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| Has the Drake Passage Played an Essential Role in the Cenozoic Cooling? |
| ZHANG Zhong-Shi,YAN Qing,WANG Hui-Jun |
| Bjerknes Centre for Climate Research, UniResearch, Bergen N-5007, Norway;Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China,Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China,Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China |
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Abstract The Drake Passage is the seaway between South America and Antarctica. It is widely believed that the thermal isolation effects caused by the opening of the Drake Passage played an important role in the abrupt cooling that occurred at the Eocene-Oligocene boundary in the Cenozoic. These effects are also thought to be independent of the geometry of the passage. Here, the authors demonstrate that the climate impacts of the Drake Passage depend on the passage geometry by comparing the climate’s sensitivity to the opening of the Drake Passage under the present and the Early Eocene land-sea configurations. These experiments show that the thermal isolation effects caused by the passage are much stronger under the present land-sea configuration. In comparison, under the Early Eocene land-sea configuration, the weak anomalies in heat transport caused by the opening of the narrow and shallow Drake Passage are not strong enough to thermally insulate Antarctica. The climate effects of the Drake Passage on the Cenozoic cooling have been overestimated in previous sensitivity studies carried out using the present land-sea configuration. Thus, it is unlikely that the opening of the Drake Passage played an essential role in the abrupt Cenozoic cooling, especially in the abrupt cooling at the Eocene-Oligocene boundary.
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Received: 29 August 2010
Revised: 12 September 2010
Accepted: 12 September 2010
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