HR: 0800h
AN: PP41A-0637    [Abstracts]
TI: Glacial-Interglacial Variations of Atmospheric CO2 Concentration: A Modeling Study for the Effect of the Southern Ocean
AU: * Kurahashi-Nakamura, T
EM: kijun@jamstec.go.jp
AF: Frontier Research Center for Global Change, JAMSTEC, 3173-25 Showamachi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Abe-Ouchi, A
EM: abeouchi@ccsr.u-tokyo.ac.jp
AF: Frontier Research Center for Global Change, JAMSTEC, 3173-25 Showamachi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Abe-Ouchi, A
EM: abeouchi@ccsr.u-tokyo.ac.jp
AF: Center for Climate System Research, The Univ. of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, 277-8568 Japan
AU: Yamanaka, Y
EM: galapen@ees.hokudai.ac.jp
AF: Div. of Earth System Science, Hokkaido Univ., N10W5, Kita-ku, Sapporo, 060-0810 Japan
AU: Misumi, K
EM: misumi@ees.hokudai.ac.jp
AF: Section of Earth System Science, Hokkaido Univ., N10W5, Kita-ku, Sapporo, 060-0810 Japan
AB: Ancient air trapped in Antarctic ice cores shows that atmospheric CO₂ concentration, pCO₂, was lower during glacial periods than during interglacial periods. At the Last Glacial Maximum (LGM), pCO₂ was 180-200 ppm which is 80-100 lower than the preanthropogenic value. This observation suggests that variations in pCO₂ has played an important role in global climate change during the late Quaternary. Although many hypotheses have been proposed to explain the pCO₂ variations, the reason for the low glacial pCO₂ is still unclear. Several recent studies using various ocean models have examined model sensitivities to changes in sea ice extent or biological activity in the Southern Ocean on pCO₂ and discussed the effect of the Southern Ocean on the low pCO₂. However, there are clear differences in the model behaviors between box models and general circulation models (GCM). In order to consider this problem, we introduce an Ocean GCM from CCSR (COCO3.4) coupled with a simple biogeochemical model to deal with a carbon cycle in the ocean. Using this model, we simulate the ocean circulation, distribution of chemical tracers, and obtain pCO₂ during an interglacial period of 280 ppm. Then we conduct some numerical experiments on the effect of sea ice and biological activity in the Southern Ocean on the pCO₂. As a result, it is shown that interruption of CO₂ exchange at the sea surface by sea ice has little effect on pCO₂, which is consistent with results obtained by other GCMs. On the other hand, enhanced biological pump in the Southern Ocean could cause pCO₂ reduction up to several tens ppm. The difference in model behaviors between box models and our GCM is also discussed in this study.
DE: 4806 Carbon cycling (0428)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4926 Glacial
DE: 4930 Greenhouse gases
DE: 4936 Interglacial
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005