Evolution of the stable carbon isotope composition of atmospheric CO₂ over the last glacial cycle

Eggleston, S.; Schmitt, J.; Bereiter, B.; Schneider, R.; Fischer, H. (2016). Evolution of the stable carbon isotope composition of atmospheric CO₂ over the last glacial cycle. Paleoceanography, 31(3), pp. 434-452. American Geophysical Union 10.1002/2015PA002874

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We present new δ¹³C measurements of atmospheric CO₂ covering the last glacial/interglacial cycle, complementing previous records covering Terminations I and II. Most prominent in the new record is a significant depletion in δ¹³C(atm) of 0.5‰ occurring during marine isotope stage (MIS) 4, followed by an enrichment of the same magnitude at the beginning of MIS 3. Such a significant excursion in the record is otherwise only observed at glacial terminations, suggesting that similar processes were at play, such as changing sea surface temperatures, changes in marine biological export in the Southern Ocean (SO) due to variations in aeolian iron fluxes, changes in the Atlantic meridional overturning circulation, upwelling of deep water in the SO, and long-term trends in terrestrial carbon storage. Based on previous modeling studies, we propose constraints on some of these processes during specific time intervals. The decrease in δ¹³C(atm) at the end of MIS 4 starting approximately 64 kyr B.P. was accompanied by increasing [CO₂]. This period is also marked by a decrease in aeolian iron flux to the SO, followed by an increase in SO upwelling during Heinrich event 6, indicating that it is likely that a large amount of δ¹³C-depleted carbon was transferred to the deep oceans previously, i.e., at the onset of MIS 4. Apart from the upwelling event at the end of MIS 4 (and potentially smaller events during Heinrich events in MIS 3), upwelling of deep water in the SO remained reduced until the last glacial termination, whereupon a second pulse of isotopically light carbon was released into the atmosphere.

Item Type:

Journal Article (Original Article)

Division/Institute:

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

UniBE Contributor:

Eggleston, Sarah Skye; Schmitt, Jochen; Bereiter, Bernhard; Schneider, Robert and Fischer, Hubertus

Subjects:

500 Science > 530 Physics

ISSN:

0883-8305

Publisher:

American Geophysical Union

Language:

English

Submitter:

Doris Rätz

Date Deposited:

08 Jul 2016 15:35

Last Modified:

25 Sep 2016 02:30

Publisher DOI:

10.1002/2015PA002874

BORIS DOI:

10.7892/boris.83817

URI:

https://boris.unibe.ch/id/eprint/83817

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