Oceans

A Conveyor Belt for Carbon

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Science  19 May 2000:
Vol. 288, Issue 5469, pp. 1137
DOI: 10.1126/science.288.5469.1137c

Dissolved organic carbon (DOC) represents a vast reservoir of carbon in the ocean and is believed to be produced in the surface waters and then transported from there to the deep ocean, where it is utilized at very low rates by free-living bacteria. Measurements of the carbon isotope composition of water from the North Atlantic and the North Pacific previously showed that DOC is quite old compared to dissolved inorganic carbon, and that DOC in the North Atlantic is younger and more abundant than in the North Pacific. On the basis of these results, it was hypothesized that the deep ocean DOC is transported via a “conveyor belt” from the North Atlantic to the North Pacific.

Druffel and Bauer have measured the carbon isotope composition of water from the Southern Ocean and find that the age of the Southern Ocean DOC is closer to that in the North Pacific, but that the DOC concentration there is almost the same as in the North Atlantic. The results support the conveyor belt movement of DOC, but also indicate an extra source of young DOC in the North Atlantic or a small microbial sink in the Southern Ocean as possible explanations for the quantitative deviations.—JU

Geophys. Res. Lett. (2000).

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