Geological Institute, Department of Earth Sciences, ETH Zürich, Zürich, Switzerland.
Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland.
Science. 2019 Mar 8;363(6431):1080-1084. doi: 10.1126/science.aat7067.
From 1.25 million to 700,000 years ago, the ice age cycle deepened and lengthened from 41,000- to 100,000-year periodicity, a transition that remains unexplained. Using surface- and bottom-dwelling foraminifera from the Antarctic Zone of the Southern Ocean to reconstruct the deep-to-surface supply of water during the ice ages of the past 1.5 million years, we found that a reduction in deep water supply and a concomitant freshening of the surface ocean coincided with the emergence of the high-amplitude 100,000-year glacial cycle. We propose that this slowing of deep-to-surface circulation (i.e., a longer residence time for Antarctic surface waters) prolonged ice ages by allowing the Antarctic halocline to strengthen, which increased the resistance of the Antarctic upper water column to orbitally paced drivers of carbon dioxide release.
从 125 万年前到 70 万年前，冰河时代的周期从 41000 年到 100000 年的周期性加深和延长，这种转变仍然无法解释。利用来自南大洋南极带的表层和底层有孔虫来重建过去 150 万年冰期期间深至表层的水供应情况，我们发现，深水源供应的减少和表层海洋的相应淡化与高振幅 10 万年冰川周期的出现同时发生。我们提出，这种深至表层循环的减缓（即南极表层水的停留时间延长）通过允许南极盐度跃层加强，从而增加了南极上层水柱对轨道驱动的二氧化碳释放的阻力，从而延长了冰期。
