Institute of Geological Sciences, University of Bern, Bern, Switzerland.
Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland.
Nature. 2016 Feb 11;530(7589):207-10. doi: 10.1038/nature16514. Epub 2016 Feb 3.
No single mechanism can account for the full amplitude of past atmospheric carbon dioxide (CO2) concentration variability over glacial-interglacial cycles. A build-up of carbon in the deep ocean has been shown to have occurred during the Last Glacial Maximum. However, the mechanisms responsible for the release of the deeply sequestered carbon to the atmosphere at deglaciation, and the relative importance of deep ocean sequestration in regulating millennial-timescale variations in atmospheric CO2 concentration before the Last Glacial Maximum, have remained unclear. Here we present sedimentary redox-sensitive trace-metal records from the Antarctic Zone of the Southern Ocean that provide a reconstruction of transient changes in deep ocean oxygenation and, by inference, respired carbon storage throughout the last glacial cycle. Our data suggest that respired carbon was removed from the abyssal Southern Ocean during the Northern Hemisphere cold phases of the deglaciation, when atmospheric CO2 concentration increased rapidly, reflecting--at least in part--a combination of dwindling iron fertilization by dust and enhanced deep ocean ventilation. Furthermore, our records show that the observed covariation between atmospheric CO2 concentration and abyssal Southern Ocean oxygenation was maintained throughout most of the past 80,000 years. This suggests that on millennial timescales deep ocean circulation and iron fertilization in the Southern Ocean played a consistent role in modifying atmospheric CO2 concentration.
没有单一的机制可以解释过去冰川间冰期大气二氧化碳 (CO2) 浓度变化的全部幅度。已经表明，在末次冰期最大值期间，海洋深处的碳积累已经发生。然而，负责在冰川消退时将深层封存的碳释放到大气中，以及深层海洋封存对末次冰期最大值之前调节大气 CO2 浓度千年尺度变化的相对重要性，仍然不清楚。在这里，我们展示了来自南大洋南极区的沉积氧化还原敏感痕量金属记录，这些记录提供了对深海氧气化瞬时变化的重建，并且可以推断出整个末次冰期循环中呼吸碳的储存情况。我们的数据表明，在冰川消退的北半球寒冷阶段，呼吸碳从深海南大洋中被去除，当时大气 CO2 浓度迅速增加，这至少部分反映了尘埃铁施肥减少和深海通风增强的综合作用。此外，我们的记录还表明，在过去的 8 万年中，大气 CO2 浓度与深海南大洋氧气化之间的观测到的相关性一直保持不变。这表明，在千年时间尺度上，南大洋的深层海洋环流和铁施肥在调节大气 CO2 浓度方面发挥了一致的作用。
