Manganese and iron in Indian Ocean waters

Journal Article · Fri Sep 01 00:00:00 EDT 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90348-7· OSTI ID:7164185

Saager, P M; De Baar, H J.W. ^[1]; Burkill, P H ^[2]

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1. NWO Laboratorium voor Isotopen Geologie, Amsterdam (Netherlands)
2. Plymouth Marine Laboratory (England)

The first vertical profiles of dissolved Mn and Fe for the (NW) Indian Ocean are reported. The area is characterized by seasonal upwelling and a broad oxygen minimum zone in intermediate waters. The dissolved Fe-profile exhibits a maximum (5.1 nM) in the oxygen minimum zone, with low values both in surface waters (0.3 nM) and deep waters (around 1 nM). Mn concentrations in the surface waters are elevated (2.0-4.3 nM), and decrease rapidly in an offshore direction. Below the first 25 m, concentrations decrease dramatically (0.5-1.3 nM), indicating removal by oxidation and particle scavenging. Further down, various Mn maxima are observed which can be related to hydrographic features. The include the facts that: intermediate water originating from the Red Sea lost its dissolved O{sub 2} while flowing northward along the Omani coast and exhibits a strong Mn maximum (4.6-6.5 nM) coincident with the deep O{sub 2} minimum; at the two inshore stations in the Gulf of Oman this is overlain by relatively modest Mn maxima ({plus minus}2.7 nM) related to Arabian Gulf overflow water; and the strong Mn maxima (4.4-5.6 nM) in the oxygen minimum zone at the two offshore stations are related to yet another watermass. Below these various maxima, concentrations decrease gradually to values as low as 90 pM at 2,000 meters depth. Towards the sea floor concentrations increase again, leading to a modest bottom water maximum (0.7-1.5 nM). The overall vertical distributions of Mn and Fe are strikingly similar, also in actual concentrations, to those previously reported for the eastern equatorial Pacific, an area also characterized by an extensive O{sub 2}-minimum zone.

• OSTI ID: 7164185
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 53:9; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
INDIAN OCEAN
WATER CHEMISTRY
IRON
ECOLOGICAL CONCENTRATION
SOLUBILITY
THERMODYNAMIC ACTIVITY
MANGANESE
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CONCENTRATION RATIO
GEOCHEMISTRY
REACTION KINETICS
REDOX REACTIONS
CHEMICAL REACTIONS
CHEMISTRY
ELEMENTS
KINETICS
METALS
SEAS
SURFACE WATERS
TRANSITION ELEMENTS
580000* - Geosciences