the SST anomalies in the Niño-3 region, indicating a potential positive feedback. The modeled bi-monthly averaged TKEF reduction in the southeastern Indian Ocean is also well correlated with the IOD mode.

  7. Intense summer Si-recycling in the surface Southern Ocean

    NASA Astrophysics Data System (ADS)

    Beucher, Charlotte; Tréguer, Paul; Hapette, Ana-Maria; Corvaisier, Rudolph; Metzl, Nicolas; Pichon, Jean-Jacques

    2004-05-01

    Si-cycle in surface waters was investigated in summer 2003 during a transect conducted from south-Australia to Antarctica. Diatoms dominated the microphytoplankton. Silicic acid was depleted up to 60°S a subsurface maximum of biogenic silica (= biosilica) was observed in the Permanent Open Ocean Zone. In the 100-0.01% light zone, the ratio of depth-integrated biosilica dissolution rate (D) to depth-integrated biosilica production rate (P) ranged between 0 to 3.1, being >1 for 5 of our 6 stations. The biosilica dissolution was related to the percentage of dead diatoms but not to the temperature and might be, at least partially, under bacteria mediation. This study shows that during summer the Southern Ocean silicate pump can be much less efficient than usually expected. Existence of scenarios with intense surface Si-recycling in the Southern Ocean has major consequences both for modelers and paleoceanographers.

  8. Glacial-interglacial variability in diatom abundance and valve size: Implications for Southern Ocean paleoceanography

    NASA Astrophysics Data System (ADS)

    Nair, Abhilash; Mohan, Rahul; Manoj, M. C.; Thamban, Meloth

    2015-10-01

    Antarctic sea ice extent along with Southern Ocean biological productivity varied considerably during glacial-interglacial periods, and both are known to have played a considerable role in regulating atmospheric CO2 variations in the past. Here we present data on diatom absolute abundance (valves/g of sediment) and size over the past ~ 42 ka B.P. and how they link to glacial-interglacial changes in Antarctic sea ice extent, Southern Ocean frontal systems, and aeolian dust flux. Our records of sea ice and permanent open ocean zone diatom abundances suggest a shift in the Antarctic winter sea ice limit and Polar Front respectively up to the modern-day Polar Frontal Zone during marine isotopic stages (MIS) 2 and late MIS 3. In addition to glacial shifts in the Polar Front, diatom assemblages also recorded a plausible northward shifts in Polar Front during few intervals of MIS 1. Glacial periods north of the Polar Front in the Indian sector of the Southern Ocean were characterized by higher total diatom abundance, larger Fragilariopsis kerguelensis apical length, and Thalassiosira lentiginosa radius. This is probably a consequence of (1) a northward expansion of the opal belt, a region characterized by high production and export of biogenic silica; (2) an increase in terrigenous input, via erosion of Crozet Islands; and (3) the alleviation of iron deficit by high input of Fe-bearing dust. The larger and highly silicified diatoms such as F. kerguelensis and T. lentiginosa may have mainly contributed in transporting biogenic silica and organic carbon to the seabed for the last 42 ka, in the northern Polar Frontal Zone of the Indian sector of the Southern Ocean.

  9. Fisheries in the Southern Ocean: an ecosystem approach.

    PubMed

    Kock, Karl-Hermann; Reid, Keith; Croxall, John; Nicol, Stephen

    2007-12-29

    The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is bound by its Article II, 3 to follow an ecosystem approach to management. This approach has been extended to the application of a precautionary approach in the late 1980s. In our review, we deal primarily with the science-related aspects of CCAMLR and its development towards an ecosystem approach to the management of the living resources of the Southern Ocean. To assist the Commission in meeting its objectives, as set out in Article II, 3, the Scientific Committee established the CCAMLR Ecosystem Monitoring Programme to detect possible effects of krill fishing on the performance of top-level predators, such as albatrosses, penguins, petrels and fur seals. Fisheries in the Southern Ocean followed the fate of other fisheries worldwide in which target species were depleted to low level one after the other. Currently, two types of fisheries are open: the longline fisheries on Patagonian toothfish (Dissostichus eleginoides) and Antarctic toothfish (Dissostichus mawsoni) and the trawl fisheries on mackerel icefish (Champsocephalus gunnari). Both fisheries are managed in a single-species context, however, with conservation measures in place to protect by-catch species, such as rattails (Macrouridae) and skates and rays (Rajidae). Two major problems still exist in fisheries in the Southern Ocean: the by-catch of birds in longline fisheries primarily in the Indian Ocean and the high level of IUU fishing again in the Indian Ocean. Both, the by-catch of birds and high IUU catches undermine the credibility of CCAMLR to safeguard the marine living resources in the Southern Ocean. PMID:17553767

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Rift zone reorganization through flank instability in ocean island volcanoes: an example from Tenerife, Canary Islands

    NASA Astrophysics Data System (ADS)

    Walter, T. R.; Troll, V. R.; Cailleau, B.; Belousov, A.; Schmincke, H.-U.; Amelung, F.; Bogaard, P.

    2005-04-01

    The relationship between rift zones and flank instability in ocean island volcanoes is often inferred but rarely documented. Our field data, aerial image analysis, and 40Ar/39Ar chronology from Anaga basaltic shield volcano on Tenerife, Canary Islands, support a rift zone—flank instability relationship. A single rift zone dominated the early stage of the Anaga edifice (~6-4.5 Ma). Destabilization of the northern sector led to partial seaward collapse at about ~4.5 Ma, resulting in a giant landslide. The remnant highly fractured northern flank is part of the destabilized sector. A curved rift zone developed within and around this unstable sector between 4.5 and 3.5 Ma. Induced by the dilatation of the curved rift, a further rift-arm developed to the south, generating a three-armed rift system. This evolutionary sequence is supported by elastic dislocation models that illustrate how a curved rift zone accelerates flank instability on one side of a rift, and facilitates dike intrusions on the opposite side. Our study demonstrates a feedback relationship between flank instability and intrusive development, a scenario probably common in ocean island volcanoes. We therefore propose that ocean island rift zones represent geologically unsteady structures that migrate and reorganize in response to volcano flank instability.

  12. Antarctic warming driven by internal Southern Ocean deep convection oscillations

    NASA Astrophysics Data System (ADS)

    Martin, Torge; Pedro, Joel B.; Steig, Eric J.; Jochum, Markus; Park, Wonsun; Rasmussen, Sune O.

    2016-04-01

    Simulations with the free-running, complex coupled Kiel Climate Model (KCM) show that heat release associated with recurring Southern Ocean deep convection can drive centennial-scale Antarctic temperature variations of 0.5-2.0 °C. We propose a mechanism connecting the intrinsic ocean variability with Antarctic warming that involves the following three steps: Preconditioning: heat supplied by the lower branch of the Atlantic Meridional Overturning Circulation (AMOC) accumulates at depth in the Southern Ocean, trapped by the Weddell Gyre circulation; Convection onset: wind and/or sea-ice changes tip the preconditioned, thermally unstable system into the convective state; Antarctic warming: fast sea-ice-albedo feedbacks (on annual to decadal timescales) and slower Southern Ocean frontal and sea-surface temperature adjustments to the convective heat release (on multi-decadal to centennial timescales), drive an increase in atmospheric heat and moisture transport towards Antarctica resulting in warming over the continent. Further, we discuss the potential role of this mechanism to explain climate variability observed in Antarctic ice-core records.

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

    USGS Publications Warehouse

    McKay, Robert; Naish, Tim; Carter, Lionel; Riesselman, Christina; Dunbar, Robert; Sjunneskog, Charlotte; Winter, Diane; Sangiorgi, Francesca; Warren, Courtney; Pagani, Mark; Schouten, Stefan; Willmott, Veronica; Levy, Richard; DeConto, Robert; Powell, Ross 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 AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ~3.3 Ma, followed by a coastal sea surface temperature cooling of ~2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world.

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

    PubMed Central

    McKay, Robert; Naish, Tim; Carter, Lionel; Riesselman, Christina; Dunbar, Robert; Sjunneskog, Charlotte; Winter, Diane; Sangiorgi, Francesca; Warren, Courtney; Pagani, Mark; Schouten, Stefan; Willmott, Veronica; Levy, Richard; DeConto, Robert; Powell, Ross 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 AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ∼3.3 Ma, followed by a coastal sea surface temperature cooling of ∼2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world. PMID:22496594

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

    PubMed

    McKay, Robert; Naish, Tim; Carter, Lionel; Riesselman, Christina; Dunbar, Robert; Sjunneskog, Charlotte; Winter, Diane; Sangiorgi, Francesca; Warren, Courtney; Pagani, Mark; Schouten, Stefan; Willmott, Veronica; Levy, Richard; DeConto, Robert; Powell, Ross D

    2012-04-24

    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 AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ∼3.3 Ma, followed by a coastal sea surface temperature cooling of ∼2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world. PMID:22496594

  16. On the birth of near-modern Southern Ocean ecosystems

    NASA Astrophysics Data System (ADS)

    Houben, A.; Bohaty, S. M.; Passchier, S.; Roehl, U.; Bijl, P.; Pross, J.; Stickley, C. E.; van de Flierdt, T.; Escutia, C.; Klaus, A.; Brinkhuis, H.

    2011-12-01

    It has become widely appreciated that the initiation of major Antarctic glaciation occurred around Eocene - Oligocene boundary times (~34-33 Ma). Some studies suggest that this greenhouse-icehouse transition (GIT) invoked a more productive Southern Ocean and therefore circum-Antarctic marine systems as a result of e.g., increased wind-stress and upwelling after ice-sheet arrival and related atmospheric reorganization. Yet, actual documentation of such presumed major reorganization among plankton communities in the Southern Ocean is quite limited. This is partly due to scarce and incomplete records, and/or lack of suitable plankton remains for various reasons. Principally on the basis of the recent Integrated Ocean Drilling Program Expedition 318, drilling of the Wilkes Land margin, and in context with studies into e.g., XRF-geochemistry, ice rafted debris, and clay mineralogy, we here discuss late Eocene to early Oligocene dinoflagellate cyst assemblage changes related to the GIT, and compare results with several other circum-Antarctic sites. Conspicuously, the earliest Oligocene circum-Antarctic dinoflagellate cyst assemblages are consistently dominated by protoperidinioid taxa, in sharp contrast to the Eocene assemblages. Extant protoperidinioid dinoflagellates have a heterotrophic feeding strategy, are therefore found in association with high productivity ecosystems, and particularly dominate modern southern ocean settings. Combined results indicate the birth of near modern circum-Antarctic marine ecosystems to coincide with the GIT.

  17. How North Atlantic cooling alters Southern Ocean wind

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2011-07-01

    At least seven times during the last ice age, large portions of the polar glaciers crumbled, sending rafts of ice floating into the North Atlantic Ocean. When these icebergs melted, the resultant injection of cold freshwater was enough to drive down ocean temperatures by as much as 12°C. These so-called Heinrich events are associated with rising atmospheric carbon dioxide (CO2) levels, but a mechanism to explain the connection convincingly has yet to arise. One proposed explanation sees the melting-iceberg-triggered North Atlantic cooling tied to increases in CO2 venting from the Southern Ocean, which surrounds Antarctica, through increased wind-driven upwelling. To test this hypothesis, which was initially proposed by researchers in 2009 based on paleoclimate evidence, Lee et al. ran ocean-atmosphere coupled climate simulations to determine the physical mechanism that could support this cross-hemisphere connection. (Paleoceanography, doi:10.1029/ 2010PA002004, 2011)

  18. Feather mercury concentrations in Southern Ocean seabirds: Variation by species, site and time.

    PubMed

    Becker, Peter H; Goutner, Vassilis; Ryan, Peter G; González-Solís, Jacob

    2016-09-01

    We studied mercury contamination in 25 seabird species breeding along a latitudinal gradient across the Southern Ocean, from Gough Island (40°S) through Marion Island (47°S) to Byers Peninsula (63°S). Total mercury concentrations in body feather samples of adults caught at breeding colonies from 2008 to 2011 were determined. Krill (Euphausia spp.) and other zooplankton consumers had low mercury concentrations (gentoo penguin Pygoscelis papua, chinstrap penguin Pseudomonas Antarctica, common diving petrel Pelecanoides urinatrix, broad-billed prion Pachyptila vittata; mean levels 308-753 ng g(-1)), whereas seabirds consuming squid or carrion had high mercury concentrations (ascending order: Kerguelen petrel Aphrodroma brevirostris, southern giant petrel Macronectes giganteus, soft-plumaged petrel Pterodroma mollis, sooty albatross Phoebetria fusca, Atlantic petrel Pterodroma incerta, northern giant petrel Macronectes halli, great-winged petrel Pterodroma macroptera; 10,720-28038 ng g(-1)). The two species with the highest mercury concentrations, northern giant petrels and great-winged petrels, bred at Marion Island. Among species investigated at multiple sites, southern giant petrels had higher mercury levels at Marion than at Gough Island and Byers Peninsula. Mercury levels among Byers Peninsula seabirds were low, in two species even lower than levels measured 10 years before at Bird Island, South Georgia. Replicate measurements after about 25 years at Gough Island showed much higher mercury levels in feathers of sooty albatrosses (by 187%), soft-plumaged petrels (53%) and Atlantic petrels (49%). Concentrations similar to the past were detected in southern giant petrels at Gough and Marion islands, and in northern giant petrels at Marion. There were no clear indications that timing of moult or migratory behavior affected mercury contamination patterns among species. Causes of inter-site or temporal differences in mercury contamination could not be verified

  19. 33 CFR 334.980 - Pacific Ocean; around San Nicolas Island, Calif., naval restricted area.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean; around San Nicolas....980 Pacific Ocean; around San Nicolas Island, Calif., naval restricted area. (a) The area. The waters of the Pacific Ocean around San Nicolas Island, Calif., extending about 3 miles seaward from...

  20. 33 CFR 334.980 - Pacific Ocean, around San Nicholas Island, Calif.; naval restricted area.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean, around San... REGULATIONS § 334.980 Pacific Ocean, around San Nicholas Island, Calif.; naval restricted area. (a) The area—(1) Perimeter (restricted). The waters of the Pacific Ocean around San Nicholas Island,...

  1. 33 CFR 334.980 - Pacific Ocean; around San Nicolas Island, Calif., naval restricted area.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean; around San Nicolas....980 Pacific Ocean; around San Nicolas Island, Calif., naval restricted area. (a) The area. The waters of the Pacific Ocean around San Nicolas Island, Calif., extending about 3 miles seaward from...

  2. 33 CFR 334.980 - Pacific Ocean; around San Nicolas Island, Calif., naval restricted area.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean; around San Nicolas....980 Pacific Ocean; around San Nicolas Island, Calif., naval restricted area. (a) The area. The waters of the Pacific Ocean around San Nicolas Island, Calif., extending about 3 miles seaward from...

  3. 33 CFR 334.980 - Pacific Ocean; around San Nicolas Island, Calif., naval restricted area.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean; around San Nicolas....980 Pacific Ocean; around San Nicolas Island, Calif., naval restricted area. (a) The area. The waters of the Pacific Ocean around San Nicolas Island, Calif., extending about 3 miles seaward from...

  4. ERS-1 scatterometer measurements over the Southern Ocean

    NASA Technical Reports Server (NTRS)

    Freilich, M. H.

    1994-01-01

    Backscatter cross section measurements from the ERS-1 Active Microwave Instrument (AMI) scatterometer were reprocessed to vector winds using the Freilich-Dunbar model function and a meteorologically aided ambiguity removal scheme. This consistent data set was used to examine the wind field over the Southern Ocean from 20 to 60 deg South. The large number of ERS-1 measurements allows relatively accurate calculation of annual mean wind, stress, and curl fields as well as overall statistics of the winds at mid to high southern latitudes. The long duration of the data time series allows preliminary examination of low frequency (semi annual) wind variability.

  5. Risk maps for Antarctic krill under projected Southern Ocean acidification

    NASA Astrophysics Data System (ADS)

    Kawaguchi, S.; Ishida, A.; King, R.; Raymond, B.; Waller, N.; Constable, A.; Nicol, S.; Wakita, M.; Ishimatsu, A.

    2013-09-01

    Marine ecosystems of the Southern Ocean are particularly vulnerable to ocean acidification. Antarctic krill (Euphausia superba; hereafter krill) is the key pelagic species of the region and its largest fishery resource. There is therefore concern about the combined effects of climate change, ocean acidification and an expanding fishery on krill and ultimately, their dependent predators--whales, seals and penguins. However, little is known about the sensitivity of krill to ocean acidification. Juvenile and adult krill are already exposed to variable seawater carbonate chemistry because they occupy a range of habitats and migrate both vertically and horizontally on a daily and seasonal basis. Moreover, krill eggs sink from the surface to hatch at 700-1,000m (ref. ), where the carbon dioxide partial pressure (pCO2) in sea water is already greater than it is in the atmosphere. Krill eggs sink passively and so cannot avoid these conditions. Here we describe the sensitivity of krill egg hatch rates to increased CO2, and present a circumpolar risk map of krill hatching success under projected pCO2 levels. We find that important krill habitats of the Weddell Sea and the Haakon VII Sea to the east are likely to become high-risk areas for krill recruitment within a century. Furthermore, unless CO2 emissions are mitigated, the Southern Ocean krill population could collapse by 2300 with dire consequences for the entire ecosystem.

  6. Extensive dissolution of live pteropods in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Bednaršek, N.; Tarling, G. A.; Bakker, D. C. E.; Fielding, S.; Jones, E. M.; Venables, H. J.; Ward, P.; Kuzirian, A.; Lézé, B.; Feely, R. A.; Murphy, E. J.

    2012-12-01

    The carbonate chemistry of the surface ocean is rapidly changing with ocean acidification, a result of human activities. In the upper layers of the Southern Ocean, aragonite--a metastable form of calcium carbonate with rapid dissolution kinetics--may become undersaturated by 2050 (ref. ). Aragonite undersaturation is likely to affect aragonite-shelled organisms, which can dominate surface water communities in polar regions. Here we present analyses of specimens of the pteropod Limacina helicina antarctica that were extracted live from the Southern Ocean early in 2008. We sampled from the top 200m of the water column, where aragonite saturation levels were around 1, as upwelled deep water is mixed with surface water containing anthropogenic CO2. Comparing the shell structure with samples from aragonite-supersaturated regions elsewhere under a scanning electron microscope, we found severe levels of shell dissolution in the undersaturated region alone. According to laboratory incubations of intact samples with a range of aragonite saturation levels, eight days of incubation in aragonite saturation levels of 0.94-1.12 produces equivalent levels of dissolution. As deep-water upwelling and CO2 absorption by surface waters is likely to increase as a result of human activities, we conclude that upper ocean regions where aragonite-shelled organisms are affected by dissolution are likely to expand.

  7. Evidence for sex-segregated ocean distributions of first-winter wandering albatrosses at Crozet islands.

    PubMed

    Åkesson, Susanne; Weimerskirch, Henri

    2014-01-01

    The highly mobile wandering albatrosses (Diomedea exulans) are adapted to navigate the extreme environment of the Southern Ocean and return to isolated islands to breed. Each year they cover several hundreds of thousands of kilometers during travels across the sea. Little is known about the dispersal flights and migration of young albatrosses. We tracked, by satellite telemetry, the departure dispersal of 13 juvenile wandering albatrosses from the Crozet Islands and compared them with tracks of 7 unrelated adults during the interbreeding season. We used the satellite tracks to identify different behavioural steps of the inherited migration program used by juvenile wandering albatrosses during their first solo-migration. Our results show that the juvenile wandering albatrosses from Crozet Islands moved to sex-specific foraging zones of the ocean using at departures selectively the wind. The results suggest that the inherited migration program used by the juvenile wandering albatrosses encode several distinct steps, based on inherited preferred departure routes, differences in migration distance between sexes, and selective use of winds. During long transportation flights the albatrosses were influenced by winds and both adult and juveniles followed approximate loxodrome (rhumbline) routes coinciding with the foraging zone and the specific latitudes of their destination areas. During the long segments of transportation flights across open seas the juveniles selected routes at more northerly latitudes than adults. PMID:24586254

  8. Evidence for Sex-Segregated Ocean Distributions of First-Winter Wandering Albatrosses at Crozet Islands

    PubMed Central

    Åkesson, Susanne; Weimerskirch, Henri

    2014-01-01

    The highly mobile wandering albatrosses (Diomedea exulans) are adapted to navigate the extreme environment of the Southern Ocean and return to isolated islands to breed. Each year they cover several hundreds of thousands of kilometers during travels across the sea. Little is known about the dispersal flights and migration of young albatrosses. We tracked, by satellite telemetry, the departure dispersal of 13 juvenile wandering albatrosses from the Crozet Islands and compared them with tracks of 7 unrelated adults during the interbreeding season. We used the satellite tracks to identify different behavioural steps of the inherited migration program used by juvenile wandering albatrosses during their first solo-migration. Our results show that the juvenile wandering albatrosses from Crozet Islands moved to sex-specific foraging zones of the ocean using at departures selectively the wind. The results suggest that the inherited migration program used by the juvenile wandering albatrosses encode several distinct steps, based on inherited preferred departure routes, differences in migration distance between sexes, and selective use of winds. During long transportation flights the albatrosses were influenced by winds and both adult and juveniles followed approximate loxodrome (rhumbline) routes coinciding with the foraging zone and the specific latitudes of their destination areas. During the long segments of transportation flights across open seas the juveniles selected routes at more northerly latitudes than adults. PMID:24586254

  9. Isotopic evidence for reduced productivity in the glacial Southern Ocean

    SciTech Connect

    Shemesh, A. ); Macko, S.A. ); Charles, C.D. ); Rau, G.H. )

    1993-10-15

    Records of carbon and nitrogen isotopes in biogenic silica and carbon isotopes in planktonic foraminifera from deep-sea sediment cores from the Southern Ocean reveal that the primary production during the last glacial maximum was lower than Holocene productivity. These observations conflict with the hypothesis that the low atmospheric carbon dioxide concentrations were introduced by an increase in the efficiency of the high-latitude biological pump. Instead, different oceanic sectors may have had high glacial productivity, or alternative mechanisms that do not involve the biological pump must be considered as the primary cause of the low glacial atmospheric carbon dioxide concentrations.

  10. Constraining early to middle Eocene climate evolution of the southwest Pacific and Southern Ocean

    NASA Astrophysics Data System (ADS)

    Dallanave, Edoardo; Bachtadse, Valerian; Crouch, Erica M.; Tauxe, Lisa; Shepherd, Claire L.; Morgans, Hugh E. G.; Hollis, Christopher J.; Hines, Benjamin R.; Sugisaki, Saiko

    2016-01-01

    Studies of early Paleogene climate suffer from the scarcity of well-dated sedimentary records from the southern Pacific Ocean, the largest ocean basin during this time. We present a new magnetostratigraphic record from marine sediments that outcrop along the mid-Waipara River, South Island, New Zealand. Fully oriented samples for paleomagnetic analyses were collected along 45 m of stratigraphic section, which encompasses magnetic polarity Chrons from C23n to C21n (˜ 51.5- 47 Ma). These results are integrated with foraminiferal, calcareous nannofossil, and dinoflagellate cyst (dinocyst) biostratigraphy from samples collected in three different expeditions along a total of ˜80 m of section. Biostratigraphic data indicates relatively continuous sedimentation from the lower Waipawan to the upper Heretaungan New Zealand stages (i.e., lower Ypresian to lower Lutetian, 55.5 to 46 Ma). We provide the first magnetostratigraphically-calibrated age of 48.88 Ma for the base of the Heretaungan New Zealand stage (latest early Eocene). To improve the correlation of the climate record in this section with other Southern Ocean records, we reviewed the magnetostratigraphy of Ocean Drilling Program (ODP) Site 1172 (East Tasman Plateau) and Integrated Ocean Drilling Program (IODP) Site U1356 (Wilkes Land Margin, Antarctica). A paleomagnetic study of discrete samples could not confirm any reliable magnetic polarity reversals in the early Eocene at Site 1172. We use the robust magneto-biochronology of a succession of dinocyst bioevents that are common to mid-Waipara, Site 1172, and Site U1356 to assist correlation between the three records. A new integrated chronology offers new insights into the nature and completeness of the southern high-latitude climate histories derived from these sites.

  11. Interannual variability of monthly Southern Ocean sea ice distributions

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    1992-01-01

    The interannual variability of the Southern-Ocean sea-ice distributions was mapped and analyzed using data from Nimbus-5 ESMR and Nimbus-7 SMMR, collected from 1973 to 1987. The set of 12 monthly maps obtained reveals many details on spatial variability that are unobtainable from time series of ice extents. These maps can be used as baseline maps for comparisons against future Southern Ocean sea ice distributions. The maps are supplemented by more detailed maps of the frequency of ice coverage, presented in this paper for one month within each of the four seasons, and by the breakdown of these results to the periods covered individually by each of the two passive-microwave imagers.

  12. Strong responses of Southern Ocean phytoplankton communities to volcanic ash

    NASA Astrophysics Data System (ADS)

    Browning, T. J.; Bouman, H. A.; Henderson, G. M.; Mather, T. A.; Pyle, D. M.; Schlosser, C.; Woodward, E. M. S.; Moore, C. M.

    2014-04-01

    Volcanic eruptions have been hypothesized as an iron supply mechanism for phytoplankton blooms; however, little direct evidence of stimulatory responses has been obtained in the field. Here we present the results of twenty-one 1-2 day bottle enrichment experiments from cruises in the South Atlantic and Southern Ocean which conclusively demonstrated a photophysiological and biomass stimulation of phytoplankton communities following supply of basaltic or rhyolitic volcanic ash. Furthermore, experiments in the Southern Ocean demonstrated significant phytoplankton community responses to volcanic ash supply in the absence of responses to addition of dissolved iron alone. At these sites, dissolved manganese concentrations were among the lowest ever measured in seawater, and we therefore suggest that the enhanced response to ash may have been a result of the relief of manganese (co)limitation. Our results imply that volcanic ash deposition events could trigger extensive phytoplankton blooms, potentially capable of significant impacts on regional carbon cycling.

  13. Atmospheric occurrence and deposition of hexachlorobenzene and hexachlorocyclohexanes in the Southern Ocean and Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Galbán-Malagón, Cristóbal; Cabrerizo, Ana; Caballero, Gemma; Dachs, Jordi

    2013-12-01

    Despite the distance of Antarctica and the Southern Ocean to primary source regions of organochlorine pesticides, such as hexachlorobenzene (HCB) and hexachlorocyclohexanes (HCHs), these organic pollutants are found in this remote region due to long range atmospheric transport and deposition. This study reports the gas- and aerosol-phase concentrations of α-HCH, γ-HCH, and HCB in the atmosphere from the Weddell, South Scotia and Bellingshausen Seas. The atmospheric samples were obtained in two sampling cruises in 2008 and 2009, and in a third sampling campaign at Livingston Island (2009) in order to quantify the potential secondary sources of HCHs and HCB due to volatilization from Antarctic soils and snow. The gas phase concentrations of HCHs and HCB are low, and in the order of very few pg m-3 α-HCH and γ-HCH concentrations were higher when the air mass back trajectory was coming from the Antarctic continent, consistent with net volatilization fluxes of γ-HCH measured at Livingston Island being a significant secondary source to the regional atmosphere. In addition, the Southern ocean is an important net sink of HCHs, and to minor extent of HCB, due to high diffusive air-to-water fluxes. These net absorption fluxes for HCHs are presumably due to the role of bacterial degradation, depleting the water column concentrations of HCHs in surface waters and driving an air-water disequilibrium. This is the first field study that has investigated the coupling between the atmospheric occurrence of HCHs and HCB, the simultaneous air-water exchange, soil/snow-air exchange, and long range transport of organic pollutants in Antarctica and the Southern Ocean.

  14. Epidemiology of Strongyloides stercoralis on Mekong islands in southern Laos.

    PubMed

    Vonghachack, Youthanavanh; Sayasone, Somphou; Bouakhasith, Dalouny; Taisayavong, Keoka; Akkavong, Kongsap; Odermatt, Peter

    2015-01-01

    Strongyloides stercoralis is a neglected helminth infection potentially that can lead to systemic infection in immunocompromised individuals. In Lao People's Democratic Republic (Lao PDR, Laos), information on S. stercoralis infection is scarce. We assessed S. stercoralis infection and associated risk factors and symptoms on the Mekong islands in Southern Laos. Baermann and Kato-Katz techniques were performed on two stool samples from each individual to detect S. stercoralis larvae and concomitant helminth infections. Among 729 individuals, 41.0% were infected with S. stercoralis. Men were at higher risk than women (OR 1.97, 95% CI 1.45-2.67). Urticaria and body itching was associated with S. stercoralis infection (OR 2.4, 95% CI 1.42-4.05). Infection with Opisthorchis viverrini (72.2%), Schistosoma mekongi (12.8%), and hookworm (56.1%) were very common. Few infections with Trichuris trichiura (3.3%), Ascaris lumbricoides (0.3%) and Taenia spp. (0.3%) were detected. The majority of helminth infections were of light intensity, with prevalences of 80.4%, 92.9%, 64.5%, 100% and 100%, for O. viverrini, hookworm, S. mekongi, T. trichiura and A. lumbricoides, respectively. Nevertheless, heavy infection intensities were observed for O. viverrini (1.0%), S. mekongi (14.0%) and hookworm (2.9%). S. stercoralis is highly endemic on the islands of Khong district, Champasack province, Southern Laos. The national helminth control programme should take action to control this helminth infection. PMID:25291044

  15. Changes in the ventilation of the southern oceans.

    PubMed

    Waugh, Darryn W

    2014-07-13

    Changes in the ventilation of the southern oceans over the past few decades are examined using ocean measurements of CFC-12 and model simulations. Analysis of CFC-12 measurements made between the late 1980s and late 2000s reveal large-scale coherent changes in the ventilation, with a decrease in the age of subtropical Subantarctic Mode Waters (SAMW) and an increase in the age of Circumpolar Deep Waters. The decrease in SAMW age is consistent with the observed increase in wind stress curl and strength of the subtropical gyres over the same period. A decrease in the age of SAMW is also found in Community Climate System Model version 4 perturbation experiments where the zonal wind stress is increased. This decrease is due to both more rapid transport along isopycnals and the movement of the isopycnals. These results indicate that the intensification of surface winds in the Southern Hemisphere has caused large-scale coherent changes in the ventilation of the southern oceans. PMID:24891397

  16. Topographic form stress in the Southern Ocean State Estimate

    NASA Astrophysics Data System (ADS)

    Masich, Jessica; Chereskin, Teresa K.; Mazloff, Matthew R.

    2015-12-01

    We diagnose the Southern Ocean momentum balance in a 6 year, eddy-permitting state estimate of the Southern Ocean. We find that 95% of the zonal momentum input via wind stress at the surface is balanced by topographic form stress across ocean ridges, while the remaining 5% is balanced via bottom friction and momentum flux divergences at the northern and southern boundaries of the analysis domain. While the time-mean zonal wind stress field exhibits a relatively uniform spatial distribution, time-mean topographic form stress concentrates at shallow ridges and across the continents that lie within the Antarctic Circumpolar Current (ACC) latitudes; nearly 40% of topographic form stress occurs across South America, while the remaining 60% occurs across the major submerged ridges that underlie the ACC. Topographic form stress can be divided into shallow and deep regimes: the shallow regime contributes most of the westward form stress that serves as a momentum sink for the ACC system, while the deep regime consists of strong eastward and westward form stresses that largely cancel in the zonal integral. The time-varying form stress signal, integrated longitudinally and over the ACC latitudes, tracks closely with the wind stress signal integrated over the same domain; at zero lag, 88% of the variance in the 6 year form stress time series can be explained by the wind stress signal, suggesting that changes in the integrated wind stress signal are communicated via rapid barotropic response down to the level of bottom topography.

  17. 87Sr/86Sr ratios in basalts from islands in the Indian Ocean

    USGS Publications Warehouse

    Hedge, C.E.; Watkins, N.D.; Hildreth, R.A.; Doering, W.P.

    1973-01-01

    87Sr/86Sr ratios of basalts from islands in the Indian Ocean (0.7040) are higher than those of basalts dredged from the Mid-Indian Ocean Ridge (0.7034). The sources of the island basalts have apparently not been in equilibrium with the source of the ridge basalts for roughly 109 years. Both ridge and island basalts in the Indian Ocean are higher in 87Sr/86Sr than are rocks from similar settings in the eastern Pacific. ?? 1973.

  18. Performance of a Southern Ocean sea ice forecast model

    NASA Astrophysics Data System (ADS)

    Heil, P.; Roberts, A.; Budd, W.

    2003-12-01

    The presentation examines the forecast peformance of an oriented fracture sea ice model applied to the Southern Ocean to predict sea ice state up to five days in advance. The model includes a modified Coulombic elastic-viscous-plastic rheology, enthalpy conserving thermodynamics and a new method of parameterising thickness distribution mechanics. 15 ice thickness classes are employed within each grid cell with a horizontal resolution of 50km. The model provides considerable insight into the thickness evolution and climatology of Antarctic sea ice. To date, thickness evolution of the Southern Ocean sea ice zone has mostly been assessed using course two-category models in climate simulations and results presented in this talk provide much greater detail over some existing model output. Simulations are presented from the model driven with NCEP-2 atmospheric analyses, NOAA sea surface temperatures, and mean climatogological currents generated using an eddy resolving ocean model. Analyses are generated by nudging ice concentrations with daily satellite derived open water fractions, and simulations using this method are compared to those without. There are important considerations in assimilating passive microwave ice concentration data into thickness distribution models, and particular attention is given to the treatment of lead ice and the impact this has on estimated total Southern Ocean sea ice volume. It is shown that nudging the model with satellite derived concentrations has an impact on ice mechanics as judged from simulated buoy tracks. A comparison with sonar soundings of sea ice draft is also favourable but shows variation with location. Whilst 5 day forecasts are reasonably skilled, predictive performance changes with season. Application of this research to operational ocean data assimilation systems is discussed in the final stages of the talk.

  19. Variability of island-induced ocean vortex trains, in the Kuroshio region southeast of Taiwan Island

    NASA Astrophysics Data System (ADS)

    Zheng, Zhe-Wen; Zheng, Quanan

    2014-06-01

    This study examines the horizontal scale and spatial characteristics of island-induced ocean vortex trains (IOVTs) in the Kuroshio region southeast of Taiwan Island using European remote sensing satellite ERS-1 SAR imagery. US Aqua satellite Moderate Resolution Imaging Spectroradiometer (MODIS) data are used to analyze the sea surface temperature (SST) features of the study area. Seasonal composites of SST images show that the IOVTs are current-induced vortexes rather than wind-induced ones. Furthermore, using the HYbrid Coordinate Ocean Model/Navy Coupled Ocean Data Assimilation (HYCOM/NCODA) system that generated current and sea surface height anomaly data, the temporal and spatial variability of the Green Island IOVTs is analyzed. The variability of IOVTs within this region shows a distinct seasonality. This seasonal variability of IOVTs is closely associated with the shoreward shift of Kuroshio mainstream driven by the winter northeasterly monsoon. This scenario is verified by vector empirical orthogonal function analysis focused on the weak IOVT period in 2012. In addition to meandering of the Kuroshio, westward-propagating mesoscale eddies and the arrival of typhoons play an important role in modifying the variability of IOVTs at intraseasonal timescale.

  20. Sea ice trends and cyclone activity in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Coggins, Jack; McDonald, Adrian; Rack, Wolfgang; Dale, Ethan

    2015-04-01

    Significant trends in the extent of Southern Hemisphere sea ice have been noted over the course of the satellite record, with highly variable trends between different seasons and regions. In this presentation, we describe efforts to assess the impact of cyclones on these trends. Employing a maximum cross-correlation method, we derive Southern Ocean ice-motion vectors from daily gridded SSMI 85.5 GHz brightness temperatures. We then derive a sea ice budget from the NASA-Team 25 km square daily sea ice concentrations. The budget quantifies the total daily change in sea ice area, and includes terms representing the effects of ice advection and divergence. A residual term represents the processes of rafting, ridging, freezing and thawing. We employ a cyclone tracking algorithm developed at the University of Canterbury to determine the timing, location, size and strength of Southern Hemisphere cyclones from mean sea-level pressure fields of the ERA-Interim reanalysis. We then form composites of the of sea ice budget below the location of cyclones. Unsurprisingly, we find that clockwise atmospheric flow around Southern Hemisphere cyclones exerts a strong influence on the movement of sea ice, an effect which is visible in the advection and divergence terms. Further, we assess the climatological importance of cyclones by comparing seasons of sea ice advance for periods with varying numbers of cyclones. This analysis is performed independently for each sea ice concentration pixel, thus affording us insight into the geographical importance of storm systems. We find that Southern Hemisphere sea ice extent is highly sensitive to the presence of cyclones in the periphery of the pack in the advance season. Notably, the sensitivity is particularly high in the northern Ross Sea, an area with a marked positive trend in sea ice extent. We discuss whether trends in cyclone activity in the Southern Ocean may have contributed to sea ice extent trends in this region.

  1. Imprint of Southern Ocean eddies on winds, clouds and rainfall

    NASA Astrophysics Data System (ADS)

    Frenger, I.; Gruber, N.; Knutti, R.; Münnich, M.

    2013-08-01

    Owing to the turbulent nature of the ocean, mesoscale eddies are omnipresent. The impact of these transitory and approximately circular sea surface temperature fronts on the overlying atmosphere is not well known. Stationary fronts such as the Gulf Stream have been reported to lead to pronounced atmospheric changes. However, the impact of transient ocean eddies on the atmosphere has not been determined systematically, except on winds and to some extent clouds. Here, we examine the atmospheric conditions associated with over 600,000 individual eddies in the Southern Ocean, using satellite data. We show that ocean eddies locally affect near-surface wind, cloud properties and rainfall. The observed pattern of atmospheric change is consistent with a mechanism in which sea surface temperature anomalies associated with the oceanic eddies modify turbulence in the atmospheric boundary layer. In the case of cyclonic eddies, this modification triggers a slackening of near-surface winds, a decline in cloud fraction and water content, and a reduction in rainfall. We conclude that transient mesoscale ocean structures can significantly affect much larger atmospheric low-pressure systems that swiftly pass by at the latitudes investigated.

  2. Southern Ocean buoyancy forcing of ocean ventilation and glacial atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Watson, Andrew J.; Vallis, Geoffrey K.; Nikurashin, Maxim

    2015-11-01

    Atmospheric CO2 concentrations over glacial-interglacial cycles closely correspond to Antarctic temperature patterns. These are distinct from temperature variations in the mid to northern latitudes, so this suggests that the Southern Ocean is pivotal in controlling natural CO2 concentrations. Here we assess the sensitivity of atmospheric CO2 concentrations to glacial-interglacial changes in the ocean's meridional overturning circulation using a circulation model for upwelling and eddy transport in the Southern Ocean coupled with a simple biogeochemical description. Under glacial conditions, a broader region of surface buoyancy loss results in upwelling farther to the north, relative to interglacials. The northern location of upwelling results in reduced CO2 outgassing and stronger carbon sequestration in the deep ocean: we calculate that the shift to this glacial-style circulation can draw down 30 to 60 ppm of atmospheric CO2. We therefore suggest that the direct effect of temperatures on Southern Ocean buoyancy forcing, and hence the residual overturning circulation, explains much of the strong correlation between Antarctic temperature variations and atmospheric CO2 concentrations over glacial-interglacial cycles.

  3. An investigation of Bjerknes Compensation in the Southern Ocean in the CCSM4

    SciTech Connect

    Weijer, Wilbert; Kinstle, Caroline M.

    2012-08-28

    This project aims to understand the relationship between poleward oceanic and atmospheric heat transport in the Southern Ocean by analyzing output from the community Climate System Model Version 4 (CCSM4). In particular, time series of meridional heat transport in both the atmosphere and the ocean are used to study whether variability in ocean heat transport is balanced by opposing changes in atmospheric heat transport, called Bjerknes Compensation. It is shown that the heat storage term in the Southern Ocean has a significant impact on the oceanic heat budget; as a result, no robust coherences between oceanic and atmospheric heat transports could be found at these southern latitudes.

  4. Rethinking the Ocean's Role in the Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Clement, A. C.; di Nezio, P. N.; Deser, C.

    2010-12-01

    The usual explanation for variability in the Southern Oscillation (SO), a shift of atmospheric mass between the Indo-Pacific warm pool region and the eastern Pacific reflected in opposite sign changes in sea level pressure, involves dynamical coupling between the atmosphere and ocean via the ‘Bjerknes feedback’ mechanism. Here we revisit this explanation using a collection of simulations with atmospheric general circulation models that have varying degrees of coupling to the ocean. The main finding is that the SO emerges as a dominant mode of tropical Pacific variability without dynamical coupling to the ocean. Atmospheric models coupled to a mixed layer ocean (i.e. with no coupled ocean dynamics) simulate what is refered to here as an ‘Atmospheric Walker Mode’ (AWM). This mode of variability has patterns in sea level pressure, sea surface temperature, and precipitation which strongly resemble observed patterns associated with the SO. The spectrum of the AWM is red out to about a decadal timescale, consistent with a stochastically forced, weakly damped process, and our analysis suggests that variability in the AWM is related to variability in the NE and SE trade winds and associated surface wind divergence in the warm pool. The main influence of ocean dynamics on the SO in fully coupled climate models is the addition power primarily at interannual timescales, as expected from the positive Bjerknes feedback. On decadal and longer timescales, ocean dynamics enhance the damping of (or act as a negative feedback on) SO variability. However, interactive ocean dynamics do not appear to be required to set the first-order spatial structure of the SO or associated patterns in SST, precipitation, or atmospheric circulation. Implications for Pacific climate variability on interannual, decadal, and century timescales are discussed.

  5. Iron supply to the Southern Ocean mixed layer from below; the ocean model effect

    NASA Astrophysics Data System (ADS)

    Schourup-Kristensen, Vibe; Hauck, Judith; Losch, Martin; Wolf-Gladrow, Dieter A.; Völker, Christoph

    2015-04-01

    In the iron limited Southern Ocean, the biogeochemical results of commonly used ocean general circulation biogeochemical models differ greatly dependent on the ocean model used. This is largely due to the difficulties in reproducing a realistic mixed layer depth (MLD), which leads to different degrees of light limitation and nutrient supply from below. Regarding the iron sources to the Southern Ocean, research has traditionally focused on the input from dust and the sediment, but recent studies have highlighted the importance of the vertical supply to the mixed layer from the nutrient rich deeper water. This latter supply mechanism may also be affected by the large inter-model differences in the MLD and thereby influence the total net primary production and export production in the models. We have performed a model study in which the biogeochemical model REcoM2 was coupled to two different ocean models, the Finite Element Sea-ice Ocean Model (FESOM) and the MIT general circulation model (MITgcm). The effect of the ocean mixed layer on the magnitude of the iron sources from below in the two models was analyzed, as was the effect on the export and net primary production. Our results revealed a remarkable difference in terms of mode and magnitude of transport dependent on the mixed layer depth in the two models; the mean iron supply from below in the Southern Ocean was on average four times higher in MITgcm than in FESOM. The dominant pathway was entrainment in MITgcm, whereas diffusion dominated in FESOM. We discuss how the difference in the depth and seasonal amplitude of the mixed layer between the models has a major effect on the vertical iron profile and thereby also on the iron fluxes. A further effect of the difference in supply is that the fraction of exported net primary production is higher in MITgcm than in FESOM, showing that the choice of ocean model has a significant impact on the modeled carbon cycle in the Southern Ocean, with possible implications for

  6. Geoid model of Tahiti-Moorea oceanic volcanic islands

    NASA Astrophysics Data System (ADS)

    Shih, H.; Mouyen, M.; Barriot, J.; Hwang, C.; Lequeux, D.; Sichoix, L.

    2013-12-01

    We present the results of an airborne gravity survey that has been conducted over Tahiti-Moorea, two oceanic volcanic islands in French Polynesia, during July and August 2013. The aim of this survey is two-folds. First, these gravity data can be inverted to unravel the subsurface structure of these islands, in particular the geometry of the magma chambers. Second, such data can be used to determine a geoid over Tahiti-Moorea. In this paper, we focus on the geoid modeling. The gravimeter used is the LaCoste & Romberg Air-Sea gravity System II. The aircraft is equipped with a GPS antenna and a receiver, which data are sampled at 1 Hz. A permanent GPS station in the University of French Polynesia is used together with the aircraft GPS to determine precise positions, velocities and accelerations of the plane. These parameters are necessary to get reliable gravity data at mgal accuracy. In addition to the airborne data, land measurements, done from May to August 2013, and shipborne data (1997) are also used for the Tahiti-Moorea geoid. A band-limited least-squares collocation in a classic remove-compute-restore technique is carried out to combine these data into the geoid computation. This geoid will be of primary interest for the analysis of two tide gauges set in Papeete harbor and Tahiti-Iti, altimetric surveys of the oceanic currents as well as for real-time GPS positioning for surveyors in Tahiti.

  7. Impact of 2004 Tsunami in the Islands of Indian Ocean: Lessons Learned

    PubMed Central

    Ramalanjaona, Georges

    2011-01-01

    Tsunami of 2004, caused by a 9.0 magnitude earthquake, is the most devastating tsunami in modern times, affecting 18 countries in Southeast Asia and Southern Africa, killing more than 250,000 people in a single day, and leaving more than 1.7 million homeless. However, less reported, albeit real, is its impact in the islands of the Indian Ocean more than 1,000 miles away from its epicenter. This is the first peer-reviewed paper on the 2004 tsunami events specifically in the eleven nations bordering the Indian Ocean, as they constitute a region at risk, due to the presence of tectonic interactive plate, absence of a tsunami warning system in the Indian Ocean, and lack established communication network providing timely information to that region. Our paper has a dual objective: the first objective is to report the 2004 tsunami event in relation to the 11 nations bordering the Indian Ocean. The second one is to elaborate on lessons learned from it from national, regional, and international disaster management programs to prevent such devastating consequences of tsunami from occurring again in the future. PMID:22046551

  8. Inventory of ocean monitoring in the Southern California Bight.

    PubMed

    Schiff, Kenneth C; Weisberg, Stephen B; Raco-Rands, Valerie

    2002-06-01

    Monitoring of the ocean environment in southern California, USA, has been conducted by a diverse array of public and private organizations with different motivations, working on a variety of spatial and temporal scales. To create a basis from which to integrate information from these diverse programs, we conducted an inventory of ocean monitoring activities in the Southern California Bight to address the following questions: (1) How much money is being expended annually on marine monitoring programs? (2) Which organizations are conducting the most monitoring? (3) How are resources allocated among the different types of monitoring programs? This inventory focused on programs existing, or those expected to be in existence, for at least 10 years and that were active at any time between 1994 and 1997. For each program identified for inclusion in this study, information was collected on the number of sites, sampling intensity, parameters measured, and methods used. Levels of effort were translated into cost estimates based upon a market survey of local consulting firms. One hundred fourteen marine monitoring programs, conducted by 65 organizations and costing US $31 million annually, were identified. Most of the effort (81 programs, 65% of samples, 70% of costs) was expended by ocean dischargers as part of their compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. Federal programs (11 programs, 25% of samples, 10% of total expenditures) expended more than state or local government programs. More than one quarter of monitoring expenditures were conducted to measure concentrations and mass of effluent inputs to the ocean. The largest effort expended on receiving water monitoring was for measuring bacteria, followed by sediments, fish/shellfish, water quality, and intertidal habitats. The large level of expenditures by individual agencies has presented opportunities for integrating small, site-specific ocean monitoring programs into

  9. Small iceberg bursts: melting breakwaters in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Ardhuin, F.; Tournadre, J.; Queffeulou, P.; Girard-Ardhuin, F.

    2010-12-01

    The variability of small-size iceberg distributions is revealed from a novel analysis of satellite altimeter data. The yearly cycle is modulated by pulse-like events confined to single ocean basins. A strong iceberg population is found in the South Atlantic in 2003-2005, and in the South Pacific in 2008. Anomalies of the order of 1°C in sea surface temperatures may be related to the iceberg distribution. Icebergs are very strongly associated with anomalies in the heights of ocean waves, with far-reaching consequences for the global wave climate. A preliminary numerical modelling of wave blocking by icebergs, including partial wave reflection, reduces model errors on the significant wave height by 26% in the region south of 45° South. Observed changes in small iceberg populations thus have profound impacts on Southern ocean dynamics and beyond. Latitude-time Hovmöller diagrams of the small iceberg ice volume cumulated over each 2° band of latitude for (a) the South Atlantic 50°W to 30°E, (b) the Indian Ocean 50°E to 130°, (c) the South Pacific 130°E to 100°, for each 2° band of latitude. (d), (e), and (f) significant wave heigth model bias against satellite altimeters for the same three sectors of the Southern Ocean, for a model without iceberg effects. In the left panels (a,b,c) the black line marks the maximum extend of the sea ice, and in the right panels (c,d,e) the white areas give the minimum extent of the 80% sea ice coverage, used as a mask in the model.

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

    NASA Astrophysics Data System (ADS)

    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

  11. Low-frequency sound level in the Southern Indian Ocean.

    PubMed

    Tsang-Hin-Sun, Eve; Royer, Jean-Yves; Leroy, Emmanuelle C

    2015-12-01

    This study presents long-term statistics on the ambient sound in the Southern Indian Ocean basin based on 2 years of data collected on six widely distributed autonomous hydrophones from 47°S to 4°S and 53°E to 83°E. Daily mean power spectra (10-100 Hz) were analyzed in order to identify the main sound sources and their space and time variability. Periodic signals are principally associated with the seasonal presence of three types of blue whales and fin whales whose signatures are easily identified at specific frequencies. In the low frequencies, occurrence of winter lows and summer highs in the ambient noise levels are well correlated with iceberg volume variations at the southern latitudes, suggesting that icebergs are a major sound source, seasonally contributing to the ambient noise, even at tropical latitudes (26°S). The anthropogenic contribution to the noise spectrum is limited. Shipping sounds are only present north and west of the study area in the vicinity of major traffic lanes. Acoustic recordings from the southern sites may thus be representative of the pristine ambient noise in the Indian Ocean. PMID:26723301

  12. Environmental forcings of Paleogene Southern Ocean dinoflagellate biogeography

    NASA Astrophysics Data System (ADS)

    Bijl, Peter K.; Pross, Jörg; Warnaar, Jeroen; Stickley, Catherine E.; Huber, Matthew; Guerstein, Raquel; Houben, Alexander J. P.; Sluijs, Appy; Visscher, Henk; Brinkhuis, Henk

    2011-02-01

    Despite warm polar climates and low meridional temperature gradients, a number of different high-latitude plankton assemblages were, to varying extents, dominated by endemic species during most of the Paleogene. To better understand the evolution of Paleogene plankton endemism in the high southern latitudes, we investigate the spatiotemporal distribution of the fossil remains of dinoflagellates, i.e., organic-walled cysts (dinocysts), and their response to changes in regional sea surface temperature (SST). We show that Paleocene and early Eocene (˜65-50 Ma) Southern Ocean dinocyst assemblages were largely cosmopolitan in nature but that a distinct switch from cosmopolitan-dominated to endemic-dominated assemblages (the so-called “transantarctic flora”) occurred around the early-middle Eocene boundary (˜50 Ma). The spatial distribution and relative abundance patterns of this transantarctic flora correspond well with surface water circulation patterns as reconstructed through general circulation model experiments throughout the Eocene. We quantitatively compare dinocyst assemblages with previously published TEX86-based SST reconstructions through the early and middle Eocene from a key locality in the southwest Pacific Ocean, ODP Leg 189 Site 1172 on the East Tasman Plateau. We conclude that the middle Eocene onset of the proliferation of the transantarctic flora is not linearly correlated with regional SST records and that only after the transantarctic flora became fully established later in the middle Eocene, possibly triggered by large-scale changes in surface-ocean nutrient availability, were abundances of endemic dinocysts modulated by regional SST variations.

  13. Silicon isotopes reveal recycled altered oceanic crust in the mantle sources of Ocean Island Basalts

    NASA Astrophysics Data System (ADS)

    Pringle, Emily A.; Moynier, Frédéric; Savage, Paul S.; Jackson, Matthew G.; Moreira, Manuel; Day, James M. D.

    2016-09-01

    The study of silicon (Si) isotopes in Ocean Island Basalts (OIB) has the potential to discern between different models for the origins of geochemical heterogeneities in the mantle. Relatively large (∼several per mil per atomic mass unit) Si isotope fractionation occurs in low-temperature environments during biochemical and geochemical precipitation of dissolved Si, where the precipitate is preferentially enriched in the lighter isotopes relative to the dissolved Si. In contrast, only a limited range (∼tenths of a per mil) of Si isotope fractionation has been observed from high-temperature igneous processes. Therefore, Si isotopes may be useful as tracers for the presence of crustal material within OIB mantle source regions that experienced relatively low-temperature surface processes in a manner similar to other stable isotope systems, such as oxygen. Characterizing the isotopic composition of the mantle is also of central importance to the use of the Si isotope system as a basis for comparisons with other planetary bodies (e.g., Moon, Mars, asteroids). Here we present the first comprehensive suite of high-precision Si isotope data obtained by MC-ICP-MS for a diverse suite of OIB. Samples originate from ocean islands in the Pacific, Atlantic, and Indian Ocean basins and include representative end-members for the EM-1, EM-2, and HIMU mantle components. On average, δ30Si values for OIB (-0.32 ± 0.09‰, 2 sd) are in general agreement with previous estimates for the δ30Si value of Bulk Silicate Earth (-0.29 ± 0.07‰, 2 sd; Savage et al., 2014). Nonetheless, some small systematic variations are present; specifically, most HIMU-type (Mangaia; Cape Verde; La Palma, Canary Islands) and Iceland OIB are enriched in the lighter isotopes of Si (δ30Si values lower than MORB), consistent with recycled altered oceanic crust and lithospheric mantle in their mantle sources.

  14. The association between El Niño/Southern Oscillation events and typhoons in the Marshall Islands.

    PubMed

    Spennemann, D H; Marschner, I C

    1995-09-01

    An analysis of the historic record of typhoons in the Marshall Islands has identified a significant association between the occurrence of the El Niño/Southern Oscillation phenomenon (ENSO) and the occurrence of typhoons in the Marshall Islands. Whilst typhoons normally occur further to the east, the warming of the ocean waters around the Marshall Islands, as part of the ENSO phenomenon, generates typhoons further to the west. The results suggest that typhoons are 2.6 times more likely to occur during ENSO years, with a 71 per cent chance of a typhoon striking during an ENSO year, and only a 26 per cent chance of one happening during a non-ENSO year. This has implications for planning and public safety, which the relevant authorities may wish to take note of. PMID:7552109

  15. Deep Ocean Heat Uptake and the Influence of Sea Ice in the Southern Ocean

    SciTech Connect

    Cecilia M. Bitz

    2011-11-22

    Climate sensitivity defines the equilibrium response to climate forcing, but ocean heat uptake is equally important at controlling the transient, response. Heat stored beneath the mixed layer is not in close thermal contact with the atmosphere, and therefore warming below the mixed layer sequesters heat that would otherwise be available to warm the surface, slowing the rate of surface warming. In this study, we investigate mechanisms that control heat uptake, primarily in the Southern Ocean, where roughly 40% of the global heat uptake occurs.

  16. 33 CFR 334.921 - Pacific Ocean at San Clemente Island, Calif.; naval restricted area.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean at San Clemente Island, Calif.; naval restricted area. 334.921 Section 334.921 Navigation and Navigable Waters CORPS OF....921 Pacific Ocean at San Clemente Island, Calif.; naval restricted area. (a) The area. All...

  17. 33 CFR 110.220 - Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. 110.220 Section 110.220 Navigation and Navigable Waters COAST... Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. (a) The restricted areas—(1)...

  18. 33 CFR 334.1360 - Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. 334.1360 Section 334.1360 Navigation and Navigable Waters CORPS OF....1360 Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone....

  19. 33 CFR 110.220 - Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. 110.220 Section 110.220 Navigation and Navigable Waters COAST... Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. (a) The restricted areas—(1)...

  20. 33 CFR 334.1440 - Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. 334.1440 Section 334.1440 Navigation and Navigable Waters CORPS OF....1440 Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. (a) The warning...

  1. 33 CFR 110.220 - Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. 110.220 Section 110.220 Navigation and Navigable Waters COAST... Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. (a) The restricted area....

  2. 33 CFR 334.1360 - Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. 334.1360 Section 334.1360 Navigation and Navigable Waters CORPS OF....1360 Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone....

  3. 33 CFR 334.1370 - Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. 334.1370 Section 334.1370 Navigation and Navigable Waters CORPS OF....1370 Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone. The...

  4. 33 CFR 334.1440 - Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. 334.1440 Section 334.1440 Navigation and Navigable Waters CORPS OF....1440 Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. (a) The warning...

  5. 33 CFR 334.921 - Pacific Ocean at San Clemente Island, Calif.; naval restricted area.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean at San Clemente Island, Calif.; naval restricted area. 334.921 Section 334.921 Navigation and Navigable Waters CORPS OF....921 Pacific Ocean at San Clemente Island, Calif.; naval restricted area. (a) The area. All...

  6. 33 CFR 334.1370 - Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. 334.1370 Section 334.1370 Navigation and Navigable Waters CORPS OF....1370 Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone. The...

  7. 33 CFR 334.1360 - Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. 334.1360 Section 334.1360 Navigation and Navigable Waters CORPS OF....1360 Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone....

  8. 33 CFR 334.1370 - Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. 334.1370 Section 334.1370 Navigation and Navigable Waters CORPS OF....1370 Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone. The...

  9. 33 CFR 334.1440 - Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. 334.1440 Section 334.1440 Navigation and Navigable Waters CORPS OF....1440 Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. (a) The warning...

  10. 33 CFR 334.921 - Pacific Ocean at San Clemente Island, Calif.; naval restricted area.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean at San Clemente Island, Calif.; naval restricted area. 334.921 Section 334.921 Navigation and Navigable Waters CORPS OF....921 Pacific Ocean at San Clemente Island, Calif.; naval restricted area. (a) The area. All...

  11. 33 CFR 110.220 - Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. 110.220 Section 110.220 Navigation and Navigable Waters COAST... Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. (a) The restricted areas—(1)...

  12. 33 CFR 334.1370 - Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. 334.1370 Section 334.1370 Navigation and Navigable Waters CORPS OF....1370 Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone. The...

  13. 33 CFR 334.1140 - Pacific Ocean at San Miguel Island, Calif.; naval danger zone.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean at San Miguel Island, Calif.; naval danger zone. 334.1140 Section 334.1140 Navigation and Navigable Waters CORPS OF....1140 Pacific Ocean at San Miguel Island, Calif.; naval danger zone. (a) The area. The waters around...

  14. 33 CFR 334.1370 - Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. 334.1370 Section 334.1370 Navigation and Navigable Waters CORPS OF....1370 Pacific Ocean at Keahi Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone. The...

  15. 33 CFR 334.1350 - Pacific Ocean, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean, Island of Oahu, Hawaii; danger zone. 334.1350 Section 334.1350 Navigation and Navigable Waters CORPS OF ENGINEERS... Ocean, Island of Oahu, Hawaii; danger zone. (a) The danger zone. Beginning at point of origin at...

  16. 33 CFR 334.1350 - Pacific Ocean, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean, Island of Oahu, Hawaii; danger zone. 334.1350 Section 334.1350 Navigation and Navigable Waters CORPS OF ENGINEERS... Ocean, Island of Oahu, Hawaii; danger zone. (a) The danger zone. Beginning at point of origin at...

  17. 33 CFR 334.1360 - Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. 334.1360 Section 334.1360 Navigation and Navigable Waters CORPS OF....1360 Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone....

  18. 33 CFR 334.130 - Atlantic Ocean off Wallops Island and Chincoteague Inlet, Va.; danger zone.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Atlantic Ocean off Wallops Island and Chincoteague Inlet, Va.; danger zone. 334.130 Section 334.130 Navigation and Navigable Waters... REGULATIONS § 334.130 Atlantic Ocean off Wallops Island and Chincoteague Inlet, Va.; danger zone. (a) The...

  19. 33 CFR 334.921 - Pacific Ocean at San Clemente Island, Calif.; naval restricted area.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean at San Clemente Island, Calif.; naval restricted area. 334.921 Section 334.921 Navigation and Navigable Waters CORPS OF....921 Pacific Ocean at San Clemente Island, Calif.; naval restricted area. (a) The area. All...

  20. 33 CFR 334.1140 - Pacific Ocean at San Miguel Island, Calif.; naval danger zone.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean at San Miguel Island, Calif.; naval danger zone. 334.1140 Section 334.1140 Navigation and Navigable Waters CORPS OF....1140 Pacific Ocean at San Miguel Island, Calif.; naval danger zone. (a) The area. The waters around...

  1. 33 CFR 334.1360 - Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. 334.1360 Section 334.1360 Navigation and Navigable Waters CORPS OF....1360 Pacific Ocean at Barber's Point, Island of Oahu, Hawaii; danger zone. (a) The danger zone....

  2. 33 CFR 110.220 - Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. 110.220 Section 110.220 Navigation and Navigable Waters COAST... Pacific Ocean at San Nicolas Island, Calif.; restricted anchorage areas. (a) The restricted areas—(1)...

  3. 33 CFR 334.921 - Pacific Ocean at San Clemente Island, Calif.; naval restricted area.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean at San Clemente Island, Calif.; naval restricted area. 334.921 Section 334.921 Navigation and Navigable Waters CORPS OF....921 Pacific Ocean at San Clemente Island, Calif.; naval restricted area. (a) The area. All...

  4. 33 CFR 334.1440 - Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. 334.1440 Section 334.1440 Navigation and Navigable Waters CORPS OF....1440 Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. (a) The warning...

  5. 33 CFR 334.1440 - Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. 334.1440 Section 334.1440 Navigation and Navigable Waters CORPS OF....1440 Pacific Ocean at Kwajalein Atoll, Marshall Islands; missile testing area. (a) The warning...

  6. Wide Range of Mercury Contamination in Chicks of Southern Ocean Seabirds

    PubMed Central

    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 δ13C) and trophic positions (reflected by δ15N) on Hg concentrations were investigated. Species-related Hg variations were highly and positively linked to feather δ15N 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 δ13C values, with species feeding in colder waters (lower δ13C values) south of Kerguelen Islands being less prone to be contaminated than species feeding in northern warmer waters (higher δ13C 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. PMID:23349912

  7. Subtropical Indian Ocean SST dipole events and southern African rainfall

    NASA Astrophysics Data System (ADS)

    Reason, C. J. C.

    An atmospheric general circulation model (AGCM) is used to examine how the regional atmospheric circulation and rainfall over southern Africa respond to a recently observed dipole in subtropical sea surface temperature (SST) over the South Indian Ocean. Observations suggest that when SST is warm to the south of Madagascar and cool off Western Australia, increased summer rains occur over large areas of southeastern Africa. The model results suggest that this SST pattern leads to increased rainfall via enhanced convergence of moister than average air over the region. Increased evaporation occurs over the warm pole in the South West Indian Ocean and this moist air is advected towards Mozambique and eastern South Africa as a result of the low pressure anomaly generated over this pole which strengthens the onshore flow.

  8. Oxygen Fugacity Recorded by Xenoliths from Pacific Oceanic Islands

    NASA Astrophysics Data System (ADS)

    Wall, K.; Davis, F. A.; Cottrell, E.

    2014-12-01

    Oxygen fugacity (fO2) plays a vital role in determining mineral stability and depth of melting in the mantle. Several studies have used the spinel peridotite oxybarometer to estimate fO2; yet few data exist from ocean islands, despite the importance of fO2 to understanding ocean island basalt petrogenesis (Herzberg and Asimow, 2008). We report fO2 recorded by peridotite xenoliths from three ocean islands: Savai'i (average fO2 = QFM -1.4 to +0.9), Tahiti (QFM +0.6 to +0.7) and Tubuai (QFM -1.1 to +0.2). We calculate fO2 using methods and standards from Wood and Virgo (1989) and Wood (RiMG, 1990). Oxygen fugacities span a similar range to those reported for El Hierro, Oahu, and Tahiti by Ballhaus (1993): more reduced than arc peridotites, but more oxidized than abyssal peridotites. Spinels in several of the xenoliths are heterogeneous and record a range of apparent fO2 at the mm scale. We propose two distinct mechanisms for introducing fO2 heterogeneity: melt refertilization (Tubuai) and diffusive reequilibration (Savai'i and Tubuai). Spinels in one Tubuai sample record increasing fO2 from QFM-0.6 in the xenolith interior to +1.1 at the basalt interface. Apparent fO2 recorded by these spinels correlate with TiO2, an indicator of melt refertilization (Pearce et al., 2000). We suggest that spinels from the xenolith interior record the relatively low fO2 conditions of the lithospheric mantle, while host basalt has oxidized near-interface spinels. Uniformly high TiO2, fO2, and low olivine Mg# in Tahitian xenoliths from this study may indicate that refertilization has reset the fO2 recorded by these rocks. Closed-system diffusive reequilibration, caused by changes in temperature, can also change the fO2 recorded by a peridotite. In samples from Savai'i and Tubuai with multiple spinel habits, fine intergrowth spinels and the rims of large, equant spinels record higher apparent fO2 and lower Al2O3 than cores of large grains. Canil and O'Neill (1996) suggest that the MgAl2O4

  9. Distinct speed dependence of entorhinal island and ocean cells, including respective grid cells

    PubMed Central

    Sun, Chen; Kitamura, Takashi; Yamamoto, Jun; Martin, Jared; Pignatelli, Michele; Kitch, Lacey J.; Schnitzer, Mark J.; Tonegawa, Susumu

    2015-01-01

    Entorhinal–hippocampal circuits in the mammalian brain are crucial for an animal’s spatial and episodic experience, but the neural basis for different spatial computations remain unknown. Medial entorhinal cortex layer II contains pyramidal island and stellate ocean cells. Here, we performed cell type-specific Ca2+ imaging in freely exploring mice using cellular markers and a miniature head-mounted fluorescence microscope. We found that both oceans and islands contain grid cells in similar proportions, but island cell activity, including activity in a proportion of grid cells, is significantly more speed modulated than ocean cell activity. We speculate that this differential property reflects island cells’ and ocean cells’ contribution to different downstream functions: island cells may contribute more to spatial path integration, whereas ocean cells may facilitate contextual representation in downstream circuits. PMID:26170279

  10. Distinct speed dependence of entorhinal island and ocean cells, including respective grid cells.

    PubMed

    Sun, Chen; Kitamura, Takashi; Yamamoto, Jun; Martin, Jared; Pignatelli, Michele; Kitch, Lacey J; Schnitzer, Mark J; Tonegawa, Susumu

    2015-07-28

    Entorhinal-hippocampal circuits in the mammalian brain are crucial for an animal's spatial and episodic experience, but the neural basis for different spatial computations remain unknown. Medial entorhinal cortex layer II contains pyramidal island and stellate ocean cells. Here, we performed cell type-specific Ca(2+) imaging in freely exploring mice using cellular markers and a miniature head-mounted fluorescence microscope. We found that both oceans and islands contain grid cells in similar proportions, but island cell activity, including activity in a proportion of grid cells, is significantly more speed modulated than ocean cell activity. We speculate that this differential property reflects island cells' and ocean cells' contribution to different downstream functions: island cells may contribute more to spatial path integration, whereas ocean cells may facilitate contextual representation in downstream circuits. PMID:26170279

  11. Seabirds modify El Niño effects on tree growth in a southern Pacific island.

    PubMed

    Molina-Montenegro, Marco A; Torres-Díaz, Cristian; Gallardo-Cerda, Jorge; Leppe, Marcelo; Gianoli, Ernesto

    2013-11-01

    Oceanic island ecosystems are particularly sensitive to El Niño effects due to their dependence on energy and nutrient inputs from marine systems. Seabirds play a key role in transporting resources of marine origin to insular ecosystems. We report tree-growth patterns showing how the effects of El Niño rainy events on tree species in a southern Pacific island depend on the presence of local seabird colonies. We performed manipulative experiments in order to assess the mechanisms underlying these patterns. Tree ring data showed that, in normal years, the growth of all tree species (Aextoxicon punctatum, Cryptocarya alba, and Pinus radiata) was significantly lower in seabird sites compared to adjacent patches without seabirds (control sites). In contrast, in El Niño years, trees formerly hosting seabird colonies grew more than those in control sites. Experiments showed that (1) pine plants on soil from seabird sites grew more than those on soil from control sites, (2) pine individuals with seabird feces on their leaves grew less than those sprayed with an aqueous solution, and (3) soil moisture had little effect on plant growth. The stress produced by massive cormorant nesting on trees, which impairs tree growth and physiological performance, is relieved during El Niño events because of seabird migration due to decreased prey availability and pouring rains that flood nests. Soils enriched by the seabird guano, together with the increased water availability associated with El Niño, foster the growth of trees from seabird sites. We suggest that El Niño may be a key determinant of tree performance in forest communities from island and coastal ecosystems of the Pacific Ocean. PMID:24400493

  12. Influenza A virus on oceanic islands: host and viral diversity in seabirds in the Western Indian Ocean.

    PubMed

    Lebarbenchon, Camille; Jaeger, Audrey; Feare, Chris; Bastien, Matthieu; Dietrich, Muriel; Larose, Christine; Lagadec, Erwan; Rocamora, Gérard; Shah, Nirmal; Pascalis, Hervé; Boulinier, Thierry; Le Corre, Matthieu; Stallknecht, David E; Dellagi, Koussay

    2015-05-01

    Ducks and seabirds are natural hosts for influenza A viruses (IAV). On oceanic islands, the ecology of IAV could be affected by the relative diversity, abundance and density of seabirds and ducks. Seabirds are the most abundant and widespread avifauna in the Western Indian Ocean and, in this region, oceanic islands represent major breeding sites for a large diversity of potential IAV host species. Based on serological assays, we assessed the host range of IAV and the virus subtype diversity in terns of the islands of the Western Indian Ocean. We further investigated the spatial variation in virus transmission patterns between islands and identified the origin of circulating viruses using a molecular approach. Our findings indicate that terns represent a major host for IAV on oceanic islands, not only for seabird-related virus subtypes such as H16, but also for those commonly isolated in wild and domestic ducks (H3, H6, H9, H12 subtypes). We also identified strong species-associated variation in virus exposure that may be associated to differences in the ecology and behaviour of terns. We discuss the role of tern migrations in the spread of viruses to and between oceanic islands, in particular for the H2 and H9 IAV subtypes. PMID:25996394

  13. Influenza A Virus on Oceanic Islands: Host and Viral Diversity in Seabirds in the Western Indian Ocean

    PubMed Central

    Lebarbenchon, Camille; Jaeger, Audrey; Feare, Chris; Bastien, Matthieu; Dietrich, Muriel; Larose, Christine; Lagadec, Erwan; Rocamora, Gérard; Shah, Nirmal; Pascalis, Hervé; Boulinier, Thierry; Le Corre, Matthieu; Stallknecht, David E.; Dellagi, Koussay

    2015-01-01

    Ducks and seabirds are natural hosts for influenza A viruses (IAV). On oceanic islands, the ecology of IAV could be affected by the relative diversity, abundance and density of seabirds and ducks. Seabirds are the most abundant and widespread avifauna in the Western Indian Ocean and, in this region, oceanic islands represent major breeding sites for a large diversity of potential IAV host species. Based on serological assays, we assessed the host range of IAV and the virus subtype diversity in terns of the islands of the Western Indian Ocean. We further investigated the spatial variation in virus transmission patterns between islands and identified the origin of circulating viruses using a molecular approach. Our findings indicate that terns represent a major host for IAV on oceanic islands, not only for seabird-related virus subtypes such as H16, but also for those commonly isolated in wild and domestic ducks (H3, H6, H9, H12 subtypes). We also identified strong species-associated variation in virus exposure that may be associated to differences in the ecology and behaviour of terns. We discuss the role of tern migrations in the spread of viruses to and between oceanic islands, in particular for the H2 and H9 IAV subtypes. PMID:25996394

  14. Microearthquake seismicity in relation to double convergence around the Solomon Islands arc by ocean-bottom seismometer observation

    NASA Astrophysics Data System (ADS)

    Shinohara, Masanao; Suyehiro, Kiyoshi; Murayama, Takayuki

    2003-06-01

    The Solomon Islands arc area is a complex plate convergence zone. At the North Solomon Trench on the northern side of the arc, it is believed that the Pacific Plate was subducting before coming into collision with the Ontong Java Plateau, the world's largest oceanic plateau. After the collision about 5 Ma, northeastward subduction initiated along the southern side of the arc at the San Cristobal Trench, another trench on the south side. GPS observations and crustal seismic structure surveys confirm that convergence occurs at both trenches. Without detailed and accurate seismicity, it is difficult to characterize the plate subduction to reveal the tectonics of such a complex zone where a key mechanism of continental growth may also exist. In 1994, an ocean-bottom seismometer (OBS) experiment was carried out for the first time in the area around the Solomon Islands arc to locate microearthquakes. Observations started in late August and continued until early September. Five digital recording OBSs were deployed around the Russell Islands west of Guadalcanal Island. OBS spacing was about 20 km. All the OBSs were recovered and yielded data with a good signal-to-noise ratio. 40 earthquakes, with magnitudes in the range 1.5-4.4 were located over 8 days. The seismicity clearly images the two subducting plates. Though the seismicity beneath the arc side slope of the San Cristobal Trench is relatively high, we can see the seismicity which is related to the subducting Pacific Plate beneath Santa Isabel Island. In addition, earthquakes occur within the crust beneath the southern part of the New Georgia Basin and the Russell Islands. An aseismic area extending 40 km inward from the San Cristobal trench axis implies initial aseismic slip of the India-Australia Plate at a small dip angle.

  15. Southern Ocean isopycnal mixing and ventilation changes driven by winds

    NASA Astrophysics Data System (ADS)

    Abernathey, Ryan; Ferreira, David

    2015-12-01

    Observed and predicted changes in the strength of the westerly winds blowing over the Southern Ocean have motivated a number of studies on the response of the Antarctic Circumpolar Current and Southern Ocean meridional overturning circulation (MOC) to wind perturbations and led to the hypothesis of the "eddy compensation" regime, wherein the MOC becomes insensitive to wind changes. In addition to the MOC, tracer transport also depends on mixing processes. Here we show, in a high-resolution process model, that isopycnal mixing by mesoscale eddies is strongly dependent on the wind strength. This dependence can be explained by mixing length theory and is driven by increases in eddy kinetic energy; the mixing length does not change strongly in our simulation. Simulation of a passive ventilation tracer (analogous to CFCs or anthropogenic CO2) demonstrates that variations in tracer uptake across experiments are dominated by changes in isopycnal mixing, rather than changes in the MOC. We argue that to properly understand tracer uptake under different wind-forcing scenarios, the sensitivity of isopycnal mixing to winds must be accounted for.

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

    PubMed

    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. PMID:26650733

  17. Recent Precipitation Trends Over the Southern Ocean in Relation to Oceanic Freshening Near Antarctica

    NASA Astrophysics Data System (ADS)

    Cullather, R. I.; Jacobs, S. S.; Giulivi, C. F.; Leonard, K. C.; Stammerjohn, S. E.

    2008-12-01

    Quantitative assessments of large-scale precipitation over the world's oceanic regions are problematic, particularly for significant regions of the data-sparse Southern Hemisphere. Available data sets are based on the assimilation of land-based measurements, satellite radiance values, numerical weather forecast models, or some combination of the three. In this study we examine several products that cover most or all of the satellite era 1979-2007 over the Southern Ocean and surrounding mid-latitudes to 45°S. These include CMAP, the NCEP Reanalysis II, ERA-40, GPCP version 2, and the Japanese Re-analysis. Averaged fields from these data show large discrepancies in the mean spatial depiction and the annual cycle. Comparisons with unique in situ snowfall measurements and satellite-derived accumulation on sea ice are presented. The available record of oceanographic measurements in the Ross Sea indicates that salinity below 200 m in the Ross Sea has decreased by 0.03 per decade since 1958, with the highest (lowest) values in 1967 (2000). The fields examined here suggest that precipitation is likely not directly influencing the oceanic freshening observed in the Ross Sea, or in other coastal seas adjacent to Antarctica. The salinity anomaly is consistent with increasing attrition of continental ice, but places a heavy demand on the melt rate. Potential contributions to oceanic freshening from changes in sea ice extent, transport, and thickness are discussed.

  18. Marine introductions in the Southern Ocean: an unrecognised hazard to biodiversity.

    PubMed

    Lewis, Patrick N; Hewitt, Chad L; Riddle, Martin; McMinn, Andrew

    2003-02-01

    This study investigated the potential for transport of organisms between Hobart, Macquarie Island and the Antarctic continent by ships used in support of Antarctic science and tourism. Northward transport of plankton in ballast water is more likely than southward transport because ballast is normally loaded in the Antarctic and unloaded at the home port. Culturing of ballast water samples revealed that high-latitude hitchhikers were able to reach greater diversities when cultured at temperate thermal conditions than at typical Southern Ocean temperatures, suggesting the potential for establishment in the Tasmanian coastal environment. Several known invasive species were identified among fouling communities on the hulls of vessels that travel between Hobart and the Southern Ocean. Southward transport of hull fouling species is more likely than northward transport due to the accumulation of assemblages during the winter period spent in the home port of Hobart. This study does not prove that non-indigenous marine species have, or will be, transported and established as a consequence of Antarctic shipping but illustrates that the potential exists. Awareness of the potential risk and simple changes to operating procedures may reduce the chance of introductions in the future. PMID:12586117

  19. A Southern Indian Ocean database of hydrographic profiles obtained with instrumented elephant seals.

    PubMed

    Roquet, Fabien; Williams, Guy; Hindell, Mark A; Harcourt, Rob; McMahon, Clive; Guinet, Christophe; Charrassin, Jean-Benoit; Reverdin, Gilles; Boehme, Lars; Lovell, Phil; Fedak, Mike

    2014-01-01

    The instrumentation of southern elephant seals with satellite-linked CTD tags has offered unique temporal and spatial coverage of the Southern Indian Ocean since 2004. 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. This landmark dataset of around 75,000 temperature and salinity profiles from 20-140 °E, concentrated on the sector between the Kerguelen Islands and Prydz Bay, continues to grow through the coordinated efforts of French and Australian marine research teams. The seal data are quality controlled and calibrated using delayed-mode techniques involving comparisons with other existing profiles as well as cross-comparisons similar to established protocols within the Argo community, with a resulting accuracy of ±0.03 °C in temperature and ±0.05 in salinity or better. The 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. PMID:25977785

  20. A Southern Indian Ocean database of hydrographic profiles obtained with instrumented elephant seals

    PubMed Central

    Roquet, Fabien; Williams, Guy; Hindell, Mark A.; Harcourt, Rob; McMahon, Clive; Guinet, Christophe; Charrassin, Jean-Benoit; Reverdin, Gilles; Boehme, Lars; Lovell, Phil; Fedak, Mike

    2014-01-01

    The instrumentation of southern elephant seals with satellite-linked CTD tags has offered unique temporal and spatial coverage of the Southern Indian Ocean since 2004. 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. This landmark dataset of around 75,000 temperature and salinity profiles from 20–140 °E, concentrated on the sector between the Kerguelen Islands and Prydz Bay, continues to grow through the coordinated efforts of French and Australian marine research teams. The seal data are quality controlled and calibrated using delayed-mode techniques involving comparisons with other existing profiles as well as cross-comparisons similar to established protocols within the Argo community, with a resulting accuracy of ±0.03 °C in temperature and ±0.05 in salinity or better. The 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. PMID:25977785

  1. Investigation of weather anomalies in the low-latitude islands of the Indian Ocean in 1991

    NASA Astrophysics Data System (ADS)

    Réchou, A.; Kirkwood, S.

    2015-07-01

    Temperature, precipitation and sunshine duration measurements at meteorological stations across the southern Indian Ocean have been analysed to try to differentiate the possible influence of the Mount Pinatubo volcanic eruption in the Philippines in June 1991 and the normal weather forcings. During December 1991, precipitation on the tropical islands Glorieuses (11.6° S) and Mayotte (12.8° S) was 4 and 3 times greater, respectively, than the climatological mean (precipitation is greater by more than than twice the standard deviation (SD)). Mean sunshine duration (expressed in sun hours per day) was only 6 h on Mayotte, although the sunshine duration is usually more than 7.5 ± 0.75 h, and on the Glorieuses it was only 5 h, although it is usually 8.5 ± 1 h. Mean and SD of sunshine duration are based on December (1964-2001 for Mayotte, 1966-1999 for the Glorieuses). The Madden-Julian Oscillation (MJO) is shown to correlate best with precipitation in this area. Variability controlling the warm zone on these two islands can be increased by the Indian Ocean Dipole (IOD), El Niño, the quasi-biennial oscillation (QBO) and/or solar activity (sunspot number, SSN). However, temperature records of these two islands show weak dependence on such forcings (temperatures are close to the climatological mean for December). This suggests that such weather forcings have an indirect effect on the precipitation. December 1991 was associated with unusually low values of the MJO index, which favours high rainfall, as well as with El Niño, eastern QBO and high SSN, which favour high variability. It is therefore not clear whether the Mount Pinatubo volcanic eruption had an effect. Since the precipitation anomalies at the Glorieuses and Mayotte are more or less local (Global Precipitation Climatology Project (GPCP) data) and the effect of the Pinatubo volcanic cloud should be more widespread, it seems unlikely that Pinatubo was the cause. Islands at higher southern latitudes (south of

  2. Oceanic crust of the Grenada Basin in the Southern Lesser Antilles Arc Platform

    NASA Astrophysics Data System (ADS)

    Speed, R. C.; Walker, J. A.

    1991-03-01

    Seismic refraction data permit the southern Lesser Antilles arc and surrounding regions to be divided by the velocity of their basement. We propose that high-velocity basement of the arc platform beneath the Grenadine islands and below a part of the Tobago Trough forearc basin is oceanic and continuous and was originally connected with oceanic crust of the Grenada Basin. Low-velocity basements of the Tobago terrane and the arc platform from St. Vincent north lie south and north, respectively, of the high-velocity basement of the arc platform. An oceanic origin of this high-velocity crust in the Grenadines is argued to be more plausible than an origin as unroofed lower arc crust. The segment of probable oceanic crust in the arc platform was greatly uplifted during development of the present island arc, mainly in late Neogene time, relative to the Grenada Basin and Tobago Trough. Accepting the proposition of shallow oceanic crust in the Grenadines, early middle Eocene and possibly older pillow basalts of Mayreau, the oldest rock unit of the southern Lesser Antilles arc platform, may be an exposure of such basement. Major and minor element compositions of Mayreau Basalt are indicative of a spreading rather than arc origin. The stratigraphy of the pillow basalts indicates extrusion in an open marine environment, distant or shielded from sources of arc or continental sediment, followed by a period of pelagic sedimentation above the carbonate compensation depth. The Eocene basalt and pelagic cover formed a relatively deep floor of a marine basin in which arc-derived turbidites and pelagic sediments accumulated over the succeeding 25-30 ma. Such basalts thus indicate a probable spreading origin of the Grenada Basin and an age of cessation of spreading in the region of Mayreau in Eocene time. The configuration of the Eocene basin and the direction of spreading, however, are unknowns. Regional structural relationships imply the spreading was probably backarc, an origin also

  3. Graviry fields of the southern ocean from Geosat data

    NASA Astrophysics Data System (ADS)

    McAdoo, David C.; Marks, Karen M.

    1992-03-01

    In August 1990, the U.S. Navy declassified all Geodetic Mission (GM) radar altimeter data acquired by the Geosat satellite over oceanic regions south of 60°S. We have used these GM data in conjunction with the unclassified, lower-resolution Geosat Exact Repeat Mission (ERM) altimeter data to construct high-resolution gravity fields on a 5-km grid covering the annular region of the southern ocean, which lies between 60°S and 72°S and encircles Antarctica. During the GM a complete mapping of the marine geoid (between 72°S and 72°N) was accomplished. The GM produce more densely spaced ground tracks (typically 2 or 3 km at 60°S) than those of either the ERM or Seasat. Consequently, we were able to use the GM data to map the marine gravity field at a higher resolution than was previously possible using satellite altimeter data. This paper describes the techniques we used to derive these gravity fields and image them. These techniques involve (1) computing along-track sea surface height slopes, (2) gridding of these ascending and descending slopes, (3) converting the slopes to conventional deflections of the vertical, (4) transforming the deflections to gravity anomalies in the frequency domain, and (5) imaging. The resulting images of the marine gravity field reveal much that is new about the seafloor and the tectonic fabric of the southern ocean: a region which includes large expanses of seafloor that have never been surveyed by ships.

  4. Characteristics of regional aerosols: Southern Arizona and eastern Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Prabhakar, Gouri

    Atmospheric aerosols impact the quality of our life in many direct and indirect ways. Inhalation of aerosols can have harmful effects on human health. Aerosols also have climatic impacts by absorbing or scattering solar radiation, or more indirectly through their interactions with clouds. Despite a better understanding of several relevant aerosol properties and processes in the past years, they remain the largest uncertainty in the estimate of global radiative forcing. The uncertainties arise because although aerosols are ubiquitous in the Earth's atmosphere they are highly variable in space, time and their physicochemical properties. This makes in-situ measurements of aerosols vital in our effort towards reducing uncertainties in the estimate of global radiative forcing due to aerosols. This study is an effort to characterize atmospheric aerosols at a regional scale, in southern Arizona and eastern Pacific Ocean, based on ground and airborne observations of aerosols. Metals and metalloids in particles with aerodynamic diameter (Dp) smaller than 2.5 μm are found to be ubiquitous in southern Arizona. The major sources of the elements considered in the study are identified to be crustal dust, smelting/mining activities and fuel combustion. The spatial and temporal variability in the mass concentrations of these elements depend both on the source strength and meteorological conditions. Aircraft measurements of aerosol and cloud properties collected during various field campaigns over the eastern Pacific Ocean are used to study the sources of nitrate in stratocumulus cloud water and the relevant processes. The major sources of nitrate in cloud water in the region are emissions from ships and wildfires. Different pathways for nitrate to enter cloud water and the role of meteorology in these processes are examined. Observations of microphysical properties of ambient aerosols in ship plumes are examined. The study shows that there is an enhancement in the number

  5. A unified history of the ocean around southern Africa

    NASA Astrophysics Data System (ADS)

    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

  6. Observed Trends in Wind Speed over the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Hande, L. B.; Siems, S. T.; Manton, M. J.

    2012-06-01

    Most studies of trends in regional climate focus on temperature, however for maritime environments in particular, changes in the wind are equally important. An analysis of trends in the wind over Macquarie Island is performed with a radio-sonde database spanning nearly four decades. The results indicate that the surface wind speed is increasing, with the trend for the upper levels being less well defined. The surface wind is highly correlated with the upper level winds, and the wind at all levels are moderately correlated with the Southern Annular Mode. ECMWF ERA-Interim reanalysis data shows significant trends in wind speed over several levels, however slightly smaller than trends in the soundings over a similar time period. The correlations in ERA-Interim are similar to those in the soundings. A clustering analysis of the wind reveals four distinct regimes, with a trend towards a regime characterised by strong north westerly winds.

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

    PubMed Central

    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. PMID:26925334

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

    PubMed

    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. PMID:26925334

  9. Applying a New Event Detection Algorithm to an Ocean Bottom Seismometer Dataset Recorded Offshore Southern California

    NASA Astrophysics Data System (ADS)

    Bishop, J.; Kohler, M. D.; Bunn, J.; Chandy, K. M.

    2015-12-01

    A number of active southern California offshore faults are capable of M>6 earthquakes, and the only permanent Southern California Seismic Network stations that can contribute to ongoing, small-magnitude earthquake detection and location are those located on the coastline and islands. To obtain a more detailed picture of the seismicity of the region, an array of 34 ocean bottom seismometers (OBSs) was deployed to record continuous waveform data off the coast of Southern California for 12 months (2010-2011) as part of the ALBACORE (Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment) project. To obtain a local event catalog based on OBS data, we make use of a newly developed data processing platform based on Python. The data processing procedure comprises a multi-step analysis that starts with the identification of significant signals above the time-adjusted noise floor for each sensor. This is followed by a time-dependent statistical estimate of the likelihood of an earthquake based on the aggregated signals in the array. For periods with elevated event likelihood, an adaptive grid-fitting procedure is used that yields candidate earthquake hypocenters with confidence estimates that best match the observed sensor signals. The results are validated with synthetic travel times and manual picks. Using results from ALBACORE, we have created a more complete view of active faulting in the California Borderland.

  10. Effects of Southern Hemisphere Wind Changes on the Meridional Overturning Circulation in Ocean Models.

    PubMed

    Gent, Peter R

    2016-01-01

    Observations show that the Southern Hemisphere zonal wind stress maximum has increased significantly over the past 30 years. Eddy-resolving ocean models show that the resulting increase in the Southern Ocean mean flow meridional overturning circulation (MOC) is partially compensated by an increase in the eddy MOC. This effect can be reproduced in the non-eddy-resolving ocean component of a climate model, providing the eddy parameterization coefficient is variable and not a constant. If the coefficient is a constant, then the Southern Ocean mean MOC change is balanced by an unrealistically large change in the Atlantic Ocean MOC. Southern Ocean eddy compensation means that Southern Hemisphere winds cannot be the dominant mechanism driving midlatitude North Atlantic MOC variability. PMID:26163010

  11. 33 CFR 334.950 - Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean at San Clemente... REGULATIONS § 334.950 Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas. (a) The danger zones. (1) The waters of the Pacific Ocean within an area beginning at China Point...

  12. 33 CFR 334.950 - Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean at San Clemente... REGULATIONS § 334.950 Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas. (a) The danger zones. (1) The waters of the Pacific Ocean within an area beginning at China Point...

  13. 33 CFR 334.1400 - Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Pacific Ocean, at Barbers Point... REGULATIONS § 334.1400 Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area. (a) The area. That portion of the Pacific Ocean lying offshore of Oahu between Ewa Beach and Barbers Point,...

  14. 33 CFR 334.950 - Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean at San Clemente... REGULATIONS § 334.950 Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas. (a) The danger zones. (1) The waters of the Pacific Ocean within an area beginning at China Point...

  15. 33 CFR 334.1400 - Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Pacific Ocean, at Barbers Point... REGULATIONS § 334.1400 Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area. (a) The area. That portion of the Pacific Ocean lying offshore of Oahu between Ewa Beach and Barbers Point,...

  16. 33 CFR 334.1400 - Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Pacific Ocean, at Barbers Point... REGULATIONS § 334.1400 Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area. (a) The area. That portion of the Pacific Ocean lying offshore of Oahu between Ewa Beach and Barbers Point,...

  17. 33 CFR 334.1400 - Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean, at Barbers Point... REGULATIONS § 334.1400 Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area. (a) The area. That portion of the Pacific Ocean lying offshore of Oahu between Ewa Beach and Barbers Point,...

  18. 33 CFR 334.1400 - Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean, at Barbers Point... REGULATIONS § 334.1400 Pacific Ocean, at Barbers Point, Island of Oahu, Hawaii; restricted area. (a) The area. That portion of the Pacific Ocean lying offshore of Oahu between Ewa Beach and Barbers Point,...

  19. 33 CFR 334.950 - Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Pacific Ocean at San Clemente... REGULATIONS § 334.950 Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas. (a) The danger zones. (1) The waters of the Pacific Ocean within an area beginning at China Point...

  20. 33 CFR 334.950 - Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Pacific Ocean at San Clemente... REGULATIONS § 334.950 Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas. (a) The danger zones. (1) The waters of the Pacific Ocean within an area beginning at China Point...

  1. Molecular transformation and degradation of refractory dissolved organic matter in the Atlantic and Southern Ocean

    NASA Astrophysics Data System (ADS)

    Lechtenfeld, Oliver J.; Kattner, Gerhard; Flerus, Ruth; McCallister, S. Leigh; Schmitt-Kopplin, Philippe; Koch, Boris P.

    2014-02-01

    More than 90% of the global ocean dissolved organic carbon (DOC) is refractory, has an average age of 4000-6000 years and a lifespan from months to millennia. The fraction of dissolved organic matter (DOM) that is resistant to degradation is a long-term buffer in the global carbon cycle but its chemical composition, structure, and biochemical formation and degradation mechanisms are still unresolved. We have compiled the most comprehensive molecular dataset of 197 Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses from solid-phase extracted marine DOM covering two major oceans, the Atlantic sector of the Southern Ocean and the East Atlantic Ocean (ranging from 50° N to 70° S). Molecular trends and radiocarbon dating of 34 DOM samples (comprising Δ14C values from -229‰ to -495‰) were combined to model an integrated degradation rate for bulk DOC resulting in a predicted age of >24 ka for the most persistent DOM fraction. First order kinetic degradation rates for 1557 mass peaks indicate that numerous DOM molecules cycle on timescales much longer than the turnover of the bulk DOC pool (estimated residence times of up to ~100 ka) and the range of validity of radiocarbon dating. Changes in elemental composition were determined by assigning molecular formulae to the detected mass peaks. The combination of residence times with molecular information enabled modelling of the average elemental composition of the slowest degrading fraction of the DOM pool. In our dataset, a group of 361 molecular formulae represented the most stable composition in the oceanic environment (“island of stability”). These most persistent compounds encompass only a narrow range of the molecular elemental ratios H/C (average of 1.17 ± 0.13), and O/C (average of 0.52 ± 0.10) and molecular masses (360 ± 28 and 497 ± 51 Da). In the Weddell Sea DOC concentrations in the surface waters were low (46.3 ± 3.3 μM) while the organic radiocarbon was significantly

  2. Insolation-induced mid-Brunhes transition in Southern Ocean ventilation and deep-ocean temperature.

    PubMed

    Yin, Qiuzhen

    2013-02-14

    Glacial-interglacial cycles characterized by long cold periods interrupted by short periods of warmth are the dominant feature of Pleistocene climate, with the relative intensity and duration of past and future interglacials being of particular interest for civilization. The interglacials after 430,000 years ago were characterized by warmer climates and higher atmospheric concentrations of carbon dioxide than the interglacials before, but the cause of this climatic transition (the so-called mid-Brunhes event (MBE)) is unknown. Here I show, on the basis of model simulations, 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 by changes 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 systematic difference in the astronomical parameters between the interglacials before and after 430,000 years ago. Rather than being a real 'event', the apparent MBE seems to have resulted from a series of individual interglacial responses--including notable exceptions to the general pattern--to various combinations of insolation conditions. Consequently, assuming no anthropogenic interference, future interglacials may have pre- or post-MBE characteristics without there being a systematic change in forcings. These findings are a first step towards understanding the magnitude change of the interglacial carbon dioxide concentration around 430

  3. Analysis of the origin of the distribution of CO in the subtropical southern Indian Ocean in 2007

    NASA Astrophysics Data System (ADS)

    Duflot, V.; Dils, B.; Baray, J. L.; de MazièRe, M.; Attié, J. L.; Vanhaelewyn, G.; Senten, C.; Vigouroux, C.; Clain, G.; Delmas, R.

    2010-11-01

    We show carbon monoxide (CO) distributions at different vertical levels over the subtropical southern Indian Ocean, analyzing an observation campaign using Fourier transform infrared (FTIR) solar absorption spectrometry performed in 2007 at Reunion Island (21°S, 55°E). The CO pollution levels detected by the FTIR measurements during the campaign show a doubling of the CO total columns during the Southern Hemisphere biomass burning season. Using correlative data from the Measurement of Pollution in the Troposphere instrument and back trajectories analyses, we show that the potential primary sources for CO throughout the troposphere in 2007 are southern Africa (June-August) and South America (September-October). A secondary potential contribution from Southeast Asia and Indonesia-Malaysia was identified in the upper troposphere, especially in July and September. We examine the relation between the Asian monsoon anticyclone seasonal cycle and this result. We also investigate the relative contribution of different areas across the globe to the CO concentration in the subtropical southern Indian Ocean in 2007 using backward simulations combining the Lagrangian model FLEXPART 6.2, the Global Fire Emissions Database (GFEDv2.1) and the Emission Database for Global Atmospheric Research (EDGARv3.2-FT2000). We confirm the predominance of the African and South American contributions in the CO concentration in the southern subtropical Indian Ocean below 11 km. We show that CO transported from Australia makes only a small contribution to the total CO concentration observed over Reunion Island, and that the long-range transport of CO coming from Southeast Asia and Indonesia-Malaysia is important, especially from June until September in the upper troposphere.

  4. The Southern Ocean as a constraint to reduce uncertainty in future ocean carbon sinks

    NASA Astrophysics Data System (ADS)

    Kessler, A.; Tjiputra, J.

    2016-04-01

    Earth system model (ESM) simulations exhibit large biases compares to observation-based estimates of the present ocean CO2 sink. The inter-model spread in projections increases nearly 2-fold by the end of the 21st century and therefore contributes significantly to the uncertainty of future climate projections. In this study, the Southern Ocean (SO) is shown to be one of the hot-spot regions for future uptake of anthropogenic CO2, characterized by both the solubility pump and biologically mediated carbon drawdown in the spring and summer. We show, by analyzing a suite of fully interactive ESMs simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5) over the 21st century under the high-CO2 Representative Concentration Pathway (RCP) 8.5 scenario, that the SO is the only region where the atmospheric CO2 uptake rate continues to increase toward the end of the 21st century. Furthermore, our study discovers a strong inter-model link between the contemporary CO2 uptake in the Southern Ocean and the projected global cumulated uptake over the 21st century. This strong correlation suggests that models with low (high) carbon uptake rate in the contemporary SO tend to simulate low (high) uptake rate in the future. Nevertheless, our analysis also shows that none of the models fully capture the observed biophysical mechanisms governing the CO2 fluxes in the SO. The inter-model spread for the contemporary CO2 uptake in the Southern Ocean is attributed to the variations in the simulated seasonal cycle of surface pCO2. Two groups of model behavior have been identified. The first one simulates anomalously strong SO carbon uptake, generally due to both too strong a net primary production and too low a surface pCO2 in December-January. The second group simulates an opposite CO2 flux seasonal phase, which is driven mainly by the bias in the sea surface temperature variability. We show that these biases are persistent throughout the 21st century, which highlights the

  5. Controlling high-latitude Southern Ocean convection in climate models

    NASA Astrophysics Data System (ADS)

    Stössel, Achim; Notz, Dirk; Haumann, F. Alexander; Haak, Helmuth; Jungclaus, Johann; Mikolajewicz, Uwe

    2015-02-01

    Earth System Models (ESMs) generally suffer from a poor simulation of the High-Latitude Southern Ocean (HLSO). Here we aim at a better understanding of the shortcomings by investigating the sensitivity of the HLSO to the external freshwater flux and the horizontal resolution in forced and coupled simulations with the Max-Planck-Institute Ocean Model (MPIOM). Forced experiments reveal an immediate reduction of open-ocean convection with additional freshwater input. The latter leads to a remarkably realistic simulation of the distinct water-mass structure in the central Weddell Sea featuring a temperature maximum of +0.5 °C at 250 m depth. Similar, but more modest improvements occur over a time span of 40 years after switching from a forced to a coupled simulation with an eddy-resolving version of MPIOM. The switch is accompanied with pronounced changes of the external freshwater flux and the wind field, as well as a more realistic heat flux due to coupling. Similar to the forced freshwater-flux experiments, a heat reservoir develops at depth, which in turn decreases the vertically integrated density of the HLSO and reduces the Antarctic Circumpolar Current to rather realistic values. Coupling with a higher resolution version of the atmosphere model (ECHAM6) yields distinct improvements of the HLSO water-mass structure and sea-ice cover. While the coupled simulations reveal a realistic amount of Antarctic runoff, its distribution appears too concentrated along the coast. Spreading the runoff over a wider region, as suggested in earlier studies to mimic the effect of freshwater transport through icebergs, also leads to noticeable improvements of the HLSO water-mass properties, predominantly along the coast. This suggests that the spread of the runoff improves the representation of Antarctic Bottom Water formation through enhanced near-boundary convection rather than weakened open-ocean convection.

  6. Observed and Modeled Trends in Southern Ocean Sea Ice

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    2003-01-01

    Conceptual models and global climate model (GCM) simulations have both indicated the likelihood of an enhanced sensitivity to climate change in the polar regions, derived from the positive feedbacks brought about by the polar abundance of snow and ice surfaces. Some models further indicate that the changes in the polar regions can have a significant impact globally. For instance, 37% of the temperature sensitivity to a doubling of atmospheric CO2 in simulations with the GCM of the Goddard Institute for Space Studies (GISS) is attributable exclusively to inclusion of sea ice variations in the model calculations. Both sea ice thickness and sea ice extent decrease markedly in the doubled CO, case, thereby allowing the ice feedbacks to occur. Stand-alone sea ice models have shown Southern Ocean hemispherically averaged winter ice-edge retreats of 1.4 deg latitude for each 1 K increase in atmospheric temperatures. Observations, however, show a much more varied Southern Ocean ice cover, both spatially and temporally, than many of the modeled expectations. In fact, the satellite passive-microwave record of Southern Ocean sea ice since late 1978 has revealed overall increases rather than decreases in ice extents, with ice extent trends on the order of 11,000 sq km/year. When broken down spatially, the positive trends are strongest in the Ross Sea, while the trends are negative in the Bellingshausen/Amundsen Seas. Greater spatial detail can be obtained by examining trends in the length of the sea ice season, and those trends show a coherent picture of shortening sea ice seasons throughout almost the entire Bellingshausen and Amundsen Seas to the west of the Antarctic Peninsula and in the far western Weddell Sea immediately to the east of the Peninsula, with lengthening sea ice seasons around much of the rest of the continent. This pattern corresponds well with the spatial pattern of temperature trends, as the Peninsula region is the one region in the Antarctic with a strong

  7. Hurricane Sandy Washover Deposits on Southern Long Beach Island, NJ

    NASA Astrophysics Data System (ADS)

    Bishop, J. M.; Richmond, B. M.; Kane, H. H.; Lunghino, B.

    2015-12-01

    Hurricane Sandy washover deposits were investigated at Forsyth National Wildlife Refuge (FNWR) on Southern Long Beach Island, New Jersey in order to map deposit thickness and characterize the sedimentary deposits. FNWR was chosen as a field area because there has been relatively little anthropogenic shoreline modification since washover deposition from Hurricane Sandy. Sediment, elevation, and geophysical data were collected during the April 2015 field campaign, approximately two and a half years after the storm. Sediment deposit data included trenches, stratigraphic descriptions, bulk sediment samples, push cores, Russian cores, and photos. Computed tomography (CT) scanning was conducted on push cores in order to acquire high resolution imaging of density, grain size, and sedimentary structure. Profiles of washover elevation were measured using Differential GPS with Real Time Kinematic processing. Ground Penetrating Radar data was collected to image the depth of the deposit and identify sedimentary structures. These data sets are compared to pre- and post -Sandy lidar surveys in order to determine post-Sandy modification in the two and a half years following the hurricane. We compare sediment thickness and sedimentary characteristics to hurricane Sandy deposits elsewhere along the U.S. eastern seaboard and to tsunami deposits.

  8. Southern Ocean and Antarctic Peninsula Temperatures During Critical Climate Transitions of the Cenozoic Constrained by Clumped Isotope Thermometry

    NASA Astrophysics Data System (ADS)

    Dill, R.; Eagle, R.; Henry, D.; Praskin, S.; Mering, J. A.; Petryshyn, V. A.; Priyadarshi, A.; Rycroft, L.; Vollmer, T.; Chea, Y.; Dix, J.; Aguilar, A.; Supakkul, K.; Tran, B.; Lipel, Z.; Flores, S.; Riesselman, C. R.; Taviani, M.; Marenssi, S.; Harwood, D. M.; Lunt, D. J.; Valdes, P. J.; Meckler, A. N.; Tripati, A.

    2014-12-01

    The Southern Ocean and Antarctica play fundamental roles in the global climate system. These polar regions are a major area for the net loss of heat to space. Ice storage on Antarctica also influences the global water cycle. Through upwelling of deep waters, the Southern Ocean is an important regulator of atmospheric CO2. To better constrain the evolution of paleoclimate in this region over major climate transitions of the Cenozoic, we estimated ocean temperatures using clumped isotope thermometry. Clumped isotope thermometry is a thermodynamically-based stable isotope thermometer that can be used to constrain temperatures previously estimated using other paleothermometers (which in turn leads to constraints on ice volume), as it allows the exclusion of water isotope composition from temperature estimates (unlike the δ18O thermometer). We previously have published calibrations for foraminifera and mollusks, two of the major archives used in this study. Critical transitions investigated include the Eocene-Oligocene boundary and the Middle Miocene Climate Transition. Study sites include Seymour Island (Antarctic Peninsula), ANDRILL (Southern McMurdo Sounds), Ocean Drilling Program (ODP) Sites 689/690 (Weddell Sea), and ODP 744 (Kerguelen Plateau). Results will be compared to GCM output.

  9. Paleoceanography and Paleoclimatology of the Southern Ocean: A Synthesis of Three Decades of Scientific Ocean Drilling

    NASA Astrophysics Data System (ADS)

    Warnke, D. A.; Filippelli, G.; Flores, J.; Marchitto, T. M.

    2004-12-01

    A Workshop on " Paleoceanography and Paleoclimatology of the Southern Ocean: A Synthesis of Three Decades of Scientific Ocean Drilling" Jan. 21-23, 2005 Boulder, CO Co-Convenors: D. Warnke, G. Filippelli, J.-A. Flores, T. Marchitto One of the greatest successes of the Ocean Drilling Program has been the concerted drilling efforts and exciting results recovered from the Southern Ocean (SO), which has been the focus of ten DSDP/ODP drilling legs. The SO is a critical component in the development and persistence of Antarctic glaciation, is a sensitive mixing pool of global water masses, a locus of high biological sedimentation, and contains high resolution records of climate forcing and response. As such, it is one of the most important oceanographic regions in the world. It is now an important time to mine the rich results from scientific ocean drilling over the past several decades and develop a scientific framework for future ocean drilling in this region. The focus of this Synthesis Workshop will be on the biogeochemical history of the SO, including: · Productivity proxies, rates, records, variations, and role of climate · Sedimentary records of organic carbon, calcium, silica, nutrients, and biogenic proxies: The role of the SO as a biogeochemical sink · Development and dynamics of the APFZ · Thermal structure and evolution of the SO · The role of limiting nutrients The overall goal to integrate the various proxies into a coherent paleoceanographic picture. Such a goal will help to synthesize several decades of scientific ocean drilling in the SO, and will likely bring to the forefront the as-yet-unanswered questions about the biogeochemical history of this important oceanic system. With this goal in mind, workshop participants will submit of a short (~250 word) abstract as the Workshop application, commit to presenting a poster at the workshop based on this abstract, and contribute to one or more manuscripts that will be published after the workshop, likely

  10. Coastal ocean transport patterns in the central Southern California Bight

    USGS Publications Warehouse

    Noble, M.A.; Rosenberger, K.J.; Hamilton, P.; Xu, J. P.

    2009-01-01

    In the past decade, several large programs that monitor currents and transport patterns for periods from a few months to a few years were conducted by a consortium of university, federal, state, and municipal agencies in the central Southern California Bight, a heavily urbanized section of the coastal ocean off the west coast of the United States encompassing Santa Monica Bay, San Pedro Bay, and the Palos Verdes shelf. These programs were designed in part to determine how alongshelf and cross-shelf currents move sediments, pollutants, and suspended material through the region. Analysis of the data sets showed that the current patterns in this portion of the Bight have distinct changes in frequency and amplitude with location, in part because the topography of the shelf and upper slope varies rapidly over small spatial scales. However, because the mean, subtidal, and tidal-current patterns in any particular location were reasonably stable with time, one could determine a regional pattern for these current fields in the central Southern California Bight even though measurements at the various locations were obtained at different times. In particular, because the mean near-surface flows over the San Pedro and Palos Verdes shelves are divergent, near-surface waters from the upper slope tend to carry suspended material onto the shelf in the northwestern portion of San Pedro Bay. Water and suspended material are also carried off the shelf by the mean and subtidal flow fields in places where the orientation of the shelf break changes abruptly. The barotropic tidal currents in the central Southern California Bight flow primarily alongshore, but they have pronounced amplitude variations over relatively small changes in alongshelf location that are not totally predicted by numerical tidal models. Nonlinear internal tides and internal bores at tidal frequencies are oriented more across the shelf. They do not have a uniform transport direction, since they move fine sediment

  11. Recycling of geochemically heterogenous oceanic crust: Significance for the origin of ocean island basalts

    NASA Astrophysics Data System (ADS)

    Duggen, S.; Hoernle, K.; Hauff, F.; Park, S.-H.; Geldmacher, J.

    2009-04-01

    Explaining the isotopic signature and origin of ocean island basalts (OIBs) is a challenge in Earth sciences. There is general agreement that lithospheric material, recycled into the Earth's mantle, is involved in the mantle sources of OIBs. The relative roles, however, of 1) subducted marine sediments, 2) altered oceanic basaltic crust (AOC), 3) oceanic lithospheric mantle and/or 4) delaminated metasomatised subcontinental lithosphere and continental lower crust, however, are much debated. We present results from geochemical modeling in the Sr-Nd-Pb-isotope space following a new approach that takes into account the trace element and isotope heterogeneity of subducted oceanic crust (sediments + AOC). By means of backward and forward modeling, we examine how a geochemically heterogeneous package of oceanic crust may evolve in terms of Sr-Nd-Pb-isotopic composition through time and compare the results with present day radiogenic isotope ratios of OIBs. Our study suggests that recycling of AOC, modified during the subduction process, and stored in the Earth's mantle for several hundreds of millions of years can explain the Sr-Nd-Pb-isotopic composition of OIBs with relatively high Nd-isotope ratios that form elongated fields along or below the Northern Hemisphere Reference Line (NHRL) in the Pb-isotopic diagrams (e.g. Canaries, Galapagos, Iceland, Madeira). Explaining the origin of OIBs with relatively low Nd-isotope ratios and Pb-isotopic composition above the NHRL, and thus geochemical affinity to enriched mantle (EM) components (e.g. Pitcairn, Tristan, Samoa), however, seems to also require recycling of other lithospheric material such as subducted sediments, lower continental crust and/or subcontinental lithosphere.

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

    PubMed

    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. PMID:22355636

  13. Extraordinarily high biomass benthic community on Southern Ocean seamounts

    PubMed Central

    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. PMID:22355636

  14. Automated ocean color product validation for the Southern California Bight

    NASA Astrophysics Data System (ADS)

    Davis, Curtiss O.; Tufillaro, Nicholas; Jones, Burt; Arnone, Robert

    2012-06-01

    Automated match ups allow us to maintain and improve the products of current satellite ocean color sensors (MODIS, MERIS), and new sensors (VIIRS). As part of the VIIRS mission preparation, we have created a web based automated match up tool that provides access to searchable fields for date, site, and products, and creates match-ups between satellite (MODIS, MERIS, VIIRS), and in-situ measurements (HyperPRO and SeaPRISM). The back end of the system is a 'mySQL' database, and the front end is a `php' web portal with pull down menus for searchable fields. Based on selections, graphics are generated showing match-ups and statistics, and ascii files are created for downloads for the matchup data. Examples are shown for matching the satellite data with the data from Platform Eureka SeaPRISM off L.A. Harbor in the Southern California Bight.

  15. Phytoplankton and light limitation in the Southern Ocean: Learning from high-nutrient, high-chlorophyll areas

    NASA Astrophysics Data System (ADS)

    Venables, Hugh; Moore, C. Mark

    2010-02-01

    Most of the Southern Ocean is a high-nutrient, low-chlorophyll (HNLC) area. There are exceptions to this situation downstream of some of the islands, where iron from the islands or surrounding shallow plateau fertilizes the mixed layer and causes a phytoplankton bloom in spring and summer. The main locations where this occurs are downstream of the South Georgia, Crozet, and Kerguelen islands. Data on mixed layer depths from Argo float profiles together with Sea-viewing Wide Field-of-view Sensor chlorophyll a (chl a) and photosynthetically available radiation from these high-nutrient, high-chlorophyll (HNHC) areas are combined to study the effects of mixed layer-averaged light availability on phytoplankton concentrations in areas where iron limitation has been lifted. The results of this analysis are then transferred to HNLC areas to assess the potential importance of light limitation through the year. We conclude that light limitation does not significantly constrain the annual integrated standing stock of chl a in the HNLC Southern Ocean.

  16. The influence of Southern Ocean winds on the North Atlantic carbon sink

    NASA Astrophysics Data System (ADS)

    Bronselaer, Ben; Zanna, Laure; Munday, David R.; Lowe, Jason

    2016-06-01

    Observed and predicted increases in Southern Ocean winds are thought to upwell deep ocean carbon and increase atmospheric CO2. However, Southern Ocean dynamics affect biogeochemistry and circulation pathways on a global scale. Using idealized Massachusetts Institute of Technology General Circulation Model (MITgcm) simulations, we demonstrate that an increase in Southern Ocean winds reduces the carbon sink in the North Atlantic subpolar gyre. The increase in atmospheric CO2 due to the reduction of the North Atlantic carbon sink is shown to be of the same magnitude as the increase in atmospheric CO2 due to Southern Ocean outgassing. The mechanism can be described as follows: The increase in Southern Ocean winds leads to an increase in upper ocean northward nutrient transport. Biological productivity is therefore enhanced in the tropics, which alters the chemistry of the subthermocline waters that are ultimately upwelled in the subpolar gyre. The results demonstrate the influence of Southern Ocean winds on the North Atlantic carbon sink and show that the effect of Southern Ocean winds on atmospheric CO2 is likely twice as large as previously thought in past, present, and future climates.

  17. A possible 20th-century slowdown of southern ocean deep water formation

    PubMed

    Broecker; Sutherland; Peng

    1999-11-01

    Chlorofluorocarbon-11 inventories for the deep Southern Ocean appear to confirm physical oceanographic and geochemical studies in the Southern Ocean, which suggest that no more than 5 x 10(6) cubic meters per second of ventilated deep water is currently being produced. This result conflicts with conclusions based on the distributions of the carbon-14/carbon ratio and a quasi-conservative property, PO(4)(*), in the deep sea, which seem to require an average of about 15 x 10(6) cubic meters per second of Southern Ocean deep ventilation over about the past 800 years. A major reduction in Southern Ocean deep water production during the 20th century (from high rates during the Little Ice Age) may explain this apparent discordance. If this is true, a seesawing of deep water production between the northern Atlantic and Southern oceans may lie at the heart of the 1500-year ice-rafting cycle. PMID:10550046

  18. Variability and trends in Southern Ocean eddy activity in 1/12° ocean model simulations

    NASA Astrophysics Data System (ADS)

    Patara, Lavinia; Böning, Claus W.; Biastoch, Arne

    2016-05-01

    The response of eddy kinetic energy (EKE) to the strengthening of Southern Hemisphere winds occurring since the 1950s is investigated with a global ocean model having a resolution of 1/12° in the Antarctic Circumpolar Current domain. The simulations expose regional differences in the relative importance of stochastic and wind-related contributions to interannual EKE changes. In the Pacific and Indian sectors the model captures the EKE variability observed since 1993 and confirms previous hypotheses of a lagged response to regional wind stress anomalies. Here the multidecadal trend in wind stress is reflected in an increase in EKE typically exceeding 5 cm2 s-2 decade-1. In the western Atlantic, EKE variability is mostly stochastic, is weakly correlated with wind fluctuations, and its multidecadal trends are close to zero. The nonuniform distribution of wind-related changes in the eddy activity could affect the regional patterns of ocean circulation and biogeochemical responses to future climate change.

  19. Southern Ocean Seasonal Net Production from Satellite, Atmosphere, and Ocean Data Sets

    NASA Technical Reports Server (NTRS)

    Keeling, Ralph F.; Campbell, J. (Technical Monitor)

    2002-01-01

    A new climatology of monthly air-sea O2 flux was developed using the net air-sea heat flux as a template for spatial and temporal interpolation of sparse hydrographic data. The climatology improves upon the previous climatology of Najjar and Keeling in the Southern Hemisphere, where the heat-based approach helps to overcome limitations due to sparse data coverage. The climatology is used to make comparisons with productivity derived from CZCS images. The climatology is also used in support of an investigation of the plausible impact of recent global warming an oceanic O2 inventories.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Performance comparison of mid-aperture broadband arrays at an ocean island and in the deep ocean

    NASA Astrophysics Data System (ADS)

    Hannemann, Katrin; Krüger, Frank; Dahm, Torsten

    2013-04-01

    Between 2011 and 2012, three mid-aperture broadband arrays were deployed on the island of Madeira, in western Portugal, and north of the Gloria fault in the Mid Atlantic within the DOCTAR (Deep Ocean Test ARray) project. Here, we compare performance parameters for the ocean island array on Madeira and the deep ocean array. The Madeira array consists of 24 temporary stations (12 broadband stations (8 Guralp 60s & 4 STS2), 12 temporary LE3D 5s stations). The mean inter-station distance is about 5 km and the array has an aperture of about 20 by 40 km on the island of Madeira if the broadband station(STS2) on the nearby island of Desertas is excluded. Furthermore, there are 3 permanent stations installed on Madeira (one Guralp 120s and 2 LE3D 5s) and 2 on the neighbouring island Porto Santo (one Guralp 120s and one LE3D 5S). The deep ocean array consists of 12 ocean bottom stations (broadband seismometer (Guralp 60s) combined with a HTI hydrophone (DEPAS type instruments)) and was deployed at the sea floor close to the Gloria fault between 5000 m and 4000 m water depth. The inter-station distance was about 10 km and the aperture about 70 km. One purpose of the experiment is to test the possible advantage of ocean bottom arrays in comparison to ocean island installations. Therefore, we compare different aspects: (1) the experimental effort and the specific problems of data processing (e.g. data loss, clock drift and station location problematic in case of the deep ocean array). Special emphasis will be given to the orientation of three component stations by waveform comparison methods and results from the use of a portable Gyrocompass on Madeira. (2) the ambient noise spectra as a function of frequency and time, (3) examples of fk analysis and the specific problems on the ocean floor and volcanic, oceanic islands (topography and scattering effects). (4) detection thresholds and frequency content of local and regional events. The presentation finally gives our

  2. The effects of natural iron fertilisation on deep-sea ecology: the Crozet Plateau, Southern Indian Ocean.

    PubMed

    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. PMID:21695118

  3. The Effects of Natural Iron Fertilisation on Deep-Sea Ecology: The Crozet Plateau, Southern Indian Ocean

    PubMed Central

    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 CO2, 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. PMID:21695118

  4. Millennial-scale sea ice variability in the southern Indian Ocean during the last glacial

    NASA Astrophysics Data System (ADS)

    Ikehara, M.; Katsuki, K.; Yamane, M.; Yokoyama, Y.

    2014-12-01

    The Southern Ocean has played an important role in the evolution of the global climate system. Sea ice coverage on sea surface strongly affects the climate of the Southern Hemisphere through its impacts on the energy and gas budget, on the atmospheric circulation, on the hydrological cycle, and on the biological productivity. In this study, we have conducted fundamental analyses of ice-rafted debris (IRD) and diatom assemblage to reveal a rapid change of sea ice distribution in the glacial southern Indian Ocean. Piston cores COR-1bPC and DCR-1PC were collected from the Conrad Rise and Del Caño Rise, Indian sector of the Southern Ocean. Age models of the cores were established by radiocarbon dating and oxygen isotope stratigraphy of planktic and benthic foraminifers. Records of IRD concentration suggest millennial-scale pulses of IRD delivery during the last glacial period. The depositions of rock-fragment IRD excluding volcanic glass and pumice were associated with increasing of sea-ice diatoms, suggesting that the millennial-scale events of cooling and sea-ice expansion were occurred in the southern Indian Ocean during the last glacial period. Provenance study of IRD grains suggest that the source of IRD in the southern Indian Ocean was mainly volcanic arc in the South Atlantic, based on chemical compositions of rock-fragment IRD grains. Thus prominent IRD layers in the glacial Southern Ocean suggest episodes of sea ice expansion and cooling in the Indian sectors of the Southern Ocean.

  5. Impact of Intrathermocline eddies on seamount and oceanic island off Central Chile: Observation and modeling

    NASA Astrophysics Data System (ADS)

    Hormazabal, Samuel; Morales, Carmen; Cornejo, Marcela; Bento, Joaquim; Valencia, Luis; Auger, Pierre; Rodriguez, Angel; Correa, Marco; Anabalón, Valeria; Silva, Nelson

    2016-04-01

    In the Southeast Pacific, oceanographic processes that sustain the biological production necessary to maintain the ecosystems associated to seamounts and oceanic islands are still poorly understood. Recent studies suggest that the interaction of mesoscale and submesoescale eddies with oceanic islands and seamounts could be playing an important role in the time-space variability of primary production. In this work, research cruises, satellite data and Regional Ocean Modeling System (ROMS) results have been used to describe the main characteristics of intrathermocline eddies (ITE) and their impact on the Juan Fernández archipelago (JFA), off central Chile. The JFA is located off the coast of central Chile (33°S), and is composed of three main islands: Robinson Crusoe (RC), Alejandro Selkirk (AS) and Santa Clara (SC). Between the RC and AS are located the westernmost seamounts (JF6 and JF5) of the Juan Fernández archipelago. Satellite altimetry data (sea surface height from AVISO) were used to detect and track mesoscale eddies through eddy-tracking algorithm. Physical, chemical and biological parameters as temperature, salinity, dissolved oxygen and fluorescence were measured in the water column at JF5 and JF6, and along the coast off central Chile (30-40°S). Results from the research cruise exhibit the interaction between an ITE and the seamount JF6. Eddy-tracking results showed that the ITE observed at the JF6 was formed at the coast off central-southern Chile, traveled ~900 km seaward and after ~9 months reached the JF5 and JF6 region. Observations along the Chilean coast confirmed that the coast corresponds to the formation area of the observed ITE. In this region, ITEs are represented by subsurface lenses (~100 km diameter; 400 m thickness) of homogeneous salinity, nutrient rich and oxygen-poor equatorial subsurface water mass (ESSW) which is transported poleward by the Peru-Chile undercurrent in the coastal band and seaward by ITEs. The effect of ITEs on the

  6. Salp distribution and size composition in the Atlantic sector of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    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.

  7. Dissolved organic carbon in the deep Southern Ocean: Local versus distant controls

    NASA Astrophysics Data System (ADS)

    Bercovici, Sarah K.; Hansell, Dennis A.

    2016-02-01

    The global ocean contains a massive reservoir (662 ± 32 Pg C) of dissolved organic carbon (DOC), and its dynamics, particularly in the deepest zones, are only slowly being understood. DOC in the deep ocean is ubiquitously low in concentration (~35 to 48 µmol kg-1) and aged (4000 to 6000 years), persisting for multiple meridional overturning circulations. Deep waters relatively enriched in DOC form in the North Atlantic, migrate to the Southern Ocean to mix with waters from Antarctic shelves and the deep Pacific and Indian Oceans, in turn forming the voluminous waters of the Circumpolar Deep Water. Here we seek evidence for local (autochthonous) versus distant (allochthonous) processes in determining the distribution of DOC in the deep Southern Ocean. Prior analyses on DOC in the deep Southern Ocean have conflicted, describing both conservative and nonconservative traits: the deep DOC field has been reported as uniform in distribution, yet local inputs have been suggested as quantitatively important. We use multiple approaches (multiple linear regression, mass transport, and mass balance calculations) with data from Climate Variability and Predictability Repeat Hydrography sections to evaluate the system. We find that DOC concentrations in the deep Southern Ocean largely reflect the conservative mixing of the several deep waters entering the system from the north. Mass balance suggests that the relatively depleted DOC radiocarbon content in the deep Southern Ocean is a conserved property as well. These analyses advance our understanding of the controls on the DOC reservoir of the Southern Ocean.

  8. Hydrogeology of Southern Cumberland Island, Georgia. Kings Bay Environmental Monitoring Program Cumberland Island national seashore, 1990. Research report

    SciTech Connect

    Wilson, S.K.

    1991-01-01

    The aqueous geochemistry of three aquifers at a 9-square mile study site on the southern end of Cumberland Island, Georgia was investigated at 10 wells on the southern end of the island. The geochemistry of the surficial aquifer varied spatially across the island. The ground water types in the surficial aquifer ranged from sodium-chloride to calcium-bicarbonate, depending on the location. A zone of dispersion associated with the freshwater-saltwater interface was encountered in the Pliocene-Miocene age aquifer and the Miocena-age sand aquifer, but was not encountered in the surficial aquifer. The zone of dispersion resulted from mixing of fresh carbonate ground water seawater. The freshwater region of the zone of dispersion (3%-5% seawater) was characterized by a calcium-chloride water type which likely resulted from freshwater-seawater mixing, calcium carbonate dissolution, and reverse ion exchange.

  9. Constraints on Multilayered Anisotropy beneath Ocean Islands from Harmonic Decomposition of Receiver Functions

    NASA Astrophysics Data System (ADS)

    Park, J. J.; Olugboji, T. M.

    2013-12-01

    Receiver functions have been used to provide, with improved resolution, velocity structure in the crust and upper mantle for oceans and continents. For oceanic regions, receiver function results are only possible were there is station coverage - ocean island stations and ocean bottom seismometers. Receiver function studies of oceanic crustal and upper mantle structure have provided constraints on Moho depth, lithosphere-asthenosphere boundary depth, and show evidence for magmatic underplating. Until recently, these receiver functions have focused on the radial RFs, neglecting information available from transverse RFs. We provide new results that suggest the prevalence of multi-layered crustal anisotropy using azimuthal variation in the amplitudes of radial and transverse receiver functions, reconstructed via harmonic decomposition. The harmonic components give information on the dip and trend of the axis of symmetry within the anisotropic layers above and below interfaces that generate Ps converted waves. Information from preliminary study of ten ocean island stations shows that azimuthal RF variation is largely two-lobed for most of the ocean-island stations, consistent with anisotropy with a tilted symmetry axis in the oceanic crust, including the underplated layers. Using sequential H-K stacks to model the isotropic velocity and the number of layers, we can guide harmonic decomposition to specify the presence and orientation of anisotropy within the specific layers. We will use this to evaluate hypothetical models for ocean-island crustal fabric.

  10. Late Cretaceous and Eocene volcanism in the southern Line Islands and implications for hotspot theory

    NASA Astrophysics Data System (ADS)

    Haggerty, Janet A.; Schlanger, Seymour O.; Premoli Silva, Isabella

    1982-08-01

    Rocks dredged from a seamount 100 km northwest of Caroline Island, at the southern end of the Line Islands chain, contain Late Cretaceous fossils associated with volcanic debris. This association is evidence for the existence of a reef-bearing volcanic edifice with a minimum age of Late Cretaceous, 70 to 75 m.y., near Caroline Island. With the discovery of this seamount, the known occurrences of Late Cretaceous, reef-capped, volcanic edifices now extend a distance of 2,500 km, from Deep Sea Drilling Project Site 165 to 100 km northwest of Caroline Island. The apparent synchroneity of Late Cretaceous volcanism over this distance argues against the proposition that a single hotspot of the Hawaiian-Emperor type produced the Line Islands chain. Biochronologic data from the Line Islands indicate that the chain is not the temporal equivalent of the Emperor chain. Volcanic edifices of Cretaceous age are now known to extend from the Line Islands through the Mid-Pacific Mountains to the Marshall Islands and the western margin of the Pacific plate from Japan to the Marianas. A volcanic event occurred in the southern Line Islands during middle Eocene time; Eocene sediments were engulfed and altered by a volcanic eruption. The occurrence of both Cretaceous and Eocene volcanism in the southern Line Islands indicates that the history of the Line Islands is similar to that of the Marshall Islands. *Present addresses: (Haggerty) Department of Geosciences, University of Tulsa, Tulsa, Oklahoma 74104; (Schlanger) Department of Geological Sciences, Northwestern University, Evanston, Illinois 60201