Impact of oceanic circulation changes on atmospheric δ¹³ CO₂

Menviel, L.; Mouchet, A.; Meissner, K. J.; Joos, F.; England, M. H. (2015). Impact of oceanic circulation changes on atmospheric δ¹³ CO₂. Global Biogeochemical Cycles, 29(11), pp. 1944-1961. American Geophysical Union 10.1002/2015GB005207

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δ¹³ CO₂ measured in Antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial-scale changes in atmospheric CO₂. However, the interpretation of δ¹³ CO₂ is not straight-forward. Using carbon isotope-enabled versions of the LOVECLIM and Bern3D models, we perform a set of sensitivity experiments in which the formation rates of North Atlantic Deep Water (NADW), North Pacific Deep Water (NPDW), Antarctic Bottom Water (AABW), and Antarctic Intermediate Water (AAIW) are varied. We study the impact of these circulation changes on atmospheric δ¹³ CO₂ as well as on the oceanic δ¹³ CO₂ distribution. In general, we find that the formation rates of AABW, NADW, NPDW, and AAIW are negatively correlated with changes in δ¹³ CO₂: namely, strong oceanic ventilation decreases atmospheric δ¹³ CO₂. However, since large-scale oceanic circulation reorganizations also impact nutrient utilization and the Earth’s climate, the relationship between atmospheric δ¹³ CO₂ levels and ocean ventilation rate is not unequivocal. In both models atmospheric δ¹³ CO₂ is very sensitive to changes in AABW formation rates: increased AABW formation enhances the transport of low δ¹³ CO₂ waters to the surface and decreases atmospheric δ¹³ CO₂. By contrast, the impact of NADW changes on atmospheric δ¹³ CO₂ is less robust and might be model dependent. This results from complex interplay between global climate, carbon cycle, and the formation rate of NADW, a water body characterized by relatively high δ¹³ CO₂.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Physics Institute > Climate and Environmental Physics

UniBE Contributor:

Joos, Fortunat

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology

ISSN:

0886-6236

Publisher:

American Geophysical Union

Language:

English

Submitter:

Doris Rätz

Date Deposited:

28 Dec 2015 10:45

Last Modified:

15 Nov 2016 15:25

Publisher DOI:

10.1002/2015GB005207

BORIS DOI:

10.7892/boris.74402

URI:

https://boris.unibe.ch/id/eprint/74402

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