巴拿马海道关闭及其古海洋和古气候影响

CLOSURE OF THE PANAMA SEAWAY AND ITS PALEOCEANOGRAPHIC AND PALEOCLIMATIC EFFECTS

位于中美洲的巴拿马海道曾是连通赤道东太平洋和大西洋的开放洋流通道。从中新世开始,巴拿马海道在构造运动的驱动下逐步关闭,切断了赤道太平洋和大西洋海水的直接交流。海道的关闭不仅改变了太平洋和大西洋海水的物理性质和洋流模式,还可能对新生代中晚期气候变化,特别是北半球大冰期的开始有重要作用。简要综述了二十余年来围绕巴拿马海道关闭及其古海洋、古气候意义方面的研究成果和最新研究进展。很多相关的问题目前仍处于激烈的争论之中或尚未得到充分的认识,亟待开展进一步工作。开展相关研究将对促进我国古海洋和古气候研究具有积极意义,并有助于进一步加深我们对于海洋-气候系统的认识。

Panama Seaway located at Central American region was once an important seaway connecting the equatorial Pacific and Atlantic. Its gradual closure caused by tectonic movements from the middle Miocene to Pliocene has been thought to significantly influence the ocean and climate. On one hand, its closure pro- gressively cut off direct seawater exchange between the equatorial Pacific and Caribbean Sea. Disruption of tropical seawater connection between the Pacific and Atlantic through the seaway led to significant diver- gence in physical properties of seawater, such as salinity and nutrients, as well as large reorganization of circulation patterns in these two ocean basins. On the other hand, reorganization of circulation induced by the closure probably played an important role in climate change in the late Cenozoic, especially in initiating Northern Hemisphere Glaciation through a set of feedbacks which are still under exploring. This paper briefly summarized research progress in the past few decades on closure process of the Panama Seaway and its impacts on the ocean and climate. Some relevant problems which remain controversial and need more studies are also discussed in the paper.