Increased storage of carbon in the oceans has been proposed as a mechanism to explain lower concentrations of atmospheric carbon dioxide during ice ages; however, unequivocal signatures of this storage have not been found1. In seawater, the dissolved gases oxygen and carbon dioxide are linked via the production and decay of organic material, with reconstructions of low oxygen concentrations in the past indicating an increase in biologically mediated carbon storage. Marine sediment proxy records have suggested that oxygen concentrations in the deep ocean were indeed lower during the last ice age, but that near-surface and intermediate waters of the Pacific Ocean—a large fraction of which are poorly oxygenated at present—were generally better oxygenated during the glacial1–3. This vertical opposition could suggest a minimal net basin-integrated change in carbon storage. Here we apply a dual-proxy approach, incorporating qualitative upper-water-column and quantitative bottom-water oxygen reconstructions4,5, to constrain changes in the vertical extent of low-oxygen waters in the eastern tropical Pacific since the last ice age. Our tandem proxy reconstructions provide evidence of a downward expansion of oxygen depletion in the eastern Pacific during the last glacial, with no indication of greater oxygenation in the upper reaches of the water column. We extrapolate our quantitative deep-water oxygen reconstructions to show that the respired carbon reservoir of the glacial Pacific was substantially increased, establishing it as an important component of the coupled mechanism that led to low levels of atmospheric carbon dioxide during the glacial.A downward expansion of oxygen depletion in the eastern Pacific Ocean during the last ice age suggests an increase in the respired carbon reservoir, contributing to the lower levels of atmospheric carbon dioxide during this period.

中文翻译：

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热带太平洋东部缺氧海水的冰川扩张

人们提出增加海洋中碳的储存量是解释冰河时代大气二氧化碳浓度降低的一种机制；但是，尚未发现此存储的明确签名1。在海水中，溶解气体氧气和二氧化碳通过有机物质的产生和衰变联系在一起，过去低氧浓度的重建表明生物介导的碳储存增加。海洋沉积物代用记录表明，在上一个冰河时代，深海中的氧气浓度确实较低，但太平洋的近表层和中层水域——目前其中很大一部分含氧量较差——通常含氧量较好在冰期1-3。这种垂直对立可能表明碳储存的净盆地综合变化最小。在这里，我们应用双代理方法，结合定性的上水柱和定量的底水氧重建 4,5，来限制自上次冰河时代以来热带太平洋东部低氧水域垂直范围的变化。我们的串联代理重建提供了在末次冰期期间东太平洋氧气消耗量向下扩展的证据，但没有迹象表明水体上游有更大的氧化作用。我们推断出我们的定量深水氧重建，以表明冰川太平洋的呼吸碳库显着增加，