Atmospheric carbon dioxide variations across the middle Miocene climate transition



Raitzsch, Markus, Bijma, Jelle, Bickert, Torsten, Schulz, Michael, Holbourn, Ann and Kucera, Michal
(2021) Atmospheric carbon dioxide variations across the middle Miocene climate transition. CLIMATE OF THE PAST, 17 (2). pp. 703-719.

Access the full-text of this item by clicking on the Open Access link.

Abstract

<jats:p>Abstract. The middle Miocene climate transition ∼ 14 Ma marks a fundamental step towards the current “ice-house” climate, with a ∼ 1 ‰ δ18O increase and a ∼ 1 ‰ transient δ13C rise in the deep ocean, indicating rapid expansion of the East Antarctic Ice Sheet associated with a change in the operation of the global carbon cycle. The variation of atmospheric CO2 across the carbon-cycle perturbation has been intensely debated as proxy records of pCO2 for this time interval are sparse and partly contradictory. Using boron isotopes (δ11B) in planktonic foraminifers from Ocean Drilling Program (ODP) Site 1092 in the South Atlantic, we show that long-term pCO2 varied at 402 kyr periodicity between ∼ 14.3 and 13.2 Ma and follows the global δ13C variation remarkably well. This suggests a close link to precessional insolation forcing modulated by eccentricity, which governs the monsoon and hence weathering intensity, with enhanced weathering and decreasing pCO2 at high eccentricity and vice versa. The ∼ 50 kyr lag of δ13C and pCO2 behind eccentricity in our records may be related to the slow response of weathering to orbital forcing. A pCO2 drop of ∼ 200 µatm before 13.9 Ma may have facilitated the inception of ice-sheet expansion on Antarctica, which accentuated monsoon-driven carbon cycle changes through a major sea-level fall, invigorated deep-water ventilation, and shelf-to-basin shift of carbonate burial. The temporary rise in pCO2 following Antarctic glaciation would have acted as a negative feedback on the progressing glaciation and helped to stabilize the climate system on its way to the late Cenozoic ice-house world. </jats:p>

Item Type: Article
Uncontrolled Keywords: 37 Earth Sciences, 3709 Physical Geography and Environmental Geoscience, 3702 Climate Change Science, 13 Climate Action
Divisions: Faculty of Health and Life Sciences
Faculty of Health and Life Sciences > Institute of Life Courses and Medical Sciences
Faculty of Health and Life Sciences > Institute of Life Courses and Medical Sciences > School of Medicine
Depositing User: Symplectic Admin
Date Deposited: 09 Feb 2023 10:09
Last Modified: 22 Jun 2024 16:10
DOI: 10.5194/cp-17-703-2021
Open Access URL: https://doi.org/10.5194/cp-17-703-2021
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3168299