Concentrations of organic carbon, nitrogen and phosphorus on vertical profiles in waters of the tropical North Atlantic in March 2002, supplement to: Dietze, Heiner; Oschlies, Andreas; Kähler, Paul (2004): Internal-wave-induced and double-diffusive nutrient fluxes to the nutrient-consuming surface layer in the oligotrophic subtropical North Atlantic. Ocean Dynamics, 54(1), 1-7


In the literature, an inconsistency exists between estimates of biotically-effected carbon export inferred from large-scale geochemical studies (Jenkins 1982; 47 gC m–2 a–1) and local measurements of turbulent nutrient supply (Lewis et al. 1986; 4 gC m–2 a–1) in the eastern subtropical North Atlantic. Nutrient supply to the upper ocean by turbulent mixing is reexamined using local standard oceanographic measurements and high-resolution vertical profiles of nutrients averaged over a large region directly comparable to that investigated by Jenkins (1982).Turbulent fluxes induced by internal waves and salt fingering, respectively, are separated according to Gregg (1989) and Zhang et al. (1998). Nutrient transport into the nutrient-consuming surface layer by salt fingering is more than fivefold higher than transport due to internal-wave induced turbulence. Still, this cannot resolve the above- mentioned apparent inconsistency, even if additional physical transport mechanisms such as eddy pumping, advection and horizontal diffusion are accounted for. Estimated nitrate fluxes due to vertical turbulent diffusion are 0.05–0.15 mol m-2 a-1, corresponding to 4–11 gC m-2 a-1. Observed NO3/PO4 turbulent flux ratios of up to 23 are interpreted as the imprint of N2 fixation.

Not filtered water samples were taken in 10 ml ampoules (sealed immediately after being acidified with phosphoric acid to pH<2, sampling), or 40 ml screw-lid vials, and measured onboard at sampling or next days, or frozen (-20°C) until being acidified and measured in home labs.Carbon measurement was by high-temperature catalytic oxydation in a 10 cm column packed with 5% Pt on aluminum oxide beads at 900°C in a stream of oxygen, and CO2 detection by infrared extinction after the removal of moisture and SO2 by appropriate traps (cold trap, Mg-percarbonate, Na-pyrophosphate, tin, bronze or Sulfix). The apparatus was the dual channel Dimatek 2000 equipped with a Binos 200 detector.Nitrogen was measured by chemoluminescence detection of NO2 in the combustion gases after leaving the Binos detector in one of the two channels of the setup. Most measurements of samples containing high nitrate were discarded, when data were inconsistent. The nature of nitrate interference is not clear.

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Metadata Access
Creator Dietze, Heiner; Oschlies, Andreas; Kähler, Paul
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2008
Rights Creative Commons Attribution 3.0 Unported
OpenAccess true
Language English
Resource Type Supplementary Collection of Datasets
Format application/zip
Size 10 datasets
Discipline Earth System Research
Spatial Coverage (-30.033W, 18.002S, -29.995E, 31.547N); North Atlantic
Temporal Coverage Begin 2002-03-14T04:00:00Z
Temporal Coverage End 2002-03-20T04:00:00Z