Publication Date:
2014-07-12
Description:
We determined the 14-year change in the anthropogenic CO 2 inventory in the eastern South Pacific Ocean along the 110˚W meridian from 67˚S to 21˚N, using seawater δ 13 C datasets collected in 1994 and 2008. The vertical integral of the 14-year δ 13 C change was assessed in five latitude bands, and found to be greatest (–14.7‰ m yr –1 ) in the subpolar band (38˚S–55˚S) and smallest (–3.0‰ m yr –1 ) in the tropical band (21˚N–18˚S). The δ 13 C change in each of the latitudinal bands was primarily caused by inputs of anthropogenic CO 2 via air-sea exchange and transport. More than 50% of the total anthropogenic CO 2 was added to the subpolar band via the northward movement of Antarctic Intermediate Water (AAIW) from the south, and the remaining 50% was added via air-sea exchange. We also calculated the ratio of the temporal change in δ 13 C to the change in dissolved inorganic carbon, which is a measure of the efficiency of oceanic uptake of anthropogenic CO 2 . The ratio for AAIW in 1994 (–0.017‰ (µmol kg –1 ) –1 ) was greater than that in 2008 (–0.010‰ (µmol kg –1 ) –1 ) based on the change in preformed δ 13 C and DIC, indicating reduced efficiency of CO 2 uptake by the Southern Ocean in 2008 relative to that in 1994. AAIW remained at the surface for a shorter period in 2008 relative to 1994, and thus would have taken up less atmospheric CO 2 prior to subduction. The projected reduction in this ratio indicates a weakening of CO 2 uptake by the Southern Ocean in the future.
Print ISSN:
0886-6236
Electronic ISSN:
1944-9224
Topics:
Biology
,
Chemistry and Pharmacology
,
Geography
,
Geosciences
,
Physics
Permalink