Ocean Oxygen, Preformed Nutrients, and the Cause of the Lower Carbon Dioxide Concentration in the Atmosphere of the Last Glacial Maximum

Daniel M. Sigman, Mathis P. Hain

Research output: Contribution to journalComment/debatepeer-review

Abstract

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.

Original languageEnglish (US)
Article numbere2023PA004775
JournalPaleoceanography and Paleoclimatology
Volume39
Issue number1
DOIs
StatePublished - Jan 2024

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Atmospheric Science
  • Palaeontology

Keywords

  • biological pump
  • carbon dioxide
  • ice age
  • nutrient
  • oxygen
  • Southern Ocean

Fingerprint

Dive into the research topics of 'Ocean Oxygen, Preformed Nutrients, and the Cause of the Lower Carbon Dioxide Concentration in the Atmosphere of the Last Glacial Maximum'. Together they form a unique fingerprint.

Cite this