Two-timescale carbon cycle response to an AMOC collapse

Atmospheric CO 2 concentrations (pCO 2 ) varied on millennial timescales in phase with Antarctic temperature during the last glacial period. A prevailing view has been that carbon release and uptake by the Southern Ocean dominated this millennial‐scale variability in pCO 2 . Here, using Earth System...

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Bibliographic Details
Published in:Paleoceanography and Paleoclimatology
Main Authors: Nielsen, SB, Jochum, M, Pedro, JB, Eden, C, Nuterman, R
Format: Article in Journal/Newspaper
Language:English
Published: Wiley-Blackwell Publishing Inc. 2019
Subjects:
Earth Sciences
Climate change science
Climate change processes
Antarctic
Southern Ocean
Antarc*
ice core
Online Access:https://doi.org/10.1029/2018PA003481
http://ecite.utas.edu.au/137184
Description
Summary:Atmospheric CO 2 concentrations (pCO 2 ) varied on millennial timescales in phase with Antarctic temperature during the last glacial period. A prevailing view has been that carbon release and uptake by the Southern Ocean dominated this millennial‐scale variability in pCO 2 . Here, using Earth System Model experiments with an improved parameterization of ocean vertical mixing, we find a major role for terrestrial and oceanic carbon releases in driving the pCO 2 trend. In our simulations, a change in Northern Hemisphere insolation weakens the Atlantic Meridional Overturning Circulation (AMOC) leading to increasing pCO 2 and Antarctic temperatures. The simulated rise in pCO 2 is caused in equal parts by increased CO 2 outgassing from the global ocean due to a reduced biological activity and changed ventilation rates, and terrestrial carbon release as a response to southward migration of the Intertropical Convergence Zone. The simulated terrestrial release of carbon could explain stadial declines in organic carbon reservoirs observed in recent ice core δ 13 C measurements. Our results show that parallel variations in Antarctic temperature and pCO 2 do not necessitate that the Southern Ocean dominates carbon exchange; instead, changes in carbon flux from the global ocean and land carbon reservoirs can explain the observed pCO 2 (and δ 13 C) changes.

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