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| Titel |
Did high Neo-Tethys subduction rates contribute to early Cenozoic warming? |
| VerfasserIn |
G. Hoareau, B. Bomou, D. J. J. van Hinsbergen, N. Carry, D. Marquer, Y. Donnadieu, G. Le Hir, B. Vrielynck, A.-V. Walter-Simonnet |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 12 ; Nr. 11, no. 12 (2015-12-18), S.1751-1767 |
| Datensatznummer |
250117492
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| Publikation (Nr.) |
 copernicus.org/cp-11-1751-2015.pdf |
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| Zusammenfassung |
| The 58–51 Ma interval was characterized by a long-term increase of global
temperatures (+4 to +6 °C) up to the Early Eocene Climate
Optimum (EECO, 52.9–50.7 Ma), the warmest interval of the Cenozoic. It was
recently suggested that sustained high atmospheric pCO2, controlling
warm early Cenozoic climate, may have been released during Neo-Tethys
closure through the subduction of large amounts of pelagic carbonates and
their recycling as CO2 at arc volcanoes. To analyze the impact of
Neo-Tethys closure on early Cenozoic warming, we have modeled the volume of
subducted sediments and the amount of CO2 emitted along the northern
Tethys margin. The impact of calculated CO2 fluxes on global
temperature during the early Cenozoic have then been tested using a climate
carbon cycle model (GEOCLIM). We show that CO2 production may have
reached up to 1.55 × 1018 mol Ma−1 specifically during the EECO,
~ 4 to 37 % higher that the modern global volcanic CO2
output, owing to a dramatic India-Asia plate convergence increase. The
subduction of thick Greater Indian continental margin carbonate sediments at
~ 55–50 Ma may also have led to additional CO2 production
of 3.35 × 1018 mol Ma−1 during the EECO, making a total of 85 % of the
global volcanic CO2 outgassed. However, climate modeling demonstrates
that timing of maximum CO2 release only partially fits with the EECO,
and that corresponding maximum pCO2 values (750 ppm) and surface warming
(+2 °C) do not reach values inferred from geochemical proxies, a
result consistent with conclusions arising from modeling based on other
published CO2 fluxes. These results demonstrate that CO2 derived
from decarbonation of Neo-Tethyan lithosphere may have possibly contributed
to, but certainly cannot account alone for early Cenozoic warming. Other
commonly cited sources of excess CO2 such as enhanced igneous province
volcanism also appear to be up to 1 order of magnitude below fluxes
required by the model to fit with proxy data of pCO2 and temperature at
that time. An alternate explanation may be that CO2 consumption, a key
parameter of the long-term atmospheric pCO2 balance, may have been
lower than suggested by modeling. These results call for a better
calibration of early Cenozoic weathering rates. |
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