Last Glacial Maximum CO2 and δ13C successfully reconciled

Nathaëlle Bouttes (1, 2) , D. Paillard (1) , Didier M. Roche (1, 2) , V. Brovkin (3) , L. Bopp (1)

1 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
2 CLIM - Modélisation du climat
3 PIK - Potsdam Institute for Climate Impact Research

[1] During the Last Glacial Maximum (LGM, ∼21,000 years ago) the cold climate was strongly tied to low atmospheric CO 2 concentration (∼190 ppm). Although it is generally assumed that this low CO 2 was due to an expansion of the oceanic carbon reservoir, simulating the glacial level has remained a challenge especially with the additional d 13 C constraint. Indeed the LGM carbon cycle was also characterized by a modern-like d 13 C in the atmosphere and a higher surface to deep Atlantic d 13 C gradient indicating probable changes in the thermohaline circulation. Here we show with a model of intermediate complexity, that adding three oceanic mechanisms: brine induced stratification, stratification-dependant diffusion and iron fertilization to the standard glacial simulation (which includes sea level drop, temperature change, carbonate compensation and terrestrial carbon release) decreases CO 2 down to the glacial value of ∼190 ppm and simultaneously matches glacial atmospheric and oceanic d 13 C inferred from proxy data. LGM CO 2 and d 13 C can at last be successfully reconciled.

Domaines: Océan, Atmosphère; Climatologie; Océanographie

Nathaëlle Bouttes, D. Paillard, Didier M. Roche, V. Brovkin, L. Bopp. Last Glacial Maximum CO2 and δ13C successfully reconciled. Geophysical Research Letters, 2011, 38 (2), pp.L 02705. ⟨10.1029/2010GL044499⟩. ⟨hal-02892239⟩