| Summary: | Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography and Paleoclimatology 36(9), (2021): e2021PA004226, https://doi.org/10.1029/2021PA004226. The deep ocean has long been recognized as the reservoir that stores the carbon dioxide (CO2) removed from the atmosphere during Pleistocene glacial periods. The removal of glacial atmospheric CO2 into the ocean is likely modulated by an increase in the degree of utilization of macronutrients at the sea surface and enhanced storage of respired CO2 in the deep ocean, known as enhanced efficiency of the biological pump. Enhanced biological pump efficiency during glacial periods is most easily documented in the deep ocean using proxies for oxygen concentrations, which are directly linked to respiratory CO2 levels. We document the enhanced storage of respired CO2 during the Last Glacial Maximum (LGM) in the Pacific Southern Ocean and deepest Equatorial Pacific using records of deglacial authigenic manganese, which form as relict peaks during increases in bottom water oxygen (BWO) concentration. These peaks are found at depths and regions where other oxygenation histories have been ambiguous, due to diagenetic alteration of authigenic uranium, another proxy for BWO. Our results require that the entirety of the abyssal Pacific below approximately 1,000 m was enriched in respired CO2 and depleted in oxygen during the LGM. The presence of authigenic Mn enrichment in the deep Equatorial Pacific for each of the last five deglaciations suggests that the storage of respired CO2 in the deep ocean is a ubiquitous feature of late-Pleistocene ice ages. This work was performed with support from the National Science Foundation (NSF) over about 30 years. The TT013 and NBP9802 cores were collected during the U.S. JGOFS program. Their collection and analyses were supported by NSF OCE-9022301 and OPP-95303398 to R. F. ...
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