Journal metrics

Journal metrics

  • IF value: 3.174 IF 3.174
  • IF 5-year value: 3.841 IF 5-year 3.841
  • CiteScore value: 3.48 CiteScore 3.48
  • SNIP value: 1.078 SNIP 1.078
  • SJR value: 1.981 SJR 1.981
  • IPP value: 3.38 IPP 3.38
  • h5-index value: 42 h5-index 42
  • Scimago H index value: 58 Scimago H index 58
Volume 14, issue 2 | Copyright
Clim. Past, 14, 239-253, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Mar 2018

Research article | 02 Mar 2018

Response of the carbon cycle in an intermediate complexity model to the different climate configurations of the last nine interglacials

Nathaelle Bouttes1, Didier Swingedouw1, Didier M. Roche2,3, Maria F. Sanchez-Goni1,4, and Xavier Crosta1 Nathaelle Bouttes et al.
  • 1Univ. Bordeaux, EPOC, UMR 5805, 33615 Pessac, France
  • 2Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
  • 3Earth and Climate Cluster, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
  • 4EPHE, PSL Research University, 33615 Pessac, France

Abstract. Atmospheric CO2 levels during interglacials prior to the Mid-Brunhes Event (MBE,  ∼ 430ka BP) were around 40ppm lower than after the MBE. The reasons for this difference remain unclear. A recent hypothesis proposed that changes in oceanic circulation, in response to different external forcings before and after the MBE, might have increased the ocean carbon storage in pre-MBE interglacials, thus lowering atmospheric CO2. Nevertheless, no quantitative estimate of this hypothesis has been produced up to now. Here we use an intermediate complexity model including the carbon cycle to evaluate the response of the carbon reservoirs in the atmosphere, ocean and land in response to the changes of orbital forcings, ice sheet configurations and atmospheric CO2 concentrations over the last nine interglacials. We show that the ocean takes up more carbon during pre-MBE interglacials in agreement with data, but the impact on atmospheric CO2 is limited to a few parts per million. Terrestrial biosphere is simulated to be less developed in pre-MBE interglacials, which reduces the storage of carbon on land and increases atmospheric CO2. Accounting for different simulated ice sheet extents modifies the vegetation cover and temperature, and thus the carbon reservoir distribution. Overall, atmospheric CO2 levels are lower during these pre-MBE simulated interglacials including all these effects, but the magnitude is still far too small. These results suggest a possible misrepresentation of some key processes in the model, such as the magnitude of ocean circulation changes, or the lack of crucial mechanisms or internal feedbacks, such as those related to permafrost, to fully account for the lower atmospheric CO2 concentrations during pre-MBE interglacials.

Download & links
Publications Copernicus
Short summary
Atmospheric CO2 is key for climate change. CO2 is lower during the oldest warm period of the last million years, the interglacials, than during the most recent ones (since 430 000 years ago). This difference has not been explained yet, but could be due to changes of ocean circulation. We test this hypothesis and the role of vegetation and ice sheets using an intermediate complexity model. We show that only small changes of CO2 can be obtained, underlying missing feedbacks or mechanisms.
Atmospheric CO2 is key for climate change. CO2 is lower during the oldest warm period of the...