Increased particle flux to the deep ocean related to monsoons

Nair, R.R.; Ittekkot, V.; Manganini, Steven J.; Ramaswamy, V.; Haake, B.; Degens, Egon T.; Desai, B. N.; Honjo, Susumu

doi:10.1038/338749a0

Cited by 398 publications

(151 citation statements)

References 15 publications

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“…The total C org flux of ∼25 µmol cm −2 yr −1 is in line with earlier data derived Table 6. Changed model parameters compared to Reed et al (2011b from sediment traps in the Arabian Sea, which show a range of C org settling fluxes between ∼ 15 and 50 µmol cm −2 yr −1 at water depths >1000 m (Nair et al, 1989;Haake et al, 1993;Lee et al, 1998;Honjo et al, 1999 The average bulk C/N/P ratio for OM (477/50/1) was more or less constant (± 5 %) throughout the core from station 4 and this was applied to the less reactive (β) and unreactive (γ ) OM pools in the model. The high C/P ratio for these OM pools is in agreement with a degraded nature of OM at the sediment surface in the Arabian Sea (Haake et al, 1992;Woulds and Cowie, 2009).…”

Section: Model Parameterizationmentioning

confidence: 99%

Sedimentary phosphorus and iron cycling in and below the oxygen minimum zone of the northern Arabian Sea

et al. 2012

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Abstract. In this study, we investigate phosphorus (P) and iron (Fe) cycling in sediments along a depth transect from within to well below the oxygen minimum zone (OMZ) in the northern Arabian Sea (Murray Ridge). Pore-water and solid-phase analyses show that authigenic formation of calcium phosphate minerals (Ca-P) is largely restricted to where the OMZ intersects the seafloor topography, likely due to higher depositional fluxes of reactive P. Nonetheless, increased ratios of organic carbon to organic P (C org /P org ) and to total reactive P (C org /P reactive ) in surface sediments indicate that the overall burial efficiency of P relative to C org decreases under the low bottom water oxygen concentrations (BWO) in the OMZ. The relatively constant Fe/Al ratio in surface sediments along the depth transect suggest that corresponding changes in Fe burial are limited. Sedimentary pyrite contents are low throughout the ∼25 cm sediment cores at most stations, as commonly observed in the Arabian Sea OMZ. However, pyrite is an important sink for reactive Fe at one station in the OMZ. A reactive transport model (RTM) was applied to quantitatively investigate P and Fe diagenesis at an intermediate station at the lower boundary of the OMZ (bottom water O 2 : ∼ 14 µmol L −1 ). The RTM results contrast with earlier findings in showing that Fe redox cycling can control authigenic apatite formation and P burial in Arabian Sea sediment. In addition, results suggest that a large fraction of the sedimentary Ca-P is not authigenic, but is instead deposited from the water column and buried. Dust is likely a major source of this Ca-P. Inclusion of the unreactive Ca-P pool in the C org /P ratio leads to an overestimation of the burial efficiency of reactive P relative to C org along the depth transect. Moreover, the unreactive Ca-P accounts for ∼85 % of total Ca-P burial. In general, our results reveal large differences in P and Fe chemistry between stations in the OMZ, indicating dynamic sedimentary conditions under these oxygen-depleted waters.

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Section: Model Parameterizationmentioning

confidence: 99%

Sedimentary phosphorus and iron cycling in and below the oxygen minimum zone of the northern Arabian Sea

et al. 2012

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“…4C) is consistent with nunierous and widespread in situ observations of extreme monsoon-driven biological productivity. In summer, monsoonal upwelling (Bottero 1969, Smith & Bottero 1977, Swallow 1984, Bauer et al 1991 brings massive quantities of nutrient-rich water into the surface layer of the Arabian Sea (Ryther et al 1966, Aruga 1973, Krey & Babenerd 1973, McCill 1973, Wyrtki 1973, Swallow 1984, McCreary & Kundu 1989, resulting in dramatically increased surface-layer chlorophyll concentrations, phytoplankton biomass, and primary production (Kabanova 1968, Krey & Babenerd 1976, Banse 1987, Hitchcock & Frazel 1989, Bauer et al 1991, Brock et al 1991, making the Arabian Sea one of the world's most productive ocean basins (Nair et al 1989).…”

Section: Mixed-layer Bloom Classmentioning

confidence: 99%

Biohydro-optical classification of the northwestern Indian Ocean

Brock¹,

Sathyendranath²,

Platt³

1998

Mar. Ecol. Prog. Ser.

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“…Strong correlations exist between susceptibility and quartz (r = 0.83) and dolomite (r = 0.70). Aerosol studies have shown that these minerals are common constituents of summer monsoon dust (Stewart et al, 1965;Goldberg and Griffin, 1970;Nair et al, 1989;Sirocko and Sarnthein, 1989). These close mineralogical associations suggest that the susceptibility variations are tracking variations in the terrigenous (eolian) fraction.…”

Section: Susceptibility and Bulk Mineralogymentioning

confidence: 99%

“…Atmospheric haze frequency data, aerosol, and ocean sediment trap studies have demonstrated that most dust transport occurs during the peak months of the summer monsoon: June, July, and August (Pye, 1987, p. 76;Chester et al, 1985;Prospero, 1981;Nair et al, 1989). In particular, the sediment trap data indicate that 80% of the annual supply of terrigenous material to the western Arabian Sea occurs during these months (Nair et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

A Rock-Magnetic Record of Monsoonal Dust Deposition to the Arabian Sea: Evidence for a Shift in the Mode of Deposition at 2.4 Ma

Menocal¹,

Bloemendal²,

King³

1991

Proceedings of the Ocean Drilling Program, 117 Scientific Results

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A detailed record of eolian deposition from the Asian monsoon has been determined from measurements of magnetic susceptibility at Sites 721 and 722 located on an elevated ridge in the western Arabian Sea. Susceptibility was measured at 5-cm intervals (1 k.y.) on whole-core sections (15,000 measurements) and these data were used to construct complete composite records extending to 3.2 Ma. The composite records at Sites 721 and 722 are virtually identical, suggesting that both are complete and without local hiatuses. Bulk X-ray diffraction analyses indicate that (eolian) quartz and dolomite abundances are strongly covariant with the susceptibility data {r = 0.83, 0.70; « = 172). An almost perfect correlation (r = 0.98; n = 94) between susceptibility and terrigenous percent (determined by sequential carbonate, opal, and organic carbon extraction) indicates that susceptibility is a rapid and sensitive tracer of terrigenous fraction variations. Furthermore, terrigenous and biogenic flux calculations indicate that the observed susceptibility variations are indeed the result of terrigenous accumulation rate variations and not dilution by variations in biogenic input.In the frequency-domain, variance is concentrated at orbital periodicities for the entire 3.2 Ma sequence; however, there is a shift in the dominant periodicity at ca. 2.4 Ma. From 3.2 to 2.4 Ma, the susceptibility data vary almost purely at 23-19 k.y. periodicities and coherency with the precessional insolation forcing is high (0.89). Strong and coherent variance at the 23-19 k.y. band is maintained after 2.4 Ma but there is a dramatic increase in variance at the 41 k.y. periodicity corresponding to orbital obliquity. The timing of this shift coincides with the initiation of Northern Hemisphere glaciation and suggests a linkage between high-and low-latitude climate processes. General circulation model experiments and paleoclimatological evidence from northeast Africa suggest that the increase in 41 k.y. power after 2.4 Ma may be reflecting periodic increases in monsoon dust source area aridity due to the coeval expansion of the Eurasian and/or North American ice sheets, which varied predominantly at this periodicity.

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Increased particle flux to the deep ocean related to monsoons

Cited by 398 publications

References 15 publications

Sedimentary phosphorus and iron cycling in and below the oxygen minimum zone of the northern Arabian Sea

Sedimentary phosphorus and iron cycling in and below the oxygen minimum zone of the northern Arabian Sea

Biohydro-optical classification of the northwestern Indian Ocean

A Rock-Magnetic Record of Monsoonal Dust Deposition to the Arabian Sea: Evidence for a Shift in the Mode of Deposition at 2.4 Ma

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