Liu Zhonghui, Pagani Mark, Zinniker David, Deconto Robert, Huber Matthew, Brinkhuis Henk, Shah Sunita R, Leckie R Mark, Pearson Ann
Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA.
Science. 2009 Feb 27;323(5918):1187-90. doi: 10.1126/science.1166368.
About 34 million years ago, Earth's climate shifted from a relatively ice-free world to one with glacial conditions on Antarctica characterized by substantial ice sheets. How Earth's temperature changed during this climate transition remains poorly understood, and evidence for Northern Hemisphere polar ice is controversial. Here, we report proxy records of sea surface temperatures from multiple ocean localities and show that the high-latitude temperature decrease was substantial and heterogeneous. High-latitude (45 degrees to 70 degrees in both hemispheres) temperatures before the climate transition were approximately 20 degrees C and cooled an average of approximately 5 degrees C. Our results, combined with ocean and ice-sheet model simulations and benthic oxygen isotope records, indicate that Northern Hemisphere glaciation was not required to accommodate the magnitude of continental ice growth during this time.
大约3400万年前，地球气候从一个相对无冰的世界转变为南极洲出现冰川状况且有大量冰盖的世界。在这次气候转变期间地球温度如何变化仍知之甚少，而且北半球极地冰的证据存在争议。在此，我们报告了来自多个海洋地点的海面温度代理记录，并表明高纬度地区的温度下降幅度很大且不均匀。气候转变前的高纬度地区（南北半球均为45度至70度）温度约为20摄氏度，平均降温约5摄氏度。我们的结果，结合海洋和冰盖模型模拟以及底栖氧同位素记录，表明这段时间内大陆冰增长的规模并不需要北半球出现冰川作用。
