Late Quaternary changes in biogenic opal fluxes in the Southern Indian Ocean

Dezileau, Laurent; Reyss, Jean Louis; Lemoine, Flavien

doi:10.1016/s0025-3227(03)00283-4

Cited by 42 publications

(57 citation statements)

References 56 publications

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“…During the second time interval (260–440 ka), both cores had similar patterns in the δ 15 N D records. The close similarity between the two δ 15 N D records implies a common nutrient source, consistent with the suggestion by Dezileau et al [2003] of northward movement of the Polar Front, which might have kept the influence of eddies or upwelling away from site 1093. The relatively depleted δ 15 N D values observed at both sites during two glacial periods, MIS 8 and MIS 10, may suggest higher‐nutrient availability during this time period (Figure 3b, interval 2).…”

Section: Discussionsupporting

confidence: 86%

Nutrient regime at the siliceous belt of the Atlantic sector of the Southern Ocean during the past 660 ka

et al. 2008

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[1] Sediment cores from Ocean Drilling Program sites 1094 and 1093 hold the most extensive and most detailed records of carbon and nitrogen isotopes of diatom-bound organic matter in the Atlantic sector of the Southern Ocean over the past 660 ka. These records were combined with summer sea surface temperatures and winter sea ice that were deduced from diatom transfer functions to reconstruct the nutrient regime at the northern and southern boundaries of the siliceous belt at latitudes 53°S and 50°S, respectively. The strong coupling between carbon and nitrogen isotope records at site 1093 suggests that the diatom productivity was influenced mainly by changes in nutrient availability. The anticorrelation between the carbon and nitrogen isotopes at site 1094 suggests that the diatom productivity was closely linked to global temperature changes, sea ice coverage, and dissolved CO 2 concentration. A detailed comparison of the nitrogen isotope records between the two sites shows three time intervals that represent different nutrient regimes. The nutrients at site 1093, which is close to the Polar Front, were dominated by eddies and meanders that sustained relatively high productivity at times of stratification or reduced ventilation, whereas at site 1094 the nutrients were influenced by ventilation processes.Citation: Schneider-Mor, A., R. Yam, C. Bianchi, M. Kunz-Pirrung, R. Gersonde, and A. Shemesh (2008), Nutrient regime at the siliceous belt of the Atlantic sector of the Southern Ocean during the past 660 ka, Paleoceanography, 23, PA3217,

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Section: Discussionsupporting

confidence: 86%

Nutrient regime at the siliceous belt of the Atlantic sector of the Southern Ocean during the past 660 ka

et al. 2008

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“…Arguments for the validity of this approach have been examined elsewhere [ Henderson et al , 1999; Yu et al , 2001]. This approach was successfully applied where lateral re‐sedimentation is important [ Suman and Bacon , 1989; François et al , 1993, 1997; Kumar et al , 1995; Anderson et al , 1998, 2002; Frank et al , 1995, 2000; Dezileau et al , 2000, 2003; Chase et al , 2003].…”

Section: Vertical Fluxes Calculationsmentioning

confidence: 99%

Iron control of past productivity in the coastal upwelling system off the Atacama Desert, Chile

et al. 2004

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[1] Biogenic opal and organic carbon vertical rain rates in sediment cores reveal a strong cyclicity in the productivity of the upwelling system off presently arid northern Chile during the last 100,000 years. Changes in productivity are found to be in phase with the precessional cycle ($20,000 years) and with inputs of iron from the continent. During austral summer insolation maxima, increased precipitation and river runoff in the region appear to have brought high inputs of iron, mainly from the Andes, to the coastal ocean enhancing primary productivity there. We interpret our results as providing evidence for iron control of past productivity in this upwelling system and for a tight link between productivity and orbital forcing at midlatitudes.

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“…A number of studies have reconstructed opal burial in all three sectors of the Southern Ocean, and data from the Atlantic and Indian sectors of the SO show decreased glacial opal flux (relative to the Holocene) south of the Antarctic Polar Front (APF), as predicted by the SALH (the APF is defined as the northernmost limit of water with a minimum temperature less than 2°C at 200 m; in other words, the northernmost limit of upwelling [ Trull et al , 2001]). However, this decrease appears to have been offset by increased opal flux north of the APF, resulting in no net glacial‐interglacial change in either sector [ Chase et al , 2003a; Dezileau et al , 2003; Diekmann , 2007; Francois et al , 1997; Frank et al , 2000; Kumar et al , 1995].…”

Section: Introductionmentioning

confidence: 99%

Comparing glacial and Holocene opal fluxes in the Pacific sector of the Southern Ocean

et al. 2009

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[1] The silicic acid leakage hypothesis (SALH) predicts that during glacial periods excess silicic acid was transported from the Southern Ocean to lower latitudes, which favored diatom production over coccolithophorid production and caused a drawdown of atmospheric CO 2 . Downcore records of 230 Th-normalized opal (biogenic silica) fluxes from 31 cores in the Pacific sector of the Southern Ocean were used to compare diatom productivity during the last glacial period to that of the Holocene and to examine the evidence for increased glacial Si export to the tropics. Average glacial opal fluxes south of the modern Antarctic Polar Front (APF) were less than during the Holocene, while average glacial opal fluxes north of the APF were greater than during the Holocene. However, the magnitude of the increase north of the APF was not enough to offset decreased fluxes to the south, resulting in a decrease in opal burial in the Pacific sector of the Southern Ocean during the last glacial period, equivalent to approximately 15 Gt opal ka À1 . This is consistent with the work of Chase et al. (2003a), and satisfies the primary requirement of the SALH, assuming that the upwelled supply of Si was approximately equivalent during the Holocene and the glacial period. However, previous results from the equatorial oceans are inconsistent with the other predictions of the SALH, namely that either the C org :CaCO 3 ratio or the rate of opal burial should have increased during glacial periods. We compare the magnitudes of changes in the Southern Ocean and the tropics and suggest that Si escaping the glacial Southern Ocean must have had an alternate destination, possibly the continental margins. There is currently insufficient data to test this hypothesis, but the existence of this sink and its potential impact on glacial pCO 2 remain interesting topics for future study.

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Late Quaternary changes in biogenic opal fluxes in the Southern Indian Ocean

Cited by 42 publications

References 56 publications

Nutrient regime at the siliceous belt of the Atlantic sector of the Southern Ocean during the past 660 ka

Nutrient regime at the siliceous belt of the Atlantic sector of the Southern Ocean during the past 660 ka

Iron control of past productivity in the coastal upwelling system off the Atacama Desert, Chile

Comparing glacial and Holocene opal fluxes in the Pacific sector of the Southern Ocean

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