Luo Yiming, Tjiputra Jerry, Guo Chuncheng, Zhang Zhongshi, Lippold Jörg
Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Allegaten 70, 5007, Bergen, Norway.
Uni Research Climate, and Bjerknes Centre for Climate Research, Jahnebakken 5, 5007, Bergen, Norway.
Sci Rep. 2018 Mar 13;8(1):4401. doi: 10.1038/s41598-018-22534-z.
Understanding how the Atlantic Meridional Overturning Circulation (AMOC) evolved during crucial past geological periods is important in order to decipher the interplay between ocean dynamics and global climate change. Previous research, based on geological proxies, has provided invaluable insights into past AMOC changes. However, the causes of the changes in water mass distributions in the Atlantic during different periods remain mostly elusive. Using a state-of-the-art Earth system model, we show that the bulk of NCW in the deep South Atlantic Ocean below 4000 m migrated from the western basins at 125 ka to the eastern basins at 115 ka, though the AMOC strength is only slightly reduced. These changes are consistent with proxy records, and it is mainly due to more penetration of the AABW at depth at 115 ka, as a result of a larger density of AABW formed at 115 ka. Our results show that depth changes in regional deep water pathways can result in large local changes, while the overall AMOC structure hardly changes. Future research should thus be careful when interpreting single proxy records in terms of large-scale AMOC changes, and considering variability of water-mass distributions on sub-basin scale would give more comprehensive interpretations of sediment records.
了解大西洋经向翻转环流（AMOC）在过去关键地质时期的演变情况，对于解读海洋动力学与全球气候变化之间的相互作用至关重要。以往基于地质指标的研究，为过去AMOC的变化提供了宝贵见解。然而，不同时期大西洋水体分布变化的原因仍大多不明。利用一个最先进的地球系统模型，我们发现，在4000米以下的南大西洋深层，大部分北大西洋深层水（NCW）在125 ka时从西部海盆迁移至115 ka时的东部海盆，尽管AMOC强度仅略有降低。这些变化与指标记录一致，主要是由于115 ka时南极底层水（AABW）在深度上的更多侵入，这是115 ka时形成的AABW密度更大的结果。我们的结果表明，区域深层水路径的深度变化可导致局部的大幅变化，而AMOC的整体结构几乎不变。因此，未来研究在根据大规模AMOC变化解读单个指标记录时应谨慎，考虑次海盆尺度上水体分布的变异性将能对沉积记录给出更全面的解释。
