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  • 1
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    Physical oceanography, inorganic nutrients, dissolved and particulate organic carbon and nitrogen during FLUXES-1 cruise to the Cape Verde Frontal Zone in 2017 (2022)
    PANGAEA
    Details
    Publication Date: 2024-03-22
    Description: The Cape Verde Frontal Zone (CVFZ) is a highly dynamic region located in the southern boundary of the Canary Current Eastern Boundary Upwelling Ecosystem. Due to the interaction of the Cape Verde Front with the Mauritanian coastal upwelling, the area features large vertical and horizontal export fluxes of organic matter. Full-depth profiles were recorded during FLUXES I cruise, with four consecutive transects defining a box embracing the giant filament of Cape Blanc and the Cape Verde front. Fifteen levels were sampled in medium and long stations (down to 4000 dbar) and 10 levels in short stations (down to 2000 dbar) where inorganic nutrients (NO3, NO2, Si(OH)4 and PO4), dissolved organic carbon/total dissolved nitrogen (DOC/TDN), and suspended particulate organic carbon and nitrogen (POC and PON) were sampled. Micromolar concentrations of nutrient salts were determined simultaneously by segmented flow analysis in an Alliance Futura autoanalyser. The determination of suspended POC and PON was carried out by high temperature catalytic oxidation at 900 °C in a Perkin Elmer 2400 elemental analyser. DOC and TDN were analysed by high temperature catalytic oxidation at 680 °C with a Shimadzu TOC-V analyser connected in line with a TNM1 measuring unit. Alongside with water samples conductivity, temperature and depth (CTD; SeaBird SBE911 plus), and dissolved oxygen (SeaBird SBE43), fluorescence of chlorophyll (SeaPoint SCF), and turbidity (SeaPoint STM) were measured. CTD conductivity was calibrated with water samples taken from the rosette and analysed on board with a Guildline 8410-A Portasal salinometer. Samples for dissolved oxygen (O2) determination were analysed on board by the Winkler potentiometric method. The chlorophyll (Chl) fluorescence sensor was calibrated with water samples taken at 4 depths in the photic layer which were estimated fluorometrically by means of a Turner Designs bench fluorometer 10-AU.
    Keywords: 29SG20170711; 29SG20170711_10-1; 29SG20170711_1-1; 29SG20170711_11-1; 29SG20170711_12-1; 29SG20170711_13-1; 29SG20170711_14-1; 29SG20170711_15-1; 29SG20170711_16-1; 29SG20170711_17-1; 29SG20170711_18-1; 29SG20170711_19-1; 29SG20170711_20-1; 29SG20170711_2-1; 29SG20170711_21-1; 29SG20170711_22-1; 29SG20170711_23-1; 29SG20170711_24-1; 29SG20170711_25-1; 29SG20170711_26-1; 29SG20170711_27-1; 29SG20170711_28-1; 29SG20170711_29-1; 29SG20170711_30-1; 29SG20170711_3-1; 29SG20170711_31-1; 29SG20170711_32-1; 29SG20170711_33-1; 29SG20170711_34-1; 29SG20170711_35-1; 29SG20170711_4-1; 29SG20170711_5-1; 29SG20170711_6-1; 29SG20170711_7-1; 29SG20170711_8-1; 29SG20170711_9-1; Biogeochemical impact of mesoscale and sub-mesoscale processes along the life history of cyclonic and anticyclonic eddies: plankton variability and productivity; Bottle number; Campaign; Cape Verde Frontal Zone; Carbon, organic, dissolved; Carbon, organic, particulate; Carbon cycling; Cast number; Chlorophyll fluorometer, Seapoint, Seapoint chlorophyll fluorometer; Constraining organic carbon fluxes in an eastern boundary upwelling ecosystem (NW Africa): the role of non-sinking carbon in the context of the biological pump; Cruise/expedition; CTD, Sea-Bird, SBE43; CTD, Sea-Bird SBE 911plus; CTD/Rosette; CTD-RO; DATE/TIME; DEPTH, water; Dissolved Organic Matter; e-IMPACT; Elemental analyzer, Perkin Elmer, 2400; Event label; Fluorescence, chlorophyll; FLUXES; FLUXES I; LATITUDE; LONGITUDE; Nitrate; Nitrite; Nitrogen, organic, particulate; Nitrogen, total dissolved; nitrogen cycling; Oxygen; particulate organic matter; Phosphate; Pressure, water; Quality flag, carbon, organic, dissolved; Quality flag, carbon, organic, particulate; Quality flag, fluorescence, chlorophyll; Quality flag, nitrate; Quality flag, nitrite; Quality flag, nitrogen, organic, particulate; Quality flag, nitrogen, total dissolved; Quality flag, oxygen; Quality flag, phosphate; Quality flag, salinity; Quality flag, silicic acid; Salinity; Sarmiento de Gamboa; Segmented flow analyzer (Alliance Futura); Shimadzu TOC-V CSH total organic carbon analyzer coupled to TNM-1 nitrogen analyzer; Silicic acid; Station label; SUMMER; Sustainable Management of Mesopelagic Resources; Temperature, water; water masses; Winkler potentiometric after Langdon (2010)
    Type: Dataset
    Format: text/tab-separated-values, 12905 data points
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    DATA PANGAEA
  • 2
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    Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre (2012)
    Copernicus Publications on behalf of the European Geosciences Union
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 9 (2012): 2831-2846, doi:10.5194/bg-9-2831-2012.
    Description: We used 5-yr concomitant data of tracer distribution from the BATS (Bermuda Time-series Study) and ESTOC (European Station for Time-Series in the Ocean, Canary Islands) sites to build a 1-D tracer model conservation including horizontal advection, and then compute net production and shallow remineralization rates for both sites. Our main goal was to verify if differences in these rates are consistent with the lower export rates of particulate organic carbon observed at ESTOC. Net production rates computed below the mixed layer to 110 m from April to December for oxygen, dissolved inorganic carbon and nitrate at BATS (1.34±0.79 mol O2 m−2, −1.73±0.52 mol C m−2 and −125±36 mmol N m−2) were slightly higher for oxygen and carbon compared to ESTOC (1.03±0.62 mol O2 m−2, −1.42±0.30 mol C m−2 and −213±56 mmol N m−2), although the differences were not statistically significant. Shallow remineralization rates between 110 and 250 m computed at ESTOC (−3.9±1.0 mol O2 m−2, 1.53±0.43 mol C m−2 and 38±155 mmol N m−2) were statistically higher for oxygen compared to BATS (−1.81±0.37 mol O2 m−2, 1.52±0.30 mol C m−2 and 147±43 mmol N m−2). The lateral advective flux divergence of tracers, which was more significant at ESTOC, was responsible for the differences in estimated oxygen remineralization rates between both stations. According to these results, the differences in net production and shallow remineralization cannot fully explain the differences in the flux of sinking organic matter observed between both stations, suggesting an additional consumption of non-sinking organic matter at ESTOC.
    Description: B. Mourino was supported by the Ramon y Cajal program from the Spanish Minister of Science and Technology. Funding for this study was provided by the Xunta de Galicia under the research project VARITROP (09MDS001312PR, PI B. Mourino) and by the Ministerio de Ciencia e Innovation MOMAC project (CTM2008-05914/MAR).
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
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    Lagrangian pathways for sub-Antarctic Mode Water formation and carbon uptake​ (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-06-23
    Description: Sub-Antarctic Mode Waters (SAMW), forming in the deep winter mixed layers in the Sub-Antarctic Zone (SAZ) to the north of the Antarctic Circumpolar Current (ACC), connect the ocean thermocline with the atmosphere, contributing to ocean carbon and heat uptake and transporting high-latitude nutrients northward, to fuel primary production at low latitudes. The important climatic role of SAMW is controlled by the rate of fluid subduction from the deep winter mixed layers and the concentration of heat, carbon and nutrients at the end of winter. These concentrations depend on a range of processes, both physical (air-sea exchange, transport of Antarctic waters across the ACC, along ACC advection, eddy fluxes, diapycnal mixing, etc.) and biogeochemical (biological uptake, export and remineralisation), whose relative contributions are very poorly understood. With a Lagrangian particle-tracking experiment in a data-assimilative coupled physico-biogeochemical model of the Southern Ocean (B-SOSE), we assess the origin of the water masses reaching SAMW formation regions and the physico- and biogeochemical transformations occurring along their transport pathways. Our results underline the importance of the advection of subtropical waters along the ACC for the sequestration of heat and anthropogenic carbon and in modulating the fertilization of the low-latitude thermocline.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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    GFZ OAI
  • 4
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    The role of mesoscale eddy stirring and microscale turbulence in supplying nutrients to phytoplankton in the North Atlantic subtropical gyre (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-05-04
    Description: Sustaining phytoplankton primary production requires the physical supply of nutrients to the thermocline and the mixed layer. In the extensive downwelling regions of the subtropical gyres, the pathways of this nutrient supply remain unclear. Global estimates of mesoscale eddy mixing and internal-wave driven diapycnal mixing and climatological nitrate, salinity, and temperature data are combined to explore the relative importance of microscale turbulence and eddy stirring in supplying nutrients to phytoplankton in the North Atlantic subtropical gyre. The nutrient fluxes by eddy stirring and microscale turbulence are estimated in terms of their advective and diffusive transfers associated with the evolution of a nutrient. Mesoscale eddy stirring and microscale turbulence together supply an average of 0.10 mol N m〈sup〉-2〈/sup〉 yr〈sup〉-1〈/sup〉 to the mixed layer over the gyre. There is substantial spatial variation in the relative importance of the eddy- and turbulence-driven supplies across the gyre, where eddy stirring dominates over microscale turbulence in the northern and south-western gyre and vice versa in the south-eastern gyre. Given the combined nitrate supply by eddy stirring and microscale turbulence to the mixed layer falls short of nitrate export over 90% of the gyre, we suggest that mesoscale eddy stirring and microscale turbulence does not sustain phytoplankton primary production in the subtropical gyres alone. Other mixing mechanisms such as time-varying eddy circulations and double diffusion by salt fingers are expected to be important.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 5
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    Mechanism of rapid along-boundary upwelling in a continental-slope canyon (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-11
    Description: Recent theoretical studies〈sup〉 〈/sup〉have hypothesized that deep-ocean upwelling may be primarily sustained by mixing processes within a thin bottom boundary layer (BBL) adjacent to the seafloor. However, this proposition appears at odds with several decades of observations of ocean turbulence, which suggest a pervasive intensification of mixing with depth conducive to deep-ocean downwelling. Here, we reconcile such intensification with the newly-proposed paradigm of BBL-focussed upwelling in the context of a typical continental-slope canyon, in which very rapid upwelling is observed. We show that upwelling along the canyon stems from episodic cells of convective turbulent mixing up to 250 m in height, generated by tidal currents sweeping up- and down-canyon. As drag against the seabed decelerates the currents’ base, their upper layers convey dense waters over slower-flowing lighter waters below, causing the dense waters to convectively mix, lighten and upwell. We discuss how this upwelling mechanism is likely to be of wider representativeness, lending support to the view that deep-ocean upwelling may predominantly occur along the ocean’s sloping boundaries.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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    GFZ OAI
  • 6
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    The influence of nitrogen inputs on biomass and trophic structure of ocean plankton: a study using biomass and stable isotope size-spectra (2016)
    Oxford University Press
    Details
    Publication Date: 2016-10-08
    Description: Large scale patterns in planktonic food web structure were studied by applying continuous size-scaled models of biomass and 15 N to plankton samples, collected at 145 stations during the Malaspina-2010 Expedition across three ocean basins and including major biomes. Carbon biomass and 15 N were determined in size-fractionated samples (40 to 5000 μm) collected by vertical hauls (0–200 m). Biomass-normalized size-spectra were constructed to summarize food web structure and spatial patterns in spectral parameters were analyzed using geographically-weighted regression analysis. Except in the northwestern Atlantic, size-spectra showed low variability, reflecting a homogeneity in nitrogen sources and food web structure for the central oceans. Estimated predator-to-prey mass ratios 〈104 and mean trophic transfer efficiency values between 16% (coastal biome) and 〉20% (Trades and Westerlies biomes) suggested that oceanic plankton food webs may support a larger number of trophic levels than current estimates based on high efficiency values. The largest changes in spectral parameters and nitrogen sources were related to inputs of atmospheric nitrogen, either from diazotrophic organisms or dust deposition. These results suggest geographic homogeneity in the net transfer of nitrogen up the food web.
    Print ISSN: 0142-7873
    Electronic ISSN: 1464-3774
    Topics: Biology
    Published by Oxford University Press
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  • 7
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    Optimality-based Trichodesmium diazotrophy in the North Atlantic subtropical gyre (2016)
    Oxford Univ. Press
    Details
    Publication Date: 2023-08-01
    Description: A recent optimality-based model for phytoplankton growth and diazotrophy was applied at two stations located in the oligotrophic western and the ultra-oligotrophic eastern subtropical North Atlantic. Contrary to the common view that diazotrophy is favoured by nitrogen (N) depletion relative to the Redfield equivalent of phosphorus (P), we find that optimality-based diazotrophy could explain N fixation in both regions in spite of relatively high N:P supply ratios. This is possible because the availability of an additional source of N for diazotrophs makes them strong competitors for P under oligotrophic conditions. The best reproduction of observations, especially of net primary production, is only achieved with preferential remineralization of P relative to N and atmospheric deposition. In line with observations, a higher rate of nitrogen fixation is predicted for the eastern site, owing to a larger niche for diazotrophs resulting from stronger oligotrophy and lower N:P supply ratios due to weaker atmospheric N deposition. Because the competitive advantage of diazotrophs under nutrient starvation diminishes with increasing supply N:P ratio, the predicted increase of atmospheric N deposition due to anthropogenic activity could negatively affect N2 fixation in the Atlantic Ocean.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Optimality-based Trichodesmium diazotrophy in the North Atlantic subtropical gyre (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-20
    Description: A recent optimality-based model for phytoplankton growth and diazotrophy was applied at two stations located in the oligotrophic western and the ultra-oligotrophic eastern subtropical North Atlantic. Contrary to the common view that diazotrophy is favoured by nitrogen (N) depletion relative to the Redfield equivalent of phosphorus (P), we find that optimality-based diazotrophy could explain N fixation in both regions in spite of relatively high N:P supply ratios. This is possible because the availability of an additional source of N for diazotrophs makes them strong competitors for P under oligotrophic conditions. The best reproduction of observations, especially of net primary production, is only achieved with preferential remineralization of P relative to N and atmospheric deposition. In line with observations, a higher rate of nitrogen fixation is predicted for the eastern site, owing to a larger niche for diazotrophs resulting from stronger oligotrophy and lower N:P supply ratios due to weaker atmospheric N deposition. Because the competitive advantage of diazotrophs under nutrient starvation diminishes with increasing supply N:P ratio, the predicted increase of atmospheric N deposition due to anthropogenic activity could negatively affect N 2 fixation in the Atlantic Ocean.
    Print ISSN: 0142-7873
    Electronic ISSN: 1464-3774
    Topics: Biology
    Published by Oxford University Press
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  • 9
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    Importance of salt fingering for new nitrogen supply in the oligotrophic ocean (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-09-11
    Description: Article The relative contribution of nitrogen fixation and nitrogen diffusion to marine biomes is presently debated. Here, the authors evaluate the contribution of these pathways across the tropics and subtropics of the global ocean and show that nitrogen diffusion, reinforced by salt fingers, is the dominant process. Nature Communications doi: 10.1038/ncomms9002 Authors: B. Fernández-Castro, B. Mouriño-Carballido, E. Marañón, P. Chouciño, J. Gago, T. Ramírez, M. Vidal, A. Bode, D. Blasco, S.-J. Royer, M. Estrada, R. Simó
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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