Preprints
https://doi.org/10.5194/cp-2021-143
https://doi.org/10.5194/cp-2021-143

  01 Nov 2021

01 Nov 2021

Review status: this preprint is currently under review for the journal CP.

Impact of terrestrial biosphere on the atmospheric CO2 concentration across Termination V

Gabriel Hes1,4, Maria Fernanda Sánchez Goñi2,4, and Nathaelle Bouttes3 Gabriel Hes et al.
  • 1Département de Géosciences, École Normale Supérieure, PSL Université, Paris, France
  • 2Ecole Pratique des Hautes Etudes (EPHE), PSL University, Allée Geoffroy Saint-Hilaire Bât. 18N, 33615 Pessac cedex, France
  • 3Laboratoire des Sciences du Climat et de l’environnement, LSCE/IPSL, CEA-CNRS-UVSQ-Université Paris Saclay, F91-198, Gif sur Yvette, France
  • 4Université de Bordeaux, UMR CNRS 5805 EPOC, Allée Geoffroy Saint-Hilaire Bât. 18N, 33615 Pessac cedex, France

Abstract. Among the 100 kyr climatic cycles of the late Pleistocene, Termination V (TV, ~[404-433] kyr BP), the fifth last deglaciation, stands out for its minimum in astronomical forcing associated paradoxically with maxima in sea level, Antarctic temperature and atmospheric CO2 concentration. However, the driving mechanisms explaining TV remain only partially understood. For instance, climate models cannot fully represent the atmospheric CO2 variation observed in paleoclimate data. Aside from essential oceanic circulation processes, there is increasing evidence that terrestrial biosphere may have played a key role in the global carbon cycle. This study proposes a three-step integrated approach, combining regional and global vegetation records with modeling results, to unveil the evolution of terrestrial biosphere and its contribution to the carbon cycle during TV. First, we provide a new high resolution (~700 years) deep-sea pollen record from the Gulf of Cadiz (Site U1386, 36°49.680 N; 7°45.320 W) for TV, which shows a moderate expansion of the Mediterranean forest. We then construct the first global forest pollen database for this period. Our compilation features distinct evolutions for different types of forest, highlighting a strong development of temperate and boreal forest which may have delayed the atmospheric CO2 increase during TV. Finally, the direct comparison of global simulated forests (iLOVECLIM model) to our pollen database reveals consistent forest evolutions despite model biases, thereby supporting a CO2 mitigation by high latitude forests of the northern hemisphere.

Gabriel Hes et al.

Status: open (until 27 Dec 2021)

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Gabriel Hes et al.

Gabriel Hes et al.

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Short summary
Termination V (TV, ~[404-433] kyr BP) marks a transition in the climate system towards amplified glacial-interglacial cycles. While the associated atmospheric CO2 changes are mostly attributed to the Southern Ocean, little is known about the terrestrial biosphere contribution to the carbon cycle. The present study provides the first (model and pollen-based) reconstruction of global forests highlighting the key role of temperate and boreal forests in the mitigation of atmospheric CO2 during TV.