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Labile Fe(II) concentrations in the Atlantic sector of the Southern Ocean along a transect from the subtropical domain to the Weddell Sea Gyre

Labile Fe(II) concentrations in the Atlantic sector of the Southern Ocean along a transect from the subtropical domain to the Weddell Sea Gyre
Labile Fe(II) concentrations in the Atlantic sector of the Southern Ocean along a transect from the subtropical domain to the Weddell Sea Gyre
Labile Fe(II) distributions were investigated in the Sub-Tropical South Atlantic and the Southern Ocean during the BONUS-GoodHope cruise from 34 to 57° S (February–March 2008). Concentrations ranged from below the detection limit (0.009 nM) to values as high as 0.125 nM. In the surface mixed layer, labile Fe(II) concentrations were always higher than the detection limit, with values higher than 0.060 nM south of 47° S, representing between 39 % and 63 % of dissolved Fe (DFe). Apparent biological production of Fe(II) was evidenced. At intermediate depth, local maxima were observed, with the highest values in the Sub-Tropical domain at around 200 m, and represented more than 70 % of DFe. Remineralization processes were likely responsible for those sub-surface maxima. Below 1500 m, concentrations were close to or below the detection limit, except at two stations (at the vicinity of the Agulhas ridge and in the north of the Weddell Sea Gyre) where values remained as high as ~0.030–0.050 nM. Hydrothermal or sediment inputs may provide Fe(II) to these deep waters. Fe(II) half life times (t1/2) at 4°C were measured in the upper and deep waters and ranged from 2.9 to 11.3 min, and from 10.0 to 72.3 min, respectively. Measured values compared quite well in the upper waters with theoretical values from two published models, but not in the deep waters. This may be due to the lack of knowledge for some parameters in the models and/or to organic complexation of Fe(II) that impact its oxidation rates. This study helped to considerably increase the Fe(II) data set in the Ocean and to better understand the Fe redox cycle.
1726-4170
2461-2479
Sarthou, G.
06d8eba4-f933-4093-a5f3-4e4c8bf602ef
Bucciarelli, E.
383299ea-e76a-41ef-acde-c0f1455ffb94
Chever, F.
e18315d9-5296-4df4-857c-f4807fbc6a52
Hansard, S.P.
78358401-0d07-489c-b521-1b141550ccf6
González-Dávila, M.
aadadcbd-8b3e-43e2-9eb8-94bf7685b157
Santana-Casiano, J.M.
c26a7ff2-e4d5-45ca-b1f0-7afda8cebb7d
Planchon, F.
ed3af88f-439a-498c-9af7-7ea3e3e609e2
Speich, S.
6eae319c-8f65-4cd3-9e28-618c7a342404
Sarthou, G.
06d8eba4-f933-4093-a5f3-4e4c8bf602ef
Bucciarelli, E.
383299ea-e76a-41ef-acde-c0f1455ffb94
Chever, F.
e18315d9-5296-4df4-857c-f4807fbc6a52
Hansard, S.P.
78358401-0d07-489c-b521-1b141550ccf6
González-Dávila, M.
aadadcbd-8b3e-43e2-9eb8-94bf7685b157
Santana-Casiano, J.M.
c26a7ff2-e4d5-45ca-b1f0-7afda8cebb7d
Planchon, F.
ed3af88f-439a-498c-9af7-7ea3e3e609e2
Speich, S.
6eae319c-8f65-4cd3-9e28-618c7a342404

Sarthou, G., Bucciarelli, E., Chever, F., Hansard, S.P., González-Dávila, M., Santana-Casiano, J.M., Planchon, F. and Speich, S. (2011) Labile Fe(II) concentrations in the Atlantic sector of the Southern Ocean along a transect from the subtropical domain to the Weddell Sea Gyre. Biogeosciences, 8 (9), 2461-2479. (doi:10.5194/bg-8-2461-2011).

Record type: Article

Abstract

Labile Fe(II) distributions were investigated in the Sub-Tropical South Atlantic and the Southern Ocean during the BONUS-GoodHope cruise from 34 to 57° S (February–March 2008). Concentrations ranged from below the detection limit (0.009 nM) to values as high as 0.125 nM. In the surface mixed layer, labile Fe(II) concentrations were always higher than the detection limit, with values higher than 0.060 nM south of 47° S, representing between 39 % and 63 % of dissolved Fe (DFe). Apparent biological production of Fe(II) was evidenced. At intermediate depth, local maxima were observed, with the highest values in the Sub-Tropical domain at around 200 m, and represented more than 70 % of DFe. Remineralization processes were likely responsible for those sub-surface maxima. Below 1500 m, concentrations were close to or below the detection limit, except at two stations (at the vicinity of the Agulhas ridge and in the north of the Weddell Sea Gyre) where values remained as high as ~0.030–0.050 nM. Hydrothermal or sediment inputs may provide Fe(II) to these deep waters. Fe(II) half life times (t1/2) at 4°C were measured in the upper and deep waters and ranged from 2.9 to 11.3 min, and from 10.0 to 72.3 min, respectively. Measured values compared quite well in the upper waters with theoretical values from two published models, but not in the deep waters. This may be due to the lack of knowledge for some parameters in the models and/or to organic complexation of Fe(II) that impact its oxidation rates. This study helped to considerably increase the Fe(II) data set in the Ocean and to better understand the Fe redox cycle.

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Published date: 6 September 2011
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 364772
URI: https://eprints.soton.ac.uk/id/eprint/364772
ISSN: 1726-4170
PURE UUID: 64c80ff3-2144-4e8b-93b1-e3c0a34d5b87

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Date deposited: 09 May 2014 09:57
Last modified: 03 Dec 2018 17:33

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