Enhanced CO2 outgassing in the Southern Ocean from a positive phase of the Southern Annular Mode


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dc.contributor.author Lovenduski, Nicole S.
dc.contributor.author Gruber, Nicolas
dc.contributor.author Doney, Scott C.
dc.contributor.author Lima, Ivan D.
dc.date.accessioned 2010-05-06T19:41:26Z
dc.date.available 2010-05-06T19:41:26Z
dc.date.issued 2007-06-20
dc.identifier.citation Global Biogeochemical Cycles 21 (2007): GB2026 en_US
dc.identifier.uri http://hdl.handle.net/1912/3406
dc.description Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 21 (2007): GB2026, doi:10.1029/2006GB002900. en_US
dc.description.abstract We investigate the interannual variability in the flux of CO2 between the atmosphere and the Southern Ocean on the basis of hindcast simulations with a coupled physical-biogeochemical-ecological model with particular emphasis on the role of the Southern Annular Mode (SAM). The simulations are run under either pre-industrial or historical CO2 concentrations, permitting us to separately investigate natural, anthropogenic, and contemporary CO2 flux variability. We find large interannual variability (±0.19 PgC yr−1) in the contemporary air-sea CO2 flux from the Southern Ocean (<35°S). Forty-three percent of the contemporary air-sea CO2 flux variance is coherent with SAM, mostly driven by variations in the flux of natural CO2, for which SAM explains 48%. Positive phases of the SAM are associated with anomalous outgassing of natural CO2 at a rate of 0.1 PgC yr−1 per standard deviation of the SAM. In contrast, we find an anomalous uptake of anthropogenic CO2 at a rate of 0.01 PgC yr−1 during positive phases of the SAM. This uptake of anthropogenic CO2 only slightly mitigates the outgassing of natural CO2, so that a positive SAM is associated with anomalous outgassing in contemporaneous times. The primary cause of the natural CO2 outgassing is anomalously high oceanic partial pressures of CO2 caused by elevated dissolved inorganic carbon (DIC) concentrations. These anomalies in DIC are primarily a result of the circulation changes associated with the southward shift and strengthening of the zonal winds during positive phases of the SAM. The secular, positive trend in the SAM has led to a reduction in the rate of increase of the uptake of CO2 by the Southern Ocean over the past 50 years. en_US
dc.description.sponsorship This work was supported by NASA headquarters under the Earth System Science Fellowship Grant NNG05GP78H to N. S. L. and grants NAG5-12528 and NNG04GH53G to N. G. Both S. C. D. and I. D. L. were supported by NSF/ONR NOPP (N000140210370) and NASA (NNG05GG30G). en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Geophysical Union en_US
dc.relation.uri http://dx.doi.org/10.1029/2006GB002900
dc.subject Southern Ocean en_US
dc.subject Carbon cycle en_US
dc.subject Southern Annular Mode en_US
dc.title Enhanced CO2 outgassing in the Southern Ocean from a positive phase of the Southern Annular Mode en_US
dc.type Article en_US
dc.identifier.doi 10.1029/2006GB002900

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