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Sample records for nw african upwelling

  1. Modelling an alkenone-like proxy record in the NW African upwelling

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    X. Giraud

    2006-01-01

    Full Text Available A regional biogeochemical model is applied to the NW African coastal upwelling between 19° N and 27° N to investigate how a water temperature proxy, alkenones, are produced at the sea surface and recorded in the slope sediments. The biogeochemical model has two phytoplankton groups: an alkenone producer group, considered to be coccolithophores, and a group comprising other phytoplankton. The Regional Ocean Modelling System (ROMS is used to simulate the ocean circulation and takes advantage of the Adaptive Grid Refinement in Fortran (AGRIF package to set up an embedded griding system. In the simulations the alkenone temperature records in the sediments are between 1.1 and 2.3°C colder than the annual mean SSTs. Despite the seasonality of the coccolithophore production, this temperature difference is not mainly due to a seasonal bias, nor to the lateral advection of phytoplankton and phytodetritus seaward from the cold near-shore waters, but to the production depth of the coccolithophores. If coretop alkenone temperatures are effectively recording the annual mean SSTs, the amount of alkenone produced must vary among the coccolithophores in the water column and depend on physiological factors (e.g. growth rate, nutrient stress.

  2. Methane emissions from the upwelling area off Mauritania (NW Africa

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    A. Kock

    2008-08-01

    Full Text Available Coastal upwelling regions have been identified as sites of enhanced CH4 emissions to the atmosphere. The coastal upwelling area off Mauritania (NW Africa is one of the most biologically productive regions of the world's ocean but its CH4 emissions have not been quantified so far. More than 1000 measurements of atmospheric and dissolved CH4 in the surface layer in the upwelling area off Mauritania were performed as part of the German SOPRAN (Surface Ocean Processes in the Anthropocene study during two cruises in March/April 2005 (P320/1 and February 2007 (P348. During P348 enhanced CH4 saturations of up to 200% were found close to the coast and were associated with upwelling of South Atlantic Central Water. An area-weighted, seasonally adjusted estimate yielded overall annual CH4 emissions in the range from 1.6 to 2.9 Gg CH4. Thus the upwelling area off Mauritania represents a regional hot spot of CH4 emissions but seems to be of minor importance for the global oceanic CH4 emissions.

  3. Spatial and temporal variability in coccolithophore abundance and distribution in the NW Iberian coastal upwelling system

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    Ausín, Blanca; Zúñiga, Diana; Flores, Jose A.; Cavaleiro, Catarina; Froján, María; Villacieros-Robineau, Nicolás; Alonso-Pérez, Fernando; Arbones, Belén; Santos, Celia; de la Granda, Francisco; Castro, Carmen G.; Abrantes, Fátima; Eglinton, Timothy I.; Salgueiro, Emilia

    2018-01-01

    A systematic investigation of the spatial and temporal variability in coccolithophore abundance and distribution through the water column of the NW Iberian coastal upwelling system was performed. From July 2011 to June 2012, monthly sampling at various water depths was conducted at two parallel stations located at 42° N. Total coccosphere abundance was higher at the outer-shelf station, where warmer, nutrient-depleted waters favoured coccolithophore rather than phytoplanktonic diatom blooms, which are known to dominate the inner-shelf location. In seasonal terms, higher coccosphere and coccolith abundances were registered at both stations during upwelling seasons, coinciding with high irradiance levels. This was typically in conjunction with stratified, nutrient-poor conditions (i.e. relaxing upwelling conditions). However, it also occurred during some upwelling events of colder, nutrient-rich subsurface waters onto the continental shelf. Minimum abundances were generally found during downwelling periods, with unexpectedly high coccolith abundance registered in subsurface waters at the inner-shelf station. This finding can only be explained if strong storms during these downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of autochthonous coccolithophore community structure. At both locations, the major coccolithophore assemblages were dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, Syracosphaera spp., Coronosphaera mediterranea, and Calcidiscus leptoporus. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccosphere abundance. These findings provide relevant information for the use of fossil coccolith assemblages in marine sediment records, in order to infer past environmental conditions, of

  4. Spatial and temporal variability in coccolithophore abundance and distribution in the NW Iberian coastal upwelling system

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    B. Ausín

    2018-01-01

    Full Text Available A systematic investigation of the spatial and temporal variability in coccolithophore abundance and distribution through the water column of the NW Iberian coastal upwelling system was performed. From July 2011 to June 2012, monthly sampling at various water depths was conducted at two parallel stations located at 42° N. Total coccosphere abundance was higher at the outer-shelf station, where warmer, nutrient-depleted waters favoured coccolithophore rather than phytoplanktonic diatom blooms, which are known to dominate the inner-shelf location. In seasonal terms, higher coccosphere and coccolith abundances were registered at both stations during upwelling seasons, coinciding with high irradiance levels. This was typically in conjunction with stratified, nutrient-poor conditions (i.e. relaxing upwelling conditions. However, it also occurred during some upwelling events of colder, nutrient-rich subsurface waters onto the continental shelf. Minimum abundances were generally found during downwelling periods, with unexpectedly high coccolith abundance registered in subsurface waters at the inner-shelf station. This finding can only be explained if strong storms during these downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of autochthonous coccolithophore community structure. At both locations, the major coccolithophore assemblages were dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, Syracosphaera spp., Coronosphaera mediterranea, and Calcidiscus leptoporus. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccosphere abundance. These findings provide relevant information for the use of fossil coccolith assemblages in marine sediment records, in order to infer past

  5. Outside the paradigm of upwelling rias in NW Iberian Peninsula: Biogeochemical and phytoplankton patterns of a non-upwelling ria

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    Ospina-Alvarez, Natalia; Varela, Manuel; Doval, María Dolores; Gómez-Gesteira, Moncho; Cervantes-Duarte, Rafael; Prego, Ricardo

    2014-02-01

    The Atlantic Galician rias show the effect of natural eutrophication during ENACW upwelling episodes when large amounts of nutrients are injected. However, the Cantabrian Galician rias do not appear to be disturbed by upwelling events and it can be hypothesized that eutrophy is not inherent to the Galician rias. This question was tackled regarding the biogeochemical and phytoplankton characteristic in the Ria of Barqueiro, located on the western boundary of the Cantabrian Sea, from January 2008 to January 2009. Thermohaline, PAR and fluorescence profiles, dissolved oxygen, nutrient salts, DOC, DON and chlorophyll concentrations, phytoplankton abundances and primary production were monthly determined in a monitoring station (43°45.509‧N-07°39.493‧W); moreover, the daily upwelling index information and fluvial contributions from Sor River were considered. Throughout the year only four annual oceanographic periods were observed: spring, summer stratification, autumn and winter, unlike the Atlantic rias, where a long upwelling period occurs with usually outstanding upwelling processes. Nutrient concentrations (a maximum of 6.2 μM of nitrate, 0.5 μM of nitrite, 2.8 μM of ammonium, 0.4 μM of phosphate and 5.7 μM of silicate), organic matter (98 μM of DOC, 14 μM of DON, 16.4 μM of POC and 2.0 μM of PON), Chl-a (1.1 μg L-1), primary production (280 gC m-2 yr-1) and phytoplankton abundance were clearly lower (about half) when compared to those reported for the other rias during upwelling. Diatoms dominated the phytoplankton assemblages especially during spring and autumn blooms. In summer, although the wind conditions were favorable, upwelling was not observed in the Ria and a mixing of diatoms and dinoflagellates co-dominated the phytoplankton community with a lower contribution of diatoms in comparison to the Atlantic rias. The paradigm of natural eutrophication reported for the Galician rias was not observed in the Ria of Barqueiro, which may be

  6. In-phase inter-hemispheric changes in two upwelling regions: The Southeast Brazilian and NW Iberian margins

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    Renata Hanae Nagai

    2016-02-01

    Full Text Available Two high-resolution multi-proxy records from cores collected in the upwelling regions off Cabo Frio (Brazil, core 7620 and Galicia (NW Iberian Peninsula, core KSGX40 were used to evaluate environmental changes during the Holocene. Core 7620 is a muddy sequence that exhibits gradual coarsening upward and covers a time period of approximately 9400 yr cal BP. Core KSGX40 records the last 4800 yr cal BP and consists of a sedimentary sequence exhibiting gradual fining upward in grain size. Results from core 7620 indicate that important changes occurred at 7000, 5800 and 3000 yr cal BP. Micropaleontological proxies indicate an increase in organic carbon supply towards the bottom, due to higher oceanic productivity, in the last 2500 yr cal BP. This increment in oceanic productivity is likely related to stronger upwelling events in the Cabo Frio region in that period. Core KSGX40 also indicates an increment in upwelling events in the Galicia region in the last 2500 yr cal BP. In both systems, the upwelling is linked to the intensification of NE winds and the prevalence of relatively drier climatic conditions. The Holocene upwelling changes in the Cabo Frio region were previously attributed to deviations in the position of the Inter-Tropical Convergence Zone (ITCZ, whereas in the Galician area this phenomenon was attributed to alterations in the North Atlantic Oscillation (NAO. The multi-millennial variability recorded in both cores suggests the occurrence of Holocene in-phase climatic changes both in Southern Hemisphere at the latitudes of the SW coast of Brazil (Cabo Frio region and in the Northern Hemisphere, at the latitude of Galicia (NW Iberian Margin. These coupled climatic alterations were probably related to changes in the oceanic-atmospheric climatic systems, coupled with and amplified by solar forcing effects.

  7. The effects of a winter upwelling on biogeochemical and planktonic components in an area close to the Galician Upwelling Core: The Sound of Corcubión (NW Spain)

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    Varela, Manuel; Álvarez-Ossorio, Ma Teresa; Bode, Antonio; Prego, Ricardo; Bernárdez, Patricia; Garcia-Soto, Carlos

    2010-10-01

    To study the biogeochemical response and the coupling plankton-benthos to an unusual winter upwelling event a cruise was carried out in February 2005 in the Sound of Corcubión, near Cape Finisterre (NW Iberian Peninsula), the Galician upwelling core. This area represents the northern boundary of the Eastern North Atlantic Upwelling System (ENAUS). The spatial distribution of plankton assemblages (phytoplankton and zooplankton), chlorophyll, physical and chemical parameters as well as diatom distribution in surface sediments, were studied in a total of 17 stations in the Sound. The upwelling processes caused an important accumulation of water in the inner Sound and near the Cape. This accumulation zone must be persistent through the upwelling events in the area, including those of summer, as indicated by the diatoms' distribution in the sediment. Unlike the summer upwelling events, the main effect of winter upwelling in the area is the increase in solar radiation due to the persistent clear skies. In this season nutrient supply is not critical due to water column mixing. The meteorological conditions were equivalent to those of early spring. As a result, both phyto- and zooplankton species assemblages were typical of spring blooms in Galician coasts. The bloom lasted for up to 6 days, as estimated from the availability and uptake of nitrogen forms. Winter blooms represented ca. 20% of total annual phytoplankton biomass, and 30% of the average biomass during summer upwelling, in the period 1997-2007, as estimated from the analysis of both, in situ and satellite derived chlorophyll.

  8. Comparative study of potential transfer of natural and anthropogenic cadmium to plankton communities in the North-West African upwelling

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    Auger, P.A., E-mail: pierreamael.auger@gmail.com [Laboratoire de Physique des Océans (LPO), UMR-CNRS 6523/IFREMER/IRD/UBO, BP70, 29280 Plouzané (France); Machu, E.; Gorgues, T.; Grima, N. [Laboratoire de Physique des Océans (LPO), UMR-CNRS 6523/IFREMER/IRD/UBO, BP70, 29280 Plouzané (France); Waeles, M. [Université de Bretagne Occidentale (UBO), Laboratoire de l' Environnement Marin (LEMAR), UMR-CNRS 6539/IRD/UBO, place N. Copernic, 29280 Plouzané (France)

    2015-02-01

    A Lagrangian approach based on a physical–biogeochemical modeling was used to compare the potential transfer of cadmium (Cd) from natural and anthropogenic sources to plankton communities (Cd-uptake) in the North-West African upwelling. In this region, coastal upwelling was estimated to be the main natural source of Cd while the most significant anthropogenic source for marine ecosystem is provided by phosphate industry. In our model experiment, Cd-uptake (natural or anthropogenic) in the North-West African upwelling is the result of an interplay between the Cd dispersion (by advection processes) and the simulated biological productivity. In the Moroccan waters, advection processes limit the residence time of water masses resulting in a low natural Cd-uptake by plankton communities while anthropogenic Cd-uptake is high. As expected, the situation is reversed in the Senegalo-Mauritanian upwelling where natural Cd-uptake is higher than anthropogenic Cd-uptake. Based upon an estimate of Cd sources, our modeling study shows, unexpectedly, that the anthropogenic signal of potential Cd-bioaccumulation in the Moroccan upwelling is of the same order of magnitude as the natural signal mainly present in the Senegalo-Mauritanian upwelling region. A comparison with observed Cd levels in mollusk and fishes, which shows overall agreement with our simulations, is confirming our estimates. - Highlights: • We model the physical–biogeochemical dynamics in the North-West African upwelling. • We model the transport of cadmium from natural and anthropogenic sources. • We derive proxies of potential cadmium absorption and bioaccumulation in the plankton food chain. • The anthropogenic signal off Morocco at least equals the natural upwelling signal off Mauritania. • We compare our results with observed cadmium levels in mollusks and fishes.

  9. Comparative study of potential transfer of natural and anthropogenic cadmium to plankton communities in the North-West African upwelling

    International Nuclear Information System (INIS)

    Auger, P.A.; Machu, E.; Gorgues, T.; Grima, N.; Waeles, M.

    2015-01-01

    A Lagrangian approach based on a physical–biogeochemical modeling was used to compare the potential transfer of cadmium (Cd) from natural and anthropogenic sources to plankton communities (Cd-uptake) in the North-West African upwelling. In this region, coastal upwelling was estimated to be the main natural source of Cd while the most significant anthropogenic source for marine ecosystem is provided by phosphate industry. In our model experiment, Cd-uptake (natural or anthropogenic) in the North-West African upwelling is the result of an interplay between the Cd dispersion (by advection processes) and the simulated biological productivity. In the Moroccan waters, advection processes limit the residence time of water masses resulting in a low natural Cd-uptake by plankton communities while anthropogenic Cd-uptake is high. As expected, the situation is reversed in the Senegalo-Mauritanian upwelling where natural Cd-uptake is higher than anthropogenic Cd-uptake. Based upon an estimate of Cd sources, our modeling study shows, unexpectedly, that the anthropogenic signal of potential Cd-bioaccumulation in the Moroccan upwelling is of the same order of magnitude as the natural signal mainly present in the Senegalo-Mauritanian upwelling region. A comparison with observed Cd levels in mollusk and fishes, which shows overall agreement with our simulations, is confirming our estimates. - Highlights: • We model the physical–biogeochemical dynamics in the North-West African upwelling. • We model the transport of cadmium from natural and anthropogenic sources. • We derive proxies of potential cadmium absorption and bioaccumulation in the plankton food chain. • The anthropogenic signal off Morocco at least equals the natural upwelling signal off Mauritania. • We compare our results with observed cadmium levels in mollusks and fishes

  10. Short-term changes in the northwest African Upwelling System induced by Saharan dust deposition events

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    Ramos, A G; Coca, J; Redondo, A [SeaSnet Canarias. Dpto. de Biologia (University of Las Palmas de Gran Canaria), Canary Islands (Spain); Cuevas, E; Alonso-Perez, S; Bustos, J J [Izana Atmospheric Research Center, Agencia Estatal de Meteorologia, Tenerife (Spain); Perez, C; Baldasano, J M [Earth Sciences Department. Barcelona Supercomputing Center, Barcelona (Spain); Nickovic, S [Atmospheric Research and Environment Branch, World Meteorological Organization, Geneva (Switzerland)], E-mail: aramos@pesca.gi.ulpgc.es

    2009-03-01

    During the last 7-year period (2000-2006) atmosphere circulation changes show strong influences on the dust storm deposition dynamics and, as a result, on the primary production dynamics of the northwest African Upwelling System. From 2000 to 2006, the annual mean sea level pressure became higher ranging from 1014 to 1015 mb. Mean annual zonal wind intensity became higher (from 1.1 to 1.8 m s{sup -1}), while the mean annual meridional was reduced from 6.2 to 5.3 m s{sup -1} at the north of the Canary Islands. Mean annual satellite-derived AVHRR/NOAA SST recorded in the northwest African Upwelling became warmer in both locations, from 18.3 deg. C to 18.8 deg. C in Cape Ghir and from 19.5 deg. C to 20.3 deg. C north Canary Islands waters. CHL records from the SeaWiFS/OV-2 showed a different pattern trend. Mean annual CHL levels increased at Cape Ghir from 0.65 mg m-3 to 0.9 mg m-3 and significantly reduced from 0.59 mg m{sup -3} to 0.31 mg m{sup -3} at the north of the Canary Islands. Changes observed in the role of CHL during the last 7-years period could be associated to intensive dust deposition and exceptional weather warming observed in this area since 2000. However, this study focused on a 7-year period and conclusions on possible links between dust deposition and marine biochemistry activity cannot be generalized.

  11. Bloom dynamics and life cycle strategies of two toxic dinoflagellates in a coastal upwelling system (NW Iberian Peninsula)

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    Bravo, Isabel; Fraga, Santiago; Isabel Figueroa, Rosa; Pazos, Yolanda; Massanet, Ana; Ramilo, Isabel

    2010-02-01

    A study of Gymnodinium catenatum and Alexandrium minutum blooms on the Galician coast was conducted from 2005 to 2007 in order to increase knowledge of the mechanisms governing recurrent blooms of these species. Considerable differences in their bloom dynamics were observed. G. catenatum blooms occurred in autumn and winter, following the pattern previously reported in the literature: they began off-shore and were advected to the Galician rias when a relaxation of the coastal upwelling occurred. On the other hand, A. minutum blooms developed inside embayments in spring and summer during the upwelling season and were associated with water stability and stratification. Both the vegetative population and the cyst distribution of A. minutum were related to less saline water from freshwater river outputs, which support a saline-gradient relationship postulated herein for this species. Dinoflagellates may produce both long-term double-walled cysts (resting) and short-term pellicle cysts. Resting cyst deposition and distribution in sediments showed that seeding occurred during the blooms of both species. However, the relationship between the cyst distribution in the sediments in Baiona Bay and the intensity and occurrence of G. catenatum blooms, suggests that the latter are not directly related to resting cyst germination. Moreover, the results presented in the present study point to other difference between the two species, such as the detection of pellicle cysts only for A. minutum. Finally, we discuss how the life cycle strategies of these two species may help to explain the different mechanisms of bloom formation reported herein.

  12. Oceanographical patterns during a summer upwelling-downwelling event in the Northern Galician Rias: Comparison with the whole Ria system (NW of Iberian Peninsula)

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    Ospina-Alvarez, N.; Prego, R.; Álvarez, I.; deCastro, M.; Álvarez-Ossorio, M. T.; Pazos, Y.; Campos, M. J.; Bernárdez, P.; Garcia-Soto, C.; Gómez-Gesteira, M.; Varela, M.

    2010-07-01

    Summer upwelling and downwelling processes were characterized in the Northern Galician Rias during July and August 2008 by means of sampling carried out onboard R/V Mytilus (CSIC) and R/V Lura (IEO). Thermohaline variables, dissolved oxygen, nutrients, chlorophyll, phytoplankton, ciliates and zooplankton abundances were measured at sections located in the Rias of Viveiro, Barqueiro and Ortigueira and their adjacent shelves. Ekman transport was calculated from QuikSCAT satellite, upwelling intensity estimated with upwelling index from the average daily geostrophic winds, and SST maps obtained from NASA GHRSST satellite. Ekman transport and SST behaviour showed two different patterns: (i) offshore and upwelling favourable conditions on 13-22nd of July; (ii) onshore and downwelling favourable conditions from 23rd July to 19th August. During upwelling, TS diagram showed an intrusion of Eastern North Atlantic Central Water affecting the continental shelf but not the rias. Nutrient salt concentrations increased with depth, reaching their maximum values near the mouth of Ortigueira Ria. During downwelling, coastal water increased its temperature (18.5-19.8 °C) and was retained inside rias; nutrients were nearly depleted, except for the innermost ria (estuarine zone) due to fluvial nutrient inputs. In this inner area, the maximum of chlorophyll- a (Barqueiro Ria) was observed. Low phytoplankton abundances were measured in both cases, even though a short increase in the plankton biomass was observed inside rias during upwelling, while under downwelling a small red tide of Lingulodinium polyedrum was detected. During the upwelling period Northern Rias tend to be mesotrophic systems as revealed by nutrient concentrations, chlorophyll levels and plankton abundances. On the contrary, in similar situations, the Western Rias behaves as eutrophics. In the Northern Galician shelf, the average of upwelling (downwelling) was 1.9±0.8 (2.1±1.0) events yr -1 from May to September

  13. Alkaline phosphatase activity and its relationship to inorganic phosphorus in the transition zone of the North-western African upwelling system

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    Sebastián, Marta; Arístegui, Javier; Montero, María F.; Escanez, Jose; Xavier Niell, F.

    2004-08-01

    The enzymatic activity of alkaline phosphatase (APA) was studied in the transition zone between the African upwelling system and the open ocean waters of the Canary Islands region. This region is recurrently dominated by the presence of upwelling filaments that may transport nutrient-enriched waters out into the open ocean before nutrients become exhausted by plankton. Turnover rates by APA were generally low in the whole region, but detectable in all the measurements carried out. On average, turnover rates were higher in the upwelling stations, and APA in those waters seemed to be mainly generated by heterotrophic bacteria to supply easily assimilable organic C. APA outside the upwelling area showed an inverse hyperbolic relationship with increasing phosphate, suggesting the presence of both constitutive and Pi-inducible APA. In these offshore waters, a threshold of 0.1 μM of phosphate could be defined for the regulatory function of Pi on APA. Thus, APA in nutrient-poor waters seemed to be induced to compensate for Pi-deficiency. Turnover rates in the filaments showed basal (probably constitutive) levels, whereas they increased in the surrounding waters, where phosphate concentration presumably did not satisfy plankton P-demands. The fertilising effect of the filaments and associated cyclonic eddies extended to at least 175 km offshore, where basal alkaline phosphatase activities were still found. The magnitude of this effect depends probably on the intensity of upwelling events and the degree of recirculation of filament water back to the coastal jet.

  14. Benthic phosphorus and iron budgets for three NW African slope sediments: a balance approach

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    K. Küster-Heins

    2010-02-01

    Full Text Available Despite intensive research on the different domains of the marine phosphorus (P cycle during the last decades, frequently discussed open questions still exist especially on controlling factors for the benthic behaviour of P and its general distribution in sediment-pore water systems. Steady state or the internal balance of all relevant physical and (biogeochemical processes are amongst the key issues. In this study we present and discuss an extended data set from surface sediments recovered from three locations on the NW African continental slope. Pore water data and results from sequential sediment extractions give clear evidence to the well-known close relationship between the benthic cycles of P and iron. Accordingly, most of the dissolved phosphate must have been released by microbially catalyzed reductive dissolution of iron (oxhydroxides. However, rates of release and association of P and iron, respectively, are not directly represented in profiles of element specific sediment compositions. Results from steady-state based transport-reaction modelling suggest that particle mixing due to active bioturbation, or rather a physical net downward transport of P associated to iron (oxyhydroxides, is an essential process for the balance of the inspected benthic cycles. This study emphasizes the importance of balancing analytical data for a comprehensive understanding of all processes involved in biogeochemical cycles.

  15. Temporal variation and trends of inorganic nutrients in the coastal upwelling of the NW Spain (Atlantic Galician rías)

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    Doval, M. D.; López, A.; Madriñán, M.

    2016-02-01

    The temporal variability of inorganic nutrients (nitrate, nitrite, ammonium, phosphate and silicate) in five coastal upwelling Galician rías (Ría de Vigo, Ría de Pontevedra, Ría de Arousa, Ría de Muros and Ría de Ares-Betanzos) was assessed by considering biweekly values at 10 oceanographic stations for the decade 2002-2011. The long trends (1993-2011) of biweekly and annual average series for one station (mouth of Ría de Arousa, A0) were compared with decadal trends. A marked seasonal variability in all surface inorganic nutrients was observed. The average of the ten annual cycles (2002-2011) of each variable was calculated in order to obtain the average seasonal cycles. Maximum surface values occurred from the end of October to the end of February (8-24 μmol L- 1 dissolved inorganic nitrogen, 5-22 μmol L- 1 silicate and 0.5-1.8 μmol L- 1 phosphate). Minimum surface values (0.9-3.0 μmol L- 1 dissolved inorganic nitrogen, 0.6-2.5 μmol L- 1 silicate and 0.15-0.6 μmol L- 1 phosphate) detected from the beginning of May to the end of September. The highest nutrient concentrations (> 35%) recorded in the inner stations (V3, P3, A3, M2 and L3), as compared to the outer stations (V5, P4, A0, M5 and L1), indicated a more estuarine behaviour of these areas. Trends of the deseasonalised nutrient data were highly dependent on factors as length of the series, the initial year and the time integration period considered. The results found for these trends should be taken with caution due to the change in the sign of the slopes and the moderate accuracy of the models. Considering the variables whose trends did not change sign, ammonium and silicate showed a slightly positive trend for the biweekly-averaged series in A0 station during the periods 2002-2011 and 1993-2011.

  16. Dynamics of plankton populations in upwelling areas

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    Szekielda, K. H. (Principal Investigator)

    1975-01-01

    The author has identified the following significant results. Spectral properties of the upwelled waters off the NW coast of Africa were studied with observations derived from aircraft and Skylab. Results indicate that the two-channel, ratio approach is ineffective in determining surface chlorophyll concentrations. Ocean color boundaries and temperature gradients were found to be directly correlated with each other and also with fishing effort in the upwelling region. Photographic and scanner data derived from Skylab were effective in locating ocean boundaries and mapping temperature distributions.

  17. Relationships between academic performance, SES school type and perceptual-motor skills in first grade South African learners: NW-CHILD study.

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    Pienaar, A E; Barhorst, R; Twisk, J W R

    2014-05-01

    Perceptual-motor skills contribute to a variety of basic learning skills associated with normal academic success. This study aimed to determine the relationship between academic performance and perceptual-motor skills in first grade South African learners and whether low SES (socio-economic status) school type plays a role in such a relationship. This cross-sectional study of the baseline measurements of the NW-CHILD longitudinal study included a stratified random sample of first grade learners (n = 812; 418 boys and 394 boys), with a mean age of 6.78 years ± 0.49 living in the North West Province (NW) of South Africa. The Beery-Buktenica Developmental Test of Visual-Motor Integration-4 (VMI) was used to assess visual-motor integration, visual perception and hand control while the Bruininks Oseretsky Test of Motor Proficiency, short form (BOT2-SF) assessed overall motor proficiency. Academic performance in math, reading and writing was assessed with the Mastery of Basic Learning Areas Questionnaire. Linear mixed models analysis was performed with spss to determine possible differences between the different VMI and BOT2-SF standard scores in different math, reading and writing mastery categories ranging from no mastery to outstanding mastery. A multinomial multilevel logistic regression analysis was performed to assess the relationship between a clustered score of academic performance and the different determinants. A strong relationship was established between academic performance and VMI, visual perception, hand control and motor proficiency with a significant relationship between a clustered academic performance score, visual-motor integration and visual perception. A negative association was established between low SES school types on academic performance, with a common perceptual motor foundation shared by all basic learning areas. Visual-motor integration, visual perception, hand control and motor proficiency are closely related to basic academic skills

  18. Dynamics of plankton populations in upwelling areas. [by remote sensors

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    Szekielda, K.

    1974-01-01

    Recent investigations of the upwelling area along the NW Coast of Africa which include studies with satellites are discussed. The detection of patchiness in temperature and plankton distribution in the upwelling area is of special interest because they can be investigated from space synoptically with repeated coverage. The recent satellite missions provide recordings in the infrared region of the electromagnetic spectrum (EMR) as well as in the visible part. The information from those two parts of the EMR is useful for establishing the sea surface temperature and plankton distribution in upwelling areas. The temperature distribution as observed with infrared sensors and the patchiness in plankton patterns are discussed as observed with the most recent satellites, namely the Earth Resources Technology Satellite (ERTS) and NOAA-2.

  19. Crustal structure variations along the NW-African continental margin: A comparison of new and existing models from wide-angle and reflection seismic data

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    Klingelhoefer, Frauke; Biari, Youssef; Sahabi, Mohamed; Aslanian, Daniel; Schnabel, Michael; Matias, Luis; Benabdellouahed, Massinissa; Funck, Thomas; Gutscher, Marc-André; Reichert, Christian; Austin, James A.

    2016-04-01

    Deep seismic data represent a key to understand the geometry and mechanism of continental rifting. The passive continental margin of NW-Africa is one of the oldest on earth, formed during the Upper Triassic-Lower Liassic rifting of the central Atlantic Ocean over 200 Ma. We present new and existing wide-angle and reflection seismic data from four study regions along the margin located in the south offshore DAKHLA, on the central continental margin offshore Safi, in the northern Moroccan salt basin, and in the Gulf of Cadiz. The thickness of unthinned continental crust decreases from 36 km in the North to about 27 km in the South. Crustal thinning takes place over a region of 150 km in the north and only 70 km in the south. The North Moroccan Basin is underlain by highly thinned continental crust of only 6-8 km thickness. The ocean-continent transition zone shows a variable width between 40 and 70 km and is characterized by seismic velocities in between those of typical oceanic and thinned continental crust. The neighbouring oceanic crust is characterized by a thickness of 7-8 km along the complete margin. Relatively high velocities of up to 7.5 km/s have been imaged between magnetic anomalies S1 and M25, and are probably related to changes in the spreading velocities at the time of the Kimmeridgian/Tithonian plate reorganization. Volcanic activity seems to be mostly confined to the region next to the Canary Islands, and is thus not related to the initial opening of the ocean, which was associated to only weak volcanism. Comparison with the conjugate margin off Nova Scotia shows comparable continental crustal structures, but 2-3 km thinner oceanic crust on the American side than on the African margin.

  20. Rapid 20th-century increase in coastal upwelling off northwest Africa.

    Science.gov (United States)

    McGregor, H V; Dima, M; Fischer, H W; Mulitza, S

    2007-02-02

    Near-shore waters along the northwest African margin are characterized by coastal upwelling and represent one of the world's major upwelling regions. Sea surface temperature (SST) records from Moroccan sediment cores, extending back 2500 years, reveal anomalous and unprecedented cooling during the 20th century, which is consistent with increased upwelling. Upwelling-driven SSTs also vary out of phase with millennial-scale changes in Northern Hemisphere temperature anomalies (NHTAs) and show relatively warm conditions during the Little Ice Age and relatively cool conditions during the Medieval Warm Period. Together, these results suggest that coastal upwelling varies with NHTAs and that upwelling off northwest Africa may continue to intensify as global warming and atmospheric CO2 levels increase.

  1. Climate influence on the North West African fisheries: a large-scale perspective

    Science.gov (United States)

    Lopez-Parages, Jorge; Rodriguez-Fonseca, Belén; Brochier, Timothee; Auger, Pierre-Amaël; Gaetan, Carlo; Rubino, Angelo; Keenlyside, Noel; Zanchettin, Davide; Woldeyes Arisido, Maeregu

    2017-04-01

    There are still many questions about the environmental forcings on marine biological ecosystems that need to be addressed. Of special relevance are those associated with the so-called Eastern Boundary Upwelling Systems (EBUS) due to their great climatic and socio-economic importance, being the latter specially crucial for some regions along the globe such as the North West African region (hereinafter NW Africa). In this study, some possible teleconnections involving large-scale climatic phenomena and the small pelagic fishes dynamics in the NW Africa, have been addressed. These possible teleconnections would be interesting on its own, but those associated with the Sea Surface Temperature (SST) processes are of special importance, since they could noticeably contribute to the development of a seasonal prediction system of fisheries. To this aim, we have used data provided by the couple model compounded by the Regional Oceanic Modeling System ROMS configured for the NW African upwelling system and by the biogeochemical model PISCES, which simulates plankton productivity and carbon biomass based upon the main nutrients. This coupled model has been run over the period 1980-2009 using interannual atmospheric forcings and consistent oceanic boundary conditions (from NCEP Climate Forecast System Reanalysis). Finally, an evolutionary individual-based Lagrangian model has been used to simulate the spatio-temporal behavior of the small pelagic fishes, at different stages, according to the environmental constraints obtained from ROMS. The results obtained, though preliminary, point out that the well known El Niño-Southern Oscillation variability mode (ENSO) could act as a possible large-scale climatic forcing of the NW African fishes, which could open a window of opportunity for the development of an effective seasonal prediction system in the aforementioned region.

  2. Under pressure: Climate change, upwelling and eastern boundary upwelling ecosystems

    Directory of Open Access Journals (Sweden)

    Marisol eGarcía-Reyes

    2015-12-01

    Full Text Available The IPCC AR5 provided an overview of the likely effects of climate change on Eastern Boundary Upwelling Systems (EBUS, stimulating increased interest in research examining the issue. We use these recent studies to develop a new synthesis describing climate change impacts on EBUS. We find that model and observational data suggest coastal upwelling-favorable winds in poleward portions of EBUS have intensified and will continue to do so in the future. Although evidence is weak in data that are presently available, future projections show that this pattern might be driven by changes in the positioning of the oceanic high-pressure systems rather than by deepening of the continental low-pressure systems, as previously proposed. There is low confidence regarding the future effects of climate change on coastal temperatures and biogeochemistry due to uncertainty in the countervailing responses to increasing upwelling and coastal warming, the latter of which could increase thermal stratification and render upwelling less effective in lifting nutrient-rich deep waters into the photic zone. Although predictions of ecosystem responses are uncertain, EBUS experience considerable natural variability and may be inherently resilient. However, multi-trophic level, end-to-end (i.e., winds to whales studies are needed to resolve the resilience of EBUS to climate change, especially their response to long-term trends or extremes that exceed pre-industrial ranges.

  3. Upwelling and sinking along Visakhapatnam coast

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.V.N.; Rao, D.P.; Rao, B.P.; RamaRaju, V.S.

    typical of a coastal upwelling driven by local wind stress. Upwelling is predominant off Visakhapatnam during premonsoon and monsoon periods. Waters from the deeper depths of the shelf appear to reach the surface causing considerable fall of temperature...

  4. Emergent anthropogenic trends in California Current upwelling

    Science.gov (United States)

    Brady, Riley X.; Alexander, Michael A.; Lovenduski, Nicole S.; Rykaczewski, Ryan R.

    2017-05-01

    Upwelling in the California Current System (CCS) sustains a productive ecosystem and is mediated by alongshore, equatorward wind stress. A decades-old hypothesis proposes that global warming will accelerate these upwelling favorable winds. Recent analyses provide empirical support for upwelling intensification in the poleward portion of the CCS. However, these studies rely on proxies for upwelling and are limited in their ability to distinguish anthropogenic forcing from internal climate variability. Here we estimate simulated changes in CCS upwelling from 1920 to 2100 using monthly output from a single climate model ensemble, where divergences among simulations can be attributed entirely to internal climate variability. Our projections suggest that CCS upwelling will become more intense in the spring and less intense in the summer as a result of anthropogenic climate change. Anthropogenic changes in upwelling will emerge primarily in the second half of the century.

  5. On the upwelling dynamics off northwest Africa in 2009-2012

    Science.gov (United States)

    Menna, Milena; Poulain, Pierre-Marie; Faye, Saliou; Diaw, Basirou; Centurioni, Luca; Lazar, Alban; Gaye, Amadou; Sow, Bamol Ali; Dragone, Dominique

    2014-05-01

    Drifter data, satellite maps and time series of SST, upwelling index and ocean surface wind products are used to characterise the North Western Africa upwelling system in the period 2009-2012, with particular focus to the region between Cap Blanc (Mauritania) and Cap Vert (Senegal). This region corresponds to the southern part of the seasonal translation of the Trade winds along the western African coast and the relative upwelling has a marked seasonal periodicity. The upwelling season generally starts in late November and persists until early July north of 20°N, whereas it starts in late December until May in the south; in June the upwelling events south of Cap Blanc disappear and gradually the residual cold water mixes with the warm surface tropical Atlantic water. The most intense upwelling episodes are recorded between February and May and the upwelling index reaches its maximum in April-May (values larger than 1000 m3/s). These episodes usually coincide with maximum intensities of upwelling favourable winds (Trade winds) and are characterised by a mean duration of 5-10 days, SST values lower than 20.2°C and upwelling index larger than 700 m3/s. Cold and nutrient-rich coastal near-surface waters are upwelled and transported offshore (westward) by means of energetic filaments rooted at specific locations along the coasts of Mauritania and Senegal. Four recurrent upwelling filaments (SST lower than 20°C), with an offshore extension between 200 km and 400 km, are observed and characterised. These filaments persist for a few weeks, and they subsequently mix with the surrounding waters. The filament formation is generally associated with the topographic features (capes) of the region. Wind vorticity fields show positive values close to the coast between Cape Vert and Cape Blanc during the upwelling seasons; larger values correspond with the location of the main cold water filaments. Cold water upwelled in the Cap Vert region are transported both westward, toward

  6. Relationships between academic performance, SES school type and perceptual-motor skills in first grade South African learners: NW-CHILD study

    NARCIS (Netherlands)

    Pienaar, A.E.; Barhorst, R.; Twisk, J.W.R.

    2014-01-01

    Background: Perceptual-motor skills contribute to a variety of basic learning skills associated with normal academic success. This study aimed to determine the relationship between academic performance and perceptual-motor skills in first grade South African learners and whether low SES

  7. Warm water upwelling in the Cenozoic Era

    Science.gov (United States)

    Zhang, Y.

    2017-12-01

    Modern observations show that the occurrence of wind-driven upwelling is often tied to cold sea surface temperatures (SSTs). However, SST reconstructions indicate that globally, the upwelling regions were much warmer in the Miocene and Pliocene. This questions the overall strength of deep-water upwelling in the geological past, with important implications for the associated atmospheric, climatic and biogeochemical processes, and the fate of upwelling regions in a high-CO2 world. We recently showed that the eastern equatorial Pacific (EEP) was characterized by strong air-sea disequilibrium of CO2 during the late Miocene - Pliocene. Combined with export productivity proxies, we interpreted these as signs of vigorous upwelling. The upwelled waters were nutrient- and CO2-rich, but warm. The cause of the "excess" warming in the upwelling regions is linked to the source waters which originated from the higher latitudes. In other words, the reduced east (upwelling) to west (non-upwelling) temperature gradients along the equator in major ocean basins are rooted in the reduced meridional temperature gradients. To further test this hypothesis, we examine the history of the EEP and temperature gradients during the even-warmer Eocene - middle Miocene.

  8. Geochemical character and petrogenesis of Pan-African Amspoort suite of the Boundary Igneous Complex in the Kaoko Belt (NW Namibia)

    Czech Academy of Sciences Publication Activity Database

    Janoušek, V.; Konopásek, J.; Ulrich, Stanislav; Erban, V.; Tajčmanová, L.; Jeřábek, P.

    2010-01-01

    Roč. 18, č. 4 (2010), s. 688-707 ISSN 1342-937X Grant - others:GA ČR(CZ) GA205/07/1409 Institutional research plan: CEZ:AV0Z30120515 Keywords : whole-rock geochemistry * Pan-African * Damara Orogeny * Boundary Igneous Complex * Kaoko Belt * Namibia Subject RIV: DD - Geochemistry Impact factor: 5.503, year: 2010

  9. The physical structure of an upwelling filament off the North-west ...

    African Journals Online (AJOL)

    ... in dispersal of material originating in the region of active coastal upwelling. The location of the filament studied appears repeatable from year to year, suggestive of a strong relation with the topographically trapped eddy, which was situated downstream of a lateral ridge between the. Canary Islands and the African coast.

  10. Upwelling along the east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, C.S.; Varadachari, V.V.R.

    but with the following differences: (1) Off Madras and Karaikal, weak upwelling is indicated. Water from shallow depths reach the surface nearshore and there is no marked lowering of the surface temperature near the coast. (2) Upwelling is prominent off Waltair during...

  11. Crustal structure variations along the NW-African continental margin: a comparison of new and existing models from wide angle and reflection seismic data

    Science.gov (United States)

    Biari, Y.; Klingelhoefer, F.; Sahabi, M.; Aslanian, D.; Philippe, S.; Louden, K. E.; Berglar, K.; Moulin, M.; Mehdi, K.; Graindorge, D.; Evain, M.; Benabellouahed, M.; Reichert, C. J.

    2014-12-01

    Deep seismic data represent a key to understand the geometry and mechanism of continental rifting. The passive continental margin of NW-Africa is one of the oldest on earth, formed during the Upper Triassic-Lower Liassic rifting of the central Atlantic Ocean over 200 Ma. We present new and existing wide-angle and reflection seismic data from three study regions along the margin located in the North Moroccan salt basin, on the central continental margin offshore Safi and in the south, offshore Dakhla. In each of the study areas several combined wide-angle and reflection seismic profiles perpendicular and parallel to the margin have been acquired and forward modelled using comparable methods. The thickness of unthinned continental crust decreases from 36 km in the North to about 27 km in the South. In the North Moroccan Basin continental crust thins from originally 36 km to about 8 km in a 150 km wide zone. The basin itself is underlain by highly thinned continental crust. Offshore safi thinning of the continental crust is confined to a 130 km wide zone with no neighboring sedimentary basin underlain by continental crust. In both areas the zone of crustal thinning is characterised by the presence of large blocks and abundant salt diapirs. In the south crustal thinning is more rapid in a zone of 90 km and asymmetric with the upper crust thinning more closely to the continent than the lower crust, probably due to depth-dependent stretching and the presence of the precambrian Reguibat Ridge on land. Oceanic crust is characterised by a thickness of 7-8 km along the complete margin. Relatively high velocities of up to 7.5 km/s have been imaged between magnetic anomalies S1 and M25, and are probably related to changes in the spreading velocities at the time of the Kimmeridgian/Tithonian plate reorganisation. Volcanic activity seems to be confined to the region next to the Canary Islands, and is thus not related to the initial opening of the oceanic, which was related to no

  12. Role of nutrient recycling in upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T E

    1979-01-01

    The regeneration of nitrogen is an important process that increases the efficiency of the upwelling ecosystem by enlarging their spatial scales. Ammonium regeneration was considered to contribute 42 to 72 percent of phytoplankton nitrogen requirements in the northwest Africa, Peru, and Baja California upwelling systems. Zooplankton are responsible for the largest portion of regenerated nitrogen; however, fish and benthic sediments may be nearly as large. Comparisons of the importance of ammonium regeneration in upwelling areas with coastal and open ocean regions indicate that the percentage contributions are similar. Future nutrient regeneration studies are needed to assess the recycling of benthic sediments, microzooplankton, gelatinous zooplankton, demersal fish, bacterioplankton, and mollusks.

  13. Dehumidification of Iberia by enhanced summer upwelling

    Science.gov (United States)

    Miranda, P. M.; Costa, V.; Nogueira, M.; Semedo, A.

    2015-12-01

    Dehumidification of Iberia by enhanced summer upwelling Miranda PMA, Costa V, Semedo AIDL, Faculdade de Ciências, University of LisbonA 24-year simulation of the recent Iberian climate, using the WRF model at 9km resolution forced by ERA-Interim reanalysis (1989-2012), is analysed for the decadal evolution of the upwelling forcing coastal wind and for column integrated Precipitable water vapour (PWV). Results indicate that, unlike what was found by Bakun et al. (2009) for the Peruvian region, a statistically significant trend in the upwelling favourable (northerly) wind has been accompanied by a corresponding decrease in PWV, not only inland but also over the coastal waters. Such increase is consistent with a reinforced northerly coastal jet in the maritime boundary layer contributing to atmospheric Ekman pumping of dry continental air into the coastal region. Diagnostics of the prevalence of the Iberian thermal low following Hoinka and Castro (2003) also show a positive trend in its frequency during an extended summer period (April to September). These results are consistent with recent studies indicating an upward trend in the frequency of upwelling in SW Iberia (Alves and Miranda 2013), and may be relevant for climate change applications as an increase in coastal upwelling (Miranda et al 2013) may lead to substantial regional impacts in the subtropics. Aknowledgements: Study supported by FCT Grant RECI/GEO-MET/0380/2012Alves JMR, Miranda PMA (2013) Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses, Tellus A 2013, http://dx.doi.org/10.3402/tellusa.v65i0.19245.Bakun et al (2010) Greenhouse gas, upwelling-favorable winds, and the future of coastal ocean upwelling ecosystems, Global Change Biology, doi: 10.1111/j.1365-2486.2009.02094.xHoinka KP, Castro M (2003) The Iberian Peninsula thermal low. QJRMS, 129, 1491- 1511, doi: 10.1256/qj.01.189.Miranda et al (2013) Climate change and upwelling: response of Iberian upwelling to atmospheric

  14. Effects of suspended mussel culture on benthic-pelagic coupling in a coastal upwrelling system (Ria de Vigo, NW Iberian Peninsula)

    NARCIS (Netherlands)

    Alonso-Perez, F.; Ysebaert, T.; Castro, C.G.

    2010-01-01

    The influence of suspended mussel culture on the benthic-pelagic coupling was evaluated in the Ria de Vigo, in the coastal upwelling system of the NW Iberian Peninsula, during the month of July 2004. Measurements of water column properties were carried out at three stations in the Ria de Vigo: under

  15. Coastal upwelling south of Madagascar: Temporal and spatial variability

    Science.gov (United States)

    Ramanantsoa, Juliano D.; Krug, M.; Penven, P.; Rouault, M.; Gula, J.

    2018-02-01

    Madagascar's southern coastal marine zone is a region of high biological productivity which supports a wide range of marine ecosystems, including fisheries. This high biological productivity is attributed to coastal upwelling. This paper provides new insights on the structure, variability and drivers of the coastal upwelling south of Madagascar. Satellite remote sensing is used to characterize the spatial extent and strength of the coastal upwelling. A front detection algorithm is applied to thirteen years of Multi-scale Ultra-high Resolution (MUR) Sea Surface Temperatures (SST) and an upwelling index is calculated. The influence of winds and ocean currents as drivers of the upwelling is investigated using satellite, in-situ observations, and a numerical model. Results reveal the presence of two well-defined upwelling cells. The first cell (Core 1) is located in the southeastern corner of Madagascar, and the second cell (Core 2) is west of the southern tip of Madagascar. These two cores are characterized by different seasonal variability, different intensities, different upwelled water mass origins, and distinct forcing mechanisms. Core 1 is associated with a dynamical upwelling forced by the detachment of the East Madagascar Current (EMC), which is reinforced by upwelling favourable winds. Core 2 appears to be primarily forced by upwelling favourable winds, but is also influenced by a poleward eastern boundary flow coming from the Mozambique Channel. The intrusion of Mozambique Channel warm waters could result in an asynchronicity in seasonality between upwelling surface signature and upwelling favourables winds.

  16. A comparison of Globigerinoides ruber calcification between upwelling and non-upwelling regions in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Godad, S.P.; Naidu, P.D.; Ramaswamy, V.

    Shell weights of planktonic foraminifera species Globigerinoides ruber in the size range of 300–355 mew m were measured from sediment traps in the western and eastern Arabian Sea which represent upwelling and non-upwelling conditions respectively...

  17. Zonation of bacterioplankton communities along aging upwelled water in the northern Benguela upwelling

    Directory of Open Access Journals (Sweden)

    Benjamin eBergen

    2015-06-01

    Full Text Available Upwelling areas are shaped by enhanced primary production in surface waters, accompanied by a well-investigated planktonic succession. Although bacteria play an important role in biogeochemical cycles of upwelling systems, little is known about bacterial community composition and its development during upwelling events. The aim of this study was to investigate the succession of bacterial assemblages in aging upwelled water of the Benguela upwelling from coastal to offshore sites. Water from the upper mixed layer at 12 stations was sampled along two transects from the origin of the upwelling to a distance of 220 km. 16S rRNA gene amplicon sequencing was then used in a bacterial diversity analysis and major bacterial taxa were quantified by catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH. Additionally, bacterial cell numbers and bacterial production were assessed . Community statistical analysis revealed a reproducible zonation along the two transects, with four clusters of significantly different microbial assemblages. Clustering was mainly driven by phytoplankton composition and abundance. Similar to the temporal succession that occurs during phytoplankton blooms in temperate coastal waters, operational taxonomic units (OTUs affiliated with Bacteroidetes and Gammaproteobacteria were dominant during algal blooming whereas Pelagibacterales were highly abundant in regions with low algal abundance. The most dominant heterotrophic OTU (9% of all reads was affiliated with Pelagibacterales and showed a strong negative correlation with phytoplankton. By contrast, the second most abundant heterotrophic OTU (6% of all reads was affiliated with the phylum Verrucomicrobia and correlated positively with phytoplankton. Together with the close relation of bacterial production and phytoplankton abundance, our results showed that bacterial community dynamics is strongly driven by the development and composition of the phytoplankton

  18. Understanding the nature of mantle upwelling beneath East-Africa

    Science.gov (United States)

    Civiero, Chiara; Hammond, James; Goes, Saskia; Ahmed, Abdulhakim; Ayele, Atalay; Doubre, Cecile; Goitom, Berhe; Keir, Derek; Kendall, Mike; Leroy, Sylvie; Ogubazghi, Ghebrebrhan; Rumpker, Georg; Stuart, Graham

    2014-05-01

    The concept of hot upwelling material - otherwise known as mantle plumes - has long been accepted as a possible mechanism to explain hotspots occurring at Earth's surface and it is recognized as a way of removing heat from the deep Earth. Nevertheless, this theory remains controversial since no one has definitively imaged a plume and over the last decades several other potential mechanisms that do not require a deep mantle source have been invoked to explain this phenomenon, for example small-scale convection at rifted margins, meteorite impacts or lithospheric delamination. One of the best locations to study the potential connection between hotspot volcanism at the surface and deep mantle plumes on land is the East African Rift (EAR). We image seismic velocity structure of the mantle below EAR with higher resolution than has been available to date by including seismic data recorded by stations from many regional networks ranging from Saudi Arabia to Tanzania. We use relative travel-time tomography to produce P- velocity models from the surface down into the lower mantle incorporating 9250 ray-paths in our model from 495 events and 402 stations. We add smaller earthquakes (4.5 image structures of ~ 100-km length scales to ~ 1000 km depth beneath the northern East-Africa rift (Ethiopia, Eritrea, Djibouti, Yemen) with good resolution also in the transition zone and uppermost lower mantle. Our observations provide evidence that the shallow mantle slow seismic velocities continue trough the transition zone and into the lower mantle. In particular, the relatively slow velocity anomaly beneath the Afar Depression extends up to depths of at least 1000 km depth while another low-velocity anomaly beneath the Main Ethiopian Rift seems to be present in the upper mantle only. These features in the lower mantle are isolated with a diameter of about 400 km indicating deep multiple sources of upwelling that converge in broader low-velocity bodies along the rift axis at shallow

  19. Better Buildings NW Ohio

    Energy Technology Data Exchange (ETDEWEB)

    Moyer, Kevin [Toledo-Lucas County Port Authority, Toledo, OH (United States)

    2015-03-04

    Districts or ESIDs and what is nationally known as Property Assessed Clean Energy or PACE districts and PACE financing. The project methodology followed the identify, develop, implement, monitor and measure format. These districts began in Toledo and adjoining areas and are expanding to TLCPA’s 28 county financing agency geographic footprint. What began as the Toledo Ohio Advanced Energy Improvement Corporation is now doing business as the Northwest Ohio Advanced Energy Improvement District recognizing it expansion into creating and financing other districts in NW Ohio. The program has been sought out as an advisor by major communities and states in the process of developing similar legislation and programs and has become one of the largest most successful PACE energy improvement and financing districts in the US. The program and the energy district focused on transforming energy use, delivery, conservation and renewable energy as “options of first choice”. The significant energy savings paid for many of the improvements and created a financially viable program well beyond the grant period. The program has become a model within the State of Ohio and Nationally on how to implement and finance projects in broad energy districts including how to evolve and integrate several financing methodologies. It is a unique utilization of revolving loan funds and energy bond pooling with revenue backing primarily from energy improvement special assessments on commercial properties along with some power purchase agreement (PPA) and loan agreement revenue. The program has also incorporated Qualified Energy Conservation Bonds, State of Ohio Energy Loans (SEP), utility rebates, solar and renewable energy certificates, renewable tax incentives and grants, and owner funded equity as additional program leverage and funding. Other keys to this success have been a continual simplification and refinement of the application and documentation process to make funding available easily and

  20. African Journal of Marine Science - Vol 26 (2004)

    African Journals Online (AJOL)

    AN ECOSYSTEM FRAMEWORK FOR FISHERIES MANAGEMENT IN THE SOUTHERN BENGUELA UPWELLING SYSTEM · EMAIL FREE FULL TEXT EMAIL FREE FULL ... ACCOUNTING FOR FOOD REQUIREMENTS OF SEABIRDS IN FISHERIES MANAGEMENT – THE CASE OF THE SOUTH AFRICAN PURSE-SEINE ...

  1. Spatio-Temporal Variation in Effects of Upwelling on the Fatty Acid Composition of Benthic Filter Feeders in the Southern Benguela Ecosystem: Not All Upwelling Is Equal.

    Directory of Open Access Journals (Sweden)

    Eleonora Puccinelli

    Full Text Available Variability in mesoscale nearshore oceanographic conditions plays an important role in the distribution of primary production and food availability for intertidal consumers. Advection of nutrient rich waters by upwelling usually allows the proliferation of diatoms, later replaced by dinoflagellates. We examined upwelling effects on the fatty acid (FA signature of a benthic intertidal filter feeder to identify its response to pulsed variability in food availability. The study took place in two contrasting seasons and at two upwelling and two non-upwelling sites interspersed within the southern Benguela upwelling system of South Africa. We investigated the FA composition of the adductor muscles and gonads of the mussel Mytilus galloprovincialis to assess how FA are apportioned to the different tissues and whether this changes between upwelling and non-upwelling conditions. In situ temperature loggers used to identify upwelling conditions at the four sites indicated that such events occurred only at the upwelling centres and only in summer. Tissues differed strongly, with gonads presenting a higher proportion of essential FAs. This could reflect the faster turnover rate of gonad tissue or preferential retention of specific FA for reproductive purposes. FA composition did not vary as a direct function of upwelling, but there were strong dissimilarities among sites. Upwelling influenced mussel diets at one upwelling site while at the other, the expected signature of upwelling was displaced downstream of the core of upwelling. Condition Index (CI and Gonad Index (GI differed among sites and were not influenced by upwelling, with GI being comparable among sites. In addition, FA proportions were consistent among sites, indicating similar food quality and quantity over time and under upwelling and non-upwelling conditions. This suggests that the influence of upwelling on the west coast of South Africa is pervasive and diffuse, rather than discrete; while

  2. Upwelling features near Sri Lanka in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    ShreeRam, P.; Rao, L.V.G.

    , the southwest monsoon in summer and the northeast monsoon in winter. The wind stress associated with these winds cause mass drift of oceanic waters leading to upwelling and downwelling. The upwelling features in the Bay of Bengal with a special mention about...

  3. The Benguela upwelling system lying off southern Africa's west ...

    African Journals Online (AJOL)

    spamer

    The Benguela upwelling system lying off southern. Africa's west coast is one of the world's four main upwelling systems (Parrish et al. 1983). Its physical characteristics have been summarized by Nelson and. Hutchings (1983), Shannon (1985) and Shannon and. Nelson (1996). It encompasses the entire region that.

  4. Ecological features of harmful algal blooms in coastal upwelling ...

    African Journals Online (AJOL)

    The mass mortalities that accompany anoxia, common to the Benguela and Peru upwelling systems, may be a trophic control mechanism to maintain biogeochemical balance and regional homeostasis, which are vital to upwelling ecosystem dynamics. Some traditional concepts of phytoplankton ecology may not completely

  5. Four large coastal upwelling areas are created by eastern boundary ...

    African Journals Online (AJOL)

    spamer

    Four large coastal upwelling areas are created by eastern boundary currents along the west coasts of. Africa and the Americas (Fig. 1). Upwelling regions are strongly influenced by the physical environment, which provides the nutrient-rich, bright-light conditions necessary for productive plant growth. The primary production ...

  6. Although most of the phytoplankton of the Benguela upwelling ...

    African Journals Online (AJOL)

    spamer

    Red tides are common and usually attributed to members of the Dinophyceae, most of .... Red tide forms and impacts on the coast, following relax- ation of upwelling. As wind stress decreases during the quiescent phase of upwelling, cross-shelf currents become ..... syndrome that results in short-term memory loss in victims ...

  7. Ekman estimates of upwelling at cape columbine based on ...

    African Journals Online (AJOL)

    Ekman estimates of upwelling at cape columbine based on measurements of longshore wind from a 35-year time-series. AS Johnson, G Nelson. Abstract. Cape Columbine is a prominent headland on the south-west coast of Africa at approximately 32°50´S, where there is a substantial upwelling tongue, enhancing the ...

  8. Zooplankton biomass data (displacement volume, wet mass, and dry mass) collected by the Sea Fisheries Research Institute (SFRI) in the active upwelling zone on the west coast of South Africa 1969-12-02 to 1969-12-16 (NODC Accession 0071850)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton biomass data (displacement volume, wet mass, and dry mass) collected by South African the Sea Fisheries Research Institute (SFRI) during SFRI upwelling...

  9. The Triassic upwelling system of Arctic Alaska

    Science.gov (United States)

    Yurchenko, I.; Graham, S. A.

    2017-12-01

    The Middle to Upper Triassic Shublik Formation of Arctic Alaska is a laterally and vertically heterogeneous rock unit that has been analyzed both in outcrop and in the subsurface. The Shublik Formation sediments are distinguished by a characteristic set of lithologies that include glauconitic, phosphatic, organic-rich, and cherty facies consistent with a coastal upwelling zone deposition interpretation. It is often recognized by abundance of impressions and shells of distinctive Triassic bivalves. To understand main controls on lithofacies distributions, this study reviews and refines lithologic and paleoenvironmental interpretations of the Shublik Formation, and incorporates the newly acquired detailed geochemical analyses of two complete Shublik cores. This work focuses on organic geochemistry (analyses of biomarkers and diamondoids), chemostratigraphy (hand-held XRF), and iron speciation analysis to reconstruct paleoproductivity and redox conditions. Based on the available evidence, during Shublik deposition, an upwelling-influenced open shelf resulted in high nutrient supply that stimulated algal blooms leading to high net organic productivity, reduced water transparency, oxygen deficiency, and water column stratification. Evidence of such eutrophic conditions is indicated by the lack of photic benthic organisms, bioturbation and trace fossils, and dominance of the monospecific light-independent epibenthic bivalves. The flat, subcircular, thin shells of these carbonate-secreting organisms allowed them to adapt to dysoxic conditions, and float on soft, soupy, muddy substrate. The distinctive clay- and organic-rich facies with abundant bivalves occurred on the mid to outer stable broad shelf, and were deposited when organic productivity at times overlapped with periods of increased siliciclastic input controlled by sea level and changes in local sediment dispersal systems, and therefore are more spatially and temporally localized than the widespread clay

  10. The growth season of Dinophysis acuminata in an upwelling system embayment: A conceptual model based on in situ measurements

    Science.gov (United States)

    Velo-Suárez, L.; González-Gil, S.; Pazos, Y.; Reguera, B.

    2014-03-01

    The distribution and physiological condition of the DSP-toxin producer Dinophysis acuminata, its relation with accompanying microplankton populations and coupling with upwelling events are described based on weekly sampling at a fixed station in Ría de Pontevedra, Galician Rías Baixas, NW Spain between March and December 2007. D. acuminata was detected from 18 June to 01 October. The appearance of D. acuminata in the Ría coincided with an upwelling-relaxation event and a short-lived maximum (up to 27 000 cells L-1) of its potential prey, the phototrophic ciliate Mesodinium cf rubrum. An increase in the proportion of vacuolated Dinophysis cells (72%) observed one week later suggests that the bloom was triggered by heterotrophic feeding on a co-occurring peak of Mesodinium coupled with advection of Dinophysis cells into the ría. Elevated frequencies of cells with starch and vacuoles were closely associated with the presence of M. cf rubrum during the entire bloom season. However, peaks in the frequency of vacuolated cells were only recorded on a few occasions, suggesting that D. acuminata is prey-limited most of the time but does not require a constant supply of prey for long term survival. Infection of D. acuminata by the parasite dinoflagellate Amoebophrya sp., a potential loss factor in the population dynamics of dinoflagellate populations, was observed (1-17% prevalence) immediately prior to the decline of the bloom. A conceptual model is presented of the mechanisms by which D. acuminata blooms develop in a ría influenced by upwelling which utilizes a combination of physics (upwelling-promoted shoreward transport of Dinophysis inoculum) and the match-mismatch of predator-prey (Dinophysis and Mesodinium) populations.

  11. The Benguela upwelling ecosystem lies adjacent to the south ...

    African Journals Online (AJOL)

    denise

    The Benguela upwelling ecosystem lies adjacent to the south-western coast of Africa, from southern Angola. (15°S) to Cape Agulhas (35°S; Fig. 1). Ecologically, it is split into separate northern and southern sub- systems by a zone of intense perennial upwelling near. Lüderitz (26–27.5°S; Shannon 1985). As is charac-.

  12. Reconstructing Holocene Upwelling Conditions in Monterey Bay, California

    Science.gov (United States)

    Owen, P. W.; Wagner, A. J.; Addison, J. A.; Schwartz, V.; Barron, J. A.; Carlin, J. A.

    2017-12-01

    Upwelling along the eastern margin of the North Pacific is vital to the California Current System (CCS) and is a major contributing factor to the diverse marine ecosystems along the US West Coast. Prior studies hypothesize climate change will accelerate the alongshore equatorward winds that drive coastal upwelling, with the greatest increase in upwelling occurring within the poleward portion (N of 40°N) of the CCS. However, other studies have suggested that future upwelling changes in the southern portion (S of 35°N) of the CCS are less certain. Here we present a geological perspective into past Holocene upwelling along the central California coast from the Monterey Bay National Marine Sanctuary to provide a potential analogue for future upwelling conditions and a deeper understanding of CCS dynamics. A smear slide analysis of marine sediment cores taken from [1] the Pioneer Seamount off the Central California coast, [2] offshore of Pt. Año Nuevo, and [3] near the mouth of the Salinas River shows varying percentages of biogenic and terrigenous sediments during the past 11,000 years, with a shift toward greater biogenic silica sediments occurring approximately 3,000 cal yrs BP in the offshore site. In addition, an analysis of the diatom assemblages is used as a proxy for upwelling conditions. Preliminary results suggest a greater abundance of F. doliolus, a diatom species commonly used as a proxy for increased productivity and upwelling, occurs around 3,500 cal years BP. These results are then compared to existing calibrated X-ray computed tomography (CT) bulk density, total organic carbon (TOC), and biogenic silica (opal) measurements during periods of known climatic variability such as the Holocene Climate Optimum, Medieval Warm Period and Little Ice Age. Our results can provide a new high-resolution study of the central CCS throughout the Holocene, and give us a better understanding as to how future oceanic conditions may change the marine ecosystems along

  13. ENSO and the California Current coastal upwelling response

    Science.gov (United States)

    Jacox, Michael G.; Fiechter, Jerome; Moore, Andrew M.; Edwards, Christopher A.

    2015-03-01

    A 31 year (1980-2010) sequence of historical analyses of the California Current System (CCS) is used to describe the central CCS (35-43˚N) coastal upwelling response to El Niño-Southern Oscillation (ENSO) variability. The analysis period captures 10 El Niño and 10 La Niña events, including the extreme El Niños of 1982-1983 and 1997-1998. Data-assimilative model runs and backward trajectory calculations of passive tracers are used to elucidate physical conditions and source water characteristics during the upwelling season of each year. In general, El Niño events produce anomalously weak upwelling and source waters that are unusually shallow, warm, and fresh, while La Niña conditions produce the opposite. Maximum vertical transport anomalies in the CCS occur ˜1 month after El Niño peaks in midwinter, and before the onset of the upwelling season. Source density anomalies peak later than transport anomalies and persist more strongly through the spring and summer, causing the former to impact the upwelling season more directly. As nitrate concentration covaries with density in the central CCS, El Niño may exert more influence over the nitrate concentration of upwelled waters than it does over vertical transport, although both factors are expected to reduce nitrate supply during El Niño events. Interannual comparison of individual diagnostics highlights their relative impacts during different ENSO events, as well as years deviating from the canonical response to ENSO variability. The net impact of ENSO on upwelling is explored through an "Upwelling Efficacy Index", which may be a useful indicator of bottom-up control on primary productivity.

  14. Pliocene Warm Period Upwelling in the Southern Benguela Region

    Science.gov (United States)

    Petrick, B. F.; McClymont, E.; Felder, S.; Leng, M. J.; Rosell Mele, A.; Rueda, G.

    2014-12-01

    The mid-Pliocene has been proposed as a possible analogue for understanding future climate change and testing climate models. Previous work has shown that during the Pliocene the major upwelling systems were relatively warm, and thus either inactive, contracted, or upwelling warmer waters than present. Here we examine evidence from a core site located on the margins of the modern Benguela upwelling system, to test whether the upwelling cells had migrated or contracted relative to present during the Pliocene. We applied several organic geochemistry proxies and foraminiferal analyses to reconstruct the Pliocene history of ODP site 1087 (31º28'S, 15º19'E, 1374m water depth), including the UK37' index and TEX86 index (for reconstructing sea surface temperatures), chlorins (for estimating primary productivity) and planktonic foraminifera assemblages (for inferring water mass changes). These proxies show that between 3.5 and 3.0 Ma the southern Benguela region was significantly cooler than the northern Benguela region, the latter where the main upwelling cells are found today. Coupled with higher primary production, a shift in planktonic foraminifera assemblage, and an offset between the UK37' index and TEX86 index, we infer that more extensive upwelling was present in the southern Benguela region during the Pliocene. We infer that the main Benguela upwelling cells had shifted southward relative to today, as a result of changes in the local wind field. We find evidence for pronounced cooling and a shift in the planktonic foraminifera assemblage during the M2 and KM2 glacial stages, showing a sensitivity of Benguela upwelling to these short-lived climate events.

  15. Trends in the number of extreme hot SST days along the Canary Upwelling System due to the influence of upwelling

    Directory of Open Access Journals (Sweden)

    Xurxo Costoya

    2014-07-01

    Full Text Available Trends in the number of extreme hot days (days with SST anomalies higher than the 95% percentile were analyzed along the Canary Upwelling Ecosystem (CUE over the period 1982- 2012 by means of SST data retrieved from NOAA OI1/4 Degree. The analysis will focus on the Atlantic Iberian sector and the Moroccan sub- region where upwelling is seasonal (spring and summer are permanent, respectively. Trends were analyzed both near coast and at the adjacent ocean where the increase in the number of extreme hot days is higher. Changes are clear at annual scale with an increment of 9.8±0.3 (9.7±0.1 days dec-1 near coast and 11.6±0.2 (13.5±0.1 days dec-1 at the ocean in the Atlantic Iberian sector (Moroccan sub-region. The differences between near shore and ocean trends are especially patent for the months under intense upwelling conditions. During that upwelling season the highest differences in the excess of extreme hot days between coastal and ocean locations (Δn(#days dec-1 occur at those regions where coastal upwelling increase is high. Actually, Δn and upwelling trends have shown to be significantly correlated in both areas, R=0.88 (p<0.01 at the Atlantic Iberian sector and R=0.67 (p<0.01 at the Moroccan sub-region.

  16. Development of the Central-Afar volcanic margin, mantle upwelling and break-up processes

    Science.gov (United States)

    Pik, Raphaël; Bellahsen, Nicolas; Leroy, Sylvie; Stab, Martin; Ayalew, Dereje; Yirgu, Gezahegn

    2017-04-01

    Whereas the present day mantle dynamics is now well imaged by geophysical investigations, the long-term expression of mantle dynamics below rifted lithosphere is not directly recorded at the surface of the earth. Such information must therefore be extracted from non-direct manifestations of mantle upwelling, which are principally (i) the uplift of the upperlying lithosphere and (ii) the melts produced when the solidus of mantle mineral assemblages is crossed. These first order and unique evidences should therefore represent corner stones output of any geodynamic models used to deduce the interplay between mantle dynamics and surface deformations. For magmatism produced during extension of lithosphere, the dynamics of mantle upwelling can be recognized in the volumes of magmas and also in their geochremistry, which allow tracking the various types of mantle sources and the various types of mantle melting regime (P, T and intensity of partial melting). Volcanism has been closely associated with extension in the East African rift system. It is yet (and logically) heterogeneously distributed along the western, eastern and northern volcanic provinces. We have concentrated the efforts of a multidisciplinary team these last years in the northern Ethiopian volcanic province where the most important volumes of volcanism have been emplaced since 30 Ma, from Continental Flood Basalts episode to active extension along the Central Afar magmatic segment. These structural and geochemical data point out new constraints on the interplay between the upwelling of the Afar mantle plume and the style and mechanisms of extension, and imply to update and revise our understanding of the development of this volcanic margin.

  17. Wind-driven upwelling effects on cephalopod paralarvae: Octopus vulgaris and Loliginidae off the Galician coast (NE Atlantic)

    Science.gov (United States)

    Otero, Jaime; Álvarez-Salgado, X. Antón; González, Ángel F.; Souto, Carlos; Gilcoto, Miguel; Guerra, Ángel

    2016-02-01

    Circulation patterns of coastal upwelling areas may have central consequences for the abundance and cross-shelf transport of the larval stages of many species. Previous studies have provided evidences that larvae distribution results from a combination of subtidal circulation, species-specific behaviour and larval sources. However, most of these works were conducted on organisms characterised by small-sized and abundant early life phases. Here, we studied the influence of the hydrography and circulation of the Ría de Vigo and adjacent shelf (NW Iberian upwelling system) on the paralarval abundance of two contrasting cephalopods, the benthic common octopus (Octopus vulgaris) and the pelagic squids (Loliginidae). We sampled repeatedly a cross-shore transect during the years 2003-2005 and used zero inflated models to accommodate the scarcity and patchy distribution of cephalopod paralarvae. The probability of catching early stages of both cephalopods was higher at night. Octopus paralarvae were more abundant in the surface layer at night whereas loliginids preferred the bottom layer regardless of the sampling time. Abundance of both cephalopods increased when shelf currents flowed polewards, water temperature was high and water column stability was low. The probability of observing an excess of zero catches decreased during the year for octopus and at high current speed for loliginids. In addition, the circulation pattern conditioned the body size distribution of both paralarvae; while the average size of the captured octopuses increased (decreased) with poleward currents at daylight (nighttime), squids were smaller with poleward currents regardless of the sampling time. These results contribute to the understanding of the effects that the hydrography and subtidal circulation of a coastal upwelling have on the fate of cephalopod early life stages.

  18. Multiple mantle upwellings through the transition zone beneath the Afar Depression?

    Science.gov (United States)

    Hammond, J. O.; Kendall, J. M.; Stuart, G. W.; Thompson, D. A.; Ebinger, C. J.; Keir, D.; Ayele, A.; Goitom, B.; Ogubazghi, G.

    2012-12-01

    there is no evidence for a plume in the classical sense (i.e. a narrow conduit). Instead, we propose that secondary upwellings rise from the base of the transition zone and connect with the northeast flowing African superswell in the upper mantle.

  19. Wind stress and heat fluxes over a Brazilian Coastal Upwelling

    Science.gov (United States)

    Dourado, Marcelo; Candella, Rogério

    2017-04-01

    Coastal upwelling zones have been intensively studied in the last decades especially due to their importance to the biological cycle. The coastal upwelling system of the Cabo Frio region (east coast of the Rio de Janeiro state, Brazil) keeps the surface water cold during most part of the year, what induces a stable atmospheric boundary layer associated to northeast winds. The main goal of this study is to investigate the wind stress and heat fluxes exchanges between the ocean and the atmosphere in that area. For this purpose, a set of hourly data meteorological and oceanographic data collected by a Wavescan metocean buoy anchored at 23o59S; 42oW, were used, as well as solar radiation and relative humidity from a terrestrial meteorological station from the Instituto Nacional de Meteorologia (InMet). COARE 3.0 algorithm was used to calculate the latent and sensible heat fluxes. In this discussion, positive values represent fluxes towards the ocean. The average net heat flux over our study period is 88 W m-2. The reduction of the net heat flux is due to the increase of the ocean latent heat loss, although a reduction in incoming shortwave radiation and an increase in ocean long wave cooling also contributes. The latent heat is 20 times larger than the sensible heat flux, but the mean value of the latent heat flux, 62 W m-2, is half the typical value found in open ocean. The temporal variability of both sensible and latent heat fluxes reflects their dependence on wind speed and air-sea temperature differences. When upwelling events, here periods when diurnal SST is lower than 18oC, are compared with undisturbed (without upwelling) events, it can be noted the sensible heat fluxes are positives and 10 times greater in magnitude. This is related to an increment, during these upwelling events, of the air-sea temperature difference and an increasing of the wind speed. The cold waters of the upwelling increase the air-sea temperature gradient and, also, the horizontal land

  20. Environmental changes associated with monsoon induced upwelling, off central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DeSousa, S.N.; Sawkar, K.; Rao, P.V.S.S.D.P.

    Coastal upwelling of nutrients during and after the southwest monsoon has been considered to support rich pelagic and demersal fisheries off the west coast of India. Studies indicate occurrence of coastal upwelling assoicated with Ekman transport...

  1. Upwelling Index, 57N 137W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  2. Upwelling Index, 21N 107W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  3. The Benguela upwelling ecosystem lies adjacent to the south ...

    African Journals Online (AJOL)

    denise

    (Grant 1985). The Benguela sardine is a population of the circumglobally distributed Sardinops sagax, additional populations being found in some of the other upwelling ... Off Namibia, signs of a population recovery in the early 1990s were followed ... processes could include environmental forcing, interspecies interactions.

  4. The winter St. Helena climate index and extreme Benguela upwelling

    Science.gov (United States)

    Hagen, Eberhard; Agenbag, Jacobus J.; Feistel, Rainer

    2005-09-01

    Climate changes in the subtropical South-east Atlantic turn out to be well described by the St. Helena Island Climate Index (HIX) and observed fluctuations are in good agreement with inter-decadal variability of the entire South Atlantic Ocean. Year-to-year variations of the averaged austral winter HIX (July-September), representative of the main upwelling season, were compared with (i) corresponding averages of the geostrophic alongshore component of the south-east trade wind (SET) between St. Helena Island in the south-west and Luanda/Angola in the north-east, (ii) the meridional distribution of surface waters colder than 13 °C to characterise intense Benguela upwelling (IBU), and (iii) the meridional position of the Angola-Benguela Frontal Zone (ABFZ) determined by means of sea surface temperature images for offshore distances between 50 and 400 km. Temporal changes of these parameters were investigated and showed that the frequency of consecutive years of strong and relaxed Benguela upwelling is characterised by a quasi-cycle of about 11-14 years. It is proposed that the index of the winter HIX may be used as a 'surveyor's rod' to describe interannual changes in the Benguela upwelling regime as well as those of the embedded marine ecosystem.

  5. Upwelling Index, 60N 149W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  6. Upwelling Index, 33N 119W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  7. Nitrate reducing activity pervades surface waters during upwelling

    Science.gov (United States)

    Fernandes, Sheryl Oliveira; Halarnekar, Reena; Malik, Ashish; Vijayan, Vijitha; Varik, Sandesh; Kumari, Ritu; V. K., Jineesh; Gauns, Manguesh U.; Nair, Shanta; LokaBharathi, P. A.

    2014-09-01

    Nitrate reducing activity (NRA) is known to be mediated by microaerophilic to anaerobic bacteria and generally occurs in the sub-surface waters. However, we hypothesize that NRA could become prominent in the surface waters during upwelling. Hence, we examined nitrification and nitrate reduction along with hydrographic and environmental parameters off Trivandrum and Kochi, south-west-India in June 2010. Shoaling isolines of temperature, density, and nutrients revealed the onset of upwelling off Trivandrum. Shoaling of these signatures was absent in the northern transect off Kochi. The degree of nutrient consumption (DNC) was low emphasizing the presence of newly upwelled water off Trivandrum. A significant increase in NRA (df = 1, p < 0.05) was observed off Trivandrum than at Kochi. Moreover, as hypothesized, NRA at Trivandrum was pronounced at the surface with a maximum rate of 0.85 (± 0.02) μmol L1 h- 1 nearshore which was ~ 29 × higher than that at Kochi. Further, an inverse relationship between NRA and NO3- concentration (n = 34, r = - 0.415, p < 0.01) suggested transformation of the upwelled nutrient. Nitrification/NRA was ~ 10 × lower at 0.28 off Trivandrum indicating a discernible shift towards reduction. Such contribution from bacterial activity could be a response towards restoration of homeostasis.

  8. Diet of sardine Sardinops sagax in the southern Benguela upwelling ...

    African Journals Online (AJOL)

    Diet of sardine Sardinops sagax in the southern Benguela upwelling ecosystem. ... type was assessed by calculating the carbon content of prey items. Sardine is an omnivorous clupeoid, ingesting both phytoplankton and zooplankton, with the relative importance of these two food types varying both spatially and temporally.

  9. Nutrients, Recycling, and Biological Populations in Upwelling Ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T. E.

    1980-01-01

    Nutrient recycling has been studied in the upwelling areas of Baja California, Northwest Africa, and Peru. Regeneration by biological populations in these areas contributes significant quantities of recycled nitrogen which is utilized in productivity processes. Each area has a different combination of organisms which leads to differences in the relative contributions of zooplankton, nekton, or benthos to the nutrient cycles. Comparisons of ammonium regeneration rates of zooplankton and nekton-micronekton populations in the three upwelling areas show that zooplankton recycle relatively less nitrogen in the Baja California and Peru systems than nekton. In the Northwest Africa upwelling region, however, zooplankton, fish, and benthic inputs are all substantial. In recent years the Peruvian upwelling system has been altered with the decline of the anchoveta population and an increase in the importance of zooplankton in nutrient recycling. The distribution of recycled nitrogen (ammonium and urea) in transects across the shelf at 10°S and 15°S indicates that regeneration is relatively more important at 10°S in the region of the wide shelf. In both areas the distribution of ammonium and urea are not entirely coincident thereby indicating differences in their production and/or utilization.

  10. On an upwelling front, propagation of upwelling and vertical velocity in the eastern Arabian sea during monsoon, 1987

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Unnikrishnan, A.S.

    A coastal upwelling front parallel to the coast and identifiable upto a depth of 75 m was observed between 12.5 and 16 degrees N along the eastern Arabian Sea in September, 1987 from closely spaced digital BT data. With a north-south slope...

  11. Dinoflagellate blooms in upwelling systems: Seeding, variability, and contrasts with diatom bloom behaviour

    Science.gov (United States)

    Smayda, T. J.; Trainer, V. L.

    2010-04-01

    The influence of diatom bloom behaviour, dinoflagellate life cycles, propagule type and upwelling bloom cycles on the seeding of dinoflagellate blooms in eastern boundary current upwelling systems is evaluated. Winter-spring diatom bloom behaviour is contrasted with upwelling bloom behaviour because their phenology impacts dinoflagellate blooms. The winter-spring diatom bloom is usually sustained, whereas the classical upwelling diatom bloom occurs as a series of separate, recurrent mini-blooms intercalated by upwelling-relaxation periods, during which dinoflagellates often bloom. Four sequential wind-regulated phases characterize upwelling cycles, with each phase having different effects on diatom and dinoflagellate bloom behaviour: bloom “spin up”, bloom maximum, bloom “spin down”, and upwelling relaxation. The spin up - bloom maximum is the period of heightened diatom growth; the spin down - upwelling-relaxation phases are the periods when dinoflagellates often bloom. The duration, intensity and ratio of the upwelling and relaxation periods making up upwelling cycles determine the potential for dinoflagellate blooms to develop within a given upwelling cycle and prior to the subsequent “spin up” of upwelling that favours diatom blooms. Upwelling diatoms and meroplanktonic dinoflagellates have three types of propagules available to seed blooms: vegetative cells, resting cells and resting cysts. However, most upwelling dinoflagellates are holoplanktonic, which indicates that the capacity to form resting cysts is not an absolute requirement for growth and survival in upwelling systems. The long-term (decadal) gaps in bloom behaviour of Gymnodinium catenatum and Lingulodinium polyedrum, and the unpredictable bloom behaviour of dinoflagellates generally, are examined from the perspective of seeding strategies. Mismatches between observed and expected in situ bloom behaviour and resting cyst dynamics are common among upwelling dinoflagellates. This

  12. NW CSC annual report fiscal year 2013

    Science.gov (United States)

    Bisbal, Gustavo A.

    2013-01-01

    The Northwest Climate Science Center (NW CSC) was established in 2010 as one of eight regional Climate Science Centers created by the Department of the Interior (DOI). The NW CSC encompasses Washing-ton, Oregon, Idaho, and western Montana and has overlapping boundaries with three Landscape Conservation Cooperatives (LCCs): the Great Northern, the Great Basin, and the North Pacific. With guidance from its Executive Stakeholder Advisory Committee (ESAC), the NW CSC and its partner LCCs are addressing the highest priority regional climate science needs of Northwest natural and cultural resource managers. Climate Science Centers tap into the scientific expertise of both the U.S. Geological Survey (USGS) and academic institutions. The NW CSC is supported by an academic consortium with the capacity to generate climate science and tools in a coordinated fashion, serving stakeholders across the Northwest region. This consortium is primarily represented by Oregon State University (OSU), the University of Id-ho (UI), and the University of Washington (UW). The academic consortium and USGS provide capabilities in climate science, ecology, impacts and vulnerability assessment, modeling, adaptation planning, and advanced information technology, all necessary to address and respond to climate change in the Northwest. University members also recruit and train graduate students and early-career scientists. This Annual Report summarizes progress for the goals set out in the NW CSC Strategic Plan for 2012-2015 (http://www.doi.gov/csc/northwest/upload/Northwest-CSC-Strategic-Plan.cfm) and the NW CSC Work-plan for Fiscal Year (FY) 2013 (October 1, 2012 through September 30, 2013). The report follows the structure of the Strategic Plan, which describes the five core services (Executive, Science, Data, Communications, and Education and Training) provided by the NW CSC in support of the stated vision: Our Vision: To become nationally recognized as a best-practice model for the provision

  13. Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

    Energy Technology Data Exchange (ETDEWEB)

    Pease, Leonard F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bamberger, Judith A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Minette, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-02-28

    This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from jets characteristic of pulse jet mixers (PJMs) has been analyzed, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell break through? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g., six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored.

  14. Coastal upwelling in the Gelendzhik area of the Black Sea: Effect of wind and dynamics

    Science.gov (United States)

    Silvestrova, K. P.; Zatsepin, A. G.; Myslenkov, S. A.

    2017-07-01

    Long series data of a thermistor chain in the Black Sea coastal zone near Gelendzhik were analyzed. A thermistor chain installed 1 km offshore and at a depth of 22 m. There are full and incomplete upwelling events observed. The study of upwelling genesis based on: wind speed data from the NCEP/CFSR reanalysis and Gelendzhik weather station, velocity and direction of coastal currents measured by ADCP profiler moored on the bottom near the thermistor chain. Over the whole observation period (warm seasons of 2013-2015), more than 40 events of upwelling were registered four of them were full upwellings, when presence of under-thermocline water was observed near the sea surface. For every upwelling event, conditions prior to the changes in thermic structure, were analyzed. It is found that full upwelling generally occur under synergistic wind and current forcing. Fairly strong forcing of one of these factors is sufficient for partial upwelling to occur.

  15. Continuous eclogite melting and variable refertilisation in upwelling heterogeneous mantle.

    Science.gov (United States)

    Rosenthal, Anja; Yaxley, Gregory M; Green, David H; Hermann, Joerg; Kovács, István; Spandler, Carl

    2014-08-18

    Large-scale tectonic processes introduce a range of crustal lithologies into the Earth's mantle. These lithologies have been implicated as sources of compositional heterogeneity in mantle-derived magmas. The model being explored here assumes the presence of widely dispersed fragments of residual eclogite (derived from recycled oceanic crust), stretched and stirred by convection in the mantle. Here we show with an experimental study that these residual eclogites continuously melt during upwelling of such heterogeneous mantle and we characterize the melting reactions and compositional changes in the residue minerals. The chemical exchange between these partial melts and more refractory peridotite leads to a variably metasomatised mantle. Re-melting of these metasomatised peridotite lithologies at given pressures and temperatures results in diverse melt compositions, which may contribute to the observed heterogeneity of oceanic basalt suites. We also show that heterogeneous upwelling mantle is subject to diverse local freezing, hybridization and carbonate-carbon-silicate redox reactions along a mantle adiabat.

  16. Meteorological constraints on oceanic halocarbons above the Peruvian Upwelling

    OpenAIRE

    S. Fuhlbrügge; B. Quack; E. Atlas; A. Fiehn; H. Hepach; K. Krüger

    2015-01-01

    Halogenated very short lived substances (VSLS) are naturally produced in the ocean and emitted to the atmosphere. Recently, oceanic upwelling regions in the tropical East Atlantic were identified as strong sources of brominated halocarbons to the atmosphere. During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (M...

  17. Meteorological constraints on oceanic halocarbons above the Peruvian upwelling

    OpenAIRE

    Fuhlbrügge, Steffen; Quack, Birgit; Atlas, Elliot; Fiehn, Alina; Hepach, Helmke; Krüger, Kirstin

    2016-01-01

    During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL) were investigated above the Peruvian upwelling. This study presents novel observations of the three very short lived substances (VSLSs) – bromoform, dibromomethane and methyl iodide – together with high-resolution meteorological measurements, Lagrangian transport and source–loss calculations. ...

  18. Meteorological constraints on oceanic halocarbons above the Peruvian upwelling

    Directory of Open Access Journals (Sweden)

    S. Fuhlbrügge

    2016-09-01

    Full Text Available During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL were investigated above the Peruvian upwelling. This study presents novel observations of the three very short lived substances (VSLSs – bromoform, dibromomethane and methyl iodide – together with high-resolution meteorological measurements, Lagrangian transport and source–loss calculations. Oceanic emissions of bromoform and dibromomethane were relatively low compared to other upwelling regions, while those for methyl iodide were very high. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting as strong barriers for convection and vertical transport of trace gases in this region. Observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height correlated well during the cruise. We used a simple source–loss estimate to quantify the contribution of oceanic emissions along the cruise track to the observed atmospheric concentrations. This analysis showed that averaged, instantaneous emissions could not support the observed atmospheric mixing ratios of VSLSs and that the marine background abundances below the trade inversion were significantly influenced by advection of regional sources. Adding to this background, the observed maximum emissions of halocarbons in the coastal upwelling could explain the high atmospheric VSLS concentrations in combination with their accumulation under the distinct MABL and trade inversions. Stronger emissions along the nearshore coastline likely added to the elevated abundances under the steady atmospheric conditions. This study underscores the importance of oceanic upwelling and trade wind systems on the atmospheric distribution of marine VSLS emissions.

  19. Meteorological constraints on oceanic halocarbons above the Peruvian upwelling

    Science.gov (United States)

    Fuhlbrügge, Steffen; Quack, Birgit; Atlas, Elliot; Fiehn, Alina; Hepach, Helmke; Krüger, Kirstin

    2016-09-01

    During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL) were investigated above the Peruvian upwelling. This study presents novel observations of the three very short lived substances (VSLSs) - bromoform, dibromomethane and methyl iodide - together with high-resolution meteorological measurements, Lagrangian transport and source-loss calculations. Oceanic emissions of bromoform and dibromomethane were relatively low compared to other upwelling regions, while those for methyl iodide were very high. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting as strong barriers for convection and vertical transport of trace gases in this region. Observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height correlated well during the cruise. We used a simple source-loss estimate to quantify the contribution of oceanic emissions along the cruise track to the observed atmospheric concentrations. This analysis showed that averaged, instantaneous emissions could not support the observed atmospheric mixing ratios of VSLSs and that the marine background abundances below the trade inversion were significantly influenced by advection of regional sources. Adding to this background, the observed maximum emissions of halocarbons in the coastal upwelling could explain the high atmospheric VSLS concentrations in combination with their accumulation under the distinct MABL and trade inversions. Stronger emissions along the nearshore coastline likely added to the elevated abundances under the steady atmospheric conditions. This study underscores the importance of oceanic upwelling and trade wind systems on the atmospheric distribution of marine VSLS emissions.

  20. Determining correlation between Emerita analoga recruitment and coastal upwelling (Invited)

    Science.gov (United States)

    Wong, K.; Godoy, E.; Dean, A.; Johnson, R.

    2009-12-01

    Since 2003, Careers in Science (CiS) interns have been participating in the Farallones Marine Sanctuary Association's Long-term Monitoring Program and Experiential Training for Students (LiMPETS) program monitoring populations of Emerita analoga, the Pacific mole crab. The CiS intern program at the California Academy of Sciences is a multi-year, year-round work-based science education and youth development program for young people from groups typically under-represented in the sciences. E. analoga, an inhabitant of sandy beach swash zone, plays an essential role in marine food webs. Recent studies have suggested E. analoga to be indicators of DDT and domoic acid in the ecosystem. My peers and I collected E. analoga to determine population demographics, including size and sex. On a weekly basis during the months of June, July and August, at San Francisco’s Ocean Beach in Golden Gate National Recreational Area we systematically collect live samples and data for the population monitoring. From June to August 2009, field observations indicated the most abundant E. analoga recruit populations since 2003. After observing this change, we wanted to find possible causes for the increase in recruits. We hypothesized that there was a correlation between recruit population and coastal upwelling events because of the increased nutrient availability due to the events. We compared recruit population data from 2003 through 2009 to upwelling anomalies off the coast of San Francisco. We did not find an increased recruit population 4 to 5 months after an upwelling event, which is the time needed for E. analoga to develop from its planktonic stage to a recruit. One implication of our comparison is that upwelling events cannot be directly correlated with successful recruiting of E. analoga.

  1. Nutrient pumping by submesoscale circulations in the mauritanian upwelling system

    Science.gov (United States)

    Hosegood, P. J.; Nightingale, P. D.; Rees, A. P.; Widdicombe, C. E.; Woodward, E. M. S.; Clark, D. R.; Torres, R. J.

    2017-12-01

    Observations made within a cold filament in the Mauritanian upwelling system demonstrate that intense submesoscale circulations at the peripheral edges of the filament are likely responsible for anomalously high levels of observed primary productivity by resupplying nutrients to the euphotic zone. Measurements made on the shelf within the recently upwelled water reveal that primary production (PP) of 8.2 gC/m-2 day-1 was supported by nitrate concentrations (NC) of 8 mmol m-3. Towards the front that defined the edge of the filament containing the upwelled water as it was transported offshore, PP dropped to 1.6 gC m-2 day-1 whilst NC dropped to 5.5 mmol m-3. Thus, whilst the observed nutrients on the shelf accounted for 90% of new production, this value dropped to ∼60% near the filament's front after accounting for vertical turbulent fluxes and Ekman pumping. We demonstrate that the N15 was likely to have been supplied at the front by submesoscale circulations that were directly measured as intense vertical velocities ⩾100 m day-1 by a drifting acoustic Doppler current profiler that crossed a submesoscale surface temperature front. At the same time, a recently released tracer was subducted out of the mixed layer within 24 h of release, providing direct evidence that the frontal circulations were capable of accessing the reservoir of nutrients beneath the pycnocline. The susceptibility of the filament edge to submesoscale instabilities was demonstrated by O(1) Rossby numbers at horizontal scales of 1-10 km. The frontal circulations are consistent with instabilities arising from a wind-driven nonlinear Ekman buoyancy flux generated by the persistent northerly wind stress that has a down-front component at the northern edge of the inshore section of the filament. The prevalence of submesoscale instabilities and their associated vertical circulations are proposed to be a key mechanism operating at sub-grid scales and sustaining new production throughout the upwelling

  2. Patterns of copepod diversity in the Chilean coastal upwelling system

    Science.gov (United States)

    Hidalgo, Pamela; Escribano, Ruben; Vergara, Odette; Jorquera, Erika; Donoso, Katty; Mendoza, Paula

    2010-12-01

    The copepod community structure from the Northern and Central/southern upwelling regions off Chile was studied and compared. The derived community descriptors were species abundance (N), species richness (R) and the Shannon-Wiener diversity index (H'). These descriptors were related to distinct habitats and conditions, sea surface temperature (SST) and depth of the upper boundary of the oxygen minimum zone (OMZ). From 159 samples, obtained between 2002 and 2008, a total number of 118 species were found of which the calanoids Paracalanus indicus, Acartia tonsa and Eucalanus inermis, along with the cyclopoid Oithona similis, and the poecilostomatoids Triconia conifera and Oncaea media were the dominant species. H' was higher in the northern region, but no differences in N and R were detected between regions. N was higher in the epipelagic vs the deep habitat, but R and H' did not differ. N, R and H' correlated positively to SST and negatively to OMZ depth. The ascent of the OMZ to the upper layer forced by upwelling was proposed as a mechanism that aggregates and increases copepod diversity in the food-rich photic zone. All these findings suggest a fundamental role of upwelling variation for modulating copepod dynamics and community structure in this highly productive but strongly variable marine ecosystem.

  3. Convective upwelling in the mantle beneath the Gulf of California.

    Science.gov (United States)

    Wang, Yun; Forsyth, Donald W; Savage, Brian

    2009-11-26

    In the past six million years, Baja California has rifted obliquely apart from North America, opening up the Gulf of California. Between transform faults, seafloor spreading and rifting is well established in several basins. Other than hotspot-dominated Iceland, the Gulf of California is the only part of the world's seafloor-spreading system that has been surrounded by enough seismometers to provide horizontal resolution of upper-mantle structure at a scale of 100 kilometres over a distance great enough to include several spreading segments. Such resolution is needed to address the long-standing debate about the relative importance of dynamic and passive upwelling in the shallow mantle beneath spreading centres. Here we use Rayleigh-wave tomography to image the shear velocity in the upper 200 kilometres or so of the mantle. Low shear velocities similar to those beneath the East Pacific Rise oceanic spreading centre underlie the entire length of the Gulf, but there are three concentrated locations of anomalously low velocities spaced about 250 kilometres apart. These anomalies are 40 to 90 kilometres beneath the surface, at which depths petrological studies indicate that extensive melting of passively upwelling mantle should begin. We interpret these seismic velocity anomalies as indicating that partial melting triggers dynamic upwelling driven by either the buoyancy of retained melt or by the reduced density of depleted mantle.

  4. Adjoint sensitivity studies of coastal upwelling at northeast of Taiwan

    Science.gov (United States)

    Gopalakrishnan, G.; Cornuelle, B. D.; Hoteit, I.

    2010-12-01

    The north Pacific western boundary current (Kuroshio) begins to the east of the Philippines, crosses the Luzon strait and flows northward close to the Taiwan coast following the continental shelf. The Kuroshio shows occasional splitting near the shelf northeast of Taiwan where one branch carries Kuroshio waters onto the shelf north of Taiwan while the major part flows along the shelf oriented in the east-west direction. Previous modeling and observational studies of the Kuroshio near the Taiwan coast showed that during summer (May - September) the core of the Kuroshio moves offshore by 100 km, while during winter (October - April) Kuroshio waters flows closer to the Taiwan coast. Another interesting phenomenon is the occurrences of cold waters ”cold-dome” just northeast of Taiwan, which is closely associated with the seasonal migration of Kuroshio waters. Cold water upwells in this area during summer, associated with cyclonic eddies. This patch of cold water can be clearly distinguished from surrounding warm waters in satellite sea-surface temperature (SST) maps. This seasonal upwelling is more pronounced during summer, when the axis of the Kuroshio shifts offshore, and is less persistent during winter when the Kuroshio flows closer to the Taiwan coast. A number of five year forward model simulation have been made using realistic forcings, initial conditions and boundary conditions. The forward model simulations have been tested by comparing with satellite measurements of sea-surface height (SSH) and SST. An adjoint-based sensitivity study been performed for the ”cold-dome” upwelling features and northward shelf intrusion of Kuroshio waters at northeast coast of Taiwan. The system uses the Massachusetts Institute of Technology general circulation model (MITgcm) and its adjoint. The goal is to understand the influences on the cold-dome and the shelf intrusions. The adjoint sensitivities of SST, SSH, velocities, and transport were computed with respect to

  5. Holocene variability in the intensity of wind-gap upwelling in the tropical eastern Pacific

    Science.gov (United States)

    Toth, Lauren T.; Aronson, Richard B.; Cheng, Hai; Edwards, R. Lawrence

    2015-01-01

    Wind-driven upwelling in Pacific Panamá is a significant source of oceanographic variability in the tropical eastern Pacific. This upwelling system provides a critical teleconnection between the Atlantic and tropical Pacific that may impact climate variability on a global scale. Despite its importance to oceanographic circulation, ecology, and climate, little is known about the long-term stability of the Panamanian upwelling system or its interaction with climatic forcing on millennial time scales. Using a combination of radiocarbon and U-series dating of fossil corals collected in cores from five sites across Pacific Panamá, we reconstructed the local radiocarbon reservoir correction, ΔR, from ~6750 cal B.P. to present. Because the ΔR of shallow-water environments is elevated by upwelling, our data set represents a millennial-scale record of spatial and temporal variability of the Panamanian upwelling system. The general oceanographic gradient from relatively strong upwelling in the Gulf of Panamá to weak-to-absent upwelling in the Gulf of Chiriquí was present throughout our record; however, the intensity of upwelling in the Gulf of Panamá varied significantly through time. Our reconstructions suggest that upwelling in the Gulf of Panamá is weak at present; however, the middle Holocene was characterized by periods of enhanced upwelling, with the most intense upwelling occurring just after of a regional shutdown in the development of reefs at ~4100 cal B.P. Comparisons with regional climate proxies suggest that, whereas the Intertropical Convergence Zone is the primary control on modern upwelling in Pacific Panamá, the El Niño–Southern Oscillation drove the millennial-scale variability of upwelling during the Holocene.

  6. Modelling Ecosystem Dynamics of the Oxygen Minimum Zones in the Angola Gyre and the Northern Benguela Upwelling System.

    Science.gov (United States)

    Schmidt, M.; Eggert, A.

    2016-02-01

    The Angola Gyre and the Northern Benguela Upwelling System are two major oxygen minimum zones (OMZ) of different kind connected by the system of African Eastern Boundary Currents. We discuss results from a 3-dimensional coupled biogeochemical model covering both oxygen-deficient systems. The biogeochemical model component comprises trophic levels up to zooplankton. Physiological properties of organisms are parameterized from field data gained mainly in the course of the project "Geochemistry and Ecology of the Namibian Upwelling System" (GENUS). The challenge of the modelling effort is the different nature of both systems. The Angola Gyre, located in a "shadow zone" of the tropical Atlantic, has a low productivity and little ventilation, hence a long residence time of water masses. In the northern Benguela Upwelling System, trade winds drive an intermittent, but permanent nutrient supply into the euphotic zone which fuels a high coastal productivity, large particle export and high oxygen consumption from dissimilatory processes. In addition to the local processes, oxygen-deficient water formed in the Angola Gyre is one of the source water masses of the poleward undercurrent, which feeds oxygen depleted water into the Benguela system. In order to simulate the oxygen distribution in the Benguela system, both physical transport as well as local biological processes need to be carefully adjusted in the model. The focus of the analysis is on the time scale and the relative contribution of the different oxygen related processes to the oxygen budgets in both the oxygen minimum zones. Although these are very different in both the OMZ, the model is found as suitable to produce oxygen minimum zones comparable with observations in the Benguela and the Angola Gyre as well. Variability of the oxygen concentration in the Angola Gyre depends strongly on organismic oxygen consumption, whereas the variability of the oxygen concentration on the Namibian shelf is governed mostly by

  7. Coastal upwelling seasonality and variability of temperature and chlorophyll in a small coastal embayment

    Science.gov (United States)

    Walter, Ryan K.; Armenta, Kevin J.; Shearer, Brandon; Robbins, Ian; Steinbeck, John

    2018-02-01

    While the seasonality of wind-driven coastal upwelling in eastern boundary upwelling systems has long been established, many studies describe two distinct seasons (upwelling and non-upwelling), a generalized framework that does not capture details relevant to marine ecosystems. In this contribution, we present a more detailed description of the annual cycle and upwelling seasonality for an understudied location along the central California coast. Using both the mean monthly upwelling favorable wind stress and the monthly standard deviation, we define the following seasons (contiguous months) and a transitional period (non-contiguous months): "Winter Storms" season (Dec-Jan-Feb), "Upwelling Transition" period (Mar and Jun), "Peak Upwelling" season (Apr-May), "Upwelling Relaxation" season (Jul-Aug-Sep), and "Winter Transition" season (Oct-Nov). In order to describe the oceanic response to this upwelling wind seasonality, we take advantage of nearly a decade of full water-column measurements of temperature and chlorophyll made using an automated profiling system at the end of the California Polytechnic State University Pier in San Luis Obispo Bay, a small ( 2 km wide near study site) and shallow ( 10 m average bay depth) coastal embayment. Variability and average-year patterns are described inside the bay during the various upwelling seasons. Moreover, the role of the local coastline orientation and topography on bay dynamics is also assessed using long-term measurements collected outside of the bay. The formation of a seasonally variable upwelling shadow system and potential nearshore retention zone is discussed. The observations presented provide a framework on which to study interannual changes to the average-year seasonal cycle, assess the contribution of higher-frequency features to nearshore variability, and better predict dynamically and ecologically important events.

  8. Jupiter's belts and zones: Contradictory evidence for upwelling and downwelling

    Science.gov (United States)

    Ingersoll, Andrew P.; Juno Science Team

    2017-10-01

    Early authors (Hess and Panofsky 1951, Ingersoll and Cuzzi 1969, Barcilon and Gierasch 1970) noted that the zonal winds are cyclonic in the belts and anticyclonic in the zones. From the thermal wind equation they concluded that the air below the clouds is colder at the belts and warmer at the zones. Hot air rising and cold air sinking led to the notion of downwelling in the belts and upwelling in the zones, which agreed with observations of clear air and low ammonia vapor in the belts and cloudy air and high ammonia vapor in the zones (Gierasch et al. 1986). However, lightning in the belts seemed to contradict that idea, based on the assumption that lightning and convection require upwelling of moist air from below (Little et al. 1999, Ingersoll et al. 2000). Convergence of the eddy momentum flux on the poleward sides of the zones (Salyk et al. 2006) supports the inference based on lightning by implying convergence of the meridional flow in the zones. Here we argue that lightning in the belts does not require upwelling. Instead, there is a threshold for moist convection that is triggered when the thickness of the weather layer drops below a critical value (Li and Ingersoll 2006, Thomson and McIntyre 2016). We also argue that the convergence of the eddy momentum flux does not require equatorward flow. Instead, the meridional flow is controlled by the sign of the potential vorticity (PV) gradient, which is southward on the equatorward sides of the zones (Ingersoll et al. 2017), implying divergence of the meridional flow in the zones. This is a new idea and is based on the observation that the predicted flat parts of the PV staircase (Dritschel and McIntyre 2008), might actually be sloping inward, since the curvature of the zonal velocity profile U_yy exceeds beta at the centers of the westward jets (Ingersoll and Cuzzi 1969, Ingersoll et al. 1981, Limaye et al. 1986, Li et al. 2004, Read et al. 2006). These arguments agree with observations of upwelling in the zones

  9. Surface circulation and upwelling patterns around Sri Lanka

    Science.gov (United States)

    de Vos, A.; Pattiaratchi, C. B.; Wijeratne, E. M. S.

    2014-10-01

    Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean, with the Arabian Sea on its western side and the Bay of Bengal on its eastern side, and experiences bi-annually reversing monsoon winds. Aggregations of blue whale (Balaenoptera musculus) have been observed along the southern coast of Sri Lanka during the northeast (NE) monsoon, when satellite imagery indicates lower productivity in the surface waters. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The model was run for 3 years to examine the seasonal and shorter-term (~10 days) variability. The results reproduced correctly the reversing current system, between the Equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the southwest (SW) monsoon transporting 11.5 Sv (mean over 2010-2012) and the westward flowing Northeast Monsoon Current (NMC) transporting 9.6 Sv during the NE monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the southern coast. During the SW monsoon, the island deflects the eastward flowing SMC southward, whilst along the eastern coast, the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the southern coast, resulting from southward flow converging along the southern coast and subsequent divergence associated with the offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the

  10. Coastal upwelling in Gelendzhik area of the Black sea: wind and dynamics influence.

    Science.gov (United States)

    Silvestrova, Ksenia

    2017-04-01

    This work presents the results of upwelling observations at the coastal zone of the Black Sea near Gelendzhik city. The long series of water temperature (thermochain from 6 to 18 m) were analyzed. The events of full and incomplete upwelling were selected. 5 events from 45 referred to the full upwelling. Under termocline water with a temperature of less than 10° C was observed near the surface. In order to analyze upwelling causes the wind speed from NCEP/CFSR reanalysis and data of the Acoustic Doppler Current Profiler (ADCP) over the period 2013-2015 (mostly warm season) were used. Special upwelling cryteria that consideres wind stress, local baroclinic Rossby radius and thickness of upper mixed layer was calculated. This cryteria allow to estimate role of the wind forcing. Conditions precedent change of the thermal structure are analyzed for each of the upwelling events. It is found that full upwelling preceded by a steady long (more than 2 days) northwest wind. Most of all fixed upwelling events (40%) happened with the synergetic effect of wind and currents. There is also a possibility of local rise of cold waters in submesoscale eddies and advection of these waters with current - such event of full upwelling was recorded in June 2015. This work was supported by Russian Science Founding, grant № 14-17-00382.

  11. The influence of summer upwelling at the western boundary of the Cantabrian coast

    Science.gov (United States)

    Prego, R.; Varela, M.; deCastro, M.; Ospina-Alvarez, N.; Garcia-Soto, C.; Gómez-Gesteira, M.

    2012-02-01

    Recent characterizations of atmospheric conditions favorable to upwelling events in the Western Cantabrian Sea have stressed the need to analyze the significance of the orientation of the coast on the phenomenon of upwelling. Surface-wind fields for the northwestern Galician marine area were provided by the QuikSCAT satellite and an SST map was elaborated using the NASA GHRSST satellite data. A cruise was conducted aboard the RV Lura in June 2009 during northern prevailing winds. Data of thermohaline variables, concentration of dissolved oxygen, dissolved inorganic nitrogen, chlorophyll, dissolved and particulate organic carbon and nitrogen and phytoplankton abundances were obtained. When the upwelling developed west of the Cape Ortegal was strong, the Eastern North Atlantic Central Water mixed with coastal water eastward of the Cape and the upwelled seawater reached the westernmost of the Northern Galician Rias, the Ria of Ortigueira. Incoming seawater was poor in nitrate and chlorophyll concentrations when compared to that of the upwelling events in the Western Galician Rias. The phytoplankton assemblages were typical of summer upwelling blooms in the latter Rias but phytoplankton biomass was lower in the Ria of Ortigueira and the species were indicatives of initial (inner ria under continental influence) and advanced (outer ria under upwelling inputs) stages of phytoplankton succession. The observed process arose when the upwelling edge-zone reaches a change of coastal orientation as may also occur in other upwelling regions.

  12. Submesoscale CO2 variability across an upwelling front off Peru

    Science.gov (United States)

    Köhn, Eike E.; Thomsen, Sören; Arévalo-Martínez, Damian L.; Kanzow, Torsten

    2017-12-01

    As a major source for atmospheric CO2, the Peruvian upwelling region exhibits strong variability in surface fCO2 on short spatial and temporal scales. Understanding the physical processes driving the strong variability is of fundamental importance for constraining the effect of marine emissions from upwelling regions on the global CO2 budget. In this study, a frontal decay on length scales of 𝒪(10 km) was observed off the Peruvian coast following a pronounced decrease in down-frontal (equatorward) wind speed with a time lag of 9 h. Simultaneously, the sea-to-air flux of CO2 on the inshore (cold) side of the front dropped from up to 80 to 10 mmol m-2 day-1, while the offshore (warm) side of the front was constantly outgassing at a rate of 10-20 mmol m-2 day-1. Based on repeated ship transects the decay of the front was observed to occur in two phases. The first phase was characterized by a development of coherent surface temperature anomalies which gained in amplitude over 6-9 h. The second phase was characterized by a disappearance of the surface temperature front within 6 h. Submesoscale mixed-layer instabilities were present but seem too slow to completely remove the temperature gradient in this short time period. Dynamics such as a pressure-driven gravity current appear to be a likely mechanism behind the evolution of the front.

  13. Atmosphere-ocean feedbacks in a coastal upwelling system

    Science.gov (United States)

    Alves, J. M. R.; Peliz, A.; Caldeira, R. M. A.; Miranda, P. M. A.

    2018-03-01

    The COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) modelling system is used in different configurations to simulate the Iberian upwelling during the 2012 summer, aiming to assess the atmosphere-ocean feedbacks in the upwelling dynamics. When model results are compared with satellite measurements and in-situ data, two-way coupling is found to have a moderate impact in data-model statistics. A significant reinforcement of atmosphere-ocean coupling coefficients is, however, observed in the two-way coupled run, and in the WRF and ROMS runs forced by previously simulated SST and wind fields, respectively. The increasing in the coupling coefficient is associated with slight, but potentially important changes in the low-level coastal jet in the atmospheric marine boundary layer. While these results do not imply the need for fully coupled simulations in many applications, they show that in seasonal numerical studies such simulations do not degrade the overall model performance, and contribute to produce better dynamical fields.

  14. Artificial ocean upwelling utilizing the energy of surface waves

    Science.gov (United States)

    Soloviev, Alexander

    2016-04-01

    Artificial upwelling can bring cold water from below the thermocline to the sea surface. Vershinsky, Pshenichnyy, and Soloviev (1987) developed a prototype device, utilizing the energy of surface waves to create an upward flow of water in the tube. This is a wave-inertia pump consisting of a vertical tube, a valve, and a buoy to keep the device afloat. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10 oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. A system of artificial upwelling devices can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from a deeper layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps and climatic consequences are estimated for different environmental conditions using a computational fluid dynamics model.

  15. Towards a management perspective for coastal upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Howe, S.O.; Walsh, J.J.

    1976-01-01

    Data are reviewed from studies on the general distribution of upwelling of coastal waters, associated current patterns, and first order biological effects. Field observations and theory are discussed. Recent research has shown that variability and dynamism are the predominant characteristic features of these regions. Populations related by nonlinear interactions occur in constantly moving patches and swirls subjected to variability in the winds, currents, water chemistry, and solar insolation. Gross stationary features of upwelling communities have been described, but the responses of critical components and their relationships to human or natural perturbations remain poorly defined in this and other types of coastal ecosystems. Large scale research programs recognize that the continental shelf ecosystems are complex event-oriented phenomena. It is postulated that assessment of living resources in an environmental vacuum may lead to mismanagement and hindcasting rather than prescient management. A growing data base encourages the development of computer simulation models of ecosystem relationships and responses will lead to better understanding and management of these and other marine ecosystems in the future. 80 references.

  16. Oceanic contributions from tropical upwelling systems to atmospheric halogens

    Science.gov (United States)

    Ziska, Franziska; Hepach, Helmke; Stemmler, Irene; Quack, Birgit; Atlas, Elliot; Fuhlbrügge, Steffen; Bracher, Astrid; Tegtmeier, Susann; Krüger, Kirstin

    2014-05-01

    Short lived halogenated substances (halocarbons) from the oceans contribute to atmospheric halogens, where they are involved in ozone depletion and aerosol formation. Oceanic regions that are characterized by high biological activity are often associated with increased halocarbon abundance of e.g. bromoform (CHBr3) and dibromomethane (CH2Br2), representing the main contributors to atmospheric organic bromine. Apart from biological production, photochemical pathways play an important role in the formation of methyl iodide (CH3I), the most abundant organoiodine in the marine atmosphere. Recently, the contribution of biogenic diiodomethane (CH2I2) and chloroiodomethane (CH2ClI) to atmospheric organic iodine has been estimated to be similarly significant as CH3I. In the tropics, rapid uplift of surface air can transport these short-lived compounds into the upper troposphere and into the stratosphere. Oceanic upwelling systems off Mauritania, Peru and in the equatorial Atlantic might therefore potentially contribute large amounts of halocarbons to the stratosphere. Concentrations and emissions of iodo- and bromocarbons from several SOPRAN campaigns in different tropical upwelling systems, the Mauritanian and the equatorial upwelling in the Atlantic, as well as the Peruvian upwelling in the Pacific, will be presented. Processes contributing to halocarbon occurrence in the water column, as well as biological and physical factors influencing their emission into the atmosphere are investigated (Fuhlbrügge, et al. 2013; Hepach et al., 2013). We will present the relative contribution of the upwelling systems to global air-sea fluxes from different modelling studies. The data based bottom-up emissions from Ziska et al. (2013) will be compared to model simulated halocarbons. The model is a global three-dimensional ocean general circulation model with an ecosystem model and halocarbon module embedded (MPIOM/HAMOCC). It resolves CH3I and CHBr3 production, degradation, and

  17. AD1995: NW Europe's hydrocarbon industry

    International Nuclear Information System (INIS)

    Glennie, K.; Hurst, A.

    1996-01-01

    This volume concerns itself with wide-ranging aspects of the upstream hydro-carbon industry over the whole of NW Europe. As such, the book contrasts with many thematic volumes by presenting a broad range of topics side-by-side. One section of the book looks back at the history of geological exploration and production, and provides an overview of hydrocarbon exploration across NW Europe. Another section covers the state of the art in hydrocarbon exploration and production. This includes an update on computer-based basin modelling overpressure systems, innovations in reservoir engineering and reserve estimation, 3D seismic and the geochemical aspects of secondary migration. The final section of the book takes a look into the future. This covers the remaining hydrocarbon resources of the North Sea, managing risk in oil field development, oil field economics, and pollution and the environment. It is the editors' hope that several key areas of NW Europe's upstream oil industry have been usefully summarized in the volume. (Author)

  18. Spatio-temporal variability of upwelling along the southwest coast of India based on satellite observations

    Science.gov (United States)

    Jayaram, Chiranjivi; Kumar, P. K. Dinesh

    2018-03-01

    Upwelling phenomenon along the eastern boundaries of global ocean has received greater attention in the recent times due to its environmental and economic significance in the global warming and the scenario of changing climate as opined by IPCC AR5. In this context, the availabile satellite data on sea surface winds, sea surface temperature (SST), sea level anomaly (SLA) and chlorophyll-a concentration (Chl-a), for the period 1981-2016 were analyzed to identify the coastal upwelling pattern in the Southeastern Arabian Sea (SEAS). Synergistic approach, using winds, SST, SLA and Chl-a revealed that strong upwelling was prevailing between 8°N and 12°N. During the study period, geographical differences existed in the peak values of upwelling favorable conditions considered for study. Analysis of the alongshore winds which are conducive for upwelling were observed to be curtailed towards the northern part of the study region between 2005 and 2010. Also, the strength of upwelling reduced during the strong ENSO years of 1997 and 2015. Linear regression based trend analysis of upwelling indices like Ekman transport, SST and chlorophyll along the coast, during the upwelling period, revealed slight increase in the strength towards the southern region while it decreased to the north during the study period.

  19. An upwelling-induced retention area off Senegal: A mechanism to ...

    African Journals Online (AJOL)

    Chlorophyll distribution peaks nearshore. This unique surface structure is interpreted as the result of a “double cell” structure in the upwelling vertical circulation: a first cell located at the shelf break, the main upwelling cell that brings cold and nutrient-rich subsurface water to the surface, and a second cell located inshore of ...

  20. The relationship between Arabian Sea upwelling and Indian Monsoon revisited in a high resolution ocean simulation

    Science.gov (United States)

    Yi, Xing; Hünicke, Birgit; Tim, Nele; Zorita, Eduardo

    2018-01-01

    Studies based on sediment records, sea-surface temperature and wind suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer Monsoon. We examine this relationship directly in an eddy-resolving global ocean simulation STORM driven by atmospheric reanalysis over the last 61 years. With its very high spatial resolution (10 km), STORM allows us to identify characteristics of the upwelling system. We analyse the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analysis reveals high interannual correlations between coastal upwelling and along-shore wind-stress (r = 0.73) as well as with sea-surface temperature (r = -0.83). However, the correlation between the upwelling and the Monsoon is small. We find an atmospheric circulation pattern different from the one that drives the Monsoon as the main modulator of the upwelling variability. In spite of this, the patterns of temperature anomalies that are either linked to Arabian Sea upwelling or to the Monsoon are spatially quite similar, although the physical mechanisms of these links are different. In addition, no long-term trend is detected in our modelled upwelling in the Arabian Sea.

  1. Sardine and anchovy spawning as related to temperature and upwelling in the California current system

    Energy Technology Data Exchange (ETDEWEB)

    Lluch-Belda, D.; Lluch-Cota, D.B.; Hernandez-Vazquez, S.H.; Salinas-Zavala, C.A. (Centro de Investigaciones Biologicas de Baja California Sur, A.C., (Mexico)); Schwartzlose, R.A. (Univ. of California, La Jolla (United States))

    1991-11-01

    Sardine and anchovy spawning was analyzed regarding its relation to sea-surface temperature and upwelling, using CalCOFI cruise data and Bakun's upwelling indices. Previous reports of temperature ranges for sardine and anchovy spawning have not taken into account the distribution of SST and have mostly referenced the cooler spawning area of the species. By obtaining the proportion of positive stations to total sampled stations for each tenth of a degree Celsius in the SST distribution, the authors were able to discriminate the ranges of preferred temperatures of spawning for both species. Sardines spawn in a much wider temperature range (13-25C) than anchovy (11.5-16.5C). Two maxima of spawning occur in the California Current: at 15C and 23C. An additional peak is present in the Gulf of California at about 19C. Only one maximum is evident for anchovy spawning, at about 14C. The distribution of spawning as a function of upwelling was also analyzed for both species. There is a maximum for sardines at intermediate values of upwelling. There are two maxima for anchovy: a minor one at low levels of upwelling and a major one at the maximum values of upwelling. They conclude that sardines are eurythermic as compared to anchovies, but spawn only at intermediate values of upwelling, whereas anchovies are stenothermic but spawn at much wider ranges of upwelling, particularly at low and high values. The differences suggest exclusive competition, but more detailed analyses are needed.

  2. Response of Mytilus edulis to enhanced phytoplankton availibility by controlled upwelling in an oligographic fjord

    NARCIS (Netherlands)

    Strohmeier, T.; Strand, Ø.; Alunno-Bruscia, M.; Duinker, A.; Rosland, R.; Jansen, H.M.

    2015-01-01

    The controlled upwelling of nutrient-rich deep water in oligotrophic coastal regions has been proposed as a means of increasing phytoplankton and, subsequently, bivalve aquaculture production. This was tested as part of a large-scale upwelling experiment in an oligotrophic environment (Lysefjord,

  3. The future of coastal upwelling in the Humboldt current from model projections

    Science.gov (United States)

    Oyarzún, Damián; Brierley, Chris M.

    2018-03-01

    The Humboldt coastal upwelling system in the eastern South Pacific ocean is one of the most productive marine ecosystems in the world. A weakening of the upwelling activity could lead to severe ecological impacts. As coastal upwelling in eastern boundary systems is mainly driven by wind stress, most studies so far have analysed wind patterns change through the 20th and 21st Centuries in order to understand and project the phenomenon under specific forcing scenarios. Mixed results have been reported, and analyses from General Circulation Models have suggested even contradictory trends of wind stress for the Humboldt system. In this study, we analyse the ocean upwelling directly in 13 models contributing to phase 5 of the Coupled Model Intercomparison Project (CMIP5) in both the historical simulations and an extreme climate change scenario (RCP8.5). The upwelling is represented by the upward ocean mass flux, a newly-included variable that represents the vertical water transport. Additionally, wind stress, ocean stratification, Ekman layer depth and thermocline depth were also analysed to explore their interactions with coastal upwelling throughout the period studied. The seasonal cycle of coastal upwelling differs between the Northern and Southern Humboldt areas. At lower latitudes, the upwelling season spans most of the autumn, winter and spring. However, in the Southern Humboldt area the upwelling season takes place in spring and the summertime with downwelling activity in winter. This persists throughout the Historical and RCP8.5 simulations. For both the Northern and Southern Humboldt areas an increasing wind stress is projected. However, different trends of upwelling intensity are observed away from the sea surface. Whereas wind stress will continue controlling the decadal variability of coastal upwelling on the whole ocean column analysed (surface to 300 m depth), an increasing disconnect with upwelling intensity is projected below 100 m depth throughout the 21

  4. Seasonal patterns of wind-induced upwelling/downwelling in the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Andrew Bakun

    2001-09-01

    Full Text Available The historical file of wind observations from maritime weather reports is summarized to identify the characteristic seasonal distributions of wind-induced Ekman upwelling and downwelling in the Mediterranean Sea. Both coastal upwelling/downwelling and wind-stress curl-driven open ocean upwelling/downwelling are treated in a unified description. Vigorous upwelling zones are found in the eastern Aegean Sea, off the west coast of Greece, and in the Gulf of Lyons. The southern coast of the Mediterranean is found to be primarily a downwelling area, although significant coastal upwelling does appear in the Gulf of Sidra during the spring and summer seasons, and along the Algerian coast during summer.

  5. Sources of new nitrogen in the Vietnamese upwelling region of the South China Sea

    DEFF Research Database (Denmark)

    Bombar, Deniz; Dippner, Joachim W.; Doan, Hai Nhu

    2010-01-01

    In the South China Sea, the southwest monsoon between June and September induces upwelling off the southern central Vietnamese coast. During field campaigns in July 2003 and 2004 we evaluated the importance of nitrate and nitrogen fixation as sources of new nitrogen for phytoplankton primary...... productivity, both in the actual upwelling zone and in the oligotrophic area farther offshore. Complementary to rate measurements of primary productivity, nitrate uptake, and nitrogen fixation, we determined vertical nitrate fluxes by Ekman upwelling (upwelling zone) and turbulent diffusion (offshore waters...... productivity, if Redfield stoichiometry is assumed. In July 2003 upwelling fluxes of 14 ± 2 mmol N m-2 d-1 exceeded N demands, indicating that new production was not fully realized. Diffusive nitrate fluxes in offshore waters were determined in July 2003 and are of the order of 2.3 ± 0.6 mmol N m-2 d-1, based...

  6. Regeneration of nitrogen by zooplankton and fish in the Northwest Africa and Peru upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T E

    1976-01-01

    The availability of nutrients and light are the dominant controlling factors of the levels of primary production in the ocean. In the lower latitudes where most coastal upwelling areas are located, the amount of light is seldom below the critical level to inhibit productivity so nutrients are often the limiting factor in phytoplankton growth. Nutrients utilized in primary productivity are derived from two sources in upwelling areas. Nutrients are introduced to the euphotic zone from depth by the physical processes that create upwelling and nutrients are recycled by biological organisms that inhabit the area. Nitrate introduced into the euphotic zone by upwelling supports new productivity while ammonium and other excretory products regenerated by zooplankton and nekton supports regenerated productivity. Results are reported from studies off the coast of Northwest Africa and Peru using /sup 15/N as a tracer that showed that recycled ammonium may fulfill nearly half of the daily nitrogen requirement of phytoplankton and upwelled nitrate may provide the other half.

  7. Nutrient supply, surface currents, and plankton dynamics predict zooplankton hotspots in coastal upwelling systems

    Science.gov (United States)

    Messié, Monique; Chavez, Francisco P.

    2017-09-01

    A simple combination of wind-driven nutrient upwelling, surface currents, and plankton growth/grazing equations generates zooplankton patchiness and hotspots in coastal upwelling regions. Starting with an initial input of nitrate from coastal upwelling, growth and grazing equations evolve phytoplankton and zooplankton over time and space following surface currents. The model simulates the transition from coastal (large phytoplankton, e.g., diatoms) to offshore (picophytoplankton and microzooplankton) communities, and in between generates a large zooplankton maximum. The method was applied to four major upwelling systems (California, Peru, Northwest Africa, and Benguela) using latitudinal estimates of wind-driven nitrate supply and satellite-based surface currents. The resulting zooplankton simulations are patchy in nature; areas of high concentrations coincide with previously documented copepod and krill hotspots. The exercise highlights the importance of the upwelling process and surface currents in shaping plankton communities.

  8. Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses

    Directory of Open Access Journals (Sweden)

    José M. R. Alves

    2013-05-01

    Full Text Available The Regional Ocean Modeling System ocean model is used to simulate the decadal evolution of the regional waters in offshore Iberia in response to atmospheric fields given by ECMWF ERA-40 (1961–2001 and ERA-Interim (1989–2008 reanalyses. The simulated sea surface temperature (SST fields are verified against satellite AVHRR SST, and they are analysed to characterise the variability and trends of coastal upwelling in the region. Opposing trends in upwelling frequency are found at the northern limit, where upwelling has been decreasing in recent decades, and at its southern edge, where there is some evidence of increased upwelling. These results confirm previous observational studies and, more importantly, indicate that observed SST trends are not only due to changes in radiative or atmospheric heat fluxes alone but also due to changes in upwelling dynamics, suggesting that such a process may be relevant in climate change scenarios.

  9. Influence of upwelling on distribution of chaetognath (zooplankton) in the oxygen deficient zone of the eastern Arabian Sea.

    Digital Repository Service at National Institute of Oceanography (India)

    Kusum, K.K.; Vineetha, G.; Raveendran, T.V.; Muraleedharan, K.R.; Biju, A.; Achuthankutty, C.T.

    species. Abundance weight (Aw) value further helped to understand the mode of distribution of the chaetognath community around the upwelling locations. The variation in the depth-weighted average values of different species between the upwelling and non...

  10. Dynamics of a "low-enrichment high-retention" upwelling center over the southern Senegal shelf

    Science.gov (United States)

    Ndoye, Siny; Capet, Xavier; Estrade, Philippe; Sow, Bamol; Machu, Eric; Brochier, Timothée.; Döring, Julian; Brehmer, Patrice

    2017-05-01

    Senegal is the southern tip of the Canary upwelling system. Its coastal ocean hosts an upwelling center which shapes sea surface temperatures between latitudes 12° and 15°N. Near this latter latitude, the Cape Verde headland and a sudden change in shelf cross-shore profile are major sources of heterogeneity in the southern Senegal upwelling sector (SSUS). SSUS dynamics is investigated by means of Regional Ocean Modeling System simulations. Configuration realism and resolution (Δx≈ 2 km) are sufficient to reproduce the SSUS frontal system. Our main focus is on the 3-D upwelling circulation which turns out to be profoundly different from 2-D theory: cold water injection onto the shelf and upwelling are strongly concentrated within a few tens of kilometers south of Cape Verde and largely arise from flow divergence in the alongshore direction; a significant fraction of the upwelled waters are retained nearshore over long distances while travelling southward under the influence of northerly winds. Another source of complexity, regional-scale alongshore pressure gradients, also contributes to the overall retention of upwelled waters over the shelf. Varying the degree of realism of atmospheric and oceanic forcings does not appreciably change these conclusions. This study sheds light on the dynamics and circulation underlying the recurrent sea surface temperature pattern observed during the upwelling season and offers new perspectives on the connections between the SSUS physical environment and its ecosystems. It also casts doubt on the validity of upwelling intensity estimations based on simple Ekman upwelling indices at such local scales.

  11. Hot upwelling conduit beneath the Atlas Mountains, Morocco

    Science.gov (United States)

    Sun, Daoyuan; Miller, Meghan S.; Holt, Adam F.; Becker, Thorsten W.

    2014-11-01

    The Atlas Mountains of Morocco display high topography, no deep crustal root, and regions of localized Cenozoic alkaline volcanism. Previous seismic imaging and geophysical studies have implied a hot mantle upwelling as the source of the volcanism and high elevation. However, the existence, shape, and physical properties of an associated mantle anomaly are debated. Here we use seismic waveform analysis from a broadband deployment and geodynamic modeling to define the physical properties and morphology of the anomaly. The imaged low-velocity structure extends to ~200 km beneath the Atlas and appears ~350 K hotter than the ambient mantle with possible partial melting. It includes a lateral conduit, which suggests that the Quaternary volcanism arises from the upper mantle. Moreover, the shape and temperature of the imaged anomaly indicate that the unusually high topography of the Atlas Mountains is due to active mantle support.

  12. Artificial upwelling using offshore wind energy for mariculture applications

    Directory of Open Access Journals (Sweden)

    Álvaro Viúdez

    2016-09-01

    Full Text Available Offshore wind is proposed as an energy source to upwell nutrient-rich deep water to the ocean photic layers. A spar-buoy wind turbine with a rigid tube about 300 m long is proposed as a pipe to drive deep water up to the surface. The minimum energy required to uplift the water is the potential energy difference between surface waters inside and outside the pipe, which depends on the background density profile. The corresponding surface jump or hydraulic head, h, calculated for several analytical and experimental density profiles, is of the order of 10 cm. If the complete turbine power (of the order of several MW is used for raising the water (assuming a 100% pump efficiency, in a frictionless flow, very large water volumes, of the order of thousands of m3 s-1, will be transported to the photic layers. In a more realistic case, taking into account pipe friction in wide pipes, of the order of 10 m radius, and a power delivered to the fluid of 1 MW, the volume transport is still very large, about 500 m3 s-1. However, such a large amount of dense water could sink fast to aphotic layers due to vertical static instability (the fountain effect, ruining the enhancement of primary production. Hence, some ways to increase the turbulent entrainment and avoid the fountain effect are proposed. From the energetic viewpoint, artificial upwelling using offshore wind energy is a promising way to fertilize large open sea regions. This mariculture application is, however, severely subjected to atmosphere and ocean climatology, as well as to ecological dynamics. The general problem is multidisciplinary, and some important physical, engineering and ecological questions need to be seriously addressed to improve our confidence in the approach presented here.

  13. Using CAM3 and the Alkenone Method to Understand how Pliocene SST's Affect California and Other Climates Adjacent to Upwelling Regions

    Science.gov (United States)

    Searles, Z. A.; Otto-Bliesner, B. L.; Rosenbloom, N. A.; Dekens, P. S.

    2008-12-01

    The Intergovernmental Panel on Climate Change fourth assessment report established with 90% confidence that anthropogenic climate change will result in a warmer world. In order to more fully understand possible future climate, past analogues of warm periods should be analyzed. The early Pliocene is an appropriate analogue because the continental configuration was similar to today and CO2 levels were comparable to present (~100ppm higher than pre-anthropogenic levels). This project has two objectives: 1.To test the atmospheric sensitivity to USGS PRISM2 dataset revised to better approximate proxy data indicating warmer SST's in upwelling regions and 2. To provide early-Pliocene (2.7- 3.5 Ma) SST estimates for ODP site 1018 on the California Margin (36°59.4'N, 123°16.5'W) using the UK'37 SST proxy. Recent UK'37 proxy data reveals that PRISM2 underestimates SST's in Pacific and Atlantic coastal upwelling regions. The sensitivity of the atmosphere to significantly warmer SST's in upwelling regions was tested using the National Center for Atmospheric Research (NCAR) Community Atmospheric Model, version 3 (CAM3). Initial conditions were supplied by the USGS PRISM2 project and include Pliocene SST's, vegetation cover, sea level height, topography, marine and continental ice extent. Pliocene SST's along the Californian, Peruvian, North African and South African margin were modified to reflect proxy observations from 4 sites. The lack of observational coverage (1 data point per region) required interpolation of the areal extent of the SST warming anomaly indicated by the proxies. Experiment results show increased cumulative precipitation and humidity in regions where the original PRISM2 predicted drying. The predicted North American increase in precipitation is in better agreement with geologic proxies indicating wetter conditions. Warmer SST's also causes weaker wind velocities along the North American, Peruvian, and North African margins, and stronger winds along the

  14. Micro- and Mesozooplankton Distribution Related to an Upwelling Filament in the Northern Benguela Current Region

    Science.gov (United States)

    Koppelmann, R.; Bohata, K.

    2016-02-01

    Upwelling filaments are formations of cold upwelled water which develop near the coast and extend up to hundreds of kilometers offshore. They are important for the dynamics of upwelling systems as they transport nutrients and plankton to the open ocean. On regional scales, the transport of water masses by upwelling filaments occasionally can be higher and more important than the Ekman transport. Such filaments are able to transport a large fraction of coastal primary production even during low upwelling intensity. However, the dimension and nature of transported organic matter depends largely on the size structure of the involved plankton community. In the course of the GENUS project (Geochemistry and Ecology of the Namibian Upwelling System), we investigated the micro- and mesozooplankton community associated with upwelling filaments. Small-scale differences in the distribution of micro- and mesozooplankton species were detected and related to different water masses. Depending on the developmental stage of the filament, zooplankton abundance can be higher or lower than in the surrounding offshore waters. Along the filament, the microzooplankton composition changed from ciliates-dominated in the in the centre of the filament to dinoflagellate-dominated further offshore. Several mechanisms like the exhaustion of available nutrients and the subsequent die off and sinking of the community or increased predation pressure within the filament are discussed to enlighten the fate of the transported organic material.

  15. Sources of short-lived bromocarbons in the Iberian upwelling system

    Directory of Open Access Journals (Sweden)

    S. Raimund

    2011-06-01

    Full Text Available Seawater concentrations of the four brominated trace gases, dibromomethane (CH2Br2, bromodichloromethane (CHBrCl2, dibromochloromethane (CHBr2Cl and bromoform (CHBr3 were measured at different depths of the water column in the Iberian upwelling off Portugal during summer 2007. Statistical analysis of the data set revealed three distinct clusters, caused by different sea surface temperature. Bromocarbon concentrations were elevated in recently upwelled and aged upwelled waters (mean values of 30 pmol l−1 for CHBr3, while concentrations in the open ocean were significantly lower (7.4 pmol l−1 for CHBr3. Comparison with other productive marine areas revealed that the Iberian upwelling had higher halocarbon concentrations than the Mauritanian upwelling. However, the concentrations off the Iberian Peninsula were still much lower than those of coastal macroalgal-influenced waters or those of Polar regions dominated by cold water adapted diatoms. Correlations with biological variables and marker pigments indicated that phytoplankton was a source of bromocarbon in the open ocean. By contrast, in upwelled water masses along the coast, halocarbons showed weaker correlations to marker pigments but were significantly influenced by the tidal frequency. Our results indicate a strong intertidal coastal source of bromocarbon and transport by surface currents of these enriched waters towards the upwelling region.

  16. Physical structure and algae community of summer upwelling off eastern Hainan

    Science.gov (United States)

    Xu, H.; Liu, S.; Xie, Q.; Hong, B.; Long, T.

    2017-12-01

    The upwelling system is the most productive ecosystem along the continental shelf of the northern South China Sea Shelf. It brings nutrient from bottom to surface and blooms biotic community driven by summer monsoon. In this study, we present observed results of physical and biotic community structures during August, 2015 in the upwelling system along Hainan eastern coast, which is one the strongest upwelling systems in the northern South China Sea. By using hydrological data collected by CTD, we found a significant cold water tongue with high salinity which extended from offshore to 100 m isobaths. However, dissolved oxygen (DO) showed a sandwich structure in which high core of DO concentration appeared at the layer from 5 m to 30 m. It possibly was caused by the advection transport of high DO from adjacent area. Basically, this upwelling system was constrained at northern area of 18.8ºN in horizontal due to the weakening summer monsoon in August. In addition, we collected water sample at the upwelling area and measured algae categories and concentration by high performance liquid chromatography (HPLC). Results show the biotic community was dominated by five types of algae mainly, they were diatoms, dinoflagellates, green algae, prokaryotes and prochlorococcus. And different patterns of different algae were demonstrated. In the upwelling area, diatoms and prokaryotes show opposite structures, and more complex pattern for the rest three algae indicating an active biotic community in the upwelling system.

  17. A Holocene record of ocean productivity and upwelling from the northern California continental slope

    Science.gov (United States)

    Addison, Jason A.; Barron, John A.; Finney, Bruce P.; Kusler, Jennifer E.; Bukry, David; Heusser, Linda E.; Alexander, Clark R.

    2018-01-01

    The Holocene upwelling history of the northern California continental slope is examined using the high-resolution record of TN062-O550 (40.9°N, 124.6°W, 550 m water depth). This 7-m-long marine sediment core spans the last ∼7500 years, and we use it to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with Holocene millennial-scale warm intervals. A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ13C and bulk sedimentary δ15N), and key microfossil indicators of upwelling were used to test this hypothesis. The record of biogenic accumulation in TN062-O550 shows considerable Holocene variability despite being located within 50 km of the mouth of the Eel River, which is one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at ∼2900 calibrated years before present (cal yr BP) indicates the onset of modern upwelling in the CCS, and this period also corresponds to the most intense period of upwelling in the last 7500 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification at TN062-O550 corresponds closely to that seen at nearby ODP Site 1019, as well as in the Santa Barbara Basin of southern California. Other CCS records with less refined age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we suggest that CCS warming may be conducive to upwelling intensification, though future changes are unclear as the mechanisms forcing SST variability may differ.

  18. A Holocene record of ocean productivity and upwelling from the northern California continental slope

    Science.gov (United States)

    Addison, J. A.; Barron, J. A.; Finney, B.; Kusler, J. E.; Bukry, D.; Heusser, L. E.; Alexander, C. R., Jr.

    2016-12-01

    The Holocene upwelling history of the northern California continental slope is examined using a 7-m-long marine sediment core (TN062-O550; 40.9°N, 124.6°W, 550 m water depth) collected offshore from Eureka, CA, that spans the last 7,400 calibrated years before present (cal yrs BP). A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ13C and bulk sedimentary δ15N), and key microfossil indicators of upwelling were used to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with global Holocene millennial-scale warm intervals. Results show biogenic sediment accumulation in TN062-O550 varied considerably during the Holocene, despite being located within 50 km of the mouth of the Eel River, one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at 2900 cal yr BP indicates the onset of modern upwelling in the CCS, and that this period also corresponds to the most intense period of upwelling in the last 7,400 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification as recorded in TN062-O550 corresponds closely to that seen at nearby ODP Site 1019 as well as in the Santa Barbara Basin of southern California. Other CCS records with less high-quality age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone-derived sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we tentatively suggest that regional CCS warming may be conducive to upwelling intensification in the future.

  19. Corona Formation and Heat Loss on Venus by Coupled Upwelling and Delamination

    Science.gov (United States)

    Smrekar, Suzanne E.; Stofan, Ellen R.

    1997-01-01

    Coronae are volcanotectonic features that are unique to Venus and are interpreted to be small-scale upwellings. A model in which upwelling causes delamination at the edge of the plume head, along with deformation of a pre-existing depleted mantel Layer, can produce the full range of topographic forms of coronae. If half of the coronae are active, delamination of the lower lithosphere could account for about 10% of venus's heat loss, with another 15% due to upwelling. Delamination may occur in other geologic enviroment and could help account for 'Venus' heat loss 'deficit'.

  20. Biological and oceanographic upwelling indicators at Cabo Frio (RJ

    Directory of Open Access Journals (Sweden)

    Gleyci A. O. Moser

    1997-01-01

    Full Text Available Phytoplankton biomass, chemical parameters and hydrology were studied in a transect 101.6 km long off Cabo Frio (RJ, Southeast Brazil, during summer (December 29 to 31, 1991 and winter (June 27 to 30, 1992. Wind induced upwelling events are frequently observed in the area during summer, becoming rare during winter. By the summer cruise a bloom of phytoplankton was observed in surface, close to the coast, with chlorophyll concentrations reaching 25.55 mg Chl-a m-3, uncoupled from the cold, nutrient rich waters of South Atlantic Central Water (SACW, found below 40 m depth. During the winter cruise, the SACW raised at the surface waters in front of Cabo Frio depicting an upwelling event. However, in spite of high surface nitrate concentrations (up to 7.7 f.1M chlorophyll-a were lower than 2 mg Chl-a m-3. The phytoplankton biomass, meteorological and hydrological data suggest a probable upwelling event immediately before the summer cruise, and an ongoing one during winter time. Cluster analyses and principal component analyses (PCA were applied to summer and winter data, pointing out multidimensional fronts in the area during both seasons.A biomassa fitoplanctônica, parâmetros químicos e hidrologia foram estudadas em um transecto de 101,6 Km ao largo de Cabo Frio, (RJ Brasil, durante o verão (Dezembro 29 a 31, 1991 e inverno (Junho 27 a 30, 1992. Nesta área, eventos de ressurgência induzidos pelo vento são comuns durante o verão, tornando-se mais raros durante o inverno. Durante o período de verão uma floração de fitoplâncton foi observada na superfície próximo ao continente, apresentando um máximo de clorofila-a igual a 25,55 mg Cl-a m'3 desacoplado das águas frias e ricas em nutrientes da Água Central do Atlântico Sul (ACAS, presente abaixo de 40 m. Durante o inverno, a ACAS alcançou a superflcie em frente a Cabo Frio, caracterizando um evento de ressurgência. Entretanto, apesar das altas concentrações de nitrato na superf

  1. Artificial upwelling using the energy of surface waves

    Science.gov (United States)

    Soloviev, A.

    2016-02-01

    The ocean is an important component of climate and climate change, since the heat capacity of a few meters of the upper ocean is equivalent to the heat capacity of the entire atmosphere. (Solar radiation and IR balance in the atmosphere are of course major factors as well.) Artificial upwelling devices using the energy of surface waves, similar to those developed by Vershinskiy, Pshenichnyy, and Soloviev (1987), can bring cold water from below the thermocline to the sea surface. Their wave-inertia pump consisted of a vertical tube, a valve, and a buoy to keep the device afloat. The device operated by using energy of surface waves to create an upward flow of water in the tube. An outlet valve at the top of the unit synchronized the operation of the device with surface waves and prevented back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. This type of artificial upwelling can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from the deep layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps has been estimated for different environmental conditions using a computational fluid dynamics model. The cooled near-surface layer of the ocean will be getting more heat from the sun, which is a detrimental consequence. Cloud seeding can help to mitigate this extra warming. A synergistic approach to climate engineering can thus reduce detriments and increase potential benefits of this system to society.

  2. Diagenetic behavior of barite in a coastal upwelling setting

    Science.gov (United States)

    Hendy, I. L.

    2010-12-01

    Multiproxy data from ODP Hole 1017E (Point Conception, California) provide an excellent opportunity to examine the behavior of barium, within a well-characterized sedimentary system. Bariumexcess is generally considered to be a productivity proxy; however, in nearshore environments, Baexcess records can be compromised by both sediment provenance and barite remobilization. For the last 60 kyr, ODP Hole 1017E exhibits significant changes both in primary productivity driven by coastal upwelling and in the sediment redox chemistry of underlying sediments. Significant barite enrichment occurs at an active diagenetic front that marks the boundary between sulfate-rich and sulfate-poor pore waters. This boundary also intersects a sediment facies change from deposition of relatively coarse-grained sediment before 35 ka to an interval of fine-grained, organic-rich sediment after (i.e., Interstadial Event 8). Changes in diffusion rates associated with the sediment facies change cause a strong but misleading correlation between a mobile zone of barite enrichment and rapid climate change. Thus, within the Baexcess record at ODP Hole 1017E is a history of redox chemistry that has corrupted the paleoproductivity record of Babiogenic.

  3. Ten Years of Hydrographic Variability Off Central California During the Upwelling Season

    National Research Council Canada - National Science Library

    Baltz, Kenneth

    1997-01-01

    Analysis of mean conditions and variability during the upwelling season off central California was performed on data sets of buoy and shoreline surface measurements and CTD data from ten annual NMFS surveys (1987-1996...

  4. Observational evidence of upwelling off the southwest coast of India during June-July 2006

    Digital Repository Service at National Institute of Oceanography (India)

    Lekshmi, S.; Smitha, B.R.; Revichandran, C.

    Considerable latitudinal variability exists in the forcing mechanisms and intensity of coastal upwelling along the southwest coast of India. Present work is based on the insitu observations conducted onboard FORV Sagar Sampada for 12 days along two...

  5. Ekman Upwelling, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  6. Upwelling and associated hydrography along the west coast of india during southwest monsoon, 1999

    Digital Repository Service at National Institute of Oceanography (India)

    Maheswaran, P.A.; Rajesh, G.; Revichandran, C.; Nair, K.K.C.

    ) and 1.2 degrees C (off Mangalore) from the farthest stations, indicating the presence of upwelled water near the coast. Well defined thermal, saline and density fronts were visible. Relatively high offshore transport was observed off Kanyakumari...

  7. Upwelling along the western Indian continental margin and its geological record - a summary

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    sediment components can be correlated to the characteristics of the water masses and, thereby, to the intensity and magnitude of upwelling. Benthic and planktonic foraminifers are particularly useful indicators; e.g., the invasion of immigrant populations...

  8. Observed anomalous upwelling in the Lakshadweep Sea during the summer monsoon season of 2005

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Rao, R.R.; Nisha, K.; GirishKumar, M.S.; Pankajakshan, T.; Ravichandran, M.; Johnson, Z.; Girish, K.; Aneeshkumar, N.; Srinath, M.; Rajesh, S.; Rajan, C.K.

    of local and remote forcings are examined to explain the observed anomalous upwelling during SMS of 2005. The equatorward alongshore wind stress (WS) along the KK XBT transect persisted in a transient manner beyond September only during SMS of 2005...

  9. Ekman Upwelling, METOP ASCAT, 0.25 degrees, Global, Near Real Time

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  10. Climate change. Climate change and wind intensification in coastal upwelling ecosystems.

    Science.gov (United States)

    Sydeman, W J; García-Reyes, M; Schoeman, D S; Rykaczewski, R R; Thompson, S A; Black, B A; Bograd, S J

    2014-07-04

    In 1990, Andrew Bakun proposed that increasing greenhouse gas concentrations would force intensification of upwelling-favorable winds in eastern boundary current systems that contribute substantial services to society. Because there is considerable disagreement about whether contemporary wind trends support Bakun's hypothesis, we performed a meta-analysis of the literature on upwelling-favorable wind intensification. The preponderance of published analyses suggests that winds have intensified in the California, Benguela, and Humboldt upwelling systems and weakened in the Iberian system over time scales ranging up to 60 years; wind change is equivocal in the Canary system. Stronger intensification signals are observed at higher latitudes, consistent with the warming pattern associated with climate change. Overall, reported changes in coastal winds, although subtle and spatially variable, support Bakun's hypothesis of upwelling intensification in eastern boundary current systems. Copyright © 2014, American Association for the Advancement of Science.

  11. Discriminating the biophysical impacts of coastal upwelling and mud banks along the southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Karnan, C.; Jyothibabu, R.; Arunpandi, N.; Jagadeesan, L.; Muraleedharan, K.R.; Pratihary, A.K.; Balachandran, K.K.; Naqvi, S.W.A.

    Coastal upwelling and mud banks are two oceanographic processes concurrently operating along certain stretches of the southwest (Kerala) coast of India during the Southwest Monsoon period (June-September), facilitating significant enhancement...

  12. A Heated Debate: Evidence for Two Thermal Upwellings in East Africa

    Science.gov (United States)

    Rooney, T.; Herzberg, C.; Bastow, I.

    2008-12-01

    East African Cenozoic magmatism records the thermal influence of one or more long-lived mantle plumes. We present primary magma compositions, mantle potential temperatures (Tp), and mantle melt fractions using PRIMELT2 in order to examine the geographic and historical distribution of upper mantle thermal anomalies in East Africa. Regional magmatism can be divided into an early flood basalt phase in Ethiopia/Yemen (~30 Ma), a longer-lived episode of basaltic magmatism in Kenya and Southern Ethiopia (~45 to 23 Ma), and a more recent phase (~23 Ma to Present) that is coincidental with the development of the East African Rift (EAR). We have carefully selected a total of 54 samples from these time periods, excluding erroneous results derived from lavas with evidence of clinopyroxene fractionation or volatile rich and pyroxenitic sources. Our results show that elevated Tp in the Ethiopian/Yemen flood basalt province (Tp max =1520°C) and in the early Kenya/S. Ethiopia magmatism (Tp max = 1510°C) are virtually identical. Our results indicate that the existing geochemical division between high and low Ti Ethiopia/Yemen flood basalts has a thermal basis: low-Ti lavas are hotter than the high-Ti lavas. Magmatism in the region subsequent to 23 Ma exhibits only minor cooling (Tp max = 1490°C), though more substantial cooling is observed in Turkana, Kenya (60°C) and Yemen (80°C). Rift lavas from Ethiopia exhibit a clear decrease in Tp away from Afar southwestward along the EAR before progressively rising again in Southern Ethiopia towards Turkana. South of Turkana, elevated Tp is observed in the western and eastern branches of the EAR surrounding the Tanzania Craton. The modern spatial distribution of Tp in EAR magmatism indicate two distinct heat sources, one in Afar and another under the Tanzania craton. We suggest that hot mantle plume material from Afar and Turkana (which may or may not merge at depth) is channeled beneath the thinned rift lithosphere and provides a

  13. Practical limitations on the use of diurnal temperature signals to quantify groundwater upwelling

    Science.gov (United States)

    Briggs, Martin A.; Lautz, Laura K.; Buckley, Sean F.; Lane, John W.

    2014-01-01

    Groundwater upwelling to streams creates unique habitat by influencing stream water quality and temperature; upwelling zones also serve as vectors for contamination when groundwater is degraded. Temperature time series data acquired along vertical profiles in the streambed have been applied to simple analytical models to determine rates of vertical fluid flux. These models are based on the downward propagation characteristics (amplitude attenuation and phase-lag) of the surface diurnal signal. Despite the popularity of these models, there are few published characterizations of moderate-to-strong upwelling. We attribute this limitation to the thermodynamics of upwelling, under which the downward conductive signal transport from the streambed interface occurs opposite the upward advective fluid flux. Governing equations describing the advection–diffusion of heat within the streambed predict that under upwelling conditions, signal amplitude attenuation will increase, but, counterintuitively, phase-lag will decrease. Therefore the extinction (measurable) depth of the diurnal signal is very shallow, but phase lag is also short, yielding low signal to noise ratio and poor model sensitivity. Conversely, amplitude attenuation over similar sensor spacing is strong, yielding greater potential model sensitivity. Here we present streambed thermal time series over a range of moderate to strong upwelling sites in the Quashnet River, Cape Cod, Massachusetts. The predicted inverse relationship between phase-lag and rate of upwelling was observed in the field data over a range of conditions, but the observed phase-lags were consistently shorter than predicted. Analytical solutions for fluid flux based on signal amplitude attenuation return results consistent with numerical models and physical seepage meters, but the phase-lag analytical model results are generally unreasonable. Through numerical modeling we explore reasons why phase-lag may have been over-predicted by the

  14. Kinematic models for the opening of the South China Sea: An upwelling divergent flow origin

    Science.gov (United States)

    Chen, Lin; Hu, Jiwei; Yang, Dinghui; Song, Haibin; Wang, Zhenhua

    2017-06-01

    We investigate the kinematics of continent breakup and seafloor spreading in response to the upwelling divergent mantle flow using the optimal nearly-analytical discrete method. Modeling results show that a larger upwelling rate (Vz) in the upwelling divergent flow system favors the earlier development of continent breakup and seafloor spreading and the formation of narrow continental rifted margins and mantle exhumation; while a larger half divergent rate (Vx) favors the diffusive lithospheric thinning and the formation of wide continental rifted margins and mantle exhumation. The upwelling divergent flow-driven continent extension is strongly depth-dependent at the proximal margins, but it behaves approximately in a depth-uniform manner at the distal margins. Application of this model to the South China Sea (SCS) demonstrates that: (1) an upwelling flow operation with Vz = 0.3 cm/yr can explain the pre-spreading continent extension of the SCS between ca. 65 Ma and ca. 33 Ma; (2) the followed upwelling divergent flow with Vx = 2.5 cm/yr and Vz = 0.3 cm/yr can reproduce the seafloor spreading history at ca. 33-16 Ma in the SCS central oceanic basin; and (3) the post-16 Ma thermal cooling since the cessation of the SCS seafloor spreading contributed ∼1.2 km to the present-day bathymetry at the relict spreading ridge. The upwelling divergent flow with a high ratio of Vx/Vz was also likely responsible for the occurrence of the very wide rifted continental margins bounded the SCS. We suggest that an upwelling divergent mantle flow played a leading role in the opening of the SCS.

  15. A long history of equatorial deep-water upwelling in the Pacific Ocean

    Science.gov (United States)

    Zhang, Yi Ge; Pagani, Mark; Henderiks, Jorijntje; Ren, Haojia

    2017-06-01

    Cold, nutrient- and CO2-rich waters upwelling in the eastern equatorial Pacific (EEP) give rise to the Pacific cold tongue. Quasi-periodic subsidence of the thermocline and attenuation in wind strength expressed by El Niño conditions decrease upwelling rates, increase surface-water temperatures in the EEP, and lead to changes in regional climates both near and far from the equatorial Pacific. EEP surface waters have elevated CO2 concentrations during neutral (upwelling) or La Niña (strong upwelling) conditions. In contrast, approximate air-sea CO2 equilibrium characterizes El Niño events. One hypothesis proposes that changes in physical oceanography led to the establishment of a deep tropical thermocline and expanded mixed-layer prior to 3 million years ago. These effects are argued to have substantially reduced deep-water upwelling rates in the EEP and promoted a "permanent El Niño-like" climate state. For this study, we test this supposition by reconstructing EEP "excess CO2" and upwelling history for the past 6.5 million years using the alkenone-pCO2 methodology. Contrary to previous assertions, our results indicate that average temporal conditions in the EEP over the past ∼6.5 million years were characterized by substantial CO2 disequilibrium and high nutrient delivery to surface waters - characteristics that imply strong upwelling of deep waters. Upwelling appears most vigorous between ∼6.5 to 4.5 million years ago coinciding with high accumulation rates of biogenic material during the late Miocene - early Pliocene "biogenic bloom".

  16. A Fortran-77 program for Monte Carlo simulation of upwelling light from the sea

    Digital Repository Service at National Institute of Oceanography (India)

    Sathe, P.V.; Sathyendranath, S.

    the sea surface and at its bottom. Besides, the program simulates the angular composition of upwelling light for individual spectral channels, as well as its spectral composition for each angular interval. The physical conditions of radiative transfer... the sea under given physical conditions can be computed from the inherent optical properties of the seawater. Remote sensing in the visible channels, on the other hand, involves measurement of this upwelling light from the sea and its interpretation...

  17. Spatial distribution of upwelling off the central east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.V.N.

    ), Stommel and Wooster (1965), Panikkar and Jayaraman (1966) and Hsueh and Coastal upwelling along the east coast of India has received considerable attention over the past three decades both in theoretical and observational studies (LaFond, 1954, 1957... coast has been reported by LaFond (1954). The lowering of sea surface tempera- ture in August along the east coast prompted LaFond (1958) to infer the possibility of a secondary period of upwelling. A theoretical study by Varadachari (1961) indicates...

  18. Pathways of upwelling deep waters to the surface of the Southern Ocean

    Science.gov (United States)

    Tamsitt, Veronica; Drake, Henri; Morrison, Adele; Talley, Lynne; Dufour, Carolina; Gray, Alison; Griffies, Stephen; Mazloff, Matthew; Sarmiento, Jorge; Wang, Jinbo; Weijer, Wilbert

    2017-04-01

    Upwelling of Atlantic, Indian and Pacific deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of anthropogenic carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. Here we go beyond the two-dimensional view of Southern Ocean upwelling, to show detailed Southern Ocean upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution ocean and climate models. The northern deep waters enter the Antarctic Circumpolar Current (ACC) via narrow southward currents along the boundaries of the three ocean basins, before spiraling southeastward and upward through the ACC. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the southern ACC boundary, with a spatially nonuniform distribution, regionalizing warm water supply to Antarctic ice shelves and the delivery of nutrient and carbon-rich water to the sea surface. The timescale for half of the deep water to upwell from 30°S to the mixed layer is on the order of 60-90 years, which has important implications for the timescale for signals to propagate through the deep ocean. In addition, we quantify the diabatic transformation along particle trajectories, to identify where diabatic processes are important along the upwelling pathways.

  19. Spatio-Temporal Variability in Coastal Upwelling/Downwelling from Scatterometer Winds

    Science.gov (United States)

    Morey, S. L.

    2014-12-01

    The decade-plus near-continuous record from satellite scatterometers provides indirect measurements of vector winds over the global ocean with sampling largely determined by the satellite orbits. This allows investigation of wind-driven ocean processes even at remote locations that are poorly sampled by in situ measurements. Global satellite wind products are used to produce a database of time series of upwelling indices, similar to those typically produced using data from coastal ocean observing systems, at all coastal locations over the Earth. This database is analyzed to study spatial and temporal variability of coastal upwelling and downwelling throughout the world ocean. The upwelling index is typically a proxy for upwelling/downwelling across the slope assuming a simple local mass balance to the offshore surface Ekman transport. However, along-shore variations in winds and shelf geometry perturb this simple local balance via shelf wave dynamics. In particular, cross-slope velocities downcoast (in a shelf wave propagation sense) of changes in the topographic gradient orientation may respond preferentially to a wind direction not oriented along local isobaths. Data from numerical models are analyzed to illustrate this point and to clarify the relation between upwelling/downwelling and local wind direction throughout the global coastal ocean that may allow improvement in wind-derived upwelling indices.

  20. Variability and Dynamics of the Yucatan Upwelling: High-Resolution Simulations

    Science.gov (United States)

    Jouanno, J.; Pallàs-Sanz, E.; Sheinbaum, J.

    2018-02-01

    The Yucatan shelf in the southern Gulf of Mexico is under the influence of an upwelling that uplifts cool and nutrient rich waters over the continental shelf. The analysis of a set of high-resolution (Δx = Δy ≈ 2.8 km) simulations of the Gulf of Mexico shows two dominant modes of variability of the Yucatan upwelling system: (1) a low-frequency mode related to variations in position and intensity of the Loop Current along the shelf, with upwelling intensified when the Loop Current is strong and approaches to the Yucatan shelf break and (2) a high-frequency mode with peak frequency in the 6-10 days band related to wind-forced coastal waves that force vertical velocities along the eastern Yucatan shelf break. To first order, the strength and position of the Loop Current are found to control the intensity of the upwelling, but we show that high-frequency winds also contribute (˜17%) to a net input of cool waters (<22.5°C) on the Yucatan shelf. Finally, although more observational studies are needed to corroborate the topographic character of the Yucatan upwelling system, this study reveals the key role played by a notch along the Yucatan shelf break: a sensitivity simulation without the notch shows a 55% reduction of the upwelling.

  1. Trends of the Galician upwelling in the context of climate change

    Science.gov (United States)

    Casabella, N.; Lorenzo, M. N.; Taboada, J. J.

    2014-10-01

    Coastal upwelling is a phenomenon of great importance both for the study of ocean dynamics and for the development of fish production in some coastal regions. Our study region, the Galician coast, lies at the northern end of the Canary-Iberian Peninsula upwelling system. Knowing the changes provoked by climate change on this upwelling system is particularly relevant for the future of this area taking into account the social and economic importance of fishing activities in this region. In this paper we study the trends in the intensity and frequency of upwelling in the Galician coast and the expected changes in this phenomenon for the next decades using three regional models implemented within the European project ENSEMBLES. As a main result, we observe that the models show a positive trend in both the intensity and frequency of upwelling phenomenon for the future, particularly significant in spring and summer which are the seasons favorable for upwelling. In autumn and winter there are no significant changes.

  2. Coastal upwelling ecosystems are often identified as regions ...

    African Journals Online (AJOL)

    spamer

    (Chile and Peru), Californian (California and Oregon) and Canary (North-West African – Iberian Peninsula). The Benguela is unique in that its southern boundary is demarcated by the retroflection of a major western boundary current system, the Agulhas Current. On occa- sions Agulhas Current water may intrude into the.

  3. In upwelling regions in which anchovy Engraulis spp. and sardine ...

    African Journals Online (AJOL)

    spamer

    similarities between South African anchovy and sardine, based on the influence of advection of eggs and larvae from different spawning areas. The study attempts to compare the role of passive transport in the survival of young stages of anchovy and sardine. COMPARISON OF SARDINE AND ANCHOVY. LIFE HISTORIES.

  4. NW Iberia Shelf Dynamics. Study of the Douro River Plume.

    Directory of Open Access Journals (Sweden)

    Isabel Iglesias

    2014-06-01

    Full Text Available River plumes are one of the most important mechanisms that transport the terrestrial materials to the coast and the ocean. Some examples of those materials are pollutants, essential nutrients, which enhance the phytoplankton productivity or sediments, which settle on the seabed producing modifications on the bathymetry affecting the navigation channels. The mixing between the riverine and the oceanic waters can induce instabilities, which might generate bulges, filaments, and buoyant currents over the continental shelf. Offshore, the buoyant riverine water could form a front with the oceanic waters often related with the occurrence of current-jets, eddies and strong mixing. The study and modelling of the river plumes is a key factor for the complete understanding of sediment transport mechanisms and patterns, and of coastal physics and dynamic processes. On this study the Douro River plume will be simulated. The Douro River is located on the north-west Iberian coast and its daily averaged freshwater discharge can range values from 0 to 13000 m3/s. This variability impacts the formation of the river plumes and its dispersion along the continental shelf. This study builds on the long-term objective of generate a Douro River plume forecasting system as part of the RAIA and RAIA.co projects. Satellite imagery was analyzed showing that the river Douro is one of the main sources of suspended particles, dissolved material and chlorophyll in the NW Iberian Shelf. The Regional Oceanic Modeling System (ROMS model was selected to reproduce scenarios of plume generation, retention and dispersion. Whit this model, three types of simulations were performed: (i schematic winds simulations with prescribed river flow, wind speed and direction; (ii multi-year climatological simulation, with river flow and temperature change for each month; (iii extreme case simulation, based on the Entre-os-Rios accident situation. The schematic wind case-studies suggest that the

  5. Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

    Energy Technology Data Exchange (ETDEWEB)

    Pease, Leonard F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bamberger, Judith A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Minette, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-08-01

    This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from pulse jet mixers (PJMs) has been analyzed in some detail, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell breakthrough? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g., six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored. The central upwell must satisfy several criteria to be considered a free jet. First, it must travel for several diameters in a nearly constant direction. Second, its velocity must decay with the inverse of elevation. Third, it should have an approximately Gaussian profile. Fourth, the influence of surface or body forces must be negligible. A combination of historical data in a 12.75 ft test vessel, newly analyzed data from the 8 ft test vessel, and conservation of momentum arguments derived specifically for PJM operating conditions demonstrate that the central upwell satisfies these criteria where vigorous breakthrough is achieved. An essential feature of scaling from one vessel to the next is the requirement that the underlying physics does not change adversely. One may have confidence in scaling if (1) correlations and formulas capture the relevant physics; (2) the underlying physics does not change from the conditions under which it was developed to the conditions of interest; (3) all factors relevant to scaling have been incorporated, including flow, material, and geometric considerations; and (4) the uncertainty in the relationships is sufficiently narrow to meet required specifications. Although the central upwell

  6. High frequency responses of nanoplankton and microplankton to wind-driven upwelling off northern Chile

    Science.gov (United States)

    Aguilera, Victor; Escribano, Ruben; Herrera, Liliana

    2009-08-01

    Autotrophic and heterotrophic nanoplankton and microplankton vary widely in quantity and composition in coastal upwelling zones, causing a highly heterogeneous distribution of food resources for higher trophic levels. Here, we assessed daily changes in size-fractioned biomass and community structure of nanoplankton and microplankton at two upwelling sites off northern Chile, Mejillones (23°S) and Chipana (21°S), during summer 2006, winter 2006 and summer 2007 as related to changes in oceanographic conditions upon upwelling variation. We found highly-significant changes in quantity and community structure (species diversity and richness) of both nanoplankton and microplankton fractions after 3-5 days of observations. These changes were coupled to an intermittent upwelling regime reflected in the alongshore component of the wind. After a few days the whole community was modified in terms of species and size structure. Over-imposing this variability, during winter 2006 there was a strong perturbation of remote origin that substantially impacted temperature, oxygenation and stratification of the water column. This "abnormal" warming event altered the upwelling regime, but its impact on abundance and composition of the nanoplankton and microplankton fractions was uncertain. Over the short-time scale however, we found a strong coupling between daily changes in the alongshore component of wind and nanoplankton and microplankton abundances and their structure. All these findings indicate that despite the high biological productivity of this upwelling region, high frequency variation induced by wind forcing may be a major regulator of food resources (quantity and quality) for primary consumers, such as zooplankton, fish larvae and benthic organisms in the near-shore area. This high frequency variation may also impose a key constrain for prey-predator encounter rates and survival of short-lived zooplankton and invertebrate and fish larvae in the upwelling zone.

  7. Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium

    Science.gov (United States)

    Steinfeldt, R.; Sültenfuß, J.; Dengler, M.; Fischer, T.; Rhein, M.

    2015-12-01

    Upwelling is an important process, bringing gases and nutrients into the ocean mixed layer. The upwelling velocities, however, are too small to be measured directly. Here we use the surface disequilibrium of the 3He / 4He ratio measured in two coastal upwelling regions off Peru in the Pacific ocean and off Mauritania in the Atlantic ocean to calculate the regional distribution of vertical velocities. To also account for the fluxes by diapycnal mixing, microstructure-based observations of the vertical diffusivity have been performed on all four cruises analysed in this study. The upwelling velocities in the coastal regions vary between 1.1 ± 0.3 × 10-5 and 2.8 ± 1.5 × 10-5 m s-1 for all cruises. Vertical velocities are also inferred from the divergence of the wind-driven Ekman transport. In the coastal regimes, both methods agree within the error range. Further offshore, the helium-derived vertical velocity still reaches 1 × 10-5 m s-1, whereas the wind-driven upwelling from Ekman suction is smaller by up to 1 order of magnitude. One reason for this difference is ascribed to eddy-induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium-derived vertical velocities and the vertical diffusivities. The advective part of these fluxes makes up at about 50 % of the total. The nutrient flux into the mixed layer in the coastal upwelling regimes is equivalent to a net community production (NCP) of 1.3 ± 0.3 g C m2 d-1 off Peru and 1.6-2.1 ± 0.5 g C m2 d-1 off Mauritania.

  8. A Lagrangian study tracing water parcel origins in the Canary Upwelling System

    Directory of Open Access Journals (Sweden)

    Evan Mason

    2012-08-01

    Full Text Available The regional ocean circulation within the Canary Upwelling System between 31°N and 35°N is studied using numerical tools. Seasonal mean and near-instantaneous velocity fields from a previously-generated climatological Regional Ocean Modelling System (ROMS solution of the Canary Basin are used to force a series of offline Lagrangian particle-tracking experiments. The primary objective is to identify the pathways through which water parcels arrive at the upwelling region north of Cape Ghir. Examining year-long pathways, the Azores Current contributes over 80% of particles annually, of which a large proportion arrive directly from offshore (from the northwest, while others travel along the shelf and slope from the Gulf of Cadiz. The remaining ~20% originate within the Gulf of Cadiz or come from the south, although the southern contribution is only significant in autumn and winter. When season-long pathways are considered, the alongshore contributions become increasingly important: northern contributions reach 40% in spring and summer, while southern values exceed 35% in winter. This study also shows that coastal upwelling changes both spatially and temporally. Upwelling becomes intensified near Cape Beddouza, with most upwelling occurring within ~40 km from shore although significant values may reach as far as 120 km offshore north of Cape Beddouza; at these locations the offshore integrated upwelling reaches as much as 4 times the offshore Ekman transport. In the Cape Beddouza area (32°N to 33°N, upwelling is negligible in February but intensifies in autumn, reaching as much as 3 times the offshore Ekman transport.

  9. The NAO Influence on the Early to Mid-Holocene North Atlantic Coastal Upwelling

    Science.gov (United States)

    Hernandez, A.; Cachão, M.; Sousa, P.; Trigo, R. M.; Freitas, M. C.

    2017-12-01

    Coastal upwelling regions yield some of the oceanic most productive ecosystems, being crucial for the worldwide social and economic development. Most upwelling systems, emerging cold nutrient-rich deep waters, are located in the eastern boundaries of the Atlantic and Pacific basins, and are driven by meridional wind fields parallel to the coastal shore. These winds are associated with the subsiding branch of the large-scale Anticyclonic high pressure systems that dominate the subtropical ocean basins, and therefore can be displaced or intensified within the context of past and future climate changes. However, the role of the current global warming influencing the coastal upwelling is, as yet, unclear. Therefore it is essential to derive a long-term perspective, beyond the era of instrumental measurements, to detect similar warm periods in the past that have triggered changes in the upwelling patterns. In this work, the upwelling dynamics in the Iberian North Atlantic margin during the early and mid-Holocene is reconstructed, using calcareous nannofossils from a decadally resolved estuarine sediment core located in southwestern Portugal. Results suggest that the coastal dynamics reflects changes in winds direction likely related to shifts in the NAO-like conditions. Furthermore, the reconstructed centennial-scale variations in the upwelling are synchronous with changes in solar irradiance, a major external forcing factor of the climate system that is known to exert influence in atmospheric circulation patterns. In addition, these proxy-based data interpretations are in agreement with wind field and solar irradiance simulation modelling for the mid-Holocene. Therefore, the conclusion that the solar activity via the NAO modulation controlled the North Atlantic upwelling of western Iberia during the early and mid-Holocene at decadal to centennial timescales can be derived. The financial support for attending this meeting was possible through FCT project UID/GEO/50019

  10. Glacial-Holocene variability in pelagic denitrification and OMZ intensity along the NW Mexican Margin

    Science.gov (United States)

    Ontiveros Cuadras, J. F.; Thunell, R.; Ruiz-Fernandez, A. C.; Machain-Castillo, M. L.; Tappa, E.

    2017-12-01

    Denitrification of fixed nitrogen represents a substantial loss of bioavailable nitrogen from the ocean, thus playing a major role in the global nitrogen cycle. Water-column (pelagic) denitrification occurs mostly in the oxygen minimum zones (OMZs), which are situated beneath coastal upwelling areas that are characterized by high settling fluxes of organic detritus and high rates of oxygen utilization from remineralization. Our study uses biogenic components (total organic carbon and opal) and δ15N values of sediments from the NW Mexican Margin to reconstruct variations in denitrification and strength of the OMZ in the eastern tropical North Pacific (ETNP) for the last 36,000 years. During the last glacial period (LGM, 23-18 kyr) the associations between relatively low δ15N values (7-8‰) and low TOC (2-4%) and opal (1-4%) content indicates reduced denitrification due to reduced upwelling and decreased flux of organic matter through the OMZ. This was followed by abrupt acceleration of water-column denitrification (δ15N, 7-10‰) and the strengthening of the OMZ during the latter half of Heinrich Stadial 1 (HS1; 18-14.7 kyr). However, the biogenic component of sediments deposited during HS1 do not increase appreciably, suggesting that the increase in denitrification was not driven by an increase in productivity. Furthermore, the increase in δ15N precedes the deglacial decrease in planktonic foraminiferal δ18O which mostly occurs during the Bolling Alerod (14.7-12.9 kyr). This suggests that the increase in denitrification was not a response to surface warming. Rather, we attribute the rapid increase in denitrification during HS1 to reduced ventilation of the ETNP OMZ. Following the peak in denitrification at the end of HS1, we observe a small but steady decline in δ15N over the last 15 kyr. Higher TOC in Holocene sediments relative to glacial sediments suggests that increased productivity has played a role in maintaining a strong OMZ throughout the Holocene.

  11. Benthic primary production in an upwelling-influenced coral reef, Colombian Caribbean

    Directory of Open Access Journals (Sweden)

    Corvin Eidens

    2014-09-01

    Full Text Available In Tayrona National Natural Park (Colombian Caribbean, abiotic factors such as light intensity, water temperature, and nutrient availability are subjected to high temporal variability due to seasonal coastal upwelling. These factors are the major drivers controlling coral reef primary production as one of the key ecosystem services. This offers the opportunity to assess the effects of abiotic factors on reef productivity. We therefore quantified primary net (Pn and gross production (Pg of the dominant local primary producers (scleractinian corals, macroalgae, algal turfs, crustose coralline algae, and microphytobenthos at a water current/wave-exposed and-sheltered site in an exemplary bay of Tayrona National Natural Park. A series of short-term incubations was conducted to quantify O2 fluxes of the different primary producers during non-upwelling and the upwelling event 2011/2012, and generalized linear models were used to analyze group-specific O2 production, their contribution to benthic O2 fluxes, and total daily benthic O2 production. At the organism level, scleractinian corals showed highest Pn and Pg rates during non-upwelling (16 and 19 mmol O2 m−2 specimen area h−1, and corals and algal turfs dominated the primary production during upwelling (12 and 19 mmol O2 m−2 specimen area h−1, respectively. At the ecosystem level, corals contributed most to total Pn and Pg during non-upwelling, while during upwelling, corals contributed most to Pn and Pg only at the exposed site and macroalgae at the sheltered site, respectively. Despite the significant spatial and temporal differences in individual productivity of the investigated groups and their different contribution to reef productivity, differences for daily ecosystem productivity were only present for Pg at exposed with higher O2 fluxes during non-upwelling compared to upwelling. Our findings therefore indicate that total benthic primary productivity of local autotrophic reef

  12. One-dimensional advection diffusion modeling of upwelled hyporheic stream temperature along Deer Creek, Vina, California

    Science.gov (United States)

    Butler, N. L.; Hunt, J. R.; Tompkins, M. R.

    2011-12-01

    Hyporheic exchange can locally mitigate thermal stress caused by high water temperatures by upwelling water cooler than ambient stream temperatures and thus providing thermal refuge for critical cold water organisms like salmonids. Ten hyporheic exchange locations were identified by dye tracer experiments along a 16 km stretch of Deer Creek near Vina, California. Four months of continuous temperature measurements were made in the late summer of 2005 at each downwelling and upwelling location and revealed upwelled temperatures that were lagged in time and damped in amplitude. Upwelling hyporheic temperatures that could provide thermal refuge were observed in seven of the ten temperature records. This data was modeled by an analytical one-dimensional advection-diffusion equation solution using subsurface water velocity and the hydrodynamic dispersivity fitting parameters. At each location variations in upwelling temperature are explained by changing subsurface water velocities and flow pathways. The lag time in hyporheic heat flow ranged from a few hours to 44 hours over distances of 15 to 76 meters. The daily stream temperature variation was on the order of 10°C, which was reduced to 1 to 8°C in the upwelling hyporheic flow. At four locations, there was evidence that changes in stream flow produced changes in the amplitude and phase of the upwelling hyporheic water temperature by altering both the subsurface water velocity and hydrodynamic dispersivity. At two locations, additional cold water refuge was created by decreases in surface water flow because it reduced the estimated subsurface water velocity increasing the lag time between the peak surface water and subsurface water temperatures. Increases in surface water flow increased the dispersivity at three locations providing more cold water refuge by reducing the amplitude of the upwelling hyporheic temperature. Such changes alter thermal refuge for salmonids placing a new emphasis on managing surface water

  13. Natural ocean acidification at Papagayo upwelling system (north Pacific Costa Rica: implications for reef development

    Directory of Open Access Journals (Sweden)

    C. Sánchez-Noguera

    2018-04-01

    Full Text Available Numerous experiments have shown that ocean acidification impedes coral calcification, but knowledge about in situ reef ecosystem response to ocean acidification is still scarce. Bahía Culebra, situated at the northern Pacific coast of Costa Rica, is a location naturally exposed to acidic conditions due to the Papagayo seasonal upwelling. We measured pH and pCO2 in situ during two non-upwelling seasons (June 2012, May–June 2013, with a high temporal resolution of every 15 and 30 min, respectively, using two Submersible Autonomous Moored Instruments (SAMI-pH, SAMI-CO2. These results were compared with published data from the 2009 upwelling season. Findings revealed that the carbonate system in Bahía Culebra shows a high temporal variability. Incoming offshore waters drive intra- and interseasonal changes. Lowest pH (7.8 and highest pCO2 (658.3 µatm values measured during a cold-water intrusion event in the non-upwelling season were similar to those minimum values reported from upwelling season (pH  =  7.8, pCO2  =  643.5 µatm, unveiling that natural acidification also occurs sporadically in the non-upwelling season. This affects the interaction of photosynthesis, respiration, calcification and carbonate dissolution and the resulting diel cycle of pH and pCO2 in the reefs of Bahía Culebra. During the non-upwelling season, the aragonite saturation state (Ωa rises to values of  >  3.3 and during the upwelling season falls below 2.5. The Ωa threshold values for coral growth were derived from the correlation between measured Ωa and coral linear extension rates which were obtained from the literature and suggest that future ocean acidification will threaten the continued growth of reefs in Bahía Culebra. These data contribute to building a better understanding of the carbonate system dynamics and coral reefs' key response (e.g., coral growth to natural low-pH conditions, in upwelling areas in the eastern tropical

  14. Low thermal emissivity surfaces using AgNW thin films

    Science.gov (United States)

    Pantoja, Elisa; Bhatt, Rajendra; Liu, Anping; Gupta, Mool C.

    2017-12-01

    The properties of silver nanowire (AgNW) films in the optical and infrared spectral regime offer an interesting opportunity for a broad range of applications that require low-emissivity coatings. This work reports a method to reduce the thermal emissivity of substrates by the formation of low-emissivity AgNW coating films from solution. The spectral emissivity was characterized by thermal imaging with an FLIR camera, followed by Fourier transform infrared spectroscopy. In a combined experimental and simulation study, we provide fundamental data of the transmittance, reflectance, haze, and emissivity of AgNW thin films. Emissivity values were finely tuned by modifying the concentration of the metal nanowires in the films. The simulation models based on the transfer matrix method developed for the AgNW thin films provided optical values that show a good agreement with the measurements.

  15. Influence of Coastal Upwelling on SST Trends along the South Coast of Java.

    Science.gov (United States)

    Varela, R; Santos, F; Gómez-Gesteira, M; Álvarez, I; Costoya, X; Días, J M

    2016-01-01

    The south coast of Java has warmed at a much lower rate than adjacent ocean locations over the last three decades (1982-2015). This behavior can be observed during the upwelling season (July-October) and it is especially patent in August and September when upwelling attains the highest values. Although different warming rates (ocean-coast) had been previously observed in other areas around the world, this behavior was always linked to situations where upwelling increased or remained unchanged. South Java warming is observed at ocean locations and cooling near shore but under a scenario of decreasing upwelling (~30% in some cases). The origin of coastal cooling is due to changes in the vertical structure of the water column. A vein of subsurface water, which has cooled at a rate higher than 0.3°C per decade, is observed to enter from the northwestern part of the study area following the South Java Current. This water only manifests at surface near coast, where it is pumped up by coastal upwelling.

  16. Environmental control on the variability of DMS and DMSP in the Mauritanian upwelling region

    Directory of Open Access Journals (Sweden)

    C. Zindler

    2012-03-01

    Full Text Available Dimethylsulphide (DMS and dissolved and particulate dimethylsulfoniopropionate (DMSPd, DMSPp were measured in near-surface waters along the Mauritanian coast, Northwest Africa, during the upwelling season in February 2008. DMS, DMSPd and DMSPp surface concentrations of up to 10 nmol L−1, 15 nmol L−1 and 990 nmol L−1, respectively, were measured. However, the DMS concentrations measured are in the low range compared to other upwelling regions. The maximum DMSPp concentration is the highest reported from upwelling regions so far, which might indicate that the Mauritanian upwelling is a hot spot for DMSP. Within the phytoplankton groups, dinoflagellates were identified as important contributors to DMS concentrations, while other algae seemed to have only a minor or no influence on DMS and DMSP concentrations. A pronounced switch from high DMSP to high DMS concentrations was observed when the nitrogen to phosphorus ratio (N:P was below 7. The high DMS/DMSP ratios at N:P ratios <7 indicate that nitrogen limitation presumably triggered a switch from DMSP to DMS independent of the species composition. Our results underline the importance of coastal upwelling regions as a local source for surface seawater sulphur.

  17. Characterization of gold mineralization in Garin Hawal area, Kebbi State, NW Nigeria, using remote sensing

    Directory of Open Access Journals (Sweden)

    Talaat M. Ramadan

    2010-12-01

    Full Text Available Garin Hawal area, Kebbi State, NW Nigeria is part of the Neoproterozoic to Early Phanerozoic terrane separating the west African and Congo Cratons. Three main gold-bearing shear zones were detected in the study area from the processed Landsat ETM+ images and extensive ground investigation. Field and petrographical studies indicate that the Neoproterozoic rocks are represented by a highly folded and faulted belt constituted of hornblende, muscovite and graphite schist. They are intruded by granondiorites and late to post granitic dykes. Extensive alteration zones were identified using high resolution QuickBird image along Garin Hawal shear zone. The alteration zones and associated quartz veins are generally concordant with the main NE–SW regional structural trend and are dipping to the NW. Geochemical studies indicate that the gold content reaches 8 g/t in the alteration zones, while it reaches up to 35 g/t in the quartz veins. Mineralogical studies indicate that the alterations are strongly potassium-enriched. Pyrophyllite, kaolinite, illite, gypsum and quartz also occur. The main ore minerals are gold, chalcopyrite, arsenopyrite, pyrite, galena and iron oxides. This study indicates that the alteration zones and the associated quartz veins in the muscovite schist are promising and need more detailed exploration for Au and Ag mineralization to evaluate their potential.

  18. Intracratonic asthenosphere upwelling and lithosphere rejuvenation beneath the Hoggar swell (Algeria): Evidence from HIMU metasomatised lherzolite mantle xenoliths

    Science.gov (United States)

    Beccaluva, L.; Azzouni-Sekkal, A.; Benhallou, A.; Bianchini, G.; Ellam, R. M.; Marzola, M.; Siena, F.; Stuart, F. M.

    2007-08-01

    The mantle xenoliths included in Quaternary alkaline volcanics from the Manzaz-district (Central Hoggar) are proto-granular, anhydrous spinel lherzolites. Major and trace element analyses on bulk rocks and constituent mineral phases show that the primary compositions are widely overprinted by metasomatic processes. Trace element modelling of the metasomatised clinopyroxenes allows the inference that the metasomatic agents that enriched the lithospheric mantle were highly alkaline carbonate-rich melts such as nephelinites/melilitites (or as extreme silico-carbonatites). These metasomatic agents were characterized by a clear HIMU Sr-Nd-Pb isotopic signature, whereas there is no evidence of EM1 components recorded by the Hoggar Oligocene tholeiitic basalts. This can be interpreted as being due to replacement of the older cratonic lithospheric mantle, from which tholeiites generated, by asthenospheric upwelling dominated by the presence of an HIMU signature. Accordingly, this rejuvenated lithosphere (accreted asthenosphere without any EM influence), may represent an appropriate mantle section from which deep alkaline basic melts could have been generated and shallower mantle xenoliths sampled, respectively. The available data on lherzolite xenoliths and alkaline lavas (including He isotopes, Ra Pan-African basement. This can be considered a far-field foreland reaction of the Africa-Europe collisional system since the Eocene.

  19. Lagrangian Timescales of Southern Ocean Upwelling in a Hierarchy of Model Resolutions

    Science.gov (United States)

    Drake, Henri F.; Morrison, Adele K.; Griffies, Stephen M.; Sarmiento, Jorge L.; Weijer, Wilbert; Gray, Alison R.

    2018-01-01

    In this paper we study upwelling pathways and timescales of Circumpolar Deep Water (CDW) in a hierarchy of models using a Lagrangian particle tracking method. Lagrangian timescales of CDW upwelling decrease from 87 years to 31 years to 17 years as the ocean resolution is refined from 1° to 0.25° to 0.1°. We attribute some of the differences in timescale to the strength of the eddy fields, as demonstrated by temporally degrading high-resolution model velocity fields. Consistent with the timescale dependence, we find that an average Lagrangian particle completes 3.2 circumpolar loops in the 1° model in comparison to 0.9 loops in the 0.1° model. These differences suggest that advective timescales and thus interbasin merging of upwelling CDW may be overestimated by coarse-resolution models, potentially affecting the skill of centennial scale climate change projections.

  20. Spatiotemporal trends in the southwest monsoon wind-driven upwelling in the southwestern part of the South China Sea.

    Directory of Open Access Journals (Sweden)

    Poh Heng Kok

    Full Text Available This study analyzes two wind-induced upwelling mechanisms, namely, Ekman transport and Ekman pumping that occur during the southwest monsoon. The results suggest that the coastline of the east coast of Peninsular Malaysia (ECPM is affected by upwelling with spatiotemporal variations. Characterization of upwelling by using wind-induced upwelling indexes (UIW indicate the existence of favorable upwelling conditions from May to September. Upwelling intensity increased in May and peaked in August before declining in September, decreasing intensity from the southern tip towards the northern tip along the coastline of the ECPM. The existence of upwelling along the ECPM has resulted in an important difference between the SSTs of the inshore and the oceanic regions. Nonetheless, the use of the SST gradient between the inshore and the oceanic SSTs to characterize upwelling (UISST was found to be unsuitable because the SST along the ECPM was affected by water advection from the Java Sea and incessant changes in the SST. In order to indicate the major contributor of wind-induced upwelling along the ECPM in terms of the spatiotemporal scale, a comparison between Ekman transport and Ekman pumping was drawn by integrating Ekman pumping with respect to the distance where the positive wind stress curl existed. The estimation of Ekman transport and Ekman pumping indicated that Ekman pumping played a major role in contributing towards upwelling in any particular month during the southwest monsoon along the entire coastline of the ECPM as compared to Ekman transport, which contributed towards more than half of the total upwelling transport. By dividing the ECPM into three coastal sections, we observed that Ekman pumping was relatively predominant in the middle and northern coasts, whereas both Ekman transport and Ekman pumping were equally prevalent in the southern coast.

  1. The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO2 change

    International Nuclear Information System (INIS)

    Watson, Andrew J.; Naveira Garabato, Alberto C.

    2006-01-01

    Decreased ventilation of the Southern Ocean in glacial time is implicated in most explanations of lower glacial atmospheric CO 2 . Today, the deep (>2000 m) ocean south of the Polar Front is rapidly ventilated from below, with the interaction of deep currents with topography driving high mixing rates well up into the water column. We show from a buoyancy budget that mixing rates are high in all the deep waters of the Southern Ocean. Between the surface and 2000 m depth, water is upwelled by a residual meridional overturning that is directly linked to buoyancy fluxes through the ocean surface. Combined with the rapid deep mixing, this upwelling serves to return deep water to the surface on a short time scale. We propose two new mechanisms by which, in glacial time, the deep Southern Ocean may have been more isolated from the surface. Firstly, the deep ocean appears to have been more stratified because of denser bottom water resulting from intense sea ice formation near Antarctica. The greater stratification would have slowed the deep mixing. Secondly, subzero atmospheric temperatures may have meant that the present-day buoyancy flux from the atmosphere to the ocean surface was reduced or reversed. This in turn would have reduced or eliminated the upwelling (contrary to a common assumption, upwelling is not solely a function of the wind stress but is coupled to the air/sea buoyancy flux too). The observed very close link between Antarctic temperatures and atmospheric CO 2 could then be explained as a natural consequence of the connection between the air/sea buoyancy flux and upwelling in the Southern Ocean, if slower ventilation of the Southern Ocean led to lower atmospheric CO 2 . Here we use a box model, similar to those of previous authors, to show that weaker mixing and reduced upwelling in the Southern Ocean can explain the low glacial atmospheric CO 2 in such a formulation

  2. Gradients in microbial methanol uptake: productive coastal upwelling waters to oligotrophic gyres in the Atlantic Ocean

    Science.gov (United States)

    Dixon, Joanna L; Sargeant, Stephanie; Nightingale, Philip D; Colin Murrell, J

    2013-01-01

    Methanol biogeochemistry and its importance as a carbon source in seawater is relatively unexplored. We report the first microbial methanol carbon assimilation rates (k) in productive coastal upwelling waters of up to 0.117±0.002 d−1 (∼10 nmol l−1 d−1). On average, coastal upwelling waters were 11 times greater than open ocean northern temperate (NT) waters, eight times greater than gyre waters and four times greater than equatorial upwelling (EU) waters; suggesting that all upwelling waters upon reaching the surface (⩽20 m), contain a microbial population that uses a relatively high amount of carbon (0.3–10 nmol l−1 d−1), derived from methanol, to support their growth. In open ocean Atlantic regions, microbial uptake of methanol into biomass was significantly lower, ranging between 0.04–0.68 nmol l−1 d−1. Microbes in the Mauritanian coastal upwelling used up to 57% of the total methanol for assimilation of the carbon into cells, compared with an average of 12% in the EU, and 1% in NT and gyre waters. Several methylotrophic bacterial species were identified from open ocean Atlantic waters using PCR amplification of mxaF encoding methanol dehydrogenase, the key enzyme in bacterial methanol oxidation. These included Methylophaga sp., Burkholderiales sp., Methylococcaceae sp., Ancylobacter aquaticus, Paracoccus denitrificans, Methylophilus methylotrophus, Methylobacterium oryzae, Hyphomicrobium sp. and Methylosulfonomonas methylovora. Statistically significant correlations for upwelling waters between methanol uptake into cells and both chlorophyll a concentrations and methanol oxidation rates suggest that remotely sensed chlorophyll a images, in these productive areas, could be used to derive total methanol biological loss rates, a useful tool for atmospheric and marine climatically active gas modellers, and air–sea exchange scientists. PMID:23178665

  3. Upwelling, species, and depth effects on coral skeletal cadmium-to-calcium ratios (Cd/Ca)

    Science.gov (United States)

    Matthews, Kathryn A.; Grottoli, Andréa G.; McDonough, William F.; Palardy, James E.

    2008-09-01

    Skeletal cadmium-to-calcium (Cd/Ca) ratios in hermatypic stony corals have been used to reconstruct changes in upwelling over time, yet there has not been a systematic evaluation of this tracer's natural variability within and among coral species, between depths and across environmental conditions. Here, coral skeletal Cd/Ca ratios were measured in multiple colonies of Pavona clavus, Pavona gigantea and Porites lobata reared at two depths (1 and 7 m) during both upwelling and nonupwelling intervals in the Gulf of Panama (Pacific). Overall, skeletal Cd/Ca ratios were significantly higher during upwelling than during nonupwelling, in shallow than in deep corals, and in both species of Pavona than in P. lobata. P. lobata skeletal Cd/Ca ratios were uniformly low compared to those in the other species, with no significant differences between upwelling and nonupwelling values. Among colonies of the same species, skeletal Cd/Ca ratios were always higher in all shallow P. gigantea colonies during upwelling compared to nonupwelling, though the magnitude of the increase varied among colonies. For P. lobata, P. clavus and deep P. gigantea, changes in skeletal Cd/Ca ratios were not consistent among all colonies, with some colonies having lower ratios during upwelling than during nonupwelling. No statistically significant relationships were found between skeletal Cd/Ca ratios and maximum linear skeletal extension, δ 13C or δ 18O, suggesting that at seasonal resolution the Cd/Ca signal was decoupled from growth rate, coral metabolism, and ocean temperature and salinity, respectively. These results led to the following conclusions, (1) coral skeletal Cd/Ca ratios are independent of skeletal extension, coral metabolism and ambient temperature/salinity, (2) shallow P. gigantea is the most reliable species for paleoupwelling reconstruction and (3) the average Cd/Ca record of several colonies, rather than of a single coral, is needed to reliably reconstruct paleoupwelling events.

  4. Evaluation of ERTS data for certain oceanographic uses. [upwelling, water circulation, and pollution in Great Lakes

    Science.gov (United States)

    Strong, A. E. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Upwelling along the eastern shore of Lake Michigan was occurring during the 3 and 21 August 1973 visits by ERTS-1. The NOAA-2 VHRR thermal-IR data are being digitized for comparison. Early indications are that these upwellings induced a calcium carbonate precipitate to form in the surface waters. It is most pronounced in the MSS-4 channel. On the lake bottom this jell-like sediment is known as marl and adds to the eutrophication of the lake. This phenomenon may help to explain the varve-like nature of bottom cores that have been observed in the Great Lakes.

  5. What controls biological production in coastal upwelling systems? Insights from a comparative modeling study

    Directory of Open Access Journals (Sweden)

    Z. Lachkar

    2011-10-01

    Full Text Available The magnitude of net primary production (NPP in Eastern Boundary Upwelling Systems (EBUS is traditionally viewed as directly reflecting the wind-driven upwelling intensity. Yet, different EBUS show different sensitivities of NPP to upwelling-favorable winds (Carr and Kearns, 2003. Here, using a comparative modeling study of the California Current System (California CS and Canary Current System (Canary CS, we show how physical and environmental factors, such as light, temperature and cross-shore circulation modulate the response of NPP to upwelling strength. To this end, we made a series of eddy-resolving simulations of the two upwelling systems using the Regional Oceanic Modeling System (ROMS, coupled to a nitrogen-based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD ecosystem model. Using identical ecological/biogeochemical parameters, our coupled model simulates a level of NPP in the California CS that is 50 % smaller than that in the Canary CS, in agreement with observationally based estimates. We find this much lower NPP in the California CS despite phytoplankton in this system having nearly 20 % higher nutrient concentrations available to fuel their growth. This conundrum can be explained by: (1 phytoplankton having a faster nutrient-replete growth in the Canary CS relative to the California CS; a consequence of more favorable light and temperature conditions in the Canary CS, and (2 the longer nearshore water residence times in the Canary CS, which permit a larger buildup of biomass in the upwelling zone, thereby enhancing NPP. The longer residence times in the Canary CS appear to be a result of the wider continental shelves and the lower mesoscale activity characterizing this upwelling system. This results in a weaker offshore export of nutrients and organic matter, thereby increasing local nutrient recycling and reducing the spatial decoupling between new and export production in the Canary CS. Our results suggest that climate change

  6. Coastal upwelling and downwelling forcing of circulation in a semi-enclosed bay: Ria de Vigo

    Science.gov (United States)

    Barton, E. D.; Largier, J. L.; Torres, R.; Sheridan, M.; Trasviña, A.; Souza, A.; Pazos, Y.; Valle-Levinson, A.

    2015-05-01

    Semi-enclosed bays in upwelling regions are exposed to forcing related to winds, currents and buoyancy over the shelf. The influence of this external forcing is moderated by factors such as connectivity to the open ocean, shelter by surrounding topography, dimensions of the bay, and freshwater outflows. Such bays, preferred locations for ports, mariculture, marine industry, recreational activities and coastal settlement, present a range of characteristics, understanding of which is necessary to their rational management. Observations in such a semi-enclosed bay, the Ria de Vigo in Spain, are used to characterize the influence of upwelling and downwelling pulses on its circulation. In this location, near the northern limit of the Iberian upwelling system, upwelling events dominate during a short summer season and downwelling events the rest of the year. The ria response to the external forcing is central to nutrient supply and resultant plankton productivity that supports its high level of cultured mussel production. Intensive field studies in September 2006 and June 2007 captured a downwelling event and an upwelling event, respectively. Data from eight current profiler moorings and boat-based MiniBat/ADCP surveys provided an unprecedented quasi-synoptic view of the distribution of water masses and circulation patterns in any ria. In the outer ria, circulation was dominated by the introduction of wind-driven alongshore flow from the external continental shelf through the ria entrances and its interaction with the topography. In the middle ria, circulation was primarily related to the upwelling/downwelling cycle, with a cool, salty and dense lower layer penetrating to the inner ria during upwelling over the shelf. A warmer, lower salinity and less dense surface layer of coastal waters flowed inward during downwelling. Without external forcing, the inner ria responded primarily to tides and buoyancy changes related to land runoff. Under both upwelling and downwelling

  7. Distribution of upwelling index planktonic foraminifera in the sediments of the western continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    d'UllC zone d'upwelling, marge continentale de I'Indc I Les foraminifcrcs planctoniques. radiolaires. carhonates et Ie carhone organique. ont etc analyses dans vingt et un cchantillons de sediments. La repartition de ces parame tres revcle que les... sediments contienncnt la signature d'un upwelling. L'ahondance relative des foraminitcres planctoniques, des radiolaires et les teneurs en carbonates et en c

  8. Evaluation of wind vectors measured by QuikSCAT using ocean buoy data along the Galician coast (NW Iberian Peninsula)

    Science.gov (United States)

    Alvarez, I.; Gomez-Gesteira, M.; deCastro, M.; Sousa, M. C.; Dias, J. M.; Santos, F.

    2012-04-01

    Wind above sea surface constitutes a key parameter to analyze coastal phenomena, like upwelling in the NW part of the Iberian Peninsula. The present work analyzes the accuracy of QuikSCAT for the period 2000-2009 by comparing satellite data with in situ data from three buoys placed along the NW coast of the Iberian Peninsula. The use of these long data series has two main objectives, on the one hand, the margin of error diminishes with the extent of the series and, on the other hand, it allows capturing the high inter-annual variability of the area. According to previous studies, the wet season is characterized by a high variability, in such a way that wind patterns change from year to year. The comparison confirms a low skill of QuikSCAT for low speed winds (<3 m/s) as previously pointed out by other authors. Once these winds were discarded, QuikSCAT revealed a higher accuracy for winds within the range 6-12 m/s. In direction, winds blowing from coast seem to be less accurately calculated by the satellite. Statistical results were similar for the three buoys in spite of the different coastal orientations. In average, the RMSE and bias for wind speed were 1.5 m/s and 0.2 m/s, respectively. Statistical data were also similar for wind direction, with the mean RMSE on the order of 34° and the mean bias on the order of 4° in absolute value. These statistical parameters are at least as accurate as those calculated in other near-shore areas all over the world. In particular, the bias was observed to be lower (in absolute value) than measured by most of the authors, which is possibly due to the high percentage of sampled winds lying within the interval [6-12] m/s, where satellite measurements are more accurate.

  9. Nutrient regime and upwelling in the northern Benguela since the middle Holocene in a global context – a multi-proxy approach

    Directory of Open Access Journals (Sweden)

    S. Meisel

    2011-08-01

    Full Text Available The last 5500 years of climate change and environmental response in the northern Benguela Coastal Upwelling are reconstructed by means of three sediment cores from the inner shelf off central Namibia. The study is based on nutrient (δ15N, δ13C and productivity proxies (accumulation rates of total organic carbon; ARTOC. Reconstructed sea surface temperatures (alkenone-derived SST and temperatures at subsurface depths (Tδ18O; based on tests of planktonic foraminifers reflect the physical boundary conditions. The selection of proxy indicators proved a valuable basis for robust palaeo-climatic reconstructions, with the resolution ranging from multi-decadal (NAM1 over centennial (core 178 to millennial scale (core 226620. The northern Benguela experienced pronounced and rapid perturbation during the middle and late Holocene, and apparently, not all are purely local in character. In fact, numerous correlations with records from the adjacent South African subcontinent and the northern hemisphere testify to global climatic teleconnections. The Holocene Hypsithermal, for instance, is just as evident as the Little Ice Age (LIA and the Roman Warm Period. The marked SST-rise associated with the latter is substantiated by other marine and terrestrial data from the South African realm. The LIA (at least its early stages manifests itself in intensified winds and upwelling, which accords with increased rainfall receipts above the continental interior. It appears that climate signals are transferred both via the atmosphere and ocean. The combined analysis of SST and Tδ18O proved a useful tool in order to differentiate between both pathways. SSTs are primarily controlled by the intensity of atmospheric circulation features, reflecting changes of upwelling-favourable winds. Tδ18O records the temperature of the source water and often correlates with global ocean conveyor speed due to varying inputs of warm Agulhas Water. It seems as though conveyor slowdown or

  10. Coastal upwelling fluxes of O2, N2O, and CO2 assessed from continuous atmospheric observations at Trinidad, California

    Directory of Open Access Journals (Sweden)

    T. J. Lueker

    2004-01-01

    Full Text Available Continuous atmospheric records of O2/N2, CO2 and N2O obtained at Trinidad, California document the effects of air-sea exchange during coastal upwelling and plankton bloom events. The atmospheric records provide continuous observations of air-sea fluxes related to synoptic scale upwelling events over several upwelling seasons. Combined with satellite, buoy and local meteorology data, calculated anomalies in O2/N2 and N2O were utilized in a simple atmospheric transport model to compute air-sea fluxes during coastal upwelling. CO2 fluxes were linked to the oceanic component of the O2 fluxes through local hydrographic data and estimated as a function of upwelling intensity (surface ocean temperature and wind speed. Regional air-sea fluxes of O2/N2, N2O, and CO2 during coastal upwelling were estimated with the aid of satellite wind and SST data. Upwelling CO2 fluxes were found to represent ~10% of export production along the northwest coast of North America. Synoptic scale upwelling events impact the net exchange of atmospheric CO2 along the coastal margin, and will vary in response to the frequency and duration of alongshore winds that are subject to climate change.

  11. Development of upwelling on pathway and freshwater transport of Pearl River plume in northeastern South China Sea

    Science.gov (United States)

    Chen, Zhaoyun; Jiang, Yuwu; Liu, James T.; Gong, Wenping

    2017-08-01

    In situ observations, satellite images, and numerical modeling results have shown that the Pearl River plume axis extends alongshore and passes through two separate upwelling regions—one off the Guangdong and Fujian coasts (the Yuedong upwelling) and the other in the Taiwan Bank during the initial and medium stages of the Yuedong upwelling, while it is directed offshore when the Yuedong upwelling is strong. Model experiments are conducted to examine the effects of wind strength and baroclinicity on the upwelling and the corresponding pathway and freshwater transport of the Pearl River plume. The baroclinic effect is important to intensifying the horizontal velocity at the upwelling front and freshwater transport in the northeastern South China Sea. The freshwater transport flux is further decomposed into advection, vertical shear, and tidal pumping components, and advection is the dominant contributor. As the Yuedong upwelling develops, the zone with a relatively high-pressure gradient moves offshore due to offshore Ekman transport and the shift in the upwelling front, which is responsible for the offshore transport of the river plume. When the river plume is transported to the outer-shelf, sometimes it can be further entrained into eddies, allowing its export to the open sea.

  12. The upwelling record in the sediments of the westen continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; PrakashBabu, C.; Rao, Ch.M.

    margin of India. In: Petroleum geochemistry and exploration in the Afro-Asian region, R. K. KUMAR et al., editors, Balkema, Rotterdam, pp. 347-361. PRELL W. L. (1984) Variation of monsoonal upwelling: a response to changing solar radiation. Climate...

  13. Climate change and ocean deoxygenation within intensified surface-driven upwelling circulations.

    Science.gov (United States)

    Bakun, Andrew

    2017-09-13

    Ocean deoxygenation often takes place in proximity to zones of intense upwelling. Associated concerns about amplified ocean deoxygenation arise from an arguable likelihood that coastal upwelling systems in the world's oceans may further intensify as anthropogenic climate change proceeds. Comparative examples discussed include the uniquely intense seasonal Somali Current upwelling, the massive upwelling that occurs quasi-continuously off Namibia and the recently appearing and now annually recurring 'dead zone' off the US State of Oregon. The evident 'transience' in causal dynamics off Oregon is somewhat mirrored in an interannual-scale intermittence in eruptions of anaerobically formed noxious gases off Namibia. A mechanistic scheme draws the three examples towards a common context in which, in addition to the obvious but politically problematic remedy of actually reducing 'greenhouse' gas emissions, the potentially manageable abundance of strongly swimming, finely gill raker-meshed small pelagic fish emerges as a plausible regulating factor.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

  14. Coastal upwelling along the southwest coast of India – ENSO modulation

    Directory of Open Access Journals (Sweden)

    K. Muni Krishna

    2008-06-01

    Full Text Available An index of El Niño Southern Oscillation (ENSO in the Pacific during pre monsoon season is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold ENSO events being associated with relaxation (intensification of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.

  15. Modelling shelf-ocean exchange and its biogeochemical consequences in coastal upwelling systems

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar

    margin bathymetry, and 3) what processes determine the observed variability of total organic carbon (TOC) content in shelf sediments underlying the upwelling system, with implications for the formation of petroleum source rocks. Here, a numerical ocean modeling approach is used in this thesis to explore...

  16. The potential role of mass balance models for the management of upwelling ecosystems

    DEFF Research Database (Denmark)

    Jarre, Astrid

    1998-01-01

    Upwelling ecosystems are productive fishing grounds, contributing >30% to the world's catch of marine fish. A set of seven trophic mass balance models of productive subsystems of the four largest upwelling areas is used to demonstrate key features of the modeling process and the analysis of the m......Upwelling ecosystems are productive fishing grounds, contributing >30% to the world's catch of marine fish. A set of seven trophic mass balance models of productive subsystems of the four largest upwelling areas is used to demonstrate key features of the modeling process and the analysis...... N), focusing on different biological regimes in the 1970s and 1980s. The straightforwardness of the method is emphasized as a coherent basis for more sophisticated modeling approaches. One major advantage over more traditional assessment methods is that the fishery is explicitly tied into the full...... set of species interactions, and its impact can thus be readily compared to that of other piscivores in the ecosystem. This approach consequently allows us to assess the ecological sustainability of a fishery. It therefore addresses the Code of Conduct for Responsible Fisheries recently published...

  17. On the warm nearshore bias in Pathfinder monthly SST products over Eastern Boundary upwelling systems

    CSIR Research Space (South Africa)

    Dufois, F

    2012-01-01

    Full Text Available Using in situ sea surface temperature (SST) data and MODIS/TERRA SST, the monthly AVHRR Pathfinder (version 5.0 and 5.2) SST product was evaluated within the four main Eastern Boundary Upwelling Systems. A warm bias in the monthly Pathfinder data...

  18. Climate change and ocean deoxygenation within intensified surface-driven upwelling circulations

    Science.gov (United States)

    Bakun, Andrew

    2017-08-01

    Ocean deoxygenation often takes place in proximity to zones of intense upwelling. Associated concerns about amplified ocean deoxygenation arise from an arguable likelihood that coastal upwelling systems in the world's oceans may further intensify as anthropogenic climate change proceeds. Comparative examples discussed include the uniquely intense seasonal Somali Current upwelling, the massive upwelling that occurs quasi-continuously off Namibia and the recently appearing and now annually recurring `dead zone' off the US State of Oregon. The evident `transience' in causal dynamics off Oregon is somewhat mirrored in an interannual-scale intermittence in eruptions of anaerobically formed noxious gases off Namibia. A mechanistic scheme draws the three examples towards a common context in which, in addition to the obvious but politically problematic remedy of actually reducing `greenhouse' gas emissions, the potentially manageable abundance of strongly swimming, finely gill raker-meshed small pelagic fish emerges as a plausible regulating factor. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

  19. Coastal upwelling ecosystems are known to be parts of the most ...

    African Journals Online (AJOL)

    spamer

    and a persistent wind-induced drift of surface waters offshore (Wooster ... swept away from the coast by wind-induced offshore drift. This major characteristic of coastal upwelling ecosystems has strong ecological implications (Bakun. 1996). In a recent .... wind of the peninsula, in a place where the continental shelf extends ...

  20. Observations and mechanisms of upwelling in the northern KwaZulu ...

    African Journals Online (AJOL)

    The 11-month inshore bottom-temperature record revealed five substantial upwelling events lasting 5–10 days each where temperatures decreased by about 7 °C to 17–18 °C. Satellite sea surface temperature data showed these events to coincide with cold-water plumes occupying the northern wedge of the ...

  1. Foraminiferal production and monsoonal upwelling in the Arabian sea: evidence from sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Curry, W.B.; Ostermann, D.R.; Guptha, M.V.S.; Ittekkot, V.

    (18) O values by about 1%, accurately reflecting the average 4 degrees C sea surface temperature decrease associated with the upwelling. The mean value of delta super(18) O for G. ruber was greater in the western Arabian Sea than in the central...

  2. The Benguela upwelling system off the west coast of southern Africa ...

    African Journals Online (AJOL)

    spamer

    (Schumann and Brink 1990), was obtained from measurements taken at Saldanha Bay, a coastal site adjacent to a major upwelling centre on the west coast of South Africa (Nelson and Hutchings 1983). Sea level fluctuations in such a dataset could then be attributed to wind-driven processes. Wind dataset. Wind data were ...

  3. Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

    Science.gov (United States)

    Abrantes, Fatima; Cermeno, Pedro; Lopes, Cristina; Romero, Oscar; Matos, Lélia; Van Iperen, Jolanda; Rufino, Marta; Magalhães, Vitor

    2016-07-01

    Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California, and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

  4. On the upwelling off the Southern Tip and along the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Smitha, B.R.; Sanjeevan, V.N.; VimalKumar, K.G.; Revichandran, C.

    ; the latter is forced by the longshore wind stress. Moderate to relatively intense upwelling occurs along the Kollam to Mangalore coast (9 degrees N to 13 degrees N) due to the combined action of the longshore wind stress, the coastally trapped Kelvin waves...

  5. Microbial and biogeochemical responses to projected future nitrate enrichment in the California upwelling system

    Directory of Open Access Journals (Sweden)

    Katherine Rose Marie Mackey

    2014-11-01

    Full Text Available Coastal California is a dynamic upwelling region where nitrogen (N and iron (Fe can both limit productivity and influence biogeochemistry over different spatial and temporal scales. With global change, the flux of nitrate from upwelling is expected to increase over the next century, potentially driving additional oceanic regions toward Fe limitation. In this study we explored the effect of changes in Fe/N ratio on native phytoplankton from five currently Fe-replete sites near the major California upwelling centers at Bodega Bay and Monterey Bay using nutrient addition incubation experiments. Despite the high nitrate levels (13-30 M in the upwelled water, phytoplankton at three of the five sites showed increased growth when 10 M nitrate was added. None of the sites showed enhanced growth following addition of 10 nM Fe. Nitrate additions favored slow sinking single-celled diatoms over faster sinking chain-forming diatoms, suggesting that future increases in nitrate flux could affect carbon and silicate export and alter grazer populations. In particular, solitary cells of Cylindrotheca were more abundant than the toxin-producing genus Pseudonitzschia following nitrate addition. These responses suggest the biogeochemistry of coastal California could change in response to future increases in nitrate, and multiple stressors like ocean acidification and hypoxia may further result in ecosystem shifts.

  6. Arabian Sea upwelling - A comparison between coastal and open ocean regions

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.; PrasannaKumar, S.

    The response of the eastern Arabian Sea to prevailing winds during an upwelling event, in the peak of southwest monsoon, was studied at both coastal and open ocean environment based on the data collected as a part of the Indian Joint Global Ocean...

  7. Petrogenesis and tectonic implication of the Late Triassic post-collisional volcanic rocks in Chiang Khong, NW Thailand

    Science.gov (United States)

    Qian, Xin; Wang, Yuejun; Feng, Qinglai; Zi, Jian-Wei; Zhang, Yuzhi; Chonglakmani, Chongpan

    2016-04-01

    The volcanic rocks exposed within the Chiang Khong-Lampang-Tak igneous zone in NW Thailand provide important constraints on the tectonic evolution of the eastern Paleotethys ocean. An andesite sample from the Chiang Khong area yields a zircon U-Pb age of 229 ± 4 Ma, significantly younger than the continental-arc and syn-collisional volcanic rocks (ca. 238-241 Ma). The Chiang Khong volcanic rocks are characterized by low MgO (1.71-6.72 wt.%) and high Al2O3 (15.03-17.76 wt.%). They are enriched in LILEs and LREEs and depleted in HFSEs, and have 87Sr/86Sr (i) ratios of 0.7050-0.7065, εNd (t) of - 0.32 to - 1.92, zircon εHf (t) and δ18O values of 3.5 to - 11.7 and 4.30-9.80 ‰, respectively. The geochemical data for the volcanic rocks are consistent with an origin from the enriched lithospheric mantle that had been modified by slab-derived fluid and recycled sediments. Based on available geochronological and geochemical evidences, we propose that the Late Triassic Chiang Khong volcanic rocks are equivalent to the contemporaneous volcanic rocks in the Lancangjiang igneous zone in SW China. The formation of these volcanic rocks was possibly related to the upwelling of the asthenospheric mantle during the Late Triassic, shortly after slab detachment, which induced the melting of the metasomatized mantle wedge.

  8. Biogenic halocarbons from coastal oceanic upwelling regions as tropospheric halogen source

    Science.gov (United States)

    Krüger, Kirstin; Fuhlbrügge, Steffen; Hepach, Helmke; Fiehn, Alina; Atlas, Elliot; Quack, Birgit

    2016-04-01

    Halogenated very short lived substances (VSLS) are naturally produced in the ocean and emitted to the atmosphere. Recently, oceanic upwelling regions in the tropical East Atlantic were identified as strong sources of brominated halocarbons to the troposphere. During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL) were investigated above the Peruvian Upwelling for the first time. This study presents novel observations of the three VSLS bromoform, dibromomethane and methyl iodide together with high resolution meteorological measurements and Lagrangian transport modelling. Although relatively low oceanic emissions were observed, except for methyl iodide, surface atmospheric abundances were elevated. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting both as strong barriers for convection and trace gas transport in this region. Significant correlations between observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height were found. We used a simple source-loss estimate to identify the contribution of oceanic emissions to observed atmospheric concentrations which revealed that the observed marine VSLS abundances were dominated by horizontal advection below the trade inversion. The observed VSLS variations can be explained by the low emissions and their accumulation under different MABL and trade inversion conditions. Finally, observations from a second Peruvian Upwelling cruise with R/V SONNE during El Nino in October 2015 will be compared to highlight the role of different El Nino Southern Oscillation conditions. This study confirms the importance of coastal oceanic upwelling and trade wind systems on creating effective transport barriers in the lowermost atmosphere controlling the distribution of VSLS abundances above coastal ocean upwelling

  9. Microbial diversity of a Brazilian coastal region influenced by an upwelling system and anthropogenic activity.

    Directory of Open Access Journals (Sweden)

    Juliano C Cury

    Full Text Available BACKGROUND: Upwelling systems are characterised by an intense primary biomass production in the surface (warmest water after the outcrop of the bottom (coldest water, which is rich in nutrients. Although it is known that the microbial assemblage plays an important role in the food chain of marine systems and that the upwelling systems that occur in southwest Brazil drive the complex dynamics of the food chain, little is known about the microbial composition present in this region. METHODOLOGY/PRINCIPAL FINDINGS: We carried out a molecular survey based on SSU rRNA gene from the three domains of the phylogenetic tree of life present in a tropical upwelling region (Arraial do Cabo, Rio de Janeiro, Brazil. The aim was to analyse the horizontal and vertical variations of the microbial composition in two geographically close areas influenced by anthropogenic activity (sewage disposal/port activity and upwelling phenomena, respectively. A lower estimated diversity of microorganisms of the three domains of the phylogenetic tree of life was found in the water of the area influenced by anthropogenic activity compared to the area influenced by upwelling phenomena. We observed a heterogenic distribution of the relative abundance of taxonomic groups, especially in the Archaea and Eukarya domains. The bacterial community was dominated by Proteobacteria, Cyanobacteria and Bacteroidetes phyla, whereas the microeukaryotic community was dominated by Metazoa, Fungi, Alveolata and Stramenopile. The estimated archaeal diversity was the lowest of the three domains and was dominated by uncharacterised marine Crenarchaeota that were most closely related to Marine Group I. CONCLUSIONS/SIGNIFICANCE: The variety of conditions and the presence of different microbial assemblages indicated that the area of Arraial do Cabo can be used as a model for detailed studies that contemplate the correlation between pollution-indicating parameters and the depletion of microbial

  10. Modification of sea surface temperature by chlorophyll concentration in the Atlantic upwelling systems

    Science.gov (United States)

    Hernandez, O.; Jouanno, J.; Echevin, V.; Aumont, O.

    2017-07-01

    The influence of the chlorophyll on the upper Tropical Atlantic Ocean is investigated with long-term (1979-2012) regional oceanic simulations with 1/4° horizontal resolution based on the NEMO3.6 model. The model solar radiation penetration scheme depends on the chlorophyll concentration. Simulations with time and spatially varying concentrations obtained from satellite ocean color observations are compared with a simulation forced with constant chlorophyll concentration of 0.05 mg m-3, representative of chlorophyll depleted waters. Results indicate that regions of the Tropical Atlantic with chlorophyll concentrations larger than in the reference simulation (i.e., [chl] > 0.05 mg m-3) get warmer at the surface, with the exception of the main upwelling regions where high chlorophyll concentrations are associated with a significant cooling of the sea surface (˜1°C in the Benguela upwelling). The analysis of the model heat balance shows that the biological differential heating causes negative temperature anomalies in subsurface source waters prior to their upwelling at the coast. The shallow mixed-layer in the eastern equatorial and tropical Atlantic favors the persistence of these subsurface anomalies and may explain why the Benguela is particularly sensitive to the biological differential heating. In spite of the presence of high chlorophyll concentrations in the upwelling regions, both the larger amount of shortwave radiation captured in the surface layers and the modifications of the horizontal and vertical advection at the coast are found to play a secondary role in the SST change in the upwelling region.

  11. Quo vadis NW Black Sea benthic ecosystems?

    Science.gov (United States)

    Traian Gomoiu, Marian

    2016-04-01

    / thalasoterapy. Black Sea ecosystem restoration - Certainties and Uncertainties: Pressure on the Danube and other rivers has decreased, chemical discharges have decreased obviously, and yet there appear phenomena of water flowering - "red waters", hypoxia is still present at times and there is mass mortality of fish and other benthic organisms. Why? Signs of recovery should be considered cautiously and uncertainties may be resolved only in a longer time by increasing our scientific efforts. The results of the EU FP7 Project PERSEUS led to the identification of three important issues that should be resolved in order to achieve good environmental status: • Applying an adaptive management to increase the resilience of the ecosystems and to diminish the vulnerability of biodiversity; • Necessity of participative approach by stakeholders; • Identifying and obtaining adequate financial support for new R-D-I projects. Who are the actors in addressing and implementing the actions? • Academic educational and research institutions for adequate working condition; • More specialists trained for taxonomic groups; • Reasonable diversity of coordinating specialists, capable team leaders / satisfactory work packages; • Attracting NGO members towards nature conservation issues; • Resonable stakeholders committed to environmental issues. Studying the results of researches carried out by GeoEcoMar on the Romanian Black Sea coast in recent years, the author concluded that the major problems hampering progress towards a good ecosystem in NW Bent Black Sea are: • lack of diversity in the fields of research, both in theoretical and applied realms; • structural and functional consequences of ecological pressures and the disordered state of the ecosystems in the periods of paroxysmal eutrophication / pollution at the end of the 20th Century; • scarcity of data and knowledge on the Social-Economic System; • high costs of the new marine technology used directly in the sea and

  12. Summer upwelling at the Boknis Eck time series station (1982 to 2012) - a combined glider and wind data analysis

    Science.gov (United States)

    Karstensen, J.; Liblik, T.; Fischer, J.; Bumke, K.; Krahmann, G.

    2014-02-01

    Two consecutive summer upwelling events, each lasting for less than 24 h, where surveyed in high temporal and vertical resolution at the Boknis Eck time series station (BE) in the western Belt Sea (Baltic Sea) in summer 2010 with an autonomous glider. Driven only by moderate offshore winds, both events resulted in strong cooling of surface waters (up to 5 K). Only for the second event, significant irreversible changes in the vertical stratification were observed and the appearance of low oxygen waters at the bottom indicated that the upwelling had an impact on the water column as a whole. A combination of wind and seasurface temperature data revealed that summer (June to September) upwelling at BE occurs for wind directions between 190° to 260° and with hourly averaged wind speed exceeding 4 m s-1. For the period 1982 to 2012 BE experience about 18 days of upwelling favourable wind conditions on average. Large interannual variability exist ranging from only 7.7 days in 2006 to more than 28 days in 1985. Surface (1 m depth) and deep water (below 25 m depth) anomalies of salinity and oxygen at the BE follow extended periods of strong upwelling favourable winds. Although seasurface temperature is good indicator for the existence of summer upwelling, the upwelling intensity does not correlate with the temperature anomaly.

  13. The role of wind-forced coastal upwelling on the thermohaline functioning of the North Aegean Sea

    Science.gov (United States)

    Mamoutos, Ioannis; Zervakis, Vassilis; Tragou, Elina; Karydis, Michael; Frangoulis, Constantin; Kolovoyiannis, Vassilis; Georgopoulos, Dimitris; Psarra, Stella

    2017-10-01

    This work examines the impact of coastal upwelling on the exchanges of a semi-enclosed basin with the open sea. Five oceanographic transects were performed with a cross-shore direction relative to the western coast of Lesvos island of the eastern Aegean Sea, a region where coastal upwelling is regularly observed during the summer Etesian northerly winds. Filaments of highly saline water were observed during upwelling incidents, and were attributed to the enhanced transport of Levantine water from the south due to the baroclinic response to upwelling. All our observations, as well as a 9-year hindcast of the phenomenon revealed that the origin of the upwelled isopycnals usually remained above 40 m depth, and never exceeded the depth of 60 m. On the contrary, the isopycnals hosting the nutricline appear to downwell during upwelling incidents. Our hindcast showed that the secondary geostrophic circulation is comprised both by surface and subsurface longshore currents, which affect the meridional exchanges at the surface and intermediate layers and reduce the residence time of the water in the basin. We conclude that coastal upwelling in a region with longshore temperature and salinity gradients can modify the transport of salt and heat along the coast, possibly affecting the thermohaline functioning of a basin.

  14. Heterotrophic bacterial production, respiration, and growth efficiency associated with upwelling intensity in the Ulleung Basin, East Sea

    Science.gov (United States)

    Kim, Bomina; Kim, Sung-Han; Kwak, Jung Hyun; Kang, Chang-Keun; Lee, Sang Heon; Hyun, Jung-Ho

    2017-09-01

    We investigated bacterial production (BP) and respiration (BR), as well as the physico-chemical properties of the water column, to elucidate the effect of upwelling on heterotrophic bacterial metabolic activities and growth efficiency (BGE) in July 2012 and May 2013 in the Ulleung Basin (UB), East/Japan Sea. The upwelled conditions were characterized by higher chlorophyll-a (Chl-a) concentrations resulting from the upward shift of the nitracline compared to that of the non-upwelled condition. Analyses of the size fractions of Chl-a and pigment composition revealed that large size phytoplankton (> 20 μm), mainly consisting of diatoms, appeared to be the major phytoplankton component. BP and BR were significantly correlated with Chl-a (P 0.05). These results suggest that bacterial metabolic activities are stimulated by the availability of organic resources enhanced by upwelling in the UB. Further statistical analysis showed that the difference in BP and BGE with variations in upwelling intensity were significant (P = 0.018 for BP, P = 0.035 for BGE), but the difference in BR was not significant (P = 0.321). These results suggest that metabolic energy is partitioned more for BP under a strong upwelling condition, i.e. high nutrient and Chl-a conditions. In contrast, the energy generated via respiration was partitioned more for maintaining metabolism rather than for biomass production under weakly or non-upwelled conditions, i.e. stratified and low Chl-a conditions. Overall, our results suggest that any changes in upwelling intensity would significantly affect the carbon cycle associated with the fate of primary production, and the role of the microbial loop in the UB where changes in the intensity and frequency of upwelling associated with climatic changes are in progress.

  15. Hydrogeology of the basalts in the Uruguayan NW

    International Nuclear Information System (INIS)

    Hausman, A.; Fernandez, A.

    1967-01-01

    This work is about the hydrogeological aspects in the NW Uruguayan basaltic area. The results of this research are the main geological, morphological and hydrogeological aspects of the area as well as the characteristics and the color of the basalt and sandstones

  16. Montane pollen from the Tertiary of NW. Borneo

    NARCIS (Netherlands)

    Muller, J.

    1966-01-01

    In NW. Borneo thick series of Tertiary sediments occur which are rich in fossil pollen and spores. The majority of these plant microfossils were derived from the various types of tropical lowland vegetation such as mangrove (Muller, 1964), mixed peat swamp forest and mixed Dipterocarp forest. Some

  17. Hydrogeological map of Kabo Sheet 80NW topographical sheet 1 ...

    African Journals Online (AJOL)

    A hydro geological mapping of the Federal Surveys of Nigeria, Kabo Sheet 80 NW, on scale 1:50,000 were made with areal coverage of 729Km2 on the Crystalline Basement Complex, and the hydrogeoogical maps produced are maps of depth to the water table and maps of configuration peak of dry season and wet ...

  18. African Literature

    OpenAIRE

    Recek, Denis

    2011-01-01

    The topic of this diploma is the formation and shaping of African literature. The first chapter is about the beginning of African literature. It describes oral literature and its transmission into written literature. Written African literature had great problems in becoming a part of world literature because of its diversity of languages and dialects. Christianity and Islam are mentioned as two religions which had a great impact on African literature. Colonialism is broadly described as an es...

  19. Glider observations of enhanced deep water upwelling at a shelf break canyon: A mechanism for cross-slope carbon and nutrient exchange

    Science.gov (United States)

    Porter, M.; Inall, M. E.; Hopkins, J.; Palmer, M. R.; Dale, A. C.; Aleynik, D.; Barth, J. A.; Mahaffey, C.; Smeed, D. A.

    2016-10-01

    Using underwater gliders we have identified canyon driven upwelling across the Celtic Sea shelf-break, in the vicinity of Whittard Canyon. The presence of this upwelling appears to be tied to the direction and strength of the local slope current, which is in itself highly variable. During typical summer time equatorward flow, an unbalanced pressure gradient force and the resulting disruption of geostrophic flow can lead to upwelling along the main axis of two small shelf break canyons. As the slope current reverts to poleward flow, the upwelling stops and the remnants of the upwelled features are mixed into the local shelf water or advected away from the region. The upwelled features are identified by the presence of sub-pycnocline high salinity water on the shelf, and are upwelled from a depth of 300 m on the slope, thus providing a mechanism for the transport of nutrients across the shelf break onto the shelf.

  20. African Anthropologist

    African Journals Online (AJOL)

    African Anthropology is the journal of the Pan African Anthropological Association (PAAA). It provides a forum for African and Africanist anthropologists to publish research reports, articles, book reviews, news items and other useful information. It aims at stimulating the debate of ideas and the development of methods and ...

  1. An annually-resolved palaeoenvironmental archive for the Eastern Boundary North Atlantic upwelling system: Sclerochronology of Glycymeris glycymeris (Bivalvia) shells from the Iberian shelf

    Science.gov (United States)

    Freitas, Pedro; Monteiro, Carlos; Butler, Paul; Reynolds, David; Richardson, Christopher; Gaspar, Miguel; Scourse, James

    2015-04-01

    The seasonally variable western Iberia upwelling system, albeit placed at a crucial climatic boundary position to record high frequency climate events, lacks well-dated high-resolution records of environmental variability. Bivalve shells provide robust high-resolution archives of oceanographic and climatic variability on timescales of decades to millennia. In particular, the North Atlantic Ocean region has recently seen several noteworthy sclerochronological and geochemical reconstructions based on bivalve shells (mainly Arctica islandica) of high frequency oceanographic and climatic conditions during the last millennium. However, due to the absence of Arctica islandica and similarly long-lived bivalves, sclerochronological palaeoenvironmental studies of southern European coastal shelf seas are scarce. In particular, none of these studies focus on reconstructing the variability of an eastern boundary upwelling system. The relatively long-lived bivalve (>100 years) Glycymeris glycymeris occurs in European and North West African coastal shelf seas and provides a valid annually resolved archive of environmental conditions during growth. Annual growth increment width series from living G. glycymeris shells, collected in 2014 on the western Iberian continental shelf (ca. 35 m water depth), were used to construct a statistically robust, ca. 70-year long absolutely-dated chronology. Sub-annually resolved (11 to 22 samples per year) oxygen stable isotope (δ18Oshell) data covering three years of shell growth, together with the direct evaluation of the time of growth mark deposition in shells collected during the autumn and winter months, were used to constrain the season of growth and to evaluate the seasonal bias of the sea-surface temperature signal preserved in the δ18Oshelldata. The growth increment width and δ18Oshell series, once robustly calibrated against modelled and instrumental oceanographic and climatic series, potentially provide novel insights into the

  2. Variability in the Benguela Current upwelling system over the past 70,000 years

    Science.gov (United States)

    Summerhayes, C. P.; Kroon, D.; Rosell-Melé, A.; Jordan, R. W.; Schrader, H.-J.; Hearn, R.; Villanueva, J.; Grimalt, J. O.; Eglinton, G.

    This study was designed to see if the intensity and location of upwelling in the Benguela Current Upwelling System off Namibia changed significantly during the last 70,000 years. Most of the analytical work focused on geochemical, micropalaeontological and stable isotopic analyses of a 6.5m long combined pilot and piston core, PGPC12, from 1017m on the continental slope close to Walvis Bay. The slope sediments are rich in organic matter. Most of it is thought to represent deposition beneath a productive shelf edge upwelling system, but some is supplied by downslope nearbottom flow of material probably resuspended on the outer continental shelf. Temporal changes in upwelling intensity as represented by fluctuations in the accumulation of organic matter do not show the simple ‘classical’ pattern of less upwelling and lower productivity in interglacials and more upwelling and higher productivity in glacials, but instead show a pattern of higher frequency fluctuations. The broad changes in organic carbon accumulation reach maxima at times when the earth-sun distance was greatest, indicating that this accumulation responded to changes in the precession index; at these times monsoons would have been weakest and Trade Winds strongest. Maximum accumulation of organic matter on the slope occurred in the last interstadial (isotope stage 3), and coincided with coldest sea surface temperatures as recorded by alkenone data (U k37), and by nannofossil assemblages. It is attributed largely to increased productivity in situ, rather than the lateral supply of material eroded from older organic rich deposits exposed by the lowering of sealevel at that time. The enhanced productivity is attributed to a strengthening of upwelling-favourable winds in this area in response to the minimal solar insolation typical of this period. Diatoms generally are not abundant in these sediments, so appear to be unreliable indicators of productivity over the continental slope. When sealevel was

  3. Modelling shelf-ocean exchange and its biogeochemical consequences in coastal upwelling systems

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar

    margin bathymetry, and 3) what processes determine the observed variability of total organic carbon (TOC) content in shelf sediments underlying the upwelling system, with implications for the formation of petroleum source rocks. Here, a numerical ocean modeling approach is used in this thesis to explore...... processes and the development of anoxia/euxinia under the present day or past geological conditions. Thirdly and last, processes controlling distribution of total organic carbon (TOC) content in sediments across the continental margin is evaluated by application of the model to the Benguela upwelling system....... In the model, biological primary production and shelf bottom-water anoxia result in enhanced sedimentary TOC concentrations on the mid shelf and upper slope. The simulated TOCs implicate that bottom lateral transport only has a significant effect on increasing the deposition of the organic carbon on the mid...

  4. Changes in upwelling and surface productivity in the Eastern Pacific during Terminations I and II

    Science.gov (United States)

    Erdem, Z.; De Bar, M.; Stolwijk, D.; Schneider, R. R.; S Sinninghe Damsté, J.; Schouten, S.

    2017-12-01

    The Eastern Pacific coastal system is characterized by intense upwelling and consequently by an enhanced surface primary productivity. Combination of this high organic matter flux with sluggish bottom water ventilation results in one of the most pronounced oxygen minimum zones reaching from offshore California in the North to offshore Chile in the South. As a result of this process, the region is particularly interesting in view of nutrient and carbon cycling as well as ecosystem dynamics. The dynamics of the upwelling and oxygen concentrations are closely related to climatic conditions. Therefore, paleo-reconstructions of different settings are crucial in order to improve our understanding of the response of these nutrient-rich, oxygen-deficient, environments in relation to the recent global ocean warming, acidification and deoxygenation. In this study, we present downcore results from three different sites in the Eastern Pacific: offshore California (IODP site 1012), Peru (M77/2-52-2) and Chile (IODP site 1234). We applied different biomarkers as proxies to decipher changes in phytoplankton community composition, including the upwelling index based on long chain diols, and other common productivity indicators such as bulk organic carbon, carbonate and biogenic opal. In addition, application of carbon and nitrogen isotope ratios of total organic carbon and benthic foraminifera complement our multiproxy approach. Herewith we aim to compare at least two glacial-interglacial transitions with different magnitudes of deglacial warming along the Eastern Pacific upwelling systems at different latitudes. The data presented will cover the last 160 ka BP offshore California and Chile, and 30 ka BP offshore Peru enabling comparison between glacial Terminations I and II.

  5. Upwelling Dynamics off Monterey Bay: Heat Flux and Temperature Variability, and their Sensitivities

    Science.gov (United States)

    2010-05-01

    WHOI Slocum gliders . The Princeton Glider Coordinated Control System (GCCS) was used for path planning to steer a fleet of underwater gliders to a...energy decayed and led to the development of mesoscale features within a warming upper thermocline. Shulman (2009) researched the impact of glider ...such as undersea gliders to study ocean processes associated with the upwelling of cold, deep water along the Central California Coast  Use the

  6. Contrasting biogeochemical responses of ENSO induced upwelling variability in the Humboldt Current System

    Science.gov (United States)

    Franco, Ana C.; Gruber, Nicolas; Münnich, Matthias

    2017-04-01

    The Humboldt Current System (HCS) is one of the most productive ecosystems in the world. This high productivity is supported by a large input of nutrients from the subsurface layers to the surface due to year-round upwelling. However, upwelling also supplies waters with low pH and low aragonite saturation state potentially affecting many organisms, especially those that calcify. The influence, extent and source of upwelled water vary substantially on interannual timescales in association with the El Niño/Southern Oscillation (ENSO) phenomenon, generating natural contrasting responses on the biogeochemistry of this system. Here we analyze these responses using an eddy resolving, basin-scale ocean model that covers the whole Pacific Ocean with high resolution (4 km) on the west coast of South America. We performed a simulation of the last 30 years (hindcast simulation) that allows us to investigate the influence of at least eight El Niño episodes and eight La Niña episodes on productivity variations and changes in oxygen concentration and aragonite saturation state. An absolute change in surface omega aragonite of almost 2 units, as well as an absolute change of the aragonite saturation depth of 200 m result from the change of an El Niño phase to a La Niña phase. This variability is on the same order of magnitude as the projected change in the aragonite saturation state in a centennial timescale. During La Niña events, a lower aragonite saturation state values and reduced oxygen concentration in the surface layer are a direct consequence of enhanced upwelling and increased net primary productivity. The opposite is true during El Niño events, where high values of omega aragonite occur in concordance with extraordinarily low net primary productivity values.

  7. Enhanced incubation success for kokanee spawning in groundwater upwelling sites in a small Idaho stream

    Science.gov (United States)

    James W. Garrett; David H. Bennett; Frank O. Frost; Russell F. Thurow

    1998-01-01

    Kokanee (Oncorhynchus nerka lacustrine sockeye salmon) spawned in groundwater upwelling in the North Fork of the Payette River, Idaho. Intragravel water temperatures in groundwater-influenced redds exceeded surface flow water temperature by 2.4–2.6°C. In redds without groundwater influence, intragravel and water column temperatures did not differ by more than 0.2°C....

  8. Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

    Science.gov (United States)

    Hepach, Helmke; Quack, Birgit; Tegtmeier, Susann; Engel, Anja; Bracher, Astrid; Fuhlbrügge, Steffen; Galgani, Luisa; Atlas, Elliot L.; Lampel, Johannes; Frieß, Udo; Krüger, Kirstin

    2016-09-01

    Halocarbons are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling zone obtained during the M91 cruise onboard the research vessel METEOR in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3) and dibromomethane (CH2Br2) correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group is a likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I) of up to 35.4 pmol L-1, chloroiodomethane (CH2ClI) of up to 58.1 pmol L-1 and diiodomethane (CH2I2) of up to 32.4 pmol L-1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM) components measured in the surface water. Our results suggest a biological source of these compounds as a significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt), CH2ClI (up to 2.5 ppt) and CH2I2 (3.3 ppt) above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. During the first part of the cruise, the enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels, while this contribution was considerably smaller during the second part.

  9. Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

    Directory of Open Access Journals (Sweden)

    H. Hepach

    2016-09-01

    Full Text Available Halocarbons are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling zone obtained during the M91 cruise onboard the research vessel METEOR in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3 and dibromomethane (CH2Br2 correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group is a likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I of up to 35.4 pmol L−1, chloroiodomethane (CH2ClI of up to 58.1 pmol L−1 and diiodomethane (CH2I2 of up to 32.4 pmol L−1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM components measured in the surface water. Our results suggest a biological source of these compounds as a significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt, CH2ClI (up to 2.5 ppt and CH2I2 (3.3 ppt above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. During the first part of the cruise, the enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels, while this contribution was considerably smaller during the second part.

  10. Nutrients, oxygen and biogeochemical processes in the Humboldt upwelling current system off Peru

    Directory of Open Access Journals (Sweden)

    Michelle I. Graco

    2013-04-01

    Full Text Available The upwelling system of the Humboldt Current, is considered among the most productive systems in the world, extending along the eastern South Pacific off Chile and Peru. In particular the coastal waters off Peru attracted considerable interest for being among the most fertile and productive the world, highlighting fisheries, such as anchovy, which represent one of the pillars of the economy of Peru.

  11. Influence of monsoon upwelling on the planktonic foraminifera off Oman during Late Quaternary

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    , these sediments provide an integrated information of the upwelling process and Asian monsoon strengths over geological time. The monsoon system is one of the Earth's most dynamic features, which interacts with global atmospheric circulation that controls... the heat budget in the Arabian Sea. Hence changes in the monsoon system may play an essential role on global climate. The southwest (SW) monsoon system in the Arabian Sea exerts a strong influence upon the climatic conditions in south and southeast...

  12. REGIONAL AIR-SEA INTERACTION (RASI) GAP WIND AND COASTAL UPWELLING EVENTS CLIMATOLOGY GULF OF PANAMA, PANAMA V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Regional Air-Sea Interactions (RASI) Gap Wind and Coastal Upwelling Events Climatology datasets were created using an automated intelligent algorithm which...

  13. REGIONAL AIR-SEA INTERACTION (RASI) GAP WIND AND COASTAL UPWELLING EVENTS CLIMATOLOGY GULF OF TEHUANTEPEC, MEXICO V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Regional Air-Sea Interactions (RASI) Gap Wind and Coastal Upwelling Events Climatology datasets were created using an automated intelligent algorithm which...

  14. REGIONAL AIR-SEA INTERACTION (RASI) GAP WIND AND COASTAL UPWELLING EVENTS CLIMATOLOGY GULF OF PAPAGAYO, COSTA RICA V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Regional Air-Sea Interactions (RASI) Gap Wind and Coastal Upwelling Events Climatology datasets were created using an automated intelligent algorithm which...

  15. REGIONAL AIR-SEA INTERACTION (RASI) GAP WIND AND COASTAL UPWELLING EVENTS CLIMATOLOGY GULF OF PAPAGAYO, COSTA RICA V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Regional Air-Sea Interactions (RASI) Gap Wind and Coastal Upwelling Events Climatology Gulf of Papagayo, Costa Rica dataset was created using an automated...

  16. Wind-driven coastal upwelling along the western boundary of the Bay of Bengal during the southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Shenoi, S.S.C.; Gouveia, A; Michael, G.S.; Sundar, D.; Nampoothiri, G.

    . by local winds, in a fashion similar to that observed along eastern boundaries. Below the upwelling band there were often signatures of downwelling, suggestive of an undercurrent. There were no indications of a large-scale remotely forced western boundary...

  17. Influence of upwelling induced near shore hypoxia on the Alappuzha mud banks, South West Coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    GireeshKumar, T.R.; Mathew, D.; Pratihary, A.K.; Naik, H.; Narvekar, K.U.; Araujo, J.; Balachandran, K.K.; Muraleedharan, K.R.; Thorat, B.R.; Nair, M.; Naqvi, S.W.A.

    The results of the first time-series measurements spanning 18-weeks (22 April to 20 September 2014) from a coastal environment (Alappuzha, southwest India), where two process of upwelling and mud banks are concurrent during summer monsoon...

  18. Resource partitioning within major bottom fish species in a highly productive upwelling ecosystem

    Science.gov (United States)

    Abdellaoui, Souad; El Halouani, Hassan; Tai, Imane; Masski, Hicham

    2017-09-01

    The Saharan Bank (21-26°N) is a wide subtropical continental shelf and a highly productive upwelling ecosystem. The bottom communities are dominated by octopus and sparid fish, which are the main targets of bottom-trawl fishing fleets. To investigate resource partitioning within the bottom fish community, adult fish from 14 of the most abundant species were investigated for stomach content analysis. Samples were collected during two periods: October 2003 and May 2007. The diet of the analysed species showed more variation between periods than between size classes, suggesting that temporal or spatial variability in prey availability appears to play a significant role in their diet. Multivariate analysis and subsequent clustering led to a grouping of the species within five trophic guilds. Two species were fish feeders, and the others mainly fed on benthic invertebrates, where epibenthic crustaceans, lamellibranchs and fish were the most important groups in defining trophic guilds. We found that the studied species had a high rate of overlapping spatial distributions and overlapping trophic niches. In this highly productive upwelling ecosystem, where food resources may not be a limiting factor, inter-specific competition did not appear to be an important factor in structuring bottom fish communities. For the species that showed differences in the proportions of prey categories in comparison with other ecosystems, the rise of the proportion of epibenthic crustaceans in their diet was a common feature; a possible consequence of the benthic productivity of this highly productive upwelling ecosystem.

  19. Contrasting energy allocation strategies of two sympatric Merluccius species in an upwelling system.

    Science.gov (United States)

    Rey, J; Fernandez-Peralta, L; Quintanilla, L F; Hidalgo, M; Presas, C; Salmeron, F; Puerto, M A

    2015-03-01

    This study investigated the somatic growth and energy allocation strategy of two sympatric hake species (Merluccius polli and Merluccius senegalensis), coexisting under the strong influence of the Mauritanian upwelling. The results revealed that ontogeny, bathymetry, geography and reproduction shaped the differences found between the condition dynamics of the two species. Aside from species-specific differences, individuals were observed in better condition in the northernmost area (more influenced by the permanent upwelling) and in the deepest waters, probably the most favourable habitat for Merluccius spp. Both species also displayed contrasting trade-offs in energy allocation probably due to the dissimilarity of their habitats, which favours the existence of divergent adaptive strategies in response to different ontogenic requirements. It was hypothesized that M. polli invests in mass and energy reserves while sacrificing growth, as larger sizes may not provide an ecological advantage in a deeper and more stable environment. Moreover, M. senegalensis capitalizes on a steady growth without major disruptions, enabling earlier spawning at the expense of a lower somatic mass, which is fitting to a less stable shallower environment. This study sheds new light on differences in the biological traits and life strategies of Merluccius spp., which permit their overlap in a complex upwelling system and may contribute to the long-lasting scientific-based management of these species. © 2015 The Fisheries Society of the British Isles.

  20. Macro-Scale Patterns in Upwelling/Downwelling Activity at North American West Coast.

    Directory of Open Access Journals (Sweden)

    Romeo Saldívar-Lucio

    Full Text Available The seasonal and interannual variability of vertical transport (upwelling/downwelling has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling activity along the North American west coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series analysis. We found that spatial co-variation of seawater vertical movements present three dominant low-frequency signals in the range of 33, 19 and 11 years, resembling periodicities of: atmospheric circulation, nodal moon tides and solar activity. Those periodicities might be related to the variability of vertical transport through their influence on dominant wind patterns, the position/intensity of pressure centers and the strength of atmospheric circulation cells (wind stress. The low-frequency signals identified in upwelling/downwelling are coherent with temporal patterns previously reported at the study region: sea surface temperature along the Pacific coast of North America, catch fluctuations of anchovy Engraulis mordax and sardine Sardinops sagax, the Pacific Decadal Oscillation, changes in abundance and distribution of salmon populations, and variations in the position and intensity of the Aleutian low. Since the vertical transport is an oceanographic process with strong biological relevance, the recognition of their spatio-temporal patterns might allow for some reasonable forecasting capacity, potentially useful for marine resources management of the region.

  1. Future changes in coastal upwelling ecosystems with global warming: The case of the California Current System.

    Science.gov (United States)

    Xiu, Peng; Chai, Fei; Curchitser, Enrique N; Castruccio, Frederic S

    2018-02-12

    Coastal upwelling ecosystems are among the most productive ecosystems in the world, meaning that their response to climate change is of critical importance. Our understanding of climate change impacts on marine ecosystems is largely limited to the open ocean, mainly because coastal upwelling is poorly reproduced by current earth system models. Here, a high-resolution model is used to examine the response of nutrients and plankton dynamics to future climate change in the California Current System (CCS). The results show increased upwelling intensity associated with stronger alongshore winds in the coastal region, and enhanced upper-ocean stratification in both the CCS and open ocean. Warming of the open ocean forces isotherms downwards, where they make contact with water masses with higher nutrient concentrations, thereby enhancing the nutrient flux to the deep source waters of the CCS. Increased winds and eddy activity further facilitate upward nutrient transport to the euphotic zone. However, the plankton community exhibits a complex and nonlinear response to increased nutrient input, as the food web dynamics tend to interact differently. This analysis highlights the difficulty in understanding how the marine ecosystem responds to a future warming climate, given to range of relevant processes operating at different scales.

  2. Influence of upwelling saline groundwater on iron and manganese cycling in the Rio Grande floodplain aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, Matthew F. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States)], E-mail: matthew.f.kirk@gmail.com; Crossey, Laura J. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States); Takacs-Vesbach, Cristina [Department of Biology, University of New Mexico, Albuquerque, NM 87131 (United States); Newell, Dennis L. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States); Bowman, Robert S. [Department of Earth and Environmental Science, New Mexico Tech, Socorro, NM 87801 (United States)

    2009-03-15

    Salinity contributions from upwelling groundwater significantly degrade water quality in the Rio Grande, a major source of water for the southwestern USA. This study considers the influence of this upwelling water on the geochemistry and microbiology of the Rio Grande floodplain alluvial aquifer. The composition of surface water, groundwater, and floodplain sediment samples collected from three transects in the Socorro Basin was examined. Terminal-restriction fragment length polymorphism (T-RFLP) was also used to examine microbial biomass samples. The distribution of salinity in the floodplain groundwater largely reflects the configuration of local groundwater flow and mixing of two major water sources, deeply-sourced saline groundwater and river water. Microbial populations in the shallow aquifer consume O{sub 2} and NO{sub 3}{sup -} and serve to redistribute metal oxides from the saturated zone to locations of groundwater discharge at the surface and possibly near the water table. The upwelling saline groundwater affects floodplain microbial processes by transporting reduced metals and organic electron donors to the alluvial aquifer system. This enhances metal reduction in the saturated zone and ultimately metal oxidation at or near the surface. Geochemical modeling suggests that mixing of the saline groundwater with more dilute water in the floodplain creates conditions more favorable for metal oxidation to occur and thereby influences the distribution of metal oxides.

  3. Lagrangian studies of phytoplankton growth and grazing relationships in a coastal upwelling ecosystem off Southern California

    Science.gov (United States)

    Landry, Michael R.; Ohman, Mark D.; Goericke, Ralf; Stukel, Michael R.; Tsyrklevich, Kate

    2009-12-01

    Experimental studies of phytoplankton growth and grazing processes were conducted in the coastal upwelling system off Point Conception, California to test the hypothesis that phytoplankton growth and grazing losses determine, to first order, the local dynamics of phytoplankton in the upwelling circulation. Eight experiments of 3-5 days each were conducted over the course of two cruises in May-June 2006 and April 2007 following the trajectories of satellite-tracked drifters. Rates of phytoplankton growth and microzooplankton grazing were determined by daily in situ dilution incubations at 8 depths spanning the euphotic zone. Mesozooplankton grazing was assessed by gut fluorescence analysis of animals collected from net tows through the euphotic zone. We compared directly the net rates of change observed for the ambient phytoplankton community to the net growth rates predicted from experimental determinations of each process rate. The resulting relationship accounted for 91% of the variability observed, providing strong support for the growth-grazing hypothesis. In addition, grazing by mesozooplankton was unexpectedly high and variable, driving a substantial positive to negative shift in phytoplankton net rate of change between years despite comparable environmental conditions and similar high growth rates and suggesting strong top-down control potential. The demonstrated agreement between net ambient and experimental community changes is an important point of validation for using field data to parameterize models. Data sets of this type may provide an important source of new information and rate constraints for developing better coupled biological-physical models of upwelling system dynamics.

  4. African Journals Online: African Studies

    African Journals Online (AJOL)

    Items 51 - 56 of 56 ... Research Review of the Institute of African Studies. Please note: As of 2013 the Research Review of the Institute of African Studies is now publishing under the title Contemporary Journal of African Studies. You can view the CJAS pages on AJOL here: http://www.ajol.info/index.php/contjas/index.

  5. Variability of Phytoplankton Size Structure in Response to Changes in Coastal Upwelling Intensity in the Southwestern East Sea

    Science.gov (United States)

    Shin, Jung-Wook; Park, Jinku; Choi, Jang-Geun; Jo, Young-Heon; Kang, Jae Joong; Joo, HuiTae; Lee, Sang Heon

    2017-12-01

    The aim of this study was to examine the size structure of phytoplankton under varying coastal upwelling intensities and to determine the resulting primary productivity in the southwestern East Sea. Samples of phytoplankton assemblages were collected on five occasions from the Hupo Bank, off the east coast of Korea, during 2012-2013. Because two major surface currents have a large effect on water mass transport in this region, we first performed a Backward Particle Tracking Experiment (BPTE) to determine the coastal sea from which the collected samples originated according to advection time of BPTE particles, following which we used upwelling age (UA) to determine the intensity of coastal upwelling in the region of origin for each sample. Only samples that were affected by coastal upwelling in the region of origin were included in subsequent analyses. We found that as UA increased, there was a decreasing trend in the concentration of picophytoplankton, and increasing trends in the concentration of nanophytoplankton and microphytoplankton. We also examined the relationship between the size structure of phytoplankton and primary productivity in the Ulleung Basin (UB), which has experienced significant variation over the past decade. We found that primary productivity in UB was closely related to the strength of the southerly wind, which is the most important mechanism for coastal upwelling in the southwestern East Sea. Thus, the size structure of phytoplankton is determined by the intensity of coastal upwelling, which is regulated by the southerly wind, and makes an important contribution to primary productivity.

  6. Summer upwelling at the Boknis Eck time-series station (1982 to 2012) - a combined glider and wind data analysis

    Science.gov (United States)

    Karstensen, J.; Liblik, T.; Fischer, J.; Bumke, K.; Krahmann, G.

    2014-07-01

    Two consecutive summer upwelling events, each lasting for less than 24 h, were surveyed in high temporal and vertical resolution close to the Boknis Eck time-series station (BE) in the western Belt Sea (Baltic Sea) in summer 2010 with an autonomous glider. Driven only by moderate offshore winds both events resulted in more than 5 K cooling of surface waters, while only for the second event were significant irreversible changes in the vertical stratification observed. Generalizing the glider survey observations with hourly wind data from nearby meteorological stations, it is found that upwelling in the BE area occurs for wind directions between 190 to 260° and wind speed exceeding 4 m s-1. Based on these thresholds the wind-induced summer (June to September) upwelling conditions in the BE area for the period 1982 to 2012 are reconstructed. On average about 18 days of upwelling favourable wind conditions are found for the four summer months, with significant interannual variability ranging from 7.7 days (2006) to more than 28 days (1985). By aligning upwelling favourable wind conditions with the monthly BE surveys it is found that extreme anomalies in BE surveys follow extended periods of upwelling favourable winds.

  7. Upwelling di Laut Banda dan Pesisir Selatan Jawa serta Hubungannya dengan ENSO dan IOD

    Directory of Open Access Journals (Sweden)

    Herlina Ika Ratnawati

    2017-04-01

    Full Text Available Upwelling events analysis in southern coast of Java and Banda sea were conducted. The events were identified by using satellite data i.e. wind surface, Sea Surface Temperature (SST and ocean color during period of 14 years (2002-2016 which calculated by Ekman pumping and Ekman transport. It’s found that Ekman pumping velocity in Banda Sea reached a maximum in June-July-August (JJA by approximately 3,65x10 -6 . Comparing with Ekman transport, Ekman pumping makes an even greater contribution to the local upwelling in Banda Sea. Ekman pumping velocity in southern coast of Java reached a maximum in June-July-August (JJA by approximately 4,9x10 -1 ms . Ekman pumping and Ekman transport makes an equal contribution to coastal upwelling in southern coast of Java. That’s related to highest clorophyll-a concentration apperars in JJA periode. Partial correlation analysis then was applied to identify a correlation between chlorophyll-a concentration and interannual climate variabilities such as ENSO and IOD. Partial Correlation between chlorophyll-a and Nino 3.4 and DMI-Dipole Mode Index (controlled in Banda Sea is 0.18, and 0.05 in southercoast of Java. It’s represent ENSO (Elnino Southern Oscilation has higher influences to Banda Sea than southern coast of Java. Partial correlation between chlorophyll-a and DMI and Nino 3.4 (controlled is 0.55 in southern coast of Java, and 0.25 in Banda Sea. Its represent IOD (Indian Ocean Dipole has higher influences to southern coast of Java than Banda Sea. Upwelling in Banda sea and along southern coast of Java dominantly occurs in southeast monsoon as a responds to regional wind driven motion associated with the monsoon climate. Various condition of chlorophyll-a booming also occured according to combination of ENSO and IOD events. -6 -1 ms Keywords: upwelling, Banda sea, southern coast of Java, Ekman transport, Ekman pumping, IOD, ENSO

  8. Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system.

    Science.gov (United States)

    Ohde, Thomas; Dadou, Isabelle

    2018-01-01

    We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS) for the 2002-2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area). The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone, increased mass

  9. Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system.

    Directory of Open Access Journals (Sweden)

    Thomas Ohde

    Full Text Available We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS for the 2002-2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area. The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone

  10. Assessing the applicability of organic SST proxies in an upwelling region (Arabian Sea)

    Science.gov (United States)

    Lattaud, J.; van Erk, M. R.; Reichart, G. J.; Schulz, H.; S Sinninghe Damsté, J.; Schouten, S.

    2017-12-01

    Multiple organic proxies have the potential to reconstruct sea surface temperature (SST), but their behaviour is not completely understood within upwelling areas. This holds in particular for the recently developed Long chain Diol Index1 (LDI), based on the ratio of 1,15-diols over 1,13-diols, both likely produced by Eustigmatophytes. We tested the applicability of the LDI by comparing it to the more established temperature proxies TEX86 and Uk¢37 in a sediment core (spanning the last 76 ky) from the northern Arabian Sea and in surface sediments (Pakistan margin). In the surface sediments, Uk¢37- and LDI-SSTs agree well with annual mean SST, but the TEX86-SST substantially overestimates SST. A better agreement is observed, when the 0-200 m TEX86 calibration is used, suggesting TEX86 reflects subsurface temperatures. The results from the sediment core reveal that the SST records differ in absolute reconstructed temperature and show different patterns. TEX86 subsurface temperatures show a continuous increase toward the Holocene and no stadial/interstadial differences, while the LDI-SST is constant around 26°C with the exception of some short-term cooling events during periods of intensified upwelling. The Uk¢37-SST varies between 22 and 26°C and follows the global δ18Obenthic foram curve and thus is representing mean annual SST in this region3. During stadials, the reduced monsoon and low upwelling intensity resulted in warming of the subsurface waters2, as indicated by higher TEX86 temperatures, while global cooling led to colder surface waters as reflected in lower Uk¢37-SSTs, thus reducing the thermal gradient in the water column2. During the interstadials, which are periods of strong upwelling3, there is a high proportion of 1,14-diols (>40%). This probably disturbs the LDI-SST signal because the diatoms that produce the 1,14-diols are also generating small amounts of the 1,13-diols4. This suggests that care has to be taken in applying the LDI in upwelling

  11. A study on the seasonal variability of upwelling and its effects on physical parameters in Arabian Sea

    Science.gov (United States)

    Shukla, Rohit Kumar; Shaji, Chithra; Ojha, Satya P.; Kumar, Pankaj

    2017-04-01

    The upwelling in Arabian Sea is an important phenomenon, mainly occurring along the southwest coast of India during summer monsoon, which increases the biological productivity in the region. The south west coast of Arabian sea region accounts for about 53% of fish yield of the total fish production in Arabian Sea, thus it is imperative to study and understand the process of upwelling in this region. To study the upwelling features in southwest coast of India, monthly Ekman mass transport is estimated using analyzed wind and derived products from Oceansat-II scatterometer data. Seasonal variability of Ekman mass transport has been analyzed to study the occurrences of coastal upwelling in this region. Results show prominent region of upwelling along southwest coast of India is between 7° and 15° N. Transport estimate demonstrate that the strong offshore Ekman mass transport, as high as -2000 kg/m/s, was observed during summer monsoon months due to favorable wind conditions. Very weak offshore transport, as low as -200 kg/m/s, was observed during pre-monsoon months as winds were weak and spatially variable. Moderate offshore transport, up to -750 kg/m/s, was observed during winter monsoon months. The upwelling associated ocean surface features such as Sea-surface temperature (SST, from AVHRR), chlorophyll concentration (AQUA-MODIS), wind stress curl derived from Oceansat-II and sea surface salinity (SSS, from Aquarius) were examined to demonstrate the spatial and temporal evolution of upwelling in this region. With the advancement of the summer monsoon and upwelling, the monthly mean SST range reaches up to 26-27°C (August - September) from about 29-30°C (April - May). The monthly mean Chlorophyll concentration reaches up to 25-30 mg/m3 (August-September) from 0.1-0.2 mg/m3 (January-February). The monthly SSS which was observed to be about 34 psu (December 2102- January 2013) reaches to 36.5 psu (August-September). Analysis of SST from different sources suggests

  12. Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an ENSO event

    Science.gov (United States)

    Loick-Wilde, Natalie; Bombar, Deniz; Doan, Hai Nhu; Nguyen, Lam Ngoc; Nguyen-Thi, Anh Mai; Voss, Maren; Dippner, Joachim W.

    2017-04-01

    Investigating microplankton biomass and diversity under different climatological conditions is key to the understanding of cascading effects of climate change on nutrient cycles and biological productivity. Here we have used data collected during two contrasting summers along the coast of Viet Nam to show how climatological-driven changes can have a significant influence on the distribution of microplankton communities and their biomass via its impact on nutrient concentrations in the water column. The first summer in July 2003 followed a weak El-Nino Southern Oscillation (ENSO) event and was characterized by weak coastal upwelling, in the second summer during July 2004, upwelling was normal. Very low silicate (SiO4) concentrations and SiO4:DIN ratios characterized the source water mass for upwelling in July 2004, and dynamic SiO4 to dissolved inorganic nitrogen ratios (SiO4:DIN) mainly below the Redfield-Brzezinski ratio and DIN to phosphate ratios (DIN:PO43-) below the Redfield ratio were a common feature off Viet Nam. Much higher particle concentrations and PSi/PC ratios during normal upwelling revealed major changes in the microplankton community structure among summers. Small dinoflagellates (10-20 μm) prevailed ubiquitously during reduced upwelling. During normal upwelling, the diatom Rhizosolenia sp. dominated the cell-carbon biomass in the silicate poor upwelling waters. Trichodesmium erythraeum dominated in the Mekong-influenced and nutrient depleted offshore waters, where it co-occurred with Rhizosolenia sp. Both species were directly associated with the much higher primary production (PP) and N2 fixation rates that were quantified in earlier studies, as well as with much higher diversities at these offshore sites. Along the coast, the correlation between Rhizosolenia sp. and PP rates was less clear and the factors regulating the biomass of Rhizosolenia sp. in the upwelling waters are discussed. The very low silicate concentrations in the source water

  13. Modern sedimentation in the Cabo Frio upwelling system, Southeastern Brazilian shelf

    Directory of Open Access Journals (Sweden)

    Michel M. de Mahiques

    2005-09-01

    Full Text Available The analyses of Uk'37 paleotemperatures and sedimentological parameters in box cores from the Cabo Frio upwelling zone, southeastern Brazil, were used to understand the modern sedimentation as well as to evaluate the role played by the upwelling process in the sedimentary patterns. Three box-cores located closer to the upwelling area show a general trend of cooling waters taking place in the last 700 years. Since the present upwelling is dependent on local and remote wind regime, a phase of dominating NE winds favors a more effective upward transport of the cold thermocline level South Atlantic CentralWater towards the coast. The intensification in the upwelling regime for the last ca. 700 years can be associated with the strengthening of the NE winds off the area and a possible increase of the Brazil Current mesoscale activity. Nevertheless, the lack of significant correlation of the paleotemperatures and most of sedimentological parameters indicate that upwelling is not the only sedimentation mechanism in the area. Also, the comparison of sedimentological parameters reveals that eventual temporal changes are superimposed by the geographical variability. Sedimentation rates vary from 0.26 mm.yr-1 to 0.66 mm.yr-1.As análises de Uk'37 paleotemperaturas e de parâmetros sedimentológicos em amostras de box-core da zona de ressurgência de Cabo Frio, sudeste do Brasil, foram usadas para compreender os processos de sedimentação moderna na área, bem como avaliar o papel desempenhado pela ressurgência no estabelecimento dos padrões sedimentológicos principais. Como observado em três box-cores localizados nas proximidades da área de ressurgência, é possível verificar uma tendência geral de resfriamento das águas nos últimos 700 anos (idade calibrada. Uma vez que o processo de ressurgência é dependente do regime de ventos local e remoto, uma fase de ventos predominantes de NE favorece um deslocamento mais efetivo das águas frias da

  14. Discriminating the biophysical impacts of coastal upwelling and mud banks along the southwest coast of India

    Science.gov (United States)

    Karnan, C.; Jyothibabu, R.; Arunpandi, N.; Jagadeesan, L.; Muraleedharan, K. R.; Pratihari, A. K.; Balachandran, K. K.; Naqvi, S. W. A.

    2017-08-01

    Coastal upwelling and mud banks are two oceanographic processes concurrently operating along certain stretches of the southwest (Kerala) coast of India during the Southwest Monsoon period (June-September), facilitating significant enhancement in plankton biomass. Mud banks have scientific and societal attention from time immemorial, predominantly due to the large fisheries associated with them. In this paper, for the first time, the specific biophysical roles of these oceanographic processes have been discriminated, based on a focused 18 weekly/fortnightly time-series study (April to September 2014) in a mud bank-upwelling area (off Alappuzha, southwest coast of India). In conjunction with standard hydrographical and satellite remote sensing data, we utilised a FlowCAM to track the biophysical linkage in terms of plankton composition abundance and size structure at three locations (M1, M2 and M3) in the study area. During the Pre-Southwest Monsoon (April-May), the entire study area was warmer with low nitrate concentration in the surface waters, which caused lower biomass of autotrophs compared to the Southwest Monsoon (June-September). By the onset of the Southwest Monsoon (June), drastic hydrographical transformations took place in the study domain due to the Coastal upwelling, reflected as the surfacing of significantly cool, high nutrient and hypoxic waters. Concurrently, mud bank formed at location M2 due to the presence of relatively high-suspended sediments in the region, creating a localised calm environment conducive for fishing activities. In response to the hydrographical transformations in the entire study area during the Southwest Monsoon, the autotrophic plankton biomass and size structure experienced significant change. The micro-autotrophs biomass that was low during the Pre-Southwest Monsoon (av. 0.33 ± 0.2 mgC L- 1 at surface and av. 0.07 ± 0.04 mgC L- 1 at subsurface) noticeably increased during the Southwest Monsoon (av. 1.6 ± 0.4 mgC L- 1 at

  15. Glider observations of enhanced deep water upwelling at a shelf break canyon: a mechanism for cross-slope carbon and nutrient exchange

    OpenAIRE

    Porter, M.; Inall, M.E.; Hopkins, J.; Palmer, M.R.; Dale, A.C.; Aleynik, D.; Barth, J.A.; Mahaffey, C.; Smeed, D.A.

    2016-01-01

    Using underwater gliders we have identified canyon driven upwelling across the Celtic Sea shelf-break, in the vicinity of Whittard Canyon. The presence of this upwelling appears to be tied to the direction and strength of the local slope current, which is in itself highly variable. During typical summer time equatorward flow, an unbalanced pressure gradient force and the resulting disruption of geostrophic flow can lead to upwelling along the main axis of two small shelf break canyons. As the...

  16. Short commentary on marine productivity at Arctic shelf breaks: upwelling, advection and vertical mixing

    Science.gov (United States)

    Randelhoff, Achim; Sundfjord, Arild

    2018-04-01

    The future of Arctic marine ecosystems has received increasing attention in recent years as the extent of the sea ice cover is dwindling. Although the Pacific and Atlantic inflows both import huge quantities of nutrients and plankton, they feed into the Arctic Ocean in quite diverse regions. The strongly stratified Pacific sector has a historically heavy ice cover, a shallow shelf and dominant upwelling-favourable winds, while the Atlantic sector is weakly stratified, with a dynamic ice edge and a complex bathymetry. We argue that shelf break upwelling is likely not a universal but rather a regional, albeit recurring, feature of the new Arctic. It is the regional oceanography that decides its importance through a range of diverse factors such as stratification, bathymetry and wind forcing. Teasing apart their individual contributions in different regions can only be achieved by spatially resolved time series and dedicated modelling efforts. The Northern Barents Sea shelf is an example of a region where shelf break upwelling likely does not play a dominant role, in contrast to the shallower shelves north of Alaska where ample evidence for its importance has already accumulated. Still, other factors can contribute to marked future increases in biological productivity along the Arctic shelf break. A warming inflow of nutrient-rich Atlantic Water feeds plankton at the same time as it melts the sea ice, permitting increased photosynthesis. Concurrent changes in sea ice cover and zooplankton communities advected with the boundary currents make for a complex mosaic of regulating factors that do not allow for Arctic-wide generalizations.

  17. Short commentary on marine productivity at Arctic shelf breaks: upwelling, advection and vertical mixing

    Directory of Open Access Journals (Sweden)

    A. Randelhoff

    2018-04-01

    Full Text Available The future of Arctic marine ecosystems has received increasing attention in recent years as the extent of the sea ice cover is dwindling. Although the Pacific and Atlantic inflows both import huge quantities of nutrients and plankton, they feed into the Arctic Ocean in quite diverse regions. The strongly stratified Pacific sector has a historically heavy ice cover, a shallow shelf and dominant upwelling-favourable winds, while the Atlantic sector is weakly stratified, with a dynamic ice edge and a complex bathymetry. We argue that shelf break upwelling is likely not a universal but rather a regional, albeit recurring, feature of the new Arctic. It is the regional oceanography that decides its importance through a range of diverse factors such as stratification, bathymetry and wind forcing. Teasing apart their individual contributions in different regions can only be achieved by spatially resolved time series and dedicated modelling efforts. The Northern Barents Sea shelf is an example of a region where shelf break upwelling likely does not play a dominant role, in contrast to the shallower shelves north of Alaska where ample evidence for its importance has already accumulated. Still, other factors can contribute to marked future increases in biological productivity along the Arctic shelf break. A warming inflow of nutrient-rich Atlantic Water feeds plankton at the same time as it melts the sea ice, permitting increased photosynthesis. Concurrent changes in sea ice cover and zooplankton communities advected with the boundary currents make for a complex mosaic of regulating factors that do not allow for Arctic-wide generalizations.

  18. Upwelling and downwelling induced by mesoscale circulation in the DeSoto Canyon region

    Science.gov (United States)

    Nguyen, T. T.; Chassignet, E.; Morey, S. L.; Dukhovskoy, D. S.

    2014-12-01

    Ocean dynamics are complex over irregular topography areas, and the northeastern Gulf of Mexico, specifically the DeSoto Canyon region, is a challenge for modelers and oceanographers. Vertical movement of waters, especially upwelling, is observed to take place over the canyon's head and along the coast; however, it is not well understood. We focus on upwelling/downwelling processes induced by the Loop Current and its associated eddy field using multi-decadal Hybrid Coordinate Ocean Model simulations. The Loop Current, part of the Gulf Stream, can develop northward into the Gulf through the Yucatan Channel and exit through the Florida Straits. It can reach the continental slope of the study domain and directly depress the isopycnals. Cyclonic eddies in front of the Loop Current also induce upwelling underneath. On the other hand, the Loop Current sometimes impinges on the West Florida Shelf and generates a high pressure disturbance, which travels northward along the shelf into the study region. Consequently, large-scale downwelling occurs across the continental slopes. Our analysis of sea surface height shows that the Loop Current pressure disturbance tends to propagate along the shallow isobaths of 100 to 300 m in the topographic wave direction from south of the West Florida Shelf to the Mississippi Delta. In addition, after shedding a large anticyclonic eddy, the Loop Current retracts southward and can touch the southeastern corner of the West Florida Shelf. This can result in a higher pressure disturbance, and therefore stronger large-scale downwelling in the DeSoto Canyon region.

  19. Trophic modelling of the Peruvian upwelling ecosystem: Towards reconciliation of multiple datasets

    Science.gov (United States)

    Guénette, Sylvie; Christensen, Villy; Pauly, Daniel

    2008-10-01

    In the 1980s, personnel from the Instituto del Mar del Peru collaborated with foreign experts to reconstruct time series of (1) catch and biomass of the Peruvian anchovy Engraulis ringens back to 1953, along with parallel time series of (2) abundance of anchovy predators and competitors, and (3) abiotic parameters indicative of the dynamics of the Peruvian upwelling system. This contribution documents an attempt to build an ecosystem model of the Peruvian upwelling ecosystem and recreate the observed biomass trends through the period 1953-1984, using the Ecopath with Ecosim (EwE) software. The time series of biomass, particularly of Peruvian anchovy and its various predators, are not reproduced by the EwE model based solely on the original parameters. Instead, to model the anchovy abundance fluctuations caused by El Niño and other oceanographic events, it is necessary to include mechanisms that were not part of the original description of the ecosystem, which focused on mass-balance. For example, a switch between large and small phytoplankton appears to be required to induce the observed abundance shifts between sardine and anchovy. Similarly, a ‘mitigating’ relationship must be assumed between bonito ( Sarda chilensis) and seabirds for the 1965 collapse of seabirds to be reproduced by the model. Mechanisms of this sort, here proposed in a very tentative fashion, will have to be firmly established and quantified before a model can successfully explain both the older data series (1953-1984) as done here, and eventually the new series on the Peruvian upwelling system that became available only recently. With a total of now over 50 years of data, this would represent one of the best documented marine ecosystems in the world, matching its status as one of the most productive.

  20. Upwelling UV spectral irradiances and surface albedo measurements at Lauder, New Zealand

    Science.gov (United States)

    McKenzie, R. L.; Kotkamp, M.; Ireland, W.

    Simultaneous measurements of upwelling and downwelling ultraviolet (UV) spectral irradiance were used to deduce the wavelength dependence and the solar zenith angle dependence of the albedo of the ground surface (long grass) at Lauder, New Zealand (45.05°S, 169.68°E). In the UVB region the deduced albedos are approximately 1%. At longer wavelengths the albedo increases to approximately 2% at 400 nm, and 4.5% at 450 nm. These albedos are significantly smaller than those generally quoted for the visible region. The deduced albedos tend to increase at larger solar zenith angles, demonstrating that the surface is not strictly Lambertian.

  1. Ocean variability over the Agulhas Bank and its dynamical connection with the southern Benguela upwelling system

    CSIR Research Space (South Africa)

    Blanke, B

    2009-12-01

    Full Text Available and interannual variability. We put the stress on wind forcing since the seasonal and interannual variability of the Benguela upwelling system depends significantly on wind variability [Blanke et al., 2002, 2005], with the appearance of subsequent SST...-resolution child model is designed to encompass the Agulhas Bank and its surroundings and has a temporal and spatial resolution three times finer than the parent grid (approximately 15 min and 8 km, respec- tively). The child model has 233 � 185 grid points...

  2. Biological consequences of environmental changes related to coastal upwelling: a simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Howe, S.O.

    1979-05-01

    Two simulation models of marine ecosystem dynamics are formulated and applied to field data. The first is a time-dependent model of phytoplankton growth in nutrient-enriched batch cultures where spatial gradients of dependent variables and the effects of higher tropic level processes are not included. Rates of photosynthesis, nutrient uptake, chlorophyll synthesis and cell division for a single phytoplankton functional group are simulated as functions of photosynthetically active solar radiation, dissolved nutrient concentrations and cell quotas of carbon, nitrogen and silica. The second model combines the phytoplankton growth model with a time dependent, two-dimensional model of coastal upwelling off northwest Africa.

  3. Bowhead whale body condition and links to summer sea ice and upwelling in the Beaufort Sea

    Science.gov (United States)

    George, John C.; Druckenmiller, Matthew L.; Laidre, Kristin L.; Suydam, Robert; Person, Brian

    2015-08-01

    We examined the response of bowhead whale (Balaena mysticetus) body condition to summer sea ice conditions and upwelling-favorable winds. We used a long-term dataset collected from whales of the Bering-Chukchi-Beaufort Seas (BCB) stock to estimate various body condition indices (BCI's) for individual whales that were harvested by Alaskan Eskimos. A series of offshore regions frequented by bowhead whales in summer were delineated and used to quantify interannual summertime environmental conditions including: (a) mean open water fraction, (b) duration of melt season, (c) date of continuous freeze-up, and (d) mean upwelling-favorable wind stress. Body condition was analyzed relative to these metrics for both the preceding summer feeding season and the previous three seasons combined. Our analysis indicates a significant increase in the long-term trend in an axillary girth-based body condition index (BCIG) over the study period (1989-2011). The increase in BCIG is likely associated with the trend in overall reduction of sea ice, including increased duration of open water, changes in upwelling potential (wind stress), and possibly higher primary production in the Pacific Arctic marine ecosystem favoring water-column invertebrates. We found strong significant positive correlations between BCIG and late summer open water fraction in the Beaufort Sea and smaller nearshore areas off the Mackenzie Delta and west of Banks Island. Additionally, BCIG was positively and significantly correlated with duration of melt season, later date of freeze-up in the Beaufort Sea, and upwelling-favorable winds on the Mackenzie shelf and west of Banks Island. A strong seasonal difference in BCI's was noted for subadult bowheads, presumably associated with summer feeding; however, yearlings were found to drop in BCI over at least the first summer after weaning. Our results indicate an overall increase in bowhead whale body condition and a positive correlation with summer sea ice loss over the

  4. Surface circulation and upwelling patterns around Sri Lanka and formation of the Sri Lanka Dome

    Science.gov (United States)

    Pattiaratchi, C. B.; Wijeratne, S.; De Vos, A.

    2014-12-01

    Sri Lanka, a relatively large island (length 440 km; width 225 km), occupies a unique location within the equatorial belt in the northern Indian Ocean with the Arabian Sea on its western side and the Bay of Bengal on its eastern side and experiences bi-annually reversing monsoon winds. This allows for the Island to interact with the seasonally reversing monsoon currents leading to the the island mass effect and enhanced primary production. We will present elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The model was run for 4 years to examine the inter-annual, seasonal and shorter term (~10 days) variability. The results confirmed the presence of the reversing current system, between the equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the Southwest (SW) monsoon transporting 11.5 Sv and the westward flowing Northeast Monsoon Current (NMC) transporting 9.5 Sv during the Northeast (NE) monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the Island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the south coast (see Figure). During the SW monsoon the Island deflects the eastward flowing SMC southward whilst along the east coast the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the south coast resulting from southward flow converging along the south coast and subsequent divergence associated with the offshore transport of water(see Figure). Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and

  5. Glacial-interglacial productivity contrasts along the eastern Arabian Sea: Dominance of convective mixing over upwelling

    Directory of Open Access Journals (Sweden)

    Kumar Avinash

    2015-11-01

    The primary productivity along the southwestern continental margin of India seems to have been controlled principally by the upwelling during the southwest monsoon season that was weaker from MIS-4 to MIS-2, as relative to that during the MIS-1. In contrast, increased glacial productivity noticed in sediments deposited below the current oxygen minimum zone (OMZ along the north of the study area that can be linked to entrainment of nutrients through the intensified convective mixing of surface water during the northeast monsoon. The sequestration of greenhouse gases by the western continental margin of India was higher during glacial than interglacial cycles.

  6. The spatial variability of coastal surface water temperature during upwelling. [in Lake Superior

    Science.gov (United States)

    Scarpace, F. L.; Green, T., III

    1979-01-01

    Thermal scanner imagery acquired during a field experiment designed to study an upwelling event in Lake Superior is investigated. Temperature data were measured by the thermal scanner, with a spatial resolution of 7 m. These data were correlated with temperatures measured from boats. One- and two-dimensional Fourier transforms of the data were calculated and temperature variances as a function of wavenumber were plotted. A k-to-the-minus-three dependence of the temperature variance on wavenumber was found in the wavenumber range of 1-25/km. At wavenumbers greater than 25/km, a k-to-the-minus-five-thirds dependence was found.

  7. Slab break-off triggered lithosphere - asthenosphere interaction at a convergent margin: The Neoproterozoic bimodal magmatism in NW India

    Science.gov (United States)

    Wang, Wei; Pandit, Manoj K.; Zhao, Jun-Hong; Chen, Wei-Terry; Zheng, Jian-Ping

    2018-01-01

    The Neoproterozoic Malani Igneous Suite (MIS) is described as the largest felsic igneous province in India. The linearly distributed Sindreth and Punagarh basins located along eastern margin of this province represent the only site of bimodal volcanism and associated clastic sediments within the MIS. The in-situ zircon U-Pb dating by LA-ICPMS reveals that the Sindreth rhyolites were erupted at 769-762 Ma. Basaltic rocks from both the basins show distinct geochemical signatures that suggest an E-MORB source for Punagarh basalts (low Ti/V ratios of 40.9-28.2) and an OIB source (high Ti/V ratios of 285-47.6) for Sindreth basalts. In the absence of any evidence of notable crustal contamination, these features indicate heterogeneous mantle sources for them. The low (La/Yb)CN (9.34-2.10) and Sm/Yb (2.88-1.08) ratios of Punagarh basalts suggest a spinel facies, relatively shallow level mantle source as compared to a deeper source for Sindreth basalts, as suggested by high (La/Yb)CN (7.24-5.24) and Sm/Yb (2.79-2.13) ratios. Decompression melting of an upwelling sub-slab asthenosphere through slab window seems to be the most plausible mechanism to explain the geochemical characteristics. Besides, the associated felsic volcanics show A2-type granite signatures, such as high Y/Nb (5.97-1.55) and Yb/Ta (9.36-2.57) ratios, consistent with magma derived from continental crust that has been through a cycle of continent-continent collision or an island-arc setting. A localized extension within an overall convergent scenario is interpreted for Sindreth and Punagarh volcanics. This general convergent setting is consistent with the previously proposed Andean-type continental margin for NW Indian block, the Seychelles and Madagascar, all of which lay either at the periphery of Rodinia supercontinent or slightly off the Supercontinent.

  8. African Trypanosomiasis

    Science.gov (United States)

    2011-06-01

    a disease of horses, mules, camels , and cattle. African trypanosomiasis has probably played an impor- tant role in recorded history from antiquity...Saunders; 1929:706. 6. Baker JR. The subspecific taxonomy of Trypanosoma brucei. Parasite. 1995;2:3-12. 7. Control and surveillance of African

  9. African Zoology

    African Journals Online (AJOL)

    African Zoology, a peer-reviewed research journal, publishes original scientific contributions and critical reviews that focus principally on African fauna in terrestrial, freshwater, and marine ecosystems. Research from other regions that advances practical and theoretical aspects of zoology will be considered. Rigorous ...

  10. Interannual control of plankton communities by deep winter mixing and prey/predator interactions in the NW Mediterranean: Results from a 30-year 3D modeling study

    Science.gov (United States)

    Auger, P. A.; Ulses, C.; Estournel, C.; Stemmann, L.; Somot, S.; Diaz, F.

    2014-05-01

    A realistic modeling approach is designed to address the role of winter mixing on the interannual variability of plankton dynamics in the north-western (NW) Mediterranean basin. For the first time, a high-resolution coupled hydrodynamic-biogeochemical model (Eco3m-S) covering a 30-year period (1976-2005) is validated on available in situ and satellite data for the NW Mediterranean. In this region, cold, dry winds in winter often lead to deep convection and strong upwelling of nutrients into the euphotic layer. High nutrient contents at the end of winter then support the development of a strong spring bloom of phytoplankton. Model results indicate that annual primary production is not affected by winter mixing due to seasonal balance (minimum in winter and maximum in spring). However, the total annual water column-integrated phytoplankton biomass appears to be favored by winter mixing because zooplankton grazing activity is low in winter and early spring. This reduced grazing is explained here by the rarefaction of prey due to both light limitation and the effect of mixing-induced dilution on prey/predator interactions. A negative impact of winter mixing on winter zooplankton biomass is generally simulated except for mesozooplankton. This difference is assumed to stem from the lower parameterized mortality, top trophic position and detritivorous diet of mesozooplankton in the model. Moreover, model suggests that the variability of annual mesozooplankton biomass is principally modulated by the effects of winter mixing on winter biomass. Thus, interannual variability of winter nutrient contents in the euphotic layer, resulting from winter mixing, would control spring primary production and thus annual mesozooplankton biomass. Our results show a bottom-up control of mesozooplankton communities, as observed at a coastal location of the Ligurian Sea.

  11. Initial observation of upwelling along east coast of Peninsular Malaysia musica-gratis.softonic.it/ >musica gratis

    Science.gov (United States)

    Akhir, M.; Tanggang, F.

    2013-12-01

    There is no published evidence of upwelling in coastal area along the east coast of Peninsular Malaysia. However numbers of recent cruise data collected during the southwest monsoon found features of thermocline lifting and isolated cooler temperature water along the coast, These sign was observed along the 104°E from numbers of parallel transects. To confirm the presence of upwelling, satellite remote sensing data was used, and numerical model experiments were conducted. Cooler sea-surface temperature along the coast was observed from both in-situ and satellite data, while upward movement in the vertical profiles agreed with the location of upwelling from both in-situ and satellite data. Moreover, these data also show that the upwelled water band along the 104°E longitude stretch approximately 650 km long. Initially, southwesterly wind during this season is believed to be the important mechanism that contributed to this wind-induced Ekman upwelling. musica-gratis.softonic.it/ >musica gratis

  12. African Journals Online: African Studies

    African Journals Online (AJOL)

    Items 1 - 50 of 56 ... African Journal of Library, Archives and Information Science is established mainly to provide a forum for librarians, archivists, documentalists, information scientists and other information related professionals in Africa to report their research findings but with emphasis on African setting. The Journal is ...

  13. Potential for Great Thrust Earthquakes in NE Colombia & NW Venezuela

    Science.gov (United States)

    Bilham, R. G.; Mencin, D.

    2013-05-01

    Sixty-five percent of the ≈19 mm/yr eastward velocity of the Caribbean Plate north of Aruba and the Guajira peninsula relative to the South American plate is accommodated by dextral slip on the Bocono Fault system in NW Venezuela at 12±1 mm/yr, the remaining ~3 mm/yr of shear apparently distributed to the NW of the fault (Perez et al., 2011). The N40E strike of the Bocono fault system, however, requires that 10.6±1 mm/yr of convergence should accompany this partitioned dextral shear, but GPS measurements reveal that less than 25% of this convergence occurs across the Venezuelan Andes. The remaining 6-8 mm of convergence is presumably accommodated by incipient subduction between the Bocono fault and a trench 300 km NW of the northern coast of Colombia. Hence NW Venezuela and NE Colombia may occasionally host great earthquakes. Our current poor understanding of the geometry of the plate interface permits the plate to be locked 300 km down-dip and possibly 600 km along-strike, and if the plate slips in 10 m ruptures it could do so every 1200 years in a M~9 earthquake. No great earthquake has occurred since 1492, since when ~4 m of potential slip has developed, but should slip occur on just 10% of the hypothesized décollement (100x150 km) it could do so now in an Mw=8.2 earthquake. In that a potential Mw>8 earthquake poses a future seismic and tsunami threat to the Caribbean it is important to examine whether great earthquakes have occurred previously near the NW Venezuela coast. It is possible that creep accommodates the entire convergence signal, since there is no suggestion from microseismicity for an abrupt locked-to-sliding transition, as, for example, signifies its location in the Himalaya. An alternative measure of future potential seismic energy release is to identify the locus and rate of present-day strain contraction. To this end, Venezuelan, Colombian and US (CU and UNAVCO) investigators are installing an array of more than a dozen continuous operating

  14. Joint effect of freshwater plume and coastal upwelling on phytoplankton growth off the Changjiang River

    Science.gov (United States)

    Tseng, Y.-F.; Lin, J.; Dai, M.; Kao, S.-J.

    2014-01-01

    The Changjiang (Yangtze) River discharges vast amount of unbalanced nutrients (dissolved inorganic nitrogen and phosphorus with N / P ratio > 80 in general) into the East China Sea in summer. To study nutrient dynamics and P-stress potential for phytoplankton, a cruise was conducted in the Changjiang plume during summer 2011. With 3-D observations of nutrients, chlorophyll a (Chl a), and bulk alkaline phosphatase activity (APA), we concluded that the Changjiang Diluted Water and coastal upwelling significantly influenced the horizontal and vertical heterogeneities of phytoplankton P deficiency in the Changjiang plume. Allochthonous APA was detected at nutrient-enriched freshwater end. Excessive N (~ 10 to 112 μM) was observed throughout the entire plume surface. In the plume fringe featuring stratification and excess N, diapycnal phosphate supply was blocked and phytoplankton APA was stimulated for growth. We observed an upwelling just attaching to the turbidity front at seaward side where Chl a peaked yet much less APA was detected. An external phosphate supply from subsurface, which promoted phytoplankton growth but inhibited APA, was suggested to be sourced from the Nearshore Kuroshio Branch Current. In the so hydrographically complicated Changjiang plume, phosphate supply instead of its concentration may be more important in determining the expression of APA. Meanwhile, allochthonous APA may also alter the usefulness of APA as a P-stress indicator.

  15. A Broad-Area Method for the Diurnal Characterisation of Upwelling Medium Wave Infrared Radiation

    Directory of Open Access Journals (Sweden)

    Bryan Hally

    2017-02-01

    Full Text Available Fire detection from satellite sensors relies on an accurate estimation of the unperturbed state of a target pixel, from which an anomaly can be isolated. Methods for estimating the radiation budget of a pixel without fire depend upon training data derived from the location’s recent history of brightness temperature variation over the diurnal cycle, which can be vulnerable to cloud contamination and the effects of weather. This study proposes a new method that utilises the common solar budget found at a given latitude in conjunction with an area’s local solar time to aggregate a broad-area training dataset, which can be used to model the expected diurnal temperature cycle of a location. This training data is then used in a temperature fitting process with the measured brightness temperatures in a pixel, and compared to pixel-derived training data and contextual methods of background temperature determination. Results of this study show similar accuracy between clear-sky medium wave infrared upwelling radiation and the diurnal temperature cycle estimation compared to previous methods, with demonstrable improvements in processing time and training data availability. This method can be used in conjunction with brightness temperature thresholds to provide a baseline for upwelling radiation, from which positive thermal anomalies such as fire can be isolated.

  16. Multi-scale processes drive benthic community structure in upwelling-affected coral reefs

    Directory of Open Access Journals (Sweden)

    Corvin eEidens

    2015-02-01

    Full Text Available Environmental processes acting at multiple spatial scales control benthic community structures in coral reefs. However, the contribution of local factors (e.g., substrate availability and water clarity vs. non-local oceanographic processes (e.g. upwelling events in these highly complex systems is poorly understood. We therefore investigated the relative contribution of local and non-local environmental factors on the structure of benthic groups and specifically on coral assemblages in the upwelling-affected Tayrona National Natural Park (TNNP, Colombian Caribbean. Coral-dominated communities were monitored along with key environmental parameters at water current-exposed and -sheltered sites in four consecutive bays. Regression tree analyses revealed that environmental parameters explained 59.1% of the variation within the major benthic groups and 36.1% within coral assemblages. Findings also showed recurring patterns in community structures at sites with similar exposure across bays. We suggest that benthic community composition in TNNP is primarily driven by 1 wave exposure, followed by 2 temporal changes in nutrient availability governing the structure of benthic groups, and 3 local bay-specific differences controlling the zonation of benthic groups and coral assemblages. This study highlights the existence of complex hierarchical levels of local and non-local environmental factors acting on reef communities and stresses the importance of considering processes operating at multiple spatial scales in future studies on coral reef community structure and resilience.

  17. Comparing Derived and Actual Upwelling Longwave Measurements at the CERES Ocean Validation Experiment (COVE)

    Science.gov (United States)

    Fabbri, B. E.; Schuster, G. L.; Denn, F. M.; Arduini, R. F.; Madigan, J. J.

    2017-12-01

    One of the parameters measured from the Clouds and the Earth's Radiant Energy System (CERES) satellite is Earth emitted or longwave (LW) radiation. One validation site to compare this quantity is the CERES Ocean Validation Experiment (COVE), located at Chesapeake Light Station, approximately 25 kilometers east of Virginia Beach, Virginia (coordinates: 36.90N, 75.71W). However, the upwelling measurement is complicated due to the Light Station tower being in the LW instruments field of view. A negative outcome of the tower being in the field of view is a tower radiating effect, especially noticeable on clear, sunny days. During these days, the tower tends to heat up and radiate extra heat energy that is measured by the LW instrument. To understand the extent of the problem, we derive upwelling longwave measurements at the surface using sea surface temperature, air temperature, and dewpoint to compare with the actual longwave measurement made with an Eppley Laboratory pyrgeometer. The data used in this study is over a four-year period (2009-2012). One result using only nighttime data (range: 15.0 =solar insolation creating the tower radiating effect. Other results comparing the diurnal scope are analyzed and presented.

  18. Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an ENSO event

    DEFF Research Database (Denmark)

    Loick-Wilde, Natalie; Bombar, Deniz; Doan, Hai Nhu

    2017-01-01

    Investigating microplankton biomass and diversity under different climatological conditions is key to the understanding of cascading effects of climate change on nutrient cycles and biological productivity. Here we have used data collected during two contrasting summers along the coast of Viet Nam...... to show how climatological-driven changes can have a significant influence on the distribution of microplankton communities and their biomass via its impact on nutrient concentrations in the water column. The first summer in July 2003 followed a weak El-Nino Southern Oscillation (ENSO) event...... and was characterized by weak coastal upwelling, in the second summer during July 2004, upwelling was normal. Very low silicate (SiO4) concentrations and SiO4:DIN ratios characterized the source water mass for upwelling in July 2004, and dynamic SiO4 to dissolved inorganic nitrogen ratios (SiO4:DIN) mainly below...

  19. Upwelling-derived oceanographic conditions impact growth performance and growth-related gene expression in intertidal fish.

    Science.gov (United States)

    Fuentes, Eduardo N; Zuloaga, Rodrigo; Almarza, Oscar; Mendez, Katterinne; Valdés, Juan Antonio; Molina, Alfredo; Pulgar, Jose

    2017-12-01

    Growth is one of the main biological processes in aquatic organisms that is affected by environmental fluctuations such as upwelling (characterized by food-rich waters). In fish, growth is directly related with skeletal muscle increase; which represents the largest tissue of body mass. However, the effects of upwelling on growth, at the physiological and molecular level, are unknown. This study used Girella laevifrons (one of the most abundant intertidal fish in Eastern South Pacific) as a biological model, considering animals from upwelling (U) and non-upwelling (NU) areas. Here, we evaluated the effect of nutritional composition and food availability on growth performance and expression of key growth-related genes (insulin-kike growth factor 1 (igf1) and myosin heavy-chain (myhc)) and atrophy-related genes (muscle ring-finger 1 (murf1), F-box only protein 32 (atrogin-1) and BCL2/adenovirus E1B 19kDa-interacting protein 3 (bnip3)). We reported that, among zones, U fish displayed higher growth performance in response to nutritional composition, specifically between protein- and fiber-rich diets (~1g). We also found in NU fish that atrophy-related genes were upregulated with fiber-rich diet and during fasting (~2-fold at minimum respect U). In conclusion, our results suggest that the growth potential of upwelling fish may be a consequence of differential muscle gene expression. Our data provide a preliminary approach contributing on how upwelling influence fish growth at the physiological and molecular levels. Future studies are required to gain further knowledge about molecular differences between U and NU animals, as well as the possible applications of this knowledge in the aquaculture industry. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Habitat characteristics influence macrofaunal communities in coralline turf more than mesoscale coastal upwelling on the coast of Northern Chile

    Science.gov (United States)

    Kelaher, Brendan P.; Carlos Castilla, Juan

    2005-04-01

    Rocky shore communities are often influenced by near-shore coastal upwelling. For macrofauna in algal turf, these effects may be caused directly by well-studied bottom-up mechanisms or indirectly via changes in habitat structure provided by algal turf associated high nutrient loads. Here, we investigated possible interactions between upwelling and habitat structure by sampling diverse faunal assemblages in coralline algal turf on seven rocky intertidal shores in northern Chile, ranging from El Cobre [23°17'1″S, 70°31'40″W] to La Lobería [23°03'40″S, 70°33'14″W]. Some of these shores were located adjacent to strong upwelling centers, while others were in areas rarely affected. On each shore, we sampled four (2 × 2 m) sites separated by 15-50 m. In each site, we collected three replicate cores (80 mm in diameter) from which we measured macrofauna greater than 850 μm, biomass of sediment and epiphytes, frond density and average frond length. We used mean water temperature and its variation at 1-1.5 m water depth (below Extreme Low Water Spring, ELWS) to represent local upwelling intensity because long-term data have shown that these variables make excellent indicators for this region. In total, we found 94 macrofaunal taxa in coralline turf, which is almost three times higher than has previously been reported in Chile. Although macrofaunal assemblages varied significantly among shores, there were no patterns to suggest mesoscale variation in upwelling intensity affected either faunal assemblages or local habitat characteristics. In contrast, multivariate and univariate correlations highlighted sediment and frond density as strong determinants of community structure. We therefore conclude that traditionally studied habitat characteristics, such as structural complexity and habitat heterogeneity, have greater influence on faunal assemblages in mat-like habitats on rocky shores than environmental variables associated with mesoscale coastal upwelling.

  1. Spatiotemporal variation of vertical particle fluxes and modelled chlorophyll a standing stocks in the Benguela Upwelling System

    Science.gov (United States)

    Vorrath, Maria-Elena; Lahajnar, Niko; Fischer, Gerhard; Libuku, Viktor Miti; Schmidt, Martin; Emeis, Kay-Christian

    2018-04-01

    Marine particle fluxes from high productive coastal upwelling systems return upwelled CO2 and nutrients to the deep ocean and sediments and have a substantial impact on the global carbon cycle. This study examines relations between production regimes on the shelf and over the continental margin of the Benguela Upwelling System (BUS) in the SE Atlantic Ocean. Data of composition and timing of vertical particle flux come from sediment trap time series (deployed intermittently between 1988 and 2014) in the regions Walvis Ridge, Walvis Bay, Luederitz and Orange River. We compare their seasonal variability to modelled patterns of chlorophyll concentrations in a 3-D ecosystem model. Both modelled seasonal chlorophyll a standing stocks and sampled particle flux patterns are highly correspondent with a bimodal seasonal cycle offshore the BUS. The material in the particle flux in offshore traps is dominantly carbonate (40-70%), and flux peaks in offshore particle flux originate from two independent events: in austral autumn thermocline shoaling and vertical mixing are decoupled from coastal upwelling, while fluxes in spring coincide with the upwelling season, indicated by slightly elevated biogenic opal values at some locations. Coastal particle fluxes are characterized by a trimodal pattern and are dominated by biogenic opal (22-35%) and organic matter (30-60%). The distinct seasonality in observed fluxes on the shelf is caused by high variability in production, sinking behaviour, wind stress, and hydrodynamic processes. We speculate that global warming will increase ocean stratification and alter coastal upwelling, so that consequences for primary production and particle flux in the BUS are inevitable.

  2. Quantifying the impact of an upwelling filament on the physical-chemical-biological interactions off SW Iberia

    Science.gov (United States)

    Cravo, A.; Sanchez, R.; Monteiro, C.; Cardeira, S.; Madureira, M.; Rita, F.; Relvas, P.

    2017-12-01

    Upwelling filaments are mesoscale structures of cold water that stretch seaward in a tongue-like shape with origin in the coastal upwelling zone. Filaments off the Iberian Peninsula are recurrent, showing similarities with those in the Californian coast. The Cape São Vicente, the SW tip of the Iberian Peninsula, is the root of recurrent filaments observed in the satellite imagery during the upwelling season. However, the understanding of its physical and chemical impact on the biological productivity is rather limited. There, a relatively small filament ( 80 km long) was investigated through remote sensing and in situ multidisciplinary observations during an upwelling favourable wind relaxation event, but just after an intense upwelling period. A total of 42 CTD+Rosette casts up to 400 m depth were distributed on an almost regular grid of 15 km mean spacing guided by guided by satellite SST imagery transmitted to the ship in near-real time. The parameters sampled during the sea campaign included: velocity field sampled along the ship track through a hull-mounted 38 kHz RDI ADCP, meteorological variables, temperature, salinity, chlorophyll a, dissolved oxygen, nitrate, phosphate, silicate, cadmium, lead and zinc. The extent of the impact of the filament was evaluated by quantifying the cross-shelf transports of several properties. The amounts conveyed by the filament were much stronger than those expected by the wind-driven Ekman mechanism, showing that it represents an efficient feature for the exchange of water, dissolved and particulate matter from the productive shelf towards the oligotrophic offshore region. Considering the periods of strong upwelling events and the extent of their duration along the year, the amounts of exported matter will certainly enhance the biological productivity of these waters, including its fisheries. These filament data contribute to better understand the physical-chemical-biological interactions of this regional ecosystem.

  3. Response of zooplankton to physical changes in the environment: coastal upwelling along central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Madhupratap, M.; Nair, S.R.S.; Haridas, P.; Padmavati, G.

    higher than those recorded even 'j during zooplankton swarms from the northern Indian Ocean (2.5 to 4.8 ml.m", MADHUPRA TAP et ai., 1980). Offshore biomass was low rel ative to upwelled regions but generally higher than noted in other non... of India. Temora turbinata and Acrocalanus sp. have been reported to form swarms during upwelling sea son (HARIDAS et 0/., 1980). The stndy also showed that most ofthese copepoda have either poor abundances or are absent in inshore waters during other...

  4. Bioturbational structures record environmental changes in the upwelling area off Vietnam (South China Sea) for the last 150,000 years

    NARCIS (Netherlands)

    Wetzel, A.; Tjallingii, R.; Wiesner, M.G.

    2011-01-01

    The sediments in the upwelling area off central Vietnam are totally bioturbated and display a low-diverse assemblage of bioturbational structures. During interglacial times (Marine Isotope Stage MIS 1, 5a, 5c, 5e), summer monsoon leads to pronounced upwelling and seasonally pulsed arrival of organic

  5. Total and mesoscale long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

    Science.gov (United States)

    Lovecchio, Elisa; Gruber, Nicolas; Münnich, Matthias; Byrne, David; Lachkar, Zouhair

    2017-04-01

    The ocean's biological pump is often simplified to a purely vertical process. Nevertheless, the horizontal transport of organic carbon can be substantial, especially in coastal regions such as the Canary Upwelling System (CanUS), one of the four major Eastern Boundary Upwelling Systems, characterized by high shelf productivity and an intense lateral exchange of mass and tracers with the adjacent oligotrophic waters. Despite its importance, the magnitude of this lateral flux has not yet been constrained. Here, we quantify the lateral export of organic carbon from the CanUS to the open North Atlantic using the Regional Ocean Modeling System (ROMS) coupled to a biogeochemical ecosystem module. The model is run on an Atlantic telescopic grid with a strong refinement towards the north-western African shelf, to combine an eddy-resolving resolution in the region of study with a full Atlantic basin perspective. Our results reveal that over the whole CanUS more than a third of the Net Community Production (NCP) in the nearshore 100 km is transported offshore, amounting to about 19 Tg C yr-1. The offshore transport dominates the lateral fluxes up to 1500 km into the subtropical North Atlantic, along the way adding organic carbon to the upper 100 m at rates of between 8% and 34% of the alongshore average NCP. The remineralization at depth of this extra organic carbon leads to strongly negative vertically-integrated NCP throughout the whole offshore region of the CanUS, i.e. it makes the offshore region net heterotrophic. Substantial subregional variability shapes the spatial pattern of the fluxes in the CanUS. In particular, the central subregion surrounding Cape Blanc is the most efficient in terms of collecting and laterally exporting the organic carbon, resulting in a sharp peak of watercolumn heterotrophy. A decomposition of the organic carbon fluxes into a time-mean component and a time-variable, i.e., mesoscale component reveals a large contribution of the mesoscale

  6. Mercury speciation in fish of the Cabo Frio upwelling region, SE-Brazil

    Directory of Open Access Journals (Sweden)

    Carlos Alberto da Silva

    2011-09-01

    Full Text Available Mercury distribution in the oceans is controlled by complex biogeochemical cycles, resulting in retention of trace amounts of this metal in marine biota. The impact of upwelling processes in this metal behavior has been overlooked. Data from literature are insufficient to evaluate the risks associated with the presence of mercury in the fish collected in upwelling areas and its consumers. Therefore, the aim of the present work was to perform a study of mercury speciation in four fish species belonging to different trophic levels from Cabo Frio-Brazil upwelling region. The total mercury content vary of 53 ng g-1 (Sardinella brasiliensis -sardine to 1215 ng g-1 (Cynoscion striatus -striped weakfish and, with exception of the planktivorous fish, methylmercury levels reaches circa 90% of total mercury concentration.A distribuição de Mercúrio nos oceanos é controlada por um complexo ciclo biogeoquímico, resultando na retenção de pequenas quantidades na biota marinha. O impacto dos processos de ressurgência costeira no comportamento desse metal tem sido negligenciado. Dados da literatura são insuficientes para elucidar o risco associado com a presença de mercúrio em peixes capturados em áreas de ressurgência e seus consumidores. Portanto o objetivo do presente trabalho foi realizar um estudo de especiação de mercúrio em quatro espécies de peixes pertencentes a diferentes níveis tróficos da região de ressurgência de Cabo Frio-Brasil. O conteúdo total de mercúrio variou de 53 ng g-1 (Sardinella brasiliensis -sardinha to 1215 ng g-1 (Cynoscion striatus -pescada e, com exceção da espécie planctivora, os níveis de metilmercúrio atingem cerca de 90% da concentração total de mercúrio.

  7. Diurnal variability of inner-shelf circulation in the lee of a cape under upwelling conditions

    Science.gov (United States)

    Lamas, L.; Peliz, A.; Dias, J.; Oliveira, P. B.; Angélico, M. M.; Castro, J. J.; Fernandes, J. N.; Trindade, A.; Cruz, T.

    2017-07-01

    The nearshore circulation in the lee of a cape under upwelling conditions was studied using in-situ data from 3 consecutive summers (2006-2008). Focus was given to a period between 20 July and 04 August 2006 to study the diurnal variability of the cross-shelf circulation. This period was chosen because it had a steady upwelling-favourable wind condition modulated by a diurnal cycle much similar to sea breeze. The daily variability of the observed cross-shelf circulation consisted of three distinct periods: a morning period with a 3-layer vertical structure with onshore velocities at mid-depth, a mid-day period where the flow is reversed and has a 2-layer structure with onshore velocities at the surface and offshore flow below, and, lastly, in the evening, a 2-layer period with intensified offshore velocities at the surface and onshore flow at the bottom. The observed cross-shelf circulation showed a peculiar vertical shape and diurnal variability different from several other systems described in literature. We hypothesize that the flow reversal of the cross-shelf circulation results as a response to the rapid change of the wind magnitude and direction at mid-day with the presence of the cape north of the mooring site influencing this response. A numerical modelling experiment exclusively forced by winds simulated successfully most of the circulation at the ADCP site, especially the mid-day reversal and the evening's upwelling-type structure. This supports the hypothesis that the cross-shelf circulation at diurnal timescales is mostly wind-driven. By analysing the 3D circulation in the vicinity of Cape Sines we came to the conclusion that the diurnal variability of the wind and the flow interaction with topography are responsible for the circulation variability at the ADCP site, though only a small region in the south of the cape showed a similar diurnal variability. The fact that the wind diurnally undergoes relaxation and intensification strongly affects the

  8. Resolving the Mantle Heat Transfer Discrepancy by Reassessing Buoyancy Flux Estimates of Upwelling Plumes

    Science.gov (United States)

    Hoggard, Mark; Parnell-Turner, Ross; White, Nicky

    2017-04-01

    The size and relative importance of mantle plumes is a controversial topic within the geodynamics community. Numerical experiments of mantle convection suggest a wide range of possible behaviours, from minor plumelets through to large scale, whole-mantle upwellings. In terms of observations, recent seismic tomographic models have identified many large, broad plume-like features within the lower mantle. In contrast, existing estimates of buoyancy flux calculated from plume swells have suggested that these upwellings transfer a relatively minor amount of material and heat into the uppermost mantle. Here, we revisit these calculations of buoyancy flux using a global map of plume swells based upon new observations of dynamic topography. Usually, plume flux is calculated from the cross-sectional area of a swell multiplied by either plate velocity or spreading rate. A key assumption is that plume head material flows laterally at or below the velocity of the overriding plate. Published results are dominated by contributions from the Pacific Ocean and suggest that a total of ˜ 2 TW of heat is carried by plumes into the uppermost mantle. An alternative approach exploits swell volume scaled by a characteristic decay time, which removes the reliance on plate velocities. The main assumption of this method is that plumes are in quasi-steady state. In this study, we have applied this volumetric approach in a new global analysis. Our results indicate that the Icelandic plume has a buoyancy flux of ˜ 27 ± 4 Mg s-1 and the Hawaiian plume is ˜ 2.9 ± 0.6 Mg s-1. These revised values are consistent with independent geophysical constraints from the North Atlantic Ocean and Hawaii. All magmatic and amagmatic swells have been included, suggesting that the total heat flux carried to the base of the plates is ˜ 10 ± 2 TW. This revised value is a five-fold increase compared with previous estimates and provides an improved match to published predictions of basal heat flux across the

  9. Transient increase in proto-Indian Ocean upwelling during the Cenomanian/Turonian OAE2

    Science.gov (United States)

    Thomas, D. J.; Tilghman, D.

    2013-12-01

    The Oceanic Anoxic Events (OAEs) that punctuated the Cretaceous Period were characterized by the preservation and burial of vast amounts of organic carbon. OAE 2 coincided with the Cenomanian-Turonian boundary ~93.9 Ma, and was the most prominent and globally significant of the major OAEs. The C/T interval was characterized by extreme warmth, and meridional thermal gradients significantly lower than modern. Weaker thermal gradient imply more sluggish oceanic circulation and hence a diminshed rate of seafloor ventilation. These arguments led to the classic idea that stagnation of the overturning circulation likely contributed to enhanced preservation of organic carbon at the sea floor. However, recent Neodymium isotope data from the tropical and North Atlantic basins suggest an active overturning circulation that likely promoted intensified upwelling within the region - thus enhance nutrient delivery to regional sea surface waters may have been the dominant process responsible for anomalous accumulation of organic carbon at the seafloor. A similarly dynamic upwelling regime has been proposed to explain organic carbon accumulation in the South Atlantic. Here we explore the role of deep-water circulation in organic matter preservation during OAE2 in the proto-Indian Ocean, a region potentially characterized by deep-water formation distinct from the Atlantic basins during the Late Cretaceous. We generated high-resolution Nd isotope records at ODP Sites 763, 765, 766, and 1138 and compiled them with previously published lower resolution data from these sites. The new data set indicates a divergence in the Nd isotopic composition of regional intermediate (Site 763) and deep waters (Sites 765/766) that suggests an increase in water mass stratification during the longer term Cenomanian - Turonian interval (~99 to 91 Ma). This stratification occurred in concert with global transgression and a decrease in the regional bulk carbonate oxygen isotope values. However, the

  10. Immunizations and African Americans

    Science.gov (United States)

    ... Data > Minority Population Profiles > Black/African American > Immunizations Immunizations and African Americans African American adults are less ... 19 to 35 months had comparable rates of immunization. African American women are as likely to have ...

  11. A statistical approach to coastal upwelling in the Baltic Sea based on the analysis of satellite data for 1990-2009

    Directory of Open Access Journals (Sweden)

    Andreas Lehmann

    2012-06-01

    Full Text Available A statistical analysis of Baltic Sea upwelling has been carried out to cover, for the first time, the entire sea area for the period 1990-2009. Weekly composite SST maps based on NOAA/AVHRR satellite data were used to evaluate the location and frequency of upwelling. The results obtained were analysed and compared with earlier studies with excellent agreement. Our study enables the most intense upwelling areas in the entire Baltic Sea to be evaluated. According to the analysis of 443 SST maps, the most common upwelling regions are found off the Swedish south and east coasts (frequency 10-25%, the Swedish coast of the Bothnian Bay (16%, the southern tip of Gotland (up to 15%, and the Finnish coast of the Gulf of Finland (up to 15%. Pronounced upwelling also occurs off the Estonian coast and the Baltic east coast (up to 15%, the Polish coast and the west coast of Rügen (10-15%; otherwise the upwelling frequency was between 5 and 10%. Additionally, simulated SST distributions derived from a Baltic Sea numerical model were analysed for the same period. Furthermore, at specific positions close to the coastline, surface winds based on the SMHI meteorological data base were analysed for the same 20-year period. Wind components parallel to the coast were discriminated into favourable and unfavourable winds forcing upwelling. The obtained frequencies of upwelling-favourable winds fit very well the observed upwelling frequencies derived from satellite SST maps. A positive trend of upwelling frequencies along the Swedish east coast and the Finnish coast of the Gulf of Finland was calculated for the period 1990-2009.

  12. Upwelling Rates and Vertical Diffusivities Determined During the 2013 US GEOTRACES Eastern Tropical Pacific Zonal Transect: Results from 7Be Analysis

    Science.gov (United States)

    Kadko, D. C.

    2014-12-01

    Upwelling is an important physical process affecting biogeochemical cycling within the global ocean. Direct measurements are difficult because of the relatively small velocities involved, and must therefore be inferred by indirect methods such as those provided by tracer observations. Measurements of the cosmogenic radioisotope 7Be (half-life = 53.3 d) were used to derive upwelling rates and upper thermocline vertical diffusivities during the 2013 US GEOTRACES Eastern Tropical Pacific Zonal Transect. In the eastern, upwelling zone of this transect, the 7Be activity in the mixed layer varied between low values of 63 dpm/m3 in areas with the coldest sea surface temperatures (SSTs) to values of 190 dpm/m3 associated with warm SSTs. The 7Be inventory in the coldest water was only 5,150 dpm/m2 while that in the warmer water was 19,000 dpm/m2. The decrease in mixed layer 7Be with decrease in temperature occurs as 7Be ''dead'', cold water is upwelled from below. The deficit of the 7Be inventory relative to the non-upwelling stations provides a measure of the upwelling rate. For the eastern-most station with the lowest SST (17.6 deg C) an upwelling rate of 2.56 m/d was derived. Towards the west, as SST increased, derived upwelling rates decreased. At SST of 20.9 deg C, upwelling was zero. With knowledge of upwelling rates, 7Be and temperature profiles were used to constrain vertical diffusivity within the upper thermocline. Diffusivities derived from 7Be profiles were approximately twice that derived from temperature, likely reflecting the difference in vertical resolution of these measurements. Diffusivities derived from temperature were on the order of 1-4 x 10-4 m2/s. These parameters will be applied to profiles of nutrients and trace elements to derive fluxes of these species into the mixed layer.

  13. Is copper an inhibiting factor for primary production in the upwelling waters of Cabo Frio?

    Directory of Open Access Journals (Sweden)

    Diniz Antônia G.

    2003-01-01

    Full Text Available The goal of the present work was to test the hypothesis that inorganic species of copper may inhibit primary production in upwelling waters from the Cabo Frio region. Water samples were collected from four different depths up to 50 m at three stations of Cabo Frio and nutrient concentration, pH, dissolved oxygen, alkalinity, seston, chlorophyll a, primary production, NPP, copper speciation, Cu(II and Cu(I and complexing capacity were determined. The results indicate that the rate of photosynthesis in nutrient rich waters with higher copper content and lower complexing capacity is significantly reduced. Cu(I made up 2-15% of the total copper, however, there was no evidence to suggest that the photochemical production of Cu(I affects NPP.

  14. Grazing and excretion by zooplankton in the Peru upwelling system during April 1977

    Science.gov (United States)

    Dagg, M.; Cowles, T.; Whitledge, T.; Smith, S.; Howe, S.; Judkins, D.

    1980-01-01

    Rates of ingestion and excretion by adult females of the copepods Calanus chilensis, Eucalanus inermis, and Centropages brachiatus were measured in natural seawater during a cruise in the Peru upwelling system during April 1977. Simultaneously, zooplankton samples were collected for later determination of the abundance and distribution of these and other species. For these three organisms, feeding, and excretion rates of individuals are combined with information on the animal concentrations to estimate the grazing stress on the phytoplankton at each station, and to estimate the excretory nitrogen produced at each station. Comparison of grazing stresses with measured rates of primary production indicates that these large copepods were harvesting less than 5% of the daily phytoplankton production. Comparison of the nitrogen excretion rates with the amounts of excreted nitrogen in the water column indicates that less than 3% of the ambient excretory nitrogen was produced daily by these copepods. The importance of the abundant small zooplankton in the system is suggested.

  15. Astronomically forced western African (21°N-20°S) rainfall variations during the Last Interglacial

    Science.gov (United States)

    Govin, Aline; Varma, Vidya; Prange, Matthias

    2013-04-01

    Many studies document an intensified NW African monsoon during the African Humid Period (11.5-5.5 ka) in response to increased summer insolation. Similarly, the particularly high summer insolation during the Last Interglacial (LIG, 129-116 ka) led to enhanced North African rainfall and a "green Sahara". Although this pluvial period seemed to facilitate the migration of modern humans out of Africa, the precise evolution of African wet conditions during the LIG remains unknown. Here we aim to document the evolution of western African precipitation during the LIG and identify the climate forcing associated. We use the major element compositions of nine marine sediment cores located along the W African margin (21°N-20°S) in order to characterize the terrestrial climatic conditions in the region where terrigenous material originates and infer past western African precipitation changes. Geochemical data are compared to results from a transient simulation (130-115 ka) performed with the coupled ocean - atmosphere Community Climate System Model CCSM3 and forced by insolation variations only. Both geochemical and model data indicate humid conditions in NW Africa (9-21°N) between 127 and 122 ka, in response to the high summer insolation. The period of intensified NW African monsoon starts ~3 ka later in geochemical data (127 ka) than in the simulation (130 ka). This result suggests that the persistent melting of northern ice sheets and associated cooling at the beginning of the LIG delayed the orbitally-induced intensification of the NW African monsoon. In addition, geochemical and model data indicate a slight precipitation increase in equatorial Africa throughout the LIG, in response to the small increase in annual insolation induced by the obliquity decrease. At ~5-10°S, sediment cores and model results document a small decrease in annual precipitation that is consistent with increasing sea level pressure in southern Africa during the LIG. This pattern seems to follow

  16. On the Hiatus in the Acceleration of Tropical Upwelling Since the Beginning of the 21st Century

    Science.gov (United States)

    Aschmann, J.; Burrows, J. P.; Gebhardt, C.; Rozanov, A.; Hommel, R.; Weber, M.; Thompson, A. M.

    2014-01-01

    Chemistry-climate models predict an acceleration of the upwelling branch of the Brewer-Dobson circulation as a consequence of increasing global surface temperatures, resulting from elevated levels of atmospheric greenhouse gases. The observed decrease of ozone in the tropical lower stratosphere during the last decades of the 20th century is consistent with the anticipated acceleration of upwelling. However, more recent satellite observations of ozone reveal that this decrease has unexpectedly stopped in the first decade of the 21st century, challenging the implicit assumption of a continuous acceleration of tropical upwelling. In this study we use three decades of chemistry transport-model simulations (1980-2013) to investigate this phenomenon and resolve this apparent contradiction. Our model reproduces the observed tropical lower stratosphere ozone record, showing a significant decrease in the early period followed by a statistically robust trend-change after 2002. We demonstrate that this trend-change is correlated with corresponding changes in the vertical transport and conclude that a hiatus in the acceleration of tropical upwelling occurred during the last decade.

  17. The Impact of Reduced SST Gradients and MJO-like Tropical Variability on Surface Winds at Midlatitude Upwelling Sites

    Science.gov (United States)

    Arnold, N. P.; Tziperman, E.

    2012-12-01

    Sediment core data suggest that sea surface temperatures (SST) at present-day sites of wind-driven coastal upwelling were much warmer during the early Pliocene, and only cooled gradually over the last 3-4My. Several hypotheses have been advanced to explain the Pliocene warm anomalies, including a globally deeper thermocline and weaker upwelling-favorable winds, but it remains unclear if the SST anomalies reflect differences in upwelling intensity or in subsurface water properties. In this study we explore two factors which might affect the surface winds responsible for midlatitude upwelling: (1) differences in the large-scale SST distribution and their impact on the atmospheric general circulation, and (2) teleconnections from changes in tropical convective variability. We run the NCAR Community Atmosphere Model with a spectrum of meridional and zonal surface temperature gradients, ranging from a modern climatology to a low-gradient state reminiscent of the early Pliocene. A prescribed forcing is then added to the model to stimulate tropical convective variability based on the observed Madden-Julian Oscillation (MJO), which can impact midlatitude sites by exciting atmospheric Rossby waves. Quantitative metrics of along-shore wind stress at several midlatitude sediment core sites are presented as a function of the prescribed SST gradients and tropical forcing amplitude.

  18. How depositional conditions control input, composition, and degradation of organic matter in sediments from the Chilean coastal upwelling region

    DEFF Research Database (Denmark)

    Niggemann, Jutta; Ferdelman, Timothy G.; Lomstein, Bente Aagaard

    2007-01-01

    the Chilean coastal upwelling system and have an extended oxygen minimum zone in the water column. However, the northern site (23°S) borders the Atacama Desert, while the southern site (36°S) has a humid hinterland. Eight surface sediment cores (up to 30 cm long) from water depths of 126‑1350 m were...

  19. Dynamics of oxygen depletion in the nearshore of a coastal embayment of the southern Benguela upwelling system

    CSIR Research Space (South Africa)

    Pitcher, GC

    2014-04-01

    Full Text Available Acquisition of high resolution time series of water column and bottom dissolved oxygen (DO) concentrations inform the dynamics of oxygen depletion in St Helena Bay in the southern Benguela upwelling system at several scales of variability. The bay...

  20. Post-Pan-African tectonic evolution of South Malawi in relation to the Karroo and recent East African rift systems

    Science.gov (United States)

    Castaing, C.

    1991-05-01

    Structural studies conducted in the Lengwe and Mwabvi Karroo basins and in the basement in South Malawi, using regional maps and published data extended to cover Southeast Africa, serve to propose a series of geodynamic reconstructions which reveal the persistence of an extensional tectonic regime, the minimum stress σ3 of which has varied through time. The period of Karroo rifting and the tholeiitic and alkaline magmatism which terminated it, were controlled by NW-SE extension, which resulted in the creation of roughly NE-SW troughs articulated by the Tanganyika-Malawi and Zambesi pre-transform systems. These were NW-SE sinistral-slip systems with directions of movement dipping slightly to the Southeast, which enabled the Mwanza fault to play an important role in the evolution of the Karroo basins of the Shire Valley. The Cretaceous was a transition period between the Karroo rifting and the formation of the Recent East African Rift System. Extension was NE-SW, with some evidence for a local compressional episode in the Lengwe basin. Beginning in the Cenozoic, the extension once more became NW-SE and controlled the evolution in transtension of the Recent East African Rift System. This history highlights the major role of transverse faults systems dominated by strike-slip motion in the evolution and perpetuation of the continental rift systems. These faults are of a greater geological persistence than the normal faults bounding the grabens, especially when they are located on major basement anisotropies.

  1. Resolving Phytoplankton Diversity, Growth and Mortality in an Eastern Boundary Upwelling System

    Science.gov (United States)

    Worden, A. Z.; Jimenez, V.

    2015-12-01

    Eastern Boundary Upwelling Systems are highly productive marine regions. Primary production in these systems is performed by a complex array of phytoplankton, many of which are in the picophytoplankton size class (≤2 µM diameter). Because morphological features in these small cells are limited and difficult to visualize, our understanding of their distributions and activities is poor. Even at broad levels, such as cyanobacteria versus picoeukaryotes, contributions to primary production are not well resolved. However, laboratory experiments show that the biology of species within each of these groups is highly differentiated. Hence, to develop predictive understanding of primary production in these regions, its transfer to higher trophic levels and key export terms, it is necessary to understand which taxa are present and their in situ activities. Here, we report results from multi-year expeditions along a transect (Line 67) that extends from Monterey Bay, California (USA) to the North Pacific Gyre and is also part of the California Cooperative Oceanic Fisheries Investigations (CalCOFI). We explore the diversity of phytoplankton in the coastal zone, the upwelling-transition zone and subtropical gyre-like waters to gain insights into controls acting on primary producers in each. Our Line 67 results on primary producer dynamics are underlain by a comprehensive suite of genomic, metagenomic, metatranscriptomic and molecular analyses. Statistical approaches have helped us to define temperature maxima, nutrient thresholds and important remineralization processes that influence dominance by specific eukaryotic algae. First-ever species-specific growth and grazing mortality rates provide an unprecedented view of contributions to biomass production and its consumption by higher trophic levels. Finally, by investigating the entire microbial community including heterotrophic taxa, we are able to establish baselines for community interactions that are affiliated with

  2. Are large macroalgal blooms necessarily bad? Nutrient impacts on seagrass in upwelling-influenced estuaries.

    Science.gov (United States)

    Hessing-Lewis, Margot L; Hacker, Sally D; Menge, Bruce A; McConville, Sea-oh; Henderson, Jeremy

    2015-07-01

    Knowledge of nutrient pathways and their resulting ecological interactions can alleviate numerous environmental problems associated with nutrient increases in both natural and managed systems. Although not unique, coastal systems are particularly prone to complex ecological interactions resulting from nutrient inputs from both the land and sea. Nutrient inputs to coastal systems often spur ulvoid macroalgal blooms, with negative consequences for seagrasses, primarily through shading, as well as through changes in local biogeochemistry. We conducted complementary field and mesocosm experiments in an upwelling-influenced estuary, where marine-derived nutrients dominate, to understand the direct and indirect effects of nutrients on the macroalgal-eelgrass (Zostera marina L.) interaction. In the field experiment, we found weak evidence that nutrients and/or macroalgal treatments had a negative effect on eelgrass. However, in the mesocosm experiment, we found that a combination of nutrient and macroalgal treatments led to strongly negative eelgrass responses, primarily via indirect effects associated with macroalgal additions. Together, increased total light attenuation and decreased sediment oxygen levels were associated with larger effects on eelgrass than shading alone, which was evaluated using mimic algae treatments that did not alter sediment redox potential. Nutrient addition in the mesocosms directly affected seagrass density; biomass, and morphology, but not as strongly as macroalgae. We hypothesize that the contrary results from these parallel experiments are a consequence of differences in the hydrodynamics between field and mesocosm settings. We suggest that the high rates of water movement and tidal submersion of our intertidal field experiments alleviated the light reduction and negative biogeochemical changes in the sediment associated with macroalgal canopies, as well as the nutrient effects observed in the mesocosm experiments. Furthermore, adaptation

  3. Disruption of the PV-PPV Phase Transition by a Dome-like Upwelling Beneath Alaska

    Science.gov (United States)

    Sun, D.; Helmberger, D. V.; Miller, M. S.

    2014-12-01

    The lowermost mantle region, D", represents one of the most dramatic thermal andcompositional layers within our planet. Global tomographic models display relatively fast patchsalong the circum-Pacific which is generally attributed to slab-debris. Such cold patches interactwith the PV-PPV phase boundary to generate particularly strong heterogeneity at their edges.Most seismic observations for the D" come from the lower mantle S wave triplication (Scd).However, the sampling regions concentrated beneath Central America, where intensive studies,including migration methods and array analysis, have been accomplished. Beneath the centralAmerica, the D" can have a step variation of ~ 100 km, which argues strong lateral temperaturevariations or possible chemical variations. However, the common used ray paths between SouthAmerican events and seismic stations in US sample such sharp boundary azimuthally, whichmake the modeling difficult. Here, we exploit the USArray waveform data to examine one ofthese sharp transitions beneath Alaska. From west to east beneath Alaska, we observed threedifferent type of D": West region with strong Scd requiring sharp δVS = 2% increase;Middle region with no clear Scd indicating lack of D"; East region with strong Scd requiring gradientδVS increase. To explain such strong lateral variation, chemical variations must be involved. Wesuggested that West region represents a normal mantle. In contrast, the east region is dominated bysubducted slab. At the Middle region, we discovered a strong upwelling structure that disrupts the phaseboundary. A distinct pattern of travel time delays, waveform distortions, and amplitude patternsreveal a circular anomaly about 5° across which can be modeled synthetically as a dome about400 km high with a shear velocity reduction of ~5%. Geodynamic modeling indicates thatthis structure could be the base of an upwelling and/or a hot Fe-rich oxide hill.

  4. Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems

    Directory of Open Access Journals (Sweden)

    V. Rossi

    2009-08-01

    Full Text Available Eastern Boundary Upwelling Systems (EBUS are characterized by a high productivity of plankton associated with large commercial fisheries, thus playing key biological and socio-economical roles. Since they are populated by several physical oceanic structures such as filaments and eddies, which interact with the biological processes, it is a major challenge to study this sub- and mesoscale activity in connection with the chlorophyll distribution. The aim of this work is to make a comparative study of these four upwelling systems focussing on their surface stirring, using the Finite Size Lyapunov Exponents (FSLEs, and their biological activity, based on satellite data. First, the spatial distribution of horizontal mixing is analysed from time averages and from probability density functions of FSLEs, which allow us to divide each areas in two different subsystems. Then we studied the temporal variability of surface stirring focussing on the annual and seasonal cycle. We also proposed a ranking of the four EBUS based on the averaged mixing intensity. When investigating the links with chlorophyll concentration, the previous subsystems reveal distinct biological signatures. There is a global negative correlation between surface horizontal mixing and chlorophyll standing stocks over the four areas. To try to better understand this inverse relationship, we consider the vertical dimension by looking at the Ekman-transport and vertical velocities. We suggest the possibility of a changing response of the phytoplankton to sub/mesoscale turbulence, from a negative effect in the very productive coastal areas to a positive one in the open ocean. This study provides new insights for the understanding of the variable biological productivity in the ocean, which results from both dynamics of the marine ecosystem and of the 3-D turbulent medium.

  5. Geochemistry and magnetic sediment distribution at the western boundary upwelling system of southwest Atlantic

    Science.gov (United States)

    Cruz, Anna P. S.; Barbosa, Catia F.; Ayres-Neto, Arthur; Munayco, Pablo; Scorzelli, Rosa B.; Amorim, Nívea Santos; Albuquerque, Ana L. S.; Seoane, José C. S.

    2018-02-01

    In order to investigate the chemical and magnetic characteristics of sediments of the western boundary upwelling system of Southwest Atlantic we analyzed magnetic susceptibility, grain size distribution, total organic carbon, heavy mineral abundance, Fe associated with Mössbauer spectra, and Fe and Mn of pore water to evaluate the deposition patterns of sediments. Four box-cores were collected along a cross-shelf transect. Brazil Current and coastal plume exert a primary control at the inner and outer shelf cores, which exhibited similar depositional patterns characterized by a high abundance of heavy minerals (mean 0.21% and 0.08%, respectively) and very fine sand, whereas middle shelf cores presented low abundances of heavy minerals (mean 0.03%) and medium silt. The inner shelf was dominated by sub-angular grains, while in middle and outer shelf cores well-rounded grains were found. The increasing Fe3+:Fe2+ ratio from the inner to the outer shelf reflects farther distance to the sediment source. The outer shelf presented well-rounded minerals, indicating abrasive processes as a result of transport by the Brazil Current from the source areas. In the middle shelf, cold-water intrusion of the South Atlantic Central Water contributes to the primary productivity, resulting in higher deposition of fine sediment and organic carbon accumulation. The high input of organic carbon and the decreased grain size are indicative of changes in the hydrodynamics and primary productivity fueled by the western boundary upwelling system, which promotes loss of magnetization due to the induction of diagenesis of iron oxide minerals.

  6. Linking benthic community structure to terrestrial runoff and upwelling in the coral reefs of northeastern Hainan Island

    Science.gov (United States)

    Li, Xiubao; Wang, Daoru; Huang, Hui; Zhang, Jing; Lian, Jiansheng; Yuan, Xiangcheng; Yang, Jianhui; Zhang, Guoseng

    2015-04-01

    Near-shore coral reefs in northeastern Hainan Island are close to river mouths and aquaculture ponds, and also located at the center of the Qiongdong Upwelling (QDU). However, it is still unclear how terrestrial runoff and upwelling influence the community composition and spatial distribution of the benthos. During three cruises in 2010 and 2011 in Wenchang, northeastern Hainan Island, we determined a subset of environmental parameters in seawater (e.g. temperature, salinity, DO, dissolved inorganic nutrient (DIN), turbidity and transparency) and macroalgal δ15N and investigated the benthic communities (e.g. live coral cover, coral species richness, juvenile coral density, macroalgal cover and coverage of calcified algae) by video transect and visual census techniques at 10 stations (i.e. 1S-6D). The results showed that the QDU has influenced the reef waters in Wenchang. In 2011, the upwelling started in early May, peaked in July and disappeared in September and most upwelling events lasted for 1-2 weeks between May and July. The results also demonstrated that the reef water was nutrient enriched. Stations close to the river mouth and aquaculture ponds had higher levels of DIN and a higher percentage of ammonia in DIN, and there was consistently lower live coral cover, juvenile coral density and higher macroalgal cover. At some stations in this study, live coral cover was negatively correlated with macroalgal cover (i.e. 2S-6D). Live coral cover, species richness, and juvenile coral density all increased with the distance away from the river outlet and decreased with the rise of DIN. These results suggest that terrestrial runoff and upwelling stimulate nutrient enrichment, and that overgrowing macroalgae has an important influence on the coral communities in northeastern Hainan Island.

  7. Variability of coastal water hydrodynamics in the southern Baltic - hindcast modelling of an upwelling event along the Polish coast

    Directory of Open Access Journals (Sweden)

    Andrzej Jankowski

    2002-12-01

    Full Text Available This paper presents the results of an attempt to reproduce, with theaid of a numerical circulation model, the hydrological conditions observedin the coastal area of the southern Baltic in September 1989.A large fall in surface layer seawater temperature was recordedin September 1989 at two coastal stations in the vicinity ofKolobrzeg and Wladyslawowo. This upwelling-like phenomenon was assumed tobe related to the specific anemobaric situation in September 1989,however typical of this phenomenon to occur along the Polish Baltic coast(Malicki & Mietus 1994. A three-dimensional (3-D sigma-coordinatebaroclinic model of the Baltic Sea, with a horizontal resolution of~5 km and 24 sigma-levels in the vertical, was applied to investigatewater circulation and thermohaline variability. Hindcastnumerical simulation showed that the model provided a good reproductionof the temporal history of the surface seawater temperature and theduration of the upwelling-like fall, but that the model results wereunderestimated. The maxima of this large fall in the surface layertemperature at both coastal stations are closely related to the phase ofchange of the upwelling-favourable wind direction to the opposite one.The results of simulation runs showed details of upwelling developmentdue to wind field fluctuations in time and differences in shaping thetemperature and current patterns in conjunction with the variations intopography and coastline features in some areas along the Polish coast.Two different hydrodynamic regimes of water movements along the coastresulting from topographical features (the Slupsk Bank can be distinguished.From the model simulation the specific conditions for the occurrence anddevelopment of upwelling at the eastern end of the Polish coast(in the vicinity of Wladyslawowo can be deduced.

  8. The Benguela upwelling related to the Miocene cooling events and the development of the Antarctic Circumpolar Current: Evidence from calcareous dinoflagellate cysts

    Science.gov (United States)

    Heinrich, Sonja; Zonneveld, Karin A. F.; Bickert, Torsten; Willems, Helmut

    2011-09-01

    Sediment samples from ODP Site 1085 were investigated in order to obtain more information on the initiation and development of the Benguela upwelling system during the middle and upper Miocene. In particular, our intent was to establish the causes of the upwelling as well as the response of the upwelling regime to the development of the Antarctic Circumpolar Current. Based on changes in the calcareous dinoflagellate cyst association, we found an initial increase of the dinoflagellate cyst productivity, probably related to the initiation of upwelling about 11.8 Ma ago. Two distinct increases in cyst productivity in conjunction with temperature decreases of the upper water masses reflect upwelling pulses off Namibia and occur at the end of the Miocene cooling events Mi5 (about 11.5 Ma) and Mi6 (about 10.5 Ma). Both cooling events are associated with an ice volume increase in Antarctica and are thought to have led to an increase in southeasterly winds, possibly causing these two upwelling pulses. We demonstrate a decrease in dinoflagellate cyst productivity and enhanced terrigenous input via the Orange River after the Mi5 event. At about 11.1 Ma, the dinoflagellate cyst productivity increases again. The polar cyst species Caracomia arctica occurs here for the first time. This implies an influence of subantarctic mode water and therefore a change in the quality of the upwelling water which allowed the Benguela upwelling to develop into modern conditions. From about 10.4 Ma, C. arctica forms a permanent part of the association, pointing to an establishment of the upwelling regime.

  9. African Environment

    African Journals Online (AJOL)

    Environmental Studies and Regional Planning Bulletin African Environment is published in French and English, and for some issues, in Arabic. (only the issue below has been received by AJOL). Vol 10, No 3 (1999). DOWNLOAD FULL TEXT Open Access DOWNLOAD FULL TEXT Subscription or Fee Access. Table of ...

  10. Mechanisms of the intensification of the upwelling-favorable winds during El Niño 1997-1998 in the Peruvian upwelling system

    Science.gov (United States)

    Chamorro, Adolfo; Echevin, Vincent; Colas, François; Oerder, Vera; Tam, Jorge; Quispe-Ccalluari, Carlos

    2018-01-01

    The physical processes driving the wind intensification in a coastal band of 100 km off Peru during the intense 1997-1998 El Niño (EN) event were studied using a regional atmospheric model. A simulation performed for the period 1994-2000 reproduced the coastal wind response to local sea surface temperature (SST) forcing and large scale atmospheric conditions. The model, evaluated with satellite data, represented well the intensity, seasonal and interannual variability of alongshore (i.e. NW-SE) winds. An alongshore momentum budget showed that the pressure gradient was the dominant force driving the surface wind acceleration. The pressure gradient tended to accelerate the coastal wind, while turbulent vertical mixing decelerated it. A quasi-linear relation between surface wind and pressure gradient anomalies was found. Alongshore pressure gradient anomalies were caused by a greater increase in near-surface air temperature off the northern coast than off the southern coast, associated with the inhomogeneous SST warming. Vertical profiles of wind, mixing coefficient, and momentum trends showed that the surface wind intensification was not caused by the increase of turbulence in the planetary boundary layer. Moreover, the temperature inversion in the vertical mitigated the development of pressure gradient due to air convection during part of the event. Sensitivity experiments allowed to isolate the respective impacts of the local SST forcing and large scale condition on the coastal wind intensification. It was primarily driven by the local SST forcing whereas large scale variability associated with the South Pacific Anticyclone modulated its effects. Examination of other EN events using reanalysis data confirmed that intensifications of alongshore wind off Peru were associated with SST alongshore gradient anomalies, as during the 1997-1998 event.

  11. African Journals Online: Central African Republic

    African Journals Online (AJOL)

    African Journals Online: Central African Republic. Home > African Journals Online: Central African Republic. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This ...

  12. Sea surface temperature changes during May and August in the western Arabian Sea over the last 22 kyr: Implications as to shifting of the upwelling season

    Digital Repository Service at National Institute of Oceanography (India)

    Godad, S.P.; Naidu, P.D.; Malmgren, B.A.

    Naidu 1** ., Bjorn Malmgren 2 1. National Institute of Oceanography, Dona Paula 403 004, Goa, India. 2. Solvagen 17, SE – 761 64 Norrtalje, Sweden. Abstract In the modern day the highest seasonal sea surface temperature (SST) difference has... by the upwelling indices record (Naidu and Malmgren, 1996), August SST was higher than modern day SST at this site indicating two features: i) the intensity of upwelling during August was not as intense as that in the modern day, ii) the upwelling must be more...

  13. Dome-like low velocity upwelling in D" beneath Alaska imaged with USArray data

    Science.gov (United States)

    Sun, Daoyuan; Miller, Meghan S.; Helmberger, Don

    2015-04-01

    The lowermost mantle region, D", represents one of the most dramatic thermal and compositional layers within our planet. Global tomographic models display relatively fast patches along the circum-Pacific which are generally attributed to slab-related debris. Most seismic observations for the D" boundary layer come from the lower mantle S wave triplication (Scd). However, the most sampled regions are concentrated beneath Central America, where intensive studies, including migration methods and array analysis, have been accomplished. Beneath Central America, the D" can have a step variation of ~100 km, which argues strong lateral temperature variations or possible chemical variations. However, the commonly used ray paths between South American events and seismic stations in North America sample this sharp boundary azimuthally, which is difficult to model. Here, we exploit the USArray waveform data to examine a sharp transition beneath Alaska. From west to east beneath Alaska, we observe three different types of structures in the D" layer: in the western region we observed a strong Scd phase, which requires a sharp δVS = 2% increase; in the middle region there is no clear Scd phase indicating no D" layer; in the eastern region we observe a strong Scd phase requiring a positive gradient δVS. To explain such strong lateral differences in seismic velocity, we propose a chemical variation. We suggest that the western region represents a "normal" lowermost mantle. In contrast, the eastern region has fast velocities, which appears to influenced by the subducted Pacific slab. In the middle region, we interpret an upwelling structure that disrupts the phase boundary. This is based upon observations of a distinct pattern of travel time delays, waveform distortions, and amplitude patterns which reveal a circular anomaly about 5° across which can be modeled synthetically as a dome about 400 km high with a low shear velocity reduction of ~5%. Numerical modeling indicates that

  14. The Mono Arch, eastern Sierra region, California: Dynamic topography associated with upper-mantle upwelling?

    Science.gov (United States)

    Jayko, A.S.

    2009-01-01

    A broad, topographic flexure localized east of and over the central and southern Sierra Nevada, herein named the Mono Arch, apparently represents crustal response to lithospheric and/or upper-mantle processes, probably dominated by mantle upwelling within the continental interior associated Pacific-North American plate-boundary deformation. This zone of flexure is identified through comparison between the topographic characteristics of the active Cascade volcanic arc and backarc regions with the analogous former arc and backarc in the Sierra Nevada and eastern Sierra Nevada. Serial topographic profiles measured normal to the modern Cascade backarc reveal an accordance of topographic lows defined by valley floors with an average minimum elevation of ???1400-1500m for over 175km to the southeast. Although the accordance drops in elevation slightly to the south, the modern Cascade backarc region is remarkably level, and is characterized by relief up to ???750m above this baseline elevation. By contrast, serial topographic profiles over the former arc and backarc transitions of the eastern Sierra region exhibit a regional anticlinal warping defined by accordant valley floors and by a late Miocene-early Pliocene erosion surface and associated deposits. The amplitude of this flexure above regionally flat baseline elevations to the east varies spatially along the length of the former Sierran arc, with a maximum of ???1000m centred over the Bridgeport Basin. The total zone of flexure is approximately 350km long N-S and 100km wide E-W, and extends from Indian Wells Valley in the south to the Sonora Pass region in the north. Previous geophysical, petrologic, and geodetic studies suggest that the Mono Arch overlies a zone of active mantle upwelling. This region also represents a zone crustal weakness formerly exploited by the middle-to-late Miocene arc and is presently the locus of seismic and volcanic activities. This seismic zone, which lies east of the Sierra Nevada block

  15. Impacts of Evolutionary History on Endangerment in a Changing Climate: Miocene upwelling, Holocene Pluvial Cycles and Endemics at the Mouth of the Colorado River.

    Science.gov (United States)

    Jacobs, D. K.

    2006-12-01

    The environmental conditions communities experienced during their diversification and recent geologic history informs us as to which environmental changes are most likely to impact species in those communities. Three examples follow: 1) Recent compilation of molecular and paleontological data document that higher aspects of the trophic chain in the Pacific Northwest, including the salmon genus Onchoyrhynchus, alcid birds (Auks & Puffins) and crabs of the genus Cancer speciated dramatically in response to enhanced upwelling of the mid Miocene (Jacobs et al. 2004). Consistent with this evolutionary origin, population dynamics and endangerment of these taxa are associated with the changing productivity regime of the Pacific as well as more direct human impacts. 2) Pluvials in the Eurasian and African continent respond to the precession cycle, as a result wetland habitats were much more expansive in the early and middle Holocene. Late Holocene wetland habitat contraction combines with increasing anthropogenic manipulation of these cyclically limited hydrologic resources to yield a suite of endangered taxa across these continents as is statistically documented by analysis of Redbook data. 3) Our recent work documents the evolution of endemic fish and Molluscan taxa in association with the Colorado River Delta. These endemic taxa are then vulnerable to the to impacts on the Colorado Delta where anthropogenic use of water resources combine with the threat of climate provide combined threats to this ecosystem. The Environmental/Evolutionary history of lineages clearly has strong implications for how anthropogenic changes impacts and endangers those lineages. Jacobs D.K. et al. Annu. Rev. Earth Planet. Sci. 2004. 32:601 52

  16. Association of Sub-continental and Asthenosphere related Volcanism in NW Iran,Implication forMantle thermal perturbation induced by slab break off and collision event

    Science.gov (United States)

    Jahangiri, A.

    2017-12-01

    Cenozoic magmatic rocks occur extensively in the north of the Zagros suture zone and constitute a significant component of the continental crust in this segment of the Alpine-Himalayan orogenic belt. They range in age from Eocene to quaternary. Miocene to Plio-Quaternary volcanism with post-collisional related significant is covered vast areas in NW Iran. These volcanic rocks can be divided into three different sub-groups on the basis of their mineralogy, geochemistry and magma sources including: 1. alkaline leucite-bearing mafic rocks, which are characterized with high ratios of K2O/Na2O, high content LILE and low HFS elements like Ti, Nb and Ta. They are display fractionated REE patterns and based on different discrimination diagrams show similarity with subduction related magmas. 2- Olivine basalt to trachy-basaltic samples which shows similarity to within plate basalts with high content of TiO2, Nb, Ta and fractionated REE pattern. However, compared with a global average of OIB, they are display slightly higher LIL elements and lower HFS elements concentrations, features that resemble to the arc magmas and suggest that the source of the magmas may have been contaminated by slab-derived fluids. These rocks have simple mineralogical composition with plagioclase, clinopyroxene and olivine. 3- Dominant dacitic volcanic rocks with adakitic geochemical characteristics such as highly fractionate REE pattern and high Sr/Y ratio. Generation of adakitic magmas can be related to increased temperatures in the subduction zone due to mantle upwelling and slab tearing. Subsequent asthenospheric upwelling could be caused direct melting of sub-continental mantle to produce the alkaline magmas, with high contents of K2O, MgO and volatile rich phase's potassic magmas that led to crystallization of leucite, phlogopite, apatite and olivine in studied samples. Rupture of the continental lithosphere by strike-slip-related transtensional deformation might have caused decompression

  17. Support Vector Machine-based method for predicting Pseudo-nitzschia spp. blooms in coastal waters (Galician rias, NW Spain)

    Science.gov (United States)

    González Vilas, Luis; Spyrakos, Evangelos; Torres Palenzuela, Jesus M.; Pazos, Yolanda

    2014-05-01

    Phytoplanktonic blooms in the coastal embayments (rias) at the NW part of Spain were mentioned for the first time in 1918 and since then they have been associated numerous times with negatives impacts to a very important economic activity in the area, mussel production. In this study, eight years of Pseudo-nitzschia spp. abundance and associated meteorological and oceanographic data were used to develop and validate support vector machine (SVM) models for the prediction of these diatoms. SVM were used to identify presence/below low detection limit, bloom/no bloom conditions of Pseudo-nitzschia spp. and finally to predict blooms due to these diatoms in the coastal systems of the Galician rias. The best SVM models were selected on the basis of C and γ parameters and their performance was evaluated in terms of accuracy and kappa statistics (κ). Regarding the presence/below low detection limit, bloom/no bloom models the best results in the validation dataset were achieved using all the variables: ria code, day of the year, temperature, salinity, upwelling indices and bloom occurrence in previous weeks. The best performing models were also tested in an independent dataset from the study area, where they showed high overall accuracy (78.53-82.18%), κ values (0.77-0.81) and true positive rates (62.60-78.18). In these models the bloom occurrence in previous weeks was identified as a key parameter to the prediction performance. In this paper, toxic Pseudo-nitzschia blooms could not be predicted due to limited information on toxin concentration and species composition. Nevertheless, this study demonstrates that the approach followed here is capable for high predictive performance which could be of great aid in the monitoring of algal blooms and offer valuable information to the local shellfish industry. The reliable prediction of categorical Pseudo-nitzschia abundances using variables that are operationally determined or short-term predicted could provide early warning of

  18. African Journals Online (AJOL)

    African Journals Online (AJOL)

    ChemSearch Journal. Vol 48, No 3 (2018). South African Journal of Animal Science. Vol 8, No 1 (2018). African Journal of Chemical Education. Vol 48, No 2 (2018). South African Journal of Animal Science. Vol 48, No 1 (2018). South African Journal of Animal Science. Vol 7, No 1 (2018). South African Journal of Geomatics.

  19. Successional trajectory of the fouling community on a tropical upwelling ecosystem in southeast Rio de Janeiro, Brazil

    Directory of Open Access Journals (Sweden)

    Bruno Pereira Masi

    2015-06-01

    Full Text Available Abstract The present study describes the successional trajectory of the fouling community in the upwelling region of Cabo Frio in southeastern Rio de Janeiro, Brazil. For 12 months, five PVC panels were sampled monthly by underwater photography to record the percent cover of fouling organisms, which allowed for the evaluation of the successional process through functional groups. The variability in the composition of the fouling community increased throughout the successional trajectory, creating a mosaic pattern. The identification of two associations after a year of observation, with one characterized by filamentous algae, Hydrozoa and Cirripedia and another mainly by articulated calcareous algae, shows that divergent trajectories can be observed even under the same environmental conditions. As an important seasonal factor of the local oceanographic characteristics, the upwelling events allowed for an environmental heterogeneity, and rejecting the classic orderly and directional succession model.

  20. Transport of terrigenous polycyclic aromatic hydrocarbons affected by the coastal upwelling in the northwestern coast of South China Sea.

    Science.gov (United States)

    Ya, Miaolei; Wu, Yuling; Li, Yongyu; Wang, Xinhong

    2017-10-01

    Coastal upwelling prevails in the coast of Hainan Island, the northern South China Sea (SCS) during summer. We studied the influences of the upwelling on the horizontal and vertical transport of terrigenous polycyclic aromatic hydrocarbons (PAHs). PAHs in dissolved and suspended particulate phase of water samples were determined in the upper (depth  10 m). PAH levels decreased sharply from inshore to offshore to open sea. The results showed that terrestrial input was the main source of coastal PAHs. Perylene, an important indicator of land plant-derived PAH, showed the significant correlation with PAHs (p rising PAHs with their subsequent transport offshore and settling in the adjacent open sea. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Influence of ocean acidification and deep water upwelling on oligotrophic plankton communities in the subtropical North Atlantic

    DEFF Research Database (Denmark)

    Taucher, Jan; Bach, Lennart T.; Boxhammer, Tim

    2017-01-01

    and successfully simulated a deep water upwelling event that induced a pronounced plankton bloom. Our study revealed significant effects of OA on the entire food web, leading to a restructuring of plankton communities that emerged during the oligotrophic phase, and was further amplified during the bloom......Oceanic uptake of anthropogenic carbon dioxide (CO2) causes pronounced shifts in marine carbonate chemistry and a decrease in seawater pH. Increasing evidence indicates that these changes-summarized by the term ocean acidification (OA)-can significantly affect marine food webs and biogeochemical......, which regularly occur in response to upwelling of nutrient-rich deep water in the study region. Therefore, we specifically developed a deep water collection system that allowed us to obtain 85 m3 of seawater from 650 m depth. Thereby, we replaced 20% of each mesocosm's volume with deep water...

  2. Sporadic Groundwater Upwelling in Deep Martian Craters: Evidence for Lacustrine Clays and Carbonates

    Science.gov (United States)

    Michalski, J. R.; Rogers, A. D.; Wright, S. P.; Niles, P.; Cuadros, J.

    2012-01-01

    While the surface of Mars may have had an active hydrosphere early in its history [1], it is likely that this water retreated to the subsurface early on due to loss of the magnetic field and early atmosphere [2]. This likely resulted in the formation of two distinct aqueous regimes for Mars from the Late Noachian onward: one dominated by redistribution of surface ice and occasional melting of snow/ice [3], and one dominated by groundwater activity [4]. The excavation of alteration minerals from deep in the crust by impact craters points to an active, ancient, deep hydrothermal system [5]. Putative sapping features [6] may occur where the groundwater breached the surface. Upwelling groundwater may also have played a critical role in the formation of massive, layered, cemented sediments in Sinus Meridiani [7,8], in the Valles Marineris [9], and possibly in Gale Crater [10], where the Curiosity Rover will land later this year. Understanding the past distribution, geochemistry, and significance of groundwater on Mars is critical to untangling the origins of deep alteration minerals, Hesperian sulfate deposits, and crater fill deposits at Gale Crater or in other locations.

  3. Mantle upwelling beneath Madagascar: evidence from receiver function analysis and shear wave splitting

    Science.gov (United States)

    Paul, Jonathan D.; Eakin, Caroline M.

    2017-07-01

    Crustal receiver functions have been calculated from 128 events for two three-component broadband seismomenters located on the south coast (FOMA) and in the central High Plateaux (ABPO) of Madagascar. For each station, crustal thickness and V p / V s ratio were estimated from H- κ plots. Self-consistent receiver functions from a smaller back-azimuthal range were then selected, stacked and inverted to determine shear wave velocity structure as a function of depth. These results were corroborated by guided forward modeling and by Monte Carlo error analysis. The crust is found to be thinner (39 ± 0.7 km) beneath the highland center of Madagascar compared to the coast (44 ± 1.6 km), which is the opposite of what would be expected for crustal isostasy, suggesting that present-day long wavelength topography is maintained, at least in part, dynamically. This inference of dynamic support is corroborated by shear wave splitting analyses at the same stations, which produce an overwhelming majority of null results (>96 %), as expected for vertical mantle flow or asthenospheric upwelling beneath the island. These findings suggest a sub-plate origin for dynamic support.

  4. Distribution of zooplankton biomass and potential metabolic activities across the northern Benguela upwelling system

    Science.gov (United States)

    Fernández-Urruzola, I.; Osma, N.; Packard, T. T.; Gómez, M.; Postel, L.

    2014-11-01

    The distribution of zooplankton biomass and potential metabolic rates, in terms of electron transport system (ETS) and glutamate dehydrogenase (GDH), were analyzed along a cross-shelf transect in waters off Namibia. The highly variable dynamics of upwelling filaments promoted short-term fluctuations in the zooplankton biomass and metabolism. Maximum values were characteristically found over the shelf-break, where zooplankton biomass as dry mass (DM) reached peaks of 64.5 mg m- 3 within the upper 200 m in late August. Two weeks later, the zooplankton-DM decreased by more than a third (19 mg DM m- 3). Zooplankton potential respiration and NH4+ excretion averaged 234 μmol O2 m- 3 d- 1 and 169 μmol NH4+ m- 3 d- 1 in the Namibian shelf, respectively. High protein-specific ETS activities even in the low-chlorophyll waters outside the filament suggested a shift into greater omnivory seaward. In this light, zooplankton elemental and isotopic compositions were used to investigate the pelagic food web interactions. They evidenced spatial changes in the carbon resource for zooplankton as well as changes in the form of nitrogen that fueled the biological production in aging advected waters. Overall, both aspects of zooplankton metabolism impacted the primary productivity at a level less than 10% under all the different oceanographic conditions.

  5. Evidence of an intermittent deep equatorward flow in the Peru upwelling system

    Science.gov (United States)

    Pietri, Alice; Echevin, Vincent; Testor, Pierre; Chaigneau, Alexis; Mortier, Laurent; Grados, Carmen; Albert, Aurelie; Beguery, Laurent; Bhairy, Nagib

    2013-04-01

    In April-May 2010, 6 consecutive repeated cross-shore sections of ~100 km were occupied by a Slocum glider off the coast of Pisco (14°S) in the southernmost Peruvian upwelling region. The collected temperature and salinity data, acquired from the surface to 1000m depth and the depth-integrated velocity, estimated from the glider drift between two dives, are used to estimate absolute geostrophic alongshore velocities and study the spatio-temporal variability of the near-coastal circulation during a 5-week time period. Besides providing interesting information on the surface frontal jet and surfacing poleward undercurrent trapped on the continental shelf and slope, the glider data reveal the presence of a subsurface deep equatorward current. The dynamics and origin of this current, which can transport up to ˜2 Sv northward, are investigated using simulations from an eddy-resolving regional model (ROMS). This relatively strong equatorward subsurface current is associated with a poleward propagating coastal trapped wave of equatorial origin, with a strongly sheared vertical structure. A simple linear coastal wave model which successfully reproduces part of the observed vertical structure of the current, indicates that it corresponds to a third baroclinic mode of coastal wave.

  6. Tottori earthquakes and Daisen volcano: Effects of fluids, slab melting and hot mantle upwelling

    Science.gov (United States)

    Zhao, Dapeng; Liu, Xin; Hua, Yuanyuan

    2018-03-01

    We investigate the 3-D seismic structure of source areas of the 6 October 2000 Western Tottori earthquake (M 7.3) and the 21 October 2016 Central Tottori earthquake (M 6.6) which occurred near the Daisen volcano in SW Japan. The two large events took place in a high-velocity zone in the upper crust, whereas low-velocity (low-V) and high Poisson's ratio (high-σ) anomalies are revealed in the lower crust and upper mantle. Low-frequency micro-earthquakes (M 0.0-2.1) occur in or around the low-V and high-σ zones, which reflect upward migration of magmatic fluids from the upper mantle to the crust under the Daisen volcano. The nucleation of the Tottori earthquakes may be affected by the ascending fluids. The flat subducting Philippine Sea (PHS) slab has a younger lithosphere age and so a higher temperature beneath the Daisen and Tottori area, facilitating the PHS slab melting. It is also possible that a PHS slab window has formed along the extinct Shikoku Basin spreading ridge beneath SW Japan, and mantle materials below the PHS slab may ascend to the shallow area through the slab window. These results suggest that the Daisen adakite magma was affected by the PHS slab melting and upwelling flow in the upper mantle above the subducting Pacific slab.

  7. New method to estimate surface upwelling long-wave radiation from MODIS cloud-free data.

    Science.gov (United States)

    Wang, Chunlei; Tang, Bo-Hui; Huo, Xing; Li, Zhao-Liang

    2017-06-12

    As an important component in the surface radiation budget, surface upwelling longwave radiation (SULR) is an outcome of the land surface energy exchange and mainly represents the capability of thermal radiation from the surface of the Earth. Existing satellite-derived SULR products are too coarse to support high-resolution numerical models, and their accuracy needs to be improved. In this study, an equivalent temperature is introduced through which a "split-window" atmospheric correction algorithm is developed for MODIS data to estimate the instantaneous clear-sky SULR. It is a simple and feasible method that is particularly applicable to MODIS data to acquire relatively high precision SULR under clear skies from which qualified water vapor contents (WVC) and thermal channel brightness temperatures are available. The root mean square errors (RMSEs) are less than 13 W/m 2 for all WVC sub-ranges with the viewing zenith angle (VZA) less than 30°, or for all sub-ranges with the VZA less than 60° and the WVC less than 3.5 g/cm 2 . Also, applications and comparisons with the LST-emissivity method are made by using ground measurements which are collected from the network of surface radiation budget network data (SURFRAD) at the moment of MODIS overpass. Results show that the proposed model has high computational efficiency to estimate SULR from MODIS cloud-free data.

  8. Episodic upwelling and dust deposition as bloom triggers in low-nutrient, low-chlorophyll regions

    Science.gov (United States)

    Calil, Paulo H. R.; Doney, Scott C.; Yumimoto, Keiya; Eguchi, Kenta; Takemura, Toshihiko

    2011-06-01

    Summertime phytoplankton blooms in the oligotrophic North Pacific Ocean are supported by N2-fixing organisms that relieve the system of nitrate limitation. Phosphate and iron, however, limit their growth and need to be supplied for these organisms to thrive. We analyze two recent blooms in the region whose differences provide insight into their possible formation mechanisms. In 2008, a typical late summer bloom, with sporadic patches of higher-chlorophyll concentration, occurred near the island chain and the subtropical front. In 2010, an unusually large, contiguous bloom was observed in the western oligotrophic North Pacific, a region where blooms seldom, if ever, occur. Streaks of high chlorophyll in 2008 coincide with surface temperature fronts and regions of large horizontal stretching, as detected by Lagrangian diagnostics. Such regions are prone to the generation of vertical velocities via frontogenesis. Horizontal transport from upwelling regions or iron-rich island sediments is also important for the redistribution of nutrients. In the case of the 2010 bloom, we use a global aerosol transport model as well as space-borne lidar observations to argue that atmospheric dust deposition events prior to the bloom provided the necessary nutrient conditions for the growth of N2-fixing organisms. As sea surface temperature increased in the region, chlorophyll values increased significantly, showing that this bloom was likely a consequence of prior enrichment and that temperature is a key factor in bloom development in this important biome.

  9. CRED REA Fish Team Stationary Point Count Surveys at Necker, NW Hawaiian Islands, 2006

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Stationary Point Counts at 4 stations at each survey site were surveyed as part of Rapid Ecological Assessments (REA) conducted at 2 sites around Necker in the NW...

  10. CRED REA Coral Population Parameters at Necker, NW Hawaiian Islands (NWHI) in 2006

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Belt transects along 2 consecutively-placed, 25m transect lines were surveyed as part of Rapid Ecological Assessments conducted at 2 sites at Necker in the NW...

  11. CRED REA Algal Assessments at Kure Atoll, NW Hawaiian Islands in 2006

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Twelve quadrats were sampled along 2 consecutively-placed, 25m transect lines, as part of Rapid Ecological Assessments, conducted at 9 sites at Kure Atoll in the NW...

  12. CRED REA Fish Team Belt Transect Survey at Maro Reef, NW Hawaiian Islands, 2006

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Belt transects along 3 consecutively-placed, 25m transect lines were surveyed as part of Rapid Ecological Assessments conducted at 9 sites at Maro Reef in the NW...

  13. Population genetic structure of Orchesella cincta (Collembola; Hexapoda) in NW Europe, as revealed by microsatellite markers

    NARCIS (Netherlands)

    Wurff, van der A.W.G.; Gols, R.; Ernsting, G.; Straalen, van N.M.

    2005-01-01

    We studied genetic variation and population differentiation in the springtail Orchesella cincta L. An earlier approach, using allozymes, revealed extremely low variation among and within populations from NW Europe. Microsatellite marker analysis showed higher genetic variation than allozymes, and

  14. CRED REA Fish Team Stationary Point Count Surveys at Lisianski, NW Hawaiian Islands, 2006

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Stationary Point Counts at 4 stations at each survey site were surveyed as part of Rapid Ecological Assessments (REA) conducted at 9 sites around Lisianski in the NW...

  15. Alkaline phosphatase activity at the southwest coast of India: A comparison of locations differently affected by upwelling

    Science.gov (United States)

    Mamatha, S. S.; Malik, Ashish; Varik, Sandesh; Parvathi, V.; Jineesh, V. K.; Gauns, Mangesh U.; LokaBharathi, P. A.

    2015-01-01

    The realization of the potential importance of phosphorus (P) as a limiting nutrient in marine ecosystem is increasing globally. Hence, the contribution of biotic variables in mobilizing this nutrient would be relevant especially in productive coastal waters. As alkaline phosphatase activity (APA) indicates the status of P for primary production in aquatic environments, we asked the following question: is the level of APA indicative of P sufficiency or deficiency in coastal waters, especially, where upwelling is a regular phenomenon? Therefore, we have examined the total APA, chlorophyll a along with phosphatase producing bacteria (PPB) and related environmental parameters from nearshore to offshore in coastal waters off Trivandrum and Kochi regions differently affected by upwelling during the onset of monsoon. Off Trivandrum, APA in the offshore waters of 5-m layer at 2.23 μM P h- 1 was > 4 times higher than nearshore. Thus, low APA could be indicative of P sufficiency in coastal waters and higher activity suggestive of deficiency in offshore waters off Trivandrum. In contrast, there was less difference in APA between near and offshore surface waters off Kochi. Our results show that the regions differently affected by upwelling respond differently according to ambient P concentration, distance from shore or depth of water. These observations could apparently be applicable to other coastal systems as well, where gradients in upwelling and phosphate runoff have been noticed. Further studies on other transects would throw more light on the extent and direction of the relationship between APA and ambient P concentration. Such studies would help in understanding the level of control of this nutrient on the productivity of coastal waters.

  16. Inter-annual variability of the Pelagic-Benthic coupling in the upwelling system off central Chile

    Directory of Open Access Journals (Sweden)

    M. Graco

    2006-01-01

    Full Text Available The coastal region of central Chile (36° S is one of the most productive coastal systems, characterized by a marked seasonality in the upwelling regime, that brings subsurface waters rich in nutrient and poor in oxygen (ESSW into the euphotic zone. This oceanographic condition depends basically on the equatorward wind strength and is modified on different time scales, with the El Niño-Southern Oscillation (ENSO phenomenon as the main source of interannual variability in the Pacific Ocean. Here we present an effort to integrate physical and biogeochemical variability associated with in situ information and experiments at coastal stations off central Chile (36° S in order to improve the knowledge on the pelagic-benthic coupling in this upwelling system during the warm ENSO phase or El Niño. Carbon fluxes exported from the water column to the sediments and the ammonium exchange across the sediment-water interface are discussed together with oceanographic and benthic conditions. All measurements and estimations were carried out from May 1997 until April 2001 at two stations, one located inside Concepción Bay (~28 m depth, and the other on the continental shelf at ~36° S (~88 m depth. The results show that the pelagic and benthic systems are strongly coupled off central Chile (36° S. Oceanographic variability associated with upwelling events (seasonal scale and an El Niño event (interannual scale was observed. The carbon fluxes exported to the sediments, the benthic conditions (i.e., quantity and quality of the sediment organic matter, and the ammonium exchange across the sediment-water interface, responded to the seasonal regime of upwelling during non El Niño years as well as to the ENSO related oceanographic variability.

  17. Epidemiology of neosporosis in dairy cattle in Galicia (NW Spain).

    Science.gov (United States)

    González-Warleta, Marta; Castro-Hermida, José Antonio; Carro-Corral, Carmen; Cortizo-Mella, Javier; Mezo, Mercedes

    2008-01-01

    This comprehensive study of neosporosis in dairy cattle in Galicia (NW Spain) included: (1) a comparative study of three serological techniques for detection of Neospora caninum antibodies (direct agglutination, enzyme-linked immunosorbent assay and indirect immunofluorescence); (2) a cross-sectional serological survey in which 276 herds and 5,196 animals were tested; (3) a study of N. caninum antibody dynamics; (4) the isolation of viable tachyzoites of N. caninum. Data were analysed to determine the risk factors associated with the infection. A total of 219 herds (79.3%) and 816 heads of cattle (15.7%) were found to be seropositive. Seropositivity was higher on farms with dogs than on farms without dogs, and there was a negative correlation between the size of the herds and seroprevalence. Co-infection with Toxoplasma gondii increased the risk of seropositivity. Cows infected with N. caninum were 5.3 times more likely to abort than non-infected cows. The dynamics study showed an increase in anti-N. caninum antibody titres during the third trimester of pregnancy. Viable tachyzoites were isolated from brain samples. These results indicate that the economic impact of N. caninum is high in Galicia, and therefore, the inclusion of control measures for neosporosis in the official control health programmes is strongly recommended.

  18. Coastal upwelling linked to toxic Pseudo-nitzschia australis blooms in Los Angeles coastal waters, 2005-2007

    KAUST Repository

    Schnetzer, Astrid

    2013-06-10

    Harmful algal blooms dominated by the diatom Pseudo-nitzschia spp. have become a perennial but variable event within surface waters near the greater Los Angeles area. Toxic blooms during spring seasons from 2005 to 2007 varied strongly in their overall toxicity and duration. Differences in bloom dynamics were linked to differences in storm-induced river discharge following episodic rain events and coastal upwelling, both major coastal processes that led to the injection of nutrients into coastal surface waters. Heavy river runoff during early 2005, a record-rainfall year, favored a phytoplankton community mainly comprised of algal taxa other than Pseudo-nitzschia. The spring bloom during 2005 was associated with low domoic acid surface concentrations and minor contributions of (mainly) P. delicatissima to the diatom assemblage. In contrast, highly toxic P. australis-dominated blooms during spring seasons of 2006 and 2007 were linked to strong upwelling events. River discharge quotas in 2006 and 2007, in contrast to 2005, fell well below annual averages for the region. Surface toxin levels were linked to colder, more saline (i.e. upwelled) water over the 3-year study, but no such consistent relationship between domoic acid levels and other physiochemical parameters, such as macronutrient concentrations or nutrient ratios, was observed. © The Author 2013. Published by Oxford University Press. All rights reserved.

  19. Habitat coupling writ large: pelagic-derived materials fuel benthivorous macroalgal reef fishes in an upwelling zone.

    Science.gov (United States)

    Docmac, Felipe; Araya, Miguel; Hinojosa, Ivan A; Dorador, Cristina; Harrod, Chris

    2017-09-01

    Coastal marine upwelling famously supports elevated levels of pelagic biological production, but can also subsidize production in inshore habitats via pelagic-benthic coupling. Consumers inhabiting macroalgae-dominated rocky reef habitats are often considered to be members of a food web fuelled by energy derived from benthic primary production; conversely, they may also be subsidized by materials transported from pelagic habitats. Here, we used stable isotopes (δ 13 C, δ 15 N) to examine the relative contribution of pelagic and benthic materials to an ecologically and economically important benthivorous fish assemblage inhabiting subtidal macroalgae-dominated reefs along ~1,000 km of the northern Chilean coast where coastal upwelling is active. Fish were isotopically most similar to the pelagic pathway and Bayesian mixing models indicated that production of benthivorous fish was dominated (median 98%, range 69-99%) by pelagic-derived C and N. Although the mechanism by which these materials enter the benthic food web remains unknown, our results clearly highlight the importance of pelagic-benthic coupling in the region. The scale of this subsidy has substantial implications for our basic understanding of ecosystem functioning and the management of nearshore habitats in northern Chile and other upwelling zones worldwide. © 2017 by the Ecological Society of America.

  20. Fungal parasites infect marine diatoms in the upwelling ecosystem of the Humboldt current system off central Chile.

    Science.gov (United States)

    Gutiérrez, Marcelo H; Jara, Ana M; Pantoja, Silvio

    2016-05-01

    This is the first report of fungal parasitism of diatoms in a highly productive coastal upwelling ecosystem, based on a year-round time series of diatom and parasitic Chytridiomycota abundance in the Humboldt Current System off Chile (36°30.80'S-73°07.70'W). Our results show co-variation in the presence of Skeletonema, Thalassiosira and Chaetoceros diatoms with attached and detached chytrid sporangia. High abundance of attached sporangia was observed during the austral spring, coinciding with a predominance of Thalassiosira and Skeletonema under active upwelling conditions. Towards the end of austral spring, a decreasing proportion of attached sporangia was accompanied by a decline in abundance of Skeletonema and Thalassiosira and the predominance of Chaetoceros, suggesting specificity and host density dependence of chytrid infection. The new findings on fungal parasitism of diatoms provide further support for the inclusion of Fungi in the current model of the role played by the marine microbial community in the coastal ocean. We propose a conceptual model where Fungi contribute to controlling the dynamics of phytoplankton populations, as well as the release of organic matter and the transfer of organic carbon through the pelagic trophic web in coastal upwelling ecosystems. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  1. NW-trending fault structures. A key factor to uranium mineralization in Egongshan volcanic basin

    International Nuclear Information System (INIS)

    Zhang Wanliang

    1996-01-01

    Influenced by the Tancheng-Lujiang fault system, the NW-trending fault structures in Egongshan basin are characterized by tensile-shearing, NE-dipping and dextrorotaty down slipping, having an obvious control over three uranium deposits and the overwhelming majority of uranium occurrences, and are the key factors to uranium mineralization. The study on the NW-trending fault structures is of practical significance in ore prospecting in Egongshan basin and other areas

  2. Impact of tropical cyclones on the evolution of the monsoon-driven upwelling system in the coastal waters of the northern South China Sea

    Science.gov (United States)

    Zheng, Binxin; Li, Yunhai; Li, Jiufa; Shu, Fangfang; He, Jia

    2018-02-01

    An upwelling system exists in the coastal waters of the northern South China Sea (NSCS), a region that is frequently affected by tropical cyclones in summer. This study investigates the evolution of the NSCS monsoon-driven upwelling system and the effects of the Talim and Doksuri tropical cyclones on the system using in situ observational data obtained at three mooring stations, one land-based meteorological station, and concurrent satellite remote sensing data for the NSCS coastal waters from May to July 2012. The results show that the occurrence and evolution of the upwelling system were mainly controlled by the Asian southwest monsoon, while the eastward current also made important contributions to the upwelling intensity. A decrease in the bottom water temperature and shifts in the along-shore and cross-shore currents were direct evidence of the establishment, existence, and recovery of this upwelling. Tropical cyclones have significant impacts on hydrodynamics and can thus influence the evolution of the NSCS upwelling system by changing the local wind and current fields. Variations in water level and local current systems impeded the development of upwelling during tropical cyclones Talim and Doksuri in the study area, which have low-frequency fluctuations of approximately 2-10 days. These variations were the results of the coupled interactions between local wind fields, coastal trapped waves, and other factors. The hydrodynamic environment of the marine water (including coastal upwelling system) rapidly recovered to normal sea conditions after each cyclone passed due to the relatively short duration of the impact of a tropical cyclone on the dynamic environment of the waters.

  3. Strengthening African Union for African Integration: An African ...

    African Journals Online (AJOL)

    Toshiba

    globalization, there is strong need for African leaders to re-strategize a new world view of African role in African affairs ... need to cope with the forces of globalization and her impact on national sovereignty and threat to local ..... 2011 endorsed a framework, roadmap and architecture of the continental free trade area (CFTA).

  4. Easily fabricated and lightweight PPy/PDA/AgNW composites for excellent electromagnetic interference shielding.

    Science.gov (United States)

    Wang, Yan; Gu, Fu-Qiang; Ni, Li-Juan; Liang, Kun; Marcus, Kyle; Liu, Shu-Li; Yang, Fan; Chen, Jin-Ju; Feng, Zhe-Sheng

    2017-11-30

    Conductive polymer composites (CPCs) containing nanoscale conductive fillers have been widely studied for their potential use in various applications. In this paper, polypyrrole (PPy)/polydopamine (PDA)/silver nanowire (AgNW) composites with high electromagnetic interference (EMI) shielding performance, good adhesion ability and light weight are successfully fabricated via a simple in situ polymerization method followed by a mixture process. Benefiting from the intrinsic adhesion properties of PDA, the adhesion ability and mechanical properties of the PPy/PDA/AgNW composites are significantly improved. The incorporation of AgNWs endows the functionalized PPy with tunable electrical conductivity and enhanced EMI shielding effectiveness (SE). By adjusting the AgNW loading degree in the PPy/PDA/AgNW composites from 0 to 50 wt%, the electrical conductivity of the composites greatly increases from 0.01 to 1206.72 S cm -1 , and the EMI SE of the composites changes from 6.5 to 48.4 dB accordingly (8.0-12.0 GHz, X-band). Moreover, due to the extremely low density of PPy, the PPy/PDA/AgNW (20 wt%) composites show a superior light weight of 0.28 g cm -3 . In general, it can be concluded that the PPy/PDA/AgNW composites with tunable electrical conductivity, good adhesion properties and light weight can be used as excellent EMI shielding materials.

  5. African Journals Online (AJOL)

    African Journals Online (AJOL)

    2017). South African Family Practice. Vol 30, No 4 (2017). South African Journal of Clinical Nutrition. Vol 22, No 3 (2017). Journal of Endocrinology, Metabolism and Diabetes of South Africa. AJOL African Journals Online. HOW TO USE AJOL.

  6. Retraction | Simon | African Zoology

    African Journals Online (AJOL)

    Panthera leo) ina. West African national park”. African Zoology is publishing an Editorial Expression of Concern regarding the following article: “New records of a threatened lion population (Panthera leo) in a West African national park” by ...

  7. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journal of Science and Technology; Educational leadership and management: theory, policy and practice. South African Journal of Education; Involute Spur Gear Template Development by Parametric Technique Using Computer Aided Design African Research Review; Drug interactions with tuberculosis therapy

  8. African Journals Online: Health

    African Journals Online (AJOL)

    bioline.org.br/hs. African Health Sciences encourages authors to now submit ... The African Journal of Drug & Alcohol Studies is an international scientific journal published by the African Centre for Research and Information on ...

  9. Role of physical forcings and nutrient availability on the control of satellite-based chlorophyll a concentration in the coastal upwelling area of the Sicilian Channel

    Directory of Open Access Journals (Sweden)

    Bernardo Patti

    2010-08-01

    Full Text Available The northern sector of the Sicilian Channel is an area of favourable upwelling winds, which ought to support primary production. However, the values for primary production are low when compared with other Mediterranean areas and very low compared with the most biologically productive regions of the world’s oceans: California, the Canary Islands, Humboldt and Benguela. The aim of this study was to identify the main factors that limit phytoplankton biomass in the Sicilian Channel and modulate its monthly changes. We compared satellite-based estimates of chlorophyll a concentration in the Strait of Sicily with those observed in the four Eastern Boundary Upwelling Systems mentioned above and in other Mediterranean wind-induced coastal upwelling systems (the Alboran Sea, the Gulf of Lions and the Aegean Sea. Our results show that this low level of chlorophyll is mainly due to the low nutrient level in surface and sub-surface waters, independently of wind-induced upwelling intensity. Further, monthly changes in chlorophyll are mainly driven by the mixing of water column and wind-induced and/or circulation-related upwelling processes. Finally, primary production limitation due to the enhanced stratification processes resulting from the general warming trend of Mediterranean waters is not active over most of the coastal upwelling area off the southern Sicilian coast.

  10. Intensification of Chile-Peru upwelling under climate change: diagnosing the impact of natural and anthropogenic forcing from the IPSL-CM5 model.

    Science.gov (United States)

    Jebri, B.; Khodri, M.; Gastineau, G.; Echevin, V.; Thiria, S.

    2017-12-01

    Upwelling is critical to the biological production, acidification, and deoxygenation of the ocean's major eastern boundary current ecosystems. A conceptual hypothesis suggests that the winds that favour coastal upwelling intensify with anthropogenic global warming due to increased land-sea temperature contrast. We examine this hypothesis for the dynamics of the Peru-Chile upwelling using a set of four large ensembles of coupled, ocean-atmosphere model simulations with the IPSL model covering the 1940-2014 period. In one large ensemble we prescribe the standard CMIP5 greenhouse gas (GHG) concentrations, anthropogenic aerosol, ozone and volcanic forcings, following the historical experiments through 2005 and RCP8.5 from 2006-2014, while the other ensembles consider separately the GHG, ozone and volcanic forcings. We find evidence for intensification of upwelling-favourable winds with however little evidence of atmospheric pressure gradients in response to increasing land-sea temperature differences. Our analyses reveal poleward migration and intensification of the South Pacific Anticyclone near poleward boundaries of climatological Peruvian and Chilean upwelling zones. This contribution further investigates the physical mechanisms for the Peru-Chile upwelling intensification and the relative role of natural and anthropogenic forcings.

  11. Upwelling regions, the most fertile of the seas' habitats, are also ...

    African Journals Online (AJOL)

    spamer

    developed along the South African coast (Horstman. 1981), and during 1992/93 alone, 60 red tides were ...... and Harrison 1975). In an even more dynamic situation, a bloom of L. polyedrum persisted for 20 days off ...... to starvation unless reformed soon thereafter. Given the importance of similar clupeoid fish in other up-.

  12. Late Cretaceous to Present evolution of the NW Africa peri-cratonic in the Africa-Eurasia plate convergence context

    Science.gov (United States)

    Ghorbal, B.; Bertotti, G.; Andriessen, P. A. M.

    2009-04-01

    Africa-Eurasia plate convergence is the main mechanism to explain topographic evolution and patterns of Tertiary vertical motions recorded around the entire Mediterranean and even further east. However, most of the studies are concentrated on the Eurasian side of the Mediterranean Realm. Along the NW Africa pericratonic zone (western Mediterranean side) extending longitudinally from the Anti-Atlas to the Rif Mountains, the highest topography is observed in the High Atlas intracontinental belt and in the Pan-African Anti-Atlas belt, and not in the youngest belt, the Rif. The combination of AFT and (U-Th)/He low-thermal dating, performed on pre-Cenozoic basement rocks along the Moroccan pericratonic transect (500km) yield ages ranging respectively between 90-9Ma and 65-7Ma, documenting vertical motions of subsidence and exhumation in between Late Cretaceous and Present. Time-Temperature models show that vertical movements are spatially zoned through Morocco, with the highest amplitude of vertical movements in the High Atlas (>4-5km) and more modest amounts in the Anti-Atlas and the Western Meseta (African peri-cratonic zone including the Western Meseta and the Anti-Atlas in addition to the Atlas and the Rif systems experienced Tertiary deformation. Two stages of folding are distinguished on the basis of low-thermal dating results along the pericratonic transect. The first is a lithospherical folding of ~500km in the Late Cretaceous (confirming that this process is a primary response to recently induced compressional stress fields) and the second is a crustal folding of ~100-150km wavelength in the Late Eocene that occurred independently to the mantle, requiring therefore the existence of a decoupling in between the base of the crust and the high mantle.

  13. Firewood Resource Management in Different Landscapes in NW Patagonia

    Directory of Open Access Journals (Sweden)

    Daniela V. Morales

    2017-09-01

    Full Text Available Ecosystems, their components, processes and functions are all subject to management by human populations, with the purpose of adapting the environments to make them more habitable and ensuring the availability and continuity of subsistence resources. Although a lot of work has been carried out on resources of alimentary or medicinal interest, little has been done on associating processes of domestication with firewood extraction, a practice considered to be destructive of the environment. In the arid steppe of NW Patagonia, inhabited and managed for different purposes for a long time by Mapuche-Tehuelche communities, the gathering of combustible plant species has up to the present time played a crucial role in cooking and heating, and work is required to achieve sustainability of this resource. In this study we evaluate whether environments with less landscape domestication are more intensively used for firewood gathering. Using an ethnobiological approach, information was obtained through participant observation, interviews and free listing. The data were examined using both qualitative and quantitative approaches. Twenty-eight firewood species are gathered, both native (75% and exotic (25%. The supply of firewood mainly depends on gathering from the domesticated (10 species, semi-domesticated (17 species and low human intervention landscapes (17 species. In contrast to our hypothesis, average use intensity is similar in all these landscapes despite their different levels of domestication. That is, the different areas are taken advantage of in a complementary manner in order to satisfy the domestic demand for firewood. Neither do biogeographic origin or utilitarian versatility of collected plants vary significantly between the different landscape levels of domestication. Our results show that human landscape domestication for the provision of firewood seems to be a socio-cultural resilient practice, and shed new light on the role of culture in

  14. A study of petroleum system in Chuhuangkeng anticline, NW Taiwan

    Science.gov (United States)

    Yiang, S.; Tsai, L. Y.

    2015-12-01

    Since energy demand is still increasing in the world, the exploration of unconventional fossil fuel becomes more and more important today. Miaoli area of the NW Western Foothill Belt, Taiwan, had been a major oil and gas producing field in the past, important oil/gas producing structures include Tiechenshen, Chinshui and Chuhuangkeng anticline. The reservoir rocks of unconventional resources need to be examined to illustrate the remaining hydrocarbon potential of Chuhuangkeng anticline. A standard evaluation procedure for assessing integrated geochemical parameters can thus be established. In this study, we combine various geochemical parameters including TOC, porosity, Rock-Eval pyrolysis, vitrinite reflectance measurement to assess the HC potential of shale gas reservoirs. The results show that Wuchishan and Mushan Formations possess the best hydrocarbon potential in Chuhuangkeng anticline. The maturation of Wuchishan and Mushan Formations are both in oil window (Ro of Wuchishan formation =1.7% , Ro of Mushan =1.01~1.53% ). The maturation of Shitih Formation barely reached oil window, however the shallower depth and less exploration cost are the advantages of Shitih Formation. Moreover, Wuchishan Formation is a dry gas field and Mushan Formation is a condensate gas field. The results of porosity show that there are secondary porosity existed in Mushan Formation which provides the extra storage space for hydrocarbon. Additionally, Piling Shale is a good cap rock on top of Mushan formation, it further benefits the conservation of oil and gas in Mushan Formation. In conclude, Mushan Formation is the most potential HC target in future shale gas exploration.

  15. ERUPTIVE VARIABLE STARS AND OUTFLOWS IN SERPENS NW

    Energy Technology Data Exchange (ETDEWEB)

    Hodapp, Klaus W. [Institute for Astronomy, University of Hawaii, 640 N. Aohoku Place, Hilo, HI 96720 (United States); Chini, Rolf; Watermann, Ramon; Lemke, Roland, E-mail: hodapp@ifa.hawaii.edu [Ruhr Universitaet Bochum, Astronomisches Institut, Universitaetsstrasse 150, D-44801 Bochum (Germany)

    2012-01-01

    We study the outflow activity, photometric variability, and morphology of three very young stellar objects in the Serpens NW star-forming region: OO Serpentis, EC 37 (V370 Ser), and EC 53 (V371 Ser). High spatial resolution Keck/NIRC2 laser guide star adaptive optics images obtained in 2007 and 2009 in broadband K and in a narrowband filter centered on the 1-0 S(1) emission line of H{sub 2} allow us to identify the outflows from all three objects. We also present new, seeing-limited data on the photometric evolution of the OO Ser reflection nebula and re-analyze previously published data. We find that OO Ser declined in brightness from its outburst peak in 1995 to about 2003, but that this decline has recently stopped and actually reversed itself in some areas of the reflection nebula. The morphology and proper motions of the shock fronts MHO 2218 near EC 37 suggest that they all originate in EC 37 and that this is an outflow seen nearly along its axis. We identify an H{sub 2} jet emerging from the cometary nebula EC 53. The star illuminating EC 53 is periodically variable with a period of 543 days and has a close-by, non-variable companion at a projected distance of 92 AU. We argue that the periodic variability is the result of accretion instabilities triggered by another very close, not directly observable, binary companion and that EC 53 can be understood in the model of a multiple system developing into a hierarchical configuration.

  16. Grounding zone wedges, Kveithola Trough (NW Barents Sea)

    Science.gov (United States)

    Rebesco, Michele; Urgeles, Roger; Özmaral, Asli; Hanebuth, Till; Caburlotto, Andrea; Hörner, Tanja; Lantzsch, Hendrik; LLopart, Juame; Lucchi, Renata; Skøtt Nicolaisen, Line; Giacomo, Osti; Sabbatini, Anna; Camerlenghi, Angelo

    2014-05-01

    Swath bathymetry within Kveithola Trough (NW Barents Sea) shows a seafloor characterized by E-W trending megascale glacial lineations (MSGLs) overprinted by transverse Grounding Zone Wedges (GZWs), which give the trough a stair profile (Rebesco et al., 2011). GZWs are formed by deposition of subglacial till at temporarily stable ice-stream fronts in between successive episodic retreats (Rüther et al., 2012; Bjarnadóttir et al., 2012). Sub-bottom data show that present-day morphology is largely inherited from palaeo-seafloor topography of GZWs, which is draped by a deglacial to early Holocene glaciomarine sediments (about 15 m thick). The ice stream that produced such subglacial morphology was flowing from East to West inside Kveithola Trough during Last Glacial Maximum. Its rapid retreat was likely associated with progressive lift-offs, and successive rapid melting of the grounded ice, induced by the eustatic sea-level rise (Lucchi et al., 2013). References: Bjarnadóttir, L.R., Rüther, D.C., Winsborrow, M.C.M., Andreassen, K., 2012. Grounding-line dynamics during the last deglaciation of Kveithola, W Barents Sea, as revealed by seabed geomorphology and shallow seismic stratigraphy. Boreas, 42, 84-107. Lucchi R.G., et al. 2013. Postglacial sedimentary processes on the Storfjorden and Kveithola TMFs: impact of extreme glacimarine sedimentation. Global and Planetary Change, 111, 309-326. Rebesco, M., et al. 2011. Deglaciation of the Barents Sea Ice Sheet - a swath bathymetric and subbottom seismic study from the Kveitehola Trough. Marine Geology, 279, 141-14. Rüther, D.C., Bjarnadóttir, L.R., Junttila, J., Husum, K., Rasmussen, T.L., Lucchi, R.G., Andreassen, K., 2012. Pattern and timing of the north-western Barents Sea Ice Sheet deglaciation and indications of episodic Holocene deposition. Boreas 41, 494-512.

  17. Timing and Spatial Distribution of Loess in Xinjiang, NW China.

    Directory of Open Access Journals (Sweden)

    Yun Li

    Full Text Available Central Asia is one of the most significant loess regions on Earth, with an important role in understanding Quaternary climate and environmental change. However, in contrast to the widely investigated loess deposits in the Chinese Loess Plateau, the Central Asian loess-paleosol sequences are still insufficiently known and poorly understood. Through field investigation and review of the previous literature, the authors have investigated the distribution, thickness and age of the Xinjiang loess, and analyzed factors that control these parameters in the Xinjiang in northwest China, Central Asia. The loess sediments cover river terraces, low uplands, the margins of deserts and the slopes of the Tianshan Mountains and Kunlun Mountains and are also present in the Ili Basin. The thickness of the Xinjiang loess deposits varies from several meters to 670 m. The variation trend of the sand fraction (>63 μm grain-size contour can indicate the local major wind directions, so we conclude that the NW and NE winds are the main wind directions in the North and South Xinjiang, and the westerly wind mainly transport dust into the Ili basin. We consider persistent drying, adequate regional wind energy and well-developed river terraces to be the main factors controlling the distribution, thickness and formation age of the Xinjiang loess. The well-outcropped loess sections have mainly developed since the middle Pleistocene in Xinjiang, reflecting the appearance of the persistent drying and the present air circulation system. However, the oldest loess deposits are as old as the beginning of the Pliocene in the Tarim Basin, which suggests that earlier aridification occurred in the Tarim Basin rather than in the Ili Basin and the Junggar Basin.

  18. The matter of preservation: A comparison of recent organic-walled dinoflagellate cyst assemblages in sediment trap and core top sediments off Cape Blanc (NW Africa)

    Science.gov (United States)

    Rüßbült, Annegret; Zonneveld, Karin A. F.; Pospelova, Vera

    2017-04-01

    During the last decades, organic-walled dinoflagellate cysts (dinocysts) have become a valuable tool for paleoenvironmental reconstructions. It is known that the sedimentary record depends on several factors like initial cyst production and preservation. Therefore it is necessary to know, to what extent the assemblage in the sediment reflects the primary signal produced in the water column. In this study, we compare undisturbed core top sediments with sediment trap data covering the same time intervals. Both, core and trap, were retrieved at a similar location off Cape Blanc (NW Africa) where high productivity of organic material takes place due to costal upwelling. The samples of trap CBi analyzed for dinocysts were collected over 5 years (2003-2008) and compared to assemblages found in 2 mm interval sections of core GeoB 14103-7. 210Pb dating revealed an age of 2.5 years per core sample, leading to a comparison of the upper 6 mm with CBi 1-5. The dinocyst species composition in core and trap sediments is similar. Both assemblages are dominated by heterotrophic species. However, while the most common species in the trap, Brigantidinium spp., makes up over 50% of each sample, it is less abundant in the core where it forms only 13% of the assemblage. Core samples are dominated by Protoperidinium monospinum with an average of 28%. This species is underrepresented in CBi with 3% abundance. Over time the proportions of the individual species show minor variations both in core and trap samples. We therefore assume that the strong differences in association composition are due to post-depositional processes altering the assemblages in the sediments like degradation or bioturbation rather than to changes in initial cyst production or differences in source areas of trap and sediment core.

  19. Airborne observations of far-infrared upwelling radiance in the Arctic

    Directory of Open Access Journals (Sweden)

    Q. Libois

    2016-12-01

    Full Text Available The first airborne measurements of the Far-InfraRed Radiometer (FIRR were performed in April 2015 during the panarctic NETCARE campaign. Vertical profiles of spectral upwelling radiance in the range 8–50 µm were measured in clear and cloudy conditions from the surface up to 6 km. The clear sky profiles highlight the strong dependence of radiative fluxes to the temperature inversion typical of the Arctic. Measurements acquired for total column water vapour from 1.5 to 10.5 mm also underline the sensitivity of the far-infrared greenhouse effect to specific humidity. The cloudy cases show that optically thin ice clouds increase the cooling rate of the atmosphere, making them important pieces of the Arctic energy balance. One such cloud exhibited a very complex spatial structure, characterized by large horizontal heterogeneities at the kilometre scale. This emphasizes the difficulty of obtaining representative cloud observations with airborne measurements but also points out how challenging it is to model polar clouds radiative effects. These radiance measurements were successfully compared to simulations, suggesting that state-of-the-art radiative transfer models are suited to study the cold and dry Arctic atmosphere. Although FIRR in situ performances compare well to its laboratory performances, complementary simulations show that upgrading the FIRR radiometric resolution would greatly increase its sensitivity to atmospheric and cloud properties. Improved instrument temperature stability in flight and expected technological progress should help meet this objective. The campaign overall highlights the potential for airborne far-infrared radiometry and constitutes a relevant reference for future similar studies dedicated to the Arctic and for the development of spaceborne instruments.

  20. Sardine (Sardina pilchardus) larval dispersal in the Iberian upwelling system, using coupled biophysical techniques

    Science.gov (United States)

    Santos, A. M. P.; Nieblas, A.-E.; Verley, P.; Teles-Machado, A.; Bonhommeau, S.; Lett, C.; Garrido, S.; Peliz, A.

    2018-03-01

    The European sardine (Sardina pilchardus) is the most important small pelagic fishery of the Western Iberia Upwelling Ecosystem (WIUE). Recently, recruitment of this species has declined due to changing environmental conditions. Furthermore, controversies exist regarding its population structure with barriers thought to exist between the Atlantic-Iberian Peninsula, Northern Africa, and the Mediterranean. Few studies have investigated the transport and dispersal of sardine eggs and larvae off Iberia and the subsequent impact on larval recruitment variability. Here, we examine these issues using a Regional Ocean Modeling System climatology (1989-2008) coupled to the Lagrangian transport model, Ichthyop. Using biological parameters from the literature, we conduct simulations that investigate the effects of spawning patchiness, diel vertical migration behaviors, and egg buoyancy on the transport and recruitment of virtual sardine ichthyoplankton on the continental shelf. We find that release area, release depth, and month of release all significantly affect recruitment. Patchiness has no effect and diel vertical migration causes slightly lower recruitment. Egg buoyancy effects are significant and act similarly to depth of release. As with other studies, we find that recruitment peaks vary by latitude, explained here by the seasonal variability of offshore transport. We find weak, continuous alongshore transport between release areas, though a large proportion of simulated ichthyoplankton transport north to the Cantabrian coast (up to 27%). We also show low level transport into Morocco (up to 1%) and the Mediterranean (up to 8%). The high proportion of local retention and low but consistent alongshore transport supports the idea of a series of metapopulations along this coast.

  1. Redescription of Gymnodinium heterostriatum Kofoid et Swezy 1921 (Dinophyceae)

    Science.gov (United States)

    Elbrächter, M.

    1994-12-01

    The dinoflagellate Gymnodinium heterostriatum Kofoid et Swezy is described anew from live material of the upwelling region off the NW African coast. The characteristics that distinguish it from Gymnodinium striatissimum Hulburt, a species with which it has been mistaken since the original description, are discussed.

  2. Ignoring Authentic African Literature Means Ignoring Africans

    Science.gov (United States)

    Romano, Carlin

    2005-01-01

    Africa produces imaginative and authentic literature whose texture makes it impossible to think of Africans as statistics. African writers, however have to struggle to get recognized in America due to their culture and other racial and social differences, hence suggesting that efforts should be made to give authentic African literature its due.

  3. Micro-phytoplankton community structure in the coastal upwelling zone off Concepción (central Chile): Annual and inter-annual fluctuations in a highly dynamic environment

    Science.gov (United States)

    Anabalón, V.; Morales, C. E.; González, H. E.; Menschel, E.; Schneider, W.; Hormazabal, S.; Valencia, L.; Escribano, R.

    2016-12-01

    An intensification of upwelling-favorable winds in recent decades has been detected in some of the main eastern boundary current systems, especially at higher latitudes, but the response of coastal phytoplankton communities in the Humboldt Current System (HCS) remains unknown. At higher latitudes in the HCS (35-40°S), strong seasonality in wind-driven upwelling during spring-summer coincides with an annual increase in coastal chlorophyll-a and primary production, and a dominance of micro-phytoplankton. In order to understand the effects of potential upwelling intensification on the micro-phytoplankton community in this region, annual and inter-annual variability in its structure (total and taxa-specific abundance and biomass) and its association with oceanographic fluctuations were analyzed using in situ time series data (2002-2009) from a shelf station off Concepcion (36.5°S). At the annual scale, total mean abundance and biomass, attributed to a few dominant diatom taxa, were at least one order of magnitude greater during spring-summer than autumn-winter, in association with changes in upwelling and surface salinity and temperature, whereas macro-nutrient concentrations remained relatively high all the year. At the inter-annual scale, total abundance and biomass decreased during the upwelling season of the 2006-2009 period compared with the 2002-2006 period, notably due to lower abundances of Skeletonema and Leptocylindrus, but the relative dominance of a few taxa was maintained. The 2006-2009 period was characterized by higher upwelling intensity, colder and higher salinity waters, and changes in nutrient concentrations and ratios compared with the first period. The inter-annual changes in the micro-phytoplankton community were mostly associated with changes in surface salinity and temperature (changes in upwelling intensity) but also with changes in Si/N and N/P, which relate to other land-derived processes.

  4. African Communalism and Globalization

    African Journals Online (AJOL)

    info

    Abstract. The certainty of African philosophy during pre-colonial Africa is no longer in doubt. Doubting such a claim is denying the existence of the African race which may be self contradictory. As this work observes, African philosophy which is all encompassing, is inbuilt in African communalism through which indigenous ...

  5. Trends in African philosophy

    African Journals Online (AJOL)

    JONATHAN

    In the contention of Oladipo (2006), the debate on the idea of. African philosophy which has been divided into trends or schools, dates back to the 1960's and 70's, which constitute the modern epoch of African philosophy, when some African thinkers began to question the perspective that traditional African beliefs and.

  6. African Journals Online (AJOL)

    African Journals Online (AJOL)

    It has also been difficult for African researchers to access the work of other African academics. In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and to the rest of the ... Egyptian Journal of Medical Human Genetics.

  7. African Journals Online (AJOL)

    African Journals Online (AJOL)

    It has also been difficult for African researchers to access the work of other African academics. In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and to the rest of the world. AJOL is a Non-Profit Organisation based in ...

  8. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journals OnLine (AJOL) is the world's largest and pre-eminent collection of peer-reviewed, African-published scholarly journals. Historically, scholarly information has flowed from North to South and from West to East. It has also been difficult for African researchers to access the work of other African academics.

  9. African Journals Online: Cameroon

    African Journals Online (AJOL)

    Items 1 - 8 of 8 ... African Anthropologist. African Anthropology is the journal of the Pan African Anthropological Association (PAAA). It provides a forum for African and Africanist anthropologists to publish research reports, articles, book reviews, news items and other useful information. It aims at stimulating the debate of ideas ...

  10. African Journals Online (AJOL)

    African Journals Online (AJOL)

    2018). South African Journal of Animal Science. Vol 8, No 1 (2018). African Journal of Chemical Education. Vol 48, No 2 (2018). South African Journal of Animal Science. Vol 48, No 1 (2018). South African Journal of Animal Science. Vol 7, No ...

  11. African Journals Online (AJOL)

    African Journals Online (AJOL)

    South African Journal of Education; Corporal punishment in South African schools : a neglected explanation for its Existence South African Journal of Education; The competitive advantage of nations: is Porter's Diamond Framework a new theory that explains the international competitiveness of countries? Southern African ...

  12. African Journals Online (AJOL)

    African Journals Online (AJOL)

    It has also been difficult for African researchers to access the work of other African academics. In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and ... Featured Country: South Africa, Featured Journal: Ergonomics SA ...

  13. African Journals Online: Peru

    African Journals Online (AJOL)

    PROMOTING ACCESS TO AFRICAN RESEARCH. AFRICAN JOURNALS ONLINE (AJOL) · Journals · Advanced Search · USING AJOL · RESOURCES. African Journals Online: Peru. Home > African Journals Online: Peru. Log in or Register to get access to full text downloads. Username, Password, Remember me

  14. Description of some characteristics of flowers and seeds of Arabidopsis thaliana - ecotype landsberg erecta and mutant NW4

    Directory of Open Access Journals (Sweden)

    Leszek Trząski

    2014-01-01

    Full Text Available Flowers and seeds of Landsberg erecta (Ler ecotype and NW4 mutant were studied by light microscopy and scanning electron microscopy to reveal characteristic features of their structure. The NW4 mutant flowers differ from Ler mainly in presence of two bract-like sepals with complicated vasculature and a variable number of secondary flowers. In the two outer whorls of NW4 flower, variable number of transformed stamen-, petal-, sepal- and style-like elements also occur. The NW4 mutant seeds are characterized by the absence of mucilage around the surface and a deviating seed coat morphology.

  15. Glacimarine sedimentation in Petermann Fjord and Nares Strait, NW Greenland

    Science.gov (United States)

    Hogan, Kelly; Jakobsson, Martin; Mayer, Larry; Mix, Alan; Nielsen, Tove; Kamla, Elina; Reilly, Brendan; Heirman, Katrina An; Stranne, Christian; Mohammed, Rezwan; Eriksson, Bjorn; Jerram, Kevin

    2017-04-01

    thinning and acceleration of NW Greenland's marine-terminating outlet glaciers.

  16. Structure of the Rangel alkaline complex (Salta, NW Argentina)

    Science.gov (United States)

    Vegas, Nestor; Hongn, Fernando; María Tubía, José; Menegatti, Nilda; Aranguren, Aitor; Rodriguez-Méndez, Lidia

    2017-04-01

    The alcaline complex of the Sierra de Rangel is a Cretaceous granitoid emplaced in the Puna Region, at the province of Salta (NW Argentina). This granitoid spreads over 9 km2 and is elongated following a NE-SW trend. The Rangel complex intrudes Quaternary sediments of the Salinas Grandes salt flat towards the east and Ordovician quartzites and metapelites to the west. There are three main facies in the Rangel granitoid: the easternmost part of the intrusion is composed by sienites that crop out in three hills isolated into the salt flat; the central part of the stock made of alkaline granites and quartz-sienites; and the westernmost side composed by alkaline granites. The available rubidium-strontium ages point out two magmatic pulses: 134±1,6Ma for the granites and quartz-sienites and the sienites of the central and eastern part and 122±1,5 Ma for the alkaline granites of the western border. The most common structure in the host quartzites and metapelites is N55oE-trending schistosity that dips around 60o to the SE. This schistosity is parallel to the axial surface of asymmetric folds with axes plunging to the east. The sharp western contact of the Rangel complex with the host rocks display a N30oE strike and dips around 40o to the SE. This contact is parallel to the intra-magmatic contact between the western and central facies and to the NE-SW elongation of the granitoid. The study of the magnetic fabrics carried on 52 sites of the Rangel complex outline the presence of two sets of tabular intrusions: a main group of overlapping NE-trending sheets that dip to the SE; and a minor group roughly perpendicular to the previous one. The integration of the magnetic fabrics results and the structural data suggest that the former set of intrusions are feeder dykes of the NE-trending sheeted intrusions. Moreover, the radiometric data suggest that the oldest pulse corresponds to the upper part of the granitoid. This fact would imply that the emplacement was controlled by

  17. An Operational Coastal Forecasting System in Galicia (NW Spain)

    Science.gov (United States)

    Balseiro, C. F.; Carracedo, P.; Pérez, E.; Pérez, V.; Taboada, J.; Venacio, A.; Vilasa, L.

    2009-09-01

    The Galician coast (NW Iberian Peninsula coast) and mainly the Rias Baixas (southern Galician rias) are one of the most productive ecosystems in the world, supporting a very active fishing and aquiculture industry. This high productivity lives together with a high human pressure and an intense maritime traffic, which means an important environmental risk. Besides that, Harmful Algae Blooms (HAB) are common in this area, producing important economical losses in aquiculture. In this context, the development of an Operational Hydrodynamic Ocean Forecast System is the first step to the development of a more sophisticated Ocean Integrated Decision Support Tool. A regional oceanographic forecasting system in the Galician Coast has been developed by MeteoGalicia (the Galician regional meteorological agency) inside ESEOO project to provide forecasts on currents, sea level, water temperature and salinity. This system is based on hydrodynamic model MOHID, forced with the operational meteorological model WRF, supported daily at MeteoGalicia . Two grid meshes are running nested at different scales, one of ~2km at the shelf scale and the other one with a resolution of 500 m at the rias scale. ESEOAT (Puertos del Estado) model provide salinity and temperature fields which are relaxed at all depth along the open boundary of the regional model (~6km). Temperature and salinity initial fields are also obtained from this application. Freshwater input from main rivers are included as forcing in MOHID model. Monthly mean discharge data from gauge station have been provided by Aguas de Galicia. Nowadays a coupling between an hydrological model (SWAT) and the hydrodynamic one are in development with the aim to verify the impact of the rivers discharges. The system runs operationally daily, providing two days of forecast. First model verifications had been performed against Puertos del Estado buoys and Xunta de Galicia buoys network along the Galician coast. High resolution model results

  18. Distribution Strategies for Solar and Wind Renewables in NW Europe

    Science.gov (United States)

    Smedley, Andrew; Webb, Ann

    2017-04-01

    Whilst the UNFCCC Paris Agreement Climate change was ratified in November, 2016 saw the highest global temperature anomaly on record at 1.2°C above pre-industrial levels. As such there is urgent need to reduce CO2 emissions by a move away from fossil fuels and towards renewable electricity energy technologies. As the principal renewable technologies of solar PV and wind turbines contribute an increasing fraction to the electricity grid, questions of cumulative intermittency and the large-scale geographic distribution of each technology need to be addressed. In this study our initial emphasis is on a calculation of a relatively high spatial resolution (0.1° × 0.1°) daily gridded dataset of solar irradiance data, over a 10 year period (2006-2015). This is achieved by coupling established sources of satellite data (MODIS SSF level2 instantaneous footprint data) to a well-validated radiative transfer model, here LibRadTran. We utilise both a morning and afternoon field for two cloud layers (optical depth and cloud fraction) interpolated to hourly grids, together with aerosol optical depth, topographic height and solar zenith angle. These input parameters are passed to a 5-D LUT of LibRadTran results to construct hourly estimates of the solar irradiance field, which is then integrated to a daily total. For the daily wind resource we rely on the 6 hourly height-adjusted ECMWF ERA-Interim reanalysis wind fields, but separated into onshore, offshore and deep water components. From these datasets of the solar and wind resources we construct 22 different distribution strategies for solar PV and wind turbines based on the long-term availability of each resource. Combining these distributions with the original daily gridded datasets enables each distribution strategy to be then assessed in terms of the day-to-day variability, the installed capacity required to maintain a baseline supply, and the relative proportions of each technology. Notably for the NW European area

  19. Evolution of the earliest mantle caused by the magmatism-mantle upwelling feedback: Implications for the Moon and the Earth

    Science.gov (United States)

    Ogawa, M.

    2017-12-01

    The two most important agents that cause mantle evolution are magmatism and mantle convection. My earlier 2D numerical models of a coupled magmatism-mantle convection system show that these two agents strongly couple each other, when the Rayleigh number Ra is sufficiently high: magmatism induced by a mantle upwelling flow boosts the upwelling flow itself. The mantle convection enhanced by this positive feedback (the magmatism-mantle upwelling, or MMU, feedback) causes vigorous magmatism and, at the same time, strongly stirs the mantle. I explored how the MMU feedback influences the evolution of the earliest mantle that contains the magma ocean, based on a numerical model where the mantle is hot and its topmost 1/3 is partially molten at the beginning of the calculation: The evolution drastically changes its style, as Ra exceeds the threshold for onset of the MMU feedback, around 107. At Ra 107, however, the mantle remains compositionally more homogeneous in spite of the widespread magmatism, and the deep mantle remains hotter than the shallow mantle, because of the strong convective stirring caused by the feedback. The threshold value suggests that the mantle of a planet larger than Mars evolves in a way substantially different from that in the Moon does. Indeed, in my earlier models, magmatism makes the early mantle compositionally stratified in the Moon, but the effects of strong convective stirring overwhelms that of magmatism to keep the mantle compositionally rather homogeneous in Venus and the Earth. The MMU feedback is likely to be a key to understanding why vestiges of the magma ocean are so scarce in the Earth.

  20. CHANGES IN NUTRIENT CONTENT OF PALMARIA PALMATA IN RESPONSE TO VARIABLE LIGHT AND UPWELLING IN NORTHERN SPAIN(1).

    Science.gov (United States)

    Martínez, Brezo; Rico, Jose M

    2008-02-01

    Light has been identified as one of the main factors affecting seaweed ecophysiology. We investigated the dependence of nutrient metabolism on sun and shade light conditions and whether episodes of upwelling of nutrient-rich subsuperficial water could reduce the summer nutrient limitation driving physiological changes in Palmaria palmata (L.) Kuntze. We measured the major nutrient pools, photosynthetic pigments, and light curves, under sun and shade conditions during a summer period when one upwelling was recorded. The redundancy analysis (RDA) produced two clear groups: sun- and shade-acclimated algae. Light was the major predictive factor. Sun-acclimated algae exhibited higher carbon (C) and lower nitrogen (N) and phosphorus (P) content in association with the storage of floridoside (main C reserve) to benefit from higher irradiance (under nutrient limitation). Among N pools, N reserves (phycoerythrin, nitrate) were a lower proportion of the total N in sun-acclimated algae, suggesting their degradation to fulfill the N demands of the cell. The orthophosphate content was also lower in sun-acclimated algae, indicating its utilization as a nutrient reserve. In contrast, N within cell walls and membranes and chl a contributed to a similar proportion of the total N in sun- and shade-acclimated algae, suggesting a response to sustain cell integrity. Transient high nutrient concentration due to the upwelling was unrelated to the nutrient content of the thallus. The storage of C as floridoside from high light exposure was shown to be the driving force for the metabolic adjustment of P. palmata at the end of summer before the onset of dormancy. © 2008 Phycological Society of America.

  1. Nitrous Oxide Production in the Eastern Tropical South Pacific Upwelling Zone

    Science.gov (United States)

    Ji, Q.; Babbin, A. R.; Ward, B. B.

    2014-12-01

    The Eastern Tropical South Pacific upwelling zone, where low to undetectable oxygen concentrations exist in the water column, is a region of intense nitrous oxide (N2O) production in the ocean. N2O production is generally attributed to nitrification and denitrification in oxic and anoxic waters, respectively, with overlap under suboxic conditions. Seawater samples from different depths and in situ oxygen concentrations were incubated with 15N tracer labeled substrates (NH4+, NO2- and NO3-) to measure potential N2O production rates. These rates were used to determine contributions of nitrification and denitrification to total N2O production. N2O reached maximum concentrations at the base of oxycline just above the oxygen deficient zone (ODZ) and nitrification was the major production pathway. The N2O yield from nitrification, i.e., the ratio of N2O to NO2- production from NH4+, increased from ~0.04% to ~1% as oxygen concentration decreased from 100% to ~1% saturation. This relationship is consistent with culture studies showing increased N2O yield from nitrification at low oxygen; and thus with high N2O production rate from nitrification in the oxycline. N2O production from NO3- was detected at the base of oxycline. Highest N2O production rates (up to 10 nM d-1) were detected at the top of the ODZ, with denitrification as the major pathway. At the secondary nitrite maximum within the core of the ODZ, rates of N2O production from denitrification were relatively high despite low N2O concentration, suggesting N2O reduction to N2 must be co-occurring. This implies rapid N2O turnover by denitrification within the ODZ and a close coupling between production and consumption. These results indicate that oxygen concentrations greatly influence both the magnitude of N2O production and the relative contributions of nitrification and denitrification. Because most N2O production occurred in the oxycline and in the uppermost layer of the ODZ, anticipated spatial expansion of

  2. Cenozoic intraplate volcanism on New Zealand: Upwelling induced by lithospheric removal

    Science.gov (United States)

    Hoernle, K.; White, J. D. L.; van den Bogaard, P.; Hauff, F.; Coombs, D. S.; Werner, R.; Timm, C.; Garbe-Schönberg, D.; Reay, A.; Cooper, A. F.

    2006-08-01

    Diffuse intraplate volcanism spanning the Cenozoic on the North, South, Chatham, Auckland, Campbell and Antipodes Islands of New Zealand has produced quartz tholeiitic to basanitic/nephelinitic (including their differentiates) monogenetic volcanic fields and large shield volcanoes. New 40Ar/ 39Ar ages, combined with published age data, show no correlations among age, location or composition of the volcanoes. Continuous volcanism in restricted areas over long time periods, and a lack of volcanic age progressions in the direction and at the rate of plate motion, are inconsistent with a plume origin for the intraplate volcanism. Although localized extension took place during some episodes of volcanic activity, the degree of extension does not correlate with erupted volumes or compositions. Major and trace element data suggest that the silica-poor volcanic rocks (primarily basanites) were derived through low degrees of partial melting at deeper depths than the more silica-rich volcanic rocks (alkali basalts and tholeiites) and that all melts were produced from ocean island basalt (OIB)-type sources, containing garnet pyroxenite or eclogite. The Sr-Nd-Pb isotope data indicate that the silica-poor rocks were derived from high time-integrated U/Pb (HIMU)-type sources and the silica-rich rocks from more enriched mantle (EM)-type sources, reflecting greater interaction with lithosphere modified by subduction beneath Gondwana. The first-order cause of melting is inferred to be decompression melting in the garnet stability field of upwelling asthenosphere, triggered by removal (detachment) of different parts of the subcontinental lithospheric keel throughout the Cenozoic. In some cases, large thicknesses of keel were removed and magmatism extended over many millions of years. Decompression melting beneath a thick craton generates melts that are likely to be similar to those from the base of the mid-ocean-ridge melting column. At mid-ocean ridges, however, these melts never

  3. Carbon and oxygen isotope time series records of planktonic and benthic foraminifera from the Arabian Sea: Implications on upwelling processes

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Niitsuma, N.

    . Paleoceanographic record of thelastglacial/interglacialcycleintheRedSeaandGulfof Aden. Palaeogeogr. Palaeoclimatol. Palaeoecol. 64, 163^ 187. Manghnani, V., Morrison, J.M., Hopkins, T.S., Bohm, E., 1998. Advection of upwelled waters in the form of plumes o¡ Oman... of 18 Oin precipitation with temperature and altitude. Nature 285, 314^317. Shi,W.,Morrison,J.M.,Bohm,E.,Manghnani,V.,2000.The Omanupwellingzoneduring1993,1994and1995.Deep-Sea Res.II47,1227^1247. Sirocko, F., Sarnthein, M., Erlenkeuser, H., Lange, H., Ar...

  4. Influences of riverine and upwelling waters on the coastal carbonate system off Central Chile and their ocean acidification implications

    Science.gov (United States)

    Vargas, Cristian A.; Contreras, Paulina Y.; Pérez, Claudia A.; Sobarzo, Marcus; Saldías, Gonzalo S.; Salisbury, Joe

    2016-06-01

    A combined data set, combining data from field campaigns and oceanographic cruises, was used to ascertain the influence of both river discharges and upwelling processes, covering spatial and temporal variation in dissolved inorganic carbon (DIC) and aragonite saturation state. This work was conducted in one of the most productive river-influenced upwelling areas in the South Pacific coasts (36°S). Additionally, further work was also conducted to ascertain the contribution of different DIC sources, influencing the dynamics of DIC along the land-ocean range. Six sampling campaigns were conducted across seven stations at the Biobío River basin, covering approximately 200 km. Three research cruises were undertaken simultaneously, covering the adjacent continental shelf, including 12 sampling stations for hydrographic measurements. Additionally, six stations were also sampled for chemical analyses, covering summer, winter, and spring conditions over 2010 and 2011. Our results evidenced that seaward extent of the river plume was more evident during the winter field campaign, when highest riverine DIC fluxes were observed. The carbonate system along the river-ocean continuum was very heterogeneous varying over spatial and temporal scales. High DIC and pCO2 were observed in river areas with larger anthropogenic effects. CO2 supersaturation at the river plume was observed during all campaigns due to the influence of low pH river waters in winter/spring and high-pCO2 upwelling waters in summer. δ13CDIC evidenced that main DIC sources along the river and river plume corresponded to the respiration of terrestrial organic matter. We have linked this natural process to the carbonate saturation on the adjacent river-influenced coastal area, suggesting that Ωaragonite undersaturation in surface/subsurface waters is largely modulated by the influence of both river discharge and coastal upwelling events in this productive coastal area. Conditions of low Ωaragonite might impact

  5. Note on the shelf break upwelling off the southeast coast of Brazil (lat. 26º30'S

    Directory of Open Access Journals (Sweden)

    Afrânio Rubens de Mesquita

    1983-01-01

    Full Text Available A western margin frontal zone is described, from measurements of temperature, salinity and currents, in a section taken with R/V "Prof. W. Besnard" in December 1980, crossing the shelf break border at latitude 26º30'S. The analyses of the sections showed consistently the occurrence of an ascension of the T and S isolines over the shelf break. Simultaneous current measurements showed a surface eddy structure with clockwise circulation and anti-clockwise circulation having a common stem over the break characterizing a shelf break upwelling.

  6. The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

    Directory of Open Access Journals (Sweden)

    M. I. Graco

    2017-10-01

    Full Text Available Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ. It is also an area of intense nitrogen loss and anammox activity and experiences large interannual variability associated with the equatorial remote forcing. In this context, we examined the oceanographic and biogeochemical variability associated with the OMZ off central Peru from a monthly time series (1996–2011 recorded off the coast of Callao (12° 02′ S, 77° 29′ W. The data reveal a rich spectrum of variability in the OMZ that includes frequencies ranging from seasonal to interannual scales. Due to the efficient oceanic teleconnection off Peru, the observed variability is interpreted in the light of an estimate of the equatorial Kelvin wave contribution to sea level anomalies considering the peculiarities of its vertical structure (i.e., the first two baroclinic modes. The span of the data set allows us to contrast two OMZ regimes. The strong regime is associated with the strong 1997–1998 equatorial Pacific El Niño, during which the OMZ adjusted to Kelvin-wave-induced downwelling conditions that switched off the upwelling and drastically reduced nutrient availability. The weak regime corresponds to the post-2000 period associated with the occurrence of moderate central Pacific El Niño events and enhanced equatorial Kelvin wave activity, in which mean upwelling conditions are maintained. It is shown that the characteristics of the coupling between physics and biogeochemistry is distinct between the two regimes with the weak regime being associated with a larger explained variance in biogeochemical properties not linearly related to the ENSO oceanic teleconnection. The

  7. Palaeoceanographic Variability of the Benguela Upwelling System Depending on the Northern Hemisphere Glaciation (NHG) - Indicated by Organic-Walled Dinoflagellates

    Science.gov (United States)

    Bork, M.

    2003-12-01

    The causes and effects of the intensification of growth of the northern Hemisphere ice caps at around 3.2 and 2.74 Ma BP are still unclear. Possible causes are changes in the global ocean circulation and the global carbon cycle, which might have resulted from tectonic processes, solar insolation changes, or the interaction between both processes. The Benguela upwelling area forms a key area within the global ocean system. Here, warm and saline Indian Ocean waters enter the South Atlantic Ocean and are transported to the north. Variability of this inflow may thus result in changes in deep-water production in the North Atlantic, thereby influencing the global thermohaline circulation. Furthermore, the Benguela area is characterized by extremely high bioproductivity in surface waters as a result of year-round upwelling. Variations in the upwelling intensity might lead to changes in atmospheric ¤CO2. To study the changes in the circulation and the upwelling intensity, within this region organic-walled dinoflagellate cysts from two high-resolution cores (ODP 1084 and1082) covering the time interval from 3.3 to 2.5 Ma BP were investigated. Due to their sensitiveness to ecological parameters, organic-walled dinoflagellates reflect oceanographic characteristics keenly. The analyses discover clear distribution differences of individual species, especially of those that are sensible or resistant against aerobic decay. The sensible species, (Protoperidinium and Echinidinium), have their highest abundance from 2.76 to 2.73 Ma BP, a time interval in which the resistant species show no significant changes in their abundance. This implies that during this time interval the oxygen was reduced in the deep- and porewater suggesting that the global ocean deepwater circulation was weakened. Comparing these results with the known intensification of the NHG at around 2.74 Ma BP leads to the speculation that the increasing of ice caps in the northern hemisphere is highly associated with

  8. Distribution and respiration of the high-latitude pelagic amphipod Themisto gaudichaudi in the Benguela Current in relation to upwelling intensity

    Science.gov (United States)

    Auel, Holger; Ekau, Werner

    2009-12-01

    The cold and highly productive waters of coastal upwelling areas provide habitats for marine species usually occurring at higher latitudes and allow those species to extend their distribution ranges towards the equator into regions otherwise characterised by warm and oligotrophic sub-tropical waters. The pelagic hyperiid amphipod Themisto gaudichaudi has a circum-Antarctic epipelagic distribution pattern generally south of 35°S and plays an important role in Antarctic food webs as effective link from zooplankton secondary production to higher trophic levels including seabirds and marine mammals. In the cold and productive waters of the Benguela Current coastal upwelling system, the distribution range of the species extents far northward into the subtropics. The present study focuses on the distribution of T. gaudichaudi at the northernmost limit of its range in the Benguela upwelling system in relation to upwelling intensity and hydrographic conditions (sea surface temperature) based on time-series data from 2002 to 2008. Moreover, field data on life-history traits and respiration rates in relation to water temperature are combined to elucidate the environmental and physiological factors limiting the distribution range. Compared to Themisto populations from higher latitudes, the relatively higher water temperatures in the coastal upwelling region lead to higher respiration rates, faster growth, earlier sexual maturity and smaller body size.

  9. Strengthening African Union for African Integration: An African ...

    African Journals Online (AJOL)

    ... a collective effort to combat terrorism, ensure stability in the political system; and use a collective effort to combat pervasive corruption among African Countries. Corruption kills economic growth and demeans political legitimacy. These factors inhibit investment process hence, trading among African countries is very low.

  10. Equatorial Pacific peak in biological production regulated by nutrient and upwelling during the late Pliocene/early Pleistocene cooling

    Directory of Open Access Journals (Sweden)

    J. Etourneau

    2013-08-01

    Full Text Available The largest increase in export production in the eastern Pacific of the last 5.3 Myr (million years occurred between 2.2 and 1.6 Myr, a time of major climatic and oceanographic reorganization in the region. Here, we investigate the causes of this event using reconstructions of export production, nutrient supply and oceanic conditions across the Pliocene–Pleistocene in the eastern equatorial Pacific (EEP for the last 3.2 Myr. Our results indicate that the export production peak corresponds to a cold interval marked by high nutrient supply relative to consumption, as revealed by the low bulk sedimentary 15N/14N (δ15N and alkenone-derived sea surface temperature (SST values. This ∼0.6 million year long episode of enhanced delivery of nutrients to the surface of the EEP was predominantly initiated through the upwelling of nutrient-enriched water sourced in high latitudes. In addition, this phenomenon was likely promoted by the regional intensification of upwelling in response to the development of intense Walker and Hadley atmospheric circulations. Increased nutrient consumption in the polar oceans and enhanced denitrification in the equatorial regions restrained nutrient supply and availability and terminated the high export production event.

  11. Late Neogene foraminifera from the northern Namibian continental shelf and the transition to the Benguela Upwelling System

    Science.gov (United States)

    Bergh, Eugene W.; Compton, John S.; Frenzel, Peter

    2018-05-01

    Middle Miocene to Plio-Pleistocene foraminifera provide insights into the palaeoenvironment on the northern Namibian continental shelf located at the far northern end of the present-day Benguela Upwelling System (BUS). Biostratigraphy and Strontium Isotope Stratigraphy (SIS) of the recovered basal olive-green mud unit indicate an age of 16 to 14 Ma. A sharp, erosional contact separates the basal mud from the overlying Plio-Pleistocene gravelly pelletal phosphorite sands. Grain size data, P/B ratios and benthic diversity indices indicate a change between the middle Miocene and overlying Plio-Pleistocene palaeoenvironments linked to the timing and conditions associated with the initiation of the BUS. The different lithological units and microfossil assemblages in the olive-green mud unit and the overlying pelletal phosphorite units support the late Miocene initiation of the BUS and the northwards migration of the Angola-Benguela Front. Planktic foraminifera indicate a shift from warmer surface water conditions to cooler conditions during the initiation of the BUS. Benthic palaeobathymetric ranges and P/B ratios are consistent with outer shelf water depths suggesting a deeper palaeoenvironment during the Mid-Miocene Climatic Optimum (MMCO) than today. Benthic foraminifera in the middle Miocene are dominated by large (>1 mm) taxa and adapted to oligotrophic environments before the initiation of the BUS. The benthic assemblage composition indicates that bottom water conditions changed to eutrophic conditions during the Plio-Pleistocene under intensified upwelling conditions.

  12. Metagenomic Analysis of Upwelling-Affected Brazilian Coastal Seawater Reveals Sequence Domains of Type I PKS and Modular NRPS.

    Science.gov (United States)

    Cuadrat, Rafael R C; Cury, Juliano C; Dávila, Alberto M R

    2015-11-27

    Marine environments harbor a wide range of microorganisms from the three domains of life. These microorganisms have great potential to enable discovery of new enzymes and bioactive compounds for industrial use. However, only ~1% of microorganisms from the environment can currently be identified through cultured isolates, limiting the discovery of new compounds. To overcome this limitation, a metagenomics approach has been widely adopted for biodiversity studies on samples from marine environments. In this study, we screened metagenomes in order to estimate the potential for new natural compound synthesis mediated by diversity in the Polyketide Synthase (PKS) and Nonribosomal Peptide Synthetase (NRPS) genes. The samples were collected from the Praia dos Anjos (Angel's Beach) surface water-Arraial do Cabo (Rio de Janeiro state, Brazil), an environment affected by upwelling. In order to evaluate the potential for screening natural products in Arraial do Cabo samples, we used KS (keto-synthase) and C (condensation) domains (from PKS and NRPS, respectively) to build Hidden Markov Models (HMM) models. From both samples, a total of 84 KS and 46 C novel domain sequences were obtained, showing the potential of this environment for the discovery of new genes of biotechnological interest. These domains were classified by phylogenetic analysis and this was the first study conducted to screen PKS and NRPS genes in an upwelling affected sample.

  13. Connecting pigment composition and dissolved trace elements to phytoplankton population in the southern Benguela Upwelling zone (St. Helena Bay)

    Science.gov (United States)

    Das, Supriyo Kumar; Routh, Joyanto; Roychoudhury, Alakendra N.; Veldhuis, Marcel J. W.; Ismail, Hassan E.

    2017-12-01

    Rich in upwelled nutrients, the Southern Benguela is one of the most productive ecosystems in the world ocean. However, despite its ecological significance the role of trace elements influencing phytoplankton population in the Southern Benguela Upwelling System (SBUS) has not been thoroughly investigated. Here, we report pigment composition, macronutrients (nitrate, phosphate and silicate) and concentrations of dissolved Cd, Co, Fe and Zn during late austral summer and winter seasons in 2004 to understand the relationship between the selected trace elements and phytoplankton biomass in St. Helena Bay (SHB), which falls within the southern boundary of the SBUS. Chlorophyll a concentrations indicate higher phytoplankton biomass associated with high primary production during late summer in SHB where high diatom population is inferred from the presence of fucoxanthin. Diminished phytoplankton biomass and a shift from diatoms to dinoflagellates as the dominant phytoplankton taxa are indicated by diagnostic pigments during late winter. Dissolved trace elements (Cd, Co and Zn) and macronutrients play a significant role in phytoplankton biomass, and their distribution is affected by biological uptake and export of trace elements. Continuous uptake of Zn by diatoms may cause an onset of Zn depletion leading to a period of extended diatom proliferation during late summer. Furthermore, the transition from diatom to dinoflagellate dominated phytoplankton population is most likely facilitated by depletion of trace elements (Cd and Co) in the water column.

  14. Plants as Indicators of Past and Present Zones of Upwelling Soil CO2 at the ZERT Facility

    Science.gov (United States)

    Apple, M. E.; Sharma, B.; Zhou, X.; Shaw, J. A.; Dobeck, L.; Cunnningham, A.; Spangler, L.; ZERT Team

    2011-12-01

    By their very nature, photosynthetic plants are sensitive and responsive to CO2, which they fix during the Calvin-Benson cycle. Responses of plants to CO2 are valuable tools in the surface detection of upwelling and leaking CO2 from carbon sequestration fields. Plants exposed to upwelling CO2 rapidly exhibit signs of stress such as changes in stomatal conductance, hyperspectral signatures, pigmentation, and viability (Lakkaraju et al. 2010; Male et al. 2010). The Zero Emission Research and Technology (ZERT) site in Bozeman, MT is an experimental facility for surface detection of CO2 where 0.15 ton/day of CO2 was released (7/19- 8/15/2010, and 7/18 - 8/15/2011) from a 100m horizontal injection well, (HIW), 1.5 m underground with deliberate leaks of CO2 at intervals, and from a vertical injector, (VIW), (6/3-6/24/2010). Soil CO2 concentrations reached 16%. Plants at ZERT include Taraxacum officinale (Dandelion), Dactylis glomerata (Orchard Grass), Poa pratensis, (Kentucky Bluegrass), Phleum pratense (Timothy), Bromus japonicus (Japanese Brome), Medicago sativa (Alfalfa) and Cirsium arvense (Canadian Thistle). Dandelion leaves above the zones of upwelling CO2 at the HIW and the VIW changed color from green to reddish-purple (indicative of an increase in anthocyanins) to brown as they senesced within two weeks of CO2 injection. Their increased stomatal conductance along with their extensive surface area combined to make water loss occur quickly following injection of CO2. Xeromorphic grass leaves were not as profoundly affected, although they did exhibit changes in stomatal conductance, accelerated loss of chlorophyll beyond what would normally occur with seasonal senescence, and altered hyperspectral signatures. Within two weeks of CO2 injection at the HIW and the VIW, hot spots formed, which are circular zones of visible leaf senescence that appear at zones of upwelling CO2. The hot spots became more pronounced as the CO2 injection continued, and were detectable

  15. Evaluation of Water Residence Time, Submarine Groundwater Discharge, and Maximum New Production Supported by Groundwater Borne Nutrients in a Coastal Upwelling Shelf System

    Science.gov (United States)

    Luo, Xin; Jiao, Jiu Jimmy; Liu, Yi; Zhang, Xiaolang; Liang, Wenzhao; Tang, Danling

    2018-01-01

    The biogeochemical processes in the continental shelf systems are usually extensively influenced by coastal upwelling and submarine groundwater discharge (SGD). Using eastern Hainan upwelling shelf system as an example, this study fully investigates SGD and coastal upwelling and their effects on the coastal nutrient loadings to the mixing layer of eastern Hainan shelf. Based on the spatial distributions of 223Ra and 228Ra, water residence time is estimated to be 16.9 ± 8.9 days. Based on the mass balance models of 226Ra and 228Ra, the total SGD of the eastern Hainan shelf is estimated to be 0.8 × 108 and 1.4 × 108 m3 d-1, respectively. The groundwater borne dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphate (DIP) are estimated to be up to 1121.8 and 20.4 μM m2 d-1. The coastal upwelling delivers 2741.8 μM m2 d-1 DIN and 217.7 μM m2 d-1 DIP into the mixing layer, which are predominant in all the exogenous nutrient inputs. The groundwater borne DIN will support a maximum new production of 7.5 mM C m2 d-1, about up to 24.0% of the total new production in the study area. SGD-derived nutrient could be significant as a missing DIN to support the new production in the mixing layer of eastern Hainan shelf. The findings contribute to a better understanding of biogeochemical processes under the influences of SGD and coastal upwelling in the study area and other similar coastal upwelling systems.

  16. Spatio-temporal variation of microphytoplankton in the upwelling system of the south-eastern Arabian Sea during the summer monsoon of 2009

    Directory of Open Access Journals (Sweden)

    Lathika Cicily Thomas

    2013-02-01

    Full Text Available The phytoplankton standing crop was assessed in detail along the South Eastern Arabian Sea (SEAS during the different phases of coastal upwelling in 2009. During phase 1 intense upwelling was observed along the southern transects(8°N and 8.5°N. The maximum chlorophyll a concentration (22.7 mg m-3 was observedin the coastal waters off Thiruvananthapuram (8.5°N. Further north there was no signature of upwelling, with extensive Trichodesmium erythraeum blooms. Diatoms dominated in these upwelling regions with thecentric diatom Chaetoceros curvisetus being the dominant species along the 8°N transect. Along the 8.5°N transect pennate diatoms like Nitzschia seriata and Pseudo-nitzschia sp. dominated. Duringphase 2, upwelling of varying intensity was observed throughout the study area with maximum chlorophyll a concentrations along the 9°N transect (25 mg m-3 with Chaetoceros curvisetus as the dominantphytoplankton. Along the 8.5°N transect pennate diatoms during phase 1 were replaced by centric diatoms like Chaetoceros sp. The presence of solitary pennate diatoms Amphora sp. and Navicula sp.were significant in the waters off Kochi. Upwelling was waning during phase 3 and was confined to the coastal waters of the southern transects with the highest chlorophyll a concentration of 11.2 mg m-3. Along withdiatoms, dinoflagellate cell densities increased in phases 2 and 3. In the northern transects (9°N and 10°N the proportion of dinoflagellates was comparatively higher and was represented mainly by Protoperidinium spp.

  17. Trophic connectivity between offshore upwelling and the inshore food web of Banc d'Arguin (Mauritania): New insights from isotopic analysis

    Science.gov (United States)

    Carlier, Antoine; Chauvaud, Laurent; van der Geest, Matthijs; Le Loc'h, François; Le Duff, Michel; Vernet, Marc; Raffray, Jean; Diakhaté, Djibril; Labrosse, Pierre; Wagué, Abdoulaye; Le Goff, Clément; Gohin, Francis; Chapron, Bertrand; Clavier, Jacques

    2015-11-01

    Banc d'Arguin (BA), Mauritania, is a nationally protected shallow gulf > 10,000 km2 between the Sahara desert and the upwelling system off the Mauritanian coast. In the southeast, BA consists of a 500 km2 tidal flat, the most important wintering site for shorebirds using the East Atlantic Flyway. The Mauritanian upwelling-driven phytoplankton production supports the most productive fisheries worldwide, but little is known about its trophic role in the functioning of the inshore BA food web. Using stable isotopes as trophic tracers to distinguish between upwelling-driven phytoplankton, open ocean phytoplankton, and benthic primary producers, we assessed the spatial extent to which the inshore BA food web is fuelled by upwelling-driven phytoplankton production. The δ13C and δ15N signals were characterized in dominant primary producers, benthic invertebrate taxa, and various fish species along an offshore-inshore (northwest-southeast) gradient. We also monitored the spatial and temporal extent of upwelling entering BA during 2008 with remote sensing of sea surface temperature and chlorophyll a data. The results suggest that benthic invertebrates and fishes living in the northwestern part of BA depend on the nearby upwelling phytoplankton production, but this food source does not support the intertidal benthic community in southeast BA. Furthermore, the isotopic signatures of fishes suggest weak trophic connectivity between the northern subtidal and southeastern intertidal BA. Our results support the hypothesis that the southeastern tidal flat region functions as a distinct ecosystem with a food web supported mainly by local benthic primary production, which is crucial knowledge for effective management of the pristine BA national park.

  18. Determination of the Anthropogenic Carbon Signal to the Total Change in Dissolved Carbon in the Coastal Upwelling Region Along the Washington-Oregon-California Continental Margin

    Science.gov (United States)

    Feely, R. A.

    2016-02-01

    The continental shelf region off the Washington-Oregon-California coast is seasonally exposed to water with a low aragonite saturation state by coastal upwelling of CO2-rich waters. To date, the spatial and temporal distribution of anthropogenic CO2 (Canthro) contribution to the CO2-rich waters is largely unknown. Here we use an adaptation of the linear regression approach described in Feely et al (2008) along with the GO-SHIP Repeat Hydrography data sets from the northeast Pacific to establish an annually updated relationship between Canthro and potential density. This relationship was then used with the NOAA Ocean Acidification Program west coast cruise data sets from 2007, 2011, 2012 and 2013 to determine the spatial variations of Canthro in the upwelled water. Our results show large spatial differences in Canthro in surface waters along the coast with the lowest surface values (40-45 µmol kg-1) in strong upwelling regions of off northern California and southern Oregon and higher values (50-70 µmol kg-1) to the north and south. Canthro contributes an average of about 70% of the increased amount of dissolved inorganic carbon in the upwelled waters at the surface. In contrast, at 50 m the Canthro contribution is approximately 31% and at 100 m it averages about 16%. The remaining contributions are primarily due to respiration processes in the water that was upwelled and transported to coastal regions or underwent respiration processes that occurred locally during the course of the upwelling season. The uptake of Canthro has caused the aragonite saturation horizon to shoal by approximately 30-50 m since preindustrial period so that the undersaturated waters are well within the regions that affect the biological communities on the continental shelf.

  19. African Journals Online (AJOL)

    African Journals Online (AJOL)

    reviewed, African-published scholarly journals. Historically, scholarly information has flowed ... Research in Hospitality Management. Vol 7, No 1 (2018). AFRREV IJAH: An International Journal of Arts and Humanities. Vol 12, No 1 (2018). African ...

  20. African Journals Online (AJOL)

    African Journals Online (AJOL)

    2017). South African Family Practice. Vol 30, No 4 (2017). South African Journal of Clinical Nutrition. Vol 22, No 3 (2017). Journal of Endocrinology, Metabolism and Diabetes of South Africa. Vol 38, No 1 (2017). Nigerian Veterinary Journal.

  1. African Journals Online (AJOL)

    African Journals Online (AJOL)

    reviewed, African-published scholarly journals. Historically, scholarly information has flowed from North to South and from West to East. ... Featured Country: South Africa, Featured Journal: Southern African Linguistics and Applied Language Studies ...

  2. Liberalism and African Culture.

    Science.gov (United States)

    Sindima, Harvey

    1990-01-01

    Discusses the effect of liberalism on the African understanding of education, community, and religion. Describes ways in which the European intrusion, that is, colonial governments, schools, and churches, undermined traditional African life and thought. (DM)

  3. Depression and African Americans

    Science.gov (United States)

    ... You are here Home » Depression And African Americans Depression And African Americans Not “Just the Blues” Clinical ... or spiritual communities. Commonly Asked Questions about Clinical Depression How do I get help for clinical depression? ...

  4. African Studies Monographs

    African Journals Online (AJOL)

    The African Studies Monographs is a serial that promotes research and scholarship on the African perspective worldwide. This includes matters of philosophy, history, literature, arts and culture, environment, gender, politics, administration crisis management, etc.

  5. Micromorphology of a weathered granite near the Ría de Arosa (NW Spain)

    NARCIS (Netherlands)

    Bisdom, E.B.A.

    1966-01-01

    A detailed study has been made of several weathering profiles on the late-Hercynian Caldas de Reyes granite, NW-Spain. The field examination has been complemented by laboratory studies of large thin sections of hardened weathered material in conjunction with X-ray diffraction analyses. Three groups

  6. System-Level Sensitivity Analysis of SiNW-bioFET-Based Biosensing Using Lockin Amplification

    DEFF Research Database (Denmark)

    Patou, François; Dimaki, Maria; Kjærgaard, Claus

    2017-01-01

    carry out for the first time the system-level sensitivity analysis of a generic SiNW-bioFET model coupled to a custom-design instrument based on the lock-in amplifier. By investigating a large parametric space spanning over both sensor and instrumentation specifications, we demonstrate that systemwide...

  7. 10 years of protein crystallography at AR-NW12A beamline

    Science.gov (United States)

    Chavas, L. M. G.; Yamada, Y.; Hiraki, M.; Igarashi, N.; Matsugaki, N.; Wakatsuki, S.

    2013-03-01

    The exponential growth of protein crystallography can be observed in the continuously increasing demand for synchrotron beam time, both from academic and industrial users. Nowadays, the screening of a profusion of sample crystals for more and more projects is being implemented by taking advantage of fully automated procedures at every level of the experiments. The insertion device AR-NW12A beamline is one of the five macromolecular crystallography (MX) beamlines at the Photon Factory (PF). Currently the oldest MX beamline operational at the High Energy Accelerator Research Organization (KEK), the end-station was launched in 2001 as part of an upgrade of the PF Advanced Ring. Since its commissioning, AR-NW12A has been operating as a high-throughput beamline, slowly evolving to a multipurpose end-station for MX experiments. The development of the beamline took place about a decade ago, in parallel with a drastic development of protein crystallography and more general synchrotron technology. To keep the beamline up-to-date and competitive with other MX stations in Japan and worldwide, new features have been constantly added, with the goal of user friendliness of the various beamline optics and other instruments. Here we describe the evolution of AR-NW12A for its tenth anniversary. We also discuss the plans for upgrades for AR-NW12A, the future objectives in terms of the beamline developments, and especially the strong desire to open the beamline to a larger user community.

  8. Effect of ocean warming and acidification on a plankton community in the NW Mediterranean Sea

    NARCIS (Netherlands)

    Maugendre, L.; Gattuso, J.-P.; Louis, J.; de Kluijver, A.; Marro, S.; Soetaert, K.; Gazeau, F.

    2015-01-01

    The effect of ocean warming and acidification was investigated on a natural plankton assemblage from an oligotrophic area, the bay of Villefranche (NW Mediterranean Sea). The assemblage was sampled in March 2012 and exposed to the following four treatments for 12 days: control (~360 µatm, 14°C),

  9. Radon/helium studies for earthquake prediction N-W Himalaya

    International Nuclear Information System (INIS)

    Virk, H.S.

    1999-01-01

    The paper presents the preliminary data of radon monitoring stated in the Himalayan orogenic belt. Radon anomalies are correlated with microseismic activity in the N-W Himalaya. The He/Rn ratio will be used as a predictive tool for earthquakes

  10. Suspended sediment transport in the Gulf of Lions (NW Mediterranean): Impact of extreme storms and floods

    NARCIS (Netherlands)

    Ulses, C.; Estournel, C.; Durrieu de Madron, X.; Palanques, A.

    2008-01-01

    In situ observations were combined with 3D modeling to gain understanding of and to quantify the suspended sediment transport in the Gulf of Lions (NW Mediterranean Sea). The outputs of a hydrodynamic–sediment transport coupled model were compared to near-bottom current and suspended sediment

  11. Composition of the metazooplankton community and structure across the continental shelf off tropical NW Australia

    DEFF Research Database (Denmark)

    Jaspers, Cornelia; Nielsen, Torkel Gissel; Maar, Marie

    This talk focuses on the distribution pattern and grazing impact of different functional metazooplankton groups in a tropical marine ecosystem. We studied the metazooplankton distribution across the continental shelf from eutrophic mangrove areas to the oligotrophic deep blue ocean off NW Australia....... Small size classes impact on the primary...

  12. The role of tectonic inheritance in the morphostructural evolution of the Galicia continental margin and adjacent abyssal plains from digital bathymetric model (DBM) analysis (NW Spain)

    Science.gov (United States)

    Maestro, A.; Jané, G.; Llave, E.; López-Martínez, J.; Bohoyo, F.; Druet, M.

    2017-09-01

    The identification of recent major tectonic structures in the Galicia continental margin and adjacent abyssal plains was carried out by means of a quantitative analysis of the linear structures having bathymetric expression on the seabed. It was possible to identify about 5800 lineaments throughout the entire study area, of approximately 271,500 km2. Most lineaments are located in the Charcot and Coruña highs, in the western sector of the Galicia Bank, in the area of the Marginal Platforms and in the northern sector of the margin. Analysis of the lineament orientations shows a predominant NE-SW direction and three relative maximum directions: NW-SE, E-W and N-S. The total length of the lineaments identified is over 44,000 km, with a mode around 5000 m and an average length of about 7800 m. In light of different tectonic studies undertaken in the northwestern margin of the Iberian Peninsula, we establish that the lineaments obtained from analysis of the digital bathymetric model of the Galicia continental margin and adjacent abyssal plains would correspond to fracture systems. In general, the orientation of lineaments corresponds to main faults, tectonic structures following the directions of ancient faults that resulted from late stages of the Variscan orogeny and Mesozoic extension phases related to Triassic rifting and Upper Jurassic to Early Cretaceous opening of the North Atlantic Ocean. The N-S convergence between Eurasian and African plates since Palaeogene times until the Miocene, and NW-SE convergence from Neogene to present, reactivated the Variscan and Mesozoic fault systems and related physiography.

  13. South African Music Studies

    African Journals Online (AJOL)

    SAMUS: South African Music Studies is the official organ for the South African Society for Research in Music (SASRIM). It gives priority to the publication of research on South African music, but continues to represent the wider field of research interests in the country and in the rest of Africa. The journal invites work from any ...

  14. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journals OnLine (AJOL) is the world's largest and pre-eminent collection of peer-reviewed, African-published scholarly journals. Historically ... African Research Review; The Roles of Information Communication Technologies in Education: Review Article with Emphasis to the Computer and Internet Ethiopian Journal ...

  15. African Journals Online: Zimbabwe

    African Journals Online (AJOL)

    Items 1 - 12 of 12 ... African Journal of Social Work. The African Journal of Social Work is an international refereed journal that serves as a forum for exchanging ideas and knowledge and discussing issues relevant to social work practice, education and research in the African region. Producing 2 issues a year, the Journal is ...

  16. African Anthropologist: Submissions

    African Journals Online (AJOL)

    Author Guidelines. The African Anthropologist is a biannual journal of the Pan African Anthropological Association. It provides a forum for African and Africanist anthropologists to publish articles, research reports, review articles, and book reviews. The views expressed in any published material are those of the authors and ...

  17. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journals OnLine (AJOL) is the world's largest and pre-eminent collection of peer-reviewed, African-published scholarly journals. Historically ... Nnamdi Azikiwe University Journal of International Law and Jurisprudence; The Fulani Jihad and its Implication for National Integration and Development in Nigeria African ...

  18. African Journal of Urology

    African Journals Online (AJOL)

    The African Journal of Urology is the official journal of the Pan African Urological Surgeons' Association (PAUSA) The journal is a bilingual publication - publishing articles in English and French. The African Journal of Urology covers the whole scope of urology as well as the related basic sciences. In allignment with the ...

  19. Linguistic Imperialism: African Perspectives.

    Science.gov (United States)

    Phillipson, Robert

    1996-01-01

    Responds to an article on aspects of African language policy and discusses the following issues: multilingualism and monolingualism, proposed changes in language policy from the Organization for African Unity and South African initiatives, the language of literature, bilingual education, and whose interests English-language teaching is serving.…

  20. African Journals Online (AJOL)

    African Journals Online (AJOL)

    Madagascar Conservation & Development. Vol 11, No 3 (2017). South African Journal of Child Health. Vol 16, No 1 (2017). Agro-Science. Early View (Wetlands Special Issue). Madagascar Conservation & Development. Vol 9, No 4 (2017). African Journal of Health Professions Education. AJOL African Journals Online.

  1. African Journals Online (AJOL)

    African Journals Online (AJOL)

    South African Journal for Research in Sport, Physical Education and Recreation. Vol 17, No 4 (2017). African Health Sciences. Vol 6, No 1 (2015). Nigeria Journal of Pure and Applied Physics. Vol 5, No 2 (2017). Journal of Student Affairs in Africa. Vol 14, No 1 (2017). Annals of African Surgery. Vol 63, No 7-9 (2018).

  2. African Journals Online (AJOL)

    African Journals Online (AJOL)

    West African Journal of Applied Ecology. Vol 6, No 2 (2017). Filosofia Theoretica: Journal of African Philosophy, Culture and Religions. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and Conditions of Use · Contact AJOL ...

  3. African Journals Online (AJOL)

    African Journals Online (AJOL)

    reviewed, African-published scholarly journals. Historically, scholarly information has flowed from North to South and from West to East. It has also been difficult for African researchers to access the work of other African academics. In partnership with ...

  4. Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

    Science.gov (United States)

    Fischer, Gerhard; Romero, Oscar; Merkel, Ute; Donner, Barbara; Iversen, Morten; Nowald, Nico; Ratmeyer, Volker; Ruhland, Götz; Klann, Marco; Wefer, Gerold

    2016-05-01

    A more than two-decadal sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analysed with respect to deep ocean mass fluxes, flux components and their variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal timescales. High winter fluxes of biogenic silica (BSi), used as a measure of marine production (mostly by diatoms) largely correspond to a positive North Atlantic Oscillation (NAO) index (December-March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004-2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter and occasionally in summer/autumn enhanced particle sedimentation and carbon export on short timescales via the ballasting effect. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) might have weakened the relationships between fluxes and large-scale climatic oscillations. As phytoplankton biomass is high throughout the year, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by incorporating dust into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was observed for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all bulk fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997-1999 where low fluxes were obtained for almost 1 year during the warm El Niño and high fluxes in the following cold La Niña phase. For decadal timescales, Bakun (1990) suggested an intensification of coastal upwelling

  5. Storm Driven Upwelling Responsible for pCO2-rich Water Intrusion in the South Atlantic Bight

    Science.gov (United States)

    Noakes, S.; Gledhill, D. K.

    2016-02-01

    Gray's Reef National Marine Sanctuary (GRNMS) is located approximately 20 miles offshore Georgia along the inner to middle shelf of the South Atlantic Bight (SAB). The University of Georgia (UGA) and the Pacific Marine Environmental Lab have maintained a high resolution pCO2 system for almost a decade on the National Data Buoy Center's buoy moored at GRNMS. To support the surface monitoring and set the stage for benthic monitoring at GRNMS, UGA and GRNMS have established a seafloor observatory that monitors pCO2, pH and water quality parameters. Traditional thought had held that given the relatively shallow water depth at GRNMS, the pCO2 measured on the surface could be extrapolated to the seafloor and utilized to monitor the benthic community. However, seafloor pCO2 data collected to date have revealed unusual episodes of subsurface pCO2-rich water moving through GRNMS that had not been previously identified by surface monitoring. Many of these events correspond with major storms that have either formed off the SAB or passed nearby GRNMS. Based on the surface data collected to date, temperature driven seasonal pCO2 changes occur naturally on an annual scale in the SAB which also affects the pH. However, the storms appear to have induced upwelling of pCO2-rich water from the deep Atlantic Ocean pushing it inward over the long continental shelf towards GRNMS. The result of the upwelling is a sharp increase of subsurface pCO2 lasting only days to weeks as compared to the seasonal cycle. It is part of the natural weather patterns for storms to form off the SAB or pass nearby, but depending on if the storm frequency increases due to global climate change, this process may become more of an impact on the benthic community. How this affects the benthic community has yet to be determined, but it is clear that they have adapted to seasonal fluctuations for survival. These upwellings are obviously adding to the SAB total carbon budget and affecting the benthic water quality

  6. Receiver Function Imaging of Mantle Transition Zone Discontinuities Beneath the Tanzania Craton and Adjacent Segments of the East African Rift System

    Science.gov (United States)

    Sun, Muchen; Liu, Kelly H.; Fu, Xiaofei; Gao, Stephen S.

    2017-12-01

    The mantle transition zone (MTZ) discontinuities beneath the Tanzania Craton and the Eastern and Western Branches of the East African Rift System are imaged by stacking over 7,100 receiver functions. The mean thickness of the MTZ beneath the Western Branch and Tanzania Craton is about 252 km, which is comparable to the global average and is inconsistent with the existence of present-day thermal upwelling originating from the lower mantle. In contrast, beneath the Eastern Branch, an up to 30 km thinning of the MTZ is observed and is attributable to upwelling of higher temperature materials from either the upper MTZ or the lower mantle. The observations are in agreement with the hypothesis that rifting in Africa is primarily driven by gradients of gravitational potential energy and lateral variations of basal traction force along zones of significant changes of lithospheric thickness such as the edges of the Tanzania Craton.

  7. A model-based insight into the coupling of nitrogen and sulfur cycles in a coastal upwelling system

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar; Canfield, Donald Eugene; Fennel, Katja

    2014-01-01

    as a combination of organic matter oxidation by nitrite reduction and sulfide-driven denitrification. Mineralization coupled to heterotrophic nitrate reduction supplies ~48% of the ammonium required by anammox. Due to active sulfate reduction, model results suggest that sulfide-driven denitrification contributes......The biogeochemical cycling in oxygen-minimum zones (OMZs) is dominated by the interactions of microbial nitrogen transformations and, as recently observed in the Chilean upwelling system, also through the energetically less favorable remineralization of sulfate reduction. The latter process...... heterotrophic nitrate reduction and sulfate reduction are responsible for 47% and 36%, respectively, of organic remineralization in a 150 m deep zone below mixed layer. Anammox contributes to 61% of the fixed nitrogen lost to N2 gas, while the rest of the loss is through canonical denitrification...

  8. Seasonal variations in groundwater upwelling zones in a Danish lowland stream analyzed using Distributed Temperature Sensing (DTS)

    DEFF Research Database (Denmark)

    Matheswaran, Karthikeyan; Blemmer, Morten; Rosbjerg, Dan

    2014-01-01

    The distribution of groundwater inflows in a stream reach plays a major role in controlling the stream temperature, a vital component shaping the riverine ecosystem. In this study, the Distributed Temperature Sensing (DTS) system was installed in a small Danish lowland stream, Elverdamsåen......–night temperature difference were applied to three DTS datasets representing stream temperature responses to the variable meteorological and hydrological conditions prevailing in summer, winter and spring. The standard deviation criterion was useful to identify groundwater discharge zones in summer and spring......, antecedent precipitation and presence of fractured clayey till in the stream reach were deemed as the vital factors causing apparent seasonal variation in the locations of upwelling zones, prompting use of DTS not only in preconceived scenarios of large diurnal temperature change but rather a long...

  9. Seasonal sea surface temperature contrast between the Holocene and last glacial period in the western Arabian Sea (Ocean Drilling Project Site 723A): Modulated by monsoon upwelling

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Malmgren, B.A.

    were noticed within the Holocene period, which is attributed to the intense upwelling during the summer monsoon. This causes a lowering of SST to values similar to those of the winter season in analogy with the present day. A 3 degrees C rise in winter...

  10. Atypical delta sup(13) C signature in Globigerina bulloides at the ODP site 723A (Arabian Sea): Implications of environmental changes caused by upwelling

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D; Niitsuma, N.

    Drilling Program (ODP) site 723A located in the intense upwelling area along the Oman Margin, Arabian Sea is studied. The delta sup(13) C signature of G. bulloides from the Oman Margin during the last 19 ka ranges from -2.65 ppt to -1.13 ppt. Strikingly...

  11. A numerical investigation of the atmosphere-ocean thermal contrast over the coastal upwelling region of Cabo Frio, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Dourado, M. [Departamento de Meteorologia, Universidade Federal de Pelotas, Pelotas RS (Brazil)]. E-mail: marcelo_dourado@ufpel.edu.br; Pereira de Oliveira, A. [Departamento de Ciencias Atmosfericas, Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, (Brazil)

    2008-01-15

    An one-dimensional atmospheric second order closure model, coupled to an oceanic mixed layer model, is used to investigate the short term variation of the atmospheric and oceanic boundary layers in the coastal upwelling area of Cabo Frio, Brazil (23 degrees Celsius S, 42 degrees Celsius 08' W). The numerical simulations were carried out to evaluate the impact caused by the thermal contrast between atmosphere and ocean on the vertical extent and other properties of both atmospheric and oceanic boundary layers. The numerical simulations were designed taking as reference the observations carried out during the passage of a cold front that disrupted the upwelling regime in Cabo Frio in July of 1992. The simulations indicated that in 10 hours the mechanical mixing, sustained by a constant background flow of 10 m s-1, increases the atmospheric boundary layer in 214 m when the atmosphere is initially 2 K warmer than the ocean (positive thermal contrast observed during upwelling regime). For an atmosphere initially -2 K colder than the ocean (negative thermal contrast observed during passage of the cold front), the incipient thermal convection intensifies the mechanical mixing increasing the vertical extent of the atmospheric boundary layer in 360 m. The vertical evolution of the atmospheric boundary layer is consistent with the observations carried out in Cabo Frio during upwelling condition. When the upwelling is disrupted, the discrepancy between the simulated and observed atmospheric boundary layer heights in Cabo Frio during July of 1992 increases considerably. During the period of 10 hours, the simulated oceanic mixed layer deepens 2 m and 5.4 m for positive and negative thermal contrasts of 2 K and -2 K, respectively. In the latter case, the larger vertical extent of the oceanic mixed layer is due to the presence of thermal convection in the atmospheric boundary layer, which in turn is associated to the absence of upwelling caused by the passage of cold fronts

  12. Yearly variation of bacterial production in the Arraial do Cabo protection area (Cabo Frio upwelling region: an evidence of anthropogenic pressure

    Directory of Open Access Journals (Sweden)

    Sérgio A. Coelho-Souza

    2013-12-01

    Full Text Available Arraial do Cabo is where upwelling occurs more intensively on the Brazilian coast. Although it is a protection area it suffers anthropogenic pressure such as harbor activities and sporadic sewage emissions. Short-time studies showed a high variability of bacterial production (BP in this region but none of them evaluated BP during long periods in a large spatial scale including stations under different natural (upwelling and cold fronts and anthropogenic pressures. During 2006, we sampled surface waters 10 times (5 in upwelling and 5 in subsidence periods in 8 stations and we measured BP, temperature as well as the concentrations of inorganic nutrients, pigments and particulate organic matter (POM. BP was up to 400 times higher when sewage emissions were observed visually and it had a positive correlation with ammonia concentrations. Therefore, in 2007, we did two samples (each during upwelling and subsidence periods during sewage emissions in five stations under different anthropogenic pressure and we also measured particles abundance by flow cytometry. The 12 samples in the most impacted area confirmed that BP was highest when ammonia was higher than 2 μM, also reporting the highest concentrations of chlorophyll a and suspended particles. However, considering all measured variables, upwelling was the main disturbing factor but the pressure of fronts should not be neglected since it had consequences in the auto-heterotrophic coupling, increasing the concentrations of non fluorescent particles and POM. Stations clustered in function of natural and anthropogenic pressures degrees and both determined the temporal-spatial variability.

  13. african solutions to africa's problems? african approaches to peace ...

    African Journals Online (AJOL)

    Ilse van der Walt

    few Africans participated in the Pan-African congresses until the fifth one, held in. Manchester in 1945, where approximately one third of the delegates were African descendants. The first conference of the (then eight) independent African states was held in 1958 in Accra, Ghana. The Pan-African movement also enjoyed ...

  14. Spatio-temporal variability of inorganic and organic nutrients in five Galician rias (NW Spain

    Directory of Open Access Journals (Sweden)

    María Dolores Doval

    2013-01-01

    Full Text Available The spatial variability of inorganic (nitrate, nitrite, ammonium, phosphate and silicate and organic (dissolved organic carbon nutrients in five Galician rias (Vigo, Pontevedra, Arousa, Muros and Ares-Betanzos was assessed by considering average values for the upwelling and downwelling periods. Inner stations were significantly different from middle and outer stations, especially during the downwelling period. Spatial differences between the five rías, tested by means of a multivariate analysis, were found in both periods. The behaviour of inorganic and organic nutrient variables was also significantly different between periods with and without shellfish harvesting closures due to the occurrence of toxic phytoplankton species.

  15. Environmental ethics: An African understanding | Ojomo | African ...

    African Journals Online (AJOL)

    African Journal of Environmental Science and Technology. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 5, No 8 (2011) >. Log in or Register to get access to full text downloads.

  16. Active faults pattern and interplay in the Azerbaijan region (NW Iran)

    Science.gov (United States)

    Faridi, M.; Burg, J.-P.; Nazari, H.; Talebian, M.; Ghorashi, M.

    2017-07-01

    Northwest Iran is dominated by two main sets of active strike slip faults that accommodate oblique convergence between the Arabian and Iranian Plates. The best known are the right-lateral North-Tabriz, Qoshadagh, Maragheh and Zagros (Main Recent) strike slip Faults. This work reports that these dominant NW-SE to E-W striking faults are conjugate to smaller, NNE-SSW striking, left-lateral faults with minor dip slip component. All of these active faults displace Precambrian rock units, which suggests that they root in the crystalline basement of the NW Iranian microcontinent. Coulomb stress variance during co-seismic rupture along one of these faults may cause reactivation of the other faults. The minor set of left-lateral fault is therefore important to introduce in seismic risk assessment.

  17. Preliminary Feasibility Assessment of Integrating CCHP with NW Food Processing Plant #1: Modeling Documentation

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, Michael G.; Srivastava, Viraj; Wagner, Anne W.; Makhmalbaf, Atefe; Thornton, John

    2014-01-01

    The Pacific Northwest National Laboratory (PNNL) has launched a project funded by the Bonneville Power Association (BPA) to identify strategies for increasing industrial energy efficiency and reducing energy costs of Northwest Food Processors Association (NWFPA) plants through deployment of novel combinations and designs of variable-output combined heat and power (CHP) distributed generation (DG), combined cooling, heating and electric power (CCHP) DG and energy storage systems. Detailed evaluations and recommendations of CHP and CCHP DG systems will be performed for several Northwest (NW) food processing sites. The objective is to reduce the overall energy use intensity of NW food processors by 25% by 2020 and by 50% by 2030, as well as reducing emissions and understanding potential congestion reduction impacts on the transmission system in the Pacific Northwest.

  18. High dark inorganic carbon fixation rates by specific microbial groups in the Atlantic off the Galician coast (NW Iberian margin)

    NARCIS (Netherlands)

    Guerrero-Feijóo, E.; Sintes, E.; Herndl, G.J.; Varela, M.M.

    2018-01-01

    Bulk dark dissolved inorganic carbon (DIC) fixation rates were determined and compared to microbial heterotrophic production in subsurface, meso- and bathypelagic Atlantic waters off the Galician coast (NW Iberian margin). DIC fixation rates were slightly higher than heterotrophic production

  19. OXYGEN - AVERAGE SEABED CONSUMPTION from FIXED STATIONS From NW Atlantic (limit-40 W) from 19750429 to 19760126 (NODC Accession 9200021)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data consists of taut moorings designed for long-duration measurement of temperature/pressure time series in the deep ocean. These data were collected in NW...

  20. CRED SVP Drifting Buoy Argos_ID 30291 Data in the NW Hawaiian Islands, 20020920-20050105 (NODC Accession 0049436)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CRED SVP drifter Argos_ID 30291 was deployed in the region of NW Hawaiian Islands to assess ocean currents and sea surface temperature. SVP drifter data files...

  1. High dark inorganic carbon fixation rates by specific microbial groups in the Atlantic off the Galician coast (NW Iberian margin)

    NARCIS (Netherlands)

    Guerrero-Feijóo, E.; Sintes, E.; Herndl, G.J.; Varela, M.M.

    2018-01-01

    Bulk dark dissolved inorganic carbon (DIC) fixationrates were determined and compared to microbial heterotrophicproduction in subsurface, meso- andbathypelagic Atlantic waters off the Galician coast(NW Iberian margin). DIC fixation rates were slightlyhigher than heterotrophic production throughout

  2. Quality-intensity relationships of phosphorus in some soils from NW India

    International Nuclear Information System (INIS)

    Vig, A.C.; Dev, G.

    1975-01-01

    In a laboratory investigation, Q/I relationship of soil phosphorus in soils derived from four different agroclimatic regions of N.W. India have been worked out on the basis of adsorption studies, involving the use of radioactive phosphorus. These two parameters are related to each other by a Langmuir-like equation. The results indicate that for supply of P, the soils fall in the decreasing order of: Dalhousie, Ludhiana, Gurudaspur, Palampur. (author)

  3. GC determination of fatty acids in green beans grown in Galicia (N.W. Spain)

    OpenAIRE

    López Hernández, J.; González-Castro, M. J.; Simal-Lozano, J.; Vázquez-Blanco, M. E.; Vázquez-Orderiz, M. L.

    1996-01-01

    The concentrations of lauric, myristic, palmitic, palmitoleic, stearic, oleic, linoleic, linolenic, arachidic acids in green beans (Phaseolus vulgaris L.) grown in Galicia (N.W. Spain) were determinated by capillary gas chromatography (GC). Palmitic acid was the most abundant fatty acid component (113 mg/100 g. of lyophilizate; 35.2% of total fatty acid content), followed by linolenic acid (23.1%) and linoleic acid (21.6%).

    Se determinaron, mediante croma...

  4. The East African rift system

    Science.gov (United States)

    Chorowicz, Jean

    2005-10-01

    This overview paper considers the East African rift system (EARS) as an intra-continental ridge system, comprising an axial rift. It describes the structural organization in three branches, the overall morphology, lithospheric cross-sections, the morphotectonics, the main tectonic features—with emphasis on the tension fractures—and volcanism in its relationships with the tectonics. The most characteristic features in the EARS are narrow elongate zones of thinned continental lithosphere related to asthenospheric intrusions in the upper mantle. This hidden part of the rift structure is expressed on the surface by thermal uplift of the rift shoulders. The graben valleys and basins are organized over a major failure in the lithospheric mantle, and in the crust comprise a major border fault, linked in depth to a low angle detachment fault, inducing asymmetric roll-over pattern, eventually accompanied by smaller normal faulting and tilted blocks. Considering the kinematics, divergent movements caused the continent to split along lines of preexisting lithospheric weaknesses marked by ancient tectonic patterns that focus the extensional strain. The hypothesis favored here is SE-ward relative divergent drifting of a not yet well individualized Somalian plate, a model in agreement with the existence of NW-striking transform and transfer zones. The East African rift system comprises a unique succession of graben basins linked and segmented by intracontinental transform, transfer and accommodation zones. In an attempt to make a point on the rift system evolution through time and space, it is clear that the role of plume impacts is determinant. The main phenomenon is formation of domes related to plume effect, weakening the lithosphere and, long after, failure inducing focused upper mantle thinning, asthenospheric intrusion and related thermal uplift of shoulders. The plume that had formed first at around 30 Ma was not in the Afar but likely in Lake Tana region (Ethiopia

  5. Evidence for an Ancient Buried Landscape on the NW Rim of Hellas Basin, Mars

    Science.gov (United States)

    Crown, David A.; Bleamaster, Leslie F., III; Mest, Scott C.; Mustard, John F.; Vincendon, Mathieu

    2010-01-01

    Hellas basin is the largest (2000+ km across) well-preserved impact structure on Mars and its deepest depositional sink [e.g., 1]. The Hellas rim and adjacent highlands are of special interest given the possibility of paleolakes on the basin floor [2-4], recent studies of potential localized fluvial/lacustrine systems [2, 5-17], and evidence for phyllosilicates around and within impact craters north of the basin [18-26]. We are producing a 1:1.5M-scale geologic map of eight MTM quadrangles (-25312, -25307, -25302, -25297, -30312, -30307, -30302, -30297) along Hellas NW rim. The map region (22.5-32.5degS, 45- 65degE) includes a transect across the cratered highlands of Terra Sabaea, the degraded NW rim of Hellas, and basin interior deposits of NW Hellas Planitia. No previous mapping studies have focused on this region, although it has been included in earlier global and regional maps [27-29].

  6. Infant Mortality and African Americans

    Science.gov (United States)

    ... Profiles > Black/African American > Infant Health & Mortality Infant Mortality and African Americans African Americans have 2.2 ... to receive late or no prenatal care. Infant Mortality Rate Infant mortality rate per 1,000 live ...

  7. Differential responses of calcifying and non-calcifying epibionts of a brown macroalga to present-day and future upwelling pCO2.

    Directory of Open Access Journals (Sweden)

    Vincent Saderne

    Full Text Available Seaweeds are key species of the Baltic Sea benthic ecosystems. They are the substratum of numerous fouling epibionts like bryozoans and tubeworms. Several of these epibionts bear calcified structures and could be impacted by the high pCO2 events of the late summer upwellings in the Baltic nearshores. Those events are expected to increase in strength and duration with global change and ocean acidification. If calcifying epibionts are impacted by transient acidification as driven by upwelling events, their increasing prevalence could cause a shift of the fouling communities toward fleshy species. The aim of the present study was to test the sensitivity of selected seaweed macrofoulers to transient elevation of pCO2 in their natural microenvironment, i.e. the boundary layer covering the thallus surface of brown seaweeds. Fragments of the macroalga Fucus serratus bearing an epibiotic community composed of the calcifiers Spirorbis spirorbis (Annelida and Electra pilosa (Bryozoa and the non-calcifier Alcyonidium hirsutum (Bryozoa were maintained for 30 days under three pCO2 conditions: natural 460 ± 59 µatm, present-day upwelling1193 ± 166 µatm and future upwelling 3150 ± 446 µatm. Only the highest pCO2 caused a significant reduction of growth rates and settlement of S. spirorbis individuals. Additionally, S. spirorbis settled juveniles exhibited enhanced calcification of 40% during daylight hours compared to dark hours, possibly reflecting a day-night alternation of an acidification-modulating effect by algal photosynthesis as opposed to an acidification-enhancing effect of algal respiration. E. pilosa colonies showed significantly increased growth rates at intermediate pCO2 (1193 µatm but no response to higher pCO2. No effect of acidification on A. hirsutum colonies growth rates was observed. The results suggest a remarkable resistance of the algal macro-epibionts to levels of acidification occurring at present day upwellings in the Baltic

  8. Shift in the species composition of the diatom community in the eutrophic Mauritanian coastal upwelling: Results from a multi-year sediment trap experiment (2003-2010)

    Science.gov (United States)

    Romero, Oscar E.; Fischer, Gerhard

    2017-12-01

    A multiannual, continuous sediment trap experiment was conducted at the mooring site CBeu (Cape Blanc eutrophic, ca. 20 °N, ca. 18 °W; trap depth = 1256-1296 m) in the high-productive Mauritanian coastal upwelling. Here we present fluxes and the species-specific composition of the diatom assemblage, and fluxes of biogenic silica (BSi, opal) and total organic carbon (TOC) for the time interval June 2003-Feb 2010. Flux ranges of studied parameters are (i) total diatoms = 1.2 ∗ 108-4.7 ∗ 104 valves m-2 d-1 (average = 5.9 × 106 valves ± 1.4 × 107); (ii) BSi = 296-0.5 mg m-2 d-1 (average = 41.1 ± 53.5 mg m-2 d-1), and (iii) TOC = 97-1 mg m-2 d-1 (average = 20.5 ± 17.8 mg m-2 d-1). Throughout the experiment, the overall good match of total diatom, BSi and TOC fluxes is reasonably consistent and reflects well the temporal occurrence of the main Mauritanian upwelling season. Spring and summer are the most favorable seasons for diatom production and sedimentation: out of the recorded 14 diatom maxima of different magnitude, six occurred in spring and four in summer. The diverse diatom community at site CBeu is composed of four main assemblages: benthic, coastal upwelling, coastal planktonic and open-ocean diatoms, reflecting different productivity conditions and water masses. A striking feature of the temporal variability of the diatom populations is the persistent pattern of seasonal groups' contribution: benthic and coastal upwelling taxa dominated during the main upwelling season in spring, while open-ocean diatoms were more abundant in fall and winter, when the upper water column becomes stratified, upwelling relaxes and productivity decreases. The relative abundance of benthic diatoms strongly increased after 2006, yet their spring-summer contribution remained high until the end of the trap experiment. The occurrence of large populations of benthic diatoms at the hemipelagic CBeu site is interpreted to indicate transport from shallow waters via nepheloid

  9. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

    Directory of Open Access Journals (Sweden)

    E. Gutknecht

    2013-06-01

    Full Text Available The Eastern Boundary Upwelling Systems (EBUS contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs, EBUS represent key regions for the oceanic nitrogen (N cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (northern Benguela using the high-resolution hydrodynamic ROMS model. We present here a validation using in situ and satellite data as well as diagnostic metrics and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate, and chlorophyll a concentrations, and the rates of microbial processes (e.g, NH4+ and NO2− oxidation, NO3− reduction, and anammox as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking, and nitrification play a key role for the low-oxygen water content, N loss, and N2O concentrations in the OMZ. Moreover, the explicit parameterization of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is necessary to improve the representation of microbial activity linked with the OMZ. The simulated minimum oxygen

  10. Nitrogen fixation in sediments along a depth transect through the Eastern Boundary Upwelling Systems off Peru and Mauritania

    Science.gov (United States)

    Gier, J.; Sommer, S.; Löscher, C. R.; Dale, A.; Schmitz, R. A.; Treude, T.

    2015-12-01

    The distribution of benthic nitrogen (N2) fixation and its relevance for N cycling in the Eastern Boundary Upwelling Systems (EBUS) are still unknown. Recent studies confirm that benthic N2 fixation can be coupled to sulfate reduction (SR) and that several species of sulfate reducing bacteria have the genetic ability to fix N due to the presence of the gene encoding for the nitrogenase enzyme. We investigated benthic N2 fixation and SR in the Peruvian oxygen minimum zone at 12°S and in the Mauritanian upwelling system at 18°N along a depth transect. Sediments were retrieved by a multicorer and a benthic lander at six stations in both regions. Benthic N2 fixation occurred throughout the sediment in both EBUS. Off Peru the highest integrated (0-20 cm) N2 fixation rate of 0.4 mmol N/m2/d was measured inside the core of the OMZ at 253 m water depth. Off Mauritania the highest integrated (0-20 cm) N2 fixation rate of 0.15 mmol N/m2/d was measured at 90 m, coinciding with a low bottom water oxygen concentration (30 μM). N2 fixation depth profiles often overlapped with SR activity. Moreover, sequencing data yielded insights into the composition and diversity of the nifH gene pool in EBUS sediments. Interestingly, detected sequences in both EBUS clustered with SR bacteria, such as Desulfovibrio vulgaris and several of the novel detected clades belonged to uncultured diazotrophs. Our results suggest that N2 fixation and SR were coupled to a large extent in both regions. However, potential environmental factors controlling benthic diazotrophs in the EBUS appear to be the availability of sulfide and organic matter. Additionally, no inhibition of N2 fixation at high ammonium concentrations was found, which highlights gaps in our knowledge regards the interaction between ammonium availability and diazotrophy. Our results contribute to a better understanding of N cycling in EBUS sediments and sources of fixed N.

  11. BSRs Elevated by Fluid Upwelling on the Upper Amazon Fan : Bottom-up Controls on Gas Hydrate Stability

    Science.gov (United States)

    Praeg, D.; Silva, C. G.; dos Reis, A. T.; Ketzer, J. M.; Unnithan, V.; Perovano Da Silva, R. J.; Cruz, A. M.; Gorini, C.

    2017-12-01

    The stability of natural gas hydrate accumulations on continental margins has mainly been considered in terms of changes in seawater pressures and temperatures driven from above by climate. We present evidence from the Amazon deep-sea fan for stability zone changes driven from below by fluid upwelling. A grid of 2D and 3D multichannel seismic data show the upper Amazon fan in water depths of 1200-2000 m to contain a discontinuous bottom-simulating seismic reflection (BSR) that forms `patches' 10-50 km wide and up to 140 km long, over a total area of at least 5000 km2. The elongate BSR patches coincide with anticlinal thrust-folds that record on-going gravitational collapse of the fan above décollements at depths of up to 10 km. The BSR lies within 100-300 m of seafloor, in places rising beneath features that seafloor imagery show to be pockmarks and mud volcanoes, some venting gas to the water column. The BSR patches are up to 500 m shallower than predicted for methane hydrate based on geothermal gradients as low as 17˚C/km measured within the upper fan, and inversion of the BSR to obtain temperatures at the phase boundary indicates gradients 2-5 times background levels. We interpret the strongly elevated BSR patches to record upwelling of warm gas-rich fluids through thrust-fault zones 101 km wide. We infer this process to favour gas hydrate occurrences that are concentrated in proportion to flux and locally pierced by vents, and that will be sensitive to temporal variations in the upward flux of heat and gas. Thus episodes of increased flux, e.g. during thrusting, could dissociate gas hydrates to trigger slope failures and/or enhanced gas venting to the ocean. Structurally-driven fluid flow episodes could account for evidence of recurrent large-scale failures from the compressive belt on the upper fan during its Neogene collapse, and provide a long-term alternative to sea level triggering. The proposed mechanism of upward flux links the distribution and

  12. Combined impact of ocean acidification and corrosive waters in a river-influenced coastal upwelling area off Central Chile

    Science.gov (United States)

    Vargas, C.; De La Hoz, M.; San Martin, V.; Contreras, P.; Navarro, J. M.; Lagos, N. A.; Lardies, M.; Manríquez, P. H.; Torres, R.

    2012-12-01

    Elevated CO2 in the atmosphere promotes a cascade of physical and chemical changes affecting all levels of biological organization, and the evidence from local to global scales has shown that such anthropogenic climate change has triggered significant responses in the Earth's biota. The increased concentration of CO2 is likely to cause a corresponding increase in ocean acidification (OA). In addition, economically valuable shellfish species predominantly inhabit coastal regions both in natural stocks and/or in managed stocks and farming areas. Many coastal ecosystems may experience seawater pCO2 levels significantly higher than expected from equilibrium with the atmosphere, which in this case are strongly linked to biological processes and/or the impact of two important processes; river plumes and coastal upwelling events, which indeed interplay in a very dynamic way on continental shelves, resulting in both source or sink of CO2 to the atmosphere. Coastal ecosystems receive persistent acid inputs as a result of freshwater discharges from river basins into the coastal domain. In this context, since shellfish resources and shellfish aquaculture activities predominantly occur in nearshore areas, it is expected that shellfish species inhabiting river-influenced benthic ecosystems will be exposed persistently to acidic conditions that are suboptimal for its development. In a wider ecological context, little is also known about the potential impacts of acid waters on the performance of larvae and juveniles of almost all the marine species inhabiting this benthic ecosystem in Eastern Southern Pacific Ocean. We present here the main results of a research study aimed to investigate the environmental conditions to which economically valuable calcifiers shellfish species are exposed in a river-influenced continental shelf off Central Chile. By using isotopic measurements in the dissolved inorganic carbon (DIC) pool (d13C-DIC) we showed the effect of the remineralization of

  13. Zooplankton associated with the oxygen minimum zone system in the northern upwelling region of Chile during March 2000

    Science.gov (United States)

    Escribano, Ruben; Hidalgo, Pamela; Krautz, Cristina

    2009-07-01

    Zooplankton in the coastal upwelling region off northern Chile may play a significant biogeochemical role by promoting carbon flux into the subsurface OMZ (oxygen minimum zone). This work identifies the dominant zooplankton species inhabiting the area influenced by the OMZ in March 2000 off Iquique (20°S, northern Chile). Abundance and vertical distribution studies revealed 17 copepod and 9 euphausiid species distributed between the surface and 600 m at four stations sampled both by day and by night. Some abundant species remained in the well-oxygenated upper layer (30 m), with no evidence of diel vertical migration, apparently restricted by a shallow (40-60 m) oxycline. Other species, however, were found closely associated with the OMZ. The large-sized copepod Eucalanus inermis was found below the oxycline and performed diel vertical migrations into the OMZ, whereas the very abundant Euphausia mucronata performed extensive diel vertical migrations between the surface waters and the core of the OMZ (200 m), even crossing it. A complete assessment of copepods and euphausiids revealed that the whole sampled water column (0-600 m) is occupied by distinct species having well-defined habitats, some of them within the OMZ. Ontogenetic migrations were evident in Eucalanidae and E. mucronata. Estimates of species biomass showed a substantial (>75% of total zooplankton biomass) daily exchange of C between the photic layer and the OMZ. Both E. inermis and E. mucronata can actively exchange about 37.8 g C m -2 d -1 between the upper well-oxygenated (0-60 m) layer and the deeper (60-600 m) OMZ layer. This migrant biomass may contribute about 7.2 g C m -2 d -1 to the OMZ system through respiration, mortality, and production of fecal pellets within the OMZ. This movement of zooplankton in and out of the OMZ, mainly as a result of the migratory behavior of E. mucronata, suggests a very efficient mechanism for introducing large amounts of freshly produced carbon into the OMZ

  14. Structural analysis of Nalagarh lobe, NW Himalaya: implication of thrusting across tectonic edge of NW limb of Nahan salient, Himachal Pradesh, India

    Science.gov (United States)

    Bhakuni, S. S.; Philip, G.; Suresh, N.

    2017-07-01

    The Main Boundary Fault (MBF), convex towards southwest, forms the leading edge of the Nahan salient. Near the southern end of an oblique ramp, a lobe-shaped physiographic front, named in this work as Nalagarh lobe, has developed across NW limb of salient. The lobe has formed across the MBF that separates the hanging wall Lower Tertiary Dharmsala rocks from the footwall Upper Tertiary Siwalik rocks and overlying Quaternaries. In front of lobe, thrust fault splays (Splay-1 and Splay-2) and associated tectonic fabrics have developed within the Late Pleistocene fan deposit. Structural elements developed across the front of Nalagarh lobe are analysed with reference to evolution of lobe. An unweathered 15-m-high hanging wall or wedge top forms the uplifted and rejuvenated bedrock fault scarp of the MBF. Below the MBF, the fan deposit has underthrust along Splay-1. Later the Splay-2 formed within fan deposit near south of Splay-1. Geometry of the overturned limb of tight to isoclinal fault propagation fold, formed on Splay-2 plane, suggests that the fold formed by normal drag, produced by intermittent fault-slips along Splay-2. The displacement along Splay-2 offset the marker bed to 1 m by which some clasts rotated parallel to the traces of brittle axial planes of fold. The variable fold geometry and style of deformation are analysed along length of thrust splays for 5 km. It is revealed that the lobe is bounded by transverse thrust faults along its NW and SE margins. The geometry of salient and oblique ramp suggests that the transverse thrust faults and associated transverse folds formed by right-lateral displacement along the NW limb of the salient. Marking the northern margin of the intermontane piggyback basin of Pinjaur dun, the MBF is interpreted to be an out-of-sequence thrust that has brought up the Lower Tertiary Dharmsala rocks over the Late Pleistocene fan deposit. The geometry of lobe and its bounding transverse faults suggest that faults are intimately

  15. The African Union's notion of 'African solutions to African problems ...

    African Journals Online (AJOL)

    intervention of the UN and France in Côte d'Ivoire; and the North Atlantic ... 2 Before NATO intervened as an organisation, its individual members including France, .... states. A culture of impunity and indifference was cultivated and became entrenched in the international relations of the African countries. Thus, learning.

  16. African agricultural trade

    DEFF Research Database (Denmark)

    Jensen, Hans Grinsted; Sandrey, Ron

    2015-01-01

    This article starts with a profile of African agricultural trade. Using the pre-release version 9.2 of the GTAP database, we then show that the results for tariff elimination on intra-African trade are promising, but these tariff barriers are not as significant as the various trade-related barriers...

  17. African Journals Online: Armenia

    African Journals Online (AJOL)

    African Journals Online: Armenia. Home > African Journals Online: Armenia. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  18. African Journals Online: Switzerland

    African Journals Online (AJOL)

    African Journals Online: Switzerland. Home > African Journals Online: Switzerland. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  19. African Journals Online (AJOL)

    African Journals Online (AJOL)

    The abnormal chest X-ray – when to refer to a specialist. Continuing Medical ... South African Journal of Education; The functions of school governing bodies in managing school finances. South African Journal ... EJOTMAS: Ekpoma Journal of Theatre and Media Arts; Clinical approach to the floppy child. Continuing Medical ...

  20. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journals OnLine (AJOL) is the world's largest and pre-eminent collection of peer-reviewed, African-published scholarly journals. Historically, scholarly information ... Ethiopian Journal of Education and Sciences; Advertising practice in Nigeria: Development, new trends, challenges and prospects. EJOTMAS: Ekpoma ...

  1. African Journals Online: Andorra

    African Journals Online (AJOL)

    African Journals Online: Andorra. Home > African Journals Online: Andorra. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  2. African Journals Online: Bahamas

    African Journals Online (AJOL)

    African Journals Online: Bahamas. Home > African Journals Online: Bahamas. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  3. African Journals Online (AJOL)

    African Journals Online (AJOL)

    Mizan Law Review; The competitive advantage of nations: is Porter's Diamond Framework a new theory that explains the international competitiveness of countries? ... African Journal of Biotechnology; The application of just administrative action in the South African environmental governance sphere: An analysis of some ...

  4. African Journals Online (AJOL)

    African Journals Online (AJOL)

    Continuing Medical Education; The competitive advantage of nations: is Porter's Diamond Framework a new theory that explains the international competitiveness of ... African Journal of Biotechnology; The application of just administrative action in the South African environmental governance sphere: An analysis of some ...

  5. African Journals Online: Kiribati

    African Journals Online (AJOL)

    African Journals Online: Kiribati. Home > African Journals Online: Kiribati. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access. Afghanistan ...

  6. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journals OnLine (AJOL) is the world's largest and pre-eminent collection of peer-reviewed, African-published scholarly journals. Historically, scholarly information has ... Africa Development; Advertising practice in Nigeria: Development, new trends, challenges and prospects. EJOTMAS: Ekpoma Journal of Theatre ...

  7. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journals OnLine (AJOL) is the world's largest and pre-eminent collection of peer-reviewed, African-published scholarly journals. Historically, scholarly ... Arab Journal of Nephrology and Transplantation; Advertising practice in Nigeria: Development, new trends, challenges and prospects. EJOTMAS: Ekpoma Journal ...

  8. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journals OnLine (AJOL) is the world's largest and pre-eminent collection of peer-reviewed, African-published scholarly journals. Historically, scholarly ... AFRREV IJAH: An International Journal of Arts and Humanities; Advertising practice in Nigeria: Development, new trends, challenges and prospects. EJOTMAS: ...

  9. African Journals Online (AJOL)

    African Journals Online (AJOL)

    South African Journal of Clinical Nutrition. Vol 22, No 3 (2017). Journal of Endocrinology, Metabolism and Diabetes of South Africa. Vol 38, No 1 (2017). Nigerian Veterinary Journal. Vol 28, No 2 (2017). Legon Journal of the Humanities. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians ...

  10. African Journals Online (AJOL)

    African Journals Online (AJOL)

    South African Journal of Clinical Nutrition. Vol 22, No 3 (2017). Journal of Endocrinology, Metabolism and Diabetes of South Africa. Vol 38, No 1 (2017). Nigerian Veterinary Journal. Vol 28, No 2 (2017). Legon Journal of the Humanities. Vol 19, No 2 (2017). Nigerian Journal of Animal Science. AJOL African Journals Online.

  11. African Journals Online (AJOL)

    African Journals Online (AJOL)

    South African Journal of Clinical Nutrition. Vol 22, No 3 (2017). Journal of Endocrinology, Metabolism and Diabetes of South Africa. Vol 38, No 1 (2017). Nigerian Veterinary Journal. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners ...

  12. African Journals Online: Uganda

    African Journals Online (AJOL)

    Items 1 - 12 of 12 ... African Crop Science Journal. The African Crop Science Journal, a quarterly publication, publishes original research papers dealing with all aspects of crop agronomy, production, genetics and breeding, germplasm, crop protection, post harvest systems and utilisation, agro-forestry, crop-animal interactions ...

  13. African Journals Online (AJOL)

    African Journals Online (AJOL)

    In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and to the rest of the world. ... Featured Country: Nigeria, Featured Journal: Journal of Educational Foundations ... Journal of Agriculture and Social Research (JASR).

  14. African Journals Online (AJOL)

    African Journals Online (AJOL)

    In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and to the rest of the world. ... AFRREV IJAH: An International Journal of Arts and Humanities; Human Rights under the Ethiopian Constitution: A Descriptive Overview

  15. Annals of African Surgery

    African Journals Online (AJOL)

    The goal of the Annals of African Surgery is to provide a medium for the exchange of current information between surgeons in the African region. The journal embraces surgery in all its aspects; basic science, clinical research, experimental research, surgical education. It will assist surgeons in the region to keep abreast of ...

  16. African Journals Online: Vanuatu

    African Journals Online (AJOL)

    African Journals Online: Vanuatu. Home > African Journals Online: Vanuatu. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  17. African Journals Online: Grenada

    African Journals Online (AJOL)

    African Journals Online: Grenada. Home > African Journals Online: Grenada. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  18. African Journals Online: Barbados

    African Journals Online (AJOL)

    African Journals Online: Barbados. Home > African Journals Online: Barbados. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  19. African Journals Online: India

    African Journals Online (AJOL)

    African Journals Online: India. Home > African Journals Online: India. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access. Afghanistan ...

  20. African American Suicide

    Science.gov (United States)

    African American Suicide Fact Sheet Based on 2012 Data (2014) Overview • In 2012, 2,357 African Americans completed suicide in the U.S. Of these, 1,908 (80. ... rate of 9.23 per 100,000). The suicide rate for females was 1.99 per 100, ...

  1. African Journals Online: Malta

    African Journals Online (AJOL)

    African Journals Online: Malta. Home > African Journals Online: Malta. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access. Afghanistan ...

  2. African Journals Online: Guernsey

    African Journals Online (AJOL)

    African Journals Online: Guernsey. Home > African Journals Online: Guernsey. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  3. African Journals Online: Liechtenstein

    African Journals Online (AJOL)

    African Journals Online: Liechtenstein. Home > African Journals Online: Liechtenstein. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  4. African Journals Online: Belgium

    African Journals Online (AJOL)

    African Journals Online: Belgium. Home > African Journals Online: Belgium. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  5. African Journals Online (AJOL)

    African Journals Online (AJOL)

    In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and to the rest of the world. AJOL is a Non-Profit Organisation based ... International Journal of Engineering, Science and Technology. Vol 30, No 1 (2018): Volume 30 ...

  6. African Journals Online (AJOL)

    African Journals Online (AJOL)

    In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and to the rest of the world. AJOL is a Non-Profit Organisation based ... International Journal of Engineering, Science and Technology. Vol 4, No 1 (2012). International ...

  7. African Journals Online (AJOL)

    African Journals Online (AJOL)

    In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and to the rest of the world. AJOL is a Non-Profit Organisation ... Featured Country: Nigeria, Featured Journal: Journal of Applied Science, Engineering and Technology ...

  8. African Journals Online: Aruba

    African Journals Online (AJOL)

    African Journals Online: Aruba. Home > African Journals Online: Aruba. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access. Afghanistan ...

  9. African Journals Online: Kazakhstan

    African Journals Online (AJOL)

    African Journals Online: Kazakhstan. Home > African Journals Online: Kazakhstan. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access ...

  10. African Literature as Celebration.

    Science.gov (United States)

    Achebe, Chinua

    1989-01-01

    Describes the Igbo tradition of "Mbari," a communal creative enterprise that celebrates the world and the life lived in it through art. Contrasts the cooperative, social dimension of pre-colonial African culture with the exclusion and denial of European colonialism, and sees new African literature again celebrating human presence and…

  11. African Journals Online (AJOL)

    African Journals Online (AJOL)

    Featured Country: South Africa, Featured Journal: Journal for Juridical Science ... The Roles of Information Communication Technologies in Education: Review Article with Emphasis to the Computer and Internet Ethiopian ... South African Journal of Education; Methods of Conflict Resolution in African Traditional Society

  12. African Journals Online: Nigeria

    African Journals Online (AJOL)

    Items 1 - 50 of 221 ... African Journal of Library, Archives and Information Science is established mainly to provide a forum for librarians, archivists, documentalists, information scientists and other information related professionals in Africa to report their research findings but with emphasis on African setting. The Journal is ...

  13. African Journals Online (AJOL)

    African Journals Online (AJOL)

    Continuing Medical Education; Educational leadership and management: theory, policy and practice. South African Journal of Education; The competitive advantage of nations: is Porter's Diamond Framework a new theory that explains the international competitiveness of countries? Southern African Business Review; The ...

  14. African Zoology: Editorial Policies

    African Journals Online (AJOL)

    Focus and Scope. African Zoology, a peer-reviewed research journal, publishes original scientific contributions and critical reviews that focus principally on African fauna in terrestrial, freshwater, and marine ecosystems. Research from other regions that advances practical and theoretical aspects of zoology will be ...

  15. East African Medical Journal

    African Journals Online (AJOL)

    Journal Homepage Image. The East African Medical Journal is intended for publication of papers on original work and reviews of all aspects of medicine. Communications bearing on clinical and basic research on problems relevant to East Africa and other African countries will receive special attention. The EAMJ has a 3 ...

  16. African Journals Online: Mozambique

    African Journals Online (AJOL)

    African Journal of Governance and Development. The African Journal of Governance and Development is a multidisciplinary publication that seeks to bring academic researchers from beyond territorial and regional boundaries to share scientific knowledge focused on the interface of governance and development.

  17. African Journals Online (AJOL)

    African Journals Online (AJOL)

    Bulletin of Animal Health and Production in Africa. Vol 22, No 2 (2017). East and Central African Journal of Surgery. Vol 6, No 1 (2018). International Journal of Pedagogy, Policy and ICT in Education. Vol 64, No 3 (2016). Bulletin of Animal Health and Production in Africa. Vol 26, No 1 (2018). African Crop Science Journal.

  18. African Journals Online (AJOL)

    African Journals Online (AJOL)

    In partnership with hundreds of journals from all over the continent, AJOL works to change this, so that African-origin research output is available to Africans and to ... Ergonomics SA. Vol 9, No 1 (2017). Inkanyiso: Journal of Humanities and Social Sciences. Vol 14, No 5 (2017). Journal of Pharmaceutical and Allied Sciences.

  19. Keeping African Masks Real

    Science.gov (United States)

    Waddington, Susan

    2012-01-01

    Art is a good place to learn about our multicultural planet, and African masks are prized throughout the world as powerfully expressive artistic images. Unfortunately, multicultural education, especially for young children, can perpetuate stereotypes. Masks taken out of context lose their meaning and the term "African masks" suggests that there is…

  20. African Art Teaching Strategies.

    Science.gov (United States)

    Chanda, Jacqueline

    Three different models for the teaching of African art are presented in this paper. A comparison of the differences between the approaches of Western art historians and African art historians informs the articulation of the three models--an approach for determining style, another for dealing with analysis, and a third for synthetic interpretation.…

  1. Inspired by African Art.

    Science.gov (United States)

    Heintz, June Rutledge

    1991-01-01

    Argues that African art helps children to learn vital art concepts and enlarges their understanding of the role of art in human culture. Outlines a unit on African art based on animals. Students created fabric designs and illustrated folktales and fables. Provides a list of free resources. (KM)

  2. Archives: African Health Sciences

    African Journals Online (AJOL)

    Items 1 - 50 of 67 ... Archives: African Health Sciences. Journal Home > Archives: African Health Sciences. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives. 1 - 50 of 67 Items, 1 2 > >> ...

  3. African Journals Online (AJOL)

    African Journals Online (AJOL)

    Ethiopian Journal of Education and Sciences; Conflicts in Africa: Meaning, Causes, Impact and Solution African Research Review; The competitive advantage of nations: is Porter's Diamond Framework a new theory that explains the international competitiveness of countries? Southern African Business Review; The Rise of ...

  4. African Journals Online (AJOL)

    African Journals Online (AJOL)

    Legon Journal of the Humanities. Vol 19, No 2 (2017). Nigerian Journal of Animal Science. Vol 36, No 1 (2017). African Journal of Neurological Sciences. Vol 86, No 2 (2017). Tanzania Journal of Forestry and Nature Conservation. Vol 37, No 4 (2016). Nigerian Veterinary Journal. Vol 33 (2017). Southern African Journal of ...

  5. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journals OnLine (AJOL) is the world's largest and pre-eminent collection of peer-reviewed, African-published scholarly journals. Historically, scholarly information has flowed ... Thought and Practice; Advertising practice in Nigeria: Development, new trends, challenges and prospects. EJOTMAS: Ekpoma Journal of ...

  6. African Health Sciences

    African Journals Online (AJOL)

    African Health Sciences is an open access, free online, internationally refereed journal publishing original articles on research, clinical practice, public health, policy, planning, implementation and evaluation, in the health and related sciences relevant to Africa and the tropics. African Health Sciences acknowledges support ...

  7. African Journals Online (AJOL)

    African Journals Online (AJOL)

    It has also been difficult for African researchers to access the work of other African academics. In partnership with ... AJOL hosts 521 Journals, including 224 Open Access Journals; The site has 12 752 Issues containing 149 326 Abstracts. There are 143 542 Full ... Marang: Journal of Language and Literature. Vol 28, No 1 ...

  8. Annals of African Medicine

    African Journals Online (AJOL)

    The Annals of African Medicine is published by the Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria and the Annals of African Medicine Society. The Journal is intended to serve as a medium for the publication of research findings in the broad field of Medicine in Africa and other developing countries, and ...

  9. African Journals Online (AJOL)

    African Journals Online (AJOL)

    African Journal of Oral Health. Vol 35, No 1-2 (2017). Egyptian Journal of Biochemistry and Molecular Biology. Vol 7, No 3 (2017). African Journal of Chemical Education. Vol 8, No 2 (2017): Journal of Language, Technology & Entrepreneurship in Africa. Journal of Language, Technology & Entrepreneurship in Africa.

  10. African Journals Online: Ireland

    African Journals Online (AJOL)

    African Journals Online: Ireland. Home > African Journals Online: Ireland. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This Journal is Open Access. Afghanistan ...

  11. Archives: African Studies Monographs

    African Journals Online (AJOL)

    Archives: African Studies Monographs. Journal Home > Archives: African Studies Monographs. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives. 1 - 5 of 5 Items. 2007. Vol 8 (2007) ...

  12. Particulate dimethylsulfoniopropionate and dimethylsulfoxide in relation to iron availability and algal community structure in the Peru Upwelling System

    Energy Technology Data Exchange (ETDEWEB)

    Riseman, S.F.; DiTullio, G.R. [Charleston College, Charleston, SC (United States). Hillings Marine Lab.

    2004-05-01

    This study examined one aspect of atmospheric-ocean processes which may impact global climate change. In particular, it examined biogeochemical cycling of sulfur compounds such as dimethyl sulfide (DMS) in the marine environment. The study examined the impact of iron on phytoplankton biogenic sulfur production, physiological status and community structure in the Peruvian Upwelling System. In September 2000, two transects were conducted off the Peru coast to measure algal pigments, photosynthetic efficiency, macronutrients, dissolved iron concentrations, temperature and salinity. Vertical profiles of particulate dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) were also measured. Chlorophyll 'a' biomass was found to decrease substantially across the shelf, while DMSP and DMSO concentrations were found to be higher at the offshore stations, most likely because of the lower iron concentrations and the shift from diatom-dominated communities to ones dominated by cryptophytes and haptophytes. Similar patterns were observed during a shipboard iron-addition incubation experiment. The observations support an antioxidant function for DMSP and DMSO. The study showed that concentrations of dissolved iron can influence the net concentrations of DMSO and DMSO in oceans. It was suggested that more laboratory work is needed to address the physiological response of different taxa to iron stress in order to accurately interpret this field data. 46 refs., 5 tabs., 8 figs.

  13. Relationships between High River Discharge, Upwelling Events, and Bowhead Whale (Balaena mysticetus) Occurrence in the Central Alaskan Beaufort Sea

    Science.gov (United States)

    Clarke, J.; Okkonen, S. R.; Potter, R. A.

    2016-02-01

    Aerial surveys of bowhead whales have been conducted in September in the central Alaskan Beaufort Sea (144°W-150°W) for several decades. These surveys, co-managed by BOEM and NOAA, have documented bowhead whale distribution that is almost exclusively on the continental shelf, generally from feeding behavior occasionally observed. In September 2014, several hundred bowhead whales were observed feeding on several occasions within a few kilometers of local barrier islands. This is an unusual situation that has been observed in September in only one other year (1997). To investigate local conditions that might be conducive to increased bowhead whale occurrence, freshwater discharge data from the Sagavanirktok and Kuparak rivers, surface wind data, and suspended sediment data obtained from MODIS satellite imagery were analyzed and compared to bowhead whale observations for September 1989-2014. Results indicate that anomalously high freshwater river discharge coupled with prior upwelling events, based on surface winds >5.4 m s-1, may combine to promote the aggregation of bowhead whale prey on the shallow shelf. When these two conditions were met, whales were sighted more frequently, were more likely to be in groups of ≥2 animals, and be closer to shore. Conversely, when either of the two conditions was not met, whales were sighted less frequently, more likely to be single animals, and be farther from shore. These results underscore annual variation during the bowhead whale fall migration and the physical oceanography processes that may be related to whale distribution and behavior.

  14. An upwelling model for the Phosphoria sea: A Permian, ocean-margin sea in the northwest United States

    Science.gov (United States)

    Piper, D.Z.; Link, P.K.

    2002-01-01

    The Permian Phosphoria Formation, a petroleum source rock and world-class phosphate deposit, was deposited in an epicratonic successor basin on the western margin of North America. We calculate the seawater circulation in the basin during deposition of the lower ore zone in the Meade Peak Member from the accumulation rates of carbonate fluorapatite and trace elements. The model gives the exchange rate of water between the Phosphoria sea and the open ocean to the west in terms of an upwelling rate (84 m yr-1) and residence time (4.2 yr) of seawater in the basin. These hydrographic properties supported a mean rate of primary productivity of 0.87 g m-2 d-1 of carbon in the uppermost few tens of meters of the water column (the photic zone) and denitrifying redox conditions in the bottom water (below approximately 150 m depth). High rain rates, onto the sea floor, of the organic matter that hosted the phosphate and several trace elements contributed to the accumulation of phosphorite, chert, and black shales and mudstones. Evaporation in the Goose Egg basin to the east of the Phosphoria basin ensured the import of surface seawater from the Phosphoria sea. Budgets of water, salt, phosphate, and oxygen, plus the minor accumulation of the biomarker gammacerane, show that exchange of water between the two basins was limited, possibly by the shallow carbonate platform that separated the two basins.

  15. Tectonic implications of U-Pb (zircon) Geochronology of Chor Granitoids of the Lesser Himalaya, Himachal Pradesh, NW Himalaya

    Science.gov (United States)

    Singh, P.; Bhakuni, S. S.

    2017-12-01

    Granitoids of various ages ranging from Proterozoic to Tertiary occur throughout the Himalayan fold-thrust belt. The occurrence of the Neoproterozoic granitoids are very less in the Himalayan orogen. One of the best example of Neoproterozoic granitoids is Chor granitoids, which are the intrusive granite bodies in the Paleoproterozoic of the Lesser Himalayan Crystallines of the Jutogh Group. In the central part these granites are non-foliated homogeneous that are porphyritic and peraluminous in nature (Singh et al., 2002; Bhargava et al., 2014, 2016), whereas in the peripheral part these are foliated showing south directed shear sense of movement. In this work we present the U-Pb (zircon) geochronology of two different granites samples of the Chor granitoids of Himachal Pradesh, NW Himalaya. The Jutogh Group of rocks is thrust over the Lesser Himalayan Sequence along the Jutogh Thrust or MCT. The geochronology of the Chor Granitoids and Lesser Himalayan Crystallines and their relationship with each other, including with the Indian shield are sparsely obscure. U-Pb zircon geochrnological age populations from these granitoids yield ages between 780 and 980 Ma. One sample gives the prominent age spectra for 206Pb/238U with weighted mean age of 908.3 ± 6.7 Ma (2σ) MSWD = 2.4 (n = 18). Similarly another sample gives the age of crystallization with weight mean age of 917 ± 17 Ma (2σ) MSWD = 3 (n = 11) and Th/U ratios of both samples are >0.1, indicating their magmatic origin. As a result of ductile shearing of granites along the MCT during the Cenozoic Himalayan Orogeny, the age has reduced to 780 Ma. The Neoproterozoic age of Chor granite matches with the Neoproterozoic detrital zircon age (800 to 1000 Ma by Parrish and Hodges 1996, Decelles et al., 2000) of the HHC. On the basis of U-Pb (zircon) geochronological ages, it is revealed that the source of zircons of the Chor granite and HHC rocks was the northern margin of the Pan-African orogen. The Chor granitoids was

  16. Harmful algal blooms (HABs), dissolved organic matter (DOM), and planktonic microbial community dynamics at a near-shore and a harbour station influenced by upwelling (SW Iberian Peninsula)

    Science.gov (United States)

    Loureiro, Sofia; Reñé, Albert; Garcés, Esther; Camp, Jordi; Vaqué, Dolors

    2011-05-01

    The surface microalgal community, including harmful species, dissolved organic matter (DOM), and bacterial and viral populations were studied during an annual cycle (November 2007-October 2008) in a Near-shore (NS) and a Harbour (H) station located in an upwelling area (Sagres, SW Iberian Peninsula). The higher water residence time, water stability and shallowness of harbours in comparison with open waters likely contributed to the differences found between stations regarding chemical variables, statistical correlations and harmful algal proliferations. Also, several differences were noticed from a previous assessment ( Loureiro et al., 2005) including higher SST, lower nitrate and chlorophyll a concentrations, along with a shift in the microplankton community structure from diatom to nanoflagellate predominance. These variations feasibly reflect the response of this dynamic system to regional environmental modifications contributing to the understanding of common patterns in environmental change trends. The division of the sampling period into (1) non-upwelling (Non-Uw), (2) "spin-up" of upwelling (SU-Uw), and (3) "spin-down" and relaxation-downwelling (SD-Rel) stages allowed the identification of natural groupings of microplankton samples by Multi Dimensional Scaling (MDS) analysis. Dissolved organic nitrogen (DON) and viruses were the most significant abiotic and biotic variables, respectively, contributing to the dissimilarities between these stages (SIMPER analysis) and, therefore, potentially affecting the microplankton community structure. Harmful algal species and a stable viral community appeared to be favoured by SD-Rel conditions. Data seem to indicate that both Gymnodinium catenatum and Heterosigma akashiwo, the most abundant potentially harmful species, have been imported into the sampling area. Also, the H location, together with potential retention sites developing around the Cabo de São Vicente upwelling centre, may contribute to the local

  17. Contribution of changes in opal productivity and nutrient distribution in the coastal upwelling systems to Late Pliocene/Early Pleistocene climate cooling

    Directory of Open Access Journals (Sweden)

    J. Etourneau

    2012-09-01

    Full Text Available The global Late Pliocene/Early Pleistocene cooling (~3.0–2.0 million years ago – Ma concurred with extremely high diatom and biogenic opal production in most of the major coastal upwelling regions. This phenomenon was particularly pronounced in the Benguela upwelling system (BUS, off Namibia, where it is known as the Matuyama Diatom Maximum (MDM. Our study focuses on a new diatom silicon isotope (δ30Si record covering the MDM in the BUS. Unexpectedly, the variations in δ30Si signal follow biogenic opal content, whereby the highest δ30Si values correspond to the highest biogenic opal content. We interpret the higher δ30Si values during the MDM as a result of a stronger degree of silicate utilisation in the surface waters caused by high productivity of mat-forming diatom species. This was most likely promoted by weak upwelling intensity dominating the BUS during the Late Pliocene/Early Pleistocene cooling combined with a large silicate supply derived from a strong Southern Ocean nutrient leakage responding to the expansion of Antarctic ice cover and the resulting stratification of the polar ocean 3.0–2.7 Ma ago. A similar scenario is hypothesized for other major coastal upwelling systems (e.g. off California during this time interval, suggesting that the efficiency of the biological carbon pump was probably sufficiently enhanced in these regions during the MDM to have significantly increased the transport of atmospheric CO2 to the deep ocean. In addition, the coeval extension of the area of surface water stratification in both the Southern Ocean and the North Pacific, which decreased CO2 release to the atmosphere, led to further enhanced atmospheric CO2 drawn-down and thus contributed significantly to Late Pliocene/Early Pleistocene cooling.

  18. Expression of the Middle-Late Miocene "Carbonate Crash" and "Biogenic Bloom" in the Benguela Current Upwelling Area of the South Atlantic Ocean

    Science.gov (United States)

    Diester-Haass, L.; Meyers, P. A.; Bauman, S. C.

    2001-05-01

    The middle-late Miocene "carbonate crash" - several episodes with significant drops in concentrations and accumulation rates of CaCO3 - occurred between 13 and 9 Ma in the equatorial Pacific and Indian Oceans and the Carribean Sea (Lyle et al., 1995; Roth et al., 2000). This event is followed by a "biogenic bloom" - a strong increase in biogenous production that has been described in the equatorial Pacific and Indian Oceans. In order to explain these two events, the questions of whether they are confined to tropical upwelling areas, whether they also occur in coastal upwelling areas, or whether they are global phenomena must be answered. We have explored the expression of these events during the evolution of the Benguela Current upwelling system. Sediment sequences from ODP Sites 1085 and 1087 record several drops in carbonate concentrations in the middle and early late Miocene that culminate in a major depression at 9.5-9.0 Ma and that are synchronous with the "carbonate crash" in the equatorial Pacific (Lyle et al., 1995). Climatic changes in SW Africa, reflected by an increase in delivery terrigenous sediment components and by a larger proportion of kaolinite, and oceanic changes, indicated by an expansion of the oxygen minimum zone, accompany this event. Oxygen depletion starts during early carbonate depressions and has a maximum during the major CaCO3 depression. Marine biological productivity, as reconstructed from concentrations of organic carbon and benthic foraminiferal accumulation rates, is at a minimum in the middle-early late Miocene. However, it increases 3-6 fold at 6.5 Ma, a shift that is synchronous with the "biogenic bloom" in the equatorial Pacific Ocean (Farrell et al., 1995). We attribute this important paleoceanographic change to a strengthening of latitudinal temperature gradients and corresponding vertical mixing by zonal winds during the onset of North Atlantic Deep Water flow, which led to more vigorous deep ventilation and emergence of

  19. African Peacekeepers in Africa

    DEFF Research Database (Denmark)

    Emmanuel, Nikolas G.

    2015-01-01

    peacekeeping operations in the region. It is important to add that the international community has frequently tried to facilitate the deployment of African armed forces with aid and training. From this reality, the following study goes beyond the current literature by focusing on the international factors......African states today are strongly encouraged by the United States (US) and other members of the international community to play a more central role in confronting crises on the continent. Indeed, in recent years African armed forces have increasingly served as the backbone supporting various...... behind African participation in United Nations (UN) peacekeeping operations in Africa. In doing so, this research focuses on US military aid and foreign troop training from 2002 to 2012, and its impact on African deployments into UN peacekeeping missions in Africa. As can be expected, such third...

  20. on the evolution of the kazaure schist belt of nw nigeria

    African Journals Online (AJOL)

    Admin

    2007-05-25

    May 25, 2007 ... the context of Pan-African deformation which led to the formation of a marginal back-arc basin floored by continental materials that ... occurrence of BIF, quartzites, conglomerates, and Pan-African granitoids in the belt; and emphasizes the presence ..... movements that affected the oxide facies during Pan-.