Pagani Mark, Zachos James C, Freeman Katherine H, Tipple Brett, Bohaty Stephen
Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT 06511, USA.
Science. 2005 Jul 22;309(5734):600-3. doi: 10.1126/science.1110063. Epub 2005 Jun 16.
The relation between the partial pressure of atmospheric carbon dioxide (pCO2) and Paleogene climate is poorly resolved. We used stable carbon isotopic values of di-unsaturated alkenones extracted from deep sea cores to reconstruct pCO2 from the middle Eocene to the late Oligocene (approximately 45 to 25 million years ago). Our results demonstrate that pCO2 ranged between 1000 to 1500 parts per million by volume in the middle to late Eocene, then decreased in several steps during the Oligocene, and reached modern levels by the latest Oligocene. The fall in pCO2 likely allowed for a critical expansion of ice sheets on Antarctica and promoted conditions that forced the onset of terrestrial C4 photosynthesis.
大气二氧化碳分压(pCO₂)与古近纪气候之间的关系仍未得到很好的解决。我们利用从深海岩芯中提取的双不饱和烯酮的稳定碳同位素值,重建了始新世中期到晚渐新世(约4500万至2500万年前)的pCO₂。我们的结果表明,在始新世中期到晚始新世,pCO₂的范围在百万分之1000至1500体积分数之间,然后在渐新世期间分几个阶段下降,并在渐新世晚期达到现代水平。pCO₂的下降可能使得南极洲冰盖得以关键扩张,并促成了陆地C4光合作用开始的条件。