The North Pacific oxygen uptake rates over the past half century

Eun Young Kwon, Curtis Deutsch, Shang Ping Xie, Sunke Schmidtko, Yang Ki Cho

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The transport of dissolved oxygen (O2) from the surface ocean into the interior is a critical process sustaining aerobic life in mesopelagic ecosystems, but its rates and sensitivity to climate variations are poorly understood. Using a circulation model constrained to historical variability by assimilation of observations, the study shows that the North Pacific thermocline effectively takes up O2 primarily by expanding the area through which O2-rich mixed layer water is detrained into the thermocline. The outcrop area during the critical winter season varies in concert with the Pacific decadal oscillation (PDO). When the central North Pacific Ocean is in a cold phase, the winter outcrop window for the central mode water class (CMW; a neutral density range of γ = 25.6-26.6) expands southward, allowing more O2-rich surface water to enter the ocean's interior. An increase in volume flux of water to the CMW density class is partly compensated by a reduced supply to the shallower densities of subtropical mode water (γ = 24.0-25.5). The thermocline has become better oxygenated since the 1980s partly because of strong O2 uptake. Positive O2 anomalies appear first near the outcrop and subsequently downstream in the subtropical gyre. In contrast to the O2 variations within the ventilated thermocline, observed O2 in intermediate water (density range of γ =26.7-27.2) shows a declining trend over the past half century, a trend not explained by the open ocean water mass formation rate.

Original languageEnglish (US)
Pages (from-to)61-76
Number of pages16
JournalJournal of Climate
Volume29
Issue number1
DOIs
StatePublished - 2016
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Keywords

  • Atm/Ocean Structure/Phenomena
  • Circulation/Dynamics
  • Climate variability
  • Ocean circulation
  • Ocean dynamics
  • Pacific decadal oscillation
  • Seasonal cycle
  • Thermocline circulation
  • Variability

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