Climate Science

Reservoir Doubts

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Science  04 Mar 2011:
Vol. 331, Issue 6021, pp. 1114
DOI: 10.1126/science.331.6021.1114-b

As the last ice age came to an end, the concentration of atmospheric CO2 increased rapidly, and its 14C content declined precipitously between 17.5 and 14.5 thousand years ago. The favored explanation for this drop in the proportion of 14CO2 is that a large amount of old carbon—that is, carbon whose inventory of radioactive 14C had been depleted with age—was outgassed from a deep ocean reservoir where it had been isolated for many thousands of years. That scenario makes good intuitive sense, but conclusive evidence for a reservoir of aged carbon has not yet been found. Hain et al. use an 18-box ocean model to simulate the history of deglacial CO2 and evaluate the likelihood that an old deep-ocean CO2 reservoir was in fact the source of the observed 14C anomaly. They conclude that such a transfer of carbon was unlikely, based on inconsistencies with other records such as those of the 14C history of other depths and regions of the ocean, ocean carbonate and oxygen changes over the interval, and constraints on mixing imposed by ocean circulation.

Geophys. Res. Lett. 38, L04604 (2011).

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