In:
Climate of the Past, Copernicus GmbH, Vol. 17, No. 2 ( 2021-03-26), p. 703-719
Abstract:
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.
Type of Medium:
Online Resource
ISSN:
1814-9332
DOI:
10.5194/cp-17-703-2021
DOI:
10.5194/cp-17-703-2021-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2021
detail.hit.zdb_id:
2217985-9
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