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Sedimentary and atmospheric sources of iron around South Georgia, Southern Ocean: a modelling perspective

Sedimentary and atmospheric sources of iron around South Georgia, Southern Ocean: a modelling perspective
Sedimentary and atmospheric sources of iron around South Georgia, Southern Ocean: a modelling perspective
In high-nutrient low-chlorophyll waters of the western Atlantic sector of the Southern Ocean, an intense phytoplankton bloom is observed annually north of South Georgia. Multiple sources, including shallow sediments and atmospheric dust deposition, are thought to introduce iron to the region. However, the relative importance of each source is still unclear, owing in part to the scarcity of dissolved iron (dFe) measurements in the South Georgia region. In this study, we combine results from a recently published dFe data set around South Georgia with a coupled regional hydrodynamic and biogeochemical model to further investigate iron supply around the island. The biogeochemical component of the model includes an iron cycle, where sediments and dust deposition are the sources of iron to the ocean. The model captures the characteristic flow patterns around South Georgia, hence simulating a large phytoplankton bloom to the north (i.e. downstream) of the island. Modelled dFe concentrations agree well with observations (mean difference and root mean square errors of ~0.02 nM and ~0.81 nM) and form a large plume to the north of the island that extends eastwards for more than 800 km. In agreement with observations, highest dFe concentrations are located along the coast and decrease with distance from the island. Sensitivity tests indicate that most of the iron measured in the main bloom area originates from the coast and very shallow shelf-sediments (depths < 20 m). Dust deposition exerts almost no effect on surface chlorophyll a concentrations. Other sources of iron such as run-off and glacial melt are not represented explicitly in the model, however we discuss their role in the local iron budget.
1726-4170
1981-2001
Borrione, I.
948c5a11-4cb4-4b4c-9b7c-1ddeed07d243
Aumont, O.
f51d877d-8bb8-4a89-96b0-0eeeda8ea00c
Nielsdóttir, M.C.
a2f4e879-340c-4e2a-985e-ac1112448164
Schlitzer, R.
4e0eec4d-219b-4574-a343-d3879aaa7e5a
Borrione, I.
948c5a11-4cb4-4b4c-9b7c-1ddeed07d243
Aumont, O.
f51d877d-8bb8-4a89-96b0-0eeeda8ea00c
Nielsdóttir, M.C.
a2f4e879-340c-4e2a-985e-ac1112448164
Schlitzer, R.
4e0eec4d-219b-4574-a343-d3879aaa7e5a

Borrione, I., Aumont, O., Nielsdóttir, M.C. and Schlitzer, R. (2014) Sedimentary and atmospheric sources of iron around South Georgia, Southern Ocean: a modelling perspective. Biogeosciences, 11 (7), 1981-2001. (doi:10.5194/bg-11-1981-2014).

Record type: Article

Abstract

In high-nutrient low-chlorophyll waters of the western Atlantic sector of the Southern Ocean, an intense phytoplankton bloom is observed annually north of South Georgia. Multiple sources, including shallow sediments and atmospheric dust deposition, are thought to introduce iron to the region. However, the relative importance of each source is still unclear, owing in part to the scarcity of dissolved iron (dFe) measurements in the South Georgia region. In this study, we combine results from a recently published dFe data set around South Georgia with a coupled regional hydrodynamic and biogeochemical model to further investigate iron supply around the island. The biogeochemical component of the model includes an iron cycle, where sediments and dust deposition are the sources of iron to the ocean. The model captures the characteristic flow patterns around South Georgia, hence simulating a large phytoplankton bloom to the north (i.e. downstream) of the island. Modelled dFe concentrations agree well with observations (mean difference and root mean square errors of ~0.02 nM and ~0.81 nM) and form a large plume to the north of the island that extends eastwards for more than 800 km. In agreement with observations, highest dFe concentrations are located along the coast and decrease with distance from the island. Sensitivity tests indicate that most of the iron measured in the main bloom area originates from the coast and very shallow shelf-sediments (depths < 20 m). Dust deposition exerts almost no effect on surface chlorophyll a concentrations. Other sources of iron such as run-off and glacial melt are not represented explicitly in the model, however we discuss their role in the local iron budget.

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More information

Published date: 9 April 2014
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 364229
URI: http://eprints.soton.ac.uk/id/eprint/364229
ISSN: 1726-4170
PURE UUID: c54c9ba7-975c-44b8-9d36-772c51367461

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Date deposited: 10 Apr 2014 08:53
Last modified: 16 Jul 2019 21:07

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