In:
Climate of the Past, Copernicus GmbH, Vol. 14, No. 2 ( 2018-03-02), p. 239-253
Kurzfassung:
Abstract. Atmospheric CO2 levels during interglacials prior to the Mid-Brunhes Event (MBE, ∼ 430 ka BP) were
around 40 ppm 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.
Materialart:
Online-Ressource
ISSN:
1814-9332
DOI:
10.5194/cp-14-239-2018
DOI:
10.5194/cp-14-239-2018-supplement
Sprache:
Englisch
Verlag:
Copernicus GmbH
Publikationsdatum:
2018
ZDB Id:
2217985-9
