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Dissolved Fe and Al in the upper 1000 m of the eastern Indian Ocean: A high-resolution transect along 95°E from the Antarctic margin to the Bay of Bengal

Dissolved Fe and Al in the upper 1000 m of the eastern Indian Ocean: A high-resolution transect along 95°E from the Antarctic margin to the Bay of Bengal
Dissolved Fe and Al in the upper 1000 m of the eastern Indian Ocean: A high-resolution transect along 95°E from the Antarctic margin to the Bay of Bengal



A high-resolution section of dissolved iron (dFe) and aluminum (dAl) was obtained along ~95°E in the upper 1000?m of the eastern Indian Ocean from the Antarctic margin (66°S) to the Bay of Bengal (18°N) during the U.S. Climate Variability and Predictability (CLIVAR) CO2 Repeat Hydrography I08S and I09N sections (February–April 2007). In the Southern Ocean, low concentrations of dAl (<1?n M) reflect the negligible dust inputs impacting the water masses subducted in the circumpolar domain. The low dAl concentrations characterizing the Southern Ocean terminate near 45°S, probably because of the advection of subtropical water masses that received dust and sedimentary inputs in their formation region. Our subsurface dFe data near the southern Kerguelen Plateau were significantly higher than historical observations in other Indian sectors of the Southern Ocean. We surmise that the offshore advection of dFe-rich waters along the western flank of the southern Kerguelen plateau and enhanced vertical mixing could contribute to this elevated subsurface dFe inventory. Elevated subsurface particulate and dFe levels downstream of the northern Kerguelen Plateau may reflect long-range lateral transport from the plateau's sediments and/or remineralization inputs. At the northern edge of the south Indian subtropical gyre, the deposition of Australian dust, possibly combined with the advection of dAl-enriched waters from the Indonesian Throughflow, creates a region of elevated dAl in the upper 400?m but without a corresponding enrichment in dFe. In the northern Indian Ocean, the South Equatorial Current constitutes a remarkable biogeochemical front separating the oxygen-rich and dFe-poor subtropical gyre waters from the dFe-rich and oxygen-depleted waters of the northern Indian Ocean. By tracing the accumulation of macronutrients and dFe along the advective pathway of Indian Central Water, we show that the central waters of the northern Indian Ocean receive excess dFe in addition to that produced by remineralization inputs. The resuspension of shelf sediments and release of pore waters probably contribute to the elevated dFe and dAl levels observed below the highly stratified upper layers of the Bay of Bengal.
CLIVAR, dissolved Fe, dissolved Al, Indian Ocean, Bay of Bengal, Kerguelen Plateau
0886-6236
375-396
Grand, Maxime M.
659acbde-d639-42b7-9fab-52fa1b3655ff
Measures, Christopher I.
bee0ab0a-cbec-491e-bcfa-e0cec9df67bb
Hatta, Mariko
b8c210ca-90aa-4660-b1b7-3538b120e31d
Hiscock, William T.
57d2eb7d-bf3d-4423-95c5-8ca254b4a513
Landing, William M.
26eb4b62-d05c-42bb-a757-f840915f6576
Morton, Peter L.
b759bd86-5942-4389-8962-ac9b84981e45
Buck, Clifton S.
71ceb13c-c706-4071-a910-b0018a84b3ff
Barrett, Pamela M.
66045f1b-bf4d-4c20-b73c-d1f6e0ad4fc6
Resing, Joseph A.
10aa7ef6-6c66-4be8-85c6-7a28db61e200
Grand, Maxime M.
659acbde-d639-42b7-9fab-52fa1b3655ff
Measures, Christopher I.
bee0ab0a-cbec-491e-bcfa-e0cec9df67bb
Hatta, Mariko
b8c210ca-90aa-4660-b1b7-3538b120e31d
Hiscock, William T.
57d2eb7d-bf3d-4423-95c5-8ca254b4a513
Landing, William M.
26eb4b62-d05c-42bb-a757-f840915f6576
Morton, Peter L.
b759bd86-5942-4389-8962-ac9b84981e45
Buck, Clifton S.
71ceb13c-c706-4071-a910-b0018a84b3ff
Barrett, Pamela M.
66045f1b-bf4d-4c20-b73c-d1f6e0ad4fc6
Resing, Joseph A.
10aa7ef6-6c66-4be8-85c6-7a28db61e200

Grand, Maxime M., Measures, Christopher I., Hatta, Mariko, Hiscock, William T., Landing, William M., Morton, Peter L., Buck, Clifton S., Barrett, Pamela M. and Resing, Joseph A. (2015) Dissolved Fe and Al in the upper 1000 m of the eastern Indian Ocean: A high-resolution transect along 95°E from the Antarctic margin to the Bay of Bengal. Global Biogeochemical Cycles, 29 (3), 375-396. (doi:10.1002/2014GB004920).

Record type: Article

Abstract




A high-resolution section of dissolved iron (dFe) and aluminum (dAl) was obtained along ~95°E in the upper 1000?m of the eastern Indian Ocean from the Antarctic margin (66°S) to the Bay of Bengal (18°N) during the U.S. Climate Variability and Predictability (CLIVAR) CO2 Repeat Hydrography I08S and I09N sections (February–April 2007). In the Southern Ocean, low concentrations of dAl (<1?n M) reflect the negligible dust inputs impacting the water masses subducted in the circumpolar domain. The low dAl concentrations characterizing the Southern Ocean terminate near 45°S, probably because of the advection of subtropical water masses that received dust and sedimentary inputs in their formation region. Our subsurface dFe data near the southern Kerguelen Plateau were significantly higher than historical observations in other Indian sectors of the Southern Ocean. We surmise that the offshore advection of dFe-rich waters along the western flank of the southern Kerguelen plateau and enhanced vertical mixing could contribute to this elevated subsurface dFe inventory. Elevated subsurface particulate and dFe levels downstream of the northern Kerguelen Plateau may reflect long-range lateral transport from the plateau's sediments and/or remineralization inputs. At the northern edge of the south Indian subtropical gyre, the deposition of Australian dust, possibly combined with the advection of dAl-enriched waters from the Indonesian Throughflow, creates a region of elevated dAl in the upper 400?m but without a corresponding enrichment in dFe. In the northern Indian Ocean, the South Equatorial Current constitutes a remarkable biogeochemical front separating the oxygen-rich and dFe-poor subtropical gyre waters from the dFe-rich and oxygen-depleted waters of the northern Indian Ocean. By tracing the accumulation of macronutrients and dFe along the advective pathway of Indian Central Water, we show that the central waters of the northern Indian Ocean receive excess dFe in addition to that produced by remineralization inputs. The resuspension of shelf sediments and release of pore waters probably contribute to the elevated dFe and dAl levels observed below the highly stratified upper layers of the Bay of Bengal.

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Accepted/In Press date: February 2015
Published date: 13 March 2015
Keywords: CLIVAR, dissolved Fe, dissolved Al, Indian Ocean, Bay of Bengal, Kerguelen Plateau
Organisations: Geochemistry

Identifiers

Local EPrints ID: 379889
URI: http://eprints.soton.ac.uk/id/eprint/379889
ISSN: 0886-6236
PURE UUID: 2eb38ca3-9334-4d56-846b-4310428d22f5
ORCID for Maxime M. Grand: ORCID iD orcid.org/0000-0001-9338-694X

Catalogue record

Date deposited: 03 Aug 2015 13:22
Last modified: 09 Dec 2019 19:51

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