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Turbulent nutrient fluxes in the Iceland Basin

Turbulent nutrient fluxes in the Iceland Basin
Turbulent nutrient fluxes in the Iceland Basin
As part of a multidisciplinary cruise to the Iceland Basin in July–August 2007, near to the historical JGOFS Ocean Weather Station India site (?59° N, ?19° W), observations were made of vertical turbulent nutrient fluxes around an eddy dipole, a strong mesoscale feature consisting of a cyclonic eddy and an anti-cyclonically rotating mode-water eddy. Investigation of the spatial distribution of vertical turbulent diffusivity around the dipole shows an almost uniform horizontal distribution despite the strong horizontal gradients in water velocity and density observed. An area mean turbulent diffusivity was calculated as 0.21 (95% confidence interval: 0.17–0.26)×10?4 m2 s?1 at the base of the euphotic zone. The vertical turbulent fluxes of three major macro-nutrients into the euphotic zone were calculated as 0.13 (95% confidence interval 0.08–0.22) mmol m?2 day?1 for nitrate, 0.08 (0.05–0.12) mmol m?2 day?1 for silicate and, 8.6 (13.0–5.2 )×10?3 mmol m?2 day?1 for phosphate. The vertical turbulent flux of dissolved iron (dFe) into the euphotic zone was calculated to be 2.6 (95% confidence interval 1.3–4.3)×10?6 mmol m2 day?1. Turbulent macro-nutrient flux is estimated to contribute up to 14% of the deep winter mixing supply of silicate, nitrate and phosphate in the region. The magnitude of turbulent dFe flux is estimated to be at most 8% of the deep winter mixing supply of dFe. Deep winter mixing is hypothesised to supply an adequate amount of iron to fully utilise the deep winter mixed supply of silicate but not the deep winter mixed supply of nitrate. This suggests that while the iron supply may not limit the magnitude of the spring bloom, iron limitation may be occurring post bloom.
Nitrate, Silicate, Phosphate, Dissolved iron, Turbulent diffusion, North Atlantic
0967-0637
20-35
Forryan, A.
4e753ae9-7f12-495f-933a-2c5a1f554a0e
Martin, A.P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Srokosz, M.A.
1e0442ce-679f-43f2-8fe4-9a0f0174d483
Popova, E.E.
3ea572bd-f37d-4777-894b-b0d86f735820
Painter, S.C.
29e32f35-4ee8-4654-b305-4dbe5a312295
Stinchcombe, M.C.
433dd398-15f7-4730-9f1e-992d65bec70b
Forryan, A.
4e753ae9-7f12-495f-933a-2c5a1f554a0e
Martin, A.P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Srokosz, M.A.
1e0442ce-679f-43f2-8fe4-9a0f0174d483
Popova, E.E.
3ea572bd-f37d-4777-894b-b0d86f735820
Painter, S.C.
29e32f35-4ee8-4654-b305-4dbe5a312295
Stinchcombe, M.C.
433dd398-15f7-4730-9f1e-992d65bec70b

Forryan, A., Martin, A.P., Srokosz, M.A., Popova, E.E., Painter, S.C. and Stinchcombe, M.C. (2012) Turbulent nutrient fluxes in the Iceland Basin. Deep Sea Research Part I: Oceanographic Research Papers, 63, 20-35. (doi:10.1016/j.dsr.2011.12.006).

Record type: Article

Abstract

As part of a multidisciplinary cruise to the Iceland Basin in July–August 2007, near to the historical JGOFS Ocean Weather Station India site (?59° N, ?19° W), observations were made of vertical turbulent nutrient fluxes around an eddy dipole, a strong mesoscale feature consisting of a cyclonic eddy and an anti-cyclonically rotating mode-water eddy. Investigation of the spatial distribution of vertical turbulent diffusivity around the dipole shows an almost uniform horizontal distribution despite the strong horizontal gradients in water velocity and density observed. An area mean turbulent diffusivity was calculated as 0.21 (95% confidence interval: 0.17–0.26)×10?4 m2 s?1 at the base of the euphotic zone. The vertical turbulent fluxes of three major macro-nutrients into the euphotic zone were calculated as 0.13 (95% confidence interval 0.08–0.22) mmol m?2 day?1 for nitrate, 0.08 (0.05–0.12) mmol m?2 day?1 for silicate and, 8.6 (13.0–5.2 )×10?3 mmol m?2 day?1 for phosphate. The vertical turbulent flux of dissolved iron (dFe) into the euphotic zone was calculated to be 2.6 (95% confidence interval 1.3–4.3)×10?6 mmol m2 day?1. Turbulent macro-nutrient flux is estimated to contribute up to 14% of the deep winter mixing supply of silicate, nitrate and phosphate in the region. The magnitude of turbulent dFe flux is estimated to be at most 8% of the deep winter mixing supply of dFe. Deep winter mixing is hypothesised to supply an adequate amount of iron to fully utilise the deep winter mixed supply of silicate but not the deep winter mixed supply of nitrate. This suggests that while the iron supply may not limit the magnitude of the spring bloom, iron limitation may be occurring post bloom.

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More information

Published date: 2012
Keywords: Nitrate, Silicate, Phosphate, Dissolved iron, Turbulent diffusion, North Atlantic
Organisations: Marine Systems Modelling, Marine Biogeochemistry, Physical Oceanography, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 338078
URI: http://eprints.soton.ac.uk/id/eprint/338078
ISSN: 0967-0637
PURE UUID: 39563ae2-87de-4249-924e-e7c7ecc09b98

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Date deposited: 08 May 2012 16:03
Last modified: 14 Mar 2024 11:01

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Contributors

Author: A. Forryan
Author: A.P. Martin
Author: M.A. Srokosz
Author: E.E. Popova
Author: S.C. Painter
Author: M.C. Stinchcombe

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