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每日翻译20190620

已有 325 次阅读 2019-6-20 07:10 |个人分类:翻译作品|系统分类:科研笔记| 冰期, 更新世, 间冰期

#编者信息

熊荣川

明湖实验室

xiongrongchuan@126.com

http://blog.sciencenet.cn/u/Bearjazz

THE ICE AGES

Studies of the last 20 years have   produced great advances in our understanding of the palaeoclimate, and this   continues apace from new data and theories regularly making headlines.   Information is gathered from levels of oxygen and carbon isotopes, magnetic   and CO, measures, animal, vegetable and mineral remains in cores from the   seabed, land and ice, and this is providing evermore coherent descriptions   and explanations. It is clear that the last 700000 years have been dominated   by major ice ages with a roughly 100kyr cycle interrupted by relatively short   warm interglacials such as we enjoy at present. The Milankovitch theory proposes   that the pacemaker of this process is the orbital eccentricity of the earth around   the sun (Hays, Imbrie & Shackleton, 1976;Gribbin, 1989). This causes major   changes in insolation and along with lesser variations in axial tilt   (40000yr) and precession (23000yr) produces a complex of climatic oscillations.   Going back further in the Pleistoceneand into the Pliocene several long   records indicate that the ice ages were less intense prior to 700ky and that   the ice sheets in the northern hemisphere began to grow large around 2.4Myr   (Webb & Bartlein, 1992). Thus while the orbital cycles go back beyond   3Myr, other factors such as tectonic movement and ocean currents must be modifymg   their effects over longer periods. Furthermore, while the ice ages have become   an increasingly dramatic feature of the Pleistocene, large oscillations in   climate producing large changes in flora and fauna can be clearly traced back   into the Tertiary.

 

冰河时代

过去20年的研究在我们对古气候的理解上取得了巨大的进展,经常上头条的新数据和新理论不断让我们深化了该领域的认识。信息是从海底、陆地和冰的氧碳同位素、磁性、一氧化碳和地质测量,以及动物、植物和矿物残留物等得来,这提供了更加连贯的描述和解释。很明显,过去70万年中主要是冰期占主导地位,中间被大约10万年温暖的间冰期隔开,如当前我们乐在其中这段时期。米兰科维奇理论认为,这个过程的起搏器是地球围绕太阳的轨道偏心率(Hays, Imbrie & Shackleton, 1976;Gribbin, 1989)。这主要导致了日晒的变化,伴随轴倾(40000年)和旋进(23000年)的较小变化,从而产生了复杂的气候波动。回到过去在更新世和上新世,一些长期的记录表明,70万年之前,冰期就不那么强烈,北半球的冰盖是在240万年前左右开始变大的(Webb & Bartlein, 1992)。因此,当轨道周期超过300万年时,其他因素,如构造运动和洋流必定在较长时间内调整其影响。此外,虽然冰期已成为更新世一个日益引人注目的特征,但导致动植物的大变化的气候大振荡,可以清楚地追溯到第三纪。

Hewitt G M . Some genetic consequences of   ice ages, and their role in divergence and speciation[J]. Biological Journal   of the Linnean Society, 2010, 58(3):247-276.




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