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Migration of the subtropical front as a modulator of glacial climate

机译：亚热带锋面的迁移是冰川气候的调节器

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摘要

Ice cores extracted from the Antarctic ice sheet suggest that glacial conditions, and the relationship between isotopically derived temperatures and atmospheric P_(CO_2) have been constant over the last 800,000 years of the Late Pleistocene epoch. But independent lines of evidence, such as the extent of Northern Hemisphere ice sheets, sea level and other temperature records, point towards a fluctuating severity of glacial periods, particularly during the more extreme glacial stadials centred around 340,000 and 420,000 years ago (marine isotope stages 10 and 12). Previously unidentified mechanisms therefore appear to have mediated the relationship between insolation, CO_2 and climate. Here we test whether northward migration of the subtropical front (STF) off the southeastern coast of South Africa acts as a gatekeeper for the Agulhas current, which controls the transport of heat and salt from the Indo-Pacific Ocean to the Atlantic Ocean. Using a new 800,000-year record of sea surface temperature and ocean productivity from ocean sediment core MD962077, we demonstrate that during cold stadials (particularly marine isotope stages 10 and 12), productivity peaked and sea surface temperature was up to 6 ℃ cooler than modern temperatures. This suggests that during these cooler stadials, the STF moved northward by up to 7° latitude, nearly shutting off the Agulhas current. Our results, combined with faunal assemblages from the south Atlantic show that variable northwards migration of the Southern Hemisphere STF can modulate the severity of each glacial period by altering the strength of the Agulhas current carrying heat and salt to the Atlantic meridional overturning circulation. We show hence that the degree of northwards migration of the STF can partially decouple global climate from atmospheric partial pressure of carbon dioxide, P_(CO_2), and help to resolve the long-standing puzzle of differing glacial amplitudes within a consistent range of atmospheric P(CO_2).
机译：从南极冰盖提取的冰芯表明，在晚更新世末期的最后80万年中，冰川条件以及同位素衍生温度与大气P_（CO_2）之间的关系一直保持不变。但是独立的证据线，例如北半球冰盖的范围，海平面和其他温度记录，表明冰川时期的严重性在波动，特别是在距今约340,000和420,000年前的更极端的冰川静止期（海洋同位素阶段） 10和12）。因此，以前未知的机制似乎介导了日照，CO_2和气候之间的关系。在这里，我们测试了南非东南沿海副热带锋面（STF）的向北迁移是否是Agulhas流的守门人，Agulhas流控制着热量和盐分从印度太平洋向大西洋的运输。利用来自海洋沉积物核心MD962077的80万年的新海面温度和海洋生产力记录，我们证明了在寒冷的恒星期（尤其是海洋同位素第10和12期）中，生产力达到顶峰，海面温度比现代温度低6℃。温度。这表明在这些较凉的季节中，STF向北移动了高达7°的纬度，几乎关闭了Agulhas的水流。我们的结果，再加上来自南大西洋的动物群组合，表明南半球STF向北的可变迁移可以通过改变载有热量和盐分的Agulhas流向大西洋子午翻转循环的强度来调节每个冰川期的严重程度。因此，我们表明，STF向北迁移的程度可以使全球气候与二氧化碳的大气分压P_（CO_2）部分脱钩，并有助于解决在恒定的大气P范围内长期存在的不同冰川振幅的难题。 （CO_2）。

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  • 来源
    《Nature》 |2009年第7253期|380-383qt03|共5页
  • 作者

    Edouard Bard; Rosalind E. M. Rickaby;

  • 作者单位

    CEREGE (UMR 6635), College de France, University Paul-Cezanne Aix-Marseille, CNRS, IRD, Europole de I'Arbois BP 80,13545 Aix-en-Provence Cedex 4, France;

    Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, UK;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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