Climate Science

Seasonal Sink

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Science  11 Feb 2011:
Vol. 331, Issue 6018, pp. 651
DOI: 10.1126/science.331.6018.651-b

It is widely understood that the Southern Ocean (all of the ocean south of about 30°S latitude) is a net sink for atmospheric CO2, but estimates of how much CO2 it removes from the atmosphere vary widely, mostly due to a lack of sufficient observational constraints, particularly in the Southern Pacific. In order to quantify and characterize CO2 uptake in that region, Barbero et al. measured CO2 partial pressure and a variety of other parameters related to CO2 dynamics in the surface ocean of the Pacific Subantarctic Zone (approximately 40°S to 55°S) on four cruises conducted between 2004 and 2006 and with instruments on surface drifters. From these measurements, they were able to describe the variability in air-sea CO2 exchange on a basin-wide scale, as well as the relationships observed between CO2 parameters, ocean mixed-layer depth, and temperature—information that helped them construct a better dynamical picture of the CO2 exchange occurring there. They found that the Pacific Subantarctic Zone is a CO2 sink during spring and summer and is close to equilibrium or is a weak source during the winter. On an annual basis, the Pacific Subantarctic Zone is a sink for atmospheric CO2 but a weaker one than previously suggested. More of this type of work is needed to determine the finer-scale details of CO2 uptake by the Southern Ocean.

Global Biogeochem. CyC. 25, 10.1029/2010GB003818 (2011).

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