| Title | The carbon cycle during the Mid Pleistocene transition; the Southern Ocean decoupling hypothesis |
| Author | Köhler, P.; Bintanja, R. |
| Author Affil | Köhler, P., Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Federal Republic of Germany. Other: Koninklijk Nederlands Meteorologisch Instituut, Netherlands |
| Source | Climate of the Past, 4(4), p.311-332, . Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1814- 9324 |
| Publication Date | 2008 |
| Notes | In English. Includes supplement: http://www.clim-past.net/4/311/2008/cp-4-311- 2008-supplement.pdf; part of special issue No. 19, Climate change; from the geological past to the uncertain future - a symposium honouring Andre Berger, edited by Crucifix, M. et al., http://www.clim- past.net/special_issue19.html; published in Climate of the Past Discussion: 9 July 2008, http://www.clim-past- discuss.net/4/809/2008/cpd-4-809-2008.html; accessed in November, 2009. 80 refs. GeoRef Acc. No: 297360. CRREL Acc. No: 64002369 |
| Index Terms | carbon isotopes; climatic change; geochemical cycles; glaciation; isotopes; oxygen; paleoclimatology; Pleistocene; Antarctica--Dome C; Southern Ocean; Antarctica; benthic environment; C-13/C-12; carbon; carbon cycle; carbon dioxide; Cenozoic; climate change; cycles; decoupling; deglaciation; Dome C; EPICA; geochemical cycle; glacial extent; ice cores; interglacial environment; isotope ratios; middle Pleistocene; O-18/O-16; paleotemperature; Quaternary; stable isotopes; Wilkes Land |
| Abstract | Various hypotheses were proposed within recent years for the interpretation of the Mid Pleistocene Transition (MPT), which occurred during past 2 000 000 years (2 Myr). We here add to already existing theories on the MPT some data and model-based aspects focusing on the dynamics of the carbon cycle. We find that the average glacial/interglacial (G/IG) amplitudes in benthic #2d13C derived from sediment cores in the deep Pacific ocean increased across the MPT by ~ 40%, while similar amplitudes in benthic #2d18O stack LR04 increased by a factor of two over the same time interval. The global carbon cycle box model BICYCLE is used for the interpretation of these observed changes in the carbon cycle. Our simulation approach is based on regression analyses of various paleo- climatic proxies with the LR04 benthic delta 18O stack over the last 740 kyr, which are then used to extrapolate changing climatic boundary conditions over the whole 2 Myr time window. The observed dynamics in benthic #2d13C cannot be explained if similar relations between LR04 and the individual climate variables are assumed prior and after the MPT. According to our analysis a model- based reconstruction of G/IG amplitudes in deep Pacific delta 13C before the MPT is possible if we assume a different response to the applied forcings in the Southern Ocean prior and after the MPT. This behaviour is what we call the "Southern Ocean Decoupling Hypothesis". This decoupling might potentially be caused by a different cryosphere/ocean interaction and thus changes in the deep and bottom water formation rates in the Southern Ocean before the MPT, however an understanding from first principles remains elusive. Our hypothesis is also proposing dynamics in atmospheric pCO2 over the past 2 Myr. Simulated pCO2 is varying between 180 and 260µatm before the MPT. The consequence of our Southern Ocean Decoupling Hypothesis is that the slope in the relationship between Southern Ocean SST and atmospheric pCO2 is different before and after the MPT, something for which first indications already exist in the 800 kyr CO2 record from the EPICA Dome C ice core. We finally discuss how our findings are related to other hypotheses on the MPT. |
| URL | http://www.clim-past.net/4/311/2008/cp-4-311-2008.pdf |
| Publication Type | journal article |
| Record ID | 87510 |