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Glacial and hydrothermal sources of dissolved iron(II) in Southern Ocean waters surrounding Heard and McDonald Islands

Citation

Holmes, TM and Wuttig, K and Chase, Z and Schallenberg, C and van der Merwe, P and Townsend, AT and Bowie, AR, Glacial and hydrothermal sources of dissolved iron(II) in Southern Ocean waters surrounding Heard and McDonald Islands, Journal of Geophysical Research: Oceans, 125, (10) Article e2020JC016286. ISSN 2169-9291 (2020) [Refereed Article]


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2020. American Geophysical Union. All Rights Reserved.

DOI: doi:10.1029/2020JC016286

Abstract

The Southern Ocean is the largest region in which iron limits the growth of phytoplankton. However, a phytoplankton bloom thousands of square kilometres in area forms each spring‐summer in the Indian sector of the Southern Ocean, both above and to the east of the Kerguelen Plateau. The central region of the Kerguelen Plateau hosts the volcanically active islands, Heard and McDonald (HIMI), the former of which is largely covered by glaciers. The sources and processes governing supply of iron from HIMI to the region are relatively unknown. In the austral summer of 2016, the first voyage to focus on biogeochemical cycling in the HIMI region was undertaken (GEOTRACES process study GIpr05). Using dissolved iron (II) (DFe (II)) and hydrogen peroxide (H2O2) measurements, we are able to resolve iron sources and show that each of the adjacent islands are strong sources of reduced iron, though controlled by different supply mechanisms.

At Heard Island, the greatest DFe (II) concentrations (0.57 nmol L‐1) were detected north of the island. An inverse correlation of DFe (II) concentrations with salinity suggests the origin is from a sea‐terminating glacier on the island. At McDonald Islands, the greatest DFe (II) concentrations (1.01 nmol L‐1) were detected east of the islands which, based on DFe (II) profiles from five targeted stations, appears likely to originate from shallow diffuse hydrothermalism. Elevated DFe (II) around HIMI may increase Fe availability for biota and has implications for transport of Fe away from the islands to the broader northern Kerguelen Plateau where the annual plankton bloom is strongest.

Item Details

Item Type:Refereed Article
Keywords:GEOTRACES, biogeochemistry, iron, trace metal, Southern Ocean, Kerguelen Plateau
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Understanding climate change
Objective Field:Effects of climate change on Antarctic and sub-Antarctic environments (excl. social impacts)
UTAS Author:Holmes, TM (Dr Thomas Holmes)
UTAS Author:Wuttig, K (Dr Kathrin Wuttig)
UTAS Author:Chase, Z (Professor Zanna Chase)
UTAS Author:Schallenberg, C (Dr Christina Schallenberg)
UTAS Author:van der Merwe, P (Dr Pier van der Merwe)
UTAS Author:Townsend, AT (Associate Professor Ashley Townsend)
UTAS Author:Bowie, AR (Professor Andrew Bowie)
ID Code:140938
Year Published:2020
Deposited By:Oceans and Cryosphere
Deposited On:2020-09-15
Last Modified:2021-02-11
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