Southwest Pacific Ocean surface reservoir ages since the last glaciation: Circulation insights from multiple-core studies

Elisabeth L. Sikes, Thomas P. Guilderson

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Radiocarbon (14C) in dissolved inorganic carbon in the ocean can trace the age of ocean water relative to the atmosphere and provide insight into climate-driven changes in ocean circulation since the last glaciation. Here we estimate surface radiocarbon ages from the last glaciation through the deglaciation into the Holocene in the southwestern Pacific by using tephras, both as stratigraphic tie points and for the availability of existing radiocarbon dates from terrestrial- based analyses of the organic carbon associated with them, as markers of past atmospheric Δ14C. The glacial surface reservoir age of subtropical waters was ~700 14C years older than the coeval atmosphere at ~25,000 cal yr B.P. This was significantly older (more 14C depleted) by ~ 300 14C years, than modern reservoir ages. At the same time, subantarctic surface water reservoir age was ~3200 14C years, almost 5 times the modern reservoir age, making the difference in age between subtropical and subantarctic surface water masses treble the modern difference. This pattern is attributed to the upwelling and exchange of very old deep waters from the glacial abyss in the Southern Ocean. In the early deglaciation, surface reservoir ages were ~600 to 700 14C years. Recent atmospheric Δ14C calibrations project that these surface reservoir ages were older than modern by 1.2-fold to 2-fold. This increased reservoir effect can be attributed to shallow circulation that differed from modern, delivering waters with lower 14C content to the region. Early Holocene surface reservoir ages of ~300 to 500 14C years, similar to recent, suggest modern circulation patterns were in place by that time.

Original languageEnglish (US)
Pages (from-to)298-310
Number of pages13
JournalPaleoceanography
Volume31
Issue number2
DOIs
StatePublished - Feb 1 2016

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Palaeontology

Keywords

  • Pacific Ocean circulation
  • Southern Ocean
  • climate change
  • last glaciation
  • radiocarbon
  • reservoir age

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