During the last glacial interval, marine sediments recorded reduced current ventilation within the ocean interior below water depths of approximately >1,500 m [B. A. Hoogakker et al., Nat. Geosci. 8, 40–43 (2015)]. The degree of the associated oxygen depletion in the different ocean basins, however, is still poorly constrained. Here, we present sedimentary records of redox-sensitive metals from the southwest African margin. These records show evidence of continuous bottom water anoxia in the eastern South Atlantic during the last glaciation that led to enhanced carbon burial over a prolonged period of time. Our geochemical data indicate that upwelling-related productivity and the associated oxygen minimum zone in the eastern South Atlantic shifted far seaward during the last glacial period and only slowly retreated during deglaciation times. While increased productivity during the last ice age may have contributed to oxygen depletion in bottom waters, especially on the upper slope, slow-down of the Late Quaternary deep water circulation pattern [Rutberg et al., Nature 405, 935–938 (2000)] appears to be the ultimate driver of anoxic conditions in deep waters.

在末次冰期期间，海洋沉积物记录到水深约 >1,500 m 以下海洋内部的当前通风减少 [BA Hoogakker et al., Nat. 地理科学。8, 40–43 (2015)]。然而，不同海洋盆地中相关的氧气消耗程度仍然受到很大限制。在这里，我们展示了来自西南非洲边缘的氧化还原敏感金属的沉积记录。这些记录显示了在最后一次冰期期间南大西洋东部持续的底水缺氧的证据，这导致了长时间内碳埋藏的增加。我们的地球化学数据表明，在最后一个冰期，南大西洋东部与上升流相关的生产力和相关的氧气最低区向海移动了很远，并且在冰消期仅缓慢退缩。虽然在最后一个冰河时代生产力的提高可能导致底部水域的氧气消耗，特别是在上坡，Nature 405, 935–938 (2000)] 似乎是深水缺氧条件的最终驱动因素。