Atmospheric CO₂ concentrations over glacial–interglacial cycles closely correspond to Antarctic temperature patterns. These are distinct from temperature variations in the mid to northern latitudes, so this suggests that the Southern Ocean is pivotal in controlling natural CO₂ concentrations. Here we assess the sensitivity of atmospheric CO₂ concentrations to glacial–interglacial changes in the ocean’s meridional overturning circulation using a circulation model. for upwelling and eddy transport in the Southern Ocean coupled with a simple biogeochemical description. Under glacial conditions, a broader region of surface buoyancy loss results in upwelling farther to the north, relative to interglacials. The northern location of upwelling results in reduced CO₂ outgassing and stronger carbon sequestration in the deep ocean: we calculate that the shift to this glacial-style circulation can draw down 30 to 60 ppm of atmospheric CO₂. We therefore suggest that the direct effect of temperatures on Southern Ocean buoyancy forcing, and hence the residual overturning circulation, explains much of the strong correlation between Antarctic temperature variations and atmospheric CO₂ concentrations over glacial–interglacial cycles.

Item Type:	Refereed Article
Keywords:	atmospheric carbon, ocean overturning circulation, glacial climate
Research Division:	Earth Sciences
Research Group:	Oceanography
Research Field:	Physical oceanography
Objective Division:	Environmental Policy, Climate Change and Natural Hazards
Objective Group:	Understanding climate change
Objective Field:	Climate change models
UTAS Author:	Nikurashin, M (Dr Maxim Nikurashin)
ID Code:	106082
Year Published:	2015
Funding Support:	Australian Research Council (DE150100937)
Web of Science® Times Cited:	82
Deposited By:	IMAS Research and Education Centre
Deposited On:	2016-01-28
Last Modified:	2017-10-31
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