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每日翻译20190621

已有 237 次阅读 2019-6-21 07:23 |个人分类:翻译作品|系统分类:科研笔记| 冰期, 间冰期, 气候波动, 冰川

#编者信息

熊荣川

明湖实验室

xiongrongchuan@126.com

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

Our knowledge and understanding are best   for the last glacial cycle (- 135kyr) and particularly for the progression   from the full ice age conditions of 20 000BP to the warm interglacial of the   present (e.g. Coope, 1977; Huntley & Birks, 1983; COHMAP members, 1988;   Huntley & Webb, 1988; Bartlein & Prentice, 1989; Webb & Bartlein,   1992).The warm Eemian interglacial (135-115 kyr) gave way to colder   conditions with more and more water becoming locked up in icesheets until the   onset of the present interglacial some 18000BP. The lesser orbital cycles continued   and there were significant climatic fluctuations during this period. Recent results   from deep ice cores in Greenland revealed dramatic switches in temperature above   the ice sheet during the ice age, and even more surprisingly during the   Eemian interglacial (GRIP Project Members, 1993; Dansgaard et al., 1993). It   would seem that average temperatures would change by 10-12°C in 5-10 years   and last for periods of 70-5000 years; this was very different from the   fairly constant conditions during the last 8000 years of the present   interglacial. The European pollen record also indicates that there were   marked changes in vegetation at various sites during the last interglacial   period, which suggests extensive oscillations in climate over a wide area at   this time (Tzedakiset aL, 1994). Following the Eemian interglacial there is   growing evidence for periodic iceberg discharge into the Atlantic every   15-7kyr during the last iceage, possibly caused by a cycle of build up of ice   and collapse into the sea; the so called Bond cycles and Heinrich events   (Bond et al., 1993; Lehman, 1993). It is further postulated that such   discharges would seriously effect the ocean conveyer circulation of cold   water from the North Atlantic and warm water from the Pacific. These events   caused large changes in climate which seem to have had effects around the   globe; the reports of changes in vegetation in Florida coincident with the later   Heinrich events are particularly significant (Grimm et al., 1993).

 

我们了解较多的是最近一个冰期(135000年),尤其是从距今(BPBefore Present20000年前的完全冰期条件发展到目前温暖的间冰期条件这段时间(见 Coope, 1977; Huntley & Birks, 1983; COHMAP membe rs, 1988;   Huntley & Webb, 1988; Bartlein & Prentice, 1989; Webb & Bartlein,   1992)。温暖的艾木间冰期(135000-115000年前)被更冷的条件所取代,越来越多的水被冰盖锁住,直到大约18000年前到现在的间冰期开始。较小的轨道周期继续存在,在此期间有明显的气候波动。格陵兰岛深层冰芯的最新研究结果显示,冰河时期,冰盖上方的温度发生了剧烈的变化,而在艾木间冰期,变化更惊人(GRIP Project Members, 1993; Dansgaard et al., 1993)。似乎平均温度在5-10年内会变化10-12°C,并持续70-5000年。这与目前最近8000年间冰期中相当稳定的条件非常不同。欧洲花粉记录还表明,在上一次间冰期,许多地点的植被发生了显著的变化,这表明在这一时期,许多地区都发生了剧烈的气候振荡(Tzedakiset aL, 1994)。继艾木间冰期之后,越来越多的证据表明,上次冰期,每隔15000-17000年,就有一次阶段性冰川移入大西洋。这可能是由于冰山的形成和崩落到海中的周期引起的;即所谓的Bond周期和Heinrich事件(Bond et al.,   1993; Lehman, 1993)。进一步推断,这种排放将严重影响北大西洋冷水和来自北太平洋的温水的海洋输送循环。这些事件导致了气候的巨大变化,似乎对全球都产生了影响;据报告,佛罗里达州的植被变化与海因里希事件一致性就很显著(Grimm et al., 1993)。

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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