Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age

Xingchen T. Wang, Daniel M. Sigman, Maria Prokopenko, Jess F. Adkins, Laura Robinson, Sophia K Hines, Junyi Chai, alfredo Martinez Garcia, Tianyu Chen, Gerald H. Haug

Research output: Contribution to journalArticle (Academic Journal)peer-review

22 Citations (Scopus)
365 Downloads (Pure)

Abstract

The Southern Ocean regulates the ocean’s biological sequestration of CO2 and is widely suspected to underlie much of the ice age decline in atmospheric CO2 concentration, but the specific changes in the region are debated. While more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the 15N/14N of fossil-bound organic matter in the stony deep-sea coral Desmophyllum dianthus, a new tool for reconstructing surface ocean nutrient conditions. The central robust observation is of higher 15N/14N across the Southern Ocean during the Last Glacial Maximum (LGM), 18-25,000 years ago. These data suggest a reduced summer surface nitrate concentration in both the Antarctic and Subantarctic Zones during the LGM, with little surface nitrate transport between them. After the ice age, the increase in Antarctic surface nitrate occurred through the deglaciation and continued in the Holocene. The rise in Subantarctic surface nitrate appears to have had both early deglacial and late deglacial/Holocene components, preliminarily attributed to the end of Subantarctic iron fertilization and increasing nitrate input from the Antarctic, respectively.
Original languageEnglish
Pages (from-to)3352–3357
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number13
Early online date15 Mar 2017
DOIs
Publication statusPublished - 28 Mar 2017

Keywords

  • Southern Ocean
  • nutrient consumption
  • atmospheric CO2
  • ice ages

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