All else equal, if the ocean's “biological [carbon] pump” strengthens, the dissolved oxygen (O₂) content of the ocean interior declines. Confidence is now high that the ocean interior as a whole contained less oxygen during the ice ages. This is strong evidence that the ocean's biological pump stored more carbon in the ocean interior during the ice ages, providing the core of an explanation for the lower atmospheric carbon dioxide (CO₂) concentrations of the ice ages. Vollmer et al. (2022, https://doi.org/10.1029/2021PA004339) combine proxies for the oxygen and nutrient content of bottom waters to show that the ocean nutrient reservoir was more completely harnessed by the biological pump during the Last Glacial Maximum, with an increase in the proportion of dissolved nutrients in the ocean interior that were “regenerated” (transported as sinking organic matter from the ocean surface to the interior) rather than “preformed” (transported to the interior as dissolved nutrients by ocean circulation). This points to changes in the Southern Ocean, the dominant source of preformed nutrients in the modern ocean, with an apparent additional contribution from a decline in the preformed nutrient content of North Atlantic-formed interior water. Vollmer et al. also find a lack of LGM-to-Holocene difference in the preformed ¹³C/¹²C ratio of dissolved inorganic carbon. This finding may allow future studies to resolve which of the proposed Southern Ocean mechanisms was most responsible for enhanced ocean CO₂ storage during the ice ages: (a) coupled changes in ocean circulation and biological productivity, or (b) physical limitations on air-sea gas exchange.

中文翻译：

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海洋氧气、预先形成的营养物以及末次盛冰期大气中二氧化碳浓度较低的原因

在其他条件相同的情况下，如果海洋的“生物[碳]泵”增强，海洋内部的溶解氧(O _{2 )含量就会下降。}现在人们非常有信心地认为，在冰河时期，整个海洋内部的氧气含量较低。这是强有力的证据，表明海洋生物泵在冰河时期在海洋内部储存了更多的碳，为冰河时期大气二氧化碳（CO _{2 ）浓度较低的解释提供了核心。}沃尔默等人。（2022 年，https://doi.org/10.1029/2021PA004339）结合了底层水域的氧气和营养物含量的代理，表明在末次盛冰期，海洋营养物库被生物泵更完全地利用，增加了海洋内部溶解的营养物质“再生”（作为下沉的有机物质从海洋表面输送到内部）而不是“预形成”（作为溶解的营养物质通过海洋环流输送到内部）的比例。这表明南大洋发生了变化，南大洋是现代海洋中预制营养物的主要来源，而北大西洋形成的内水预制营养物含量的下降显然也起到了额外的作用。沃尔默等人。^{还发现溶解无机碳的预形成13} C/ ¹² C 比率缺乏末次盛世与全新世之间的差异。这一发现可能使未来的研究能够解决所提出的南大洋机制中哪种机制对冰河时期海洋 CO ₂储存量的增加负有最大责任：（a）海洋环流和生物生产力的耦合变化，或（b）对空气的物理限制海气交换。