Aging and Molecular Changes of Dissolved Organic Matter Between Two Deep Oceanic End-Members

S. K. Bercovici, B. P. Koch, O. J. Lechtenfeld, S. L. McCallister, P. Schmitt-Kopplin, D. A. Hansell

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

The global ocean contains a massive reservoir of dissolved organic carbon (DOC), rivaling the atmosphere's pool of CO2. The most recalcitrant fractions have mean radiocarbon ages of ~4,000 years in the Atlantic to ~6,000 years in the Pacific. Knowing the radiocarbon signatures of DOC and the molecular composition of dissolved organic matter (DOM) is crucial to develop understanding of the persistence and lifetime of the DOC pool. In this research, we collected samples from the deep North Pacific in August 2013 (aboard the RV Melville) to couple the Δ14C content of solid-phase-extracted DOM (Δ14C-SPE-DOM) with its molecular composition in the ocean's oldest deep waters. We find that deep waters in this region held a mean Δ14C-SPE-DOM value of −554 ± 9‰ (~6,400 14C years), substantially more depleted than that in the deep Atlantic, which held a mean Δ14C-SPE-DOM value of −445 ± 5‰. While we find a more degraded molecular composition of DOM in the deep Pacific than the deep Atlantic, the molecular formulae within the Island of Stability (Lechtenfeld et al., 2014, https://doi.org/10.1016/j.gca.2013.11.009), are largely retained. These results imply that a fraction of deep DOM is resistant to removal and present in both the deep Atlantic and Pacific Oceans.

Original languageEnglish (US)
Pages (from-to)1449-1456
Number of pages8
JournalGlobal Biogeochemical Cycles
Volume32
Issue number10
DOIs
StatePublished - Oct 2018

Keywords

  • deep North Pacific
  • dissolved organic matter
  • molecular composition
  • radiocarbon

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Environmental Science(all)
  • Atmospheric Science

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    Bercovici, S. K., Koch, B. P., Lechtenfeld, O. J., McCallister, S. L., Schmitt-Kopplin, P., & Hansell, D. A. (2018). Aging and Molecular Changes of Dissolved Organic Matter Between Two Deep Oceanic End-Members. Global Biogeochemical Cycles, 32(10), 1449-1456. https://doi.org/10.1029/2017GB005854