Productivity of the glacial ocean: Discussion of the iron hypothesis

Journal Article · Sun Dec 01 00:00:00 EST 1991 · Limnology and Oceanography; (United States)

DOI:https://doi.org/10.4319/lo.1991.36.8.1899· OSTI ID:6994201

Berger, W H ^[1]; Wefer, G ^[2]

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1. Scripps Institution of Oceanography, La Jolla (United States)
2. Univ. Bremen (Germany)

An increase in the productivity of the glacial-age Southern Ocean has been postulated to explain the decrease in pCO{sub 2} of the atmosphere observed in ice cores. A plausible mechanism has been proposed elsewhere that productivity is limited by the availability of Fe in this region and that the greater supply of eolian dust during glacial time removed this limit. Recently published evidence from cores from the Southern Ocean suggests that in fact there was no change in productivity in the assumed manner. Glacial-age productivity was indeed greatly increased in the equatorial Pacific and in the eastern boundary upwelling systems. The cause, presumably, was the mechanical action of glacial-age winds rather than a greater supply of Fe. However, a role of increased supply of micronutrients from the continents in the increase of equatorial productivity during glacial time cannot be excluded. Such enhancement from increased supply of dust would have the interesting corollary of more efficient export transfer to depth, possibly contributing to nutrient depletion in glacial-age, deep intermediate waters. There is some indication, as well, of a general decrease in nutrient content in the tropical thermocline in the western Pacific during the last several million years, a depletion that may have been fostered by increasing supply of dust from emerging Asian highlands. Alternative explanations are available. The case for Fe as a major modifier of productivity and biogenic sedimentation on geological time scales cannot be made in the absence of criteria diagnostic for Fe supply as opposed to stirring and upwelling.

• OSTI ID: 6994201
• Journal Information: Limnology and Oceanography; (United States), Vol. 36:8; ISSN 0024-3590
• Country of Publication: United States
• Language: English

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