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Distributions of particulate Al and Fe in the Bay of Bengal and south Indian subtropical gyre



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  • Journal Title:
    Marine Chemistry
  • Personal Author:
  • NOAA Program & Office:
  • Description:
    The trace element composition (Al, Si, P, Ca, and Fe) of suspended particulate matter is presented for the upper 1000 m of the water column along U.S. CLIVAR/CO2 Repeat Hydrography zonal section I05 (2009) in the South Indian subtropical gyre and meridional section I09N/I08S (2007) in the eastern Indian Ocean from the Bay of Bengal to the subtropical front. Along I09N, high particulate Al and Fe concentrations are found throughout the Bay of Bengal and the northern Indian Ocean indicating significant lithogenic particle loads from river-borne sediment transport and smaller contributions from continental dust flux than current model estimates. Particles have elevated Fe:Al ratios compared to the composition of local shelf sediments, indicating that suspended particulate matter becomes enriched from scavenging of dissolved Fe that accumulates in the oxygen minimum zone in the Bay of Bengal. Along I05, retroflection of the Agulhas Return Current transports African shelf-derived lithogenic particles into the western South Indian basin, resulting in the elevated subsurface concentrations of particulate Al and Fe nearly 3000 km into the interior of the subtropical gyre. Another region of elevated dissolved Fe concentrations and Fe-enriched particulate matter was also observed along I05 in intermediate waters (>600 m) in the subtropical gyre at 32°S between 70 and 74°E, suggesting inputs from a shallow sedimentary or possibly volcanic Fe source to these stations. Comparison of data from the crossover between the I05 and I09N/I08S sections and from the 2007 and 2016 occupations of I09N allows investigation of the temporal variability of basin-scale distributions of particle-associated trace metals with relatively short residence times in the upper water column. The most pronounced differences in trace metal distributions are associated with interannual variability in productive near-coastal and upwelling regions where mixed-layer pFe concentrations vary by a factor of 2–7, whereas Fe and Al in deeper waters and dust-impacted surface waters in oligotrophic regions show significantly less variability.
  • Source:
    Marine Chemistry, 275, 104611
  • DOI:
  • ISSN:
    0304-4203
  • Format:
    PDF
  • Publisher:
    Elsevier BV
  • Document Type:
    Journal Article
  • License:
  • Rights Information:
    CC BY
  • Compliance:
    Submitted
  • Main Document Checksum:
    urn:sha-512:3658c1e287d9f6f397f849bf286d01c7f140f86e104d2b9e71fd8e0af5e4854f6731884453ff97020c7b45ed732ee2f900e9fdb3a1d1b09b4c4c6486d0a6241f
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  • File Type:
    Filetype[PDF - 5.64 MB ]
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