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Fluxes and distribution of dissolved iron in the eastern (sub-) tropical North Atlantic Ocean

Fluxes and distribution of dissolved iron in the eastern (sub-) tropical North Atlantic Ocean
Fluxes and distribution of dissolved iron in the eastern (sub-) tropical North Atlantic Ocean
Aeolian dust transport from the Saharan/Sahel desert regions is considered the dominant external input of iron (Fe) to the surface waters of the eastern (sub-) tropical North Atlantic Ocean. To test this hypothesis, we investigated the sources of dissolved Fe (DFe) and quantified DFe fluxes to the surface ocean in this region. In winter 2008, surface water DFe concentrations varied between <0.1 nM and 0.37 nM, with an average of 0.13 ± 0.07 nM DFe (n = 194). A strong correlation between mixed layer averaged concentrations of dissolved aluminum (DAl), a proxy for dust input, and DFe indicated dust as a source of DFe to the surface ocean. The importance of Aeolian nutrient input was further confirmed by an increase of 0.1 nM DFe and 0.05 ?M phosphate during a repeat transect before and after a dust event. An exponential decrease of DFe with increasing distance from the African continent, suggested that continental shelf waters were a source of DFe to the northern part of our study area. Relatively high Fe:C ratios of up to 3 × 10?5 (C derived from apparent oxygen utilization (AOU)) indicated an external source of Fe to these African continental shelf waters. Below the wind mixed layer along 12°N, enhanced DFe concentrations (>1.5 nM) correlated positively with apparent oxygen utilization (AOU) and showed the importance of organic matter remineralization as an DFe source. As a consequence, vertical diffusive mixing formed an important Fe flux to the surface ocean in this region, even surpassing that of a major dust event.
0886-6236
GB3004
Rijkenberg, Micha J.A.
549cc6d0-6f1a-432f-863a-2988abcb25d3
Steigenberger, Sebastian
15c989b8-dd0d-454c-b3cc-08d4290eaff0
Powell, Claire F.
20ca5807-abae-44f0-83cb-78d73e5ca6d5
van Haren, Hans
65d47a22-2732-4eb9-b1e0-1f7bc5d08f6b
Patey, Matthew D.
224dd2f8-b804-4839-b9d2-b5ace922bd87
Baker, Alex R.
3a011c8c-c15a-4080-9602-6f3628fdca4a
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Rijkenberg, Micha J.A.
549cc6d0-6f1a-432f-863a-2988abcb25d3
Steigenberger, Sebastian
15c989b8-dd0d-454c-b3cc-08d4290eaff0
Powell, Claire F.
20ca5807-abae-44f0-83cb-78d73e5ca6d5
van Haren, Hans
65d47a22-2732-4eb9-b1e0-1f7bc5d08f6b
Patey, Matthew D.
224dd2f8-b804-4839-b9d2-b5ace922bd87
Baker, Alex R.
3a011c8c-c15a-4080-9602-6f3628fdca4a
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9

Rijkenberg, Micha J.A., Steigenberger, Sebastian, Powell, Claire F., van Haren, Hans, Patey, Matthew D., Baker, Alex R. and Achterberg, Eric P. (2012) Fluxes and distribution of dissolved iron in the eastern (sub-) tropical North Atlantic Ocean. Global Biogeochemical Cycles, 26 (3), GB3004. (doi:10.1029/2011GB004264).

Record type: Article

Abstract

Aeolian dust transport from the Saharan/Sahel desert regions is considered the dominant external input of iron (Fe) to the surface waters of the eastern (sub-) tropical North Atlantic Ocean. To test this hypothesis, we investigated the sources of dissolved Fe (DFe) and quantified DFe fluxes to the surface ocean in this region. In winter 2008, surface water DFe concentrations varied between <0.1 nM and 0.37 nM, with an average of 0.13 ± 0.07 nM DFe (n = 194). A strong correlation between mixed layer averaged concentrations of dissolved aluminum (DAl), a proxy for dust input, and DFe indicated dust as a source of DFe to the surface ocean. The importance of Aeolian nutrient input was further confirmed by an increase of 0.1 nM DFe and 0.05 ?M phosphate during a repeat transect before and after a dust event. An exponential decrease of DFe with increasing distance from the African continent, suggested that continental shelf waters were a source of DFe to the northern part of our study area. Relatively high Fe:C ratios of up to 3 × 10?5 (C derived from apparent oxygen utilization (AOU)) indicated an external source of Fe to these African continental shelf waters. Below the wind mixed layer along 12°N, enhanced DFe concentrations (>1.5 nM) correlated positively with apparent oxygen utilization (AOU) and showed the importance of organic matter remineralization as an DFe source. As a consequence, vertical diffusive mixing formed an important Fe flux to the surface ocean in this region, even surpassing that of a major dust event.

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Published date: 2012
Organisations: Ocean and Earth Science

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Local EPrints ID: 342337
URI: http://eprints.soton.ac.uk/id/eprint/342337
ISSN: 0886-6236
PURE UUID: c35a6c1d-2b42-46fb-a114-331f6870c0d5

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Date deposited: 22 Aug 2012 16:17
Last modified: 08 Jan 2022 17:54

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Contributors

Author: Micha J.A. Rijkenberg
Author: Sebastian Steigenberger
Author: Claire F. Powell
Author: Hans van Haren
Author: Matthew D. Patey
Author: Alex R. Baker

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